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Preparation of porous titania thin film and its photocatalytic activity
Applied Surface Science 255 (2008) 3137–3140
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Preparation of porous titania thin film and its photocatalytic activity Yanhui Ao a,b,c, Jingjing Xu a,b,c, Degang Fu a,b,c,*, Chunwei Yuan a,b a
School of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096, China State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China c Key Laboratory of Environmental and Bio-Safety in Suzhou, Research Institute of Southeast University, Dushu Lake Hogher Education Town, Suzhou 215123, China b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 2 June 2008 Received in revised form 31 August 2008 Accepted 31 August 2008 Available online 9 September 2008
In this study, different titania films were prepared by a sol–gel spin-coating technique. By introducing nanocarbon spheres into the precursor solution, porous titania film was prepared after calcination at a temperature of 500 8C for 3 h. The as-prepared porous titania film was characterized by XRD, BET, TEM and SEM. The photocatalytic property of the prepared porous film was evaluated by degrading X-3B under UV irradiation. Results showed that photocatalytic performance of as-prepared porous film was much higher than that of smooth titania and P25 films. ß 2008 Elsevier B.V. All rights reserved.
Keywords: Porous film Photocatalysis Titania Carbon spheres Spin-coating
1. Introduction Anatase-phase titania has attracted extensive attention during the last few decades due to its excellent photocatalytic properties [1–5]. However, TiO2 with high photoactivity and a significant quantum effect is commonly in nanometer size. The problem of separation and recovery of photocatalyst from the reaction medium exists, which enhances the overall capital and running cost of the treatment. Aggregation of photocatalyst would also decrease its photocatalytic activity in slurry system. So immobilized photocatalyst is more suitable for the practical application of titania photocatalysis, which has been given high attention in recent years. However, there is another problem that limitation of mass transfer often occurs [6] and activity of immobilized titania system is lower than slurry system. In order to improve photocatalytic performance, efforts have been made to increase the number of attainable surface activation sites by making porous mirostructure [7–12]. In this study, we investigated the feasibility of preparing porous titania films using nanocarbon spheres pore-forming materials by a sol–gel spin-coating method. The photocatalytic properties of
* Corresponding author at: School of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096, China. Tel.: +86 25 83794310; fax: +86 25 83793091. E-mail addresses: [email protected] (Y. Ao), [email protected] (D. Fu). 0169-4332/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2008.08.102
these films were evaluated by degrading Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under UV light irradiation. 2. Experimental 2.1. Preparation of carbon spheres In a typical synthesis of colloidal carbon spheres, 6 g of glucose was dissolved in 60 mL of water to form a clear solution. The solution was then sealed in a 50-mL Teflon-lined autoclave and maintained at 180 8C for 3 h. The products were then centrifuged, washed, and redispersed in water and ethanol for five cycles, respectively. Afterwards, the formed carbon spheres were then dried at 80 8C for 2 h under vacuum. 2.2. Preparation of porous titania film The titania precursor sols were prepared by sol–gel method at low temperature. The detailed process has been reported in previous papers [13,14]. In order to obtain porous microstructure, 0.05 g of carbon spheres were added into 100 mL titania sols. After being dispersed by ultrasonic, the carbon spheres/titania suspension was spin-coated on rectangular glass substrates (30 mm 20 mm 1 mm). The spin-coated film was dried at room temperature for 30 min, heated in the vacuum oven at 50 8C for 2 h, and then calcined at 500 8C in air for 3 h. In order to compare the photocatalytic activity, pure TiO2 film and P25 film was also prepared by the same method without the addition of carbon spheres.
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2.3. Characterization The structure properties were determined by X-ray diffractometer (XD-3A, Shimadazu Corporation, Japan) using graphite monochromatic copper radiation (Cu Ka) at 40 kV, 30 mA over the 2u range 20–808. The morphologies were characterized by transmission electron microscopy (TEM, JEM2000EX) and with a scanning electron microscopy (SEM, Sirion200, FEI). BET surface area measurements were carried out by N2 adsorption at 77 K on an ASAP2020 instrument using 30 pieces of glass substrates (20 mm 5 mm) coated with the film on both sides, since the weight of a single layer film on a substrate was too small to be measured. The concentration of X-3B was analyzed using the UV– vis spectrophotometer (Shimadzu UV-2100) at 535 nm. 2.4. Photocatalysis The photocatalytic activity of as-prepared porous film was studied by the degradation of Brilliant Red dye X-3B (C.I. reactive red 2) in aqueous solution, while pure titania and P25 films were used for comparison. A batch photoreactor system was used in experiments. It consists of a cylindrical silica reactor with glass plate at the bottom, and an external light source with vertical irradiation. A 200-W ultraviolet lamp with a wavelength peak at 365 nm was used as light source with average radiation intensity of 9 mW cm 2. A set of photocatalytic degradation experiments were performed with the following procedure: a piece of glass plate (30 mm 20 mm 1 mm) with sample film was dipped into 10 mL of X-3B solution with an initial concentration of 50 mg L 1. Prior to photoreaction, air was pumped into reactor in the dark for 30 min to reach adsorption–desorption equilibrium. Then, with continuous pump, the reaction was irradiated by the ultraviolet lamp from the top vertically. During the photoreaction, samples were collected at a time interval of every 20 min for analysis.
Fig. 2. N2 adsorption–desorption isotherm and pore size distribution curve (inset) of as-prepared porous titania film.
The X-ray diffraction (XRD) analysis pattern in Fig. 1 shows the titania phases formed at temperature 500 8C. The fact that the peaks are very narrow, indicate that the titania particles of the porous film are crystalline. As also shown in the figure, the particles had formed anatase-phase since the characteristic diffraction peaks of anatase (major peaks: 25.48, 38.08, 48.08,
54.78, and 63.18) were evident in the sample. The calcination at 500 8C not only removed the carbon spheres, but also enhanced the degree of crystallization of titania. The crystal size of the titania determined by Scherrer’s equation are estimated to be 9.5 nm. From the BET measurement, specific surface area of the porous titania film, smooth titania film and P25 film are 253, 124 and 31 m2 g 1, respectively. And the pore volume of the two films are 0.27, 0.18 and 0.10 cm3 g 1. Fig. 2 shows the typical plot of nitrogen adsorption–desorption isotherm and pore size distribution (inset) of the porous film. It can be seen that the sample shows an isotherms with hysteresis loop, clearly indicating the porous structure of the film. The corresponding pore size distribution plot of the porous film exhibits a wide pore size distribution ranged from 5 to 125 nm. The pores with diameter less than 50 nm may be formed by the aggregation of titania particles. And the pores centered at about 103 nm are considered to form as the result of combustion of carbon spheres during heat treatment. Thermal properties of the as-prepared carbon spheres were investigated by thermogravimetric analysis, the corresponding results are shown in Fig. 3. It can be seen that complete removal of carbon spheres can be accomplished at temperatures of about 440 8C. Thus the calcination temperature of 500 8C can be used to prepare porous titania films. The TEM image of carbon spheres is shown in Fig. 4(a). It can be seen from the figure that diameter of
Fig. 1. XRD patterns of as-prepared porous titania film.
Fig. 3. Thermogravimetric analysis curve of the carbon spheres.
3. Results and discussion 3.1. Characterization of the porous titania film
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Fig. 5. Kinetics of X-3B degradation in the presence of porous titania film and smooth titania and P25 film.
Fig. 4. (a) TEM image of carbon spheres and (b) SEM image of the porous titania film.
as-prepared carbon spheres ranges from 150 to 200 nm. Fig. 4(b) shows the SEM image of the prepared porous film. It can be seen that porous structure was attained after the calcination. Furthermore, we can see that the film is macroporous film with a mean pore size of about 100 nm.
Fig. 6. Linear transform ln(C0/C) = f(t) of the kinetic curves of X-3B degradation for porous titania film and smooth titania and P25 film from Fig. 3.
3.2. Photocatalytic activity of the porous titania film In order to investigate the photocatalytic activity of as-prepared porous titania film, degradation experiments of Reactive Brilliant Red X-3B (C.I. reactive red 2) were studied under UV light and results are shown in Fig. 5. The blank experiment without catalysts was also investigated. And the value can be neglected with about 2% of conversion after 2 h irradiation. From the figure, we can see that the degradation ratio of X-3B by porous film is much higher than the other two smooth films. For convenient comparison of photocatalytic activity of different films, apparent rate constant has been chosen as the basic kinetic parameter, since it enables one to determine a photocatalytic activity independent of the previous adsorption period in the dark and the concentration of X-3B remaining in the solution. The apparent first order kinetic equation ln(C0/C) = kappt is used to fit experimental data, where kapp is apparent rate constant, C is the solution-phase concentration of X-3B, and C0 is the initial concentration at t = 0 [15]. The variations in ln(C0/C) as a function of irradiation time are given in Fig. 6. The obtained apparent rate constants kapp are listed in Table 1. From the data we can see that kapp of porous film is nearly three times as that of other
Table 1 Degradation parameter of X-3B by different samples Samples
Smooth P25 film Smooth titania film Porous titania film
X-3B degradation percent (%)
Apparent rate constant kapp (min
51 49 89
0.0057 0.0051 0.0166
R 1
) 0.9948 0.9991 0.9969
smooth films. It is known that photocatalytic activity increases with increasing surface activation sites where X-3B containing solution can be in close contact with the titania film. The porous structure can provide more surface activation sites for photocatalytic reaction. Therefore, the porous titania film shows higher photocatalytic activity than smooth titania film and P25 film. 4. Conclusions Porous titania film was prepared by a simple method. Firstly, nanocarbon spheres were synthesized by hydrothermal method using glucose as precursor. The carbon spheres were used as pore-
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forming materials by a sol–gel coating technique. The photocatalytic property of the prepared porous film was evaluated by degrading X-3B under UV irradiation. Results showed that photocatalytic performance of as-prepared porous film was much higher than that of corresponding smooth films. Acknowledgements This work was supported by the National Natural Science Foundation of China (No. 60121101) and Joint Project of Guangdong Province and Education Department (No. 2007A090302018). References [1] J.G. Yu, H.G. Yu, B. Cheng, X.J. Zhao, J.C. Yu, W.K. Ho, The effect of calcination temperature on the surface microstructure and photocatalytic activity of TiO2 thin films prepared by liquid phase deposition, J. Phys. Chem. B 107 (2003) 13871–13879. [2] J.C. Zhao, T.X. Wu, K.Q. Wu, K. Oikawa, H. Hidaka, N. Serpone, Photoassisted degradation of dye pollutants 3. Degradation of the cationic dye Rhodamine B in aqueous anionic surfactant/TiO2 dispersions under visible light irradiation: evidence for the need of substrate adsorption on TiO2 particles, Environ. Sci. Technol. 32 (1998) 2394–2400. [3] Y.M. Xu, C.H. Langford, UV- or visible-light-induced degradation of X3B on TiO2 nanoparticles: the influence of adsorption, Langmuir 17 (2001) 897–902. [4] A. Fujishima, K. Honda, Electrochemical photolysis of water at a semiconductor electrode, Nature 238 (1972) 37–38.
[5] H. Tada, M. Yamamoto, S. Ito, Promoting effect of MgOx submonolayer coverage of TiO2 on the photoinduced oxidation of anionic surfactants, Langmuir 15 (1999) 3699–3702. [6] D.W. Chen, A.K. Ray, Photocatalytic kinetics of phenol and its derivatives over UV irradiated TiO2, Appl. Catal. B 23 (1999) 143–157. [7] M. Takeshi, N. Kaori, S. Kazuyuki, K. Kazumi, Preparation of nanoporous TiO2 film with large surface area using aqueous sol with trehalose, Mater. Lett. 58 (2004) 2751–2753. [8] M. Takeshi, N. Kaori, S. Kazuyuki, K. Kazumi, Preparation of thick TiO2 film with large surface area using aqueous sol with poly(ethylene glycol), J. Mater. Sci. 39 (2004) 699–701. [9] H. Li, G.L. Zhao, B. Song, G.R. Han, Preparation of macroporous and mesoporous TiO2 film with various solvents, Mater. Lett. 62 (2008) 3395–3397. [10] A. Murakami, T. Yamaguchi, S. Hirano, K. Kikuta, Synthesis of porous titania thin films using carbonatation reaction and its hydrophilic property, Thin Solid Film 516 (2008) 3888–3892. [11] K. Wessels, M. Maekawa, J. Rathousky, T. Yoshida, M. Wark, T. Oekermann, Highly porous TiO2 films from anodically deposited titanate hybrids and their photoelectrochemical and photocatalytic activity, Micropor. Mesopor. Mater. 111 (2008) 55–61. [12] M. Gartner, P. Osiceanu, M. Anastasescu, T. Stoica, T.F. Stoica, C. Trapalis, T. Giannakopoulou, N. Todorova, A. Lagoyannis, Investigation on the nitrogen doping of multilayered, porous TiO2 thin films, Thin Solid Film 516 (2008) 8184– 8189. [13] Y.H. Ao, J.J. Xu, D.G. Fu, X.W. Shen, C.W. Yuan, Low temperature preparation of anatase TiO2-activated carbon composite film, Appl. Surf. Sci. 254 (2008) 4001– 4006. [14] Y.H. Ao, J.J. Xu, D.G. Fu, X.W. Shen, C.W. Yuan, Low temperature preparation of anatase TiO2-coated activated carbon, Colloid Surf. A 312 (2008) 125–130. [15] J. Matos, J. Laine, J.M. Herrmann, Synergy effect in the photocatalytic degradation of phenol on a suspended mixture of titania and activated carbon, Appl. Catal. B: Environ. 18 (1998) 281–291.
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Preparation of porous titania thin film and its photocatalytic activity Yanhui Ao a,b,c, Jingjing Xu a,b,c, Degang Fu a,b,c,*, Chunwei Yuan a,b a
School of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096, China State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China c Key Laboratory of Environmental and Bio-Safety in Suzhou, Research Institute of Southeast University, Dushu Lake Hogher Education Town, Suzhou 215123, China b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 2 June 2008 Received in revised form 31 August 2008 Accepted 31 August 2008 Available online 9 September 2008
In this study, different titania films were prepared by a sol–gel spin-coating technique. By introducing nanocarbon spheres into the precursor solution, porous titania film was prepared after calcination at a temperature of 500 8C for 3 h. The as-prepared porous titania film was characterized by XRD, BET, TEM and SEM. The photocatalytic property of the prepared porous film was evaluated by degrading X-3B under UV irradiation. Results showed that photocatalytic performance of as-prepared porous film was much higher than that of smooth titania and P25 films. ß 2008 Elsevier B.V. All rights reserved.
Keywords: Porous film Photocatalysis Titania Carbon spheres Spin-coating
1. Introduction Anatase-phase titania has attracted extensive attention during the last few decades due to its excellent photocatalytic properties [1–5]. However, TiO2 with high photoactivity and a significant quantum effect is commonly in nanometer size. The problem of separation and recovery of photocatalyst from the reaction medium exists, which enhances the overall capital and running cost of the treatment. Aggregation of photocatalyst would also decrease its photocatalytic activity in slurry system. So immobilized photocatalyst is more suitable for the practical application of titania photocatalysis, which has been given high attention in recent years. However, there is another problem that limitation of mass transfer often occurs [6] and activity of immobilized titania system is lower than slurry system. In order to improve photocatalytic performance, efforts have been made to increase the number of attainable surface activation sites by making porous mirostructure [7–12]. In this study, we investigated the feasibility of preparing porous titania films using nanocarbon spheres pore-forming materials by a sol–gel spin-coating method. The photocatalytic properties of
* Corresponding author at: School of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096, China. Tel.: +86 25 83794310; fax: +86 25 83793091. E-mail addresses: [email protected] (Y. Ao), [email protected] (D. Fu). 0169-4332/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2008.08.102
these films were evaluated by degrading Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under UV light irradiation. 2. Experimental 2.1. Preparation of carbon spheres In a typical synthesis of colloidal carbon spheres, 6 g of glucose was dissolved in 60 mL of water to form a clear solution. The solution was then sealed in a 50-mL Teflon-lined autoclave and maintained at 180 8C for 3 h. The products were then centrifuged, washed, and redispersed in water and ethanol for five cycles, respectively. Afterwards, the formed carbon spheres were then dried at 80 8C for 2 h under vacuum. 2.2. Preparation of porous titania film The titania precursor sols were prepared by sol–gel method at low temperature. The detailed process has been reported in previous papers [13,14]. In order to obtain porous microstructure, 0.05 g of carbon spheres were added into 100 mL titania sols. After being dispersed by ultrasonic, the carbon spheres/titania suspension was spin-coated on rectangular glass substrates (30 mm 20 mm 1 mm). The spin-coated film was dried at room temperature for 30 min, heated in the vacuum oven at 50 8C for 2 h, and then calcined at 500 8C in air for 3 h. In order to compare the photocatalytic activity, pure TiO2 film and P25 film was also prepared by the same method without the addition of carbon spheres.
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2.3. Characterization The structure properties were determined by X-ray diffractometer (XD-3A, Shimadazu Corporation, Japan) using graphite monochromatic copper radiation (Cu Ka) at 40 kV, 30 mA over the 2u range 20–808. The morphologies were characterized by transmission electron microscopy (TEM, JEM2000EX) and with a scanning electron microscopy (SEM, Sirion200, FEI). BET surface area measurements were carried out by N2 adsorption at 77 K on an ASAP2020 instrument using 30 pieces of glass substrates (20 mm 5 mm) coated with the film on both sides, since the weight of a single layer film on a substrate was too small to be measured. The concentration of X-3B was analyzed using the UV– vis spectrophotometer (Shimadzu UV-2100) at 535 nm. 2.4. Photocatalysis The photocatalytic activity of as-prepared porous film was studied by the degradation of Brilliant Red dye X-3B (C.I. reactive red 2) in aqueous solution, while pure titania and P25 films were used for comparison. A batch photoreactor system was used in experiments. It consists of a cylindrical silica reactor with glass plate at the bottom, and an external light source with vertical irradiation. A 200-W ultraviolet lamp with a wavelength peak at 365 nm was used as light source with average radiation intensity of 9 mW cm 2. A set of photocatalytic degradation experiments were performed with the following procedure: a piece of glass plate (30 mm 20 mm 1 mm) with sample film was dipped into 10 mL of X-3B solution with an initial concentration of 50 mg L 1. Prior to photoreaction, air was pumped into reactor in the dark for 30 min to reach adsorption–desorption equilibrium. Then, with continuous pump, the reaction was irradiated by the ultraviolet lamp from the top vertically. During the photoreaction, samples were collected at a time interval of every 20 min for analysis.
Fig. 2. N2 adsorption–desorption isotherm and pore size distribution curve (inset) of as-prepared porous titania film.
The X-ray diffraction (XRD) analysis pattern in Fig. 1 shows the titania phases formed at temperature 500 8C. The fact that the peaks are very narrow, indicate that the titania particles of the porous film are crystalline. As also shown in the figure, the particles had formed anatase-phase since the characteristic diffraction peaks of anatase (major peaks: 25.48, 38.08, 48.08,
54.78, and 63.18) were evident in the sample. The calcination at 500 8C not only removed the carbon spheres, but also enhanced the degree of crystallization of titania. The crystal size of the titania determined by Scherrer’s equation are estimated to be 9.5 nm. From the BET measurement, specific surface area of the porous titania film, smooth titania film and P25 film are 253, 124 and 31 m2 g 1, respectively. And the pore volume of the two films are 0.27, 0.18 and 0.10 cm3 g 1. Fig. 2 shows the typical plot of nitrogen adsorption–desorption isotherm and pore size distribution (inset) of the porous film. It can be seen that the sample shows an isotherms with hysteresis loop, clearly indicating the porous structure of the film. The corresponding pore size distribution plot of the porous film exhibits a wide pore size distribution ranged from 5 to 125 nm. The pores with diameter less than 50 nm may be formed by the aggregation of titania particles. And the pores centered at about 103 nm are considered to form as the result of combustion of carbon spheres during heat treatment. Thermal properties of the as-prepared carbon spheres were investigated by thermogravimetric analysis, the corresponding results are shown in Fig. 3. It can be seen that complete removal of carbon spheres can be accomplished at temperatures of about 440 8C. Thus the calcination temperature of 500 8C can be used to prepare porous titania films. The TEM image of carbon spheres is shown in Fig. 4(a). It can be seen from the figure that diameter of
Fig. 1. XRD patterns of as-prepared porous titania film.
Fig. 3. Thermogravimetric analysis curve of the carbon spheres.
3. Results and discussion 3.1. Characterization of the porous titania film
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Fig. 5. Kinetics of X-3B degradation in the presence of porous titania film and smooth titania and P25 film.
Fig. 4. (a) TEM image of carbon spheres and (b) SEM image of the porous titania film.
as-prepared carbon spheres ranges from 150 to 200 nm. Fig. 4(b) shows the SEM image of the prepared porous film. It can be seen that porous structure was attained after the calcination. Furthermore, we can see that the film is macroporous film with a mean pore size of about 100 nm.
Fig. 6. Linear transform ln(C0/C) = f(t) of the kinetic curves of X-3B degradation for porous titania film and smooth titania and P25 film from Fig. 3.
3.2. Photocatalytic activity of the porous titania film In order to investigate the photocatalytic activity of as-prepared porous titania film, degradation experiments of Reactive Brilliant Red X-3B (C.I. reactive red 2) were studied under UV light and results are shown in Fig. 5. The blank experiment without catalysts was also investigated. And the value can be neglected with about 2% of conversion after 2 h irradiation. From the figure, we can see that the degradation ratio of X-3B by porous film is much higher than the other two smooth films. For convenient comparison of photocatalytic activity of different films, apparent rate constant has been chosen as the basic kinetic parameter, since it enables one to determine a photocatalytic activity independent of the previous adsorption period in the dark and the concentration of X-3B remaining in the solution. The apparent first order kinetic equation ln(C0/C) = kappt is used to fit experimental data, where kapp is apparent rate constant, C is the solution-phase concentration of X-3B, and C0 is the initial concentration at t = 0 [15]. The variations in ln(C0/C) as a function of irradiation time are given in Fig. 6. The obtained apparent rate constants kapp are listed in Table 1. From the data we can see that kapp of porous film is nearly three times as that of other
Table 1 Degradation parameter of X-3B by different samples Samples
Smooth P25 film Smooth titania film Porous titania film
X-3B degradation percent (%)
Apparent rate constant kapp (min
51 49 89
0.0057 0.0051 0.0166
R 1
) 0.9948 0.9991 0.9969
smooth films. It is known that photocatalytic activity increases with increasing surface activation sites where X-3B containing solution can be in close contact with the titania film. The porous structure can provide more surface activation sites for photocatalytic reaction. Therefore, the porous titania film shows higher photocatalytic activity than smooth titania film and P25 film. 4. Conclusions Porous titania film was prepared by a simple method. Firstly, nanocarbon spheres were synthesized by hydrothermal method using glucose as precursor. The carbon spheres were used as pore-
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forming materials by a sol–gel coating technique. The photocatalytic property of the prepared porous film was evaluated by degrading X-3B under UV irradiation. Results showed that photocatalytic performance of as-prepared porous film was much higher than that of corresponding smooth films. Acknowledgements This work was supported by the National Natural Science Foundation of China (No. 60121101) and Joint Project of Guangdong Province and Education Department (No. 2007A090302018). References [1] J.G. Yu, H.G. Yu, B. Cheng, X.J. Zhao, J.C. Yu, W.K. Ho, The effect of calcination temperature on the surface microstructure and photocatalytic activity of TiO2 thin films prepared by liquid phase deposition, J. Phys. Chem. B 107 (2003) 13871–13879. [2] J.C. Zhao, T.X. Wu, K.Q. Wu, K. Oikawa, H. Hidaka, N. Serpone, Photoassisted degradation of dye pollutants 3. Degradation of the cationic dye Rhodamine B in aqueous anionic surfactant/TiO2 dispersions under visible light irradiation: evidence for the need of substrate adsorption on TiO2 particles, Environ. Sci. Technol. 32 (1998) 2394–2400. [3] Y.M. Xu, C.H. Langford, UV- or visible-light-induced degradation of X3B on TiO2 nanoparticles: the influence of adsorption, Langmuir 17 (2001) 897–902. [4] A. Fujishima, K. Honda, Electrochemical photolysis of water at a semiconductor electrode, Nature 238 (1972) 37–38.
[5] H. Tada, M. Yamamoto, S. Ito, Promoting effect of MgOx submonolayer coverage of TiO2 on the photoinduced oxidation of anionic surfactants, Langmuir 15 (1999) 3699–3702. [6] D.W. Chen, A.K. Ray, Photocatalytic kinetics of phenol and its derivatives over UV irradiated TiO2, Appl. Catal. B 23 (1999) 143–157. [7] M. Takeshi, N. Kaori, S. Kazuyuki, K. Kazumi, Preparation of nanoporous TiO2 film with large surface area using aqueous sol with trehalose, Mater. Lett. 58 (2004) 2751–2753. [8] M. Takeshi, N. Kaori, S. Kazuyuki, K. Kazumi, Preparation of thick TiO2 film with large surface area using aqueous sol with poly(ethylene glycol), J. Mater. Sci. 39 (2004) 699–701. [9] H. Li, G.L. Zhao, B. Song, G.R. Han, Preparation of macroporous and mesoporous TiO2 film with various solvents, Mater. Lett. 62 (2008) 3395–3397. [10] A. Murakami, T. Yamaguchi, S. Hirano, K. Kikuta, Synthesis of porous titania thin films using carbonatation reaction and its hydrophilic property, Thin Solid Film 516 (2008) 3888–3892. [11] K. Wessels, M. Maekawa, J. Rathousky, T. Yoshida, M. Wark, T. Oekermann, Highly porous TiO2 films from anodically deposited titanate hybrids and their photoelectrochemical and photocatalytic activity, Micropor. Mesopor. Mater. 111 (2008) 55–61. [12] M. Gartner, P. Osiceanu, M. Anastasescu, T. Stoica, T.F. Stoica, C. Trapalis, T. Giannakopoulou, N. Todorova, A. Lagoyannis, Investigation on the nitrogen doping of multilayered, porous TiO2 thin films, Thin Solid Film 516 (2008) 8184– 8189. [13] Y.H. Ao, J.J. Xu, D.G. Fu, X.W. Shen, C.W. Yuan, Low temperature preparation of anatase TiO2-activated carbon composite film, Appl. Surf. Sci. 254 (2008) 4001– 4006. [14] Y.H. Ao, J.J. Xu, D.G. Fu, X.W. Shen, C.W. Yuan, Low temperature preparation of anatase TiO2-coated activated carbon, Colloid Surf. A 312 (2008) 125–130. [15] J. Matos, J. Laine, J.M. Herrmann, Synergy effect in the photocatalytic degradation of phenol on a suspended mixture of titania and activated carbon, Appl. Catal. B: Environ. 18 (1998) 281–291.