Embed Size (px)
Citation preview
ORIGINAL PAPER
Effect of Gold Particle Size and Deposition Methodon the Photodegradation of 4-Chlorophenol by Au/TiO2
S. Oros-Ruiz • J. A. Pedraza-Avella •
C. Guzman • M. Quintana • E. Moctezuma •
G. del Angel • R. Gomez • E. Perez
Published online: 19 January 2011
� Springer Science+Business Media, LLC 2011
Abstract The photoactivity of TiO2 P25 modified by
surface-deposition of gold nanoparticles was investigated
trough the photocatalytic degradation of aqueous 4-Chlo-
rophenol (4-CP). The Au/TiO2 materials were prepared by
three methods: photodeposition, deposition–precipitation
(D–P) and colloidal deposition. Each preparation yields to
different particle size, distribution and properties of gold
nanoparticles. However, the photoactivity of these systems
depends mainly on the gold particle size. All the materials
fit well to a pseudo first order rate model and a relationship
between the kinetic rate and the resulting particle sizes was
found, which shows the importance of the nanoparticle size
in the photoactivity of the TiO2 modified by gold. The
optimal load was found to be 0.5 wt% Au/TiO2 for the
material prepared by D–P, since this material increased
the photoactivity degradation of commercial TiO2 in 80%.
Keywords Titanium dioxide � Gold nanoparticles �Photocatalysis � 4-chlorophenol
1 Introduction
In photocatalysis, the most common material used for the
photodegradation of organic pollutants in aqueous solu-
tions is the titanium dioxide semiconductor, due to its low
cost, chemical and physical stability, availability and no
toxicity. Recently it has been reported that metallic nano-
particles deposited on the TiO2 support improve the
photoactivity of this material. The interaction of metallic
nanoparticles with TiO2 induces modifications in the
electronic state of the solids, leading to important
enhancement of the photocatalytic activity [1]. It has been
reported that gold nanoparticles supported on the surface of
semiconductors present a great catalytic activity for several
reactions [2, 3]. They have also been applied for different
photocatalytic reactions since they increase the separation
of the hole-electron by acting as a sink of electrons, dis-
placing the absorption of light to the visible region and
modifying the surface of the catalyst [4–7]. The use of
noble metal nanoparticles have generated a great interest in
the recent years for many purposes as for catalysis, optical
devices, detection, purification, biosensors and photovol-
taic devices [8–20].
There are several strategies to perform the deposition of
nanoparticles on the TiO2, among the most common
methods to deposit gold nanoparticles on titania are:
S. Oros-Ruiz (&)
Doctorado Institucional en Ingenierıa y Ciencia de Materiales,
Universidad Autonoma de San Luis Potosı, Av. Manuel Nava
No. 6, Zona Universitaria, San Luis Potosı, SLP, Mexico
e-mail: [email protected]
J. A. Pedraza-Avella
Centro de Investigaciones en Catalisis (CICAT), Universidad
Industrial de Santander (UIS), Sede Guatiguara, Km. 2 vıa El
Refugio, 681011 Piedecuesta (Santander), Colombia
C. Guzman � G. del Angel � R. Gomez
Departamento de Quımica, Area de Catalisis, Grupo
ECOCATAL, Universidad Autonoma Metropolitana-Iztapalapa
(UAM-I), Av. San Rafael Atlixco No. 186, 09340 Mexico, DF,
Mexico
M. Quintana � E. Perez
Instituto de Fısica, Universidad Autonoma de San Luis Potosı,
Av. Manuel Nava No.6 Zona Universitaria, San Luis Potosı,
SLP, Mexico
E. Moctezuma
Facultad de Ciencias Quımicas, Universidad Autonoma de San
Luis Potosı, Av. Manuel Nava No. 6, Zona Universitaria, San
Luis Potosı, SLP, Mexico
123
Top Catal (2011) 54:519–526
DOI 10.1007/s11244-011-9616-y
photodeposition (PD), deposition–precipitation (D–P) and
colloidal deposition (CD). PD is a method that uses UV
light to excite TiO2 and thus generate electrons that promote
the reduction of Au on the titania surface. This method does
not use stabilizing agents and the metallic particles are
formed and deposited on the surface of the TiO2 in aqueous
solution. It requires several washes to eliminate chloride
ions and calcination is not necessary [21]. The D–P method
is commonly used for producing commercial Au catalysts,
in this method the surface of the support acts as a nucleating
agent, and the metal is strongly attached to the support. This
permits the gradual and homogeneous addition of hydroxide
ions throughout the whole solution by the reduction of the
metallic precursor with urea. The D–P method requires
washing and calcination [22]. Finally, the CD method
requires a metal precursor soluble in organic solvents, the
gold nanoparticles are then stabilized by long alkyl thiols
and the TiO2 is added to the solution of these capped
nanoparticles. The metallic nanoparticles are deposited by
weak interactions with the TiO2 support. The method also
requires calcination to remove the organic capping ligands
from the surface [23].
By using these three methods, in the present work we
expect to obtain different gold particle sizes, high metallic
dispersion on the substrate, and different particle shapes.
Our main interest is to evaluate the effect of the nanopar-
ticle deposition method on the photocatalytic behavior of
TiO2. The 4-CP is a model molecule of halogenated aro-
matics; they are used as solvents or reagents in industrial
processes, therefore they are common contaminants in
industrial waste waters [24]. 4-CP is a toxic and recalci-
trant compound that can not be mineralized by traditional
waste water treatment processes, and might be totally
mineralized by advanced oxidation processes as photoca-
talysis. Furthermore 4-CP has been used as a standard for
evaluating various experimental parameters in photocata-
lytic processes [25–27].
2 Experimental Methods
TiO2 Degussa P25 was used as semiconductor in all the
reported experiments. It showed a BET specific surface
area of 56 m2/g, an average particle size of 25 nm, a purity
of 97% and an anatase/rutile ratio of 80/20.
2.1 Photodeposition (PD)
A suspension containing 1 g of TiO2 in 100 mL of Milli-Q
distilled water was prepared in a cylindrical quartz reactor
with ultrasonic agitation for 30 min. HAuCl4 (Aldrich 30
wt%) was added to the suspension to reach the desired
gold loads on the TiO2 (0.25, 0.5, 1.0 and 1.5 wt%). It is
well known that the photocatalytic process involves the
generation of a free electron and a positive hole on the
surface of the semiconductor, they induce reactions of
reduction and oxidation that proceed at the same time. In
order to start the photoreduction of the metallic source, it
is required to provide a reactant to be oxidized; in this
case we used methanol (Caledon 99.8%) in a concentra-
tion 1 M in a final volume of 400 mL [28]. The quartz
reactor was then placed in dark conditions, and deoxy-
genated for 30 min with N2 flow (100 mL/min) in con-
tinuous stirring. The gold deposition was carried out under
constant stirring with UV–Vis radiation provided by four
lamps 15 W with a primary emission at 365 nm. The
solution was filtered after 1 h of irradiation, and the col-
lected material was washed 4 times with 100 mL of
Milli-Q water. The samples were stored at room temper-
ature in dark conditions in a desiccator.
2.2 Deposition–Precipitation (D–P)
This preparation was made in the absence of light. The
deposition of gold was performed with urea (J.T. Baker
99%) following the methodology reported elsewhere [29].
TiO2 (4 g) were dispersed in 100 mL of aqueous HAuCl4(Aldrich 30 wt%) solutions with concentrations corre-
sponding to Au loads of 0.25, 0.5, 1.0, and 1.5 wt% of the
support. Urea was added in a concentration 100 times
higher than that of the HAuCl4 concentration. The sus-
pension was heated at 80 �C and stirred for 8 h. The urea
decomposition led to a gradual rise in the pH of the solu-
tion from 2 to 8. After gold deposition, the solids were
filtered and washed 4 times with 100 mL of Milli-Q water
in order to remove chloride ions which are known to cause
particle sintering. The samples were dried at 80 �C for 12 h
and calcined in air flow (100 mL/min) at 300 �C for 4 h
[29]. The samples were stored at room temperature in dark
conditions in a desiccator.
2.3 Colloidal Deposition (CD)
For this method a metallic source was firstly prepared as
follows: The corresponding to 1 g of HAuCl4 (Aldrich 30
wt%) was dissolved in 50 mL of ethanol (Caledon 95%)
and degassed with N2 for 30 min. Then, a solution of
1.364 g of phosphine (Aldrich 99%) in 50 mL of ethanol,
previously deoxygenated with N2 was added. The reaction
mixture immediately became colorless and a white pre-
cipitate appeared. The mixture was stirred for 2 min and
the product was removed by filtration, washed with diethyl
ether (Fisher 99%) and dried in vacuum. This solid was
dissolved in 10 mL of dichloromethane (Merck 99%), and
60 mL of pentane (Aldrich 99%) were added at 4 �C
resulting in the formation of white needles of
520 Top Catal (2011) 54:519–526
123
chloro(triphenylphosphine)gold that are stable in air and
soluble in organic solvents [30]. The gold nanoparticles in
colloidal suspension were prepared by mixing the
chloro(triphenylphosphine)gold with 0.125 mL of dode-
canethiol (Aldrich 98%) in 50 mL of chloroform (Caledon
98%) forming a clear solution. Tert-butylamine-borane
(Aldrich 99%) was then added in a concentration 10 times
higher than the metallic source. The color of the mixture
gradually darkened and became purple. This synthesis was
made at room temperature and was left for 6 h in constant
agitation under dark conditions. The deposition of these
colloidal metallic particles on TiO2 was made by adding
the support to the solvent containing the gold nanoparticles.
The resulting slurry was decolorated while the color of the
oxide powder was darkened. The solution was stirred for
3 h and the powder was then centrifugated and dried for
12 h at 80 �C. The metallic nanoparticles in the as-pre-
pared metal oxide composites were capped by organic
thiols, these were removed by calcination, for 4 h in air
flow (100 mL/min) at 3008. Stucky et al. reported that after
the calcination, the organic capping ligands are decom-
posed and no sulfur is detected by XPS [31]. The samples
were stored at room temperature in dark conditions in a
desiccator.
2.4 Characterization
The amount of gold deposited was determined by means
of a SpectrAA 220-FS atomic absorption spectrometer.
The XRD was used to identify the TiO2 phases with a
Bruker D-8 Diffractometer using Cu Ka radiation at a step
of 0.03 degrees/min of 2h. The specific surface area was
determined by N2 adsorption using a Quantachrome
sorptometer apparatus. The specific surface areas (BET)
were calculated from the nitrogen adsorption–desorption
isotherms. The UV–Vis spectra of the materials were
obtained in a UV–Vis Diffuse Reflectance Spectropho-
tometer Varian Cary 100. Transmission electron micros-
copy (TEM) was performed in a JEOL JEM 1230 electron
microscope operated at 100 keV. Particle size distribu-
tions were determined by counting at least 200 particles.
Carbon monoxide temperature programmed desorption
(TPD) was carried out to evaluate the dispersion of the
metallic particles using a Chembet-3000 apparatus
equipped with a TCD detector. The sample was reacti-
vated under H2 flow at 300 �C for 1 h. Afterwards the
sample was cooled at room temperature and purged with
He flow for 15 min, then a gas mixture (5%CO/95%He)
was passed through the sample for 1 h. After this time the
sample was purged with He flow for 15 min. The sample
was heated up to 300 �C at a heating rate of 10 �C/min
under a constant He flow of 10 �C/min to induce the
desorption of carbon monoxide.
2.5 Evaluation of the Photocatalytic Activity
in the 4-Chlorophenol Degradation
The evaluation of the photocatalytic activity of the result-
ing materials was made for the degradation of 4-CP, and it
was monitored for a period of 6 h taking the TiO2 P25 as
reference. The reactions were carried out in a well mixed
heterogeneous batch reactor with a UV-PC mercury lamp
of primary emission at 254 nm. The temperature was sta-
bilized at 20 �C with a water recirculation bath connected
to the outer jacket of the reactor. Air was supplied to the
reactor at a constant rate of 100 mL/min using a mass flow
controller. In a typical experiment, the reactor was loaded
with 200 mg of the photocatalyst in 200 mL of 4-CP
solution (40 ppm). To assure the adsorption/desorption
equilibrium, the system was stirred in the dark for 1 h
before turning the UV light on. The progress of the reac-
tion was followed by measuring the disappearance of
the 4-CP as a function of time with a Cary UV–Vis
spectrophotometer.
3 Results and Discussion
The specific surface areas of the solids were obtained in
order to evaluate the modification of the surface due to the
deposition of the metal. The nitrogen adsorption/desorption
isotherms for the materials with the maximum load of gold
for the three preparations were obtained. The specific
surface area obtained for bare TiO2 was 56 m2/g. Degussa
P-25 consists of agglomerates of crystallites, and possess a
low porosity, the surface area is largely external to the
agglomerates and the pore volume measured is mainly
located between the agglomerates (interagglomerate pores)
[32]. The specific surface areas were 56, 46 and 55 m2/g
for the PD, D–P and CD materials respectively, at 1.5 wt%
of Au/TiO2. The BET areas were practically of the same
order in all the samples, which show that no significant
modification of the textural properties of the TiO2 support
were produced due to the deposition of the metal nano-
particles on its surface.
XRD spectra for the bare TiO2 and for the materials at
1.5 wt% Au were recorded. The presence of anatase and
rutile phases can be observed in the materials after gold
deposition. This indicates that no structural effect on the
substrate was made by the different treatments performed
during the gold deposition. The presence of gold is not
detected in the diffractograms since the gold load is very
low. However, the content of gold on the materials was
determined by atomic absorption obtaining a good agree-
ment with the nominal amount of gold on the substrate
(0.25, 0.50, 1.00 and 1.50%). The materials prepared by PD
reported 0.30, 0.60, 1.30 and 2.00 wt%, for the materials
Top Catal (2011) 54:519–526 521
123
prepared by D–P, 0.27, 0.54, 1.20 and 1.40 wt%, and
finally the materials prepared by CD reported 0.20, 0.55,
1.3 and 1.6 wt%.
The optical properties of TiO2 are usually modified by
the presence of gold nanoparticles on the surface. The
UV–Vis absorption spectra for the bare support and the
synthesized gold supported materials are presented in
Fig. 1. A significant enhancement of the absorption due to
plasmon surface resonance (PSR) at 550 nm is observed
due to the interaction of the metallic particles with the
incident light, when this oscillates in the electron conduc-
tion band of the metal, [33]. The band gap appears shifted
to the visible region on the Au/TiO2 samples. The forbid-
den energy levels (Eg) were determined for the TiO2 P25
and for the materials prepared with different gold contents
by diffusive reflectance spectroscopy. The obtained values
are shown in Fig. 2 where the Eg for the bare TiO2 is only
plotted as a reference with a dashed line. As expected, the
band gap is displaced to lower values for the Au/TiO2
semiconductors. The Eg values of the modified materials
are close to each other and it is difficult to establish a
general behavior. However, the Eg decreased for every case
where the deposition of gold was made, and at intermediate
Au contents (1.0 and 1.5 wt% of Au/TiO2), the materials
prepared by D–P showed the lowest Eg value while the
materials prepared by PD presented the highest value.
Kamat et al. [34] have reported that when the semicon-
ductor and metal nanoparticles are in contact the photo-
generated electrons are distributed from TiO2 to the Au
particles, and the transfer continues until the two systems
attain equilibrium. The electron accumulation increases the
Fermi level of Au to more negative potentials, and the
resultant Fermi level gets closer to the conduction band of
the semiconductor, which improves the charge distribution
of the system. Kamat also observed that small Au particles
induce larger shifts in the Fermi level than the large par-
ticles do. This might indicate that the particles obtained by
D–P are smaller than the particles obtained by the other
methods.
The size of the nanoparticles evidently an important
parameter in this discussion, but it is also important in
order to elucidate the effect of the different methods used
here on the photocatalytic activity. Figure 3 shows the
micrographs of the materials at contents of 1.5 wt% of
Au/TiO2 for each deposition method. This concentration
corresponds to the highest value of gold deposition, where a
higher contrast for the different deposition methods can be
seen. The images denote the presence of nanosized metallic
particles. The average diameters and standard deviations
were calculated after counting at least 200 of these particles.
The micrographs (Fig. 3) show some important differences
between the particles synthesized by the three depositions
methods: the particles deposited by the PD and CD pre-
sented large particle size and they are not as well distributed
on the support, whereas the particles deposited by the DP
method (Fig. 3a, c) presented smaller sizes and narrow size
particles, well defined and well distributed on the substrate
(Fig. 3b). The average particle size and the corresponding
standard deviations are plotted as functions of the gold load
in Fig. 4. The D–P method produced particles with smaller
sizes and standard deviations with respect to the other
methods since this deposition method is less sensible to the
variations in the metal load. Otherwise, the particles pre-
pared by CD presented particle size values from 6.8 to
9.3 nm, while the particles prepared by PD had larger
200 300 400 500 600 700 800
Abs
orba
nce
(a.u
.)
Wavelenght (nm)
PD
D-P
CD
TiO2
Fig. 1 UV-Vis diffusive reflectance of solids for bare TiO2 and TiO2
modified with gold nanoparticles by: PD, D–P and CD. The arrowpoint up the increase in gold load 0.25, 0.5, 1.0, and 1.5 wt% of
Au/TiO2
0.25 0.50 0.75 1.00 1.25 1.502.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
Eg
(eV
)
% Au
TiO2
PD
D-P
CD
Fig. 2 Variation of the Eg as a function of Au load. Dashed linerepresents Eg for bare TiO2
522 Top Catal (2011) 54:519–526
123
particle sizes from 7.5 to 12.1 nm and larger standard
deviations.
Another important parameter in the Au deposition is the
dispersion of the metallic particles on the surface of the
TiO2. All the materials analyzed by carbon monoxide TPD
studies indicated that CO is desorbed as a single peak at
temperatures below 100 �C. The results of carbon mon-
oxide desorption also indicated that bare TiO2 adsorbs a
considerable amount of the probe molecule. The amount
adsorbed on the support was subtracted from the amount of
CO chemisorbed on the Au/TiO2 materials under identical
conditions. It has been reported that there is a good
agreement between the mean particle size estimated by
TPD and the mean particle size obtained by TEM, for gold
contents of 2% [35], however, in our case, only those
materials with gold contents of 1.5% presented a good
Fig. 3 TEM images of materials at 1.5 wt% Au/TiO2 prepared by PD (3A), D–P (3B), and CD (3C)
Top Catal (2011) 54:519–526 523
123
agreement between dispersion obtained by TPD and mean
particle size obtained by TEM, probably this technique is not
sensitive enough to determine the dispersion of metal
nanoparticles of our catalysts with gold contents below 1.5
wt%. Therefore, the average particle sizes of the gold
nanoparticles, for all the catalysts were determined by TEM.
In Table 1 are presented the parameters obtained for the
prepared materials: average particle size, constant rate, and
% of 4-CP degraded at half life time. The activities of these
materials are presented in Fig. 5: PD (5A); D–P (5B), and
CD (5C). In the case of PD the material with the highest
activity was the one prepared with 0.25% Au/TiO2, which
improving the degradation rate of the TiO2 P25 in 60%, for
higher depositions (0.5, 1.0 and 1.5% Au/TiO2) in this
method a detrimental effect on the TiO2 activity is
observed. On the other hand, D–P method shows that for
0.25, 0.5 and 1.0% of Au/TiO2, the effect of commercial
TiO2 is improved even by 80% (for the loads of 0.5 and
0.25 0.50 0.75 1.00 1.25 1.500
2
4
6
8
10
12
14
Part
icle
Siz
e (n
m)
% Au
PD
D-P
CD
Fig. 4 Particle size as a function of the Au deposited on the TiO2
Table 1 Comparative results of the Au/TiO2 photocatalysts, gold
particle size, constant rate, % of 4-CP degraded at half life time
Au/TiO2 TEM Constant rate % 4-CP degraded
Catalysts (wt%) Dav (nm) 1/K0 (min) t = 120 min
TiO2 - - 169 52
PD 0.25 7.5 ± 0.9 66 82
PD 0.50 12.2 ± 2.0 556 20
PD 1.00 10.3 ± 1.4 244 36
PD 1.50 9.2 ± 1.0 257 39
D–P 0.25 7.6 ± 1.0 161 55
D–P 0.50 6.1 ± 0.4 39 96
D–P 1.00 6.5 ± 0.4 39 91
D–P 1.50 7.6 ± 0.5 196 51
CD 0.25 6.8 ± 0.9 79 74
CD 0.50 9.3 ± 1.4 159 46
CD 1.00 7.7 ± 0.8 156 59
CD 1.50 9.3 ± 1.0 294 36
0 50 100 150 200 250 300 350 4000.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5 TiO
2
0.25% Au/TiO 2
0.50% Au/TiO 2
1.00% Au/TiO 2
1.50% Au/TiO 2
- ln
(C
/C0)
time (min)
0 50 100 150 200 250 300 350 400
time (min)
0 50 100 150 200 250 300 350 400
time (min)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0 TiO2
0.25% Au/TiO 2
0.50% Au/TiO 2
1.00% Au/TiO 2
1.50% Au/TiO 2
-ln(
C/C
0)
TiO2
0.25% Au/TiO 2
0.50% Au/TiO 2
1.00% Au/TiO 2
1.50% Au/TiO 2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
-ln
(C/C
0)
A
B
C
Fig. 5 Plot of -ln(C/C0) as a function of time for materials prepared
by a PD; b D–P and c CD
524 Top Catal (2011) 54:519–526
123
1.0% Au/TiO2). These materials were the most effective in
the photodegradation of 4-CP of the three evaluated
deposition methods. The photoactivity of the materials
prepared by CD improved significantly at 0.25% Au/TiO2
(53%), and slightly modified with 0.5 and 1.0%. The load
of 1.5% Au/TiO2 was detrimental as in the other methods
used, which indicates that this amount is not effective for
photocatalytic purposes.
The straight lines in Fig. 6 indicate the fitting of the
photocatalytic degradation of 4-CP that show that it fol-
lows approximate first-order kinetics, even after the Au
nanoparticles deposition. This result can be understood in
terms of modified (for solid–liquid reactions) Langmuir–
Hinshelwood kinetics. The degradation was considered to
take place on the semiconductor surface and not on the
gold surface [36]. Gold nanoparticles deposition was very
low in all the cases, thus the mechanism of reaction is not
modified, however, the constant rate is effectively modified
as one can infer from the slope of the fitted line.
The UV light degradation of the 4-CP as a function of
the gold load on the TiO2 is plotted in Fig. 6. It is shown
the activity of TiO2 P25 as a reference, the materials pre-
pared by PD improved the activity of TiO2 only for the one
with 0.25 wt% of Au, those with higher loads produced
larger particle sizes and this conduced to a detrimental
effect. For the materials synthesized by CD, the activity
was improved for those with 0.25, 0.50 and 1.0 wt% Au.
The photoactivity of materials prepared by D–P, presented
a better growing control of the particles, and resulted in the
smaller particles at different loads of gold, which made
them the most active materials for the degradation of the
4-CP presenting a maximum in the activity for the material
at 0.5 wt of Au. It is very interesting to remark that Fig. 6
shows the same behavior that the dependence of the
nanoparticles size as function of the Au loaded (see Fig. 4).
This means that the activity of the materials depends on the
particle size of the metal.
In order to confirm the role of the gold nanoparticles
size, the graph of the inverse of the rate of degradation
(1/K0) as a function of the particle size is shown in Fig. 7.
It can be observed that the average size of the particle has a
strong effect on the degradation rate of the 4-CP. This last
holds despite the chemical modification of the TiO2 pro-
duced by the different deposition methods. It is clear that
the main parameter that rules the photodegradation by TiO2
modified with gold nanoparticles is the particle size.
4 Conclusions
From the results obtained in this work, it is clear that the
particle size exerts an effect of on the activity of the
materials in the photoactivity, beyond the deposition
method, the most important and ruling parameter is the
metal particle size. The materials prepared by D–P were
the most active in the photodegradation of 4-CP since the
particle growth is controlled and prevents the agglomera-
tion of gold, by distributing the metal along the surface and
controlling the size. The gold load on TiO2 also plays an
important role in the activity; the materials prepared by
D–P shows that 0.5 wt% of gold is the optimum to improve
the photodegradation up to 80%. All the materials with
loads of 1.5% of Au/TiO2 presented a detrimental effect on
the TiO2 photoactivity, so this load of metal is not efficient
for photocatalytical purposes. The Au/TiO2 photocatalysts
should posses gold particles with diameters below 8.6 nm
0.25 0.50 0.75 1.00 1.25 1.500
100
200
300
400
500
600
1/K
0 (m
in)
% Au
TiO2
PD D-P
CD
Fig. 6 Inverse of rate of degradation (1/K0) as a function of the Au
load on the TiO2
5 6 7 8 9 10 11 12 13 14 15
0
100
200
300
400
500
600
1/K
0 (m
in)
Particle size (nm)
Fig. 7 Inverse of rate of degradation (1/K0) of 4-CP as a function of
gold particle size. The continuous line is to guide the eye
Top Catal (2011) 54:519–526 525
123
in order to improve the photoactivity of the commonly used
TiO2.
Acknowledgments This project was partially supported by
PROMEP and CONACyT (Mexico) through grant No. 49482.
S. Oros-Ruiz thanks to CONACyT for the fellowship 213621
Granted.
References
1. Pileni MP (2005) Nanocrystals forming mesoscopic structures.
Wiley, Weinheim, Germany
2. Haruta M (2003) The chemical record 3:75–87
3. Haruta M (2004) Gold Bull 37:27–36
4. Salata OV (2004) J Nanobiotech 2:1–6
5. Alivisatos P (2004) Nat Biotech 22:47–52
6. Jakob M, Levanon H (2003) Nano Lett 3:353–358
7. Thompson D (2003) Appl Catal A: General 243:201–205
8. Sobana N, Muruganadham M, Swaminathan M (2006) J Mol
Catal A: Chem 258:124–132
9. Li XZ, Li FB (2001) Environ Sci Technol 35:2381–2387
10. Tian Y, Tatsuma T (2005) J Am Chem Soc 127:7632–7637
11. Haruta M (1997) Catal Today 36:153–166
12. Dawson A, Kamat PV (2001) J Phys Chem B 105:960–966
13. Narayanan R, El-Sayed M (2005) J Phys Chem B 109:12663–
12676
14. Wood A, Giersig M, Mulvaney P (2001) J Phys Chem B
105:8810–8815
15. Sivalingam G, Nagaveni K, Hedge MS, Madras G (2003) Appl
Catal B: Environ 45:23–38
16. Allmond CE, Oleshko VP, Howe JM, Fitz-Gerald JM (2006)
Appl Phys A 82:675–678
17. Tran H, Scott J, Chiang K, Amal R (2006) J Photochem Photobiol
A: Chem 183:41–52
18. Wang H, Wu Y, Xu BQ (2005) Appl Catal B: Environ
59:143–150
19. Orlov A, Jefferson D, Macleod N, Lambert RM (2004) Catal Lett
92:41–47
20. Rodrıguez-Gonzalez V, Zanella R, del Angel G, Gomez R (2008)
J Mol Catal A: Chem 281:93–98
21. Chan SC, Barteau MA (2005) Langmuir 21:5588–5595
22. Zanella R, Giorgio S, Henry CR, Louis C (2002) J Phys Chem B
106:7634–7642
23. Zheng N, Fan J, Stucky G (2006) J Am Chem Soc 128:6550–
6551
24. Cheng S, Tsai S, Lee Y (1995) Catal Today 26:87–96
25. Mills A, Wang J (1998) J Photochem Photobiol A: Chem
118:53–63
26. Li X, Cubbage JW, Tetzlaff TA, Jenks W (1999) J Org Chem
64:8509–8524
27. Guillard C, Disdier J, Herrmann JM, Lehaut C, Chopin T, Malato
S, Blanco J (1999) Catal Today 54:217–228
28. Bamwenda GR, Tsubota S, Nakamura T, Haruta M (1995) J
Photochem Photobiol A: Chem 89:177–189
29. Zanella R, Louis C (2005) Catal Today 107–108:768–777
30. Braunstein P, Lehner H, Matt D (1990) Inorg Synth 27:218–221
31. Zheng N, Stucky G (2006) J Am Chem Soc 128:14278–14280
32. Porter J, Li Y, Chan C (1999) J Mater Sci 34:1523–1531
33. Kamat PV (2007) J Phys Chem C 111:2834–2860
34. Kamat P (2002) J Phys Chem B 106:7729–7744
35. Guzman C, Del Angel G, Gomez R, Galindo F, Zanella R, Torres
G, Angeles-Chavez C, Fierro JLG (2009) J Nano Res 5:13–23
36. Pelizzetti E, Minero C (1993) Langmuir 9:2995–3001
526 Top Catal (2011) 54:519–526
123
