Sequential Growth of Cs_(3)Bi_(2)I_(9)/BiVO_(4)Direct Z-Scheme Heterojunction for Visible-Light-Driven Photocatalytic CO_(2)Reduction

The high exciton binding energy and lack of a positive oxidation band potential restrict the photocatalytic CO_(2)reduction efficiency of lead-free Bi-based halide perovskites Cs_(3)Bi_(2)X_(9)(X=Br,I).In this study,a sequential growth method is presented to prepare a visible-light-driven(λ>420 nm)Z-scheme heterojunction photocatalyst composed of BiVO_(4)nanocrystals decorated on a Cs_(3)Bi_(2)I_(9)nanosheet for photocatalytic CO_(2)reduction coupled with water oxidation.The Cs_(3)Bi_(2)I_(9)/BiVO_(4)Z-scheme heterojunction photocatalyst is stable in the gas-solid photocatalytic CO_(2)reduction system,demonstrating a high visible-light-driven photocatalytic CO_(2)-to-CO production rate of 17.5μmol/(g·h),which is approximately three times that of pristine Cs_(3)Bi_(2)I_(9).The high efficiency of the Cs_(3)Bi_(2)I_(9)/BiVO_(4)heterojunction was attributed to the improved charge separation in Cs_(3)Bi_(2)I_(9).Moreover,the Z-scheme charge-transfer pathway preserves the negative reduction potential of Cs_(3)Bi_(2)I_(9)and the positive oxidation potential of BiVO_()4.This study off ers solid evidence of constructing Z-scheme heterojunctions to improve the photocatalytic performance of lead-free halide perovskites and would inspire more ideas for developing leadfree halide perovskite photocatalysts.

Photocatalytic Dye Methyl Orange Decomposition on Ternary Sulfide (CdIn2S4) under Visible-light

A novel and efficient photocatalyst, CdIn2S4, was simply prepared by a programmed temperature hydrothermal method. The product had a nanometer size （10-15 nm） and strong absorption in the range of 200 to 580 nm, and it exhibited visible-light photocatalytic activity to decompose dye methyl orange in aqueous system.

Preparation and characterization of the TiO_2-V_2O_5 photocatalyst with visible-light activity

Visible-light responsive TiO2-V2O5 catalyst was prepared using a binary sol-gel and in-situ intercalation method. The TiO2 sol and V2O5 sol were mixed to disperse the V2O5 species in the TiO2 phase at molecular level. The binary sol was then intercalated into interspaces of polyaniline （PANI） by means of in-situ polymerization of aniline. Conglomeration of the TiO2-V2O5 dusters during the calcination process was avoided because of the wrap of polyaniline. The surface mor- phology, the crystal phases, the structure, and the absorption spectra of （PANI）,/TiO2-V2O5 and the composite catalyst were studied using SEM, XRD, FT-IR, and UV-Vis. The photoactivity of the prepared catalyst under UV and visible light irradiation were evaluated by decolorization of methylene blue （MB） solution. The results showed that the composite catalyst displayed a homogeneous anatase phase, and the vanadium pentoxide species was highly dispersed in the TiO2 phase. The composite catalyst responded to visible light because of the narrowed band gap. In this study, the catalyst with the sol volume ratio of TiO2： V2O5 = 10：1 presented the best photocatalytic activity.

ZnO-chitosan/Rectorite Nanocomposite Exhibiting High Photocatalytic Activities under Visible-light Irradiation

Chitosan(CS),hydrated zinc acetate,and rectorite(REC) were used as raw materials to prepare CS-embedded zinc oxide(ZnO) nanoparticle by a chemical precipitation process.Hydrogen-bonded REC-loaded ZnO-CS nanoparticle was to form ZnO-CS/REC nanocomposite photocatalyst,its morphology and structure were analyzed by means of FTIR,XRD,TGA,SEM,and TEM.The effects of the catalyst dosage,methyl orange(MO) initial concentration and solution pH on photocatalytic performance were also discussed.The experimental results show that the ZnO-CS/REC nanocomposite has a particle size of 100 nm with good dispersion and uniformity.Under irradiation of visible light,0.6 g/L photocatalyst was used to degrade MO in solution for 90 min at pH 6,then the MO solution(10 mg/L) was decolored by more than 99%,indicating that the ZnO-CS/REC nanocomposite exhibited highly photocatalytic degradation activity.Therefore,the photodegradation kinetic mechanism of MO in aqueous solution is presumed.

In-situ hydrothermal synthesized γ-Al_2O_3/O-g-C_3N_4 heterojunctions with enhanced visible-light photocatalytic activity in water splitting for hydrogen

In this work, γ-Al2O3and hydrogen peroxide treated g-C3N4(O-g-C3N4) were combined through a novel in-situ hydrothermal method to form heterojunction structured photocatalysts. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL). FT-IR results indicate that oxygen functional groups can be grafted on the surface of O-g-C3N4by hydrogen peroxide treatment. The visible light photocatalytic hydrogen evolution rate was investigated in 10 vol% TEOA aqueous solution. The optimal Al2O3mass content is set to be 20 wt% and the corresponding hydrogen evolution rate is 1288?μmol/h/g which is approximately 6, 3 folds that of pristine g-C3N4and O-g-C3N4respectively and 1.6 folds that of mechanical mixed composite with the same Al2O3mass content. The photocurrent density–time curves were carried out under visible light illumination for four on–off cycles. The electrochemical impedance spectroscopy (EIS) measurements verified the enhanced separation efficiency of electron–hole pairs. This work raised a new method to form the heterojunction structured photocatalysts and achieved a remarkable improvement of the photocatalytic activity in water splitting for hydrogen under visible light irradiation. ? 2016

LED Modulation Characteristics in a Visible-Light Communication System

This paper conducts a research on modulation characteristics of blue light-emitting diodes (LEDs) used in a visible-light communication (VLC) system. Through analysis of the modulation characteristics of LEDs with different emitting sizes, we find that there is a similar linear relationship between LED’s 3dB bandwidth and the operation current density. This experiment also shows that high series resistance is one major issue that limits our LED's modulation speed. To further improve the LED bandwidth, the resistance can be reduced by optimizing device layout as well as reducing material bulk resistance. Clearly, this study provides an approach to increase the modulation bandwidth of GaN-based LEDs for VLC systems.

Performance improvement of InGaN/GaN multiple quantum well visible-light photodiodes by optimizing TEGa flow

The performance of an InGaN/GaN multiple quantum well（MQW） based visible-light Schottky photodiode（PD）is improved by optimizing the source flow of TEGa during In Ga N QW growth. The samples with five-pair InGaN/GaN MQWs are grown on sapphire substrates by metal organic chemical vapor deposition. From the fabricated Schottky-barrier PDs, it is found that the smaller the TEGa flow, the lower the reverse-bias leakage is. The photocurrent can also be enhanced by depositing the In GaN QWs with using lower TEGa flow. A high responsivity of 1.94 A/W is obtained at 470 nm and -3-V bias in the PD grown with optimized TEGa flow. Analysis results show that the lower TEGa flow used for depositing In Ga N may lead to superior crystalline quality with improved InGaN/GaN interface, and less structural defects related non-radiative recombination centers formed in the MQWs.

Visible-light all-fiber vortex lasers based on mode selective couplers

We demonstrate visible-light all-fiber vortex lasers by incorporating the home-made mode selective couplers (MSCs). The MSC at green or red wavebands is fabricated by specially designing and fusing a single-mode fiber (SMF) and a few-mode fiber (FMF). The MSCs inserted into visible fiber cavities act as power splitters and mode converters from the LP01 to LP11 mode at green and red wavelengths, respectively. The red-light all-fiber vortex laser is formed by a 10-cm Pr3+/Yb3+:ZBLAN fiber, a fiber Bragg grating, a fiber end-facet mirror and the MSC at 635 nm, which generates vortex beams with OAM±1 at 634.4 nm and an output power of 13 mW. The green-light all-fiber vortex laser consists of a 12-cm Ho3+:ZBLAN fiber, two fiber pigtail mirrors, and the MSC at 550 nm, which generates vortex beams with OAM±1 at 548.9 nm and an output power of 3 mW.

Hydrothermal Synthesis of CdIn_2S_4 and Photocatalytic Degradation of Methyl Orange under Visible-light Irradiation

CdIn2S4 microspheres were synthesized by a facile hydrothermal method with the temperature ranging from 120 to 200 ℃. X-ray diffraction, UV-vis diffuse reflectance spectroscopy, nitrogen sorption analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy were used to characterize the products. It was found that the crystallographic structure and optical property of the products synthesized at different temperature were almost the same. The SBEX of CdIn2S4 products decreased when the synthesized temperature increased, and the largest SBET was 33.16 m2 g-1 （120 ℃ sample）. The degradation of methyl orange （MO） under the visible-light irradiation had been used as a probe reaction to investigate the photocatalytic activity of the as-prepared CdIn2S4, which showed that the CdIn2S4 sample synthesized at 120 ℃ presented the best photocatalytic activity for MO degradation.

A Novel Visible-light-responsive Photocatalyst Bi1.5Cr0.5WO6 with Suitable Bandgap Structure and Its Application in Water Decontamination

Integrating the advantages of Bi and Cr elements in the bandgap engineering of metal oxides, a visible-light-responsive photocatalyst Bi1.5Cr0.5WO6 is successfully constructed and initially applied in water decontamination. The combination of UV-vis diffuses reflectance and the Mott-Schottky curve from electrochemical testing can be used to determine the conduction band and valence band of Bi1.5Cr0.5WO6 to be about –1.26 and 1.42 V, respectively. The location of energy band structure indicates that the superoxide free radical can be produced in Bi1.5Cr0.5WO6 photocatalytic system without hydroxyl group. This speculation is also confirmed by ESR experiment and active radical species scavenging experiments. In addition, the best photocatalytic performance of Bi1.5Cr0.5WO6 obtained under 180 ℃ is attributed to the smallest impedance and the strongest electronic migration capability.

Rare Earth Ion Yb^3+ Doping of Bi2WO6 with Excellent Visible-light Photocatalytic Activity

The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra were used to characterize the Yb^3+ doped Bi2WO6 photocatalysts.The morphology,specific surface area,and pore volume distribution were greatly affected after Yb3+ ions doping.Photocatalytic performance of Bi2WO6 was effectively enhanced after Yb3+ ions doping,6% Yb^3+ doped Bi2WO6 had the best photocatalytic performance,and 96.2% Rhodamine B was degradated after irradiated 30 min,which was 1.29 times that of the pristine one.The enhanced photocatalytic performance was due to the increased specific surface area,decreased energy band gap and inhibition of photoelectron-hole recombination after Yb3+ ions doping.

Preparation of Novel Mesoporous Photocatalyst Bi₄O₅Br₂/SBA-15 with Enhanced Visible-Light Catalytic Activity

Photocatalysis is one of the most promising methods owing to its great potential to relieve environmental issue. To construct efficient photocatalyst with low energy consumption, mild catalytic conditions, and stable chemical properties are highly desired. In this work, a novel, highly active and environmental friendly mesoporous photocatalyst Bi4O5Br2/SBA-15 was synthesized by hydrothermal method, and its characteristics and visible-light catalytic activity were investigated. The synthesized photocatalyst consisted of Langmuir type IV hysteresis loops, which was confirmed to be a composite material with mesoporous structure. It exhibited a high visible-light absorption intensity and a low recombination rate of photo-generated electrons and holes. When the mass ratio of Bi/SiO2 was 30/100 during the synthesis, the obtained photocatalyst (Bi30/SBA-15) reflected the fastest Rhodamine B (RhB) removal rate and achieved 100% decolorization of RhB by both adsorption and degradation process. This high decolorization efficiency can also be maintained and realized by recycling the used composite in practice. The enhanced visible-light photocatalytic activity of novel Bi4O5Br2/SBA-15 photocatalyst can be ascribed to the existing active sites both inside and outside SBA-15 which enhanced the separation of photo-generated electrons and holes.

Electronic Structure and Visible-Light Absorption of Transition Metals(TM=Cr,Mn, Fe, Co) and Zn-Codoped SrTiO_3: a First-Principles Study

First-principles calculations are performed on the influence of transition metal（TM=Cr, Mn, Fe, Co） as codopants on the electronic structure and visible-light absorption of Zn-doped Sr TiO_3. The calculated results show that（Zn,Mn）-codoped Sr TiO_3 requires the smallest formation energy in four codoping systems. The structures of the codoped systems display obvious lattice distortion, inducing a phase transition from cubic to rhombohedral after codoping. Some impurity Cr, Mn and Co 3d states appear below the bottom of conduction band and some Fe 3d states are located above the top of valence band, which leads to a significant narrowing of band gap after transition metal codoping. The enhancement of visible-light absorption are observed in transition metals（TM=Cr, Mn, Fe, Co） and Zn codoped Sr TiO_3 systems. The prediction calculations suggested that the（Zn,Mn）-and（Zn,Co）-codoped SrTiO_3 could be the desirable visible-light photocatalysts.

Enhanced visible-light photocatalytic hydrogen evolution using two-dimensional carbon nitride sheets with the removal of amine groups

Two-dimensional(2D)carbon nitride sheets(CNs)with atomically thin structures are regarded as one of the most promising materials for solar energy conversion.However,due to their substantially enlarged bandgap caused by the strong quantum size effect and their incomplete polymerisation with a large number of non-condensed surface amino groups,the practical applicability of CNs in photocatalysis is limited.In this study,CNs with broad visible-light absorption were synthesised using a 5-min fast thermal annealing.The removal of uncondensed amine groups reduces the bandgap of CNs from 3.06 eV to 2.60 eV,increasing their absorption of visible light.Interestingly,the CNs were distorted after annealing,which can differentiate the spatial positions of electrons and holes,enhancing the visible-light absorption efficiency.As a result,when exposed to visible light,the photocatalytic hydrogen production activity of atomically thin 2D CNs rose by 8.38 times.This research presents a dependable and speedy method for creating highly effective visible-light photocatalysts with narrowed bandgaps and improved visible-light absorption.

Additive-free synthesis of S-substituted isothioureas via visible-light-induced four-component reaction ofα-diazoesters,aryl isothiocyanates,amines and cyclic ethers

An additive-free and environmentally friendly strategy has been realized for the construction of S-substituted isothioureas through visible-light-induced multicomponent reaction starting fromα-diazoesters,aryl isothiocyanates,amines and cyclic ethers.This methodology features simple operation,mild reaction conditions,favorable functional group tolerance,easily available starting materials and high efficiency.

Continuous microflow visible-light photocatalytic N-formylation of piperidine and its kinetic study

N-formylation of amines,a class of synthetically important reactions,is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency.Here,an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine,which achieved a reaction yield of 82.97%and a selectivity of>99%at 12 min using cheap organic dye photocatalyst under mild reaction conditions.The influence of essential parameters,including light intensity,temperature and equivalents of the gas,additive and photocatalyst,on the reaction yield was systematically studied.Furthermore,kinetic investigations were conducted,exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity,temperature and photocatalyst equivalent.The microflow photocatalytic approach established in this work,which realized a markedly higher space-time yield than the conventional batch method(37.9 vs.0.212 mmol h-1 L-1),paves the way for the continuous,green and efficient synthesis of N-formamides.

Z型可见光催化剂Au NPs/g-C3N4/BiOBr的构建及其光催化性能（英文）

通过水热和原位还原法制备了一种新型Z型异质结三元复合材料Au NPs/g-C3N4/BiOBr,并通过X射线衍射、X射线光电子能谱、透射电子显微镜、紫外-可见漫反射光谱和光致发光发射光谱等技术对材料的形貌、结构进行了表征。通过在可见光下降解苯酚来评价光催化剂的活性。研究发现,Au NPs/g-C3N4/BiOBr显示出增强的光催化活性,对苯酚的降解能力是g-C3N4的3倍,是BiOBr的2.5倍。这可归因于三元复合材料的窄带隙(2.10eV)、Z型机理对光生电子-空穴对的有效分离和Au纳米颗粒的表面等离子体共振效应(SPR)。

Photocatalytic dicarboxylation of strained C-C bonds with CO_(2) via consecutive visible-light-induced electron transfer

Dicarboxylic acids have a wide range of applications in the polymer industry to construct valuable materials.Photocatalysis has recently emerged as an efficient and sustainable strategy to generate dicarboxylic acids.However,photocatalytic dicarboxylation with CO_(2) is mainly limited to unsaturated bonds,and the dicarboxylation of C-C single bonds still remains a challenge.Herein,we report a photocatalytic dicarboxylation of C-C single bonds in strained rings with CO_(2) units via consecutive photo-induced electron transfer(ConPET).It is also the first photocatalytic reductive ring-opening reaction of cyclobutanes.Notably,this transition-metal-free protocol exhibits good functional group tolerance,broad substrate scope,facile scalability,and easy product derivatizations.Moreover,diacids can easily be derivatized to mainchain liquid crystalline polyesters.

Bi_2WO_6微球的制备及可见光催化性能研究

以葡萄糖为模板剂,采用水热法在160℃下制备了Bi2WO6微球.利用X射线衍射(XRD)、扫描电镜(SEM)、紫外可见光谱仪(UV-Vis)、分别对Bi2WO6微球的结构、形貌和性能进行了表征,并特别考察了Bi2WO6微球在可见光的照射下对罗丹明B的光催化降解性能.结果表明,加入葡萄糖后,Bi2WO6的形貌从球形变为扁柿状形貌,禁带宽度减小,可见光催化性能得到大幅提高.

Synthesis and Characterization of Co-Doped Brookite Titania Photocatalysts with High Photocatalytic Activity

Transition metal-doping could effectively extend the light response range of TiO _2 photocatalysts from the ultraviolet(UV)to the visible region.Co-doped brookite titanium dioxide(Co–TiO_2)photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant.The prepared Co–TiO_2 photocatalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and UV–Vis diffuse reflectance spectroscopy(UV–Vis DRS).The photocatalytic activities of Co–TiO _2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol(IPA),a typical volatile organic compound(VOC),under visible light.The influences ofdifferent Co doping rates,initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied.At the same time,the enhancement mechanism ofcobalt ions as a trap for photogenerated holes was discussed.Thus,we found the optimum doping rate,initial concentration of IPA gas and amount of photocatalyst to add.The results show that the mesoporous Co–TiO _2 photocatalysts possess smaller size particles,larger specific surface area,lower forbidden bandgap energy(Eg)and better photocatalytic activity than pure brookite TiO _2.When the doping of Co was 7% by mass,the initial concentration ofIPA gas was 1.0×10^(-6 )mol/L and the addition of Co–TiO_2 photocatalysts was 50 mg,the best photocatalytic activity was achieved.Furthermore,the degradation rate ofIPA was up to 91%,which shows great potential for waste water treatment.