A New Application of Nanocrystal In2S3 in Efficient Degradation of

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A New Application of Nanocrystal In2S3 in Efficient Degradation of Organic Pollutants under Visible Light Irradiation Yunhui He, Danzhen Li,* Guangcan Xiao, Wei Chen, Yibin Chen, Meng Sun, Hanjie Huang, and Xianzhi Fu* Research Institute of Photocatalysis, State Key Laboratory Breeding Base of Photocatalysis, College of Chemistry and Chemical Engineering, Fuzhou UniVersity, Fuzhou 350002, P.R. China ReceiVed: October 12, 2008; ReVised Manuscript ReceiVed: February 4, 2009

The nanocrystal In2S3 (nc-In2S3) has been used as a visible light active photocatalyst. The optical absorption indicated a narrow band gap (Eg )1.9 eV) for nc-In2S3. Compared with TiO2-xNx, the decomposition of methyl orange using nc-In2S3 revealed enormously enhanced visible light activity. The · OH during the photocatalytic degradation process was detected by terephthalic acid photoluminescence probing technique (TA-PL). The organic intermediate products were successfully separated by liquid chromatogram and subsequently identified by an electrospray ionization (ESI) mass spectral technique. The possible photocatalytic mechanism is presented. 1. Introduction Methyl orange (MO), a well-known sulfonated azo dye indicator, is widely used in dyeing, foodstuff, paper and pulp, leather, and printing textiles. It is thus a common water pollutant in these industries.1-3 Intense research effort has been undertaken for the degradation of MO into harmless products. Since processes based on biodegradation were scarcely applied to textile wastewater due to the simultaneous presence of toxic residual dyestuffs, surfactants, and other harmful additives, the use of advanced photooxidation techniques would be imperative. The possible application of heterogeneous photocatalysis4-6 for the treatment has been investigated as an alternative to conventional methods. The treatment of persistent organic pollutants especially with solar energy has been a very active research topic in recent years.7 Especially, photocatalysis has many advantages over other treatment methods, for instance, the use of the environmentally friendly oxidant O2, the mild reaction conditions (e.g., room temperature, atmospheric pressure), and oxidation of the organic compounds even at low concentrations.8-10 TiO2 is one of the most widely used and highly efficient photocatalysts among semiconductors.11,12 However, it is only active under ultraviolet (UV) light irradiation, not responding to visible light (λ > 400 nm), which is the main component in solar light and indoor illuminations.13-15 For this reason, TiO2 is limited for indoor use. Therefore, much work has been done to develop visible-light-sensitive photocatalysts. One of the efforts in the development is modification of TiO2 by doping with metallic or nonmetallic elements such as V and Cr15-18 or N, S, and C.19-24 Generally speaking, these doped photocatalysts cannot show an ideal absorption in the visiblelight region or unstable during the photocatalysis process, leading to low activities.25 Another challenge is to develop new materials.26-31 The traditional visible-light photocatalysts were either unstable upon illumination with light (e.g., CdS, CdSe)32 or exhibited low activity (e.g., WO3, Fe2O3).33 Herein we report a novel non-TiO2, but more efficient than TiO2-based, visiblelight photocatalyst to utilize the solar spectrum and improve * Corresponding author. Tel./Fax: (+86)591-83779256. E-mail: dzli@ fzu.edu.cn (D.L.), [email protected] (X.F.).

the quantum efficiency. Most of the sulfides have been reported to be promising photocatalysts under visible light irradiation. However, most of the sulfides are not stable under irradiation and undergo anodic photocorrosion. To the best of our knowledge, the visible-light photooxidation activity of In2S3 has not been reported yet, except for the report about composite photocatalysts using In2S3.34,35 In this paper, we report a very simple method to prepare stable and recoverable nanocrystal In2S3 catalyst. The detailed investigation on In2S3 photodegradation of MO was systematically done to show the operating mechanisms. As a result, we first found that In2S3 showed high activity for organic dye bleaching under visible light irradiation. The current investigation provided a simple and easily scaled-up approach to produce photocatalysts for efficient removal of dye effluents in wastewater. 2. Experimental Section 2.1. Materials. Indium chloride (InCl3 · 4H2O), hydrochloric acid, and sodium sulfide (Na2S) were analytical grade, which were purchased from Shanghai Chemical Co. Titanium dioxide (P25, a mixture of 80% anatase and 20% rutile) was purchased from Degussa Co. Ultrapure water used for the preparation of all solutions was obtained by filtration and distillation of deionized water. All chemicals were used without further treatment. 2.2. Synthesis of Nanocrystal In2S3. In a typical procedure, an appropriate amount of analytical grade InCl3 · 4H2O was dissolved in distilled water to form a 0.3 M solution of InCl3. The pH value of the solution was adjusted to 1.0 by adding an appropriate amount of dilute hydrochloric acid to prevent the hydrolysis of InCl3. An appropriate amount of Na2S solution was gradually added to the solution, with continuous stirring, to give a homogeneous yellow sol (the mol ratio of In:S ) 1:2.5).Then the pH value of this sol was adjusted to 3.0 by adding a dilute hydrochloric acid. Afterward, a Teflon-lined autoclave of 100 mL capacity was filled with the sol up to 50% of the total volume. All of the process was performed in stink cupboard. The autoclave was sealed and maintained at 160 °C for 24 h and then cooled to room temperature naturally. The yellow precipitate was centrifuged and washed with distilled

10.1021/jp809028y CCC: $40.75  2009 American Chemical Society Published on Web 03/12/2009

Efficient Degradation of Organic Pollutants

Figure 1. Diffuse absorption coefficient F(R) and optical band gap energy Eg (inset) of nc-In2S3.

water and alcohol several times. The product was dried in vacuum at 100 °C for 4 h. 2.3. Analytical Procedures. Transmission electron microscopy (TEM) images were collected by using a JEOL JEM 2010F microscope working at 200 kV and equipped with an energydispersive X-ray analyzer (Phoenix). X-ray diffraction (XRD) patterns were recorded on a Bruker D8 Advance X-ray diffractometer with Cu KR radiation. The nitrogen adsorption and desorption isotherms were measured at 77 K using a Micrometrics ASAP 2020 system after the sample was degassed in vacuum at 80 °C for 12 h. A Varian Cary 500 UV-vis spectrophotometer was used to record the UV-vis spectra of the samples. X-ray photoelectron spectroscopy (XPS) was performed on the Physical Electronics instrument (PHI) Quantum 2000 using mono-Al KR (EKR ) 1486.6 eV) radiation. Photoluminescence (PL) was measured on an Edinburgh FL/ FS900 spectrophotometer with a Xe lamp at room temperature. The organic intermediate products were measured by liquid chromatogram/mass spectrometer (LC-MS) using trap XCT with

J. Phys. Chem. C, Vol. 113, No. 13, 2009 5255 ESI interface. Chromatographic separation was carried out at 30 °C with C18 (5 µm-250 mm-2.0 mm) column. The mobile phase consisted of methanol-water ) 70:30 (v/v) was set at a flow rate of 0.6 mL/min. The ESI source was set at the negative ionization mode. The MS operating conditions were optimized as follows: drying gas 8 L/min, curved desolvation line (CDL) temperature 350 °C, and capillary voltage +3.5 kV. 2.4. Photocatalytic Procedure. The photocatalytic activity of nc-In2S3 was evaluated from the bleaching of MO dye in water. In the test, the powder of 0.04 g of nc-In2S3 was suspended in 80 mL of MO solution with the initial concentration of 20 ppm in a cylindrical reaction vessel with a 44 cm2 plane side and 7 cm height. To obtain the adsorbed equilibrium states, the suspension was kept in the dark for 120 min with continuing agitation prior to visible light irradiation. The reactor was then irradiated with visible light emitted by a 500 W halogen lamp with a cutoff filter for UV light and a water cutoff filter for infrared light. The light intensity was measured with an optical-radiation power/energy meter (LPE-1B, Physcience Opto-Electonics Co., Ltd., Beijing). The light intensity permeating the filters is 113.4 mW/cm2. The system was cooled by a fan and water, which were used to maintain the system at room temperature. The transmission spectrum of the filter is shown in Figure S1 of Supporting Information. At given time intervals, 4 mL aliquots were extracted and centrifuged to remove the In2S3 particles. The filtrates were analyzed by recording variations of the maximum absorption band (λ ) 464 nm) in the UV-vis spectra of MO using UV-vis spectrophotometer. For comparison, N-doped TiO2 was utilized as a reference of visiblelight-driven photocatalyst. N-doped TiO2 was prepared by heating commercial available TiO2 under NH3 gas flow at 873 K for 3 h.36,37 The chemical stability of nc-In2S3 during photocatalytic process was also evaluated using repeated experiments of MO decomposition. 3. Results and Discussion 3.1. UV-Vis Analysis of nc-In2S3. The diffuse absorption spectrum of the In2S3 is revealed in Figure 1. For an indirectgap semiconductor, it is well-known that the relation between

Figure 2. Nitrogen adsorption/desorption isotherm and Barrett-Joyner-Halenda (BJH) pore size distribution plot (inset) of In2S3.

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Figure 3. (a) Photograph of the photodegradation of MO over nc-In2S3 against irradiation time. (b) UV-visible spectral changes of MO in aqueous In2S3 dispersions as a function of irradiation time. Photocatalytic properties of nc-In2S3 samples compared with N-doped TiO2 sample and dark reaction (inset).

absorption coefficient and band gap energy can be described by the formula38 (F(R)E)1/2 ) A(E - Eg), where E and Eg are photon energy and optical band gap energy, respectively, and A is the characteristic constant of semiconductors. From the equation, (F(R)E)1/2 has a linear relation with E. Extrapolating the linear relation to (F(R)E)1/2 ) 0 gave the band gap Eg of approximate 1.9 eV (inset of Figure 1) at room temperature, which agreed with the experimental reports.39 As In2S3 can absorb a large amount of visible light, it is considered to be a suitable visible-irradiation photocatalyst. On the other hand, we also have performed the density functional theory (DFT) calculations with generalized-gradient approximations (GGA) exchange-correlation functional by Perdew-Burke-Ernzerhof (PBE) method40 to study the band structure and the density of state (DOS) (see Supporting Information, Figure S2). The band gap of In2S3 is estimated to be 1.95 eV, which is in good agreement with our experimental data. The band structure indicates that charge transfer upon photoexcitation occurs from the S 3p orbital to the In 5p empty orbital. 3.2. N2 Adsorption-Desorption. The N2 adsorption/desorption isotherm and the pore-size distribution (inset) of In2S3 is plotted in Figure 2. It is obvious that the isotherm is type VI, indicating the presence of mesoporous materials according to the IUPAC classification. The pore-size distribution obtained from the isotherm indicated that the diameters of pores was about 3.5 nm for In2S3. The BET specific surface area of the sample calculated from N2 isotherms at -195.6 °C was found to be as much as 130.7 m2 g-1. The large surface area of the sample indicated the possibility of highly efficient photocatalyst. The single-point total volume of pores at P/P0 ) 0.9746 was 0.087 cm-3 g-1.

3.3. Photooxidation Activity. Figure 3 shows the decrease in MO concentration in the nc-In2S3 suspended solution as a function of reaction time: In2S3 loading was 0.4 g · L-1 and the initial concentration of MO was 20 ppm. The y-axis of degradation was reported as C/C0. C is the absorption of MO at each irradiated time interval of main peak of absorption spectrum at wavelength 464 nm. C0 is the absorption of starting concentration when adsorption-desorption equilibrium was achieved. For comparison, the degradation of MO by N-doped TiO2 was also given (Figure 3b, inset). Prior to light irradiation, the solution was kept in the dark for 120 min to obtain adsorption equilibrium states. After 4 h of visible light irradiation, the photocatalytic conversion of degradation MO over In2S3 was up to 95%; however, MO was only a little decomposed by N-doped TiO2 under the same condition. This result suggests the higher photoooxidative activity for nc-In2S3 than N-doped TiO2. To clarify the effect of catalysis and photolysis, we also carried out the decomposition experiments in the dark with ncIn2S3 (catalysis) and light irradiation without nc-In2S3 (photolysis). Decomposition by photolysis was hardly observed, suggesting that the decomposition of MO was largely caused by nc-In2S3 photocatalytic oxidation. Furthermore, we used a Ba(OH)2 solution to detect CO2 during the photocatalytic degradation of MO over In2S3. The reaction gases were swept out of the reaction vessel with a stream of O2 and were bubbled though a saturated solution of Ba(OH)2 in 0.2 M sodium hydroxide. Under visible light, BaCO3 was observed which was produced by reaction of Ba(OH)2 solution and the resultant CO2. It demonstrated that there were some CO2 produced in the photocatalytic reactions. No BaCO3 precipitation was observed in the dark with the same experiment conditions. However, it


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Figure 4. Cycling runs in the photocatalytic degradation of MO in the presence of nc-In2S3 under visible-light irradiation.

Figure 5. TEM image of nc-In2S3: (a) fresh, (b) typical HRTEM image of fresh nc-In2S3, (c) used, and (d) typical HRTEM image of used nc-In2S3. The insets in (a) and (c) show the corresponding electron diffraction pattern (SAED).


He et al.

Figure 6. X-ray diffraction patterns of fresh and used nc-In2S3.

is difficult to do quantitative analysis of BaCO3 (CO2), because the amount of precipitation was so little. The conclusion is that at least a part of MO was completely mineralized by using ncIn2S3 photocatalyst. 3.4. Stability of nc-In2S3 Photocatalyst. The stability of a photocatalyst is very important for industrial application; however, traditional visible light active photocatalysts are either unstable or have low efficiency.32,33,41 In this experiment, In2S3 was recycled after bleaching the MO under visible light irradiation and was reused five times in the decomposition of MO to test the chemical stability. After four recycles for the photodegradation of MO, the catalyst did not exhibit loss of activity (shown in Figure 4). In the fifth run, a slight decrease in activity occurred; however, our catalysts display more stability as compared to other sulfides such as CdS. On the other hand, the surface of the catalyst must be contaminated by the reactant and other substances (CO2, O2 absorbed on the surface) more or less, which may make some of the active places disappear, followed by activity decrease. In the fifth run, the photocatalytic conversion is also up to 90%. That may be an effective proof that In2S3 is a useful and stable visible-light-induced photocatalyst. Moreover, TEM, XRD, and XPS were also performed to confirm the chemical stability of nc-In2S3 after the fifth run. Figure 5 showed TEM images of the surface of nc-In2S3 before and after photocatalytic decomposition of MO, which indicated that the samples were composed of a large quantity of nanoparticles possessing nanopores. The selected-area electron diffraction (SAED) patterns (inset of Figure 5, a and c) showed a set of concentric rings instead of sharp spots as a result the In2S3 nanoparticles were small crystallites. Both of the diffraction rings of the fresh and the used samples could be readily indexed to (2212), (1015), (0012), (109), and (103) planes of the tetragonal β-In2S3 (JCPDS card No. 25-0390), very well consistent with the XRD analysis. The SAED patterns took little change before and after the photocatalytic reaction. The representative high-resolution TEM images of the fresh and used In2S3 samples both showed the lattice fringes of nanocrystals with d ) 0.32 nm corresponding to an interplanar distance of the (109) plane of tetragonal β-In2S3 (Figure 5, b and d). Figure 6 indicates the XRD patterns of the fresh and used In2S3 photocatalyst. The XRD pattern of the sample after the fifth run was almost similar to that of the as-prepared sample, and both of them were in good agreement with tetragonal β-In2S3 (JCPDS card No. 25-0390). Both TEM and XRD experiments support the conclusion that nc-In2S3 is very stable during photocatalytic process. The photocatalyst before and after

Figure 7. X-ray photoelectron spectra of fresh and used nc-In2S3: (a) S 2p, (b) In 3d.

reaction was also analyzed by XPS (Figure 7). Only C, S, and In peaks can be observed in the survey of the spectrum (see Supporting Information, Figure S3). The binding energies for S 2p (Figure 7a) and In 3d (Figure 7b) were in accordance with the data reported for In2S3.42,43 No peak shift was found for the peaks of In 3d and S 2p in the surface of the fresh and used photocatalyst, which indicated the valence of In and S were not changed. It could also suggest that nc-In2S3 was not photocorroded during the photocatalytic reaction. Judging from these results, In2S3 is considered to be relatively stable during photocatalytic reaction under visible light irradiation. 3.5. Exclusion of Dye Sensibilization for nc-In2S3. In order to confirm the photocatalytic property of In2S3 was not photosensitized reaction as TiO2-MO, we used a combined filter (see Supporting Information, Scheme S1) to exclude the light absorption of MO. The transmissivity of the combine filter and the absorptance of MO were plotted in Figure 8a. It was obvious that the light absorbed by MO was almost excluded. There was almost no light that could induce MO to photosensitize In2S3 photocatalyst. Figure 8b indicated the concentration changes of MO by the photodegradation of In2S3 using the combine filter. After 4.5 h of visible light irradiation, the photocatalytic conversion of degradation MO over In2S3 was up to 90%. Comparing with not using combine filter, the photocatalytic activity of In2S3 was also very high. MO was also degraded only with longer irradiation time because the weaker irradiation



Figure 8. (a) Transmission spectra of the combined filter and the absorption spectra of MO. (b) Photocatalytic degradation of MO in the presence of nc-In2S3 under visible light λ > 500 nm irradiation.

light. So all the above results can prove the reaction of MO decomposition was photocatalysis rather than photosensitized or photochemical reaction. In additional, experiment decomposition of Rhodamine B (RhB) was also carried out, and the photocatalytic conversion was up to 90% after 3 h irradiation (see Supporting Information, Figure S4). 3.6. Detection of Hydroxyl Radicals. In general, hydroxyl radicals are known as a key active species in the photocatalytic process.44,45 The oxidative ability of hydroxyl radicals is high enough to attack many organic molecules. At present, the main detection techniques for hydroxyl radicals include spin-trapping electron paramagnetic resonance (EPR), high performance liquid chromatography (HPLC), and chemical fluorometric assay.46 Terephthalic acid photoluminescence probing technique (TAPL), a highly sensitive and simple method, has been widely used in detection of hydroxyl radicals.47 The TA probed hydroxyl radicals to form 2-hydroxylterephthalic acid (HTA) during the photocatalytic process. The mechanism is shown in Scheme 1. The HTA exhibited a strong fluorescence peak (λex ) 315 nm, λem ) 426 nm). Thus, we measured the fluorescence of HTA to detect hydroxyl radicals indirectly. The photoluminescence spectra of In2S3/TA solution under visible light

SCHEME 1: Reaction between · OH and Terephthalic Acid (TA)

irradiation is shown in Figure 9a. The photoluminescence emission peak of HTA (λem ) 426 nm) increased steadily with the irradiation time, suggesting that the hydroxyl radicals were increased steadily. Figure 9b indicates that the photoluminescence intensity of the In2S3/TA solution linearly increased by the irradiation time and the ratio of hydroxyl radical generation rate (V) to time (t) followed the linear characteristic. In addition, Figure 9c shows the irradiation time (t) versus ln C0/C of the photodegradation MO by In2S3. The plots also exhibited a linear characteristic which was in accordance with the hydroxyl radical generation rate, suggesting that the main reactive species may be the · OH in In2S3 photocatalytic process.


He et al.

Figure 9. (a) · OH-trapping PL spectra of nc-In2S3 /TA solution. (b) Plots of the induced PL intensity (at λ ) 426 nm) against irradiation time. (c) Plots of the photocatalytic degradation of MO by nc-In2S3 against irradiation time.

Figure 10. Chromatograms monitored in full scan MS corresponding to the solution of MO degraded at 0, 1, and 2 h; each peak is characterized by its m/z value.

3.7. Identification of the Intermediate Products by LCMS. Sulfonated azo dyes have poor thermal stability and low volatility. Thus, we considered the application of LC-MS as a suitable analytical approach for the determination of MO. The sulfonated products after degradation were used to study the

possible photocatalytic pathway. The LC-MS technique has been already proposed48,49 for the analysis of mixtures of sulfonated azo dyes in water and wastewater, but hardly applied to the separation and identification of their degradation products to study the photocatalytic process. Typical intermediates generated



SCHEME 2: Fragmentation Scheme of MO Degradation Products

in the degradation of MO were identified from negative ionization mode mass spectra. Figure 10 reports the chromatograms monitored in full scan MS. The significant peaks presented at the various degradation times were labeled with the corresponding m/z values. The mass peak at m/z ) 304.0 of the initial solution was that of the MO dye. The MO (m/z ) 304.0) completely disappeared after 2 h irradiation. The new signals at m/z ) 289.9 and 260.0 were observed after irradiation for 1 h, which were attributed to [C13H12N3SO3]- and [C12H9N2SO3]-, respectively. The mass peaks at m/z ) 195.4 (attributed to [C6H12NSO4]-) observed on 2 h irradiation generated through cleavage of the N ) N bond. After irradiation for 2 h, there were only very low chromatogram peaks at m/z ) 195.4. It indicated that the MO was decomposed. Some of MO may be oxidized by · OH radical and mineralized to produce inorganic compounds, such as CO2, NH4+, SO32-, and SO42-. The main pathways in the photodegradation of MO by In2S3 were visualized in Scheme 2. 4. Conclusion We have developed a simple and facile method to prepare nc-In2S3. The optical band gap was estimated to be about 1.9 eV. We examined the photooxidation activity, employing an example of the decomposition of MO in the liquid phase under visible light irradiation. MO was easily decomposed under the visible light (λ > 400 nm) irradiation, and the reaction rate was faster than that of N-doped TiO2. The photophysical properties, photooxidation activity, and reaction mechanism of nc-In2S3 have been investigated. These results suggested that nc-In2S3 is a prominent material for photooxidation of organics in the range of visible light. From detection of hydroxyl radicals and identification of the intermediate products, we concluded the mechanism of nc-In2S3. The main reactive species may be the · OH in In2S3 photocatalytic process, and the main pathways were proposed. Since the nc-In2S3 could be applied for the degradation of organic pollutants, it may also provide useful insight for the development of other visible-light-active semiconductors. Acknowledgment. This work was financially supported by the National Natural Science Foundation of China (20537010,

20677010, and 20873023), An “863” Project from the MOST of China (2006AA03Z340), National Basic Research Program of China (973 Program: 2007CB613306), and the Natural Science Foundation of Fujian, China (2003F004, JA07001 and 2007F5066). The authors are indebted to Prof. Yongfan Zhang for the discussions of band structure. Supporting Information Available: UV-vis transmittance of the two light filters, X-ray photoelectron survey spectra of In2S3, DFT calculations for In2S3, and the sketch map of combined filter and the UV-visible spectral change of Rhodamine B (10-5 mol/L) in aqueous In2S3. This material is available free of charge via the Internet at http://pubs.acs.org. References and Notes (1) Muruganandham, M.; Swaminatham, M. Dyes Pigm. 2004, 62, 269. (2) Baiocchi, C.; Brussimo, C. M.; Praumauro, E.; Prevot, A. B.; Palmisano, L.; Marci, G. Int. J. Mass Spectrom. 2002, 214, 247. (3) Zollinger, H. Color Chemistry: Synthesis, Properties and Applications of Organic Dyes and Pigments; VCH Publishers: New York, 1987. (4) Ollis, D. F.; Pelizzetti, E.; Serpone, N. In Photocatalysis: Fundamentals and Applications; Serpone, N., Pelizzetti, E., Eds.; John Wiley & Sons: New York, 1989; Chapter 18, pp 603. (5) Ollis, D. F.; Al-Ekabi, H. Photocatalytic Purification and Treatment of Water and Air; Elsevier: Amsterdam, 1993. (6) Hoffmann, M. R.; Martin, S. T.; Choi, W.; Bahnemann, D. W. Chem. ReV. 1995, 95, 69. (7) Meunier, B. Science 2002, 296, 270. (8) Tao, X.; Ma, W.; Zhang, T.; Zhao, J. C. Angew. Chem. 2001, 113, 3103–13; Angew. Chem. Int. Ed. 2001, 40, 3014. (9) Ma, W.; Li, J.; Tao, X.; He, J.; Xu, Y.; Yu, Zhao, J. C. Angew. Chem. 2003, 115, 1059–61; Angew. Chem. Int. Ed. 2003, 42, 1029. (10) Falconer, J. L.; Magrini-Bair, K. A. J. Catal. 1998, 179, 171. (11) Salem, I. Catal. ReV. Sci. Eng. 2003, 45, 205. (12) Linsebigler, A. L.; Lu, G.; Yates, J. T. Chem. ReV. 1995, 95, 735. (13) Wu, T.; Liu, G.; Zhao, J.; Hidaka, H.; Serpone, N. J. Phys. Chem. B 1998, 102, 5845. (14) Wu, T.; Liu, G.; Zhao, J.; Hidaka, H.; Serpone, N. J. Phys. Chem. B 1999, 103, 4862. (15) Zhao, W.; Chen, C.; Li, X.; Zhao, J.; Hidaka, H.; Serpone, N. J. Phys. Chem. B 2002, 106, 5022. (16) Borgarello, E.; Kiwi, J.; Gratzel, M.; Pelizzetti, E.; Visca, M. J. Am. Chem. Soc. 1982, 104, 2996. (17) Serpone, N.; Lawless, D.; Disdier, J.; Herrmann, J. M. Langmuir 1994, 10, 643. (18) Yamashita, H.; Harada, M. J. Photochem. Photobiol A. 2002, 148, 257.

5262 J. Phys. Chem. C, Vol. 113, No. 13, 2009 (19) Asahi, R.; Morikawa, T.; Ohwaki, T.; Aoki, K.; Taga, Y. Science 2001, 293, 269. (20) Irie, H.; Watanabe, Y.; Hashimoto, K. J. Phys. Chem. B 2003, 107, 5483. (21) Ohno, T.; Mitsui, T.; Matsumura, M. Chem. Lett. 2003, 32, 364. (22) Irie, H.; Watanabe, Y.; Hashimoto, K. Chem. Lett. 2003, 32, 772. (23) Liu, H. Y.; Gao, L. Chem. Lett. 2004, 33, 730. (24) Ishikawa, A.; Takata, T.; Kondo, J. N.; Hara, M.; Kobayashi, H.; Domen, K. J. Am. Chem. Soc. 2002, 124, 13547. (25) Hwang, D. W.; Kim, H. G.; Lee, J. S.; Kim, J.; Li, W.; Oh, S. H. J. Phys. Chem. B 2005, 109, 2093. (26) Kudo, A.; Omori, K.; Kato, H. J. Am. Chem. Soc. 1999, 121, 11459. (27) Kudo, A. J. Ceram. Soc. Jpn. 2001, 109, S81. (28) Tang, J. W.; Zou, Z. G.; Ye, J. H. Catal. Lett. 2004, 92, 53. (29) Kako, T.; Ye, J. H. Mater. Trans. 2005, 46, 2694. (30) Kato, H.; Kobayashi, H.; Kudo, A. J. Phys. Chem. B 2002, 106, 12441. (31) Kim, H. G.; Hwang, D. W.; Lee, J. S. J. Am. Chem. Soc. 2004, 126, 8912. (32) De, G. C.; Roy, A. M.; Bhattacharya, S. S. Int. J. Hydrogen Energy 1995, 20, 127. (33) Hwang, D. W.; Kim, J.; Park, T. J.; Lee, J. S. Catal. Lett. 2002, 80, 53. (34) Kapinus, E. I.; Viktorova, T. I.; Khalyavka, T. A. Theor. Exp. Chem. 2006, 42, 282. (35) Shen, S. H.; Guo, L. J. J. Solid State Chem. 2006, 179, 2629.

He et al. (36) Asahi, R.; Morikawa, T.; Ohwaki, T.; Aoki, K.; Taga, Y. Science 2001, 293, 269. (37) Irie, H.; Watanabe, Y.; Hashimoto, K. J. Phys. Chem. B 2003, 107, 5483. (38) Pankove, J. I. Optical Processes in Semiconductors; Dover: New York, 1971; p 412. (39) Kim, W. T.; Kim, C. D. J. Appl. Phys. 1986, 60, 2631. (40) Perdew, P.; Burke, S.; Ernzerhof, M. Phys. ReV. Lett. 1996, 77, 3865–8. (41) Zollweg, R. J. Phys. ReV. 1958, 111, 113. (42) Bae, E.; Choi, W. EnViron. Sci. Technol. 2003, 37, 147. (43) He, J. J.; Hagfeldt, A.; Lindquist, S. E. Langmuir 2001, 17, 2743. (44) Ollis, D. F.; Hsiao, C. Y.; Budiman, L.; Lee, C. L. J. Catal. 1984, 88, 89. (45) Al-Ekabi, H.; Serpone, N.; Pelizzetti, E.; Minero, C.; Fox, M. A.; Draper, R. B. Langmuir 1989, 5, 250. (46) Shibashi, K. A.; Fujishima, T.; Watanabe, K. Electrochem. Commun. 2000, 2, 207. (47) Barreto, J. C.; Smith, G. S.; Strobel, N. H. P.; McQuillin, P. A.; Miller, T. A. Life Sci. 1995, 56, 89. (48) Riu, J.; Scho¨nsee, I.; Barcelo´, D.; Ra`fols, C. Trends Anal. Chem. 1997, 16, 405. (49) Ra`fols, C.; Barcelo´, D. J. Chromatogr. A 1997, 777, 177.

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