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Low-dimensional nanostructures are a promising class of ideal high-performance candidates for energy storage and conversion owing to their unique structural, optical, and chemical properties. Low-dimensional nanostructured photocatalysts have attracted ever-growing research attention. In this review, we mainly emphasize on summarizing the 0-, 1-, and 2-dimensional nanostructured photocatalysts systematically, including their photocatalytic performance, synthesis methods, and theoretical analysis. From the viewpoint of dimension, we try to figure out the way to design more high-efficiency photocatalysts towards numerous applications in the field of solar energy conversion, hoping to promote efficient control and rational development of photocatalysts.

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Low-dimensional nanostructured photocatalysts

Show Author's information Hao-Min XUHuan-Chun WANGYang SHENYuan-Hua LIN( )Ce-Wen NAN
State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China


Low-dimensional nanostructures are a promising class of ideal high-performance candidates for energy storage and conversion owing to their unique structural, optical, and chemical properties. Low-dimensional nanostructured photocatalysts have attracted ever-growing research attention. In this review, we mainly emphasize on summarizing the 0-, 1-, and 2-dimensional nanostructured photocatalysts systematically, including their photocatalytic performance, synthesis methods, and theoretical analysis. From the viewpoint of dimension, we try to figure out the way to design more high-efficiency photocatalysts towards numerous applications in the field of solar energy conversion, hoping to promote efficient control and rational development of photocatalysts.

Keywords: nanostructure, photocatalysis, low-dimension


Tong H, Ouyang S, Bi Y, et al. Nano-photocatalytic materials: Possibilities and challenges. Adv Mater 2012, 24: 229–251.
Hisatomi T, Kubota J, Domen K. Recent advances in semiconductors for photocatalytic and photoelectrochemical water splitting. Chem Soc Rev 2014, 43: 7520–7535.
Asahi R, Morikawa T, Ohwaki T, et al. Visible-light photocatalysis in nitrogen-doped titanium oxides. Science 2001, 293: 269–271.
Gao F, Chen XY, Yin KB, et al. Visible-light photocatalytic properties of weak magnetic BiFeO3 nanoparticles. Adv Mater 2007, 19: 2889–2892.
Li S, Lin Y-H, Zhang B-P, et al. Photocatalytic and magnetic behaviors observed in nanostructured BiFeO3 particles. J Appl Phys 2009, 105: 056105.
Xu H-M, Wang H-C, Shen Y, et al. Photocatalytic and magnetic behaviors of BiFeO3 thin films deposited on different substrates. J Appl Phys 2014, 116: 174307.
Cui Z, Zeng D, Tang T, et al. Enhanced visible light photocatalytic activity of QDS modified Bi2WO6 nanostructures. Catal Commun 2010, 11: 1054–1057.
Lin H, Huang CP, Li W, et al. Size dependency of nanocrystalline TiO2 on its optical property and photocatalytic reactivity exemplified by 2-chlorophenol. Appl Catal B: Environ 2006, 68: 1–11.
Brus LE. Electron–electron and electron–hole interactions in small semiconductor crystallites: The size dependence of the lowest excited electronic state. J Chem Phys 1984, 80: 4403.
Li L, Salvador PA, Rohrer GS. Photocatalysts with internal electric fields. Nanoscale 2014, 6: 24–42.
Li S, Lin Y-H, Zhang B-P, et al. Controlled fabrication of BiFeO3 uniform microcrystals and their magnetic and photocatalytic behaviors. J Phys Chem C 2010, 114: 2903–2908.
Bi Y, Ouyang S, Umezawa N, et al. Facet effect of single-crystalline Ag3PO4 sub-microcrystals on photocatalytic properties. J Am Chem Soc 2011, 133: 6490–6492.
Xi G, Ye J. Synthesis of bismuth vanadate nanoplates with exposed {001} facets and enhanced visible-light photocatalytic properties. Chem Commun 2010, 46: 1893–1895.
Xie YP, Liu G, Yin L, et al. Crystal facet-dependent photocatalytic oxidation and reduction reactivity of monoclinic WO3 for solar energy conversion. J Mater Chem 2012, 22: 6746–6751.
Harn Y-W, Yang T-H, Tang T-Y, et al. Facet-dependent photocatalytic activity and facet-selective etching of silver(I) oxide crystals with controlled morphology. ChemCatChem 2015, 7: 80–86.
Giocondi JL, Rohrer GS. The influence of the dipolar field effect on the photochemical reactivity of Sr2Nb2O7 and BaTiO3 microcrystals. Top Catal 2008, 49: 18–23.
Han J-T, Huang Y-H, Wu X-J, et al. Tunable synthesis of bismuth ferrites with various morphologies. Adv Mater 2006, 18: 2145–2148.
Huo Y, Miao M, Zhang Y, et al. Aerosol-spraying preparation of a mesoporous hollow spherical BiFeO3 visible photocatalyst with enhanced activity and durability. Chem Commun 2011, 47: 2089–2091.
Yu J, Zhang Y, Kudo A. Synthesis and photocatalytic performances of BiVO4 by ammonia co-precipitation process. J Solid State Chem 2009, 182: 223–228.
Wang Z, Luo W, Yan S, et al. BiVO4 nano-leaves: Mild synthesis and improved photocatalytic activity for O2 production under visible light irradiation. CrystEngComm 2011, 13: 2500–2504.
Dunkle SS, Helmich RJ, Suslick KS. BiVO4 as a visible-light photocatalyst prepared by ultrasonic spray pyrolysis. J Phys Chem C 2009, 113: 11980–11983.
Huang Y, Ai Z, Ho W, et al. Ultrasonic spray pyrolysis synthesis of porous Bi2WO6 microspheres and their visible-light-induced photocatalytic removal of NO. J Phys Chem C 2010, 114: 6342–6349.
Castillo NC, Heel A, Graule T, et al. Flame-assisted synthesis of nanoscale, amorphous and crystalline, spherical BiVO4 with visible-light photocatalytic activity. Appl Catal B: Environ 2010, 95: 335–347.
Jiang H-q, Endo H, Natori H, et al. Fabrication and photoactivities of spherical-shaped BiVO4 photocatalysts through solution combustion synthesis method. J Eur Ceram Soc 2008, 28: 2955–2962.
Zhang Z, Wang W, Shang M, et al. Low-temperature combustion synthesis of Bi2WO6 nanoparticles as a visible-light-driven photocatalyst. J Hazard Mater 2010, 177: 1013–1018.
Chung C-Y, Lu C-H. Reverse-microemulsion preparation of visible-light-driven nano-sized BiVO4. J Alloys Compd 2010, 502: L1–L5.
Yin W, Wang W, Sun S. Photocatalytic degradation of phenol over cage-like Bi2MoO6 hollow spheres under visible-light irradiation. Catal Commun 2010, 11: 647–650.
Zhang G, Lü F, Li M, et al. Synthesis of nanometer Bi2WO6 synthesized by sol–gel method and its visible-light photocatalytic activity for degradation of 4BS. J Phys Chem Solids 2010, 71: 579–582.
Tian Y, Hua G, Xu W, et al. Bismuth tungstate nano/microstructures: Controllable morphologies, growth mechanism and photocatalytic properties. J Alloys Compd 2011, 509: 724–730.
Zhang Y, Li G, Yang X, et al. Monoclinic BiVO4 micro-/nanostructures: Microwave and ultrasonic wave combined synthesis and their visible-light photocatalytic activities. J Alloys Compd 2013, 551: 544–550.
Wu Y, Xing M, Tian B, et al. Preparation of nitrogen and fluorine co-doped mesoporous TiO2 microsphere and photodegradation of acid orange 7 under visible light. Chem Eng J 2010, 162: 710–717.
Zalas M. Synthesis of N-doped template-free mesoporous titania for visible light photocatalytic applications. Catal Today 2014, 230: 91–96.
Dong F, Wang H, Wu Z. One-step “green” synthetic approach for mesoporous C-doped titanium dioxide with efficient visible light photocatalytic activity. J Phys Chem C 2009, 113: 16717–16723.
Paramasivam I, Jha H, Liu N, et al. A review of photocatalysis using self-organized TiO2 nanotubes and other ordered oxide nanostructures. Small 2012, 8: 3073–3103.
Zhang X, Liu H, Zheng B, et al. Photocatalytic and magnetic behaviors observed in BiFeO3 nanofibers by electrospinning. J Nanomater 2013, 2013: 1–7.
Wu N, Wang J, Tafen DN, et al. Shape-enhanced photocatalytic activity of single-crystalline anatase TiO2 (101) nanobelts. J Am Chem Soc 2010, 132: 6679–6685.
Jiang T, Xie T, Chen L, et al. Carrier concentration-dependent electron transfer in Cu2O/ZnO nanorod arrays and their photocatalytic performance. Nanoscale 2013, 5: 2938–2944.
Kudo A, Omori K, Kato H. A novel aqueous process for preparation of crystal form-controlled and highly crystalline BiVO4 powder from layered vanadates at room temperature and its photocatalytic and photophysical properties. J Am Chem Soc 1999, 121: 11459–11467.
Bai X, Wang L, Zong R, et al. Photocatalytic activity enhanced via g-C3N4 nanoplates to nanorods. J Phys Chem C 2013, 117: 9952–9961.
Soundarrajan P, Sankarasubramanian K, Sethuraman K, et al. Controlled (110) and (101) crystallographic plane growth of single crystalline rutile TiO2 nanorods by facile low cost chemical methods. CrystEngComm 2014, 16: 8756–8768.
Cha SI, Hwang KH, Kim YH, et al. Crystal splitting and enhanced photocatalytic behavior of TiO2 rutile nano-belts induced by dislocations. Nanoscale 2013, 5: 753–758.
Jang JS, Joshi UA, Lee JS. Solvothermal synthesis of CdS nanowires for photocatalytic hydrogen and electricity production. J Phys Chem C 2007, 111: 13280–13287.
Hsu Y-J, Lu S-Y. Photoluminescence resulting from semiconductor−metal solid solution observed in one-dimensional semiconductor nanostructures. Langmuir 2004, 20: 23–26.
Lin Y-F, Hsu Y-J, Lu S-Y, et al. Non-catalytic and template-free growth of aligned CdS nanowires exhibiting high field emission current densities. Chem Commun 2006: 2391–2393.
Zhang J, Jiang F, Zhang L. Fabrication of single-crystalline semiconductor CdS nanobelts by vapor transport. J Phys Chem B 2004, 108: 7002–7005.
Gao T, Li QH, Wang TH. CdS nanobelts as photoconductors. Appl Phys Lett 2005, 86: 173105.
Ge JP, Li YD. Selective atmospheric pressure chemical vapor deposition route to CdS arrays, nanowires, and nanocombs. Adv Funct Mater 2004, 14: 157–162.
Chen M, Xie Y, Lu J, et al. Synthesis of rod-, twinrod-, and tetrapod-shaped CdS nanocrystals using a highly oriented solvothermal recrystallization technique. J Mater Chem 2002, 12: 748–753.
Gao F, Yuan Y, Wang KF, et al. Preparation and photoabsorption characterization of BiFeO3 nanowires. Appl Phys Lett 2006, 89: 102506.
Shang M, Wang W, Ren J, et al. A practical visible-light-driven Bi2WO6 nanofibrous mat prepared by electrospinning. J Mater Chem 2009, 19: 6213–6218.
Prashanthi K, Gaikwad R, Thundat T. Surface dominant photoresponse of multiferroic BiFeO3 nanowires under sub-bandgap illumination. Nanotechnology 2013, 24: 505710.
Li D, Xia Y. Fabrication of titania nanofibers by electrospinning. Nano Lett 2003, 3: 555–560.
Hou D, Luo W, Huang Y, et al. Synthesis of porous Bi4Ti3O12 nanofibers by electrospinning and their enhanced visible-light-driven photocatalytic properties. Nanoscale 2013, 5: 2028–2035.
Wang S, Li C, Wang T, et al. Controllable synthesis of nanotube-type graphitic C3N4 and their visible-light photocatalytic and fluorescent properties. J Mater Chem A 2014, 2: 2885–2890.
Zhao Z-G, Miyauchi M. Nanoporous-walled tungsten oxide nanotubes as highly active visible-light-driven photocatalysts. Angew Chem Int Edit 2008, 47: 7051–7055.
Roy P, Berger S, Schmuki P. TiO2 nanotubes: Synthesis and applications. Angew Chem Int Edit 2011, 50: 2904–2939.
Ren L, Jin L, Wang J-B, et al. Template-free synthesis of BiVO4 nanostructures: I. Nanotubes with hexagonal cross sections by oriented attachment and their photocatalytic property for water splitting under visible light. Nanotechnology 2009, 20: 115603.
Zhang M, Shao C, Zhang P, et al. Bi2MoO6 microtubes: Controlled fabrication by using electrospun polyacrylonitrile microfibers as template and their enhanced visible light photocatalytic activity. J Hazard Mater 2012, 225–226: 155–163.
Liu S-J, Hou Y-F, Zheng S-L, et al. One-dimensional hierarchical Bi2WO6 hollow tubes with porous walls: Synthesis and photocatalytic property. CrystEngComm 2013, 15: 4124–4130.
Zhou M, Lou XW, Xie Y. Two-dimensional nanosheets for photoelectrochemical water splitting: Possibilities and opportunities. Nano Today 2013, 8: 598–618.
Sasaki T, Watanabe M, Hashizume H, et al. Macromolecule-like aspects for a colloidal suspension of an exfoliated titanate. Pairwise association of nanosheets and dynamic reassembling process initiated from it. J Am Chem Soc 1996, 118: 8329–8335.
Coleman JN, Lotya M, O'Neill A, et al. Two-dimensional nanosheets produced by liquid exfoliation of layered materials. Science 2011, 331: 568–571.
Liang S, Liang R, Wen L, et al. Molecular recognitive photocatalytic degradation of various cationic pollutants by the selective adsorption on visible light-driven SnNb2O6 nanosheet photocatalyst. Appl Catal B: Environ 2012, 125: 103–110.
Liu Q, Wu D, Zhou Y, et al. Single-crystalline, ultrathin ZnGa2O4 nanosheet scaffolds to promote photocatalytic activity in CO2 reduction into methane. ACS Appl Mater Interfaces 2014, 6: 2356–2361.
Chen S, Li Y, Lu R, et al. Preparation, characterization of C/Fe–Bi2WO6 nanosheet composite and degradation application of norfloxacin in water. J Nanosci Nanotechno 2013, 13: 5624–5630.
Li KW, Wang Y, Wang H, et al. Hydrothermal synthesis and photocatalytic properties of layered La2Ti2O7 nanosheets. Nanotechnology 2006, 17: 4863–4867.
Liu G, Yang HG, Wang X, et al. Visible light responsive nitrogen doped anatase TiO2 sheets with dominant {001} facets derived from TiN. J Am Chem Soc 2009, 131: 12868–12869.
Zhang J, Vukmirovic MB, Xu Y, et al. Controlling the catalytic activity of platinum-monolayer electrocatalysts for oxygen reduction with different substrates. Angew Chem Int Edit 2005, 44: 2132–2135.
Leprince-Wang Y, Yu-Zhang K, Nguyen Van V, et al. Correlation between microstructure and the optical properties of TiO2 thin films prepared on different substrates. Thin Solid Films 1997, 307: 38–42.
Liu HL, Lin MK, Cai YR, et al. Strain modulated optical properties in BiFeO3 thin films. Appl Phys Lett 2013, 103: 181907.
Chen P, Podraza NJ, Xu XS, et al. Optical properties of quasi-tetragonal BiFeO3 thin films. Appl Phys Lett 2010, 96: 131907.
Tae Kwon Y. Photocatalytic behavior of WO3-loaded TiO2 in an oxidation reaction. J Catal 2000, 191: 192–199.
Pan JH, Lee WI. Preparation of highly ordered cubic mesoporous WO3/TiO2 films and their photocatalytic properties. Chem Mater 2006, 18: 847–853.
Soni SS, Henderson MJ, Bardeau J-F, et al. Visible-light photocatalysis in titania-based mesoporous thin films. Adv Mater 2008, 20: 1493–1498.
Xu X, Lin Y-H, Li P, et al. Synthesis and photocatalytic behaviors of high surface area BiFeO3 thin films. J Am Ceram Soc 2011, 94: 2296–2299.
Zhang L-W, Wang Y-J, Cheng H-Y, et al. Synthesis of porous Bi2WO6 thin films as efficient visible-light-active photocatalysts. Adv Mater 2009, 21: 1286–1290.
McDonald KJ, Choi K-S. A new electrochemical synthesis route for a BiOI electrode and its conversion to a highly efficient porous BiVO4 photoanode for solar water oxidation. Energy Environ Sci 2012, 5: 8553–8557.
Kim TW, Choi KS. Nanoporous BiVO4 photoanodes with dual-layer oxygen evolution catalysts for solar water splitting. Science 2014, 343: 990–994.
Singh AK, Mathew K, Zhuang HL, et al. Computational screening of 2D materials for photocatalysis. J Phys Chem Lett 2015, 6: 1087–1098.
Bhatnagar A, Roy Chaudhuri A, Heon Kim Y, et al. Role of domain walls in the abnormal photovoltaic effect in BiFeO3. Nat Commun 2013, 4: 2835.
Chen B, Li M, Liu Y, et al. Effect of top electrodes on photovoltaic properties of polycrystalline BiFeO3 based thin film capacitors. Nanotechnology 2011, 22: 195201.
Tomar LJ, Chakrabarty BS. Synthesis, structural and optical properties of TiO2–ZrO2 nanocomposite by hydrothermal method. Adv Mat Lett 2013, 4: 64–67.
Li S, Lin Y-H, Zhang B-P, et al. BiFeO3/TiO2 core–shell structured nanocomposites as visible-active photocatalysts and their optical response mechanism. J Appl Phys 2009, 105: 054310.
Hu C-C, Teng H. Structural features of p-type semiconducting NiO as a co-catalyst for photocatalytic water splitting. J Catal 2010, 272: 1–8.
Abe R, Takami H, Murakami N, et al. Pristine simple oxides as visible light driven photocatalysts: Highly efficient decomposition of organic compounds over platinum-loaded tungsten oxide. J Am Chem Soc 2008, 130: 7780–7781.
Miljevic M, Geiseler B, Bergfeldt T, et al. Enhanced photocatalytic activity of Au/TiO2 nanocomposite prepared using bifunctional bridging linker. Adv Funct Mater 2014, 24: 907–915.
Di LJ, Yang H, Hu G, et al. Enhanced photocatalytic activity of BiFeO3 particles by surface decoration with Ag nanoparticles. J Mater Sci: Mater El 2014, 25: 2463–2469.
Hashimoto K, Irie H, Fujishima A. TiO2 photocatalysis: A historical overview and future prospects. Jpn J Applied Phys 2005, 44: 8269–8285.
Qu Y, Cheng R, Su Q, et al. Plasmonic enhancements of photocatalytic activity of Pt/n-Si/Ag photodiodes using Au/Ag core/shell nanorods. J Am Chem Soc 2011, 133: 16730–16733.
Sellappan R, Nielsen MG, González-Posada F, et al. Effects of plasmon excitation on photocatalytic activity of Ag/TiO2 and Au/TiO2 nanocomposites. J Catal 2013, 307: 214–221.
Yang Y-F, Sangeetha P, Chen Y-W. Au/TiO2 catalysts prepared by photo-deposition method for selective CO oxidation in H2 stream. Int J Hydrogen Energ 2009, 34: 8912–8920.
Taing J, Cheng MH, Hemminger JC. Photodeposition of Ag or Pt onto TiO2 nanoparticles decorated on step edges of HOPG. ACS Nano 2011, 5: 6325–6333.
Seabold JA, Choi K-S. Efficient and stable photo-oxidation of water by a bismuth vanadate photoanode coupled with an iron oxyhydroxide oxygen evolution catalyst. J Am Chem Soc 2012, 134: 2186–2192.
Sun Z, Zussman E, Yarin AL, et al. Compound core–shell polymer nanofibers by co-electrospinning. Adv Mater 2003, 15: 1929–1932.
McCann JT, Li D, Xia Y. Electrospinning of nanofibers with core-sheath, hollow, or porous structures. J Mater Chem 2005, 15: 735–738.
Bedford NM, Steckl AJ. Photocatalytic self cleaning textile fibers by coaxial electrospinning. ACS Appl Mater Interfaces 2010, 2: 2448–2455.
Peng X, Santulli AC, Sutter E, et al. Fabrication and enhanced photocatalytic activity of inorganic core–shell nanofibers produced by coaxial electrospinning. Chem Sci 2012, 3: 1262–1272.
Liu Z, Sun DD, Guo P, et al. An efficient bicomponent TiO2/SnO2 nanofiber photocatalyst fabricated by electrospinning with a side-by-side dual spinneret method. Nano Lett 2007, 7: 1081–1085.
Lamba R, Umar A, Mehta SK, et al. Well-crystalline porous ZnO–SnO2 nanosheets: An effective visible-light driven photocatalyst and highly sensitive smart sensor material. Talanta 2015, 131: 490–498.
Li G, Wu L, Li F, et al. Photoelectrocatalytic degradation of organic pollutants via a CdS quantum dots enhanced TiO2 nanotube array electrode under visible light irradiation. Nanoscale 2013, 5: 2118–2125.
Chouhan N, Yeh CL, Hu S-F, et al. Photocatalytic CdSe QDs-decorated ZnO nanotubes: An effective photoelectrode for splitting water. Chem Commun 2011, 47: 3493–3495.
Zhang S, Peng F, Wang H, et al. Electrodeposition preparation of Ag loaded N-doped TiO2 nanotube arrays with enhanced visible light photocatalytic performance. Catal Commun 2011, 12: 689–693.
Zhou W, Pan K, Qu Y, et al. Photodegradation of organic contamination in wastewaters by bonding TiO2/single-walled carbon nanotube composites with enhanced photocatalytic activity. Chemosphere 2010, 81: 555–561.
Li H, Bian Z, Zhu J, et al. Mesoporous titania spheres with tunable chamber stucture and enhanced photocatalytic activity. J Am Chem Soc 2007, 129: 8406–8407.
Wang M, Sun L, Lin Z, et al. p–n Heterojunction photoelectrodes composed of Cu2O-loaded TiO2 nanotube arrays with enhanced photoelectrochemical and photoelectrocatalytic activities. Energy Environ Sci 2013, 6: 1211–1220.
Song KY, Park MK, Kwon YT, et al. Preparation of transparent particulate MoO3/TiO2 and WO3/TiO2 films and their photocatalytic properties. Chem Mater 2001, 13: 2349–2355.
Bartl MH, Puls SP, Tang J, et al. Cubic mesoporous frameworks with a mixed semiconductor nanocrystalline wall structure and enhanced sensitivity to visible light. Angew Chem Int Edit 2004, 43: 3037–3040.
Jang JS, Choi SH, Park H, et al. A composite photocatalyst of CdS nanoparticles deposited on TiO2 nanosheets. J Nanosci Nanotechno 2006, 6: 3642–3646.
Li Z, Shen Y, Yang C, et al. Significant enhancement in the visible light photocatalytic properties of BiFeO3–graphene nanohybrids. J Mater Chem A 2013, 1: 823–829.
Li B, Cao H. ZnO@graphene composite with enhanced performance for the removal of dye from water. J Mater Chem 2011, 21: 3346–3349.
Liu S, Yang M-Q, Tang Z-R, et al. A nanotree-like CdS/ZnO nanocomposite with spatially branched hierarchical structure for photocatalytic fine-chemical synthesis. Nanoscale 2014, 6: 7193–7198.
Yang G, Yan W, Zhang Q, et al. One-dimensional CdS/ZnO core/shell nanofibers via single-spinneret electrospinning: Tunable morphology and efficient photocatalytic hydrogen production. Nanoscale 2013, 5: 12432–12439.
An X, Yu JC, Wang Y, et al. WO3 nanorods/graphene nanocomposites for high-efficiency visible-light-driven photocatalysis and NO2 gas sensing. J Mater Chem 2012, 22: 8525–8531.
Sun Y, Qu B, Liu Q, et al. Highly efficient visible-light-driven photocatalytic activities in synthetic ordered monoclinic BiVO4 quantum tubes-graphene nanocomposites. Nanoscale 2012, 4: 3761–3767.
Xie Z, Liu X, Wang W, et al. Enhanced photoelectrochemical and photocatalytic performance of TiO2 nanorod arrays/CdS quantum dots by coating TiO2 through atomic layer deposition. Nano Energy 2015, 11: 400–408.
Zhou N, Polavarapu L, Gao N, et al. TiO2 coated Au/Ag nanorods with enhanced photocatalytic activity under visible light irradiation. Nanoscale 2013, 5: 4236–4241.
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Publication history

Received: 03 June 2015
Revised: 21 June 2015
Accepted: 24 June 2015
Published: 08 September 2015
Issue date: September 2015


© The author(s) 2015


This work was supported by the National Natural Science Foundation of China (Nos. 51272121, 51221291, 51328203, and 51025205).

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