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A Surface Sol-Gel Process of TiO2 and Other Metal Oxide Films with Molecular Precision

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Molecular Imprinting of Azobenzene Carboxylic Acid on a TiO2 Ultrathin Film by the Surface Sol-Gel Process ... Nanoparticles in Ultrathin TiO2-Gel ... – PowerPoint PPT presentation

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Title: A Surface Sol-Gel Process of TiO2 and Other Metal Oxide Films with Molecular Precision


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A Surface Sol-Gel Process of TiO2 and Other Metal
Oxide Films with Molecular Precision
oxotitanium acetylacetonate (TiO(acac)2)
????(acac)
Chem. Mater. 1997, 9, 1296-1298
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The film density is estimated as 1.6 g/cm3 from
the thickness and the total frequency shift (5221
Hz). This value is close to the bulk density of
TiO2- based gel prepared by conventional methods.
6
Adv. Mater. 1998, 10, 535
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Layered Nanocomposite of Close-Packed Gold
Nanoparticles and TiO2 Gel Layers
Chem. Mater. 1999, 11, 33-35
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Platinum 2nm Au particles ca. 5-8 nm
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UV-vis spectra of the layer-by-layer assembly of
gold nanoparticles and TiO2 layer on a quartz
substrate. Broken line after the formation of
TiO2 gel layer. One cycle of TiO2 contains 15
cycles of the surface sol-gel process.
Solid line after immersion of the substrate into
the methanol dispersion of gold nanoparticles.
Au atom ) 1.5? 10-3 mol dm-3, at room
temperature.
12
Molecular Imprinting of Azobenzene Carboxylic
Acid on a TiO2 Ultrathin Film by the Surface
Sol-Gel Process
(1) Mixtures of 100mMTi(O-nBu)4 and 25mM(or 50
mM) C3AzoCO2H were dissolved in 21 (vol/vol)
mixtures of toluene and ethanol and stirred at
room temperature for more than 12 h. Complexation
of Ti(O-nBu)4 and C3AzoCO2H at this stage was
confirmed by FT-IR measurement after removal of
the solvents. (2) Subsequently, water (275 mM
for 25 mM template solution and 350 mM for 50 mM
template solution) was added (2.75 and 3.5 times,
respectively, relative to Ti alkoxide), and the
mixtures were aged for one to several hours. The
complete reaction of the three components in the
25 mM template solution will produce
Ti4O4(OH)4(O-Bu)4C3AzoCO2H.
Langmuir 1998, 14, 2857-2863
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In order to remove the bound template molecule,
surface gel films prepared on quartz plates were
treated with1 aqueous ammonia for 30 min, washed
thoroughly with ethanol and ion-exchanged water,
and dried by flushing with N2 gas.
UV-vis absorption spectral change due to
adsorption of the Ti(O-nBu)4/C3AzoCO2H complex.
15
In situ QCM frequency decreases due to rebinding
of the template molecule to the imprinted films
of sample 3 (Table 1). Five microliters of 50 mM
C3AzoCO2H in THF was added into 1 mL of CH3CN at
the time marked with an arrow to give a C3AzoCO2H
concentration of 0.25 mM.
In situ QCM frequency decreases due to binding of
a series of carboxylic acids. Imprinted film,
sample 3 in Table 1. Conditions of in situ
experiments are identical to those of Figure 4.
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Field Effect Transistors
Normally, semiconductors don't have many free
electrons. Since electric current relies on those
free electrons, the amount of current that can
travel through an isolated semiconductor is
negligible. Put a slab of silicon, for example,
in the middle of a circuit and it will stop the
current in its tracks. But things change if you
put an electric field near that silicon. Bringing
a positively-charged metal plate up close will
attract the negatively-charged electrons from
inside the body of the semiconductor. These
electrons stream to the surfacesuddenly there is
an abundance of free electrons creating a pathway
for the blocked current. Where once there was a
stopped passage, electricity can now flow. By
controlling the voltage on the metal plate, you
can easily flip the current through the
semiconductor on and off. On top of that, the
current traveling through the semiconductor will
be an exact replica of the signal sent to the
metal plateonly larger. The transistor has
amplified the original signal. Since this
transistor depends on an electric field, it's
known as a Field Effect transistor.
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Tailored Chemosensors for Chloroaromatic Acids
Using Molecular Imprinted TiO2 Thin Films on
Ion-Sensitive Field-Effect Transistors
Anal. Chem.2001, 73,720-723
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Tailored Chemosensors for Chloroaromatic Acids
Using Molecular Imprinted TiO2 Thin Films on
Ion-Sensitive Field-Effect Transistors
Anal. Chem.2001, 73,720-723
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About Oxygen Plasma Treatment
The Machine
Plasma is an excited low pressure gas, which can
be used for surface treatment and critical
cleaning applications. Ions and electrons in the
plasma react with the surface of materials, which
results in removal of organic contamination as
well as chemical modification of the surface.
Excited Gas Species Atoms (O) Molecules
(O3) Ions (O, O-, O2, O2-, ionized ozone)
Electrons Free radicals Metastables
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SiCl4 dissolved in CCl4
Adv. Mater. 2003, 15, 780.
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Nano-Precision Replication of Natural Cellulosic
Substances by Metal Oxides
Figure 1. Titania replicas of natural cellulosic
substances. Deposition of titania thin films was
repeated 20 times for each sample. (a) Field
emission scanning electron micrograph (FE-SEM) of
titania paper, showing titania nanotube
assemblies. The inset shows the photograph of a
sheet of titania paper. (b) and (c)
Transmission electron micrographs (TEM) of
individual titania nanotubes isolated from the
assembly. Inset of (b), selected-area electron
diffraction (SAED) pattern from the nanotube
assembly. Inset of (c), schematic illustration of
the boxed area, showing titania nanotube wall is
composed of fine anatase particles. (d) SEM image
of titania cloth. (e)SEM image of titania
cotton.
J. AM. CHEM. SOC. 2003, 125, 11834-11835
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Figure 2. Electron micrographs of zirconia
paper. Deposition of zirconia thin films was
repeated 20 times for this sample. (a) FE-SEM
image, showing zirconia nanotube assemblies. (b)
and (c) TEM images of an individual zirconia
nanotube isolated from the assembly.
24
A General, Efficient Method of Incorporation of
Metal Ions into Ultrathin TiO2 Films
In a typical preparation of Mg2-templated
ultrathin films, 0.0114 g of Mg(O-Et)2 was
dissolved in 10 mL of 2-ethoxyethanol, with the
aid of an ultrasonic bath and stirring for 5
days. Ti(O-nBu)4 (0.3531 mL) was then added with
stirring, and the mixture was stirred further for
1 h. The composition of the mixed solution was 10
mM Mg(O-Et)2 and 100 mM Ti(O-nBu)4.
Chem. Mater. 2002, 14, 3493-3500
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XPS spectra of Mg2-templated TiO2 thin films (a)
before and (b) after removal of Mg2 and (c)
after incorporation of Ba2 ions 10 mM aqueous
Ba(NO3)2, 4-h immersion time. The inset shows
the expanded spectrum between 500 and 400 eV. The
three spectra agree exactly.
26
Incorporation of various metal ions into
Mg2-templated TiO2 thin films (51 nm), as
estimated from QCM frequency changes divided by
atomic mass (10 mM aqueous metal ion nitrate,
20-min immersion time, room temperature).
27
In Situ Synthesis of Noble Metal Nanoparticles in
Ultrathin TiO2-Gel Films by a Combination of
Ion-Exchange and Reduction Processes
Preparation of silver nanoparticles in TiO2
ultrathin films. (a) Absorption spectra of an
Ag-doped TiO2 film during exposure to H2 plasma.
(b,c) TEM images of Ag nanoparticles in TiO2 thin
films (inset in Figure 1c, electron diffraction).
Langmuir 2002, 18, 10005-10010
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Size dependent on H2 plasma power
(a) Absorption spectra of Ag-doped TiO2 films
after 150 s exposures to H2 plasma of 4, 17, and
28 W. (b,c) TEM histograms of the size
distribution obtained at 4 W (b) and 28 W (c) of
the plasma power.
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Preparation of nanoparticles of other noble metal
elements in TiO2 thin films. (a-c) Absorption
spectra of (a) AuCl3-, (b) Pd2-, and (c)
PtCl4-doped TiO2 films during exposure to H2
plasma. (d-f) TEM images of (d) Au, (e) Pd, and
(f) Pt nanoparticles in TiO2 thin films.
30
Facile Fabrication of Ag-Pd Bimetallic
Nanoparticles in Ultrathin TiO2-Gel Films
Nanoparticle Morphology and Catalytic Activity
Unique features expected for multimetallic
nanoparticles may include (1) physical and
chemical interactions among different atoms and
phases that lead to novel functions (2) altered
miscibility and interactions unique to nanometer
dimension (macroscopic phase property may not
apply) (3) morphological variations that are
related to new properties.
As specific examples, gold-palladium (14) and
platinum palladium (14) core-shell nanoparticles
show higher catalytic activities than the
corresponding mixture of the monometallic
nanoparticles for selective hydrogenation of
cycloocta-1,3-diene to cyclooctene and for
hydrogenation of 4-pentenoic acid (4-???),
J. AM. CHEM. SOC. 2003, 125, 11034-11040
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Preparation of Pd-on-Ag Bimetallic Nanoparticles
in TiO2-Gel Films
Preparation of Pd-on-Ag core-shell bimetallic
nanoparticles in TiO2 thin film by sequential
incorporation/reduction of Ag and Pd2 ions (up)
and corresponding UV-visible spectra of the thin
film (below) (a) after 4 h immersion in aqueous
AgNO3 (10 mM) (b) after exposure to H2 plasma of
10 w for 150 s (c) after 4 h immersion in
aqueous Pd(NO3)2 (10 mM) and (d) after exposure
to H2 plasma of 10 w for 5 s.
32
TEM image (a), histogram (b), and magnified image
(c) of Pd-on-Ag core-shell bimetallic
nanoparticles in TiO2-gel film prepared by
sequential incorporation/reduction of Ag and
Pd2 ions, and (d) simplified cross-section model.
33
Catalytic Activity of Pd-on-Ag Bimetallic
Nanoparticles
The catalytic activity of the Pd-on-Ag bimetallic
nanoparticle in TiO2 thin film was evaluated for
hydrogenation of methyl acrylate, and compared
with that of Pd monometallic nanoparticle
(average diameter, 5.0 1.9 nm) in TiO2 film and
commercial Pd black (Wako Pure Chem). Under
identical conditions, the catalytic activity of
the commercial palladium black, as estimated from
the initial rate, was measured to be 0.0045
mol?H2 mol ? Pd-1 s-1. In contrast, the catalytic
activity of the monometallic Pd nanoparticle was
estimated to be 1.05 mol ? H2 mol ? Pd-1 s-1, 233
times as large as that of the commercial
palladium black. When the Pd-on-Ag bimetallic
nanoparticle was tested, The catalytic activity
was estimated to be 1.65 mol?H2 mol ? Pd-1 s-1.
It is 367 times as large as that of the
commercial palladium black and 1.6 times as large
as that of the monometallic Pd nanoparticle.
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Representative morphologies of bimetallic
nanoparticles.
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2. A Facile Layer-by-Layer Adsorption and
Reaction Method to the Preparation of Metal
Phosphate Films Preparation and Functionalization
36
Schematic illustration of the stepwise growth of
titanium phosphate ultrathin films
? PS 0.1 M phosphate (Na2HPO4 and NaH2PO4) with
its pH adjusted by the addition of H2SO4.
Sun JQ, et al Chem. Mater. 2005, 17, 3563-3569.
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Multilayer deposition monitored by UV-Vis
absorption spectroscopy and QCM measurements
? The frequency decrease for one layer of
titanium phosphate deposition was 253.5 ? 3.8 Hz.
Ti(HPO4)2!
38
Structural Characterization of Titanium Phosphate
Films
Thickness 15-layer, 54.17.2 nm, 3.60.5 nm/layer
Particle diameter 22.13.8 nm
The surface (a) and sectional (b) SEM images of
titanium phosphate film.
_at_ Film preparative condition 10 mM Ti(SO4)2
dissolved in 0.1 M H2SO4 (pH 0.95), pH of PS
solution 4.0)
? 1-layer film thickness can be tuned between
0.89.6 nm!
39
Superhydrophilic titanium phosphate surface
Glass 10.52 PDDA modified glass 15.58
(Ti/PS)3 modified glass 0
40
Generality of the layer-by-layer adsorption and
reaction method to prepare other kinds of
inorganic phosphate films
Fe(NO3)2 FePO4
Zr(SO4)2 Zr(HPO4)2
41
Titanium phosphate/prussian blue composite films
Langmuir 2007, 23, 6084-6090
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TiPS/PB composite films monitored by UV-Vis
absorption spectroscopy and QCM measurements
43
Film Structure Characterization
30 bilayers
SEM images of (TiPS/PB)n films with n being 5
(a), 5.5 (b), 15 (c), and 30 (d). The scale bars
in all images correspond to 200 nm.
44
Electrochemical Properties of the TiPS/PB
Composite Films
? Thickness 111.014.2 nm for 15-bilayer TiPS/PB
and 93.518.4 nm for 15-layer PB film.
45
Catalytic properties of (TiPS/ PB)5 film to the
reduction of H2O2
High stability and facilitated electron transfer
in TiPS/PB composite films was realized!
0.1M KCl - 0.1M PBS (pH6.0), -100mV.
46
Scheme of Ion Exchange and In Situ Synthesis
Nanoparticles
Chem. Mater. 2006, 18, 1988-1994.
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Chemical Composition
XPS spectra of titanium phosphate film after
silver ions exchanged for 24 h at 50 C. (a)
before and (b) after Ar etching.
The atomic ratio of P to Ag was determined to be
11.5
48
Ag-ion Exchanged Titanium Phosphate Film as
Antibacterial Coatings
? Colonies of E. coli incubated on agar plates
getting from the cultivated suspensions with
(Control) and without (Sample) silver
ion-exchanged titanium phosphate film.
? Silver-ion-exchanged titanium phosphate film
with a thickness of 39 nm has the ability to
inhibit the growth of Escherichia Coli (E. coli).
49
Incorporation of water-insoluble and
water-soluble Ruthenium dyes into Zirconium
Phosphate Ultrathin Film
?
?
Rubpy
Langmuir 2008, 24, 11684-11690
50
Rubyp-incorporated zirconium phosphate films
Process
51
Rudpy-incorporated zirconium phosphate films
Process
Rudpp
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Rudpp_at_ZrPS films as Oxygen and Humidity Sensor
Top-down and cross-sectional SEM images.
Toward humidity
(Rudpp_at_ZrPS-ol)20 film
Toward oxygen
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