Synthesis of 3D CQDs/urchin-like and yolk-shell TiO2 hierarchical structure with enhanced photocatalytic properties

A novel CQDs/TiO₂ hierarchical structure with enhanced photocatalytic properties was achieved by uniformly decorating urchin-like and yolk-shell TiO₂ microspheres (UYTMs) with carbon quantum dots (CQDs) through an environmentally friendly hydrothermal process. The CQDs were firstly synthesized by the electrochemical method, and the TEM, Raman and PL characterizations strongly indicated that the as-prepared CQDs exhibited good dispersion, high crystallinity and unique up-conversion properties. The UYTMs synthesized by a NaOH-assisted hydrothermal process showed stable 3D hierarchical structure and large surface area, which was beneficial for light absorption and contacting with contamination. The good combination of CQDs and UYTMs was further successfully achieved during the hydrothermal process, and demonstrated by a series of tests. The photocatalytic experiments suggested that the CQDs/UYTMs exhibited better photocatalytic activities than the pure UYTMs and P25 under both visible and UV light irradiation. The CQDs/UYTMs combining with 6?wt% of CQDs showed the best photocatalytic efficiency, while excessive CQDs tended to inhibit the photocatalytic activity. According to the results and discussions, a possible mechanism in improving the photocatalytic efficiency of the CQDs/UYTMs is significantly proposed. The up-conversion property of CQDs can broaden the absorption spectrum of CQDs/UYTMs to the visible light. Moreover, the CQDs, as the electron reservoirs, are efficient to separate the electrons and holes, leading to an improved photocatalytic activity of CQDs/UYTMs.     

碳量子点在光催化领域的应用

碳量子点(carbon quantum dots,CQDs)是一种新型的零维碳纳米材料,具有易制备、低毒、生物兼容性好,及良好的光稳定性等特点,在生物成像、传感器及电致发光器件等领域具有潜在的应用前景。除此之外,碳量子点的尺寸依赖性、上转换发光性质、响应波长从近红外区延伸到可见区等优点使其成为太阳能光催化材料领域的"新宠"。就碳量子点在光催化领域的应用进行了综述。     

Synthesis of carbon quantum dots/TiO2 nanocomposite for photo-degradation of Rhodamine B and cefradine

Pure TiO₂ and carbon quantum dots (CQDs)-doped TiO₂ nanocomposite (CQDs/TiO₂ nanocomposite) were prepared by a sol-gel approach for photocatalytic removal of Rhodamine B and cefradine. Analyses by Transmission electronmicroscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), UV–visible spectroscopy and X-ray powder diffraction (XRD) confirmed the successful formation of CQDs/TiO₂ heterostructure. The as-prepared TiO₂ and CQDs/TiO₂ composite possessed small particles, spherical-like shape, and anatase crystal form. Meanwhile, Rhodamine B and cefradine were chosen to evaluate the photocatalytic activity of TiO₂ and CQDs/TiO₂ composite. Results revealed that with the facile decoration of CQDs, the absorption of photocatalyst was extended into visible light region and photocatalytic activity was improved in comparison with pure TiO₂. Furthermore, the mechanism for the improvement of the photocatalytic performance of the composites was discussed on the basis of the results. CQDs play an important role in the photocatalytic process, due to their superior ability to extend the visible absorption and produce more electrons and electron–hole pairs for the degradation of pollutants. In all, the paper offers further insights into the development of CQDs/TiO₂ nanocomposite as photocatalyst for the degradation of antibiotics.     

Highly efficient visible/near-infrared light photocatalytic degradation of antibiotic wastewater over 3D yolk-shell ZnFe2O4 supported 0D carbon dots with up-conversion property

The development of effective visible and near-infrared photocatalysts is highly promising in the current field of photocatalysis. Herein, carbon dots/ZnFe2O4(CDs/ZFO) with coating zero dimensional(0D) CDs on the surface of three dimensional(3D) yolk-shell ZFO spheres was designed and synthesized via a selftemplated solvothermal method. The as-prepared CDs/ZFO composites displayed outstanding visible and near-infrared photocatalytic degradation activity of tetracycline(TC), and the optimal 3% CDs...     

基于表面等离子体共振效应的Ag(Au)/半导体纳米复合光催化剂的研究进展

由具有表面等离子体共振(surface plasmon resonance,SPR)效应的贵金属(Ag、Au等)纳米粒子和半导体纳米结构组成的纳米复合光催化剂具有优异的可见光光催化活性,成为新型光催化材料的研究热点之一。本文综述了Ag(Au)/半导体纳米复合光催化剂的制备方法、基本性质以及光催化应用方面的一些重要研究进展;重点介绍了Ag(Au)等纳米粒子的表面等离子共振增强可见光催化活性的机理,以及Ag(Au)纳米粒子与不同类型半导体复合的光催化剂的光催化性能,其中所涉及的半导体包括金属氧化物、硫化物和其他一些半导体;本领域未来几年的研究热点将集中于新型高效的Ag(Au)/半导体纳米复合光催化剂的微结构调控及其用于可见光驱动有机反应的机理研究。本文为基于SPR效应构建Ag(Au)/半导体纳米复合光催化剂的研究提供了有力的参考依据,并且指出Ag(Au)/半导体纳米复合光催化剂的研究是发展可见光高效光催化剂的重要方向。     

g-C3N4/CQDs光催化材料的制备及性能

采用高温热解法制备了石墨相氮化碳(g-C_3N_4),将其与碳量子点(CQDs)进行水热复合,得到g-C_3N_4/CQDs复合光催化剂。采用SEM、TEM、FTIR、XRD、UV-Vis/DRS、XPS、N2吸附-脱附等温线手段对制备的复合光催化剂进行了表征,以罗丹明B(Rh B)为模拟污染物,考察了g-C_3N_4/CQDs的可见光催化活性及稳定性。结果表明:与g-C_3N_4相比,g-C_3N_4/CQDs对可见光吸收强度增加,同时其吸收波长向可见光区发生红移;当CQDs含量为1.5%(以g-C_3N_4质量为基准)时,所得g-C_3N_4/CQDs光催化材料的催化活性最佳,其对Rh B的光催化降解率是54.5%,是g-C_3N_4光催化降解率的1.38倍,化学反应动力学拟合相关系数R2=0.9982。且g-C_3N_4/CQDs循环使用3次后,其催化降解率仍保持在50%以上。光催化机理研究表明,空穴(h+)、超氧阴离子自由基(·O2–)、过氧化氢分子(H2O2)和羟基自由基(·OH)都是光催化过程中的主要活性物种,四者氧化作用大小依次为:h+·O2– H2O2·OH。     

Bi2MoO6@CQDs/TiO2纳米管阵列的制备与光电催化性能

为提高TiO₂的可见光光电催化活性,本文用Bi₂MoO₆和碳量子点(CQDs)对TiO₂纳米管阵列(TNA)进行了改性。以CQDs、Bi(NO₃)₃·5H₂O和Na₂MoO₄为原料,通过简单的溶剂热法,在TNA中沉积了CQDs和Bi₂MoO₆,成功制备了新型Bi₂MoO₆@CQDs/TNA。扫描电镜(SEM)和元素mapping分析结果表明,CQDs和Bi₂MoO₆成功涂覆在TNA管壁上。通过在可见光下降解甲基橙(MO)溶液,评价了所制备的光催化剂的光电催化性能。结果显示,经3 h的光电催化降解,Bi₂MoO₆@CQDs/TNA对MO的去除率比Bi₂MoO₆/TNA高32%。CQDs优异的上转换光致发光(UCPL)性能促进了TiO₂在可见光下被激发产生光生载流子,同时Bi₂MoO₆与TiO₂的耦合抑制了光生载流子的复合,从而提高了Bi₂MoO₆@CQDs/TNA的光电催化活性。     

非金属掺杂的第二代二氧化钛光催化剂研究进展

寻求廉价、环境友好并具有可见光光催化活性的第二代光催化剂将是光催化发展进一步走向实用化的关键。氮掺杂的TIO2是新发现的具有可见光光催化活性的复合光催化剂,非金属掺杂可以使复合物的复合禁带宽度小于TIO2的禁带宽度,从而使TIO2的吸收边向可见光移动。对TIO2的氮、碳、硫、卤素掺杂国内外研究现状进行了系统评述,分析了提高TIO2可见光活性的原因,指出非金属元素特别是氮元素的阴离子掺杂是在不降低紫外光催化活性的基础上实现可见光响应的较好方法。     

Property Characterization and Photocatalytic Activity Evaluation of BiGdO3 Nanoparticles under Visible Light Irradiation

BiGdO₃ nanoparticles were prepared by a solid-state reaction method and applied in photocatalytic degradation of dyes in this study. BiGdO₃ was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, UV-Vis diffuse reflectance spectroscopy and transmission electron microscopy. The results showed that BiGdO₃ crystallized well with the fluorite-type structure, a face-centered cubic crystal system and a space group Fm3m 225. The lattice parameter of BiGdO₃ was 5.465 angstrom. The band gap of BiGdO₃ was estimated to be 2.25 eV. BiGdO₃ showed a strong optical absorption during the visible light region. Moreover, the photocatalytic activity of BiGdO₃ was evaluated by photocatalytic degradation of direct dyes in aqueous solution under visible light irradiation. BiGdO₃ demonstrated excellent photocatalytic activity in degrading Direct Orange 26 (DO-26) or Direct Red 23 (DR-23) under visible light irradiation. The photocatalytic degradation of DO-26 or DR-23 followed the first-order reaction kinetics, and the first-order rate constant was 0.0046 or 0.0023 min⁻¹ with BiGdO₃ as catalyst. The degradation intermediates of DO-26 were observed and the possible photocatalytic degradation pathway of DO-26 under visible light irradiation was provided. The effect of various operational parameters on the photocatalytic activity and the stability of BiGdO₃ particles were also discussed in detail. BiGdO₃/(visible light) photocatalysis system was confirmed to be suitable for textile industry wastewater treatment.     

Synthesis and characterization of carbon-doped titania as a visible-light-sensitive photocatalyst

The synthesis and use of carbon-doped TiO₂ particles in photocatalysis under visible light are demonstrated. The carbon-doped titania with its mesoporous structure was prepared by chemical modification and characterized by several techniques including X-ray diffraction, transmission electron spectroscopy (TEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectra (EPR), and diffuse reflectance UV-Vis. absorption spectra, with emphasis on the effect of carbon as a doping compound to the titania. Based on EPR data, the photocatalytic activity by visible light can be ascribed to the trapping of electrons at interior sites of the carbon-doped titania between the valence and conduction bands in the titania band structure, and is able to activated by visible light of a wavelength of up to 550 nm. The photocatalytic activity of the carbon-doped TiO₂ nanoparticles was evaluated by examining the decomposition of phenol by irradiation with artificial solar light (>420 nm) and the results were compared with those using Degussa P25, a commercially available titania nanomaterial.     

CdS/TiO2复合纳米粒子的制备及其产氢性能研究

采用化学沉淀法制备了CdS包覆TiO2（CdS/TiO2）复合纳米粒子,利用XRD、TEM、SEM、UV-vis吸收光谱等对其进行了表征分析,并以可见光分解水制氢为探针反应考察了复合纳米粒子的活性。结果表明,CdS/TiO2 复合纳米粒子的颗粒大小约为40nm,TiO2 以锐钛矿型存在,CdS以六方相存在;复合纳米粒子的吸收光谱较TiO2 发生“红移”,大幅拓宽了对可见光区的吸收范围。光解水制氢实验表明,CdS/TiO2 复合纳米粒子具有良好的可见光释氢活性和光学稳定性。     

In situ synthesis and enhanced visible light photocatalytic activity of C-TiO2 microspheres/carbon quantum dots

TiO₂ microspheres and TiO₂/carbon quantum dots (CQDs) composites with different CQDs contents were successfully synthesized via solvothermal and in situ hydrothermal method. The structure and morphology of the prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). Results showed that carbon elements were successfully doped into the TiO₂ lattice (C-TiO₂) and CQDs were hybrid with C-TiO₂ microspheres. The X-ray photoelectron spectroscope (XPS), valence band XPS (VB-XPS) and UV–vis diffuse reflectance spectra (DRS) analyses revealed that carbon doped into TiO₂ microspheres could lead to local energy levels in the band structure and generate valence band tails to absorb visible light. The photocatalytic activities of these samples were evaluated by the photodegradation of Rhodamine B (RhB) under visible light irradiation. C-TiO₂/CQDs samples presented an enhanced photocatalytic performance compared with pristine TiO₂, which could be attributed to the present of CQDs, acting as adsorption sites for RhB molecules and charge separation centers to impede the recombination and prolong the life time of electron and hole pairs.     

非金属掺杂对TiO2可见光吸收影响的研究现状

TiO2在光催化领域有广阔的应用前景,但大的禁带宽度限制其不能有效利用太阳能,当前研究的重点是开发能有效利用太阳光的光催化剂.许多研究通过表面改性和掺杂过渡金属离子扩大光谱响应吸收范围和提高光催化活性,概述了近年来关于TiO2改性的工艺、机理及优缺点,重点总结了非金属元素掺杂的研究,并对今后的研究作了展望.     

Porous ZnO-ZnSe nanocomposites for visible light photocatalysis

We report the synthesis of porous ZnO-ZnSe nanocomposites for use in visible light photocatalysis. Porous ZnO nanostructures were synthesized by a microwave-assisted hydrothermal reaction then converted into porous ZnO-ZnSe nanocomposites by a microwave-assisted dissolution-recrystallization process using an aqueous solution containing selenium ions. ZnO and ZnSe nanocrystallites of the nanocomposites were well-mixed (rather than forming simple core-shell (ZnO-ZnSe) structures), particularly, in the outer regions. Both ZnO and ZnSe were present at the surface and exposed to the environment. The porous ZnO-ZnSe nanocomposites showed absorption bands in the visible region as well as in the UV region. The porous ZnO-ZnSe nanocomposites had much higher activities than the porous ZnO nanostructures. Control experiments using cutoff filters revealed that the main photocatalytic activity of the synthesized nanostructures arose from photo-excitation of the semiconductor (ZnO or ZnSe) via absorption of light of an energy equal to or exceeding the band gap energy.     

新型g-C3N4/CuS复合材料的制备及光催化研究

一步水热法合成CuS修饰的石墨相氮化碳(g-C3N4/CuS)复合光催化剂,通过FE-SEM、XRD、FTIR、UV-Vis-DRS等手段对其进行了表征,利用Cr(VI)溶液考察了g-C3N4/CuS在可见光下的光催化还原性能.实验结果表明,g-C3N4/CuS复合光催化剂的光催化活性明显优于单一的g-C3N4和CuS.可见光照射下,180 min内Cr(VI)的去除率可达70％以上.CuS的引入不仅扩宽了g-C3N4的可见光吸收范围,而且降低了g-C3N4光生电子和空穴的复合率,从而显著提高g-C3N4的光催化活性.该复合材料的催化活性受溶液的pH值影响较大,酸性条件下更有利于光催化反应的进行;共存低浓度腐殖酸对Cr(VI)的去除没有显著影响.g-C3N4/CuS具有良好的可见光催化活性,可用于废水中Cr(VI)的光催化还原去除.     

Visible‐Light‐Induced Degradation of Methylene Blue by SrBi3VO8 Nanoparticles

Nanosized particles of strontium bismuth vanadate SrBi₃VO₈ were prepared via the Pechini method on the base of citrate‐complexation route. The samples were characterized using X‐ray powder diffraction (XRD), scanning electron microscope (SEM), energy dispersive X‐ray spectra (EDX), X‐ray photoelectron spectroscopic (XPS), and UV–vis absorption spectrum. This bismuth‐containing vanadate presents an efficient absorption in the UV–visible light wavelength region with a narrow band‐gap energy of 2.36 eV and an indirect allowed electronic transition. It is well‐known that hybridization of the 6s and 6p orbitals of Bi³⁺ could result in lone electron pair and yield some very interesting properties. The photocatalytic activities of SrBi₃VO₈ nanoparticles were evaluated by the photodegradation of methylene blue (MB) under visible light irradiation in air atmosphere. These results indicate that SrBi₃VO₈ could be a potential photocatalyst driven by visible light. To understand the charge generation and separation process, the luminescence as well as the decay lifetimes was investigated in the same samples for photocatalysis.     

氮掺杂TiO2可见光光催化研究进展

实现TiO2的可见光催化一直是光催化领域的热点和难点。近年来,掺氮TiO2由于在可见光区具有较好的光催化活性引起了科研工作者的关注,本文详细介绍了掺氮TiO2的制备方法、掺杂的氮的化学态和可见光响应机理的情况,对未来的发展趋势作了预测。     

NH2-MIL-125(Ti)光催化剂的研究进展

NH₂-MIL-125(Ti)具有较大的比表面积和孔隙率、均匀的孔道分布以及功能可调节性等优点,在光催化领域具有重要的应用前景,但同时也存在光生电子-空穴复合快和可见光利用率低等缺点。首先,介绍了钛酯的类型、反应物浓度、反应溶剂体积比和晶化时间对NH₂-MIL-125(Ti)晶体形貌的影响;接着,总结了提高NH₂-MIL-125(Ti)光催化活性的方法;然后,综述了国内外NH₂-MIL-125(Ti)光催化剂的应用现状;最后,提出了NH₂-MIL-125(Ti)光催化剂的发展方向。     

Preparation and photocatalytic performance of Bi nanoparticles by microwave-assisted method using ascorbic acid as reducing agent

Bismuth nanoparticles (NPs) were prepared by using microwave (MW) as heating source and ascorbic acid as reducing agent. Pure phase of Bi NPs was obtained and the size was uniform with the mean value of 70 nm. The visible light absorption was good and the optical band gap was 1.77 eV. The photocatalytic efficiency was 2.7 times that of the sample by solvothermal method for degradation of methyl blue (MB) under visible light irradiation. The hydroxyl radicals during photocatalysis were detected due to the transition of Bi from semimetal to semiconductor. The small size effect was considered to contribute a lot to the efficient photocatalytic activity.     

Role of Conducting Polymers in Enhancing TiO2-based Photocatalytic Dye Degradation: A Short Review

Research in the field of TiO₂-based photocatalysis has gained wide attention to address important energy and environmental problem. Lately, the use of conducting polymers as photosensitizers has proven to immensely enhance photodegradation by exhibiting excellent photocatalytic activity under both ultraviolet light and natural sunlight irradiation which is not possible using semiconductors alone. Considering the unique performance of conducting polymer-based nanocomposites in photocatalysis, the present review provides the recent advances in the development of ultraviolet and visible light-responsive conducting polymer-based TiO₂ nanocomposites for their potential application in environmental remediation. This review ends with a summary focusing on the challenges and new dimensions in this still emerging area of research.