U.S. patent application number 13/291448 was filed with the patent office on 2012-03-08 for green synthesis of nanometals using plant extracts and use thereof.
This patent application is currently assigned to The U.S.A as represented by the Administrator of the U.S. Environmental Protection Agency. Invention is credited to John B. Collins, George E. Hoag, Mallikarjuna N. Nadagouda, Rajendar S. Varma.
Application Number | 20120055873 13/291448 |
Document ID | / |
Family ID | 40943783 |
Filed Date | 2012-03-08 |
United States Patent
Application |
20120055873 |
Kind Code |
A1 |
Hoag; George E. ; et
al. |
March 8, 2012 |
GREEN SYNTHESIS OF NANOMETALS USING PLANT EXTRACTS AND USE
THEREOF
Abstract
The present invention relates to methods of making and using and
compositions of metal nanoparticles formed by green chemistry
synthetic techniques. For example, the present invention relates to
metal nanoparticles formed with solutions of plant extracts and use
of these metal nanoparticles in removing contaminants from soil and
groundwater and other contaminated sites. In some embodiments, the
invention comprises methods of making and using compositions of
metal nanoparticles formed using green chemistry techniques.
Inventors: |
Hoag; George E.;
(Bloomfield, CT) ; Collins; John B.; (Bloomfield,
CT) ; Varma; Rajendar S.; (Cincinnati, OH) ;
Nadagouda; Mallikarjuna N.; (Cincinnati, OH) |
Assignee: |
The U.S.A as represented by the
Administrator of the U.S. Environmental Protection Agency
Washington
DC
VeruTEK, Inc.
Bloomfield
CT
|
Family ID: |
40943783 |
Appl. No.: |
13/291448 |
Filed: |
November 8, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12667384 |
Apr 13, 2010 |
8057682 |
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PCT/US2009/044402 |
May 18, 2009 |
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13291448 |
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61071785 |
May 16, 2008 |
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Current U.S.
Class: |
210/633 ;
252/178; 252/182.12; 252/186.1; 405/128.75; 420/434; 420/463;
420/469; 420/555; 420/8; 75/351; 75/370; 977/773; 977/840;
977/902 |
Current CPC
Class: |
B22F 9/24 20130101; B82Y
30/00 20130101; B22F 1/0018 20130101 |
Class at
Publication: |
210/633 ; 75/370;
75/351; 420/8; 420/434; 420/463; 420/469; 420/555; 405/128.75;
252/178; 252/186.1; 252/182.12; 977/840; 977/902; 977/773 |
International
Class: |
C22C 38/00 20060101
C22C038/00; C22C 22/00 20060101 C22C022/00; C22C 5/04 20060101
C22C005/04; C22C 9/00 20060101 C22C009/00; B09C 1/08 20060101
B09C001/08; C02F 5/10 20060101 C02F005/10; C02F 1/26 20060101
C02F001/26; B22F 9/16 20060101 B22F009/16; C22C 28/00 20060101
C22C028/00 |
Claims
1. A method for making one or more metal nanoparticles, comprising:
providing a solution comprising a first metal ion; providing a
plant extract that comprises a reducing agent, a polyphenol,
caffeine, and/or a natural solvent or surfactant; and combining the
first metal ion solution and the plant extract to produce metal
nanoparticles; wherein the metal is selected from the group
consisting of iron, manganese, palladium, copper, indium, and
combinations.
2-9. (canceled)
10. The method of claim 1, wherein the providing of the solution
comprising the first metal ion, the providing of the plant extract,
and the combining of the first metal ion solution and the plant
extract to produce metal nanoparticles are conducted at about room
temperature.
11. The method of claim 1, wherein the reducing agent, polyphenol,
caffeine, and/or a natural solvent or surfactant is selected from
the group consisting of tea extract, green tea extract, coffee
extract, lemon balm extract, polyphenolic flavonoid, flavonoid,
flavonol, flavone, flavanone, isoflavone, flavans, flavanol,
anthocyanins, proanthocyanins, carotenoids, catechins, quercetin,
rutin, and combinations.
12. (canceled)
13. The method of claim 1, wherein the plant extract is obtained
from a waste product selected from the group consisting of fruit
juice pulp, fruit juice manufacturing wastewater, fruit juice
manufacturing waste, food processing waste, food processing
byproduct, wine manufacturing waste, beer manufacturing waste, and
forest product processing waste.
14. The method of claim 1, wherein the natural solvent or
surfactant is selected from the group consisting of VeruSOL.TM.-3,
Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus Burst 3
(CB-3), EZ-Mulse, and combinations.
15. The method of claim 1, further comprising: providing a second
solution of a metal ion, and combining the first metal ion
solution, the second metal ion solution and the plant extract to
produce metal nanoparticles comprising first and second metals.
16-21. (canceled)
22. The method of claim 1, wherein the metal ion is an iron
ion.
23. The method of claim 1, wherein the solution comprises ferric
chloride (FeCl.sub.3), ferrous sulfate (FeSO.sub.4), ferric nitrate
(Fe(NO.sub.3).sub.3), Fe(III)-EDTA, Fe(III)-citric acid,
Fe(III)-EDDS, Fe(II)-EDTA, Fe(II)-citric acid, and/or
Fe(II)-EDDS.
24-41. (canceled)
42. The method of claim 1, wherein the first metal ion is present
in a medium to be treated.
43. The method of claim 1, wherein the first metal ion is provided
in a medium to be treated by adding a chelating agent to a soil
and/or water sample to be treated.
44. (canceled)
45. A composition comprising zero valent metal nanoparticles and a
plant extract or component of the plant extract that comprises a
reducing agent, a polyphenol, caffeine, and/or a natural solvent or
surfactant wherein the metal nanoparticles comprise one or more of
iron, manganese, palladium, copper, indium, and combinations.
46. The composition of claim 45, wherein the metal nanoparticles
are coated with a substance derived from the plant extract.
47-50. (canceled)
51. The composition of claim 45, wherein the metal nanoparticles
are substantially non-aggregated.
52. The composition of claim 45, comprising a natural solvent or
surfactant.
53. The composition of claim 52, wherein the natural solvent or
surfactant is selected from the group consisting of VeruSOL.TM.-3,
Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus Burst 3
(CB-3), EZ-Mulse and combinations.
54. The composition of claim 45, further comprising a chelating
agent.
55. (canceled)
56. The composition of claim 45, further comprising an oxidant.
57. (canceled)
58. The composition of claim 45, further comprising a carboxy
methyl cellulose coating or a hydrophobic coating on the surface of
the nanoparticles.
59. (canceled)
60. The composition of claim 45, wherein the metal nanoparticles
comprise zero valent metal and a component of the plant
extract.
61. (canceled)
62. The composition of claim 45, wherein the metal nanoparticles
comprise at least two different metals.
63-88. (canceled)
89. The composition of claim 45, wherein the metal nanoparticles
are coated with a phenolic compound of the plant extract.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to methods of making and using
and compositions of metal nanoparticles formed by green chemistry
synthetic techniques. For example, the present invention relates to
metal nanoparticles formed with solutions of plant extracts and use
of these metal nanoparticles in removing contaminants from soil and
groundwater.
[0002] Certain aspects of this invention were made with the support
of the Government of the United States of America, and the
Government may have certain rights in the invention.
BACKGROUND
[0003] Nanoparticles are particles ranging in size from 1 nm to 1
micron in diameter. "Nano" is a prefix which means one billionth
(10.sup.-9) part of something (Meridian Webster Dictionary). In
recent years, the field of nanoparticles has grown due to their
unique properties. Many industries utilize nanoparticles, for
example the electronics industry, medical science, material
science, and environmental science. Noble metal nanoparticles have
found widespread use in several technological applications and
various wet chemical methods have been reported. See, X. Wang and
Y. Li, Chem. Commun., 2007, 2901; Y. Sun and Y. Xia, Science, 2002,
298, 2176; J. Chen, J. M. McLellan, A. Siekkinen, Y. Xiong, Z-Y Li
and Y. Xia, J. Am. Chem. Soc., 2006, 128, 14776; J. W. Stone, P. N.
Sisco, E. C. Goldsmith, S. C. Baxter and C. J. Murphy, Nano Lett.,
2007, 7, 116; B. Wiley, Y. Sun and Y. Xia, Acc. Chem. Res., 2007,
40, 1067.
[0004] There is great interest in synthesizing metal and
semiconductor nanoparticles due to their extraordinary properties,
which differ from those of the corresponding bulk material. An
example of a nanoparticle is nanoscale zero valent iron (nZVI).
Generally, nanoparticles are synthesized in three ways: physically
by crushing larger particles, chemically by precipitation, and
through gas condensation. Chemical generation is highly varied and
can incorporate laser pyrolysis, flame synthesis, combustion, and
sol gel approaches. See, U.S. Pat. No. 6,881,490 (2005-04-19) N.
Kambe, Y. D. Blum, B. Chaloner-Gill, S. Chiruvolu, S. Kumar, D. B.
MacQueen. Polymer-inorganic particle composites; J. Du, B. Han, Z.
Liu and Y. Liu, Cryst. Growth and Design, 2007, 7, 900; B. Wiley,
T. Herricks, Y. Sun and Y. Xia, Nano Lett., 2004, 4, 2057; C. J.
Murphy, A. M. Gole, S. E. Hunyadi and C. J. Orendorff, Inorg.
Chem., 2006, 45, 7544; B. J. Wiley, Y. Chen, J. M. McLellan, Y.
Xiong, Z-Y. Li, D. Ginger, and Y. Xia, Nanoletters, 2007, 4, 1032;
Y. Xiong, H. Cai, B. J. Wiley, J. Wang, M. J. Kim and Y. Xia, J.
Am. Chem. Soc., 2007, 129, 3665; J. Fang, H. You, P. Kong, Y. Yi.,
X. Song, and B. Ding, Cryst. Growth and Design, 2007, 7, 864; A.
Narayan, L. Landstrom and M. Boman, Appl. Surf. Sci., 2003, 137,
208; H. Song, R. M. Rioux, J. D. Hoefelmeyer, R. Komor, K. Niesz,
M. Grass, P. Yang and G. A. Somorjai, J. Am. Chem. Soc., 2006, 128,
3027; C. C. Wang, D. H. Chen and T. C. Huang, Colloids Surf., A
2001, 189, 145. Examples of mechanical processes for producing
nanoparticles include mechanical attrition (e.g., ball milling),
crushing of sponge iron powder, and thermal quenching. Examples of
chemical processes for producing nanoparticles include
precipitation techniques, sol-gel processes, and inverse-micelle
methods. Other chemical or chemically-related processes include gas
condensation methods, evaporation techniques, gas anti-solvent
recrystallization techniques, precipitation with a compressed fluid
anti-solvent, and generation of particles from gas saturated
solutions. The commercial significance of nanoparticles is limited
by the nanoparticle synthesis process, which is generally energy
intensive or requires toxic chemical solvents and is costly.
SUMMARY
[0005] The present invention relates to methods of making and using
compositions of metal nanoparticles formed by green chemistry
synthetic techniques, as well as the compositions themselves. For
example, the present invention relates to metal nanoparticles
formed with solutions of plant extracts and use of these metal
nanoparticles in removing contaminants from soil and
groundwater.
[0006] In one aspect, the invention provides methods for making
metal nanoparticles. In some embodiments, the methods comprise
providing a dissolved metal ion, for example a metal ion in
solution; providing a plant extract that comprises a reducing
agent, a polyphenol, caffeine, and/or a natural solvent or
surfactant; and combining the dissolved metal ion and the plant
extract to produce one or more metal nanoparticles. For example,
the dissolved metal ion can be provided by dissolving a metal salt
in water. For example, the dissolved metal ion can be provided by
dissolving a metal chelate in water. For example, the providing of
the dissolved metal ion, the providing of a plant extract, and/or
the combining of the dissolved metal ion and the plant extract to
produce one or more metal nanoparticles can be conducted at about
room temperature and/or at about room pressure. For example, room
temperature can be a temperature that is in a range that can be
tolerated by humans. For example, a temperature greater than or
equal to about that of the freezing point of water and less than or
equal to about the maximum temperature that naturally occurs on the
earth's surface can be considered to be room temperature. For
example, a temperature of greater than or equal to about 0.degree.
C., 4.degree. C., 10.degree. C., 15.degree. C., 20.degree. C.,
25.degree. C., 30.degree. C., 35.degree. C., 40.degree. C.,
45.degree. C., and 50.degree. C. and less than or equal to about
4.degree. C., 10.degree. C., 15.degree. C., 20.degree. C.,
25.degree. C., 30.degree. C., 35.degree. C., 40.degree. C.,
45.degree. C., 50.degree. C., and 60.degree. C. can be considered
to be room temperature. For example, room pressure can be pressure
that is greater than or equal to about the minimum that occurs on
the earth's surface (including mountaintops) and less that or equal
to about the maximum that occurs on the earth's surface (including
below sea level depressions and the bottom of mines). For example,
a pressure of greater than or equal to about 20 kPa, 30 kPa, 50
kPa, 70 kPa, 90 kPa, 95 kPa, 100 kPa, 101 kPa, 107 kPa, 120 kPa,
140 kPa, and less than or equal to about 30 kPa, 50 kPa, 70 kPa, 90
kPa, 95 kPa, 100 kPa, 101 kPa, 107 kPa, 120 kPa, 140 kPa, and 160
kPa can be considered to be room temperature. The metal
nanoparticles can be present in a concentration effective for use
in an application including, for example, soil and groundwater
remediation, water and wastewater treatment, air pollution
treatment, medical diagnostic testing, medical materials, targeted
drug delivery, catalysis of chemical synthesis reactions, pollution
control or monitoring devices, fuel cells, or electronics. The
dissolved metal ion can be present in an amount of, for example, at
least about 0.01 mM, 0.1 mM, 300 mM or more. The metal
nanoparticles can be formed at a rate of, for example, at least
about 0.002 mol/L/min, at least about 0.01 mol/L/min, at least
about 0.1 mol/L/min, at least about 0.5 mol/L/min or more, where
"mol" refers to the moles of metal atoms that form the metal
nanoparticles. The metal nanoparticles can have a mean diameter of
between about 5 and about 500 nm. A mass fraction of the metal
nanoparticles that have a diameter between about 50 nm and about
100 nm can be about 90 percent. The metal nanoparticles can have a
mean diameter between about 20 and about 250 nm, or between about
50 and about 100 nm. "Mean diameter" can refer to, for example, the
weight averaged mean diameter. That is, the mean diameter for a
group of particles can be determined as the sum of the diameter of
each individual particle weighted by its mass divided by the total
mass of the particles. The reducing agent, polyphenol, caffeine,
and/or natural solvent or surfactant can be one or more of, for
example, tea extract, green tea extract, coffee extract, lemon balm
extract, polyphenolic flavonoid, flavonoid, flavonol, flavone,
flavanone, isoflavone, flavans, flavanol, anthocyanins,
proanthocyanins, carotenoids, catechins, quercetin, and rutin. The
natural solvent or surfactant can be, for example, one or more of
VeruSOL.TM.-3, Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus
Burst 3 (CB-3), and EZ-Mulse.
[0007] In some embodiments, the metal nanoparticles can comprise
two or more metals. Methods of making such metal nanoparticles can
comprise, for example, providing a dissolved metal ion; providing a
plant extract that comprises a reducing agent, a polyphenol,
caffeine, and/or a natural solvent or surfactant; providing a
second dissolved metal ion, and combining the dissolved metal ion,
the second dissolved metal ion and the plant extract to produce one
or more metal nanoparticles each comprising a first and a second
metal. The first and second dissolved metal ions can be added to
the vessel more or less simultaneously, leading to nanoparticles in
which the first and second metals are interspersed throughout the
metal nanoparticles. Or the first dissolved metal ion can be added
to a vessel first and adding the second dissolved metal ion after a
period of time, for example, of at least about 15 or 30 seconds,
for example, a period of time in the range of from about 30 seconds
to about 60 seconds, which generally leads to nanoparticles in
which the first metal is present primarily in the core of the metal
nanoparticle and the second metal is present primarily in an outer
layer around the core of the metal nanoparticle. The first metal
can be, for example, iron and the second metal can be, for example,
palladium. Alternatively, palladium can be the first metal and iron
can be the second metal.
[0008] In some embodiments, the dissolved metal ion can be, for
example, a dissolved iron ion or a dissolved manganese ion. The
dissolved metal ion can be provided by a species including, for
example, a metal salt, an iron salt, ferric chloride (FeCl.sub.3),
ferrous sulfate (FeSO.sub.4), ferric nitrate (Fe(NO.sub.3).sub.3),
a manganese salt, manganese chloride (MnCl.sub.2), manganese
sulfate (MnSO.sub.4), a silver salt, silver nitrate (AgNO.sub.3), a
palladium salt, palladium chloride (PdCl.sub.2), a metal chelate,
Fe(III)-EDTA, Fe(III)-citric acid, Fe(III)-EDDS, Fe(II)-EDTA,
Fe(II)-citric acid, Fe(II)-EDDS, and combinations thereof. The
plant extract can be provided by a source including, for example,
tea, coffee, parsley, sorghum, marjoram, lemon balm, and
combinations thereof. Herein, unless otherwise stated, a source of
plant extract is to be understood as referring to the product or
material mentioned as well as sources, plant components associated
with sources, and processing intermediaries from which the product
or material is derived, byproducts and waste resulting from
manufacture of the product or material, and waste following use or
consumption of the product or material. For example, coffee as a
source of plant extract can be construed to include a brewed coffee
beverage as well as coffee fruit, coffee berries, coffee drupes,
coffee seeds, coffee beans, parts of the coffee plant, fermented
coffee beans, coffee bean processing wastewater, roasted coffee
beans, coffee bean chaff from roasting, ground coffee beans prior
to brewing, coffee powder, dehydrated instant coffee powder, coffee
grounds following brewing, and coffee concentrate. For example, tea
as a source of plant extract can be construed to include a brewed
tea beverage as well as tea plant buds, leaves, flushes, and other
parts of a tea plant, fermented tea leaves, oxidized tea leaves,
wilted tea leaves, post-fermented tea leaves, composted tea leaves,
tea bricks, tea powder, instant tea powder, and tea leaf waste
following brewing. In some embodiments, providing a plant extract
involves combining a plant or plant portion with the dissolved
metal ion in a vessel, causing, e.g., a reducing agent, polyphenol,
or caffeine to be released into the vessel to produce one or more
metal nanoparticles.
[0009] In some embodiments, the methods also comprise providing an
aqueous solution of carboxy methyl cellulose, and combining the
aqueous solution of carboxy methyl cellulose with the dissolved
metal ion and the plant extract to form metal nanoparticles coated
with carboxy methyl cellulose. The mixture of carboxy methyl
cellulose, dissolved metal ion, and plant extract can be heated,
for example to a temperature of about 100.degree. C., using a
method such as exposing the mixture to microwaves. In some
embodiments, the dissolved metal ion is provided in situ, for
example by adding a chelating agent to a soil and/or water to be
treated.
[0010] In some embodiments, the methods comprise providing a
dissolved metal ion; providing a plant derivative that comprises a
reducing agent, a polyphenol, caffeine, and/or a natural solvent or
surfactant; and combining the dissolved metal ion and the plant
derivative to produce one or more metal nanoparticles. The plant
derivative can be, for example, a plant extract or carboxy methyl
cellulose.
[0011] In another aspect, the invention provides compositions. The
compositions can comprise, for example, a metal nanoparticle
prepared according to any of the methods disclosed herein. The
metal nanoparticle can be, for example, coated with a substance
derived from the plant extract used in the preparation of the metal
nanoparticle--i.e., the plant extract serves as a capping agent or
dispersing agent for the nanoparticles. The composition can also
comprise a natural solvent or surfactant, such as, for example,
VeruSOL.TM.-3, Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus
Burst 3 (CB-3), EZ-Mulse, or combinations thereof. The composition
can also comprise a chelating agent, such as, for example, EDTA,
EDDS, citric acid, or combinations thereof. The compositions can
also comprise an oxidant, such as, for example, peroxide, calcium
peroxide, hydrogen peroxide, air, oxygen, ozone, persulfate, sodium
persulfate, percarbonate, permanganate, or combinations thereof.
The compositions can also comprise a carboxymethylcellulose coating
or a hydrophobic coating on the surface of the metal nanoparticle.
The metal nanoparticle can be, for example, a zero valent metal
nanoparticle, a zero valent iron nanoparticle, a zero valent
manganese nanoparticle, a silver nanoparticle, a palladium
nanoparticle, a gold nanoparticle, a platinum nanoparticle, an iron
nanoparticle, a manganese nanoparticle, a copper nanoparticle, an
indium nanoparticle, or combinations thereof, and thus can also
comprise at least two different metals, for example iron and
palladium.
[0012] In still another aspect, the invention provides methods for
reducing the concentration of one or more contaminants in a medium.
The methods can comprise, for example, causing a metal nanoparticle
prepared according to the methods described herein to be present in
the medium; and allowing the metal nanoparticle to reduce or
stimulate biological reduction of the contaminant to reduce its
concentration. For example, a contaminant can be a chemical of
concern (COC), such as a non-aqueous phase liquid (NAPL), dense
non-aqueous phase liquid (DNAPL), and/or light non-aqueous phase
liquid (LNAPL). The metal nanoparticle can be previously prepared
and thereafter introduced into the medium, or it can be formed in
situ, for example by introducing a reducing agent, a polyphenol,
caffeine, and/or a natural solvent or surfactant into the medium;
and allowing the reducing agent, polyphenol, caffeine, and/or a
natural solvent or surfactant to react with the dissolved metal
ions in the medium to form metal nanoparticles. The methods can
also comprise administering a chelating agent, such as, for
example, EDTA, citric acid, EDDS, or combinations thereof, to the
medium. The contaminant can be, for example, a perchlorate,
nitrate, heavy metals or heavy metal compounds, Hg.sup.2+,
Ni.sup.2+, Ag.sup.+, Cd.sup.2+, Cr.sub.2O.sub.7.sup.2-,
AsO.sub.4.sup.3-, compounds comprising any of these, and
combinations. The methods can also comprise introducing a natural
solvent or surfactant, such as, for example, VeruSOL.TM.-3, Citrus
Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus Burst 3 (CB-3),
EZ-Mulse or combinations thereof, into the medium. The metal
nanoparticle and the natural solvent and/or surfactant can be
introduced into the medium by injection into a subsurface. The
methods can also comprise introducing an oxidant into the medium.
The medium can be, for example, a biologically contaminated
material, soil, groundwater, water, wastewater, air, or
combinations thereof.
[0013] In yet another aspect, the invention provides methods for
determining an optimal amount of dissolved metal ion to add to a
plant extract solution in synthesizing metal nanoparticles. The
method can comprise providing several aqueous solutions of a first
set having different concentrations of a plant extract; adding DPPH
to each aqueous solution of the first set; determining DPPH
absorbance of each aqueous solution of the first set; adding a
dissolved metal ion to several aqueous solutions of a second set
having different concentrations of the plant extract to form metal
nanoparticles; adding DPPH to each aqueous solution of the second
set comprising metal nanoparticles and remaining plant extract;
determining DPPH absorbance of each aqueous solution of the second
set; comparing the DPPH absorbance of the aqueous solutions of the
first set and of the aqueous solutions of the second set to
determine the net consumption of DPPH; and determining the optimal
ratio of dissolved metal ions to plant extract.
[0014] In still another aspect, the invention provides devices
comprising a metal nanoparticle prepared according to any of the
methods disclosed herein. The device can be, for example, a medical
diagnostic test, a medical material such as a bandage, a targeted
drug delivery vehicle, a chemical synthesis system, a pollution
control or monitoring device, a fuel cell, and an electronic
device.
DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 presents a graph of specific conductivity as a
function of cumulative effluent volume in Column 1--Lemon Balm
Extract with Fe(NO.sub.3).sub.3.
[0016] FIG. 2 presents a graph of specific conductivity as a
function of cumulative effluent volume in Column 2--green tea
extract with Fe(NO.sub.3).sub.3.
[0017] FIG. 3 presents transmission electron micrographs of silver
and palladium nanoparticles in aqueous solutions of coffee and tea
extract cast on a carbon coated copper grid. (a) Silver
nanoparticles from coffee extract. (b) Silver nanoparticles from
tea extract. (c) Palladium nanoparticles from coffee extract. (d)
Palladium nanoparticles from tea extract.
[0018] FIG. 4 presents TEM images of silver nanoparticles
synthesized with coffee and tea extracts.
[0019] FIG. 5 presents TEM images of palladium nanoparticles
synthesized with coffee and tea extracts.
[0020] FIG. 6 presents TEM images of Ag and Pd nanoparticles
prepared in aqueous solutions using catechin.
[0021] FIG. 7 presents a graph of the spectra of absorbance as a
function of wavelength for a solution of tea extract with silver
nitrate at various times. (a) Pure tea extract. (b) After 1 min.
(c) After 20 min. (d) After 40 min. (e) After 60 min. (f) After 2
hrs.
[0022] FIG. 8 presents a graph of UV-Visible spectra of Ag and Pd
nanoparticles in aqueous solutions of coffee and tea leaves
extract. (a) Ag nanoparticles from coffee extract. (b) Ag
nanoparticles from tea extract. (c) Pd nanoparticles from coffee
extract. (d) Pd nanoparticles from tea extract. The inset shows
UV-Visible spectra of (a) coffee and (b) tea extract.
[0023] FIG. 9 presents a graph of voltage as a function of time for
coffee extract in 1M sodium chloride solution.
[0024] FIG. 10 presents a graph of intensity as a function of 2
theta angle for silver and palladium nanoparticles in coffee and
tea extract. (a) Silver nanoparticles from coffee extract. (b)
Silver nanoparticles from tea extract. (c) Palladium nanoparticles
from coffee extract. (d) Palladium nanoparticles from tea
extract.
[0025] FIG. 11 presents TEM images of gold nanoparticles reduced
with solutions of catechin. 2 mL 0.01N solutions of gold ions
reduced with: (a) 2 mL; (b) 4 mL; (c) 6 mL; and (d) 8 mL of
catechin in (0.1N) aqueous solution
[0026] FIG. 12 presents TEM images of gold nanowires reduced with
solutions of caffeine. 2 mL 0.01N solutions of gold ions reduced
with (a) with 25 mg (b) 100 mg (c) 200 mg and (d) 300 mg of
caffeine.
[0027] FIG. 13 presents a graph illustrating plant extract DPPH
stable radical consumption from nanoscale zero valent iron particle
formation from reaction of green tea extract with ferric
chloride.
[0028] FIG. 14 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M ferric chloride
with 0 g/L VeruSOL.TM.-3.
[0029] FIG. 15 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M ferric chloride
with 2 g/L VeruSOL.TM.-3.
[0030] FIG. 16 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M ferric chloride
with 5 g/L VeruSOL.TM.-3.
[0031] FIG. 17 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M ferric chloride
with 10 g/L VeruSOL.TM.-3.
[0032] FIG. 18 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M Fe(III)-EDTA with
0 g/L VeruSOL.TM.-3.
[0033] FIG. 19 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M Fe(III)-EDTA with
5 g/L VeruSOL.TM.-3.
[0034] FIG. 20 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M Fe(III)-citric
acid with 0 g/L VeruSOL.TM.-3.
[0035] FIG. 21 presents a micrograph of green tea synthesized zero
valent iron nanoparticles made by combining 0.1 M Fe(III)-citric
acid with 5 g/L VeruSOL.TM.-3.
[0036] FIG. 22 presents a graph depicting UV spectra of (a) Fe, (b)
tea extract and (c) reaction product of Fe(NO.sub.3).sub.3 and tea
extract. Inset shows the photographic image of the reaction.
[0037] FIG. 23 presents a representative XRD pattern of iron
nanoparticles synthesized using tea extract.
[0038] FIG. 24 presents a graph depicting concentration-dependent
bromothymol blue dye absorbance.
[0039] FIG. 25 presents a graph depicting UV-Vis Spectra
(Absorbance versus Wavelength) of bromothymol blue over time for an
initial solution containing 500 ppm bromothymol blue (pH 6), 2%
H.sub.2O.sub.2, and 0.06 mM GT-nZVI.
[0040] FIG. 26 presents a graph depicting UV-Vis Spectra of
bromothymol blue over time for an initial solution containing 500
ppm bromothymol blue (pH 6), 2% H.sub.2O.sub.2, and 0.33 mM
GT-nZVI.
[0041] FIG. 27 presents a graph of concentration versus time
depicting degradation of bromothymol blue with GT-nZVI catalyzed
H.sub.2O.sub.2. (a) bromothymol blue with 2% peroxide
solution--control, (b) bromothymol blue treated with 0.03 mM (as
Fe) GT-nZVI catalyzed hydrogen peroxide (HP) (2%), (c) bromothymol
blue treated with 0.06 mM (as Fe) GT-nZVI catalyzed HP (2%), (d)
bromothymol blue treated with 0.12 mM (as Fe) GT-nZVI catalyzed HP
(2%), (e) bromothymol blue treated with 0.33 mM (as Fe) GT-nZVI
catalyzed HP (2%).
[0042] FIG. 28 presents initial rates, in In[BTB] vs. time, of
decomposition of bromothymol blue with GT-nZVI catalyzed
H.sub.2O.sub.2. (a) bromothymol blue with 2% peroxide
solution--control, (b) bromothymol blue treated with 0.03 mM (as
Fe) GT-nZVI catalyzed HP (2%), (c) bromothymol blue treated with
0.06 mM (as Fe) GT-nZVI catalyzed HP (2%), (d) bromothymol blue
treated with 0.12 mM (as Fe) GT-nZVI catalyzed HP (2%), (e)
bromothymol blue treated with 0.33 mM (as Fe) GT-nZVI catalyzed HP
(2%).
[0043] FIG. 29 presents the initial rate constants for the
decomposition of bromothymol blue with GT-nZVI catalyzed
H.sub.2O.sub.2 as a function of Fe concentration, expressed in
terms of rate (min.sup.-1) versus GT-nZVI concentration (mM) as Fe
(y=0.4694x-0.0106R.sup.2=0.9989).
[0044] FIG. 30 presents the degradation of bromothymol blue
concentration over time with Fe-EDTA and Fe-EDDS catalyzed
H.sub.2O.sub.2. (a) bromothymol blue treated with 0.12 mM Fe
catalyzed HP (2%), (b) bromothymol blue treated with 0.33 mM as Fe
catalyzed HP (2%), (c) bromothymol blue treated with 0.50 mM as Fe
catalyzed HP (2%), (d) bromothymol blue treated with 0.66 mM as Fe
(Fe-EDDS only) catalyzed HP (2%).
[0045] FIG. 31 presents the initial rates, expressed in terms of
In[BTB] versus time, of decomposition of bromothymol blue with
Fe-EDTA and Fe-EDDS catalyzed H.sub.2O.sub.2. (a) bromothymol blue
treated with 0.12 mM Fe catalyzed HP (2%), (b) bromothymol blue
treated with 0.33 mM as Fe catalyzed HP (2%), (c) bromothymol blue
treated with 0.50 mM as Fe catalyzed HP (2%), (d) bromothymol blue
treated with 0.66 mM as Fe (Fe-EDDS only) catalyzed HP (2%).
[0046] FIG. 32 presents the initial rate constants for the
decomposition of bromothymol blue as a function of Fe
concentration, with Fe-EDTA and Fe-EDDS: Rate (min.sup.-1) vs
Fe-EDTA or Fe-EDDS (mM) as Fe. Fe-EDTA: y=-0.0016x+0.0043
(R.sup.2=0.9963), Fe-EDDS: y=-0.0099x+0.0164 (R.sup.2=0.7135).
[0047] FIG. 33 presents a graph depicting the concentration
dependent absorption of bromothymol blue (pH <6) (Standard
curve).
[0048] FIG. 34 presents a series of graphs depicting a
time-dependent Au-10 reaction after (a) 0 minutes (control); (b) 1
minute; (c) 2 minutes; and (d) 3 minutes.
[0049] FIG. 35 presents UV spectra of (a) Au-8 (b) Au-3 and (c)
Au-13 samples.
[0050] FIG. 36 presents UV spectra of (a) Au-15, (b) Au-5 and (c)
Au-10 samples.
[0051] FIG. 37 presents UV spectra of (a) Au-7 and (b) Au-12
samples.
[0052] FIG. 38 presents UV spectra of (a) Au-11, (b) Au-1 and (c)
Au-6 samples.
[0053] FIG. 39 presents XRD patterns for (a) Au-4, (b) Au-9, (c)
Au-14, (d) Au-1, (e) Au-11, (f) Au- 5, (g) Au-10 and (h) Au-8.
[0054] FIG. 40 presents SEM images of (a) Au-1, (b) Au-2 and (c-d)
Au-4 samples.
[0055] FIG. 41 presents SEM image of (a) Au-11 (b) Au-12 and (c-d)
Au-14 samples.
[0056] FIG. 42 presents SEM images of (a) Au-6 (b) Au-8 (c) Au-9
and (c) Au-10 samples.
[0057] FIG. 43 presents representative EDX spectra of Aux
nanostructures obtained using an Au-6 sample.
[0058] FIG. 44 presents TEM images of (a-b) Au-1, (c) Au-2 and (d)
Au-5 samples.
[0059] FIG. 45 presents TEM image of (a-b) Au-3 and (c-d) Au-4
samples.
[0060] FIG. 46 presents XRD patterns for butyl ammonium
bromide-reduced Au nanostructures.
DETAILED DESCRIPTION
[0061] Embodiments of the invention are discussed in detail below.
In describing embodiments, specific terminology is employed for the
sake of clarity. However, the invention is not intended to be
limited to the specific terminology so selected. A person skilled
in the relevant art will recognize that other equivalent parts can
be employed and other methods developed without parting from the
spirit and scope of the invention. All references cited herein are
incorporated by reference as if each had been individually
incorporated. For example, U.S. Appl. No. 12/068,653 and U.S. Prov.
Appl. No. 61/071,785 are hereby incorporated by reference.
[0062] "Introduce" means to cause to be present in a location. A
material or item can be introduced into a location even if the
material or item is released somewhere else and must travel some
distance in order to reach the location. For example, if a
substance is released at location A, and the substance will migrate
over time to location B, the substance has been "introduced" into
location B when it is released at location A. An item can be
introduced in any manner appropriate under the circumstances for
the substance to be introduced into the location.
[0063] "Effective" means sufficient to accomplish a purpose, and
"effective amount" or "effective concentration" means an amount or
concentration sufficient to accomplish a purpose. The purpose can
be accomplished by effecting a change, for example by decreasing
the concentration of a contaminant in a location to be remediated.
A purpose can also be accomplished where no change takes place, for
example if a change would have taken place otherwise.
[0064] "Plant derivative" encompasses any portion of a plant that
can be used according to the purposes of the present invention, for
example to bring about the formation of metal nanoparticles from
dissolved metal ions. "Plant derivative" encompasses, for example,
"plant extract." As used herein, a "plant extract" encompasses, for
example, any chemical or combination of chemicals found in a plant
or that can be prepared using a chemical or chemicals found in a
plant, whether by preparing derivatives of the compounds found in
the plant via chemical reaction. As used herein, "plant derivative"
also encompasses carboxy methyl cellulose.
[0065] As used herein, "nano-sized" and "nano-scale" mean particles
less than about 1 micron in diameter, though a different meaning
may be apparent from the context. As used herein, "micro-sized" and
"micro-scale" mean particles from about 1 to about 1000 microns in
diameter. As used herein, "macro-sized" and "macro-scale" mean
particles greater than about 1000 microns in diameter. A
"nanoparticle" is a particle whose diameter falls within the
nano-scale range. A nanoparticle can be zero-valent, or it can
carry a charge.
[0066] As used herein, "medium" encompasses any location or item in
which contaminants can be found. For example, "medium" includes,
without limitation, a biologically contaminated material, soil,
groundwater, water, wastewater, air, and combinations thereof.
[0067] "Contaminants" encompasses any substance present in a
location that, by its presence, diminishes the usefulness of the
location for productive activity or natural resources, or would
diminish such usefulness if present in greater amounts or if left
in the location for a length of time. The location may be
subsurface, on land, in or under the sea or in the air. As used
herein, "contaminated soil" encompasses any soil that contains at
least one contaminant according to the present invention.
"Contaminant" thus can encompass trace amounts or quantities of
such a substance. Examples of productive activities include,
without limitation, recreation; residential use; industrial use;
habitation by animal, plant or other life form, including humans;
and similar such activities. Examples of natural resources are
aquifers, wetlands, sediments, soils, plant life, animal life,
ambient air quality.
[0068] A "vessel" is any container or location that is capable of
supporting the reactions and preparative methods disclosed herein.
For example, a vessel can be a beaker, column, pot, mixing
apparatus, vat, or any other laboratory or manufacturing apparatus
that can hold gases, liquids and/or solids. As used herein, a
"vessel" can also be a location in need of remediation.
[0069] As used herein, "plant portion" means any part of a plant
that can be used as a source of reactants in the nanoparticle
preparation methods disclosed herein. For example, sorghum is very
rich in phenolics, such that it is generally not necessary to
perform an extraction before using sorghum phenolics in the
preparation of metal nanoparticles. Instead, it is possible to
prepare nanoparticles simply by placing a sorghum plant, or portion
thereof, into the reaction vessel. Examples of "plant portions"
include, for example, the husk, stem, root, leaves, flower, fruit,
seed, or any other part of the plant.
[0070] Conventional methods for manufacturing metal nanoparticles,
such as nZVI or nZVMn, include milling and solution methods. Many
conventional methods, for example the high energy milling method,
involve the use of toxic solvents and industrial surfactants to
prevent oxidation of iron, for example during the crushing
operation. Solution methods use toxic inorganic chemicals,
including strong chemical reducing agents such as sodium
borohydride, dispersing agents, and stabilization agents. Sodium
borohydride, a commonly used reducing agent use to make zero valent
iron nanoparticles, is a highly hazardous material. After making
zero valent iron nanoparticles using sodium borohydride, the sodium
borohydride must be washed from the zero valent iron nanoparticles,
resulting in the generation of liquid hazardous wastes.
[0071] By contrast, the invention encompasses green methods of
making metal nanoparticles, such as zero valent metal
nanoparticles, including green chemistry methods. Green chemistry
is the design, development, and implementation of chemical products
and processes for the purpose of reducing or eliminating the use
and generation of substances hazardous to human health and the
environment. See, P. T. Anastas and J. C. Warner, Green Chemistry:
Theory and Practice; Oxford University Press, Inc.: New York, 1998.
To address mounting environmental concerns regarding conventional
approaches, green chemistry methods involve the use of
environmentally benign solvents, biodegradable polymers, and
non-toxic chemicals.
[0072] In an embodiment of the invention, metal nanoparticles are
synthesized by reducing the corresponding metal ion salt solutions.
Green chemistry can be employed, for example, in the (i) choice of
solvent, (ii) the choice of reducing agent, and (iii) the choice of
capping agent (or dispersing agent) used. Multifunctional
environmentally-friendly materials can be used in synthesizing
metal nanoparticles. For example, tea and/or coffee extract, which
can contain polyphenols, can function both as a reducing agent and
a capping agent in producing, e.g., silver (Ag), palladium (Pd),
gold (Au) and iron (Fe) nanoparticles. Caffeine and/or polyphenols
can form complexes with metal ions in solution and reduce them to
the corresponding metals. Nanoparticles, e.g. of noble metals,
transition metals, manganese (Mn), copper (Cu), gold (Au), platinum
(Pt), and indium (In) can be produced with this method. The
nanoparticles can be of zero valent metal. Tea and coffee extracts
have high water solubility and low toxicity and are
biodegradable.
[0073] In an embodiment of the invention, bulk quantities of
nanoparticles, or nanocrystals, of metals such as transition
metals, noble metals, silver (Ag), gold (Au), platinum (Pt),
palladium (Pd), and iron (Fe), manganese (Mn), copper (Cu), and
indium (In) are produced in a single pot method using coffee and/or
tea extract, e.g., green tea extract, at room temperature. The
nanoparticles can be of zero valent metal. The nanoparticles can be
produced without a separate surfactant, capping agent, or template.
The nanoparticles obtained can have a size range of from about 5 to
about 500 run, for example about 20 to about 60 nm and can be
crystallized in face centered cubic symmetry. Size can be
understood as diameter of a nanoparticle. For example, diameter can
be the volume diameter, that is (6V/.pi.).sup.1/3, where V is the
volume of the nanoparticle. Plant extracts containing high
concentration of reducing agents, including polyphenolic compounds
can be used to synthesize nanometal particles in addition to those
from tea and coffee can be used. For example, extracts of parsley,
sorghum, marjoram, aronia, crowberry, spinach, potato, beets,
spruce needles, willowherb, rosemary, meadowsweet and lemon balm
can be used to produce nanometals at room temperatures and
pressures, without the use of toxic or hazardous chemicals or the
production of wastes containing toxic or hazardous chemicals.
Sources of compounds useful for producing metal nanoparticles can
include, for example, berries, fruits, vegetables, herbs, medical
plants, cereals, and tree materials. Waste products, process
streams, or by-products from plant processing containing high
concentrations of plant polyphenols can be used. The materials can
include fruit juice pulp, fruit juice manufacturing wastewater,
fruit juice manufacturing waste, food processing waste or byproduct
materials, wine and beer manufacture and forest product processing
waste streams. Compounds useful for producing metal nanoparticles
can include polyphenols, antioxidants, radical scavengers,
polyphenolic flavonoids, flavinoid phenolic compounds, flavinoids,
flavonoids, flavonols, flavones, flavanones, isoflavones, flavans,
flavanols, anthocyanins, proanthocyanins, carotenoids, catechins,
quercetins, rutins, catechins, epicatechins and their esters from
ferulic and gallic acids, e.g. epigallocatechin. Antioxidant
compounds that can be useful for metal nanoparticle synthesis
include natural antioxidants such as flavonoids, e.g., quercetin,
glabridin, red clover, and Isoflavin Beta (a mixture of isoflavones
available from Campinas of Sao Paulo, Brazil). Other examples of
natural antioxidants that can be used as antioxidants for
synthesizing metal nanoparticles include beta carotene, ascorbic
acid (vitamin C), vitamin B1, vitamin B2, tocopherol (vitamin E)
and their isomers and derivatives. Non-naturally occurring
antioxidants, such as beta hydroxy toluene (BHT) and beta hydroxy
anisole (BHA), can also be used to synthesize metal nanoparticles.
Plant oil based surfactants can be used to synthesize metal
nanoparticles, such as polyethylene glycol (PEG) modified plant
oils. Plant oils such as castor oil, corn oil, palm oil, coconut
oil, canola oil, cottonseed oil, almond oil, olive oil, rapeseed
oil, peanut oil, safflower oil, sesame oil, sunflower oil, acai
oil, flax seed oil, hemp oil and algae-derived oil.
[0074] Plant extracts that are U.S. FDA Generally Recognized as
Safe (GRAS) can be used. The synthesis of metal nanoparticles, such
as zero valent iron nanoparticles, with natural resources, can
avoid generating hazardous waste and thus can reduce environmental
risk. Methods for making metal nanoparticles with plant-based
extracts can be easier and safer than conventional methods of
making metal nanoparticles.
[0075] The green synthesized nanoparticles and compositions
including these nanoparticles according to embodiments of the
invention can be used, for example, to remediate contaminated sites
by inducing chemical reduction mechanisms, by stimulating
biological reduction mechanisms, or by a combination of chemical
and biological reduction mechanisms. For example, the green
synthesized nanoparticles, including zero valent nanometal
particles and bimetallic particles, can serve as reducing agents in
processes to detoxify inorganic species, such as metals, heavy
metals, arsenical compounds, and chromium compounds, e.g.,
Hg.sup.2+, Ni.sup.2+, Ag.sup.+, Cd.sup.2+, Cr.sub.2O.sub.7.sup.2-,
and AsO.sub.4.sup.3-, by in-place manufacture and treatment. The
green synthesized nanoparticles, e.g., zero valent nanometal
particles, can be used as reducing agents to destroy oxidizing
agent compounds such as perchlorates (ClO.sub.4.sup.-) and nitrates
(NO.sub.3.sup.-). The metal nanoparticles can be administered with,
for example, plant derived reducing agents, in order to increase
the reducing effect of the nanoparticles on the species to be
remediated.
[0076] The nanoparticles and compositions including them can be
used for catalysis, for example, to activate free radical oxidation
chemistries for remediation, water treatment, and wastewater
treatment. Green synthesized nanoparticles, such as nZVI or nZVMn
particles, and compositions including them can be applied to
remediate sites contaminated with, for example, non-aqueous phase
liquids (NAPLs), dense non-aqueous phase liquids (DNAPLs), and/or
light non-aqueous phase liquids (LNAPLs). The green synthesized
nanoparticles can be applied together with VeruTEK's VeruSOL.TM.
green co-solvents and surfactants and/or oxidants. For example, the
metal nanoparticles can be applied with oxidants such as peroxide
(e.g., calcium peroxide, hydrogen peroxide), air, oxygen, ozone,
persulfate (e.g., sodium persulfate), percarbonate, and
permanganate. The green synthesized nanoparticles can be used, for
example, to remediate contaminated water, wastewater, building
materials and equipment, and subsurfaces. nZVI can be produced with
green tea and ferric chloride in the presence or absence of
VeruSOL.TM.-3. Similarly, nZVI can be produced with green tea and
chelated iron in the presence or absence of VeruSOL.TM.-3.
[0077] The nanoparticles according to the invention and
compositions including them can be applied in conjunction with, for
example, catalyzed oxidant systems or reduction technologies to
destroy DNAPL or LNAPL compounds. Thus, nanoparticles according to
the invention and compositions including them can be used, for
example, to treat CERCLA Sites, NPDES permitted discharges, and
RCRA Sites. Furthermore, systems regulated under the Safe Drinking
Water Act, Clean Water Act, FIFRA, and TSCA can be treated using
nanoparticles according to the invention and compositions including
them. For example, agencies of the U.S. Government, such as the
Department of Defense, are responsible for sites that can benefit
from treatment with materials according to the invention, such as
nanoparticles and compositions including them. Use of the materials
according to the invention to treat water, wastewater, and
contaminated soils can reduce risks to the public and
environment.
[0078] For example, green synthesized silver or composite silver
nanometals according to the invention can be used to disinfect
materials and disinfect biological agents. Such silver or composite
silver nanometals can be, for example, incorporated into medical
materials to provide disinfecting properties. Metal nanoparticles
can have additional medical applications.
[0079] Nano-scale zero valent iron (nZVI) is of increasing interest
for use in a variety of environmental remediation, water and waste
water treatment applications. Initial ZVI research used microscale
( 150 .mu.m) particles for environmental applications in reactive
subsurface permeable barriers (PRBs) for chemical reduction of
chlorinated solvents. In comparison to larger sized ZVI particles,
nZVI has a greater reactivity due to a greater surface area to
volume ratio. Recent environmental applications include removal of
nitrite by ultrasound dispersed nZVI, dechlorination of
dibenzo-P-dioxins, reduction of chlorinated ethanes, adsorption of
humic acid and its effect on arsenic removal and hexavalent
chromium removal. However, field applications of ZVI have been
limited to granular particles used in permeable reactive barriers
(PRB). While PRBs are found to be effective for the remediation of
shallow aquifers, more cost-effective in situ technologies are
needed for rapid and complete destruction of chlorinated
contaminants in deep aquifers and in source zones. However, for
this technology to be feasible, the nZVI particles must be small
enough to be mobile in the targeted zones, and the transport
behaviors (or size) of the nanoparticles in various soils must be
controllable.
[0080] A technique for preparing nZVI particles of controlled size
and transport properties was previously unavailable, and a method
is lacking to extend the reactive lifetime of these relatively
short-lived nanoparticles. Their extreme reactivity is addressed in
this investigation, as the relative stability of such nZVI
particles has been enhanced using tea polyphenols which cap the
ensuing nanoparticles. Table 1 presents examples of green tea
manufacture of nanoscale zero valent iron particles, for example
with cosolvent-surfactant mixtures, ferric chloride and chelated
iron.
TABLE-US-00001 TABLE 1 Green Tea Manufacture of Nanoscale Zero
Valent Iron Particles with Cosolvent-Surfactant Mixtures, Ferric
Chloride and Chelated Iron Testing Conditions Chemical doses Total
Chumnee T.E. FeCl.sub.3 Volume VS-3 (20 g/L) (0.1M) Fe-EDTA
Fe-Citric Acid Sample ID ml g/L mL mL 0.1M as Fe 0.1M as Fe Tea
NZVI-T1 480 2 160 320 -- -- Tea NZVI-T2 480 5 160 320 -- -- Tea
NZVI-T3 480 10 160 320 -- -- Tea NZVI-T4 480 0 160 320 -- -- Tea
NZVI-T5 480 0 160 -- 320 -- Tea NZVI-T6 480 5 160 -- 320 -- Tea
NZVI-T7 480 0 160 -- -- 320 Tea NZVI-T8 480 5 160 -- -- 320
[0081] Gold nanostructures have been the focus of intense research
owing to their fascinating optical, electronic, and chemical
properties and promising applications in nanoelectronics,
biomedicine, sensing, and catalysis. A variety of methods have been
developed to fabricate gold nanoparticles using NaBH.sub.4,
microwave, simple galvanic replacement reaction (transmetalation
reaction), polymeric strands of oleylamine-AuCl complexes,
poly(vinyl pyrrolidone) (PVP) in aqueous solutions, reducing agent
(ascorbic acid), seed-mediated synthesis and ionic polymers. Wet
methods often require the use of an aggressive chemical reducing
agent such as sodium borohydride, hydroxylamine, and/or a capping
agent and may additionally involve an organic solvent such as
toluene or chloroform. Although these methods may successfully
produce pure, well-defined metal nanoparticles, the cost of
production is relatively high both materially and environmentally.
Consequently, more cost-effective and environmentally benign
alternatives to these existing methods should be developed. The
choice of an environmentally compatible solvent system, an
eco-friendly reducing agent, and a nonhazardous capping agent for
the stabilization of the nanoparticles are three main criteria for
a totally "green" nanoparticle synthesis. Recently, there has been
an increased emphasis on the topics of "green" chemistry using
environmentally benign and renewable materials as the respective
reducing and protecting agents. The use of environmentally benign
and renewable materials in the production of metal nanoparticles is
important for pharmaceutical and biomedical applications.
[0082] In addition to their uses in remediation applications, metal
nanoparticles prepared according to embodiments of the invention
can be useful in a wide variety of fields. For example, gold
nanoparticle applications include the following: due to the low
oxidation metal potential associated with gold nanoparticles, gold
nanoparticles can be used in medical diagnostic tests, such as,
labeling, immunostain, x-ray contrasting, and phagokinetic tracking
studies; targeted drug delivery techniques, for example conjugated
with ligands or proteins, and also those involving gene guns,
uptake by cells, and as a heat source to kill selected cells such
as cancer using targeting cell hypothermia, optically triggered
opening of DNA bonds. Gold nanoparticles with phytochemical
coatings have shown significant affinity toward prostate (PC-3) and
breast (MCF-7) cancer cells.
[0083] Gold nanoparticles are valuable catalysts in chemical
synthesis reactions and for pollution control devices, such as
those involving (1) colorimetric detection methods for cysteine
based oligonucleotide-functionalized gold nanoparticle probes that
contain strategically placed thymidine-thymidine (T-T) mismatches
to complex Hg.sup.2+ ions; and (2) colorimetric metal sensors based
on DNAzyme-directed assembly of gold nanoparticles and their use
for sensitive and selective detection and quantification of metal
ions, particularly lead in leaded paint. Fuel cell applications
include use of gold nanoparticles on carbon supports. Electronic
devices also use gold nanoparticles for superior conductance. Other
uses for metal nanoparticles include cancer cell and DNA
hypothermic inactivation, biological agent inactivation, full
cells, and toxicity reduction.
[0084] In some embodiments, the reducing agent used in preparing
the metal nanoparticles can be, without limitation, a phenolic
compound, a phenolic plant extract, a plant extract-based
surfactant, a natural solvent or surfactant, a plant oil based
surfactant, a flavonoid, or combinations thereof. In some
embodiments, the reducing agent is extracted using a plant-based
solvent, such as d-limonene and citrus terpenes.
[0085] In some embodiments, the plant extract and/or reducing agent
is further concentrated for example prior to use in the preparation
of metal nanoparticles. The concentration process can produce a
higher concentration of plant polyphenols, enabling a high
concentration of dissolved metal to be used to make higher
concentrations of nanometal particles. The plant extract and/or
reducing agent can be concentrated using any method known in the
art, for example using reverse osmosis and/or filter presses or
using extraction with supercritical carbon dioxide. Similarly, the
green synthesized nanometal particles can be further concentrated,
for example after they are prepared, to produce higher
concentrations of nanometal particles. Concentration methods
include, but are not limited to, centrifugation, filtrations,
magnetic separation, electroosmosis, and electrokinetic
migration.
[0086] Free radicals initiated from catalysis or activation of
hydrogen peroxide or sodium persulfate can be readily
experimentally determined using probe compounds such as bromothymol
blue. Bromothymol blue has an advantage over methylene blue as a
probe compound as it is not directly oxidized (in the absence of
free radicals) by sodium persulfate. Methylene blue is directly
oxidized by sodium persulfate, therefore it cannot be used to
experimentally determine free radical generation and subsequent
destruction by sodium persulfate. The advantage of bromothymol blue
is that it is not directly oxidized by either hydrogen peroxide or
sodium persulfate.
[0087] In the process of experimentally optimizing the initiation
and generation of free radicals using various catalysis or
activators, bromothymol blue is superior to many other probe
compounds in that various catalysts and activators can be rapidly
evaluated. For example, Fe-chelated metal catalysts such as
Fe-TAML, Fe-EDTA, Fe-EDDS, Fe-EDDHA, Fe-EDDHMA, Fe-EDDCHA,
Fe-EDDHSA, Fe-NTA, and Fe-DTPA can be used as catalysts for
peroxide and persulfate. Other transition metal catalysts can also
be used, such as Mn, Co, Ni, Cu, and Zn. Additionally, nanoparticle
catalysts, such as nanoiron, bimetallic nanoiron species such as
Fe/Ni, Fe/Pd, Fe-oxides, Mn-oxides, silicates, alumina, and mixed
transition metal oxides, can be used.
[0088] In many industrial applications, the faster the catalysis of
peroxide and persulfate the better. However, the catalysis of
peroxide and persulfate in subsurface remediation applications is
best conducted at a controlled rate and in many cases as slow as
possible, while still maintaining effective catalysis. Slowing the
catalysis rates using plant extract and plant extract-based
surfactants is effectively achieved and the desired rate obtained
using bromothymol blue as a probe compound. Inclusion of plant
extracts can reduce the rate of catalysis to, for example, 90%,
75%, 50%, 25%, 10%, 5%, 1% or less, compared to the rate without
plant extract-containing catalysts. In terms of initial rate
constants, the plant extract-controlled catalysts may decrease the
initial rate constant to 0.2/min, 0.1/min, 0.05/min, 0.01 /min,
0.005/min or otherwise as described for a particular
application.
[0089] In some embodiments, the invention provides methods of using
bromothymol blue as a probe compound. Bromothymol blue can be used,
for example, to optimize the rate of peroxide or persulfate
catalysis, for example using: a) bromothymol blue; b) a catalyst or
mixture of catalysts, and optionally one or more of c) an oxidant
stabilizer; d) a catalyst stabilizer; e) a soil sample; and/or f) a
contaminant.
[0090] Examples of oxidant stabilizers include, without limitation,
plant extracts, surfactants including, for example, plant-extract
based surfactants, and/or plant extract solvents and cosolvents.
Examples of catalyst stabilizers include, without limitation, plant
extracts, surfactants including, for example, plant-extract based
surfactants, chelates, poly(ethylene terephthalate),
poly(amidoamine)-dendrime, polyethylene glycol and nanometal
capping agents. In addition, the nanometal particle morphology can
be optimized for the formation of free radicals in peroxide and/or
persulfate catalysis.
[0091] A DPPH test can be used to measure the gross antioxidant
capacity of plant extracts. DPPH (2,2-diphenyl-1-picrylhydrazyl) is
a stable free radical in an aqueous solution. When a plant extract
in solution is exposed to DPPH, the amount of DPPH decreases
according to the antioxidant capacity of the plant extract.
Generally, the more DPPH consumption, the greater concentration of
plant extract components, e.g., polyphenols. The more plant extract
components, e.g., polyphenols, are in solution, the greater their
capacity to make nanometal particles. A DPPH test can be used to
determine which plant extracts, and under what extraction
conditions, yield the highest concentration of plant extract
components, e.g., polyphenols for use in making nanometal
particles.
[0092] The metal ions in solution can be within a range of, for
example, from about 0.001 M to 1.0 M, or about 0.01 to 0.1 M, for
example, up to or at least about 0.001 M, 0.005 M, 0.01 M, 0.05 M,
0.1 M, 0.2 M, 0.3 M, 0.4 M, 0.5 M, 0.6 M, 0.7 M, 0.8 M, 0.9 M, 1.0
M or more. The plant extract can have a concentration of, for
example, from about 5 g/L to about 200 g/L, or about 10 g/L to
about 100 g/L, or about 15 g/L to about 50 g/L, or about 40 g/L to
about 100 g/L, or up to or at least about 0.1, 0.5, 1, 5, 10, 15,
20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160,
170, 180, 190, 200 g/L or more. The metal nanoparticles can be
present in a concentration of from about 0.0006 to about 0.6 M,
about 0.005 to about 0.1 M, or up to or at least about 0.0001,
0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 M, 1
M or more. The nanoparticles can have a diameter of, for example,
from about 1 nm to about 1000 nm, from about 5 nm to about 100 nm,
about 20 nm to about 85 nm, about 10 to about 50 nm, about 40 to
about 100 nm, or up to or at least about 1 nm, 5 nm, 10 nm, 20 nm,
30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm,
140 nm, 160 nm, 180 nm, 200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600
nm, 700 nm, 800 nm, 900 nm, 1000 nm or more.
[0093] The nanoparticles can have various shapes, including
spheres, rods, prisms, hexagonal and mixed prisms, faceted shapes,
wires, and other shapes.
[0094] In some embodiments, the amount of the plant extract used in
the methods disclosed herein is sufficient to convert substantially
all of the dissolved metal ion into nanoparticles. As used herein,
"substantially all" encompasses, e.g., greater than 50%, or at
least about 60%, 70%, 80%, 85%, 90%, 95% or more. Different
meanings of "substantially all" may be apparent from the
context.
[0095] Compositions comprising metal nanoparticles can comprise,
for example, metal nanoparticles and plant extract or components of
plant extracts in solution; metal nanoparticles having a component
of a plant extract, including, without limitation, one or more
phenolic compounds, on its surface; with a component of a plant
extract, including, without limitation, one or more phenolic
compounds, interspersed within the metal nanoparticle. In addition,
compositions comprising metal nanoparticles can also be
compositions from which liquid components have been removed, for
example through filtration or another method, such that the
particles are suitable for, e.g., packaging and shipping; a
concentrated form of a composition comprising nanoparticles in a
liquid; as well as other forms, as would be appreciated by a person
of ordinary skill in the art.
[0096] The metal nanoparticles according to the invention can be
characterized by having a high degree of dispersibility. For
example, the metal nanoparticles can be much easier to handle
because they are less susceptible to aggregation than are metal
nanoparticles prepared using other methods. For example, if the
metal nanoparticles prepared according to embodiments of the
invention are isolated, e.g., through filtration, and then later
redispersed in, for example, water, the particles will be less
susceptible to aggregation upon redispersion than are nanoparticles
prepared using other methods. Nanoparticles prepared according to
other methods often require the application of a capping agent.
Metal nanoparticles prepared according to embodiments of the
invention generally do not require such an additional step.
[0097] As used herein, a "natural solvent or surfactant" is a
substance or composition that can perform, e.g., one or both of two
functions. First, a natural solvent or surfactant can be a
substance or composition that can be used to reduce metal ions in
solution in the preparation of metal nanoparticles, such as
zero-valent metal nanoparticles. Second, a natural solvent or
surfactant can serve to reduce the surface tension between two
phases, for example between an aqueous phase and a non-aqueous
phase that contains, e.g., a contaminant or other substance to be
remediated.
[0098] Nanoparticles, for example isolated nanoparticles, may be
incorporated into any device in which nanoparticles as disclosed
herein may be used.
EXAMPLE 1
Green Synthesis Manufacture of Nanoscale Zero Valent Iron (NZVI) or
Manganese (NZVMn)
[0099] A method according to the invention uses plant extracts
containing reducing agents that are capable of forming
nanoparticles in the presence of dissolved iron species. The
reactions are nearly instantaneous when plant extracts containing
reducing agents are mixed with dissolved iron or manganese species.
The plant reducing agents consist primarily of phenolic compounds
and flavonoids. Examples of dissolved iron are ferric chloride
(FeCl.sub.3), ferrous sulfate (FeSO.sub.4), and ferric nitrate
(Fe(NO.sub.3).sub.3). Examples of dissolved manganese species are
manganese chloride (MnCl.sub.2) and manganous sulfate
(MnSO.sub.4).
[0100] This green synthesis pathway using plant reducing agents can
replace milled or solution-based manufacturing of these materials
with a green synthesized process. This process eliminates toxic
materials used in traditional production of zero valent metal
nanoparticles (i.e., nZV metals). This process also eliminates
toxic materials in waste streams that result from the traditional
production of NZV metals.
[0101] Several sources of dissolved iron can be used to make nZVI
using plant extracts. Ferrous sulfate, ferric chloride, and ferric
nitrate can all be used to form nZVI using this green synthesis
process. Whereas solutions of each of these salts is a clear
liquid, and the plant extracts, e.g., tea extracts, are often light
colored liquids, upon combining the plant extracts with these
dissolved iron sources produces a black solution, evidencing the
formation of iron nanoparticles.
EXAMPLE 2
Synthesis of Metal Nanoparticles with Plant-Based Surfactant and/or
Cosolvent
[0102] A methods according to the invention includes the green
synthesis of metal nanoparticles in the presence of plant-based
cosolvents and surfactants. The plant-based cosolvents and
surfactants can serve to stabilize the metal nanoparticles and to
minimize their agglomeration, and they can also serve as the
reducing agent in the formation of metal nanoparticles. These
plant-based cosolvents and surfactants are naturally derived and
can be biodegradable.
[0103] Examples of plant-based cosolvents and surfactants that can
be used are U.S. FDA Generally Recognized as Safe (GRAS) cosolvents
and surfactants used by VeruTEK for increasing the solubility of
LNAPLs and DNAPLs during oxidation and reduction reactions.
Examples of plant-based cosolvents and surfactants that can be used
include VeruSOL.TM., Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2),
Citrus Burst 3 (CB-3), and EZ-Mulse, manufactured by Florida
Chemical. Any of these can be considered a "natural solvent or
surfactant" as used herein. Citrus Burst 3 includes a surfactant
blend of ethoxylated monoethanolamides of coconut oil fatty acids
and polyoxyethylene castor oil and d-limonene. Examples of
plant-based cosolvents and surfactants that can be used include
Alfoterra 53, biodegradable citrus-based solvents, degradable
surfactants derived from natural oils and products, citrus terpene,
CAS No. 94266-47-4, citrus peels extract (citrus spp.), citrus
extract, Curacao peel extract (Citrus aurantium L.), EINECS No.
304-454-3, FEMA No. 2318, or FEMA No. 2344, terpenes,
citrus-derived terpenes, limonene, d-limonene, castor oil, coca
oil, coconut oil, soy oil, tallow oil, cotton seed oil, and a
naturally occurring plant oil. Examples of plant-based cosolvents
and surfactants that can be used include ALFOTERRA 123-8S,
ALFOTERRA 145-8S, ALFOTERRA L167-7S, ETHOX HCO-5, ETHOX HCO-25,
ETHOX CO-5, ETHOX CO-40, ETHOX ML-5, ETHAL LA-4, AG-6202, AG-6206,
ETHOX CO-36, ETHOX CO-81, ETHOX CO-25, ETHOX TO-16, ETHSORBOX L-20,
ETHOX MO-14, S-MAZ 80K, T-MAZ 60 K 60, TERGITOL L-64, DOWFAX 8390,
ALFOTERRA L167-4S, ALFOTERRA L123-4S, and ALFOTERRA L145-4S. For
example, a composition of surfactant and cosolvent can include at
least one citrus terpene and at least one surfactant. Examples of
plant-based cosolvents and surfactants that can be used include
nonionic surfactants ethoxylated corn oil, ethoxylated palm oil,
ethoxylated soybean oil, ethoxylated castor oil, ethyoxylated
coconut oil, ethoxylated coconut fatty acid, ethoxylated coca oil,
or amidified, ethoxylated coconut fatty acid. Many of these natural
plant oils are US FDA GRAS. Examples of plant-based cosolvents and
surfactants that can be used include ethoxylated castor oil, a
polyoxyethylene (20) castor oil, CAS No. 61791-12-6, PEG
(polyethylene glycol)-10 castor oil, PEG-20 castor oil, PEG-3
castor oil, PEG-40 castor oil, PEG-50 castor oil, PEG-60 castor
oil, POE (polyoxyethylene) (10) castor oil, POE(20) castor oil; POE
(20) castor oil (ether, ester); POE(3) castor oil, POE(40) castor
oil, POE(50) castor oil, POE(60) castor oil, or polyoxyethylene
(20) castor oil (ether, ester). Any of these can be considered a
"natural solvent or surfactant" as used herein.
[0104] Other examples of plant-based cosolvents and surfactants
that can be used include ethoxylated coconut fatty acid, CAS No.
39287-84-8, CAS No. 61791-29-5, CAS No. 68921-12-0, CAS No.
8051-46-5, CAS No. 8051-92-1, .sub.ethoxylated coconut fatty acid,
polyethylene glycol ester of coconut fatty acid, ethoxylated
coconut oil acid, polyethylene glycol monoester of coconut oil
fatty acid, ethoxylated coca fatty acid, PEG-15 cocoate, PEG-5
cocoate, PEG-8 cocoate, polyethylene glycol (15) monococoate,
polyethylene glycol (5) monococoate, polyethylene glycol 400
monococoate, polyethylene glycol monococonut ester, monococonate
polyethylene glycol, monococonut oil fatty acid ester of
polyethylene glycol, polyoxyethylene (15) monococoate,
polyoxyethylene (5) monococoate, or polyoxyethylene (8)
monococoate. An amidified, ethoxylated coconut fatty acid can
include, for example, CAS No. 61791-08-0, ethoxylated reaction
products of coco fatty acids with ethanolamine, PEG-11 cocamide,
PEG-20 cocamide, PEG-3 cocamide, PEG-5 cocamide, PEG-6 cocamide,
PEG-7 cocamide, polyethylene glycol (11) coconut amide,
polyethylene glycol (3) coconut amide, polyethylene glycol (5)
coconut amide, polyethylene glycol (7) coconut amide, polyethylene
glycol 1000 coconut amide, polyethylene glycol 300 coconut amide,
polyoxyethylene (11) coconut amide, polyoxyethylene (20) coconut
amide, polyoxyethylene (3) coconut amide, polyoxyethylene (5)
coconut amide, polyoxyethylene (6) coconut amide, or
polyoxyethylene (7) coconut amide. Any of these can be considered a
"natural solvent or surfactant" as used herein.
[0105] Other examples of plant-based cosolvents and surfactants
that can be used include yucca extract, soapwood extract, and other
natural plants that produce saponins, such as horse chestnuts
(Aesculus), climbing ivy (Hedera), peas (Pisum), cowslip,
(Primula), soapbark (Quillaja), soapwort (Saponaria), sugar beet
(Beta) and balanites (Balanites aegyptiaca). Any of these can be
considered a "natural solvent or surfactant" as used herein. Many
surfactants derived from natural plant oils are known to exhibit
excellent surfactant power, and are biodegradable and do not
degrade into more toxic intermediary compounds.
[0106] In addition to stabilizing green synthesized metal
nanoparticles, such as zero valent metal nanoparticles, e.g., nZVI
particles, against agglomeration and serving as the reducing agent
in the formation of metal nanoparticles, the plant-based cosolvents
and surfactants can promote solubilization of chemicals of concern
such as NAPLs, LNAPLs, and DNAPLs. For example, soil and/or water
contaminated with NAPLs, LNAPLs, and/or DNAPLs can be treated with
a remediation composition that include metal nanoparticles, e.g.,
zero valent metal nanoparticles, and a plant-based natural solvent
or surfactant, in order to remediate the contaminated soil and/or
water by destroying NAPLs, LNAPLs, and/or DNAPLs and decreasing
their concentration.
[0107] Preparation of metal nanoparticles using green synthesis
methods according to some embodiments of the invention has been
demonstrated using a green cosolvent-surfactant system
(VeruSOL.TM.-3), a mixture of U.S. FDA Generally Recognized as Safe
(GRAS) citrus and plant extract-based materials. This enables the
preparation of metal nanoparticles with a food-grade
cosolvent-surfactant system that can be used in the remediation of
highly hydrophobic chemicals, non aqueous phase liquids (NAPLs) and
hydrophobic chemical or biological agents or materials.
[0108] Trials were conducted in which nZVI particles were produced
using ferric chloride and green tea extract with VeruSOL.TM.
concentrations at 2 g/L, 5 g/L, and 10 g/L. A control was prepared
using a mixture of ferric chloride and green tea extract alone. The
presence of VeruSOL.TM.-3 did not impact the formation of nZVI
particles. The presence of VeruSOL.TM.-3 in the ingredients of the
nZVI particles enables the solubilization and desorption of
hydrophobic organic compounds, such as halogenated solvents, PCBs,
and pesticides, and subsequent reduction of these compounds with
nZVI. A further advantage of this new green synthetic process for
preparing nZVI particles is that it can be carried out using
chelated iron. nZVI particles were made using Fe chelated with
ethylene diamine tetraacetic acid (EDTA) and citric acid.
Additionally, VeruSOL.TM.-3 was also used in two of the
experiments, demonstrating that the nZVI particles can be made in
the presence of VeruSOL.TM.-3 and chelated iron. Prior work by Feng
and Hoag (2004) demonstrated that chelates can be used to strip
iron from hydroxides of iron. Chelates can be used according to the
invention to complex with iron naturally present in soils and
groundwater, which can then be used to form nZVI particles.
[0109] Nanoscale zero valent iron particles were manufactured in
the presence of a cosolvent-surfactant mixture, ferric chloride,
and chelated iron species, including Fe(III)-EDTA and
Fe(III)-citric acid. Transmission Electron Microscopy (TEM) images
were made of nZVI particles made with various concentrations of a
cosolvent-surfactant mixture (VeruSOL.TM.-3) ranging in
concentration from 0.0 g/L to 10 g/L (FIGS. 14 through 17). These
figures demonstrate that as the cosolvent-surfactant concentration
increased, the agglomeration of particles decreased, with the
smallest amount of particle agglomeration occurring at the 10 g/L
concentration. Using Fe(III)-EDTA and Fe(III)-citric acid as the
dissolved iron source to make the nZVI particles led to a
significant difference in the size of particles versus those made
when VeruSOL.TM.-3 cosolvent-surfactant was present in solution
during nanoparticle preparation (FIGS. 18-21). One major advantage
of some compounds, compositions and methods of the invention is
that a chelate may be added to soil to extract iron from the soil
and/or groundwater, so that this indigenous source of iron may be
used instead of an added iron source.
[0110] Chelating compounds other than ethylene diamine tetraacetic
acid (EDTA) and citric acid can be used. For example,
ethylenediaminedissuccinate (EDDS) can be used. Some examples of
chelated iron species that can be used are Fe(III)-EDTA ,
Fe(III)-citric acid, Fe(III)-EDDS, Fe(II)-EDTA , Fe(II)-citric
acid, and Fe(II)-EDDS.
EXAMPLE 3
Coating of NZVI, NZVMn, and Bimetallic NZVI, NZVMn
[0111] The use of nanoparticle zero valent iron (nZVI) and
nanoparticle zero valent manganese (nZVMn) can be limited in
environmental applications because they may exhibit a tendency to
aggregate into micron-sized particles, thus losing some of their
surface area to mass benefit. Additionally, nZVI and nZVMn
particles can be highly reactive, and their surfaces can become
quickly passivated and oxidized. In many applications including
those for remediation, there is a need for these particles to exist
and retain reactivity for months or even years. Coating the nZVI
and nZVMn particles can reduce the rapid agglomeration, oxidation,
and passivation of the nanoscale particles.
[0112] In a green approach according to some embodiments of the
invention, bulk quantities of nanocomposites containing, for
example, transition metals such as Cu, Ag, In, and Fe, can be
produced at room temperature using a biodegradable polymer such as
carboxymethyl cellulose (CMC) by reacting respective metal salts
with the sodium salt of CMC in aqueous media. These nanocomposites
exhibit broader decomposition temperatures when compared with
control CMC, and Ag-based CMC nanocomposites exhibit a luminescent
property at longer wavelengths. Noble metals such as Au, Pt, and Pd
do not react at room temperature with aqueous solutions of CMC, but
do so rapidly under microwave irradiation (MW) conditions at
100.degree. C. The nanocomposites obtained at room temperature and
microwave conditions were characterized using scanning electron
microscopy, transmission electron microscopy, infrared
spectroscopy, UV-visible spectroscopy, X-ray mapping,
energy-dispersive analysis, and thermogravimetric analysis. This
environmentally benign approach permits the relatively easy
preparation of noble nanostructures of several shapes, without
using any toxic reducing agents, such as sodium borohydride
(NaBH.sub.4), hydroxylamine hydrochloride, and others. The approach
uses the benign biodegradable polymer CMC and does not require a
separate capping/surfactant agent. Thus, the approach can produce
nanoparticles for use in a wide and varied field of technological
application, for example medicinal and land remediation
applications.
[0113] The green synthesis of zero valent metals and bimetallic
species using plant reducing agents along with biopolymers, with or
without VeruTEK's VeruSOL.TM. green cosolvents and surfactants, can
be used to make hydrophobic organic coated nZVI and nZVMn to
enhance solvophobicity (with and without bimetallic metals). The
coatings may also exhibit amphiphillic properties because of the
presence of surfactant molecules present in the composite matrix.
The coatings and composite structures of these nanometal species
can also exhibit anionic, cationic, or zwitterionic surface charge
properties.
[0114] The first and second dissolved metal ions can be added to
the vessel more or less simultaneously, leading to nanoparticles in
which the first and second metals are interspersed throughout the
metal nanoparticles. Or the first dissolved metal ion can be added
to a vessel first and adding the second dissolved metal ion after a
period of time, for example, of at least about 1 second, 10
seconds, 15 seconds, 30 seconds, or 60 seconds, which generally
leads to nanoparticles in which the first metal is present
primarily in the core of the metal nanoparticle and the second
metal is present primarily in an outer layer around the core of the
metal nanoparticle. As used herein, "simultaneously" encompasses
events that happen at precisely the same time as well as events
that happen somewhat asynchronously, provided they are close enough
in time to substantially accomplish the ends of the procedures
requiring more or less simultaneous events. For example, in a
procedure for preparing bimetallic nanoparticles in which it is
desired that the metals be interspersed throughout the particle,
introduction of the two metal ions will be considered
"simultaneous" if, for example, the procedure produces, or is
capable of producing, bimetallic nanoparticles with the metals
substantially interspersed throughout the particles.
[0115] Bimetallic Fe/Pd nanoparticles can be prepared as follows:
prepare 20 g/L green tea extract by adding 20 grams of green tea to
1 liter of deionized water and bring to 80.degree. C. Let tea cool
to room temperature and vacuum filter through 90 mm glass fiber
filter. Prepare 0.1 M FeCl.sub.3 by dissolving 16.2 g of solid
FeCl.sub.3 in 1 L of deionized water. Prepare palladium chloride
solution in deionized water at appropriate concentration, 0.2 M in
this study. Green tea synthesized nano-scale zero valent iron
(GT-nZVI) is then prepared by adding 0.1 M of FeCl.sub.3 to the 20
g/L filtered green tea in a 2:1 volume ratio, resulting in a 66 mM
Fe concentration in the final GT-nZVI solution. Add appropriate
amount of PdCl.sub.2 to GT-nZVI solution within 30-60 seconds after
FeCl.sub.3 is added to the green tea. Shake. This and/or similar
methods can also be used to prepare nanoparticles comprising other
metals, as well as particles comprising more than two metals.
EXAMPLE 4
Trial Production of nZVI Particles With Green Tea Extract and
Ferric Chloride in the Presence of Carboxy Methyl Cellulose (CMC),
VeruSOL-3.TM., and/or Trichloroethylene (TCE)
[0116] A series of batch tests were conducted to evaluate the
capability of the green synthesis of nZVI using green tea extract
and ferric chloride with the following: a) carboxy methyl cellulose
(CMC); b) VeruSOL.TM.-3; and c) trichloroethylene (TCE). Testing
conditions are shown in Table 2.
TABLE-US-00002 TABLE 2 Compatibility of Carboxy Methyl Cellulose,
VeruSOL .TM.-3 and Trichloroethylene with Green Tea & Ferric
Chloride Synthesized Nanoscale Zero Valent Iron CMC Satu- VS-3 Pure
Green Dyed rated Water (10 g/L) VS-3 FeCl3 Tea-Extract Pure TCE
Test mL mL mL mL mL mL I-1 20 20 I-2 4 20 I-3 20 20 I-4 4 20 I-5 20
20 I-6 4 20 I-7 40 1 I-8 4 24 12 1 I-9 4 24 12 I-10 4 0.4 24 12 1
I-11 4 0.4 24 12 I-12 0.4 24 12 Notes: 1) Reagants- Carboxy methyl
cellulose (CMC) Saturated Water, VeruSOL .TM.-3, FeCl.sub.3, Green
Tea Extract, Dyed Pure TCE 2) Tests Conducted in 40 mL vials 3)
Interfacial Tension and photographs taken 24 hours after a 1 minute
initial mixing period 4) Concentrations of VeruSOL .TM.-3 used
results in 10 g/L concentration in vial 5) 0.1M ferric chloride
used in test 6) Carboxy methyl cellulose used a from a saturated
solution (~3%) of sodium carboxy methyl cellulose (MW-90,000)
[0117] In Test Vials I-1 and I-2, the compatibility of carboxy
methyl cellulose with VeruSOL.TM.-3 was evaluated at two CMC
concentrations. In both cases there were no separate phases
detected when CMC and VeruSOL.TM.-3 were mixed together. In Test
Vials I-2 and I-3, the ability of carboxy methyl cellulose to
chelate the iron in ferric chloride was evaluated. When 4 mL of a
saturated CMC solution was added to 0.1 N ferric chloride,
precipitation of iron was observed for Test Vial I-4. However, when
20 mL of a saturated CMC solution was added to 0.1 N ferric
chloride, there was no precipitation and the ferric chloride was
fully chelated. In Test Vials I-5 and I-6, the compatibility of CMC
and green tea extract were evaluated to determine if there would be
separate phase reaction products. Both of these solutions indicated
no separate phase. In Test Vial I-7, the compatibility of CMC with
pure phase trichloroethylene was evaluated. Visual observation
revealed no apparent reactivity of TCE with CMC. In Test Vials I-8
and I-9, the synthesis of nZVI using ferric chloride and green tea
extract was evaluated in the presence of CMC (I-9) and in the
presence of CMC and pure phase TCE (I-8). There was no apparent
impact on the ability to form nZVI particles when CMC and CMC plus
TCE were present. Test vials clearly exhibited a layer of TCE under
the settled nZVI.
[0118] In Test Vial 10, the synthesis of nZVI using ferric chloride
and green tea was evaluated in the presence of CMC, TCE, and
VeruSOL.TM.-3. The appearance of this test was similar to Test Vial
I-8 (similar conditions to Test Vial I-10 but without TCE);
however, the TCE appeared to attach to the glass walls of the Test
Vial. In Test Vials I-11 and I-12, the effects were determined on
the addition of VeruSOL.TM.-3 on the synthesis of nZVI using ferric
chloride and green tea extract in the presence of CMC (Vial I-11)
and absence of CMC (Vial I-12). In both cases the addition of
VeruSOL.TM.-3 stabilized the nZVI and inhibited much of the
agglomeration and settling observed when VeruSOL.TM.-3 was not
added during the synthesis of nZVI using ferric chloride and green
tea extract.
[0119] Hoag and Collins (Patent pending; U.S. Ser. No. 12/068,653)
teach that VeruSOL.TM.-3, a mixture of d-limonene and nonionic
surfactants consisting of ethoxylated plant oils, can be used to
dissolve a variety of organic liquids, including TCE. The test
results clearly indicate that nZVI can be synthesized using ferric
chloride and green tea extract in the presence of TCE without any
impact on particle formation. Therefore, nZVI can be made using
this green synthesis process in the presence of VeruTEK's
VeruSOL.TM.-3 to enable controlled dissolution of Non Aqueous Phase
Liquids (NAPL). Additionally, since nZVI can be made in situ, as
demonstrated in the soil column test results, nZVI can also be
manufactured in situ in the presence of pure phase TCE.
EXAMPLE 5
In Situ Formation of Metal Nanoparticles
[0120] A method according to the invention was used to produce
nanoscale zero valent iron particles (nZVI) in soil columns, as a
simulation of in situ formation of nanoscale iron particles in
soil. Two column experiments were conducted to evaluate the
potential for in situ generation of nZVI using Fe(NO.sub.3).sub.3
and either green tea extract or lemon balm extract. Two stock
solutions were each injected in an upflow mode into soil columns
packed with ASTM 20/30 sand with the dimension of 300 cm long by 30
cm diameter. For Column 2, green tea extract and 0.1 M
Fe(NO.sub.3).sub.3 were each simultaneously injected at flowrates
each at 0.15 mL/min for a total injected flowrate of 0.30
mL/min.
[0121] The green tea extract was made as follows: 200 mL of
deionized water were heated in a beaker to a temperature of
82.degree. C. and 4.01 grams of Chunmee green tea was added. The
beaker was covered with aluminum foil and the tea was heated in the
water for 5 minutes. After 5 minutes, the beaker was removed from
the heat and the tea was allowed to settle for 1 hour and return to
25.degree. C. The tea extract supernatant was then removed from the
beaker and either immediately used or stored at 4.degree. C. for
later use. The Lemon Balm Extract was made using a similar
procedure.
[0122] The initial formation of nZVI in the bottom (inlet) of the
soil column was observed in the bottom of Column 2, as black in an
otherwise light-colored liquid. Effluent from Column 2 was
collected and sampled for electrolytic conductivity and was
visually observed. Sample number 4 was collected between effluent
volumes of from 117 mL to 150 mL in a 40 mL sample vial and
represented approximately 0.56 pore volumes of flow through the
column. Sample number 5 was collected between effluent volume from
150 mL to 200 mL in a 60 mL sample vial and represented
approximately 0.74 pore volumes of flow through the column. Sample
number 6 was collected between effluent volumes of from 200 mL to
259 mL in a 60 mL sample vial and represented approximately 0.96
pore volumes of flow through the column. The electrolytic
conductivity values for Samples 4, 5, and 6 were 0.86 mS/cm, 2.27
mS/cm, and 17.4 mS/cm, respectively. An examination of the effluent
samples demonstrated that the nZVI began eluting from the column
between Samples 4 and 5. A comparison of the Lemon Balm Extract and
0.1 M Fe(NO.sub.3).sub.3 Column (Column 1) to a control column (no
Lemon Balm Extract or ferric nitrate) clearly showed the
accumulation of nZVI in the column, but the nZVI continued to elute
from the column as long as the test runs were conducted. The
electrolytic conductivity of the Column 1 (Lemon Balm Extract and
0.1 M Fe(NO.sub.3).sub.3) effluent is shown in FIG. 1. It is
evident that the nZVI eluted from the column and continued to elute
after breakthrough. The same trend is evident in Column 2 (Green
Tea Extract and 0.1 M Fe(NO.sub.3).sub.3), as is shown in FIG.
2.
EXAMPLE 6
DPPH Stable Radical Method For Screening of Plant Extracts For Use
in Synthesis of Metal Nanoparticles
[0123] A 2,2-diphenyl-1-picrylhydrazyl (DPPH) stable radical method
for analysis of radical scavenging properties related to
antioxidant activity was used to screen plant extract for potential
use in the manufacture of zero valent nanoparticles. This method
was used to determine and optimize the amount of ferric iron added
to a given plant extract for the formation of zero valent
nanoparticles. One optimization goal in the manufacture of
nanometal particles using plant extracts is to determine how much
ferric iron (or other metal) can be added to a given plant extract
to ensure complete conversion of ferric iron to zero valent iron.
This DPPH screening method also can be used with metals other than
iron and with plant extracts other than green tea for the
manufacture of nanometals using plant extracts.
[0124] The experimental design is presented in Table 3.
TABLE-US-00003 TABLE 3 DPPH Stable Radical Consumption by Plant
Extracts Before and After Reaction with Ferric Chloride to
Manufacture Nanoscale Zero Valent Iron Particles Absorbance of
Treated Samples at Test Test Reaction Matrix 517 nm Observations
Conc, g/L 1 L mL DI Water + 3 mL EtOH + 1 mL 0.955 Purple DPPH Soln
2 1 mL 200x, 2.5 g/L Tea Extract + 3 mL 0.836 Purple 2.5 EtOH4 + 1
mL DPPH Soln 3 1 mL 200x, 5 g/L Tea Extract + 3 mL 0.793 Purple 5
EtOH4 + 1 mL DPPH Soln 4 1 mL 200x, 10 g/L Tea Extract + 3 mL 0.637
Purple 10 EtOH4 + 1 mL DPPH Soln 5 I mL 200x, 20gfL Tea Extmct + 3
mL 0.593 Light Purple 20 EtOH4 + 1 mL DPPH Soln 6 1 mL 200x, 40 g/L
Tea Extract + 3 mL 0.072 Tea 40 EtOH4 + 1 mL DPPH Soln 7 1 mL 200x,
2.5 g/L Tea Extract/NZV1 + 0.86 Purple 2.5 3 mL EtOH4 + 1 mL DPPH
Soln 8 1 mL 200x, 5 g/L Tea Extract/NZVI + 0.858 Purple 5 3 mL
EtOH4 + 1 mL DPPH Soln 9 1 mL 200x, 10 g/L Tea Extract/NZVI + 0.802
Purple 10 3 mL EtOH4 + 1 mL DPPH Soln 10 1 mL 200x, 20 g/L Tea
Extract/NZVI + 0.774 Purple 20 3 mL EtOH4 + 1 mL DPPH Soln 11 1 mL
200x, 40 g/L Tea Exttact/NZVI + 0.527 Purple pink 40 3 mL EtOH4 + 1
mL DPPH Soln Experimental Procedure: 1) DPPH (500 uM) was dissolved
in pure ethanol (96%). The radical stock solution was prepared
fresh daily. 2) The DPPH solution (1 mL)was added to 1 mL of sample
extract with 3 mL of ethanol. 3) The mixture was shaken vigorously
for 10 min and allowed to stand at room temperature in the dark for
another 20 min. 4) A decrease in absorbance of the resulting
solution (the result of consumption of the radical scavenger) was
measured at 517 nm.
[0125] Tests 1 though 5 in Table 2 were used to determine the
effects of increasing concentrations of dry green tea used to make
tea extract in heated water on the spectroscopic absorbance of the
DPPH radical. The results of tests 1 through 5 are represented by
the lower line of best fit in FIG. 13, demonstrating a linear
relationship between dry green tea concentration (used to make the
tea extract) and DPPH absorbance at 517 run. The green tea extract
was diluted by a factor of 200 to obtain usable absorbance
measurements in a linear range. The same green tea extracts used in
tests 1 through 5 were then added to ferric chloride to make zero
valent iron nanoparticles. A ratio of 2:1 (v/v) of 0.1M FeCl.sub.3
to tea extract was used to make the zero valent iron nanoparticles
used in tests 7 through 11. The DPPH absorbance of the solution
following the formation of nZVI particles was considerably higher
than with the original green tea extracts alone, reflecting that
some of the compounds in the tea extract responsible for
consumption of the DPPH free radical were consumed in the formation
of the nZVI particles. This is evident by examination of the upper
line of best fit in FIG. 13. The difference between the two lines
represents the net consumption of DPPH free radical absorbance when
nanometal particles are manufactured. Polyphenolic compounds and
other compounds in the tea extract are consumed during the
production of metal nanoparticles, as evidenced by the difference
between the two lines. The net consumption can be used to run
successive dosing tests for the concentration ratio of the metal
salt solutions and the plant extract, thereby enabling a
relationship to be derived between DDPH absorption and metal salt
added. This relationship can be used to establish the optimum dose
of plant extract and metal salt solution to use the plant extract
to the maximum extent in the formation of metal nanoparticles.
EXAMPLE 7
Green Synthesis Manufacture of Noble Metal Nanoparticles at Room
Temperature
[0126] A method according to some embodiments of the invention
represents a green approach that generates bulk quantities of
nanocrystals of noble metal, such as silver (Ag) and palladium
(Pd), using a plant extract, such as coffee and tea extract, at
room temperature. This single-pot method uses no surfactant,
capping agent, and/or template. The obtained nanoparticles have a
diameter size of from about 20 nm to about 60 nm and are
crystallized in face centered cubic symmetry. The method may be
used to produce nanoparticles of other metals, such as other noble
metals, e.g., gold (Au) and platinum (Pt).
[0127] To produce the coffee extract, 400 mg of coffee powder (Tata
Bru coffee powder 99%) was dissolved in 50 mL of water. 2 ml of 0.1
N AgNO.sub.3 (AgNO.sub.3, Aldrich, 99%) was mixed with 10 ml of the
coffee extract and shaken to ensure thorough mixing. The reaction
mixture was allowed to settle at room temperature.
[0128] 2 ml of 0.1 N PdCl.sub.2 (PdCl2, Aldrich, 99%) was mixed
with 10 ml of the coffee extract and shaken to ensure thorough
mixing. The reaction mixture was allowed to settle at room
temperature.
[0129] To produce the tea extract, 1 gm of tea powder (Red label
from Tata, India Ltd. 99%) was boiled in 50 ml of water and
filtered through a 25 .mu.m Teflon filter. 2 ml of 0.1 N AgNO.sub.3
(AgNO.sub.3, Aldrich, 99%) was mixed with 10 ml of the tea extract
and shaken to ensure thorough mixing. The reaction mixture was
allowed to settle at room temperature.
[0130] 2 ml of 0.1 N PdCl.sub.2 (PdCl.sub.2, Aldrich, 99%) was
mixed with 10 ml of the tea extract and shaken to ensure thorough
mixing. The reaction mixture was allowed to settle at room
temperature.
[0131] To evaluate the effect of the source of the coffee or tea
extract on the morphology of the Ag and Pd nanoparticles prepared,
several experiments similar to those described above were carried
out with coffee and tea extracts from various sources. The results
are shown in Table 4.
TABLE-US-00004 TABLE 4 Various brands of tea/coffee used to
generate nanoparticles. Item Brand Names Shape Size 1 Sanka .TM.
coffee faceted ~100 nm 2 Bigelow .TM. tea spherical ~20 nm 3
Luzianne .TM. tea spherical ~100 nm 4 Starbucks .TM. coffee
spherical ~10 nm 5 Folgers .TM. coffee spherical ~10 nm 6 Lipton
.TM. tea spherical ~20-30 nm
[0132] 0.1 mL of the products containing nanoparticles was
dispersed with 5 mL distilled water to prepare samples for
transmission electron microscopy (TEM) and scanning electron
microscopy (SEM) analysis. TEM grids were prepared by placing 1
.mu.L of the particle solution on a carbon-coated copper grid and
drying at room temperature, and UV-visible spectrum measurements
were taken. To obtain better SEM images, the product was drop-cast
on carbon tape and allowed to dry; a thin layer of gold was coated
on the surface to make it conducting. TEM was performed with a
JEOL-1200 EX microscope operated at 120 kV. SEM was carried out
with a field-emission microscope (Leo, 1530 VP) operated at an
accelerating voltage of 20 kV. X-ray diffraction (XRD) patterns
were obtained from a Scintag X-ray diffractometer at a 2 theta
range of 2-600 using CuK.alpha. radiation. Open-circuit voltage
potentials were obtained using 1 M NaCl with reference to saturated
calomel electrode (SCE).
[0133] Various shapes and sizes for Ag and Pd nanoparticles using
coffee and tea extract were observed. Drop-coated films of Ag and
Pd nanoparticles were prepared by room temperature aqueous solution
evaporation on carbon-coated copper grids and analyzed by TEM (FIG.
3a-d). At low magnification, a number of highly polydisperse Ag
nanoparticles possessing a variety of shapes were observed (FIG.
3a). The TEM image shows that Ag nanoparticles were well-separated
from each other with an apparently uniform inter-particle
separation. This indicates that the Ag nanoparticles were capped by
organic molecules, such as caffeine, and at higher magnifications
it can be seen clearly (FIG. 3b). In the case of Pd nanoparticles,
the sizes seemed to be smaller than Ag nanoparticles and the
inter-particle distance was uniformly separated and well aligned
(FIG. 3c-d).
[0134] The particles sizes ranged from about 20 nm to about 60 nm,
and the particles were well-separated from each other. The
polyphenols acted as a reducing agent as well as a capping agent.
The control experiments carried out with pure catechin yielded
tennis-ball-like structures for Au and Ag (FIG. 3 and FIG. 11).
However, pure caffeine yielded wire-like structures for Au (FIG.
12) and reaction with AgNO.sub.3 is very slow with less yield. This
approach was carried out for nanoparticles produced with coffee and
tea from various sources (Table 4), and corresponding TEM images
are shown in FIGS. 4 and 5. The Ag and Pd nanoparticles were mostly
spherical and had sizes ranging from as low as about 5 nm to about
100 nm, depending upon the source of coffee or tea extract used
(see FIG. 4 and FIG. 5).
[0135] The control experiments carried out with pure catechin
showed spherical-ball-like structures for Ag and Pd, as shown in
FIG. 6.
[0136] The formation mechanism of Ag and Pd was studied using UV
spectroscopy, which was found to be a useful technique for the
analysis of nanoparticle formation over time. As illustrated in
FIG. 7, a surface plasmon peak located at .about.460 nm was
observed for the Ag nanoparticles after 2 hours of reaction (curve
(f) prepared from tea extract. A strong absorption peak was
observed at .about.340 nm corresponding to the absorption of
polyphenol compounds present in the tea.
[0137] The UV spectra of Ag and Pd nanoparticles prepared from
coffee and tea extracts are shown in FIG. 8. The generation of
strong but broad-surface plasmon peaks has been observed in the
case of various metal nanoparticles over a wide range of particle
sizes, e.g., from about 200 to about 1200 nm.
[0138] The reduction potential of caffeine is .about.0.3 V vs. SCE
(see FIG. 9) which is sufficient to reduce metals viz. Pd
(reduction potential 0.915 V vs. SCE), Ag (reduction potential 0.80
V vs. SCE), and also for reducing Au.sup.+3 to Au.sup.0 (reduction
potential is 1.50 V vs. SCE) and Pt (reduction potential 1.20 V vs.
SCE). The formation of Ag and Pd nanoparticles with caffeine is
understood to take place via the following steps:
[0139] complexation with Ag and Pd metal salts
[0140] simultaneous reduction of Ag and Pd metal and formation of
capping with oxidized caffeine.
[0141] FIG. 10a-d shows the XRD patterns of Ag and Pd nanoparticles
obtained from coffee and tea extract, respectively, from an aqueous
solution drop coated film on glass plate. From the XRD patterns,
prominent Bragg reflections at 28 values of 38.3 and 42.6 were
observed which correspond to the (111) and (200) Bragg reflections
of face centered cubic (fcc) Ag nanoparticles (FIG. 10a-b). See,
e.g., Y. Sun and Y. Xia, Science, 2002, 298, 2176. However, in the
case of Pd nanoparticles, layered structures of caffeine remained
with a well-developed progression of intense reflections, which are
successive orders of diffraction with a large d spacing (see FIG.
10c-d). See, L. M. Juliano and R. R. Griffiths, Psychopharmacology,
2004, 176, 1. The diffraction patterns can be interpreted to depict
a crystal structure in which Pd and caffeine molecules occur in
regularly stacked layers with a large interlayer lattice dimension,
and relatively small distances in the interlayer two-dimensional
lattice. The presence of narrow interlayer reflections indicates
that there is crystallographic registry of layers.
EXAMPLE 8
Green Synthesis of Nanoscale Bimetallic Zero Valent Metals
[0142] Methods according to the invention, similar to those
described above, can be used to manufacture bimetallic nZV
materials. For example, bimetallic metal nZV materials can be made
by adding additional metal salts to the base metal salt used. In
the case of nZV iron, palladium, nickel, silver, and other metals
can be used to develop bimetallic nanoparticles. The uses of these
materials can be substantially similar to those described above.
The methods described herein can also be used to prepare nZV
particles comprising three or more metals, as would be appreciated
by a person of ordinary skill in the art.
[0143] The preparation of bimetallic nanoparticles from metal salts
is generally carried out using one of two methods: 1) co-reduction
and 2) successive reduction of two metal salts. Successive
reduction can be carried out to prepare core-shell structured
bimetallic nanoparticles. Co-reduction is the simpler preparative
method for bimetallic nanoparticles. In this process, first the
metal ions coordinate with green tea/coffee extract, and then
reduction occurs. Addition of a second metal salt and subsequent
reduction with excess stabilizing green tea/coffee extract results
in the formation of core-shell structure. The formation of
core-shell structure will depend upon the metal salts used and the
reducing/stabilizing agent used in the preparation.
[0144] The plant extracts according to the invention may be aqueous
plant extracts from a wide variety of plant materials, obtained in
water from cold to boiling temperatures, with or without mild
surfactants and with or without cosolvents, e.g., ethanol or
d-limonene, to facilitate extraction. The extracts may be crude, or
may be further purified, as with catechins. The extracts generally
exhibit high anti-oxidant and/or polyphenol concentrations
sufficient to form nanoparticles of metal according to the
invention.
EXAMPLE 9
Degradation of Bromothymol Blue by "Greener" Nano-Scale Zerovalent
Iron Synthesized Using Tea Polyphenols
[0145] The focus of this study is to compare the degradation of
bromothymol blue, a model contaminant, by green tea synthesized
nano-scale zero valent iron (GT-nZVI), Fe-EDTA (Fe-ethylenediamine
tetraacetate), and Fe-EDDS (Fe-(S,S)-ethylene
diamine-N,N')-disuccinic Acid) catalyzed hydrogen peroxide. The
degradation of the model contaminant is monitored, allowing for the
determination of rate constants at various concentrations of iron.
The following green single-step synthesis of iron nanoparticles
using tea (Camellia sinensis) polyphenols uses no additional
surfactants/polymers as capping or reducing agents. The tea extract
(polyphenols) used in this study functions both as a reducing and
capping agent for Fe. It has additional advantages due to its high
water solubility, low toxicity, and biodegradability. The reaction
between polyphenols and ferric nitrate occurs within a few minutes
at room temperature, as indicated by color changes from pale yellow
to dark greenish/black in the formation of iron nanoparticles.
[0146] Bromothymol blue, a commonly deployed pH indicator, is used
here as a model contaminant for free radical reactions, due to its
stability in the presence of H.sub.2O.sub.2 and its absorbance in
the visible range at pH 6. The concentration of bromothymol blue is
conveniently monitored using ultraviolet-visible (UV-Vis)
spectroscopy during treatment with iron-catalyzed H.sub.2O.sub.2.
Various concentrations of iron are tested to allow for the
determination of initial rate constants for the different iron
sources.
##STR00001##
[0147] This new synthetic method is an extremely simple green
approach that generates bulk quantities of relatively stable
nanocrystals of iron (Fe) using tea extract at room
temperature.
[0148] Green tea extract was prepared by heating 20 g/L green tea
to 80.degree. C. followed by vacuum filtration. A solution of 0.1M
FeCl.sub.3 was prepared by dissolving 16.2 g of solid FeCl.sub.3
(Acros Organics) in 1 L of deionized water. Green tea synthesized
nano-scale zero valent iron (GT-nZVI) was then prepared by adding
0.1 M FeCl.sub.3 to 20 g/L green tea in a 2:1 volume ratio,
resulting in a 66 mM Fe concentration in the final GT-nZVI
solution.
[0149] Solutions of Fe-EDTA and Fe-EDDS were prepared at 350 mg/L
as iron. Fe-EDTA was prepared by dissolving 0.2378 g of
ethylenediamine tetraacetate (EDTA) (Fisher) in deionized water
followed by 0.1737 g of FeSO.sub.4 (Fisher). H.sub.2SO.sub.4 was
then added to the solution, drop-wise, until it turned a pale green
color. The solution was then brought to a total volume of 100 mL
with deionized water. Fe-EDDS was prepared in the same manner using
0.2239 g of (S,S)-ethylene diamine-N,N'-disuccinic Acid (EDDS) and
0.1737 g of FeSO.sub.4. An unstabilized 30% H.sub.2O.sub.2 solution
was obtained from Fisher. A 500 ppm bromothymol blue solution was
prepared by dissolving 50 mg bromothymol blue (Aldrich) in 100 mL
of deionized water.
[0150] The reaction vessel used for all experiments was a quartz
cuvette. Ultraviolet-visible absorbance measurements were made
throughout the experiment with a photodiode array scanning
spectrophotometer (Beckman). Three iron sources were tested at
various concentrations as a catalyst for the formation of
H.sub.2O.sub.2 free radicals: GT-nZVI, Fe-EDTA, and Fe-EDDS. Before
each trial, a blank was read which included 3 mL deionized water
with the appropriate iron source and concentration. A clean cuvette
was then loaded with 3 mL of 500 ppm bromothymol blue and
H.sub.2O.sub.2 was added. With the cuvette in the
spectrophotometer, the iron source was added to the solution and
quickly mixed with the pipette. Scans were started immediately
after the injection of the iron source and the solution was left
untouched until completion.
[0151] The first series of experiments examined the degradation of
bromothymol blue with GT-nZVI catalyzed H.sub.2O.sub.2 at various
nano-scale iron concentrations. The second and third series of
experiments examined the degradation of bromothymol blue with
Fe-EDTA catalyzed H.sub.2O.sub.2 and Fe-EDDS catalyzed
H.sub.2O.sub.2, respectively. A 2% H.sub.2O.sub.2 concentration was
used for all experiments. Experiments were conducted using GT-nZVI
concentrations at 0.03 mM, 0.06 mM, 0.12 mM, and 0.33 mM as Fe.
Similarly, experiments using. Fe-EDTA and Fe-EDDS had
concentrations at 0.12 mM, 0.33 mM, and 0.5 mM; an additional
concentration of 0.66 mM as Fe was also used for Fe-EDDS.
[0152] The reduction potential of caffeine is 0.3 V vs. SCE which
is sufficient to reduce metals viz. Fe (reduction potential -0.44 V
vs. SCE). The formation of Fe nanoparticles with
caffeine/polyphenols is understood to occur via the following
steps: (1) complexation with Fe salts, (2) simultaneous reduction
of Fe (+III) capping with oxidized polyphenols/caffeine. The
reduction of Fe was confirmed using UV spectra and is shown in FIG.
22. The blank extract has an absorption beginning at 500 nm which
is similar to the control Fe(NO.sub.3).sub.3 solutions. The
reaction between Fe(NO.sub.3).sub.3 and tea extract was
instantaneous and the color of the reaction mixture changed from
yellow to dark brown as shown in the inset of FIG. 22. This general
approach was explored using other common salts of iron as the
source of dissolved Fe, namely FeCl.sub.3, FeSO.sub.4, and FeEDTA.
A variety of additional plant sources of polphenols have also been
used including several herbs including lemon balm (Melissa
officinalis), and parsley (Crispum crispum) and grains, for example
sorghum bran (Sorghum spp.). After the reaction, the UV spectra had
broad absorption at a higher wavelength and there was no sharp
absorption at lower wavelengths as occurred in the controls.
Representative XRD pattern of the iron nanoparticles is shown in
FIG. 23 and the pattern was compared with JCPDS pattern
00-050-1275. The highest intensity plane (102) is well-matched with
the reported pattern. However, other additional reflections were
very weak, possibly due to preferred orientation of the iron
nanoparticles. Some small additional peaks were noted, which may
correspond to impurities originating from the tea extract.
[0153] These iron nanoparticles were tested as a catalyst for the
oxidation of bromothymol blue. The bromothymol has an absorption in
the visible region which is concentration-dependent (see FIGS. 24
and 33).
[0154] Initial bromothymol blue concentration was 500 mg/L and with
2% hydrogen peroxide, bromothymol blue did not undergo any
degradationkatalysis, confirming the lack of a direct oxidation
pathway by peroxide. A similar bromothymol blue concentration was
tested using different iron concentrations for peroxide catalysis
and is shown in FIGS. 25 and 26. The maximum absorbance, at 431 nm,
is at time zero and decreases with every scan over time,
demonstrating the free radical oxidation of bromothymol blue.
Higher iron concentrations accelerated the degradation of
bromothymol blue.
[0155] The changes in the concentration of the bromothymol blue (pH
6) at different time intervals is illustrated in FIG. 27. Graphs
(a) through (e) represent GT-nZVI concentrations in 2% hydrogen
peroxide, as set forth in Table 5. The time series graphs
demonstrate how bromothymol blue degrades over time in the presence
of 2% H.sub.2O.sub.2 and 0.03, 0.06, 0.12 and 0.33 mM GT-nZVI
respectively. Experimental rate constants of bromothymol blue
oxidation are obtained by monitoring the change in absorbance at
431.
[0156] The fastest degradation of bromothymol blue by catalyzed
H.sub.2O.sub.2 occurred with Fe GT-nZVI at a concentration of 0.33
mM. A linear relationship is determined between the natural log of
bromothymol blue concentration (In[BTB]) and time, indicating a
first order reaction with respect to bromothymol blue
concentration, as shown in FIG. 28. The rate constants increase
between 0.0062 min.sup.-1 at 0.03 mM GT-nZVI, to 0.1448 min.sup.-1
at 0.33 mM GT-nZVI (Table 5).
TABLE-US-00005 TABLE 5 Initial rates of decomposition of
bromothymol blue with GT-nZVI catalyzed H.sub.2O.sub.2. Graph
GT-nZVI (mM as Fe) Rate (min.sup.-1) R.sup.2 (a) 0 -0.0011 0.4376
(b) 0.03 0.0062 0.9842 (c) 0.06 0.0152 0.9859 (d) 0.12 0.0449
0.9938 (e) 0.33 0.1448 0.9925
[0157] FIG. 29 illustrates the linear relationship between the
initial rate constants and GT-nZVI concentrations. The highly
linear relationship of the initial bromothymol blue oxidative rate
constants (R.sup.2=0.9989) for a 2% hydrogen peroxide concentration
over a range of Fe concentrations (0.03 mM to 0.33 mM) demonstrates
the activity of these heterogeneous catalysts, with initial rate
constants varying from 0.0062 to 0.1448.sup.-1.
[0158] The degradation of bromothymol blue over time with Fe-EDTA
and Fe-EDDS catalyzed 2% H.sub.2O.sub.2, at four different Fe
concentrations is shown in FIG. 30. FIG. 30 presents the
degradation of bromothymol blue concentration over time with
Fe-EDTA (graph (a)) and Fe-EDDS (graph (b)) catalyzed
H.sub.2O.sub.2. (a) bromothymol blue treated with 0.12 mM Fe
catalyzed HP (2%), (b) bromothymol blue treated with 0.33 mM as Fe
catalyzed HP (2%), (c) brornothymol blue treated with 0.50 mM as Fe
catalyzed HP (2%), (d) bromothymol blue treated with 0.66 mM as Fe
(Fe-EDDS only) catalyzed HP (2%).
[0159] Initial rate constants for these reactions were obtained by
plotting In[BTB] as a function of Fe-EDTA or -EDDS concentrations
(as Fe). Over the range of Fe concentrations tested, the results
suggest a decrease in the rate of bromothymol blue degradation with
increasing amounts of Fe, as shown in FIG. 31. Because EDTA and
EDDS have the ability to stabilize H.sub.2O.sub.2, increasing
concentrations of Fe-EDTA or -EDDS result in an increase in the
stabilization of H.sub.2O.sub.2. This increase in H.sub.2O.sub.2
stabilization slows the decomposition of H.sub.2O.sub.2 and the
production of hydroxyl radicals, ultimately slowing the oxidation
of bromothymol blue (Tables 6 and 7).
TABLE-US-00006 TABLE 6 Initial rates of decomposition of
bromothymol blue with Fe-EDTA. Sl No. Fe-EDTA (mM as Fe) Rate
(min.sup.-1) R.sup.2 (a) 0.12 0.041 0.96 (b) 0.33 0.0038 0.9104 (c)
0.5 0.0035 0.9502
TABLE-US-00007 TABLE 7 Initial rates of decomposition of
bromothymol blue Fe-EDDS catalyzed H.sub.2O.sub.2. Sl No. Fe-EDDS
(mM as Fe) Rate (min.sup.-1) R.sup.2 (a) 0.12 0.0146 0.9742 (b)
0.33 0.0148 0.9375 (c) 0.5 0.0097 0.9936 (d) 0.66 0.0103 0.9502
[0160] FIG. 32 shows the relationship between initial rate
constants and the concentration (as Fe) of Fe-EDTA and Fe-EDDS.
Initial rate constants for the Fe-EDTA catalyzed peroxide varied
from 0.0035 to 0.0041 min.sup.-1 and Fe-EDDS initial rate constants
varied from 0.0097 to 0.0148 min.sup.-1. It is apparent that the
initial rate constants for the oxidation of the bromothymol blue
were much greater with the GT-nZVI catalyst than with Fe-EDTA or
Fe-EDDS. At a Fe concentration of 0.33 mM and a hydrogen peroxide
concentration of 0.33 mM, the initial rate constants for
bromothymol blue oxidation were 0.1447, 0.0038 and 0.0148 for the
catalysts GT-nZVI, FeEDTA and FeEDDS, respectively. The comparative
rate constants for bromothymol blue oxidation using a GT-nZVI
catalyst were more than an order of magnitude greater than with
Fe-EDTA and Fe-EDDS.
EXAMPLE 10
Green Synthesis of Au Nanostructures at Room Temperature Using
Biodegradable Plant Surfactants
[0161] The following describes a convenient one-step
room-temperature green synthesis of gold (Au) nanostructures with
different morphologies and sizes (i.e., spheres, prisms, and
hexagonal structures), which are readily prepared from inexpensive
starting materials including plant-based naturally-occurring
biodegradable surfactants and cosolvents in water without using any
additional capping or reducing reagent. The sizes vary from
nanometer to micron scale level depending on the plant extract used
for the preparation. This synthesis concept can enable the
fine-tuning of material responses to magnetic, electrical, optical,
and mechanical stimuli.
[0162] Chloroauric acid tetrahydrate (HAuCl.sub.4.4H2O) and methyl
ammonium bromide was obtained from Aldrich chemical company. Plant
extract were obtained from VeruTEK.TM. Technologies, Inc. of
Bloomfield, Conn. VeruSOL-3.TM. is a mixture of d-limonene and
plant-based surfactants. VeruSOL-10.TM., VeruSOL-11.TM. and
VeruSOL-12.TM. are individual plant-based surfactants derived from
coconut and castor oils. All of the chemicals were analytical grade
and used without further purification. Doubly distilled water was
used throughout the experiments.
[0163] Different concentrations of HAuCl.sub.4 solutions were added
to the solution of plant extracts at room temperature. This mixture
was gently mixed, followed by rapid inversion mixing for 2 minutes.
The composition of the reaction mixtures are shown in Table 8.
Samples for UV spectroscopy measurements were reaction mixtures
dispersed in distilled water. To obtain better SEM images, the
product was drop-casted on carbon tape and allowed to dry.
Transmission electron microscopy (TEM) was performed with a
JEOL-1200 EX II microscope operated at 120 kV. Scanning electron
microscopy (SEM) was carried out with a field-emission microscope
(JEOL 8400 LV) operated at an accelerating voltage of 20 kV.
Panalytical X-pert diffractometer with a copper Ka source was used
to identify crystalline phases of the lead precipitates. The tube
was operated at 45 kV and 40 mA for the analyses. Scans were
performed over a 2-theta ranging from 5 to 70.degree. with a step
of 0.02.degree. and a one-second count time at each step. Pattern
analysis was performed by following ASTM procedures using the
computer software Jade (Versions 8, Materials Data, Inc.), with
reference to the 1995-2002 ICDD PDF-2 data files (International
Center for Diffraction Data, Newtown Square, Pa.). UV spectra were
recorded using Varian UV-visible spectrometer (Model Cary 50
Conc).
TABLE-US-00008 TABLE 8 Different compositions of reaction mixture
Entry Composition Code 1 VeruSOL-3 .TM. 2 mL + 4 mL HAuCl.sub.4
Au-1 2 D-limonene 2 mL + 4 mL HAuCl.sub.4 Au-2 3 VeruSOL-12 .TM. 2
mL + 4 mL HAuCl.sub.4 Au-3 4 VeruSOL-10 .TM. 2 mL + 4 mL
HAuCl.sub.4 Au-4 5 VeruSOL-11 .TM. 2 mL + 4 mL HAuCl.sub.4 Au-5 6
VeruSOL-3 .TM. 2 mL + 4 mL HAuCl.sub.4 + 10 H.sub.2O Au-6 7
D-limonene 2 mL + 4 mL HAuCl.sub.4 + 10 H.sub.2O Au-7 8 VeruSOL-12
.TM. + 4 mL HAuCl.sub.4 + 10 H.sub.2O Au-8 9 VeruSOL-10 .TM. + 4 mL
HAuCl.sub.4 + 10 H.sub.2O Au-9 10 VeruSOL-11 .TM. + 4 mL
HAuCl.sub.4 + 10 H.sub.2O Au-10 11 VeruSOL-3 .TM. 1 mL + 10 mL
HAuCl.sub.4 Au-11 12 D-limonene 1 mL + 10 mL HAuCl.sub.4 Au-12 13
VeruSOL-12 .TM. 1 mL + 10 mL HAuCl.sub.4 Au-13 14 VeruSOL-10 .TM. 1
mL + 10 mL HAuCl.sub.4 Au-14 15 VeruSOL-11 .TM. 1 mL + 10 mL
HAuCl.sub.4 Au-15
[0164] Formation of gold nanostructures was achieved at room
temperature, followed by the in situ measurement by the UV-vis
spectra. The reaction solution containing plant extracts obtained
from VeruTEK Technologies, Inc. of Bloomfield, Conn.
HAuCl.sub.44H.sub.2O was introduced into a quartz cell immediately
after mixing, and the UV-vis spectra were recorded at different
time intervals. The color of the solution changed gradually to
light pink within 15 min after mixing. However, some of the samples
took longer for the color formation. FIG. 34 shows the
time-dependent spectral response obtained during the growth of Au
nanostructures. In FIG. 34, the graphs depict a time-dependent
Au-10 reaction after (a) 0 minutes (control); (b) 1 minute; (c) 2
minutes; and (d) 3 minutes. The spectra recorded in the early stage
show a broad peak at 550 nm, which can be assigned to the
transverse component of SPR absorption. The intensity of the peak
increases monotonically with time indicating the increase in the
amount of the gold products. It can be observed from FIG. 34 that
the intensity of the UV-vis absorption peak increases up to 2 min,
and then increases exponentially because of the formation of the
product. The reaction completes within a few minutes. FIG. 35 shows
a typical UV-vis spectrum of gold nanostructures obtained by
reducing chloroauric ions with a natural muscle-6013 (Au-10)
extract. The broad SPR bands centering at 550 nm are clearly
visible, which can be attributed to the in-plane dipole
resonance.
[0165] Similarly, the UV-vis spectra for other compositions
identified in Table 8 are shown in FIGS. 36-38. In FIG. 36 curves
(a) through (c) represent UV spectra of (a) Au-15, (b) Au-5 and (c)
Au-10 samples. In FIG. 37, curves (a) and (b) represent UV spectra
of (a) Au-7 and (b) Au-12 samples. Samples Au-5, Au-10 and Au-15
reveal a similar spectra to Au-3, Au-8, and Au-13 samples. However,
samples such as Au-1, Au-6, Au-7, Au-11 and Au-12 did not show the
absorption at 550 nm.
[0166] Representative XRD patterns of the gold nanostructures
synthesized by different plant extracts are listed in Table 8 and
found in FIG. 39. A number of Bragg reflections were present which
could be indexed on the basis of the face-centered cubic (fcc) gold
structure. No additional impurities were found except a broad hump
around 2.theta. 20.sup.0 . The broad hump may be from the organic
moieties present in the extract. The XRD pattern clearly shows that
the gold nanostructures are crystalline. In addition, the intensity
of the (111) diffraction is much stronger than those of the (200)
and (220) diffractions. These observations indicate that the gold
nanostructures formed by the reduction of Au(III) by plant extract
are dominated by {111} facets, and hence more {111} planes parallel
to the surface of the supporting substrate were sampled.
[0167] Scanning electron microscopy was used to understand the
surface morphology of the Au nanostructures. SEM images of samples
(a) Au-1; (b) Au-2; and (c-d) Au-4 samples are found in FIG. 40.
Sample Au-2 formed spherical nanostructures with sizes ranging from
100 to 300 nm. Au-1 and Au-4 also yielded a few spherical
nanoparticles along with prisms and hexagonal structures. (See
FIGS. 41 and 42.)
[0168] Similarly, Au-11, and Au14 samples yielded mainly prisms and
hexagonal Au nanostructures along with small amount of spherical
particles. The same trend continued for Au-6 and Au-9 samples. The
samples of Au-10 and Au-12 consist of spherical particles with
sizes ranging from 100-200 nm.
[0169] Typical TEM images revealing the size and morphology of the
gold nanostructures are given in FIGS. 43 and 44. The
nanostructures range in size from about 20 nm to more than a micron
in diameter, depending upon the extract used for the preparation.
Different shapes such as spherical and hexagonal geometries with
very smooth edges were observed. The single-crystalline structure
of these nanostructures was further confirmed by their
corresponding electron diffraction patterns. FIG. 45 show the TEM
image of isolated nanostructures obtained using Au-1, Au-2 and Au-5
samples, respectively. The Au-1 sample yielded interesting plate
stacks whereas Au-2 sample yielded mixed prisms, rods and spherical
particles. The Au-5 sample was observed to form only spherical
nanoparticles with sizes ranging from 20-50 nm. Similarly, TEM
images of Au-3 and Au-4 at lower and higher magnification is shown
in FIG. 45. the Au-3 sample yielded only spherical particles, in
contrast to the Au-4 sample, which mainly formed prisms and
hexagonal structures.
[0170] Au nanostructures were also made using commercially
available surfactants such as butyl ammonium bromide. The reaction
between butyl ammonium bromide and HAuCl.sub.4 is spontaneous and
color changes from pale yellow to orange (see FIG. 46 for XRD
pattern). The XRD pattern after immediate reaction did not show any
peaks corresponding to Au nanostructures (see FIG. 46(a-b).
However, the overnight reacted sample had peaks which can be
indexed to cubic Au pattern. The pattern was compared with JCPDF
card no 00-004-0784.
[0171] The embodiments illustrated and discussed in this
specification are intended only to teach those skilled in the art
the best way known to the inventors to make and use the invention.
Nothing in this specification should be considered as limiting the
scope of the present invention. All examples presented are
representative and non-limiting. The above-described embodiments of
the invention may be modified or varied, without departing from the
invention, as appreciated by those skilled in the art in light of
the above teachings. It is therefore to be understood that, within
the scope of the claims and their equivalents, the invention may be
practiced otherwise than as specifically described.
* * * * *