U.S. patent application number 12/030359 was filed with the patent office on 2008-08-14 for control of transport to and from nanoparticle surfaces.
This patent application is currently assigned to NORTHERN NANOTECHNOLOGIES. Invention is credited to Darren Anderson, Jose Amado Dinglason, Jane B. Goh.
Application Number | 20080193766 12/030359 |
Document ID | / |
Family ID | 39686084 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080193766 |
Kind Code |
A1 |
Anderson; Darren ; et
al. |
August 14, 2008 |
Control of Transport to and from Nanoparticle Surfaces
Abstract
Methods of producing stabilized composite nanoparticles
comprising a nanoparticle and a multiple polyelectrolyte
stabilizing moiety layer, a method of producing a multilayer
stabilized composite nanoparticle, and such nanoparticles.
Inventors: |
Anderson; Darren; (Toronto,
CA) ; Goh; Jane B.; (Toronto, CA) ; Dinglason;
Jose Amado; (Toronto, CA) |
Correspondence
Address: |
CHOATE, HALL & STEWART LLP
TWO INTERNATIONAL PLACE
BOSTON
MA
02110
US
|
Assignee: |
NORTHERN NANOTECHNOLOGIES
Toronto
CA
|
Family ID: |
39686084 |
Appl. No.: |
12/030359 |
Filed: |
February 13, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60892927 |
Mar 5, 2007 |
|
|
|
60889609 |
Feb 13, 2007 |
|
|
|
Current U.S.
Class: |
428/403 ;
427/212; 427/214; 427/508; 427/521 |
Current CPC
Class: |
C09K 11/883 20130101;
Y10T 428/2991 20150115; B22F 1/0018 20130101; B22F 1/0062 20130101;
B01J 2/006 20130101; Y10T 428/31504 20150401; Y10S 977/773
20130101; Y10T 428/2982 20150115; C09K 11/565 20130101; Y10T
428/2998 20150115; C09K 11/02 20130101; C09K 11/0811 20130101 |
Class at
Publication: |
428/403 ;
427/212; 427/508; 427/521; 427/214 |
International
Class: |
B32B 5/16 20060101
B32B005/16; B05D 7/00 20060101 B05D007/00; C08F 2/48 20060101
C08F002/48; C08F 2/46 20060101 C08F002/46 |
Claims
1. A method of producing a stabilized composite nanoparticle
comprising the steps of: providing a solution comprising a
nanoparticle and a plurality of polyelectrolyte stabilizing
moieties; adding a collapsing agent to the solution to collapse the
plurality of polyelectrolyte stabilizing moieties about the
nanoparticle to form a composite nanoparticle; and modifying the
plurality of polyelectrolyte stabilizing moieties in the solution
to change their transport properties.
2. The method of claim 1 further comprising cross-linking the
polymeric stabilizing moiety.
3. The method of claim 1 wherein the adding step comprises adding a
water-soluble inorganic salt to the solution to collapse the
polymeric stabilizing moiety.
4. The method of claim 1 wherein the providing step comprises
providing a nanoparticle with a mean diameter in the range of
between about 1 nm to about 100 nm.
5. The method of claim 1 wherein the modifying step comprises one
of the following: changing solution pH, changing of the solvent,
adding salts, changing the solution temperature, adsorbing
additional chemical moieties to the polymer, and desorbing chemical
moieties to the polymer.
6. The method of claim 1 wherein the cross-linking step comprises
one of the following: exposure to electromagnetic radiation,
chemically induced cross-linking or thermally induced
cross-linking.
7. The method of claim 1 wherein the modifying step changes the
transport properties between the nanoparticle environment and the
nanoparticle surface.
8. The method of claim 1 wherein the modifying step changes the
optical properties of the nanoparticle composite.
9. The method of claim 8 wherein the modifying step improves the
fluorescence efficiency of the nanoparticle composite.
10. The method of claim 8 wherein the modifying step improves the
fluorescence lifetime of the nanoparticle composite.
11. The method of claim 8 wherein the modifying step narrows the
emission spectrum of the nanoparticle composite.
12. The method of claim 1 wherein the modifying step changes the
solubility of the nanoparticle composite.
13. The method of claim 1 wherein the modifying step changes the
aggregation of the nanoparticle composite.
14. The method of claim 1 wherein the modifying step changes the
permeability of the stabilizing moiety with respect to certain
small chemical entities.
15. The method of claim 1 wherein the modifying step selectively
increases the permeability of the stabilizing moiety with respect
to certain small chemical entities, and decrease the permeability
of the stabilizing moiety with respect to certain other small
chemical entities.
16. The method of claim 1 wherein the modifying step changes the
thickness of the stabilizing moiety layer.
17. The method of claim 1 wherein the modifying step changes the
density of the stabilizing moiety layer.
18. The method of claim 1 wherein the providing step comprises
providing a polymeric stabilizing moiety comprising one of the
following: an ionizable polymer, an ionized polymer, a single
polymer molecule, co-polymers thereof, and a combination of polymer
compounds.
19. The method of claim 18 wherein the providing step comprises
providing a polymeric stabilizing moiety that comprises a
polyelectrolyte.
20. The method of claim 19 wherein the providing step comprises
providing a polymeric stabilizing moiety comprising one of the
following: poly (styrene sulfonate), poly(diallyldimethylammonium
chloride), poly(acrylic acid), poly(ethyleneimine) and
poly(allylamine hydrochloride).
21. A method of producing a stabilized composite nanoparticle
comprising the steps of: providing a nanoparticle substantially
confined within a stabilizing moiety layer comprising a plurality
of polyelectrolytes; and modifying the stabilizing moiety layer to
change its transport properties.
22. The method of claim 21 further comprising cross-linking the
polymeric stabilizing moiety.
23. The method of claim 21 wherein the providing step comprises
providing a nanoparticle with a mean diameter in the range of
between about 1 nm to about 100 nm substantially confined within a
stabilizing moiety layer.
24. The method of claim 21 wherein the modifying step comprises one
of the following: changing solution pH, changing of the solvent,
adding salts, changing the solution temperature, adsorbing
additional chemical moieties to the polymer, and desorbing chemical
moieties to the polymer.
25. The method of claim 21 wherein the cross-linking step comprises
one of the following: exposure to electromagnetic radiation,
chemically induced cross-linking or thermally induced
cross-linking.
26. The method of claim 21 wherein the modifying step changes the
transport properties between the nanoparticle environment and the
nanoparticle surface.
27. The method of claim 21 wherein the modifying step changes the
optical properties of the nanoparticle composite.
28. The method of claim 27 wherein the modifying step improves the
fluorescence efficiency of the nanoparticle composite.
29. The method of claim 27 wherein the modifying step improves the
fluorescence lifetime of the nanoparticle composite.
30. The method of claim 27 wherein the modifying step narrows the
emission spectrum of the nanoparticle composite.
31. The method of claim 21 wherein the modifying step changes the
solubility of the nanoparticle composite.
32. The method of claim 21 wherein the modifying step changes the
aggregation of the nanoparticle composite.
33. The method of claim 21 wherein the modifying step changes the
permeability of the stabilizing moiety with respect to certain
small chemical entities.
34. The method of claim 21 wherein the modifying step selectively
increases the permeability of the stabilizing moiety with respect
to certain small chemical entities, and decrease the permeability
of the stabilizing moiety with respect to certain other small
chemical entities.
35. The method of claim 21 wherein the modifying step changes the
thickness of the stabilizing moiety layer.
36. The method of claim 21 wherein the modifying step changes the
density of the stabilizing moiety layer.
37. The method of claim 21 wherein the providing step comprises
providing a polymeric stabilizing moiety comprising one of the
following: an ionizable polymer, an ionized polymer, a single
polymer molecule, co-polymers thereof, and a combination of polymer
compounds.
38. The method of claim 37 wherein the providing step comprises
providing a polymeric stabilizing moiety that comprises a
polyelectrolyte.
39. The method of claim 38 wherein the providing step comprises
providing a polymeric stabilizing moiety comprising one of the
following: poly (styrene sulfonate), poly(diallyldimethylammonium
chloride), poly(acrylic acid), poly(ethyleneimine) and
poly(allylamine hydrochloride).
40. A nanoparticle composite comprising a nanoparticle with a mean
diameter in the range of between about 1 nm to about 100 nm, the
nanoparticle substantially confined within a plurality of
polyelectrolyte stabilizing moieties.
41. The composite nanoparticle of claim 40 wherein one or more of
the polyelectrolyte stabilizing moieties is cross-linked.
42. The composite nanoparticle of claim 41 wherein the
cross-linking is accomplished by one of the following:
electromagnetic radiation induced cross-linking, chemically induced
cross-linking or thermally induced cross-linking
43. The composite nanoparticle of claim 40 wherein the polymeric
stabilizing moiety layer is porous to small chemical entities.
44. The composite nanoparticle of claim 43 wherein the small
chemical entities have a mean size in the range of about 1 nm to
about 5 nm.
45. The composite nanoparticle of claim 40 wherein the polymeric
stabilizing moiety layer comprises of one of the following: an
ionizable polymer, an ionized polymer, a single polymer molecule,
co-polymers thereof, and a combination of polymer compounds.
46. The composite nanoparticle of claim 45 wherein the polymeric
stabilizing moiety layer comprises a polyelectrolyte.
47. The composite nanoparticle of claim 46 wherein the polymeric
stabilizing moiety comprises one of the following: poly (styrene
sulfonate), poly(diallyldimethylammonium chloride), poly(acrylic
acid), poly(ethyleneimine and poly(allylamine hydrochloride).
48. The composite nanoparticle of claim 40 wherein the polymeric
stabilizing moiety layer has a net charge.
49. The composite nanoparticle of claim 48 supported by a substrate
forming a stabilized nanoparticle layer on the substrate.
50. The composite nanoparticle of claim 49 wherein the substrate
surface has a net charge.
51. The composite nanoparticle of claim 49 wherein a second
nanoparticle composite with an opposite charge polarity of the
first nanoparticle composite is adsorbed to the stabilized
nanoparticle layer.
52. The nanoparticle composite of claim 49 wherein the nanoparticle
and substrate are sintered.
53. A method of producing a multilayer, stabilized composite
nanoparticle comprising the steps of: providing a composite
nanoparticle comprising a nanoparticle and a first polyelectrolyte
stabilizing moiety layer with a net charge; contacting the
nanoparticle composite with one of a second polyelectrolyte
stabilizing moiety and an adsorbate having an opposite charge
polarity of the previous polymeric stabilizing moiety layer to form
a multilayer, stabilized composite nanoparticle.
54. The method of claim 53 further comprising cross-linking a
polymeric stabilizing moiety layer by a method comprising one of
the following: exposure to electromagnetic radiation, chemically
induced cross-linking, or thermal cross-linking.
55. The method of claim 53 further comprising modifying one of a
polymeric stabilizing moiety layer and an adsorbate.
56. The method of claim 55 wherein the modifying step modifies the
transport properties between the nanoparticle environment and the
nanoparticle surface.
57. The method of claim 55 wherein the modifying step changes the
optical properties of the nanoparticle composites.
58. The method of claim 57 wherein the modifying step improves the
fluorescence efficiency of the nanoparticle composites.
59. The method of claim 57 wherein the modifying step improves the
fluorescence lifetime of the nanoparticle composites.
60. The method of claim 57 wherein the modifying step narrows the
emission spectrum of the nanoparticle composites. The method of
claim 55 wherein the modifying step changes the solubility of the
nanoparticle composites.
61. The method of claim 55 wherein the modifying step changes the
aggregation of the nanoparticle composites.
62. The method of claim 55 wherein the modifying step changes the
permeability of the stabilizing moiety with respect to certain
small chemical entities.
63. The method of claim 55 wherein the modifying step selectively
increases the permeability of the stabilizing moiety with respect
to certain small chemical entities, and decrease the permeability
of the stabilizing moiety with respect to certain other small
chemical entities.
64. The method of claim 55 wherein the modifying step changes the
thickness of the stabilizing moiety layer.
65. The method of claim 55 wherein the modifying step changes the
density of the stabilizing moiety layer.
66. The method of claim 53 wherein the providing step comprises
providing a polymeric stabilizing moiety layer comprising one of
the following: an ionizable polymer, an ionized polymer, a single
polymer molecule, co-polymers thereof, and a combination of polymer
compounds.
67. The method of claim 66 wherein the providing step comprises
providing a polymeric stabilizing moiety layer comprising a
polyelectrolyte.
68. The method of claim 67 wherein the providing step comprises
providing a polymeric stabilizing moiety layer comprising one of
the following: poly (styrene sulfonate),
poly(diallyldimethylammonium chloride), poly(acrylic acid),
poly(ethyleneimine) and poly(allylamine hydrochloride).
Description
[0001] This application claims the priority of U.S. Provisional
Application Nos. 60/889,609 filed Feb. 13, 2007 and 60/892,927
filed Mar. 5, 2007, the entire contents of all of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] Nanoparticles are nanometer-sized materials e.g., metals,
semiconductors, polymers, and the like, that can often posses
unique characteristics because of their small size. Nanoparticles
are of particular interest because of their potential for use as
catalysts, photocatalysts, adsorbents, sensors, and ferrofluids, as
well as for their material properties in for application to
optical, electronic, and magnetic devices, and formulation of
plastics and other materials.
[0003] In practical application, however, the usefulness of a
nanoparticle depends on more than just the properties exhibited in
the laboratory. In practical application many interesting
laboratory properties may not be realized due to interferents and
undesired reactions with chemicals in the application
environment.
SUMMARY OF THE INVENTION
[0004] In various aspects, the present inventions provide
nanoparticle compositions comprising a stabilizer and methods to
tailor the permeability of a stabilizer that, e.g., impart a
nanoparticle composite with certain solubility and non-aggregative
characteristics. For example, in various embodiments, a stabilizer
can be modified to tune its permeability to materials moving from
the nanoparticle surface to the surrounding environment and/or vice
versa.
[0005] In various aspects, the present invention provides methods
to produce nanoparticles that are stabilized, where the stabilizer
provides solubility and/or prevents aggregation, and with a
selected permeability to selected small chemical entities. For
example, in various embodiments, the present inventions provide
methods for producing a stabilized composite nanoparticle
comprising the steps of: a) providing a solution comprising at
least one nanoparticle and at least one stabilizing moiety
dispersed therein; and, b) modifying at least one stabilizer moiety
in the solution to change its permeability to SCEs.
[0006] For example, in various embodiments, the present inventions
provide nanoparticle compositions that are stabilized, where the
stabilizer is chosen to allow for one or more of: (a) improved
permeability to certain SCEs; (b) decreased permeability to certain
SCEs; and (c) improved permeability to a first group of SCEs and
decreased permeability to a second group of SCEs.
[0007] In preferred embodiments of the present invention, the
stabilizing moiety comprises one or more polymeric stabilizers.
Examples of suitable means to modify the polymeric stabilizer to
change the nanoparticle transport properties include, but are not
limited to, (a) radiation or chemical-induced internal and/or
external crosslinking of stabilizer moieties, where the degree of
crosslinking controls the permeability of the layer; (b) change of
solution conditions and/or use of heating and/or cooling to induce
expansion or contraction of the polymeric stabilizer layer; (c)
adsorption or desorption of additional moieties (adsorbates) to the
polymer network, which can be assisted by chemical bond formation
or cleavage; and (d) one or more combinations thereof. Non-limiting
examples of suitable polymeric materials for use as stabilizer
moieties are discussed herein, and but can be synthetic or
naturally occurring and can be linear, branched, hyperbranched,
and/or dendrimeric.
[0008] As used herein, the terms "stabilizing moiety" or
"stabilizer" are used interchangeably and refer to a material that
interacts with the nanoparticle (e.g., through covalent,
non-covalent, ionic, van der Waals, etc. bonds) and which imparts
desirable solubility characteristics and/or prevents aggregation of
the nanoparticles.
[0009] As used herein, the terms "adsorbate" and "adsorbate moiety"
are used interchangeably and refer to an entity that preferentially
associates with a polymer-stabilized nanoparticle. This association
can be physisorption, chemisorption, through covalent bonds,
through electrostatic interactions, or through van der Waals forces
and the like.
[0010] As used herein, the term, "small chemical entities" (SCEs)
refers to cations, anions, or neutral species of various types that
are between about 0.1 nanometers (nm) to about 5 nm in size and are
soluble in the solvent in which the nanoparticles are dispersed. In
various embodiments, where for example the nanoparticles are
provided alone or on a solid support, SCEs refer to cations,
anions, or neutral species of various types that are between 0.1 nm
to about 5 nm in size and in the gaseous state.
[0011] As used herein, the terms "nanoparticle composition" when
referring to a nanoparticle composition comprising one or more
stabilizer moieties and "stabilized nanoparticle" are used
interchangeably.
[0012] As used herein, the terms "solid support" and "support" are
used interchangeably and refer to any solid phase material.
Examples of solid supports include, but are not limited to, resins,
membranes, gels, and micron-sized or larger particulates. A solid
support can be composed of one or more organic polymers such as,
e.g., polystyrene, polyethylene, polypropylene, polyfluoroethylene,
polyethyleneoxy, and polyacrylamide. A solid support can be
composed of one or more inorganic materials, such as, e.g., glass,
silica, controlled-pore-glass, or reverse-phase silica. The solid
support can be porous or non-porous, and can have swelling or
non-swelling characteristics.
[0013] Suitable stabilizing moieties for the present invention
include stabilizing moieties that can be internally or externally
chemically modified to introduce new intramolecular and/or
intermolecular chemical bonds between one or more stabilizing
moieties, e.g., to crosslink one or more stabilizing moieties.
Suitable stabilizing moieties also include stabilizing moieties
taken alone or in combination, which have a three-dimensional
structure that can be expanded or contracted using a chemical or
physical change. Suitable stabilizing moieties also include
stabilizing moieties taken alone or in combination that are
modified to increase or decrease the thickness or density of the
layer about a nanoparticle containing the stabilizing moieties.
[0014] In various embodiments, suitable stabilizing moieties
include, but are not limited to, polymers, ligands, coordinating
ions, coordinating complexes, or combinations thereof.
[0015] In various embodiments. the present inventions provide a
stabilized nanoparticle incorporated onto or into a solid support
using standard techniques such as spin coating, extrusion,
codeposition, layer-by-layer assembly, or the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The foregoing and other aspects, embodiments, objects,
features and advantages of the present inventions can be more fully
understood from the description in conjunction with the
accompanying drawings. In the drawings, like reference characters
generally refer to like features and structural elements throughout
the various figures. The drawings are not necessarily to scale,
emphasis instead being placed upon illustrating the principles of
the present inventions, wherein.
[0017] FIG. 1 schematically depicts a nanoparticle composition
(102) comprising a nanoparticle (NP) and a stabilizer moiety layer
(104); illustrating that increased cross-linking (106) of the
stabilizing moieties (situation A) reducing permeability to a SCE
(108) compared to a composition with a lesser degrees of
cross-linking (situation B).
[0018] FIG. 2 schematically depicts a nanoparticle composition
(202) comprising a nanoparticle (NP) and a stabilizer moiety layer
(204); illustrating that less favorable interaction of the
stabilizing moieties with the solvent (situation A) resulting in
contraction of the stabilizer moiety layer (206) and reducing
permeability to a SCE (208) compared to a composition with a more
favorable interaction of the stabilizing moieties with the solvent
(situation B) resulting in expansion of the stabilizer moiety layer
(210) and increased permeability to a SCE.
[0019] FIG. 3 schematically depicts the modification of a
nanoparticle composition (302) comprising a nanoparticle (NP) and a
stabilizer moiety layer (304) by addition of an adsorbate moiety
(306); illustrating modification of the stabilizing moieties with
an adsorbate (situation A) reducing permeability to a SCE (308)
compared to a composition without an adsorbate (situation B).
[0020] FIG. 4 schematically depicts layer-by-layer assembly of a
nanoparticle composition according to various embodiments of the
present inventions.
[0021] FIG. 5 depicts photoluminescence spectra of CdTe--S quantum
dots of Example 2 treated with polyelectrolyte stabilizers. The
dotted line is for the sample exposed to high intensity UV
radiation (254 nm) while the solid line is for the sample not
exposed to the UV radiation.
[0022] FIG. 6 depicts photoluminescence spectra of CdTe--S quantum
dots of Example 2 not treated with stabilizers. The dotted line is
for the sample exposed to high intensity UV radiation (254 nm)
while the solid line is for the sample not exposed to UV
radiation.
[0023] FIG. 7 depicts UV visible and emission spectra for CdS/PAA
of Example 3 formed using Cd.sup.2+/PAA that was crosslinked at
different times.
[0024] FIG. 8 depicts a graph of absorbance versus time.
[0025] FIG. 9 depicts measured Cd concentration in solutions
prepared according to Example 5.
[0026] FIG. 10 depicts the Emission spectra of CdTe--CdS (yellow)
(excitation=350 nm) showing the blue shift of the emission maximum
from no PSS (.lamda.max=570 nm) to 5% PSS (.lamda.max=560 nm) to
25% PSS (.lamda.max=555 nm)
[0027] FIG. 11 depicts the mission spectra of CdTe--CdS (orange)
(excitation=408 nm) showing the blue shift of the emission maximum
from no PSS (.lamda.max=645 nm) to 5% PSS (.lamda.max=640 nm) to
25% PSS (.lamda.max=630 nm)
DESCRIPTION OF VARIOUS EMBODIMENTS
[0028] Prior to further describing the present inventions, it may
be helpful to provide a general discussion of polymers and
nanoparticles.
A. General
[0029] The conformation of a polymer in solution is dictated by
various conditions of the solution, including, for example, its
interaction with the solvent, its concentration, and the
concentration of other species that may be present. A polymer can
undergo conformational changes, e.g., depending on the pH, ionic
strength, cross-linking agents, temperature and concentration. For
polyelectrolytes, at high charge density, e.g., when "monomer"
units of the polymer are fully charged, an extended conformation is
adopted due to electrostatic repulsion between similarly charged
monomer units. Decreasing the charge density of the polymer, e.g.,
through addition of salts or a change of pH, can result in a
transition of the extended polymer chains to a more tightly packed
globular, i.e., collapsed conformation. Such a collapse transition
is driven by attractive interactions between the polymer segments
that overcome the electrostatic repulsion forces. Changing the
solvent environment of a polymer can induce a similar transition.
This collapsed polymer can be of nanoscale dimensions and a
nanoparticle. This collapsed conformation can be rendered
irreversible by the formation of intramolecular chemical bonds
between segments of the collapsed polymer, e.g., by
cross-linking.
[0030] As used herein, the term "collapsed polymer" refers to an
approximately globular form, generally as a spheroid, but also as
an elongate and/or multi-lobed conformation collapsed polymer
having nanometer dimensions.
B. Nanoparticle Compositions
[0031] In various aspects, the present inventions provide
nanoparticle compositions comprising a nanoparticle having a layer
of one or more stabilizer moieties. The stabilizer moieties can be
chosen, e.g., for permeability to various SCEs and thus the ease or
difficulty with which an SCE can reach or leave the nanoparticle
can be selected. The degree to which materials are allowed to move
to or from the nanoparticle surface, through the stabilizer layer,
out of or into the nanoparticle environment is referred to as
"permeability." Highly permeable stabilizer layers to a SCE, e.g.,
allow for facile movement of the SCE between the nanoparticle
surface and environment, while impermeable stabilizers limit this
movement. It is to be understood that permeability varies depending
on the size and chemical character of the species (SCE) attempting
to pass through the stabilizer layer.
[0032] In various embodiments, a nanoparticle composition of the
present inventions and/or formed by a method of the present
inventions has a mean diameter in the range between about 1
nanometer (nm) to about 100 nm. In various embodiments, the
composite nanoparticle has a mean diameter in one or more of the
ranges between: (a) about 1 nm to about 10 nm; (b) about 10 nm to
about 30 nm; (c) about 15 nm to about 50 nm; and (d) about 50 nm to
about 100 nm). It is to be understood that the term "mean diameter"
is not meant to imply any sort of specific symmetry (e.g.,
spherical, ellipsoidal, etc.) of a composite nanoparticle. Rather,
the composite nanoparticle could be highly irregular and
asymmetric.
[0033] In various practical applications of nanoparticles,
nanoparticle interaction with deactivating compounds, solubility,
and/or unwanted aggregation can be a problem. In various
embodiments of the present inventions, nanoparticle compositions
are provided having a stabilizer that provides solubility and/or
prevents aggregation, but allows transport of materials from the
nanoparticle environment to the nanoparticle surface and vice
versa. In various versions, such embodiments can have practical
application in the areas, e.g., of slow-release pharmaceuticals,
agrochemicals, corrosion inhibitors, and the like, where the
nanoparticle comprises an active agent that is to be released.
Modifications to the stabilizer layer can be used to provide
nanoparticle compositions with tailored release profiles (such as,
e.g., controlled release, sustained release, delayed release, etc);
transport rates to the nanoparticle and/or away from the
nanoparticle.
[0034] For example, in various embodiments, the nanoparticle
compositions comprising a stabilizer layer that allows certain SCE
transport to and from the nanoparticle can be use in catalysis
applications, where, e.g., the transport of chemical reagents to
the nanoparticle surface is necessary for the catalytic activity of
the nanoparticles. In various embodiments, the stabilizer layer can
be chosen to have different transport properties of a SCE to the
surface of a nanoparticle than the transport properties of the
reaction product of the SCE, activated SCE (e.g., by catalytic
activation) away from the SCE. Such differences in transport
properties can be used, e.g., to control reaction rates (e.g., by
transport to the catalytic surface), provide sufficient time for
catalytic activation (e.g., by adjusting transport away from
nanoparticle surface), etc. The control of transport to and from
the nanoparticle surface of various SCE by selection and/or
modification of the stabilizer can be used to adjust or control
other factors of chemical processing such as the rate of gas
evolution, heat build up, etc. that can be problematic in large
scale chemical processing. In various embodiments, the stabilizer
layer can have a dynamic aspect, e.g., the stabilizer undergoing a
change or series of changes during the catalytic reaction to
facilitate further downstream reactions. In various embodiments,
the dynamic change can be cyclic (e.g., periodic) facilitating
providing a first stabilizer layer for a first reaction, a second
stabilizer layer for a second reaction (the second stabilizer
formed by a modification of the first layer), followed by reversion
to the first stabilizer layer for a new first reaction. It is to be
understood that more than two that such cycles or series of
stabilizer layers can be used, such as for example, a three-layer
cycle or series, a four layer cycle or series, etc. The changes to
the stabilizer layer can be initiated by compounds produced in situ
and/or addition of compounds and/or external stimuli (e.g.,
radiation, heat, etc.).
[0035] In various embodiments of the present invention, the
stabilized nanoparticle, nanoparticle compositions, of the present
inventions facilitate providing and/or provide improved optical
properties, such as narrower emission spectra, improved
fluorescence efficiency, modified fluorescence lifetimes, and the
like compared to substantially similar nanoparticles without a
stabilizer layer.
C. Nanoparticles
[0036] A wide variety of molecules can be used to form the
nanoparticle including, but not limited to, organic or inorganic
charged ions or a combination thereof. In various preferred
embodiments, the nanoparticle comprises an elemental metal, alloy
comprising a metal, or a metal species-containing compound, the
metal is preferably Cd, Zn, Cu, Pb, Ag, Mn, Ni, Au, Mg, Fe, Hg, Pt
or a combination or alloy of one or more thereof. As used herein,
by the term "metal species-containing compound" is meant a compound
containing a metal or metalloid in any valence state. In various
preferred embodiments, the nanoparticle comprises semiconductor
crystals, including, but not limited, to CdS, CdSe, CdTe, ZnS,
ZnSe, ZnTe, PbS, PbSe, PbTe, CuI, HgS, HgSe, and HgTe. These
semiconductors can be ternary or quaternary semiconductors,
including, but not limited to, CdTe/S, CdSe/S, CdTe/Se, Cd/ZnTe,
Cd/ZnSe/Te, and the like. In various preferred embodiments, the
nanoparticle comprises oxides, such as ZnO, SnO.sub.2, CoO, NiO,
CdO, InO.sub.2, and the like. In various preferred embodiments, the
nanoparticle comprises more complex systems, including alloys such
as Ag/Au, Ag/Cu, Au/Cu, phosphates such as LiFePO.sub.4, chromates
such as PbCrO.sub.4, and the like.
D. Stabilizing Moieties
[0037] The nanoparticle compositions of the present inventions
comprise a nanoparticle preferably surrounded by at least one
stabilizer moiety. A stabilizer moiety for use in the present
inventions can be any molecule capable of collapse that contains
units of monomers, that can be synthetic or naturally occurring and
can be linear, branched, hyperbranched, and/or dendrimeric.
[0038] When considering various practical applications of the
present inventions, there are three main functions of a stabilizer.
One function can be to modify and/or control the interactions of
the nanoparticles with each other and/or with a solvent, e.g., to
provide certain solubility characteristics or to prevent
aggregation. A second function can be to prevent transport of other
materials dissolved in the nanoparticle environment (e.g., tissue,
solvent, air, etc.) to the nanoparticle surface, which, e.g., can
often cause deactivation of nanoparticle properties, such as, e.g.,
fluorescence. A third function can be to prevent release of the
material comprising the nanoparticle into the nanoparticle
environment (e.g., tissue, solvent, air, etc.), e.g., to prevent
the nanoparticle from decomposing or dissolving into its component
parts, eliciting a toxic response, etc. It is to be understood that
the second and third functions can apply to nanoparticles in
gaseous systems as wells as those in a liquid environment.
[0039] In various preferred embodiments of the present inventions,
the stabilizing moiety comprises one or more polymers with
ionizable or ionized groups. An ionizable moiety or group is any
chemical functional group that can be rendered charged by adjusting
solution conditions, while ionized moieties refers to chemical
functional groups that are charged regardless of solution
conditions. An ionizable moiety also includes any chemical
functional group that can be rendered charged by the use of
radiation or by the use of a static electromagnetic field. The
ionized or ionizable moiety or group can be either cationic or
anionic, and can be continuous along an entire chain as in the case
of regular polymers, or can be interrupted by blocks containing
different functional groups, as in the case of block polymers.
[0040] Examples of polymer stabilizers suitable in various
embodiments include, but are not limited to, polyelectrolytes such
as, e.g., poly(acrylic acid), poly (styrene sulfonate),
poly(diallyldimethylammonium chloride), poly(allylamine
hydrochloride) (PAH), or others. Suitable examples of adsorbates
include similar polyelectrolytes. In various preferred embodiments
employing an adsorbate, the polymer stabilizer is of a larger
molecular weight than the adsorbate moieties.
[0041] In various embodiments, a preferred cationic group is the
amino group and preferred anionic groups are carboxylic acid,
sulfonic acid, phosphates, and the like. For cationic polymers,
examples include, but are not limited to, poly(allylamine),
poly(ethyleneimine), poly(diallyldimethylammonium chloride),
poly(arginine), chitosan, cationic collapsible proteins,
poly(methacrylamido propyl trimethyl ammonium chloride) and
poly(lysine). For anionic polymers, examples include, but are not
limited to, poly(acrylic acid), poly(styrene sulfonic acid),
poly(glutamic acid), poly(methacrylic acid), poly(aspartic acid),
nucleic acids, anionic collapsible proteins, poly (anetholesulfonic
acid), cellulose, poly(maleic acid) poly(vinyl phosphoric acid),
etc. Block polymers are made up of blocks of polymers having
different functional groups. The block polymers can be made up of
blocks of any of the mentioned anionic and cationic polymers and
another polymer that imparts a specific desirable property to the
block polymer.
E. Formation of Nanoparticle Compositions & Modification of
Stabilizer Layer
[0042] In various preferred embodiments of the present inventions,
a polymer-stabilized nanoparticle composition of the present
inventions is produced in a suitable solvent by collapse of a
stabilizer moiety about a nanoparticle or nanoparticle precursor
moiety. A wide variety of solvents can be used to form a solution
of use in the present inventions. In various embodiments, the
solution is preferably an aqueous solution.
[0043] In preferred embodiments of the present inventions, a chosen
stabilizer moiety is dissolved in a suitable solvent to form a
solution of the stabilizer. The solvent can be water, an organic
solvent or a mixture of two or more such solvents. The addition to
the solution of the collapsing agent induces a collapse of the
stabilizer about the nanoparticle or nanoparticle precursor. The
collapsing agent can itself be the nanoparticle or nanoparticle
precursor. For example, the nanoparticle or nanoparticle precursor
can be an inorganic salt that is water soluble where the water
soluble inorganic salt is of the form M.sub.xA.sub.y where M is a
metal cation belonging to Groups I to IV of the Periodic Table
possessing a charge +y and A is the counter ion to M with a charge
-x or a combination thereof.
[0044] Various preferred embodiments of the present inventions
involve the formation of composite nanoparticles by the addition of
ions that induce precipitate formation of the nanoparticle or
nanoparticle precursor within the collapsed stabilizer, wherein the
stabilizer is intra-molecularly and/or inter-molecularly
cross-linked. As used herein, "precipitation" of a nanoparticle or
nanoparticle precursor having a stabilizer layer refers to
modification of the ion to a compound that is substantially
insoluble in the solvent of the solution.
[0045] Collapsing agents are usually water-soluble inorganic salts,
most preferably, those that contain metal cations and their
corresponding anions. Examples of collapsing agents include, but
are not limited to, Cd(NO.sub.3).sub.2, Zn(NO.sub.3).sub.2,
Cu(SO.sub.4), Pb(NO.sub.3).sub.2, Pb(CH.sub.3COO).sub.2,
Ag(NO.sub.3), Mn(SO.sub.4), Ni(NO.sub.3).sub.2.
[0046] A variety of techniques can be used to collapse the
stabilizer around a nanoparticle or nanoparticle precursor. For
example, in various embodiments a collapsing agent such as a
different solvent, an ionic species (e.g., a salt); or combinations
thereof can be used. In various embodiments, it is preferred that
the nanoparticle or nanoparticle precursor itself serve as a
collapsing agent. Multiple collapsing agents can be used.
[0047] In various embodiments, to retain the collapsed conformation
of the stabilizer layer, cross-linking of the collapsed stabilizer
is achieved by exposing the polymer to .gamma.-radiation or UV
radiation. Preferably, the UV radiation is UV laser radiation or UV
arc lamp radiation. In various embodiments, intra-molecular
cross-links are chemically produced, for example, with carbodiimide
chemistry with a homobifunctional cross-linker.
[0048] In preferred embodiments, the polymer stabilizer moiety or
moieties are at least partially crosslinked so that the favorable
solubility and non-aggregative properties of the nanoparticle
composition are maintained. In various embodiments, the stabilizer
layer is stabilized by inter-molecular crosslinks to form a
gel.
1. Crosslinking in General
[0049] The polymer stabilizer is preferably chosen to be
susceptible to chemical or physical crosslinking. In various
embodiments, control of the permeability of the stabilizer to SCEs,
e.g., modification of the stabilizer layer, is achieved through
control of the degree of crosslinking of the stabilizing polymer.
For example, by increasing the degree of chemical crosslinking, the
permeability of the stabilizer to SCEs can be decreased.
[0050] A wide variety of means can be used to cross-link the
stabilizer layer, for example: chemical means through radical
reactions of pendant groups containing unsaturated bonds; through
the use of molecules having multifunctional groups than can react
with the functional groups of the stabilizer moeity; though
high-energy radiation, such as, e.g., gamma radiation.
[0051] Crosslinking can be achieved through chemical means through
introduction of multidentate molecules as crosslinkers. These
molecules contain multiple functional groups that can form covalent
bonds with the functional groups on the stabilizer moieties. These
molecules can be linear, branched, or dendrimeric. For example, a
molecule containing multiple amine groups, such as
2,2'-ethylenedioxydiethylamine can effect the intramolecular
crosslinking of poly(acrylic acid). The cross-linking reaction in
this case can be promoted by the addition of an activating agent,
typically used for amide bond formation, such as a
carbodiimide.
[0052] Chemical treatment can also be carried out to derivatize the
stabilizer layer, such that a fraction of the ionizable groups are
converted to groups that can be cross-linked through free-radical
reactions. An example is to convert some of the carboxylic acid
groups of poly(acrylic acid) to allyl esters. The allyl groups can
then be reacted to form intramolecular bonds through radical
chemistry.
[0053] Crosslinking by irradiation can be effected by exposing a
solution of the collapsed stabilizer to an electromagnetic
radiation source. The radiation source can be, for example, an
excimer laser, a mercury arc lamp, a light emitting diode, a UV
germicidal lamp or gamma rays. For the purposes of this
specification, crosslinking through means such as irradiation shall
be referred to as "physical crosslinking."
[0054] The degree of chemical cross-linking can be controlled by
controlling the relative concentration of multidentate molecules,
activating agents, or other reactive groups. The degree of physical
cross-linking can be controlled by controlling the dose,
wavelength, or type of radiation to which the polymer-stabilized
nanoparticles are exposed.
2. Stabilizing Layer Modifications
[0055] In various aspects, the present inventions also provide
methods to modify the properties of the stabilizer so that, in
various embodiments, nanoparticles compositions having stabilizers
with specific desired transport properties of material to and/or
from the nanoparticle environment to and/or from the nanoparticle
surface, and vice versa, can be produced.
[0056] In various preferred embodiments, the step modifying a
stabilizer layers occurs after collapse of the stabilizer moieties
about a nanoparticle or nanoparticle precursor but prior to
cross-linking of the stabilizer layer; substantially during or
concurrent with cross-linking of the stabilizer layer; after
cross-linking of the stabilizer layer; or a combination of one or
more of prior to, during, concurrently and after cross-linking of
the stabilizer layer.
[0057] In various embodiments, selection of the permeability and/or
other properties of the stabilizer layer are provide for by
selecting the degree of intra-molecular and/or intermolecular
cross-linking of the stabilizer moieties. FIG. 1 schematically
depicts a nanoparticle composition (102) comprising a nanoparticle
(NP), or nanoparticle precursor, and a stabilizer moiety layer
(104). FIG. 1 illustrates that increasing the degree of
intra-molecular cross-linking (106) of the stabilizing moieties
(situation A) decreases the permeability of the stabilizer layer to
a SCE (108), whereas decreasing the degree of intra-molecular
cross-linking (situation B) increase the permeability of the
layer.
[0058] In various embodiments of the present inventions, a
polymer-stabilized nanoparticle is provided in a suitable solvent.
The polymer stabilizer moieties are chosen to have a
three-dimensional structure that is sensitive to solution
conditions such as pH, temperature, solvent, ionic strength, etc.
Non-limiting examples of such polymers are polymers with ionizable
groups, where interactions between these ionizable groups can
control the three-dimensional structure of the polymer. In various
versions of c=such embodiments, control of the permeability of the
stabilizer to SCEs can be achieved. through control of the
three-dimensional structure using changes in solution conditions.
In preferred embodiments, the polymer stabilizer moiety or moieties
are at least partially crosslinked so that the favorable solubility
and non-aggregative properties of the nanoparticle composition are
maintained.
[0059] Changes in the three-dimensional structure of ionized or
ionizable polymers can be effected, e.g., using changes in pH,
temperature, solvent, ionic strength, etc. Normally in solution, at
high charge density, e.g., when "monomer" units of the stabilizer
polymer are fully or highly charged, an extended conformation is
adopted due to electrostatic repulsion between similarly charged
monomer units. Decreasing the charge density of the polymer, which
can be effected through addition of salts or a change of pH, can
result in the transition of extended polymer chains to a collapsed
conformation. If, instead of being able to freely interact with the
solution, the polymer is in a non-extended conformation, changes in
charge density on the polymer can result in swelling or contraction
of the polymer. The non-extended conformation can occur even at
high charge density if, for example, the polymer has formed a
collapsed conformation and was then internally crosslinked
chemically or physically. For example, even if the initial cause of
collapse is removed the polymer may retain its basic collapsed
shape, though it may swell or contract depending on conditions.
This can also occur if the polymer is externally crosslinked with
other polymers (inter-molecular crosslinking), e.g., forming a gel.
Cross-linking the stabilizer layer (both by intra-molecular and/or
inter-molecular crosslinking) can provide to a polymer system with
a substantially inflexible shape. Where one or more stabilizer
layers have a substantially inflexible shape, increases in charge
density can lead to repulsion between the monomers of the
stabilizer polymers. Since the polymers are not able to adopt an
extended conformation, they will instead swell, substantially
maintaining the shape of the layer but increasing in porosity.
Similarly, decreases in charge density can lead to a reduction in
repulsive interactions of the monomers of the polymers, leading to
contraction of the stabilizer layer.
[0060] Contraction or swelling of the polymer stabilizer layer can
be similarly effected by changing solvent conditions. For example,
replacement of a first solvent with a second solvent with which the
polymer has decreased favorable interactions with will encourage
contraction of the polymer stabilizer. Similarly, replacement of a
first solvent with a second solvent with which the polymer has
increased favorable interactions will encourage swelling of the
polymer stabilizer. In various versions of these embodiments,
suitable stabilizers include polymers stabilizers that have
ionizable groups and dissimilar interactions with different
solvents. In various preferred embodiments, the polymer stabilizer
is soluble in both the first and second solvents in order to
maintain favorable solubility and non-aggregative properties of the
stabilized nanoparticle.
[0061] Examples of suitable solvent systems include, but are not
limited to, water-soluble polymers where the first solvent is
aqueous and the second solvent is a combination of water and
ethanol; alcohol-soluble polymers where the first solvent is a
small-chain alcohol and the second solvent is a longer-chain
alcohol and the like.
[0062] Modification of the three-dimensional structure of the
polymer stabilizer, e.g., by swelling or contraction of the polymer
can be used to change the permeability of the polymer stabilizer to
SCEs. For example, FIG. 2 schematically depicts a nanoparticle
composition (202) comprising a nanoparticle (NP) or nanoparticle
precursor, and a stabilizer moiety layer (204). FIG. 2 illustrates
that that less favorable interaction of the stabilizing moieties of
the layer (204) with the solvent (situation A) can result in
contraction of the stabilizer moiety layer (206) and reduce
permeability to a SCE (208). A composition with a more favorable
interaction of the stabilizing moieties with the solvent (situation
B) resulting in expansion of the stabilizer moiety layer (210) and
an increased permeability to a SCE (208).
[0063] Suitable means to modify the stabilizer to change its
permeability to SCEs also include methods to modify stabilizing
moieties to increase or decrease the size of the stabilizing
moieties. The means can include, e.g., physical or chemical
absorption or desorption of additional chemical entities (e.g.,
adsorbates), which can be polymers, ligands, coordinating
complexes, or combinations thereof. The means can further comprise
a chemical reaction to assist in the adsorption or desorption
process. For example, in various embodiments, the stabilizing
moiety is further functionalized to improve compatibility with the
further adsorbed species. In various embodiments, this adsorption
or desorption process occurs subsequent to the production of a
stabilized nanoparticle, during the production of a stabilized
nanoparticle, or both.
[0064] For example, in various embodiments, an adsorbate moiety is
added to a polymer-stabilized nanoparticle while the
polymer-stabilized nanoparticle is being synthesized. In various
preferred embodiments, the polymer stabilizer is a polymer with
ionizable groups, e.g., a polyelectrolyte, and the nanoparticle is
formed using a collapse transition of the polyelectrolyte. The
adsorbate moiety is added to the solution prior to the collapse
transition, subsequent to the collapse transition, or both, and
interacts with the collapsed polyelectrolyte. In various preferred
embodiments, the adsorbate is a lower molecular-weight
polyelectrolyte than the polymer stabilizer. As a non-limiting
example, low molecular weight PAA or PAH can be added to a polymer
solution of large molecular weight PAA prior to collapse and
formation of a nanoparticle having a stabilizer layer. The low
molecular weight polyelectrolyte can interact with the polymer
stabilizer to decrease the permeability of the stabilizer layer to
SCEs.
[0065] In various embodiments of the present inventions, a
polymer-stabilized nanoparticle is provided in a suitable solvent.
Subsequent treatment of the polymer-stabilized nanoparticle with an
adsorbate moiety results in a thicker or denser polymer-adsorbate
composite stabilizer layer. This adsorbate, can be chemically
and/or physically adsorbed to the polymer stabilizer, e.g., the
adsorbate can be covalently bound to the polymer stabilizer,
physisorbed, etc. The polymer-adsorbate composite stabilizer can
decrease the permeability of the stabilizer layer to SCEs.
[0066] In various embodiments, a stabilizer layer of a
polymer-stabilized nanoparticle comprises a component that can be
desorbed or cleaved from the polymer stabilizer, resulting in a
sterically less thick or dense polymer stabilizer layer with
increased permeability to SCEs.
[0067] For example, FIG. 3 schematically depicts the modification
of a nanoparticle composition (302) comprising a nanoparticle (NP)
or nanoparticle precursor, and a stabilizer moiety layer (304).
Addition of an adsorbate moiety (306), e.g., by functionalization,
adsorption, absorption, cleavage, etc., can be used to modify the
stabilizer layer (situation A) and reduce permeability to a SCE
(308) as compared to a substantially similar stabilizer layer
without an adsorbate (situation B).
[0068] In various embodiments, the adsorbate moiety has one or more
functional groups that can be used for conjugating the stabilized
nanoparticles to other molecules containing complementary
functional groups. Examples of such molecules include, but are not
limited to, protein, ligand, oligonucleotide, aptamer,
carbohydrate, lipid, other nanoparticles, any member of
affinity-binding pairs (such as, e.g., antigen-antibody,
DNA-protein, DNA-DNA, DNA-RNA, biotin-avidin, hapten-antihapten,
protein-protein, enzyme-substrate), and combinations thereof.
[0069] In various embodiments, at least portion of the functional
groups of the adsorbate moiety can be modified to convert them to
other functional groups that can be used, e.g., for conjugation.
For example, a hetero bi-functional molecule containing an amine
group and a latent thiol group can be reacted with poly (acrylic
acid)-adsorbed nanoparticles through amide bond formation thereby
converting the carboxylic acid to a thiol group. The thiol group
can be used, e.g., for conjugation to other molecules containing
thiol-reactive groups.
[0070] In various embodiments, in addition to modifying the
thickness or density of the polymer-adsorbate stabilizer layer the
adsorbate can modify the chemical properties of the
polymer-adsorbate stabilizer. In various embodiments, this can be
used to enhance or retard changes to the permeability of the
stabilizer layer to SCEs caused by the changes in the thickness or
density of the polymer-adsorbate stabilizer. For example, a
polymer-adsorbate stabilizer having a different net charge than the
polymer stabilizer alone, would modify the net charge and thereby
can be used to modify the permeability of the stabilizer layer to
charged SCEs.
[0071] In various preferred aspects, the stabilizer layer is
composed of one or more bilayers. For example, in various preferred
embodiments, a polymer-stabilized nanoparticle is provided in a
suitable solvent. The polymer stabilizer is one or more polymer
moieties with ionizable groups where at least some of the ionizable
groups are partially or completely ionized. The presence of the
ionized groups gives the polymer stabilizer a net charge, e.g.,
positive or negative. Addition of a polymer or other adsorbate with
opposite charge can result in adsorption of the adsorbate to the
initial polymer stabilizer layer, resulting in a polymer-adsorbate
stabilizer. This process can be continued in a so-called
"layer-by-layer" fashion, where layers of adsorbates of opposite
charge are added alternately. A pair of moieties (e.g., adsorbates,
stabilizers, etc.) that are subsequently added of opposite charge
is referred to herein as a bilayer.
[0072] In various embodiments of the present inventions, individual
layers of stabilizer moiety and adsorbed polymer stabilizing layer
can be crosslinked together using radiation, chemically, or by
heating. High energy radiation in the form of UV lamps, gamma
irradiation, particulate radiation, and the like can be used to
generate free radicals to participate in a cross-linking process.
In various embodiments, bifunctional ligands such as EDC can be
used to covalently bond carboxylate groups from adjacent layers
together. In various embodiments, heating can be used to generate
crosslinks between two layers of stabilizing polymers. An example
of this process would be where the first layer contains carboxylate
groups and the second layer contains amine groups, where heating
promotes the formation of an amide covalent bond between the two
layers.
[0073] For example, FIG. 4 illustrates various embodiments of a
"layer-by-layer" assembly. A nanoparticle composition (402)
comprising a nanoparticle (NP) or nanoparticle precursor, and a
stabilizer moiety layer (404) having a net charge, is contacted
with another stabilizer moiety or adsorbate (406), with an opposite
net charge, (step 1) to form a new nanoparticle composition (408).
The steps can be repeated, a stabilizer moiety or adsorbate moiety
being added (410) of net charge opposite to the proceeding moiety
(406) to assemble additional layers (e.g., full or partial bilayers
of polyelectrolytes) on the stabilized nanoparticle (402).
F. Permeability
[0074] The permeability of a stabilizer layer can be ascertained by
a number of methods. For example, a stabilized nanoparticle can be
added to an etchant (e.g., HCl for CdS) and the rate of dissolution
measured, the rate of dissolution being be proportional to the rate
of H+ in and Cd out, which can be monitored, e.g., by watching the
intensity and position of a fluorescence peak of CdS. Another
method involves measuring the rate of dissolution/leaching of a
metal nanoparticle from the stabilized nanoparticle into solution
as a cationic metal (and thus outside the stabilizer layer), e.g.,
as in bioavailability studies. Another approach is to monitor a
property of the nanoparticle or nanoparticle precursor during
collapse and/or modification of the stabilizer moiety in the
presence of a compound that deactivates a property nanoparticle or
nanoparticle precursor, e.g., example, monitoring CdS fluorescence
in the presence of EDTA, a deactivator of CdS fluorescence.
G. Catalytic Supports
[0075] In various aspects, the present inventions provide
stabilized nanoparticles supported by a substrate. In various
embodiments, supported, stabilized nanoparticles can be used, e.g.,
in heterogeneous processes where supported nanoparticles interact
with gas- and/or liquid-borne SCEs, such as, for example, in
heterogenous catalysis. For example, in various embodiments,
stabilized nanoparticles are supported on the substrate (e.g.,
activated carbon), on the surfaces of the pores of a mesoporous
material, or a combination thereof, for catalysis of gas and/or
liquid-borne SCEs. Examples of mesoporous materials include, but
are not limited to, zeolitic materials, aluminosilicates, clays,
and other porous silicates.
[0076] A wide variety of substrates can be used as supports, and
include any solid phase material upon which a stabilized
nanoparticle can be immobilized. Examples of substrate materials
include, but are not limited to, activated carbon, mesoporous
materials, zeolites, organic polymers, inorganic surfaces, such as,
e.g., glass, controlled pore glass, silica, metals, alloys, etc.,
and combinations thereof. The support can have a variety of forms
and form factors, including, but not limited to, beads, spheres,
particles, granules, gels, membranes, surfaces. Surfaces can be a
variety of shapes, including, but not limited to, planar,
substantially planar, or non-planar. Supports can be porous,
non-porous or a combination of both, and can have swelling and/or
non-swelling characteristics.
[0077] In various preferred embodiments, a `layer-by-layer`
assembly process as described herein, such as, for example, in
section F, can be used to fashion supported, stabilized
nanoparticles. For example, in various preferred embodiments, a
polymer-stabilized nanoparticle is provided in a suitable solvent.
The polymer stabilizer comprising one or more polymer moieties with
ionizable groups where at least some of the ionizable groups are
partially or completely ionized. The presence of the ionized groups
can give the polymer stabilizer a net charge, e.g., positive or
negative. A substrate with a net surface charge of opposite
character can be exposed to a solution of these nanoparticles which
can result in absorption of nanoparticles to the surface. Addition
of a polymer, stabilized nanoparticle, bare nanoparticle, or other
adsorbate with opposite charge can result in adsorption of the
adsorbate to the initial stabilized nanoparticle layer. The process
can be continued in a so-called "layer-by-layer" fashion, where
layers of adsorbates of opposite charge can be added alternately. A
pair of moieties (e.g., adsorbates, stabilizers, etc.), where one
member of the pair has a net positive charge and the other a net
negative charge, can together be referred to herein as a
bilayer.
[0078] In various embodiments, each bilayer can comprise stabilized
nanoparticles of the appropriate charge in one and/or both of the
layers, which, for example, can be used to modify the loading of
stabilized nanoparticle in the layered substrate. In various
embodiments, one or more of the bilayers does not comprise and/or
is substantially free of nanoparticles, for example, to decrease
the loading of nanoparticles in the layered substrate.
[0079] The porosity of the layered substrate can be modified, for
example, by changing solution conditions during deposition such as
pH, ionic strength, solvent, concentrations, etc. Increased
porosity facilitates improving the diffusion of materials through
the layered substrate, while decreased porosity can, e.g., increase
the strength of coordination and barrier effects.
[0080] In various embodiments, the layered substrate is loaded with
stabilized nanoparticles with specific catalytic activity such as
metals, metal alloys, oxides, and the like. In various embodiments,
the stabilizers have increased or decreased porosity to SCEs.
[0081] In various embodiments, a layered substrate comprising
nanoparticles is sintered in a furnace in order to enhance
interconnectivity of the nanoparticles and/or burn off stabilizer
and/or other adsorbate moieties. This can result, e.g., in a porous
substrate comprising at least one type of nanoparticle. In various
embodiments, this porous substrate is used as a catalyst. In
various embodiments the porous substrate comprises an oxide. In
various embodiments the porous substrate comprises, a porous oxide
that can, e.g., act as a Lewis base in a catalytic reaction.
EXAMPLES
[0082] Various aspects and embodiments of the present inventions
may be further understood in light of the following examples, which
are not exhaustive and which should not be construed as limiting
the scope of the present inventions in any way.
Example 1
Preparation of CdTe--CdS Nanoparticles Encapsulated In PAA
[0083] A 10 mM sodium tellurite (Na.sub.2TeO.sub.3) solution was
prepared by weighing out the appropriate amount of sodium tellurite
and dissolving it in deionized water (ddH.sub.2O). A heating mantle
was heated to >100.degree. C. 50 mL of Cd-PAA solution (1.67 mM
Cd, irradiated for 1 h with 254 nm light) was put into a one-necked
round bottom flask (rbf). Trisodium citrate (50 mg) and sodium
borohydride (NaBH.sub.4, 25 mg) was added in one portion to the
stirred Cd-PAA solution. 1.25 mL Na.sub.2TeO.sub.3 solution,
prepared above, was added to the Cd-PAA solution. A condenser was
put on rbf and the reaction mixture was heated to reflux in the
heating mantle and left to reflux for 4 h. Meanwhile, another
heating mantle was preheated to 50.degree. C. After 4 h of reflux,
the reaction flask was taken out of the heating mantle and let cool
to room temperature. Meanwhile, a 100 mM solution of thioacetamide
was prepared by weighing out the appropriate amount of
thioacetamide and dissolving it in deionized water (ddH.sub.2O).
For quantum dots that emit in the green, 33 .mu.L of thioacetamide
solution was added to the reaction mixture. For yellow quantum
dots, 150 .mu.L of thioacetamide was used. For orange quantum dots,
675 uL of thioacetamide solution was used. After adding
thioacetamide, the flask was put into the heating mantle pre-heated
to 50.degree. C. The reaction was left at 50.degree. C. for 16 h,
then let cool to room temperature. The fluorescence of the yellow
and orange quantum dots are shown in FIGS. 10 and 11
respectively.
Example 2
Preparation of CdTe--CdS Nanoparticles Encapsulated In PAA/PSS
[0084] A 10 mM sodium tellurite (Na.sub.2TeO.sub.3) solution was
prepared by weighing out the appropriate amount of sodium tellurite
and dissolving it in deionized water (ddH.sub.2O). A heating mantle
was heated to >100.degree. C. 50 mL of Cd-PAA/PSS (PSS is 5% or
25% of PAA by weight) solution (1.67 mM Cd, irradiated for 1 h with
254 nm light) was put into a one-necked round bottom flask (rbf).
Trisodium citrate (50 mg) and sodium borohydride (NaBH.sub.4, 25
mg) was added in one portion to the stirred Cd-PAA solution. 1.25
mL Na.sub.2TeO.sub.3 solution, prepared above, was added to the
Cd-PAA solution. A condenser was put on rbf and the reaction
mixture was heated to reflux in the heating mantle and left to
reflux for 4 h. Meanwhile, another heating mantle was preheated to
50.degree. C. After 4 h of reflux, the reaction flask was taken out
of the heating mantle and let cool to room temperature. Meanwhile,
a 100 mM solution of thioacetamide was prepared by weighing out the
appropriate amount of thioacetamide and dissolving it in deionized
water (ddH.sub.2O). For quantum dots that emit in the green, 33
.mu.L of thioacetamide solution was added to the reaction mixture.
For yellow quantum dots, 150 .mu.L of thioacetamide was used. For
orange quantum dots, 675 uL of thioacetamide solution was used.
After adding thioacetamide, the flask was put into the heating
mantle pre-heated to 50.degree. C. The reaction was left at
50.degree. C. for 16 h, then let cool to room temperature. The
fluorescence of the yellow and orange quantum dots with 5% and 25%
PSS are shown in FIGS. 10 and 11 respectively.
Example 3
Preparation of CdTe--CdS Nanoparticles Coated With Bilayers of
Polyelectrolytes
[0085] Samples of quantum dots coated with 1, 2, or 3 bilayers of
PAA and PAH were prepared. The green CdTe--CdS quantum dots with a
PAA stabilizer were prepared according to Example 2, purified by
precipitation with ethanol, and reconstituted at 16 times its
original concentration (on a solids basis). It was then diluted 333
times with deionized, distilled water (ddH2O). To 100 .mu.L of this
solution was added alternately solutions of PAH (MW=15,000, 40
.mu.L, 0.03 mg/mL) and PAA-Na (MW =2,100, 5.mu.L, 0.3 mg/mL). After
each addition, the mixture was put on an orbital shaker for 5
minutes and then the next solution was added.
[0086] For CdTe--CdS nanoparticles with one bilayer (i.e. after one
alternate addition of PAH and PAA-Na), after one alternate addition
of PAH and PAA-Na the solution was removed from the shaker and 90
.mu.L of deionized, distilled water was added. For CdTe--CdS
nanoparticles with two bilayers, after two alternate additions of
PAH and PAA-Na the solution was removed from the shaker and 45
.mu.L of ddH2O was added. For CdTe--CdS nanoparticles with three
bilayers, after three alternate additions of PAH and PAA-Na the
solution was removed from the shaker and used.
Example 4
Polyelectrolyte Stabilizer Effect On CdTe--CdS Quantum Dot
Photoluminescence
[0087] Two sets of samples of quantum dots were prepared using a
modified version of example 1. In this case, the green CdTe--CdS
quantum dots were prepared according to Example 1 and diluted 10
times. The amounts of PAH and PAA-Na added were also modified--each
bilayer involved the addition of 10 .mu.L of each solution at
concentrations of 0.5 mg/mL and 0.05 mg/mL respectively.
[0088] One set of quantum dots was exposed to high intensity UV
radiation (254 nm) for 30 minutes while another set was kept
covered with aluminum foil tape. The photoluminescence spectra are
shown in FIG. 5. As control, two sets of solutions of quantum dots
without bilayers of PAH and PAA-Na were prepared and diluted 10
times; one set was exposed to high intensity UV radiation (254 nm)
for 30 minutes while another set was kept covered with aluminum
foil tape. The photoluminescence spectra are shown in FIG. 6.
Example 5
Effect of Crosslinking On CdS Quantum Dot Photoluminescence
[0089] Cd.sup.2+/PAA was prepared by mixing equal volumes of
aqueous 2 mg/mL Polyacrylic acid (1.2 million MW, Sigma) with 3.3
mM Cd(NO.sub.3).sub.2. Briefly, 10.0 mL of the polyacrylic acid
solution was placed in a plastic beaker with 10 mL of water and
stirred vigorously with a magnetic stir bar. To this solution, 90
mL of polyacrylic acid solution along with 90 ml of
Cd(NO.sub.3).sub.2 were added dropwise at a rate of 5 ml/minute
under vigorous stirring. To the resulting solution, 10 more ml of
Cd(NO.sub.3).sub.2 was added dropwise at a rate of 2-3 ml/min with
vigorous stirring. The resulting solution was a clear liquid.
[0090] The Cd.sup.2+/PAA was crosslinked under a UV Germicidal lamp
and aliquots at different crosslinking times were taken (0 mins, 30
mins, 1 hr, 1.5 hrs, and 2 hrs). CdS/PAA was made using
Cd.sup.2+/PAA (crosslinked at different times)--180 .mu.L of 2.8 mM
Na.sub.2S solution was added to 500 .mu.L of Cd.sup.2+/PAA
solution. The resulting UV visible and emission spectra is shown in
FIG. 7 for CdS/PAA formed using Cd.sup.2+/PAA that was crosslinked
at different times (0 hours, 30 mins., 1 hour, and 2 hours).
Example 6
Photocatalytic Activity of ZnO Nanoparticles
[0091] 100 L of methylene blue solution (0.1 mM) was added to two
separate solutions containing 100 uL of ZnO nanoparticles with a
PAA stabilizer (0.5 mg/mL based on PAA concentration). The ZnO
nanoparticles were prepared as described in Goh et al., PCT
application CD 2006/001686. Two control solutions were also made
with 100 .mu.L of ddH2O and 100 .mu.L of methylene blue solution.
The solutions were kept in the dark.
[0092] After 3.5 hours, one solution with ZnO nanoparticles and one
without was exposed to UV radiation (302 nm) and the other
solutions were kept covered with aluminum foil. Absorbance
measurements were taken after 5, 30, 60, and 189 minutes and are
shown in FIG. 8. In the absence of ZnO nanoparticles little
decrease in absorbance was observed, and accelerated breakdown was
shown for methylene blue in the presence of ZnO.
Example 7
Measurement of Cadmium Content In Unbound Form For Stabilized
CdTe--CdS Nanoparticles
[0093] Green CdTe--CdS nanoparticles with 1, 2, and 3 bilayers of
PAH and PAA were prepared as described in Example 1. A control
solution of CdTe--CdS nanoparticles with 0 bilayers was also
prepared by adding 135 .mu.L to 100 .mu.L of the diluted CdTe--CdS
solution. A control solution of polyelectrolytes was also prepared
by alternately adding 3 times 40 .mu.L of PAH and 40 .mu.L of
PAA-Na to 100 .mu.L of ddH2O with 5 minutes shaking on an orbital
shaker between addition.
[0094] 30 .mu.L of the two control solutions and the CdTe--CdS with
1, 2, and 3 bilayers were each diluted separately with 165 .mu.L of
ddH2O. The Cadmium content of each solution prepared was determined
using Measure iT Lead and Cadmium Assay kit (Invitrogen catalog
number M36353). The results are shown in FIG. 9, where a clear
change in measured Cd concentration is observed as bilayers of
polyelectrolytes are added.
Additional Examples
[0095] All literature and similar material cited in this
application, including, patents, patent applications, articles,
books, treatises, dissertations and web pages, regardless of the
format of such literature and similar materials, are expressly
incorporated by reference in their entirety. In the event that one
or more of the incorporated literature and similar materials
differs from or contradicts this application, including defined
terms, term usage, described techniques, or the like, this
application controls.
[0096] The section headings used herein are for organizational
purposes only and are not to be construed as limiting the subject
matter described in any way.
[0097] While the present inventions have been described in
conjunction with various embodiments and examples, it is not
intended that the present inventions be limited to such embodiments
or examples. On the contrary, the present inventions encompass
various alternatives, modifications, and equivalents, as will be
appreciated by those of skill in the art. Accordingly, the
descriptions, methods and diagrams of should not be read as limited
to the described order of elements unless stated to that
effect.
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