U.S. patent application number 15/138325 was filed with the patent office on 2017-03-02 for chemochromic nanoparticles, method for manufacturing the same, and hydrogen sensor comprising the same.
The applicant listed for this patent is Ajou University Industry-Academic Cooperation Foundation, Hyundai Motor Company, Kia Motors Corporation. Invention is credited to Shankara S. Kalanur, Hyun Joon Lee, Yeong An Lee, Yong Gyu Noh, Hyung Tak Seo, Hyo Sub Shim.
Application Number | 20170059538 15/138325 |
Document ID | / |
Family ID | 56178241 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170059538 |
Kind Code |
A1 |
Noh; Yong Gyu ; et
al. |
March 2, 2017 |
CHEMOCHROMIC NANOPARTICLES, METHOD FOR MANUFACTURING THE SAME, AND
HYDROGEN SENSOR COMPRISING THE SAME
Abstract
Disclosed are a chemochromic nanoparticle, a method for
manufacturing the chemochromic nanoparticle, and a hydrogen sensor
comprising the chemochromic nanoparticle. In particular, the
chemochromic nanoparticle has a core-shell structure such that the
chemochromic nanoparticle and comprises a core comprising a
hydrated or non-hydrated transition metal oxide; and a shell
comprising a transition metal catalyst.
Inventors: |
Noh; Yong Gyu; (Suwon,
KR) ; Lee; Hyun Joon; (Yongin, KR) ; Shim; Hyo
Sub; (Suwon, KR) ; Seo; Hyung Tak; (Seoul,
KR) ; Lee; Yeong An; (Tongyeong, KR) ;
Kalanur; Shankara S.; (Suwon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company
Kia Motors Corporation
Ajou University Industry-Academic Cooperation Foundation |
Seoul
Seoul
Suwon |
|
KR
KR
KR |
|
|
Family ID: |
56178241 |
Appl. No.: |
15/138325 |
Filed: |
April 26, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B05D 5/065 20130101;
B01J 23/62 20130101; B01J 23/6482 20130101; G01N 21/783 20130101;
B01J 23/8906 20130101; B01J 37/035 20130101; C01P 2006/40 20130101;
B01J 23/892 20130101; B01J 23/30 20130101; B01J 37/34 20130101;
B01J 23/58 20130101; B01J 23/8926 20130101; B01J 35/023 20130101;
B01J 37/343 20130101; B01J 23/6527 20130101; B05D 3/067 20130101;
B01J 23/60 20130101; B01J 37/345 20130101; B01J 23/626 20130101;
C01G 41/02 20130101; G01N 27/04 20130101; G01N 33/005 20130101;
B01J 23/44 20130101; F01N 2560/024 20130101; B01J 35/008 20130101;
B01J 35/002 20130101; B01J 23/6525 20130101 |
International
Class: |
G01N 33/00 20060101
G01N033/00; G01N 27/04 20060101 G01N027/04; C01G 41/02 20060101
C01G041/02; G01N 21/78 20060101 G01N021/78 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2015 |
KR |
10-2015-0123830 |
Claims
1. A chemochromic nanoparticle, comprising: a core comprising a
transition metal oxide; and a shell comprising a metal catalyst
partially coated on a surface of the core.
2. The chemochromic nanoparticle according to claim 1, wherein the
transition metal oxide comprises a non-hydrated transition metal
oxide which is not doped with water molecules or a hydrated
transition metal oxide which is doped with water molecules.
3. The chemochromic nanoparticle according to claim 1, wherein the
transition metal oxide comprises a metal oxide of one or two or
more selected from the group consisting of SnO.sub.2, TiO.sub.2,
ZnO, VO.sub.2, In.sub.2O.sub.3, NiO, MoO.sub.3, SrTiO.sub.3,
Fe.sub.2O.sub.3, WO.sub.3, and CuO.
4. The chemochromic nanoparticle according to claim 1, wherein the
transition metal oxide comprises tungsten oxide (WO.sub.3).
5. The chemochromic nanoparticle according to claim 1, wherein an
average particle size of the transition metal oxide ranges from
about 1 to about 200 nm.
6. The chemochromic nanoparticle according to claim 1, wherein the
metal catalyst comprises one metal or particles of two or more
metals selected from the group consisting of Pd, Pt, Ru, Mg, Au,
and Ir.
7. The chemochromic nanoparticle according to claim 1, wherein the
metal catalyst comprises one or two or more metal compounds
selected from the group consisting of palladium chloride
(PdCl.sub.2), palladium ammonium nitrate
(Pd(NH.sub.3).sub.2(NO.sub.3)), palladium bromide (PdBr.sub.2),
palladium oxide hydrate (PdOH.sub.2O), palladium sulfate
(PdSO.sub.4), palladium nitrate (Pd(NO.sub.3).sub.2), palladium
acetylacetate ((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Pd),
platinum chloride (PtCl.sub.2, PtCl.sub.4), platinum bromide
(PtBr.sub.2), platinum oxide (PtO.sub.2xH.sub.2O), platinum sulfide
(PtS.sub.2), ruthenium oxide hydrate (RuO.sub.2xH.sub.2O),
ruthenium acetylacetate
[(CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ru], ruthenium bromide
(RuBr.sub.3), iridium chloride (IrCl.sub.3), iridium acetylacetate
((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ir), and iridium
chloride hydrate (IrCl.sub.4xH.sub.2O).
8. The chemochromic nanoparticle according to claim 1, wherein the
metal catalyst comprises palladium chloride (PdCl.sub.2).
9. The chemochromic nanoparticle according to claim 1, wherein the
shell comprising the metal catalyst is formed using a solution
synthesis method using UV irradiation.
10. The chemochromic nanoparticle according to claim 1, wherein a
thickness of the shell comprising the metal catalyst ranges from
about 0.1 to about 50 nm.
11. The chemochromic nanoparticle according to claim 1, wherein the
shell is partially coated on the surface of the core in a dot
form.
12. The chemochromic nanoparticle according to claim 1, wherein the
chemochromic nanoparticle comprises: the cored in an amount of
about 80 to 90 wt % and the shell in an amount of about 10 to 20 wt
% based on the total weight of the chemochromic nanoparticle.
13. A method for manufacturing a chemochromic nanoparticle, the
method comprising: preparing a hydrated or non-hydrated transition
metal oxide; preparing a metal catalyst solution by dissolving a
metal catalyst precursor and a polymer compound in an organic
solvent; preparing a mixed solution by adding the hydrated or
non-hydrated transition metal oxide to the metal catalyst solution;
manufacturing the chemochromic nanoparticle with a core-shell
structure by irradiating UV light to the mixed solution; and
obtaining the chemochromic nanoparticle by filtering the mixed
solution, wherein the chemochromic nanoparticle is formed in a
core-shell structure.
14. The method according to claim 13, wherein the polymer compound
comprises one or a mixture of two or more selected from the group
consisting of polyurethane, polyetherurethane, cellulose acetate,
cellulose acetate butyrate, cellulose acetate propionate,
polymethylmethacrylate (PMMA), polymethylacrylate (PMA),
polyacrylic copolymers, polyvinylacetate (PVAc), polyvinylacetate
copolymers, polyvinylalcohol (PVA), polystyrene, polystyrene
copolymers, polyethyleneoxide (PEO), polypropyleneoxide (PPO),
polyethyleneoxide copolymers, polycarbonate (PC), polyvinylchloride
(PVC), polycaprolactone, polyvinylpyrrolidone (PVP),
polyvinylfluoride, polyvinylidene fluoride copolymers, and
polyamide.
15. The method according to claim 13, wherein the organic solvent
comprises an alcohol based solvent.
16. The method according to claim 13, wherein the irradiating of
the UV light is performed by exposure to the UV light having a
wavelength of about 365 nm, at room temperature for about 2 to 3
minutes and an output of the UV light is of about 1000 W.
17. A hydrogen sensor comprising: a chemochromic nanoparticle of
claim 1; and at least one member selectively selected from the
group consisting of a polymer, aerogel, and a solvent.
18. A method for preparing a hydrated or non-hydrated tungsten
oxide, the method comprising: preparing an aqueous ammonium
paratungstate solution; adding hydrochloric acid to the aqueous
ammonium paratungstate solution and stirring the mixture to prepare
an aqueous tungstic acid solution; adding hydrogen peroxide to the
aqueous tungstic acid solution to prepare an aqueous
peroxo-polytungstic acid solution; injecting the aqueous
peroxo-polytungstic acid solution into an autoclave and performing
primary heat treatment; precipitating a hydrated tungsten oxide by
air-cooling the autoclave after a reaction is terminated; and
obtaining the tungsten oxide.
19. The method according to claim 18, wherein the primary heat
treatment is performed at a temperature of about 160.degree. C. in
the autoclave and an internal pressure in the autoclave is
maintained at about 35 to 50 bar.
20. The method according to claim 18, the method further
comprising: re-injecting the obtained tungsten oxide into the
autoclave; and performing a secondary heat treatment to the
tungsten oxide in the autoclave at a temperature of about
500.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on and claims the benefit of
priority to Korean Patent Application No. 10-2015-0123830, filed on
Sep. 1, 2015 in the Korean Intellectual Property Office, the
disclosure of which is incorporated herein in its entirety by
reference.
TECHNICAL FIELD
[0002] The present invention relates to a chemochromic
nanoparticle, a method for manufacturing the chemochromic
nanoparticle, and a hydrogen sensor comprising the chemochromic
nanoparticle. In particular, the chemochromic nanoparticle may have
a core-shell structure comprising a core of a hydrated or
non-hydrated transition metal oxide and a shell of a metal
catalyst.
BACKGROUND
[0003] Hydrogen fuel energy does not cause environmental
contamination and may be infinitely recyclable. Accordingly, the
hydrogen fuel energy has been newly spotlighted as a new generation
energy source capable of replacing petroleum energy. Therefore,
recently, research for storing and controlling the hydrogen fuel
energy has been actively conducted in various fields such as
production technologies, storage technologies, transportation and
movement technologies, and the like. Particularly, research into a
hydrogen fuel cell vehicle using the hydrogen fuel energy has been
most prominent.
[0004] However, hydrogen is combustible gas and having a risk of
ignition and explosion when a concentration of hydrogen in the air
is 4% or greater. Therefore, it is essential to strictly manage and
supervise hydrogen gas in all of the technical fields using the
hydrogen fuel energy. Among them, a core technology for
commercializing the hydrogen fuel energy may be implementing a
highly sensitive method for detecting hydrogen such that leakage of
hydrogen gas may be rapidly and accurately detected.
[0005] According to the related art, electric sensor devices
detecting hydrogen gas using the principles associated with
electrochemical, mechanical, acoustic, thermal conductivity, and
resistance changes and work functions have been used. However,
because these electric sensors detect the presence or absence of
leakage of hydrogen gas through a change in electrical resistance,
a package including a power supply part is required, such that most
of the sensors are not suitable for being used on a large scale due
to expensive cost, a large size, a complicated structure, and low
selectivity. In addition, since the sensors are used in an electric
environment in which the sensor may be exploded at the time of
detection operation, the sensors have a disadvantage of high
risk.
[0006] Recently, in order to overcome the disadvantages as
described above, a sensor using a method for chemically detecting
hydrogen gas using a material bleached or discolored when the
material is exposed to hydrogen has been suggested.
[0007] As a representative example of the material that can be
discolored in exposure to hydrogen, a transition metal oxide has
been known as a representative electrochromic material of which a
color is changed in the case of configuring an electrochemical cell
and applying an electric field thereto. Typically, change in color
of the transition metal oxide is caused by a change in electronic
structure due to electrochemical oxidation or reduction of a
transition metal when cations and electrons are injected.
[0008] Meanwhile, since hydrogen hardly reacts with a metal
material or semiconductor material, in order to solve this problem,
a metal catalyst, or the like, that may facilitate or induce a
reaction with hydrogen may be coated on the transition metal oxide,
such that reactivity with hydrogen may be significantly
increased.
[0009] As illustrated in FIG. 1, when hydrogen molecules in
hydrogen gas are dissociated into hydrogen ions (protons) and
electronics by the metal catalyst, and the hydrogen ion pass
through a metal catalyst layer to thereby be injected into a
transition metal oxide layer comprising the electrochromic material
below the metal catalyst layer by diffusion, a color of the
transition metal oxide can be changed (see the following Reaction
Formula 1). In this case, the presence or absence of hydrogen gas
may be detected by measuring transmittance of a thin film to
monitor a change in color. A phenomenon that the color of the thin
film is changed by gas is referred to as gasochromism.
Bleaching:
2W.sup.5++OH+1/2O.sub.2.fwdarw.2W.sup.6+=O+H.sub.2O(catalyzed by
Pt.sub.np)
Discoloration: W.sup.6++O+1/2H.sub.2.fwdarw.W.sup.5+-OH(catalyzed
by Pt.sub.np) (Reaction Formula 1)
[0010] The sensor using the method for chemically detecting
hydrogen gas as described above has advantages, for example,
long-distance detection using a cable may be performed, the sensor
may be repetitively used due to reversible change in color, and the
sensor does not require an additional electric circuit in a
detection region to thereby have high safety.
[0011] However, when the sensor is used for chemically detecting
hydrogen, since a sputtering method, a vapor deposition method, or
the like, in which high pressure is applied is used in order to
closely attach and adhere the metal catalyst to a surface of a
substrate (or the transition metal oxide). As such, bonding
strength between the metal catalyst layer and the transition metal
oxide layer may be increased, such that sensitivity with respect to
hydrogen gas may be decreased. Further, in the case in which metal
catalyst particles are not closely attached to the substrate, when
the metal catalyst particles are exposed to hydrogen gas, a lattice
of the metal catalyst particles may be expanded, but when exposure
to hydrogen gas is stopped, the lattice may not recovered in an
initial state, such that reproducibility may be decreased.
[0012] As described above, the hydrogen sensors according to the
related art may not be alternatives to the existing sensors in view
of detection capability, sensitivity, safety, a rapid response time
at a low concentration, and the like.
[0013] Therefore, a technology of manufacturing a high performance,
high life time, and high safety hydrogen detection sensor, capable
of being widely used over various industries, enabling visual
identification by using a hydrogen detection method, may have
excellent convenience in view of cost and a manufacturing process,
and does not cause a decrease in sensitivity, has been
required.
SUMMARY
[0014] In preferred aspects, the present invention provides a
chemochromic nanoparticle having a core-shell structure and having
substantially improved sensitivity and selectivity to hydrogen. The
term "chemochromic" or "chemochromic material" as used herein
refers to a material or compound that may change in color,
transmission/reflection properties, or optical properties. The
chemochromic material or compound may chemically react such that
the color, transmission/reflection properties, or optical
properties may be changed between before the reaction and after the
reaction, for example, electrochemical oxidation or reduction of a
transition metal or transition metal compound. Changes in color,
transmission or reflection properties, or optical properties may be
evaluated by, for example, a naked eye, a spectrophotometer, a
photodetector that converts light or optical signals into
electrical signals (impulses) or the like.
[0015] In addition, the present invention provides a method for
manufacturing the chemochromic nanoparticle with a core-shell
structure, and the method may be a simple manufacturing method for
the chemochromic nanoparticle as described above. Moreover, the
present invention provides a hydrogen sensor which may visually
identify and have convenience in view of cost and a manufacturing
process by containing the chemochromic nanoparticle with a
core-shell structure.
[0016] According to an exemplary embodiment of the present
invention, a chemochromic nanoparticle may have a core-shell
structure. Accordingly, the chemochromic nanoparticle may comprise:
a core comprising a hydrated or non-hydrated transition metal
oxide; and a shell comprising a metal catalyst. The shell may be
entirely or partially coated on a surface of the core.
[0017] The transition metal oxide may comprise a non-hydrated
transition metal oxide which is not doped with water molecules or a
hydrated transition metal oxide which is doped with water
molecules.
[0018] The transition metal oxide may comprise a metal oxide of one
or two or more selected from the group consisting of SnO.sub.2,
TiO.sub.2, ZnO, VO.sub.2, In.sub.2O.sub.3, NiO, MoO.sub.3,
SrTiO.sub.3, Fe.sub.2O.sub.3, WO.sub.3, and CuO.
[0019] The transition metal oxide may preferably comprise tungsten
oxide (WO.sub.3).
[0020] An average particle size of the transition metal oxide may
suitably range from about 1 to about 200 nm.
[0021] The metal catalyst may suitably comprise one metal or
particles of two or more metals selected from the group consisting
of Pd, Pt, Ru, Mg, Au, and Ir.
[0022] The metal catalyst may comprise one or two or more metal
compounds selected from the group consisting of palladium chloride
(PdCl.sub.2), palladium ammonium nitrate
(Pd(NH.sub.3).sub.2(NO.sub.3)), palladium bromide (PdBr.sub.2),
palladium oxide hydrate (PdOH.sub.2O), palladium sulfate
(PdSO.sub.4), palladium nitrate (Pd(NO.sub.3).sub.2), palladium
acetylacetate ((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Pd),
platinum chloride (PtCl.sub.2, PtCl.sub.4), platinum bromide
(PtBr.sub.2), platinum oxide (PtO.sub.2xH.sub.2O), platinum sulfide
(PtS.sub.2), ruthenium oxide hydrate (RuO.sub.2xH.sub.2O),
ruthenium acetylacetate
[(CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ru], ruthenium bromide
(RuBr.sub.3), iridium chloride (IrCl.sub.3), iridium acetylacetate
((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ir), and iridium
chloride hydrate (IrCl.sub.4xH.sub.2O).
[0023] The metal catalyst may preferably comprise palladium
chloride (PdCl.sub.2).
[0024] The shell comprising the metal catalyst may be formed using
a solution synthesis method using UV irradiation.
[0025] A thickness of the shell comprising the metal catalyst may
suitably range from about 0.1 to about 50 nm.
[0026] Preferably, the shell may be partially coated on the surface
of the core in a dot form.
[0027] The term "partially coated" as used herein means being
coated in a portion of a total surface area, for example, of about
10% or less, of about 20% or less, of about 30% or less, of about
40% or less, of about 50% or less, of about 60% or less, of about
70% or less, of about 80% or less, of about 90% or less, or of
about 95% or less of the total surface area. For example, the shell
of the nanoparticle may be coated on about 10% or less, of about
20% or less, of about 30% or less, of about 40% or less, of about
50% or less, of about 60% or less, of about 70% or less, of about
80% or less, of about 90% or less, or of about 95% or less of the
total surface area of the core.
[0028] In a preferred aspect, the chemochromic nanoparticle may
comprise: the cored in an amount of about 80 to 90 wt % and the
shell in an amount of about 10 to 20 wt % based on the total weight
of the chemochromic nanoparticle.
[0029] According to an exemplary embodiment of the present
invention, a method for manufacturing a chemochromic nanoparticle
having a core-shell structure may comprise: preparing a hydrated or
non-hydrated transition metal oxide; preparing a metal catalyst
solution by dissolving a metal catalyst precursor and a polymer
compound in an organic solvent; preparing a mixed solution by
injecting the hydrated or non-hydrated transition metal oxide into
the metal catalyst solution; manufacturing a chemochromic
nanoparticle with a core-shell structure by irradiating UV light to
the mixed solution; and obtaining the chemochromic nanoparticle
with a core-shell structure by filtering the mixed solution.
[0030] The polymer compound may suitably comprise one or a mixture
of two or more selected from the group consisting of polyurethane,
polyetherurethane, cellulose acetate, cellulose acetate butyrate,
cellulose acetate propionate, polymethylmethacrylate (PMMA),
polymethylacrylate (PMA), polyacrylic copolymers, polyvinylacetate
(PVAc), polyvinylacetate copolymers, polyvinylalcohol (PVA),
polystyrene, polystyrene copolymers, polyethyleneoxide (PEO),
polypropyleneoxide (PPO), polyethyleneoxide copolymers,
polycarbonate (PC), polyvinylchloride (PVC), polycaprolactone,
polyvinylpyrrolidone (PVP), polyvinylfluoride, polyvinylidene
fluoride copolymers, and polyamide.
[0031] The organic solvent suitably may comprise an alcohol based
solvent such as methanol or ethanol.
[0032] The irradiating of the UV light may suitably be performed by
exposure to the UV light having a wavelength of about 365 nm at
room temperature for about 2 to 3 minutes, and an output of the UV
light may be about 1000 W.
[0033] The present invention also provides a method for preparing
the hydrated or non-hydrated tungsten oxide. The method may
comprise: preparing an aqueous ammonium paratungstate solution;
adding hydrochloric acid to the aqueous ammonium paratungstate
solution and stirring the mixture to prepare an aqueous tungstic
acid solution; adding hydrogen peroxide to the aqueous tungstic
acid solution to prepare an aqueous peroxo-polytungstic acid
solution; injecting the aqueous peroxo-polytungstic acid solution
into an autoclave and performing primary heat treatment;
precipitating a hydrated tungsten oxide by air-cooling the
autoclave after a reaction is terminated; and obtaining the
tungsten oxide.
[0034] In one specifically preferred system, the primary heat
treatment may be performed at a temperature of about 160.degree. C.
in the autoclave and an internal pressure in the autoclave is
maintained at about 35 to 50 bar.
[0035] The method may further comprise: re-injecting the obtained
tungsten oxide into the autoclave; and performing a secondary heat
treatment to the tungsten oxide in the autoclave at a temperature
of about 500.degree. C.
[0036] Further provided is a hydrogen sensor that may comprise the
chemochromic nanoparticle with a core-shell structure as described
herein.
[0037] Still further provided is a vehicle that may comprises a
hydrogen sensor comprising the chemochromic nanoparticle as
described herein. Other aspects of the present invention are
disclosed infra.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The above and other objects, features and advantages of the
present invention will be more apparent from the following detailed
description taken in conjunction with the accompanying
drawings.
[0039] FIG. 1 illustrates an exemplary hydrogen sensor in the
related arts.
[0040] FIG. 2 illustrates an exemplary method for preparing a
hydrated or non-hydrated transition metal oxide of Preparation
Example 1 according to an exemplary embodiment of the present
invention.
[0041] FIG. 3 illustrates an exemplary method for manufacturing an
exemplary chemochromic nanoparticle with a core-shell structure
comprising a hydrated or non-hydrated transition metal oxide
according to an exemplary embodiment of the present invention.
[0042] Left side image in FIG. 4 illustrates a result of an
exemplary hydrogen sensor containing an exemplary non-hydrated
transition metal oxide from Experimental Example 1 according to an
exemplary embodiment of the present invention before hydrogen
gasochromic test.
[0043] Right side image in FIG. 4 illustrates a result of an
exemplary hydrogen sensor containing an exemplary non-hydrated
transition metal oxide from Experimental Example 1 according to an
exemplary embodiment of the present invention after hydrogen
gasochromic test. Left side image in FIG. 5 illustrates a result of
an exemplary hydrogen sensor comprising an exemplary hydrated
transition metal oxide from Experimental Example 1 according to an
exemplary embodiment of the present invention before a hydrogen
gasochromic test.
[0044] Right side image in FIG. 5 illustrates a result of an
exemplary hydrogen sensor comprising an exemplary hydrated
transition metal oxide from Experimental Example 1 according to an
exemplary embodiment of the present invention after a hydrogen
gasochromic test.
[0045] FIG. 6 is a graph illustrating voltage-current response
results of an exemplary hydrogen sensor containing an exemplary
non-hydrated transition metal oxide from Experimental Example 2
according to an exemplary embodiment of the present invention.
[0046] FIG. 7 is a graph illustrating voltage-current response
results of an exemplary hydrogen sensor containing an exemplary
hydrated transition metal oxide from Experimental Example 2
according to an exemplary embodiment of the present invention.
DETAILED DESCRIPTION
[0047] The terminology used herein is for the purpose of describing
particular exemplary embodiments only and is not intended to be
limiting of the invention. As used herein, the singular forms "a",
"an" and "the" are intended to include the plural forms as well,
unless the context clearly indicates otherwise. It will be further
understood that the terms "comprises" and/or "comprising," when
used in this specification, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof. As used herein, the term "and/or" includes any and
all combinations of one or more of the associated listed items.
[0048] Unless specifically stated or obvious from context, as used
herein, the term "about" is understood as within a range of normal
tolerance in the art, for example within 2 standard deviations of
the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%,
5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated
value. Unless otherwise clear from the context, all numerical
values provided herein are modified by the term "about."
[0049] It is understood that the term "vehicle" or "vehicular" or
other similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles, plug-in
hybrid electric vehicles, hydrogen-powered vehicles and other
alternative fuel vehicles (e.g. fuels derived from resources other
than petroleum). As referred to herein, a hybrid vehicle is a
vehicle that has two or more sources of power, for example both
gasoline-powered and electric-powered vehicles.
[0050] Hereinafter, the present invention will be described in
detail. Terms and words used in the present specification and
claims are not to be construed as a general or dictionary meaning
but are to be construed as meaning and concepts meeting the
technical ideas of the present invention based on a principle that
the inventors can appropriately define the concepts of terms in
order to describe their own inventions in best mode.
[0051] In detail, according to an exemplary embodiment of the
present invention, provided is a chemochromic nanoparticle that may
have a core-shell structure, such that the chemochromic
nanoparticle may comprise a core comprising a hydrated or
non-hydrated transition metal oxide; and a shell comprising a metal
catalyst partially coated on a surface of the core. Preferably, the
shell maybe entirely or partially coated on the surface of the
core. For example, the shell may be coated on about 10%, 20%, 30%,
40%, 50%, 60%, 70%, 80%, 90%, 95% or 99% of the total surface area
of the core.
[0052] The transition metal oxide for the cored of the nanoparticle
may be a material of which a color may be chemically changed due to
reduction by a reaction with hydrogen molecules when the material
is exposed to hydrogen gas. Representative examples thereof may
include a metal oxide of one or two or more selected from the group
consisting of SnO.sub.2, TiO.sub.2, ZnO, VO.sub.2, In.sub.2O.sub.3,
NiO, MoO.sub.3, SrTiO.sub.3, Fe.sub.2O.sub.3, WO.sub.3, and CuO.
Preferably, the transition metal oxide may be tungsten oxide
(WO.sub.3).
[0053] The transition metal oxide may comprise particles that are
not doped with water molecules, that is, non-hydrated particles, in
order to be applied to a resistance type sensor. Alternatively, the
transition metal oxide may comprise a water molecule-doped hydrated
transition metal oxide in order to further improve chemochromic
sensitivity.
[0054] As an internal structure of the hydrated transition metal
oxide is changed due to the water molecules, a diffusion speed of
hydrogen molecules may be improved, such that the hydrated
transition metal oxide may provide an advantage, for example, color
change performance thereof may be substantially improved. On the
contrary, the color change performance of the non-hydrated
transition metal oxide may not be sufficient, but electric
responsibility of the non-hydrated transition metal oxide for
hydrogen may be significantly increased, such that the non-hydrated
transition metal oxide may also be used as a material of the
resistance type sensor.
[0055] The term "color change", as used herein, refers to a
chemical or optical discoloration that may be visibly observed by
naked eyes. In preferred embodiment, the "color change" may refer
to a change in visibly detectable colors which is induced by
chemical reaction such as reduction, oxidation and the like, with
the hydrogen. That is, there would be a visible color change (as
detected with naked eyes) of the metal oxide layer between 1)
before the metal oxide layer is exposed to the hydrogen; and 2) at
least about 1 second, about 5 seconds, about 10 seconds, about 20
seconds, about 30 seconds, about 40 seconds, about 50 seconds, or
about 60 seconds after the metal oxide layer is exposed to the
hydrogen. Further, the "color change" may be visibly detected with
naked eyes when the discoloration material in the metal oxide layer
in an amount of about 1 wt %, about 2%, about 3 wt %, about 4 wt %,
about 5 wt %, about 7 wt %, about 10 wt %, about 15 wt %, about 20
wt %, about 25 wt %, about 30 wt %, about 35 wt %, about 40 wt %,
about 50 wt %, about 60 wt %, about 70 wt %, about 80 wt %, about
90 wt %, about 99 wt %, or about 100 wt % based on the total weight
thereof is chemically reacted with the hydrogen.
[0056] In the nanoparticle with a core-shell structure according to
the present invention, an average particle size of the core
comprising the transition metal oxide may range from about 1 to 200
nm, or particularly of about 1 to 100 nm.
[0057] Further, in the nanoparticle with a core-shell structure
according to the present invention, the metal catalyst may cause a
decomposition reaction of the hydrogen molecules. For example, the
metal catalyst as used herein may include one metal or mixed
particles of two or more metals selected from the group consisting
of Pd, Pt, Ru, Mg, Au, and Ir, more specifically, one or two or
more metal catalysts selected from the group consisting of
palladium chloride (PdCl.sub.2), palladium ammonium nitrate
(Pd(NH.sub.3).sub.2(NO.sub.3)), palladium bromide (PdBr.sub.2),
palladium oxide hydrate (PdOH.sub.2O), palladium sulfate
(PdSO.sub.4), palladium nitrate (Pd(NO.sub.3).sub.2), palladium
acetylacetate ((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Pd),
platinum chloride (PtCl.sub.2, PtCl.sub.4), platinum bromide
(PtBr.sub.2), platinum oxide (PtO.sub.2xH.sub.2O), platinum sulfide
(PtS.sub.2), ruthenium oxide hydrate (RuO.sub.2xH.sub.2O),
ruthenium acetylacetate
[(CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ru], ruthenium bromide
(RuBr.sub.3), iridium chloride (IrCl.sub.3), iridium acetylacetate
((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ir), and iridium
chloride hydrate (IrCl.sub.4xH.sub.2O). Among them, palladium
chloride (PdCl.sub.2) containing palladium (Pd) metal particles,
which may increase sensitivity in addition to significantly
improving durability of a hydrogen sensor, may be preferably
used.
[0058] The shell comprising the metal catalyst may be uniformly
coated by a solution synthesis method using UV irradiation instead
of a general chemical bath deposition (CBD) method, dry deposition
method, or sputtering method. Therefore, inherent specific physical
properties of surfaces of the transition metal oxide particles may
be secured.
[0059] In addition, the chemochromic nanoparticle with a core-shell
structure according to the present invention may include: the core
comprising the hydrated or non-hydrated transition metal oxide in
an amount of about 80 to 90 wt %; and the shell comprising the
metal catalyst in an amount of about 10 to 20 wt %, based on the
total weight of the chemochromic nanoparticle.
[0060] When the content ratio of the core comprising the transition
metal oxide is greater than about 90 wt %, an amount of the metal
catalyst adsorbed in the transition metal oxide may be rapidly
decreased, such that hydrogen molecule decomposition efficiency may
be decreased. In addition, when the content ratio of the transition
metal oxide is less than about 80 wt %, change of the color to
exposure to hydrogen may not be sufficiently implemented.
[0061] A thickness of the shell comprising the metal catalyst may
range from about 0.1 to about 50 nm, or particularly from about 1
to about 30 nm. When the coating thickness of the shell is less
than about 0.1 nm, capability of dissociating hydrogen molecules
may be deteriorated. Preferably, the thickness of the shell may be
less than a diameter of the core.
[0062] Further, in order to increase sensitivity efficiency of the
transition metal oxide with respect to hydrogen gas, the shell may
be partially coated on the surface of the core in a dot form
instead of being coated on an entire surface of the core comprising
the transition metal oxide. For example, a coating area of the
shell may be of about 80% or less of the entire surface area of the
core. When the coating area of the shell is greater than about 80%,
since the shell is coated on the surface of the transition metal in
a film form instead of the dot form, a surface area of the metal
catalyst contacting hydrogen may be decreased, thereby decreasing
capability of decomposing hydrogen.
[0063] As described above, in the nanoparticles with a core-shell
structure according to the present invention, when the average
particle size of the core comprising the transition metal oxide, an
average thickness and coating area of the shell comprising the
metal catalyst, and the content ratio of the core and shell are all
within the above-mentioned ranges, the shell comprising the metal
catalyst may be distributed to a uniform thickness on the surface
of the core comprising the transition metal oxide. Therefore, a
hydrogen sensor having high sensitivity may be manufactured.
[0064] In addition, provided is a method for manufacturing a
chemochromic nanoparticle with a core-shell structure. The method
may comprise: preparing a hydrated or non-hydrated transition metal
oxide; preparing a metal catalyst solution by dissolving a metal
catalyst precursor and a polymer compound in an organic solvent;
preparing a mixed solution by adding the hydrated or non-hydrated
transition metal oxide to the metal catalyst solution;
manufacturing the chemochromic nanoparticle by irradiating UV light
to the mixed solution; and obtaining the chemochromic nanoparticle
by filtering the mixed solution. Accordingly, the thus formed
chemochromic nanoparticle may be formed to have a core-shell
structure.
[0065] Hereinafter, the method for manufacturing the chemochromic
nanoparticle with a core-shell structure according to the present
invention will be described in detail with reference to the
accompanying drawings.
[0066] FIG. 2 shows an exemplary method of preparing exemplary
hydrated or non-hydrated transition metal oxide particles according
to an exemplary embodiment of the present invention, and FIG. 3
show an exemplary method for manufacturing an exemplary
chemochromic nanoparticle with a core-shell structure, which may
include hydrated or non-hydrated transition metal oxide particles
according to an exemplary embodiment of the present invention.
[0067] Preferably, the method may provide a method of preparing a
tungsten oxide as shown in FIG. 2.
[0068] For example, the preparing of the hydrated or non-hydrated
transition metal oxide may comprise: preparing an aqueous ammonium
paratungstate solution (step (a)); adding hydrochloric acid to the
aqueous ammonium paratungstate solution and stirring the mixture to
prepare an aqueous tungstic acid solution (step (b) and step (c));
adding hydrogen peroxide to the aqueous tungstic acid solution to
prepare an aqueous peroxo-polytungstic acid solution (step (d));
injecting the aqueous peroxo-polytungstic acid solution into an
autoclave and performing primary heat treatment (step (e));
precipitating a hydrated tungsten oxide by air-cooling the
autoclave after a reaction is terminated (step (f)); and obtaining
the tungsten oxide (step (g)).
[0069] Preferably, the hydrated tungsten oxide may be represented
with WO.sub.3-0.33H.sub.2O.
[0070] In the preparing of the hydrated or non-hydrated transition
metal oxide, a concentration of the aqueous ammonium paratungstate
solution of step (a) may be of about 1 wt % based on the total
weight of the.
[0071] Further, in step (b) and step (c), a content ratio between
tungsten and hydrochloric acid in the aqueous ammonium
paratungstate solution may be of about 10:1 to 10:5. When the
content ratio of hydrochloric acid is greater than about 5 or less
than about 1, an ammonium group may not be appropriately separated,
such that tungstic acid may not be easily formed.
[0072] In addition, a content ratio between tungsten and hydrogen
peroxide in the aqueous tungstic acid solution of step (d) may be
of about 10:1 to 10:5.
[0073] Further, the preparing of the hydrated or non-hydrated
transition metal oxide may further include, after adding hydrogen
peroxide, stirring the aqueous tungstic acid solution for about 60
minutes until the aqueous tungstic acid solution becomes
transparent.
[0074] In addition, in the preparing of the hydrated or
non-hydrated transition metal oxide, the primary heat treatment of
step (a) may be performed at a temperature of about 160.degree. C.
for about 1.5 hours in an autoclave as an internal pressure inside
the autoclave may be maintained at about 35 to 50 bar.
[0075] The water molecule-doped transition metal oxide may be the
hydrated tungsten oxide (WO.sub.3-0.33H.sub.2O) and the hydrated
tungsten oxide may be prepared by a hydrothermal synthesis reaction
performed under high temperature and high pressure conditions as
described above.
[0076] Further, in the method according to the present invention, a
secondary heat treatment may be performed on the hydrated tungsten
oxide obtained in step (g), such that non-hydrated tungsten oxide
may be prepared (not illustrated).
[0077] In this case, the secondary heat treatment may be performed
at a temperature of about 500.degree. C. for about 2 hours after
re-injecting the hydrated tungsten oxide into the autoclave.
[0078] As described above, according to the present invention, the
hydrated or non-hydrated transition metal oxide may be formed at
high productivity and a particle size thereof may range from about
1 to about 200 nm, when the hydrothermal synthesis method is
used.
[0079] Further, as shown in FIG. 3, the method for manufacturing
the chemochromic nanoparticle with a core-shell structure according
to an exemplary embodiment of the present invention may be
performed using a solution synthesis method including irradiating
UV light. Hereinafter, the method for manufacturing chemochromic
nanoparticles with a core-shell structure according to the present
invention will be described.
[0080] For example, as shown in step (a) of FIG. 3, the metal
catalyst precursor may be added to the organic solvent in which the
polymer compound may be dissolved and subjected to sonication while
being stirred for about 2 hours, thereby preparing the metal
catalyst solution.
[0081] The metal catalyst precursor may include one metal or mixed
particles of two or more metals selected from the group consisting
of Pd, Pt, Ru, Mg, Au, and Ir. Preferably, the metal catalyst
precursor may include one or a mixture of two or more selected from
the group consisting of palladium chloride (PdCl.sub.2), palladium
ammonium nitrate (Pd(NH.sub.3).sub.2(NO.sub.3)), palladium bromide
(PdBr.sub.2), palladium oxide hydrate (PdOH.sub.2O), palladium
sulfate (PdSO.sub.4), palladium nitrate (Pd(NO.sub.3).sub.2),
palladium acetylacetate
((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Pd), platinum chloride
(PtCl.sub.2, PtCl.sub.4), platinum bromide (PtBr.sub.2), platinum
oxide (PtO.sub.2xH.sub.2O), platinum sulfide (PtS.sub.2), ruthenium
oxide hydrate (RuO.sub.2xH.sub.2O), ruthenium acetylacetate
[(CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ru], ruthenium bromide
(RuBr.sub.3), iridium chloride (IrCl.sub.3), iridium acetylacetate
((CH.sub.3COCH.dbd.C(O.sup.-)CH.sub.3).sub.3Ir), and iridium
chloride hydrate (IrCl.sub.4xH.sub.2O). In particular, the metal
catalyst precursor may include palladium chloride (PdCl.sub.2)
containing palladium (Pd) metal particles, which may increase
sensitivity in addition to significantly improving durability of a
hydrogen sensor.
[0082] In addition, the polymer compound may be used as an adhesive
and may improve compatibility between the transition metal oxide
particles and the metal catalyst particles thereby improve coating
efficiency. The polymer compound may include one or a mixture of
two or more selected from the group consisting of polyurethane,
polyetherurethane, cellulose acetate, cellulose acetate butyrate,
cellulose acetate propionate, polymethylmethacrylate (PMMA),
polymethylacrylate (PMA), polyacrylic copolymers, polyvinylacetate
(PVAc), polyvinylacetate copolymers, polyvinylalcohol (PVA),
polystyrene, polystyrene copolymers, polyethyleneoxide (PEO),
polypropyleneoxide (PPO), polyethyleneoxide copolymers,
polycarbonate (PC), polyvinylchloride (PVC), polycaprolactone,
polyvinylpyrrolidone (PVP), polyvinylfluoride, polyvinylidene
fluoride copolymers, and polyamide. Preferably, the polymer
compound may be polyvinylpyrrolidone (PVP).
[0083] The organic solvent may be a polar solvent, such as an
alcohol based solvent. Preferably, the organic solvent may be
methanol or ethanol.
[0084] A mixed ratio (wt %) between the metal catalyst precursor,
the polymer compound, and the organic solvent in the metal catalyst
solvent may be about 1:1 to 2:2 to 3, or particularly about
1:1.5:2.5.
[0085] The polymer compound (PVP) may be used as a capping agent in
the solution. For example, Pd.sup.2+ ions, which are the metal
catalyst, may be capped by the polymer compound (PVP), and as a
result, the Pd.sup.2+ ions may not be aggregated but may be easily
dispersed in the solution as particles.
[0086] When the content ratio of the polymer compound is greater
than about 2, since a large amount of Pd.sup.2+ ions are capped, a
size of Pd particles may be significantly decreased. As a result,
nanoparticles having a predetermined size or greater may not be
formed, such that a concentration of the metal catalyst solution
may not be adjusted suitably in a subsequent reaction step.
Further, when the content ratio of the polymer compound is less
than about 1, since an amount of the polymer compound (PVP) capping
the Pd.sup.2+ ions is reduced, at least a portion of the Pd
particles may have excessively increased sizes, and the other
portion of the Pd particles may have excessively reduced sizes,
such that the size of the Pd particles becomes significantly
non-uniform. The result may be confirmed from the fact that a color
of synthesized Pd may turn grey or white. Since coating efficiency
between the transition metal oxide particles and the metal catalyst
particles is deteriorated in the subsequent reaction step by the
influence as described above and thus an amount of the metal
catalyst particles coated on the surfaces of the transition metal
oxide particles is decreased, capability of dissociating hydrogen
atoms may be deteriorated.
[0087] As shown in step (b) of FIG. 3, the hydrated or non-hydrated
transition metal oxide may be added to the prepared metal catalyst
solution, thereby preparing the mixed solution.
[0088] The mixed ratio (wt %) between the metal catalyst precursor
and the hydrated or non-hydrated transition metal oxide may be
about 8:10 to 12.
[0089] When the mixed ratio (wt %) between the metal catalyst
precursor and the hydrated or non-hydrated transition metal oxide
is greater than about 8:12, the content of the core comprising the
transition metal oxide in the finally manufactured chemochromic
nanoparticle may be increased, but the content ratio of the shell
comprising the metal catalyst may be decreased, such that
responsibility for hydrogen gas may be decreased. Further, when the
mixed ratio (wt %) between the metal catalyst precursor and the
hydrated or non-hydrated transition metal oxide is less than about
8:10, the content of the core comprising the transition metal oxide
in the finally manufactured chemochromic nanoparticle may be
decreased, such that sufficient change in color may not be
obtained.
[0090] As shown in step (c) and step (d) of FIG. 3, the
chemochromic nanoparticles with a core-shell structure are
manufactured by irradiating UV light to the mixed solution
containing the metal catalyst precursor and the hydrated or
non-hydrated transition metal oxide.
[0091] When the metal catalyst precursor and the transition metal
oxide are mixed with each other, the color of the mixed solution
may become light yellow, but when UV light is irradiated thereto,
as the metal ions in the mixed solution may be dissociated, the
mixed solution may be changed into an opaque grey solution. It may
be appreciated from the change in color as described above that a
synthesis reaction of the chemochromic nanoparticles is
completed.
[0092] The irradiating of the UV light may be performed by exposure
to UV light having a wavelength of about 365 nm and an output of
about 1000 W at room temperature for about 2 to 3 minutes. When a
UV irradiation time is within about 2 minutes, the Pd molecules may
not be appropriately decomposed, and when the UV irradiation time
is greater than about 3 minutes, a color of the separated Pd
molecules may become excessively dark, such that a visual change in
color for detecting hydrogen gas may not be suitably observed.
[0093] In addition, the thickness of the shell comprising the metal
catalyst may be adjusted and controlled depending on the UV
irradiation time and the concentration of the mixed solution. For
example, the UV irradiation time may be suitably adjusted depending
on the concentration of the mixed solution.
[0094] As described above, according to the present invention, the
metal catalyst precursor, for example, PdCl.sub.2 precursor may be
separated into Pd molecule and Cl.sub.2 by performing an
eco-friendly UV photochemical method, that is, the UV irradiation
process. The separated Pd molecule may react with the surface of
the transition metal oxide particle, thereby forming the shell
comprising the metal catalyst on the surface of the transition
metal oxide particles in a dot form.
[0095] Subsequently, in the method according to the present
invention, after the reaction is terminated, as shown in step (e)
of FIG. 3, the mixed solution may be filtered and dried, such that
the chemochromic nanoparticles with a core-shell structure may be
obtained.
[0096] Further provided is a hydrogen sensor comprising the
chemochromic nanoparticle manufactured by the method according to
the present invention.
[0097] Moreover, the hydrogen sensor may be provided, and the
hydrogen sensor may further selectively contain a polymer, aerogel,
and a solvent. Further, in the hydrogen sensor according to the
present invention, at the time of chemochromism due to exposure to
hydrogen, a change in color in a visible light region may be
significantly increased by injecting specific impurity molecules.
For example, molecules having a large electronegativity such as
--OH, --F, --Cl, or the like may be added to an original
composition of the transition metal oxide to adjust a crystalline
structure and an optical band gap.
[0098] In according to various exemplary embodiments of the present
invention, the chemochromic nanoparticle with a core-shell
structure manufactured by the method according to the present
invention may be applied in various fields. For example, after the
chemochromic nanoparticles may be combined with a polymer or
aerogel to thereby be prepared as a coating agent, a dye, paint, or
a pigment, and the coating agent, the dye, the paint, or the
pigment may be used as a chemochromic hydrogen sensor.
Alternatively, after the chemochromic nanoparticles with a
core-shell structure are mixed with a suitable solvent to thereby
be prepared as ink, and the ink is transferred/deposited on paper,
a porous media substrate, or the like, may be used as a hydrogen
sensor having excellent mechanical safety.
[0099] As described above, since the hydrogen sensor according to
the present invention may be manufactured in a room temperature
process, a manufacturing cost may be significantly decreased, and a
production yield may be significantly increased. In addition, the
hydrogen sensor may be applied to both an optical sensor and a
chemochromism/discoloration type sensor, and it may be easy to form
a large-area hydrogen sensor. Particularly, since the hydrogen
sensor according to the present invention does not require a
protective filter or passivation layer decreasing sensitivity or
selectivity, which is applied to a surface of a hydrogen sensor
according to the related art, deterioration of the sensitivity may
be decreased, such that a detection limit concentration of hydrogen
capable of being measured may be of about 1% or less, for example,
of about 0.8% in the air.
[0100] Hereinabove, the present invention has been described in
connection with various exemplary embodiments. However, various
modifications can be made without departing from the scope of the
present invention. Therefore, technical ideas of the present
invention should not be limited to the exemplary embodiments
described above but be defined by the appended claims and their
equivalents.
EXAMPLE
Experimental Method and Equipment
[0101] a. A color change reaction of 1% hydrogen (in 99% air
balance gas (N.sub.2, H.sub.2O, O.sub.2)) was observed under a
mixed atmosphere of nitrogen, oxygen, and water vapor using an open
chamber having an outlet.
[0102] b. All gasochromic tests were performed at room temperature,
and a flow rate of 2 L/min was maintained on a sample.
Preparation Example 1
Preparation of Hydrated Tungsten Oxide
[0103] After preparing 1 wt % of an aqueous ammonium paratungstate
solution by mixing ammonium paratungstate and water in a reactor,
an aqueous tungsten solution was prepared by adding 1.5 ml of
hydrochloric acid (HCl) thereto while stirring the aqueous
solution, and additionally stirring the mixed solution for 30
minutes.
[0104] Then, 3 ml of hydrogen peroxide was added to the aqueous
tungsten solution and stirred at room temperature for 60 minutes
until the mixed solution became transparent, thereby preparing an
aqueous peroxo-polytungstic acid solution.
[0105] The aqueous peroxo-polytungstic acid solution was injected
into an autoclave in which an internal pressure of 35 to 50 bar was
maintained, primary heat treatment was performed thereon at a
temperature of 160.degree. C. for about 1.5 hours.
[0106] After a reaction was terminated, the autoclave was
air-cooled to room temperature and a precipitate was filtered,
washed, and dried, thereby preparing water molecule-doped tungsten
oxide (WO.sub.3-0.33H.sub.2O).
Preparation Example 2
Preparation of Non-Hydrated Tungsten Oxide
[0107] The hydrated tungsten oxide prepared in Preparation Example
1 was re-injected into the autoclave and subjected to secondary
heat treatment at a temperature of about 500.degree. C. for 2
hours, thereby preparing non-hydrated tungsten oxide.
Example 1
Manufacturing of Nanoparticles for Hydrogen Sensor
[0108] Palladium chloride corresponding to a metal catalyst,
polyvinylpyrrolidone corresponding to a polymer compound, and
methanol corresponding to an organic solvent were injected into a
reactor at a ratio of 1:1.5:2.5 (wt %) and subjected to sonication
while being stirred for about 2 hours.
[0109] Subsequently, after the non-hydrated tungsten oxide of
Preparation Example 2 was injected into the metal catalyst solution
(metal catalyst precursor:transition metal oxide=8:10 (wt %)), the
mixed solution was subjected to UV irradiation (wavelength: 365 nm,
output: 1000 W) within about 2 minutes while being stirred.
[0110] When a color of a reaction mixture solution was changed from
light yellow to opaque grey, the reaction was terminated, and a
precipitate was filtered and dried, thereby manufacturing
chemochromic nanoparticles with a core-shell structure.
Example 2
Manufacturing of Nanoparticles for Hydrogen Sensor
[0111] Chemochromic nanoparticles with a core-shell structure were
manufactured by the same method as in Example 1 except for using
the hydrated tungsten oxide of Preparation Example 1 instead of the
non-hydrated tungsten oxide of Preparation Example 2.
EXPERIMENTAL EXAMPLE
Experimental Example 1
Hydrogen Gasochromic Test
[0112] A color change reaction to hydrogen gas was observed with
the naked eyes while passing the chemochromic nanoparticles
manufactured in Examples 1 and 2 through 1% hydrogen gas
(containing 99% of nitrogen) under the air atmosphere in which
nitrogen, oxygen, and water vapor were mixed with each other in an
intact state in which the chemochromic nanoparticles were obtained
from a filter paper.
[0113] As a result, as shown in FIG. 4, the chemochromic
nanoparticles with a core-shell structure containing the
non-hydrated transition metal oxide of Example 1 had a turbid green
color before exposure to hydrogen gas, but after exposure to
hydrogen gas, the color of the chemochromic nanoparticles was
changed to deep green, such that hydrogen gas may be detected.
[0114] Further, as shown in FIG. 5, the chemochromic nanoparticles
with a core-shell structure containing the hydrated transition
metal oxide of Example 2 had an almost pale yellow color before
exposure to hydrogen gas, but after exposure to hydrogen gas, the
color of the chemochromic nanoparticles was changed to deep blue,
such that hydrogen gas may be detected.
Experimental Example 2
Voltage-Current Response of Hydrogen Sensor
[0115] After preparing inks by mixing the chemochromic
nanoparticles manufactured in Examples 1 and 2 with a solvent, the
inks were transferred on paper or a porous media substrate, thereby
manufacturing hydrogen sensors.
[0116] Then, voltage-current responses with respect to the hydrogen
sensors were measured, and as a result, it was confirmed that in
the sensor containing the chemochromic nanoparticles of Example 1,
a current was increased 100,000 times in a range of -10V to 10V as
illustrated in FIG. 6. That is, it was observed that after exposure
to hydrogen gas, the current was increased than that before
exposure to hydrogen gas.
[0117] Further, it was confirmed that in the sensor containing the
chemochromic nanoparticles of Example 2, a current was increased 10
times in a range of -10V to 10V as illustrated in FIG. 7. That is,
it was observed that after exposure to hydrogen gas, the current
was increased than that before exposure to hydrogen gas. These
changes indicate sensitivity of the hydrogen sensor according to
the present invention to hydrogen gas.
[0118] Particularly, as shown in the result, since in the sensor of
Example 1, a change in color was small, but the current was
significantly increased, the sensor of Example 1 may be excellent
as a material of a resistance type sensor, and since in the sensor
of Example 2, an increase in current was small, but the change in
color was significant, the sensor of Example 2 may be suitably used
in a chemochromic application field.
[0119] As described above, according to the exemplary embodiments
of the present invention, the hydrogen sensor of which hydrogen gas
detection efficiency characteristics are improved due to a specific
surface area significantly increased by containing the chemochromic
nanoparticles with a core-shell structure in which the metal
catalyst layer is partially coated on the surface of the hydrated
or non-hydrated transition metal oxide, manufactured by an
eco-friendly UV photochemical method may be manufactured.
[0120] Hereinabove, although the present invention has been
described with reference to exemplary embodiments and the
accompanying drawings, the present invention is not limited
thereto, but may be variously modified and altered by those skilled
in the art to which the present invention pertains without
departing from the spirit and scope of the present invention
claimed in the following claims.
* * * * *