Abstract: With the photocatalytic technology, people can make further progress in tackling the potential threat of environmental pollution and energy shortage, by effectively utilize solar energy to degrade pollutants in water or atmosphere and to generate hydrogen via photocatalyzed water splitting reactions. Titanium dioxide (TiO2), currently the most widely used photocatalyst with excellent photocatalytic activity, high chemical stability, low price and non-toxicity, suffers great limitation in application due to its wide band gap and rapid recombination of electrons and holes. Over the past decade or more, researchers have developed a series of methods to improve the photocatalytic activity of TiO2, including adjusting TiO2 crystal and morphology, sensitizing TiO2 using quantum dot or organic dye, depositing precious metal on catalyst surface, doping transition metal ion or non-metal ion. The sensitization of TiO2 with quantum dot refers to the combination of TiO2 and quantum dots, which can adjust the band width of TiO2, broaden the photoresponse range of the photocatalyst. However, the traditional quantum dots mostly contain toxic heavy metal ions, and will no doubt be a hazard to environment and human health. This urges intensive research efforts to seek non-toxic fluorescent nanomaterials, among which carbon quantum dots (CDs or CQDs) have displayed impressive potential and representativeness. CDs, consisting of sp2/sp3 hybridized carbon atoms and holding various surface functional groups, enjoy the advantages of abundant ingredient, stable physical and chemical performance, non-toxicity, good biocompatibility, ease of functionalization, and excellent resistance to photobleaching, compared with the traditional quantum dots. In addition, CDs possess photoinduced electron transfer character and photosensitivity, and part of them display excellent up-conversion photoluminescence. By integrating CDs and TiO2, we can obtain CDs-TiO2 composite photocatalyst which surpasses the traditional hazardous quantum dots by virtue of its low toxicity. And on the other hand, it has an enhanced ultraviolet light absorption, and also extended visible light absorption and near-infrared light absorption, and moreover, can inhibit the recombination of photogenerated electrons and holes, thus effectively promoting the photocatalytic performance and having broad application prospects in the field of photocatalysis. Previous works intend to improve the photocatalytic activity of CDs-TiO2 photocatalysts mainly from the prospectives of regulating TiO2 and regulating CDs. The former mainly includes the adjustment of TiO2 crystal and crystal surface, the control of TiO2 morphology and the hybridization of TiO2. The latter mainly includes the hybridization of CDs, the change of the particle size and loading capacity of CDs. This review analyzes the hypothesized photocatalytic mechanism of CDs-TiO2 composite photocatalysts, and describes the research results with respect to the above mentioned regulation methods. Finally, it briefly discusses the preparation and application of CDs-TiO2 as well as the future development trend.
1 Lee K M, Lai C W, Ngai K S, et al. Recent developments of zinc oxide based photocatalyst in water treatment technology: A review[J].Water Research,2016,88:428. 2 Zhang J, Xiao G, Xiao F X, et al. Revisiting one-dimensional TiO2 based hybrid heterostructures for heterogeneous photocatalysis: A critical review[J].Materials Chemistry Frontiers,2017,1:231. 3 Bhanvase B A, Shende T P, Sonawane S H. A review on graphene-TiO2 and doped graphene-TiO2 nanocomposite photocatalyst for water and wastewater treatment[J].Environmental Technology Reviews,2017,6(1):1. 4 Yun H J, Paik T, Diroll B, et al. Nanocrystal size-dependent efficiency of quantum dot sensitized solar cells in the strongly coupled CdSe nanocrystals/TiO2 system[J].ACS Applied Materials and Interfaces,2016,8(23):14692. 5 Sudhakar C, Selvankumar T, Selvam K, et al. Bauhinia purpurea L. flower mediated dye used as sensitizers for TiO2 based dye-sensitized solar cells[J].International Journal of Advanced Science and Engineering,2016,2(4):209. 6 Tang Y, Hao R, Fu Y, et al. Carbon quantum dot/mixed crystal TiO2 composites via a hydrogenation process: An efficient photoca-talyst for the hydrogen evolution reaction[J].RSC Advances,2016,6(99):96803. 7 Du G, Yuan J, Zhu C. Hierarchical nanostructures of Ag3PO4 on TiO2 nanofibers with enhanced photocatalytic activity for the degradation of rhodamine B[J].Journal of Materials Science: Materials in Electronics,2017,28(10):7307. 8 Choi Y, Kim H, Moon G, et al. Boosting up the low catalytic activity of silver for H2 production on Ag/TiO2 photocatalyst: Thiocyanate as a selective modifier[J].ACS Catalysis,2016,6(2):821. 9 Xu M, Wang Y, Geng J, et al. Photodecomposition of NOxon Ag/TiO2 composite catalysts in a gas phase reactor[J].Chemical Engineering Journal,2017,307:181. 10 Du J, Wang H, Chen H, et al. Synthesis and enhanced photocataly-tic activity of black porous Zr-doped TiO2 monoliths[J].Nano,2016,11(6):1650068. 11 Chen X, Xie Z, Liang Y, et al. Hybridizing TiO2 with nitrogen-doped carbon: A new route to a highly visible light-active photocatalyst[J].Chemistry Select,2017,2(4):1565. 12 Xu X, Song W. Enhanced H2 production activity under solar irradiation over N-doped TiO2 prepared using pyridine as a precursor: A typical sample of N-doped TiO2 series[J].Materials Technology,2017,32(1):52. 13 Benítez-martínez S, Valcárcel M. Graphene quantum dots in analytical science[J].TrAC Trends in Analytical Chemistry,2015,72:93. 14 Yu H, Shi R, Zhao Y, et al. Smart utilization of carbon dots in semi-conductor photocatalysis[J].Advanced Materials,2016,28(43):9454. 15 Liu Y, Yu Y X, Zhang W D. Carbon quantum dots-doped CdS microspheres with enhanced photocatalytic performance[J].Journal of Alloys and Compounds,2013,569:102. 16 Ming H, Ma Z, Liu Y, et al. Large scale electrochemical synthesis of high quality carbon nanodotsand their photocatalytic property[J].Dalton Transactions,2012,41(31):9526. 17 Cao L, Sahu S, Anilkumar P, et al. Carbon nanoparticles as visible-light photocatalysts for efficient CO2 conversion and beyond[J].Journal of the American Chemical Society,2011,133(13):4754. 18 Li H, Liu R, Lian S, et al. Near-infrared light controlled photocatalytic activity of carbon quantum dots for highly selective oxidation reaction[J].Nanoscale,2013,5(8):3289. 19 Li H, Liu R, Liu Y, et al. Carbon quantum dots/Cu2O composites with protruding nanostructures and their highly efficient (near) infrared photocatalytic behavior[J].Journal of Materials Chemistry,2012,22(34):17470. 20 Wang H, Wei Z, Matsui H, et al. Fe3O4/carbon quantum dots hybrid nanoflowers for highly active and recyclable visible-light driven photocatalyst[J].Journal of Materials Chemistry A,2014,2(38):15740. 21 Xie S, Su H, Wei W, et al. Remarkable photoelectrochemical performance of carbon dots sensitized TiO2 under visible light irradiation[J].Journal of Materials Chemistry A,2014,2(39):16365. 22 Huang Z, Fang L, Dong W, et al. Design and fabrication of carbon quantum dots/TiO2 photonic crystal complex with enhanced photocatalytic activity[J].Journal of Nanoscience and Nanotechnology,2014,14(6):4156. 23 Li H, He X, Kang Z, et al. Water-soluble fluorescent carbon quantum dots and photocatalyst design[J].Angewandte Chemie International Edition,2010,49(26):4430. 24 Li H, Zhu Y, Cao H, et al. Preparation and characterization of photocatalytic carbon dots-sensitized electrospun titania nanostructured fibers[J].Materials Research Bulletin,2013,48(2):232. 25 Zhou Q, Zhou J, Zeng M, et al. Photoelectrochemical performance of quantum dot-sensitized TiO2 nanotube arrays: A study of surface modification by atomic layer deposition coating[J].Nanoscale Research Letters,2017,12(1):261. 26 Zhuo S, Shao M, Lee S T. Upconversion and downconversion fluorescent graphene quantum dots: Ultrasonic preparation and photocatalysis[J].ACS Nano,2012,6(2):1059. 27 Pan J, Liu G, Lu G Q M, et al. On the true photoreactivity order of {001},{010}, and {101} facets of anatase TiO2 crystals[J].Angewandte Chemie International Edition,2011,50(9):2133. 28 Maitani M M, Tanaka K, Mochizuki D, et al. Enhancement of photoexcited charge transfer by {001} facet-dominating TiO2 nanoparticles[J].The Journal of Physical Chemistry Letters,2011,2(20):2655. 29 Yu X, Liu J, Yu Y, et al. Preparation and visible light photocataly-tic activity of carbon quantum dots/TiO2 nanosheet composites[J].Carbon,2014,68:718. 30 Xue J, Song F, Yin X W, et al. Cellulose nanocrystal-templated synthesis of mesoporous TiO2 with dominantly exposed (001) facets for efficient catalysis[J].ACS Sustainable Chemistry and Engineering,2017,5(5):3721. 31 Wang W, Ni Y, Xu Z. One-step uniformly hybrid carbon quantum dots with high-reactive TiO2 for photocatalytic application[J].Journal of Alloys and Compounds,2015,622:303. 32 Tian J, Leng Y, Zhao Z, et al. Carbon quantum dots/hydrogenated TiO2 nanobelt heterostructures and their broad spectrum photocatalytic properties under UV, visible, and near-infrared irradiation[J].Nano Energy,2015,11:419. 33 Liu R, Li H, Duan L, et al. In situ synthesis and enhanced visible light photocatalytic activity of C-TiO2 microspheres/carbon quantum dots[J].Ceramics International,2017,43(12):8648. 34 Yu H, Zhao Y, Zhou C, et al. Carbon quantum dots/TiO2 compo-sites for efficient photocatalytic hydrogen evolution[J].Journal of Materials Chemistry A,2014,2(10):3344. 35 Pan J, Sheng Y, Zhang J, et al. Preparation of carbon quantum dots/TiO2 nanotubes composites and their visible light catalytic applications[J].Journal of Materials Chemistry A,2014,2(42):18082. 36 Qu A, Xie H, Xu X, et al. High quantum yield graphene quantum dots decorated TiO2 nanotubes for enhancing photocatalytic activity[J].Applied Surface Science,2016,375:230. 37 Zhang Y Q, Ma D K, Zhang Y G, et al. N-doped carbon quantum dots for TiO2-based photocatalysts and dye-sensitized solar cells[J].Nano Energy,2013,2(5):545. 38 Liu J, Zhu W, Yu S, et al. Three dimensional carbogenic dots/TiO2 nanoheterojunctions with enhanced visible light-driven photocatalytic activity[J].Carbon,2014,79:369. 39 Dai Y, Long H, Wang X, et al. Versatile graphene quantum dots with tunable nitrogen doping[J].Particle and Particle Systems Cha-racterization,2014,31(5):597. 40 Safardoust-hojaghan H, Salavati-niasari M. Degradation of methy-lene blue as a pollutant with N-doped graphene quantum dot/titanium dioxide nanocomposite[J].Journal of Cleaner Production,2017,148:31. 41 Qu D, Zheng M, Du P, et al. Highly luminescent S, N co-doped graphene quantum dots with broad visible absorption bands for visible light photocatalysts[J].Nanoscale,2013,5(24):12272. 42 Qu D, Sun Z, Zheng M, et al. Three colors emission from S, N co-doped graphene quantum dots for visible light H2 production and bioimaging[J].Advanced Optical Materials,2015,3(3):360. 43 Ma Z, Zhang Y L, Wang L, et al. Bio-inspired photoelectric conversion system based on carbon quantum dot doped dye-semiconductor complex[J].ACS Applied Materials and Interfaces,2013,5(11):5080. 44 Bian J, Huang C, Wang L, et al. Carbon dot loading and TiO2 nanorod length dependence of photoelectrochemical properties in carbon dot/TiO2 nanorod array nanocomposites[J].ACS Applied Materials and Interfaces,2014,6(7):4883. 45 Long R, Casanova D, Fang W H, et al. Donor-acceptor interaction determines the mechanism of photoinduced electron injection from graphene quantum dots into TiO2: π-stacking supersedes covalent bonding[J].Journal of the American Chemical Society,2017,139(7):2619. 46 Miao R, Luo Z, Zhong W, et al. Mesoporous TiO2 modified with carbon quantum dots as a high-performance visible light photocatalyst[J].Applied Catalysis B: Environmental,2016,189:26. 47 Chen J, Shu J, Anqi Z, et al. Synthesis of carbon quantum dots/TiO2 nanocomposite for photo-degradation of rhodamine B and cefradine[J].Diamond and Related Materials,2016,70:137. 48 Ke J, Li X, Zhao Q, et al. Upconversion carbon quantum dots as visible light responsive component for efficient enhancement of photocatalytic performance[J].Journal of Colloid and Interface Science,2017,496:425. 49 Li F, Tian F, Liu C, et al. One-step synthesis of nanohybrid carbon dots and TiO2 composites with enhanced ultraviolet light active photocatalysis[J].RSC Advances,2015,5(11):8389. 50 Hou Y, Lu Q, Wang H, et al. One-pot electrochemical synthesis of carbon dots/TiO2 nanocomposites with excellent visible light photocatalytic activity[J].Materials Letters,2016,173:13. 51 Wang J, Gao M, Ho G W. Bidentate-complex-derived TiO2/carbon dot photocatalysts: In situ synthesis, versatile heterostructures, and enhanced H2 evolution[J].Journal of Materials Chemistry A,2014,2(16):5703. 52 Wang J, Ng Y H, Lim Y F, et al. Vegetable-extracted carbon dots and their nanocomposites for enhanced photocatalytic H2 production[J].RSC Advances,2014,4(83):44117. 53 Zhang X, Wang F, Huang H, et al. Carbon quantum dot sensitized TiO2 nanotube arrays for photoelectrochemical hydrogen generation under visible light[J].Nanoscale,2013,5(6):2274. 54 Yu X, Liu R, Zhang G, et al. Carbon quantum dots as novel sensitizers for photoelectrochemical solar hydrogen generation and theirsize-dependent effect[J].Nanotechnology,2013,24(33):335401. 55 Wei J, Li X D, Wang H Z, et al. Nitrogen doped carbon quantum dots/titanium dioxide composites for hydrogen evolution under sunlight[J].Journal of Inorganic Materials,2015,30(9):925(in Chinese). 魏婕,李雪冬,王宏志,等.NCDs/TiO2复合材料的制备及其在太阳光下催化制氢的应用[J].无机材料学报,2015,30(9):925. 56 Saud P S, Pant B, Alam A M, et al. Carbon quantum dots anchored TiO2 nanofibers: Effective photocatalyst for waste water treatment[J].Ceramics International,2015,41(9):11953. 57 Sun M, Ma X, Chen X, et al. A nanocomposite of carbon quantum dots and TiO2 nanotube arrays: Enhancing photoelectrochemical and photocatalytic properties[J].RSC Advances,2014,4(3):1120. 58 Mirtchev P, Henderson E J, Soheilnia N, et al. Solution phase synthesis of carbon quantum dots as sensitizers for nanocrystalline TiO2 solar cells[J].Journal of Materials Chemistry,2012,22(4):1265. 59 Zhang X, Liu C, Li Z, et al. An easily prepared carbon quantum dots and employment for inverted organic photovoltaic devices[J].Chemical Engineering Journal,2017,315:621. 60 Li H, Shi W, Huang W, et al. Carbon quantum dots/TiOx electron transport layer boosts efficiency of planar heterojunction perovskite solar cells to 19%[J].Nano Letters,2017,17(4):2328. 61 Jin J, Chen C, Li H, et al. Enhanced performance and photostability of perovskite solar cells by introduction of fluorescent carbon dots[J].ACS Applied Materials and Interfaces,2017,9(16):14518. 62 Ming H, Yan Y, Ming J, et al. Porous TiO2 nanoribbons and TiO2 nanoribbon/carbon dot composites for enhanced Li-ion storage[J].RSC Advances,2014,4(25):12971. 63 Wang F, Zhang Y, Liu Y, et al. Opto-electronic conversion logic behaviour through dynamic modulation of electron/energy transfer states at the TiO2-carbon quantum dot interface[J].Nanoscale,2013,5(5):1831. 64 Le Z, Liu F, Nie P, et al. Pseudocapacitive sodium storage in mesoporous single-crystal-like TiO2-graphene nanocomposite enables high-performance sodium-ion capacitors[J].ACS Nano,2017,11(3):2952.
渝公网安备50019002502923号 版权所有：《材料导报》编辑部
2018, Vol. 32 
