S-Scheme BiOCl/MoSe2 Heterostructure with Enhanced Photocatalytic Activity for Dyes and Antibiotics Degradation under Sunlight Irradiation.

Semiconductor photocatalysis is considered to be a promising technique to completely eliminate the organic pollutants in wastewater. Recently, S-scheme heterojunction photocatalysts have received much attention due to their high solar efficiency, superior transfer efficiency of charge carriers, and strong redox ability. Herein, we fabricated an S-scheme heterostructure BiOCl/MoSe2 by loading MoSe2 nanosheets on the surface of BiOCl microcrystals, using a solvothermal method. The microstructures, light absorption, and photoelectrochemical performances of the samples were characterized by the means of SEM, TEM, XRD, transient photocurrents, electrochemical impedance, and photoluminescence (PL) spectra. The photocatalytic activities of BiOCl, MoSe2, and the BiOCl/MoSe2 samples with different MoSe2 contents were evaluated by the degradation of methyl orange (MO) and antibiotic sulfadiazine (SD) under simulated sunlight irradiation. It was found that BiOCl/MoSe2 displayed an evidently enhanced photocatalytic activity compared to single BiOCl and MoSe2, and 30 wt.% was an optimal loading amount for obtaining the highest photocatalytic activity. On the basis of radical trapping experiments and energy level analyses, it was deduced that BiOCl/MoSe2 follows an S-scheme charge transfer pathway and •O2-, •OH, and h+ all take part in the degradation of organic pollutants.

Rhodol-based far-red fluorescent probe for the detection of cysteine and homocysteine over glutathione.

The simultaneous discrimination of cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) is of great importance due to their roles in biology and close link to many diseases, especially via the development of a far-red fluorescent probe that could be used for rapid, selective, and sensitive detection of all three. Herein, we report the characterization of a far-red fluorescent probe with turn-on fluorescence properties and visible color changes that could be used for the detection of cysteine and homocysteine over glutathione. In this study we found that the sensor could discriminate cysteine and homocysteine over glutathione within 20 min. Function of this probe was based on the conjugate addition-cyclization reaction and showed a low detection limit to cysteine and homocysteine. Upon the addition of cysteine and homocysteine, the absorption band at 592 nm rose gradually and fluorescence was detected at 645 nm. The color changed from colorless to blue and fluorescence changed from absent to strong red fluorescence, which could be differentiated by the naked eye. All these unique features make this probe particularly potentially favorable for use in cysteine/homocysteine sensing and bioimaging applications. Copyright © 2016 John Wiley & Sons, Ltd.

Surface-Enhanced Raman Spectroscopy Assisted by Radical Capturer for Tracking of Plasmon-Driven Redox Reaction.

The deep understanding about the photocatalytic reaction induced by the surface plasmon resonance (SPR) effect is desirable but remains a considerable challenge due to the ultrafast relaxation of hole-electron exciton from SPR process and a lack of an efficient monitoring system. Here, using the p-aminothiophenol (PATP) oxidation SPR-catalyzed by Ag nanoparticle as a model reaction, a radical-capturer-assisted surface-enhanced Raman spectroscopy (SERS) has been used as an in-situ tracking technique to explore the primary active species determining the reaction path. Hole is revealed to be directly responsible for the oxidation of PATP to p, p'-dimercaptoazobenzene (4, 4'-DMAB) and O2 functions as an electron capturer to form isolated hole. The oxidation degree of PATP can be further enhanced through a joint utilization of electron capturers of AgNO3 and atmospheric O2, producing p-nitrothiophenol (PNTP) within 10 s due to the improved hole-electron separation efficiency.

Double-diffusion-based synthesis of BiVO4 mesoporous single crystals with enhanced photocatalytic activity for oxygen evolution.

BiVO4 mesoporous single crystals (MSCs) were successfully prepared, for the first time, by a one-step hydrothermal method using the acidified BiVO4 precursor solution pre-impregnated silica as the template. It was revealed that the BiVO4 MSCs were formed by a double-diffusion mechanism. The O2 evolution rate over BiVO4 MSCs was improved nearly 10 times than that over BiVO4 bulk single crystals.

Core-Shell Structural CdS@SnO2 Nanorods with Excellent Visible-Light Photocatalytic Activity for the Selective Oxidation of Benzyl Alcohol to Benzaldehyde.

Core-shell structural CdS@SnO2 nanorods (NRs) were fabricated by synthesizing SnO2 nanoparticles with a solvent-assisted interfacial reaction and further anchoring them on the surface of CdS NRs under ultrasonic stirring. The morphology, composition, and microstructures of the obtained samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption. It was found that SnO2 nanoparticles can be tightly anchored on the surface of CdS NRs, and the thickness of SnO2 shells can be conveniently adjusted by simply changing the addition amount of SnO2 quantum dots. UV-vis diffuse reflectance spectrum indicated that SnO2 shell layer also can enhance the visible light absorption of CdS NRs to a certain extent. The results of transient photocurrents and photoluminescence spectra revealed that the core-shell structure can effectively promote the separation rate of electron-hole pairs and prolong the lifetime of electrons. Compared with the single CdS NRs, the core-shell structural CdS@SnO2 exhibited a remarkably enhanced photocatalytic activity for selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD) under visible light irradiation, attributed to the more efficient separation of electrons and holes, improved surface area, and enhanced visible light absorption of core-shell structure. The radical scavenging experiments proved that in acetonitrile solution, ·O2- and holes are the main reactive species responsible for BA to BAD transformation, and the lack of ·OH radicals is favorable to obtaining high reaction selectivity.

A Brown Mesoporous TiO2-x /MCF Composite with an Extremely High Quantum Yield of Solar Energy Photocatalysis for H2 Evolution.

A brown mesoporous TiO2-x /MCF composite with a high fluorine dopant concentration (8.01 at%) is synthesized by a vacuum activation method. It exhibits an excellent solar absorption and a record-breaking quantum yield (Φ = 46%) and a high photon-hydrogen energy conversion efficiency (η = 34%,) for solar photocatalytic H2 production, which are all higher than that of the black hydrogen-doped TiO2 (Φ = 35%, η = 24%). The MCFs serve to improve the adsorption of F atoms onto the TiO2 /MCF composite surface, which after the formation of oxygen vacancies by vacuum activation, facilitate the abundant substitution of these vacancies with F atoms. The decrease of recombination sites induced by high-concentration F doping and the synergistic effect between lattice Ti(3+)-F and surface Ti(3+)-F are responsible for the enhanced lifetime of electrons, the observed excellent absorption of solar light, and the photocatalytic production of H2 for these catalysts. The as-prepared F-doped composite is an ideal solar light-driven photocatalyst with great potential for applications ranging from the remediation of environmental pollution to the harnessing of solar energy for H2 production.

Highly-dispersed boron-doped graphene nanoribbons with enhanced conductibility and photocatalysis.

Highly-dispersed boron-doped graphene nanoribbons (B-GNRs), prepared by a simple vacuum activation method, exhibit p-type semiconductor properties and provide many more zigzag- and armchair-edges to facilitate control of the bandgap. B-GNRs are used for the photodegradation of Rhodamine B in order to demonstrate their excellent conductivity and photocatalytic activity.

Silver halide/silver iodide@silver composite with excellent visible light photocatalytic activity for methyl orange degradation.

AgBr/AgI@Ag composite photocatalyst was prepared by a handy multistep route, including controllable double-jet precipitation to synthesize cubic AgBr microcrystals, ion exchange to form AgI on AgBr surface, and visible light reduction to generate Ag nanoparticles. UV-Vis diffuse reflectance and electrochemical impedance spectra demonstrated that AgBr/AgI composite structure not only favors forming more silver nanoparticles to harvest visible light but also facilitates the transfer of charge carriers when compared with pure AgBr. Beneficial from the synergistic effect of highly effective visible light harvest and electron-hole separation, AgBr/AgI@Ag shows higher photocatalytic activity for the degradation of methyl orange (MO) than AgBr, AgBr@Ag, and AgBr/AgBr.

CeO2 mediated photocatalytic degradation studies of C.I. acid orange 7.

CeO2 nanoparticles were prepared by a simple precipitation method, followed by calcination treatment. By selecting photocatalytic degradation of acid orange 7 (AO7) as a probe reaction, the influences of calcination temperature of catalyst, the concentration of AO7, initial pH value of AO7 solution and catalyst dosage on the photocatalytic activity of CeO2 were studied. It was found that CeO2 calcined at 550 degrees C shows the highest photocatalytic activity under visible light irradiation. It was revealed that under visible light irradiation the degradation of AO7 over CeO2 nanoparticles follows a dye self-sensitization mechanism. The degradation rate of AO7 increases with decrease in the initial pH value of the reaction solution, and degradation efficiency decreases with increase in the initial dye concentration. The optimal dosage of CeO2 in solution for AO7 degradation is 1 g/L.

Microemulsion-mediated solvothermal synthesis and photocatalytic properties of crystalline titania with controllable phases of anatase and rutile.

Titanium oxide with different ratios of anatase to rutile has been prepared by the microemulsion-mediated solvothermal method. The resulting samples were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-vis diffuse reflectance spectra, transmission electron microscopy and Brunauer-Emmett-Teller analysis. The contents of anatase and rutile in the TiO(2) particles have been successfully controlled by simply adjusting the amount of urea in the aqueous phase of the microemulsion. Both the degradation of Rhodamine B in aqueous solutions and mineralization of TOC revealed that the catalyst containing 47.6% anatase have presented the highest photocatalytic activity. A proposed mechanism is discussed to interpret the evolution of the phases based on the effect of different amount of urea.

An economic method to prepare vacuum activated photocatalysts with high photo-activities and photosensitivities.

This study reports a simple and economic method to modify Degussa P25 with a vacuum activated procedure, resulting in its high photo-activity and photosensitivity, which suggests this method to be a starting point for the extension of its application to photocatalysis.

Synthesis and characterization of thermally stable Sm,N co-doped TiO2 with highly visible light activity.

Samarium and nitrogen co-doped titania (Sm/N-TiO(2)) was successfully prepared via coprecipitation method. The resulting materials were characterized by X-ray diffraction (XRD), N(2) physical adsorption, UV-vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared (FTIR) spectra. Experimental results indicated that samarium doping inhibited the growth of crystalline size and the transformation from anatase to rutile phase. The photocatalytic activities of the samples were evaluated for degradation of salicylic acid under visible light irradiation. It was found that the Sm/N-TiO(2) samples presented much higher photocatalytic activity than N-TiO(2) and pure TiO(2) under visible light irradiation. This could be attributed to the appropriate crystallite size, more efficient separation of electrons and holes on Sm/N-TiO(2). In our experiments, the optimal dopant amount of samarium was 1.5% for the maximum photocatalytic degradation and the sample calcined at 400 degrees C showed the best reactivity.

Thermally stable SiO2-doped mesoporous anatase TiO2 with large surface area and excellent photocatalytic activity.

A thermally stable SiO(2)-doped mesoporous TiO(2) with high crystallinity was prepared by a templating method. The content of SiO(2) dopant was varied from 3% to 20%. The gels were characterized by TG-DTA analysis. And the resultant catalysts were investigated by various physicochemical techniques, such as WAXRD, Raman spectroscopy, N(2) adsorption-desorption, TEM, FT-IR, and XPS. The WAXRD, TEM, and Raman measurements suggest that the SiO(2) dopant can enhance the thermal stability of the anatase phase remarkably. Rutile phase did not present at all even at 1000 degrees C when the SiO(2) content was up to 15%. N(2) adsorption-desorption results show that the SiO(2)-doped samples have uniform pore diameters and large specific surface area, which is beneficial for photocatalytic reaction. The photocatalytic activities of the samples were evaluated by degradation of Rhodamin-6G solution under UV irradiation. The results show that the SiO(2)-doped mesoporous TiO(2) have better activity than commercial P25. Especially, the 15% SiO(2)-doped mesoporous TiO(2) exhibited much higher photocatalytic activity than P25 in a large range of calcination temperatures, even at 900 degrees C. The excellent photocatalytic activity of the samples can be attributed to the high anatase crystallinity, large specific surface area, preserved surface hydroxyl groups and mesoporous channels.

Comparative studies of operational parameters of degradation of azo dyes in visible light by highly efficient WOx/TiO2 photocatalyst.

The multidimensional aspects of the photocatalytic activity were investigated in a systematic way by employing the dyes Acid Orange 7 (AO7) and Methyl Orange (MO) as substrates in terms of their degradation or conversion rates. 4.0% WO(x)/TiO(2) nanocomposite demonstrated the best reactivity under visible light, allowing more efficient usage of solar light. The reduced form of W decreased the band gap and inhibited electron hole recombination efficiently. This composite was characterized by X-ray diffraction spectroscopy (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). A series of experiments were conducted to investigate the operational parameters under visible light irradiation such as optimization of nanocomposites wt%, change of pH, reuse of catalyst and initial dye concentration. The kinetics of the dyes degradation was found to follow the Langmuir-Hinshelwood model. Decomposition or mineralization was investigated with the changes of absorption spectra, pH, degradation efficiency and TOC removal in visible irradiation systems. FT-IR spectroscopy of these adsorbed dyes on WO(x)/TiO(2) powder provided an insight to the mode of its adsorption on WO(x)/TiO(2). It was found that the dye adsorbed on WO(x)/TiO(2) underwent a series of oxidation steps which lead to decolorization and formation of a number of intermediates mainly aromatic and aliphatic acids. These intermediates were quantified by GC/GC-MS.

Preparation of Fe3+-doped TiO2 catalysts by controlled hydrolysis of titanium alkoxide and study on their photocatalytic activity for methyl orange degradation.

Fe3+-doped TiO2 (Fe-TiO2) porous microspheres were prepared by controlled hydrolysis of Ti(OC4H9)4 with water generated "in situ" via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption-desorption methods. All of the undoped TiO2 and Fe-TiO2 samples exclusively consist of primary anatase crystallites, which further form porous microspheres with diameters ranging from 150 to 500 nm. The photocatalytic activity of Fe-TiO2 catalysts was evaluated from the photodegradation of methyl orange (MO) aqueous solution both under UV and visible light irradiation. Fe3+ doping effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.1 and 0.2%, respectively. The photocatalytic mechanisms of Fe-TiO2 catalysts were tentatively discussed.

Preparation of Ce-TiO2 catalysts by controlled hydrolysis of titanium alkoxide based on esterification reaction and study on its photocatalytic activity.

The Ce-TiO2 catalysts were prepared by controlled hydrolysis of Ti(OC(4)H(9))(4) with water generated "in situ" via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), atomic absorption flame emission spectroscopy (AAS), and nitrogen adsorption-desorption methods. Both of undoped TiO2 and Ce-TiO2 samples exclusively consist of primary anatase crystallites, which further form spherical aggregates with diameters ranging from 100 to 500 nm. The photocatalytic activity of Ce-TiO2 was investigated for the photocatalytic degradation of Rhodamine B (RB) aqueous solution both under UV and visible light irradiation. Doping of Ce(4+) effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.2 and 0.4%, respectively. The photocatalytic mechanisms of Ce-TiO2 catalysts were tentatively discussed.

Influences of acids and salts on the crystalline phase and morphology of TiO2 prepared under ultrasound irradiation.

Nanocrystalline TiO2 powders were rapidly prepared by hydrolysis of Ti(OC4H9)4 under ultrasound irradiation. The influences of acids (HCl, HNO3, and H2SO4) and their corresponding salts (NaCl, KNO3, and Na2SO4) on the crystalline phase and morphology of products were investigated, respectively. Compared with NaCl and KNO3 that show no evident influence on the crystalline phase, HCl and HNO3 have a decisive influence on the crystalline phase of the products. However, both H2SO4 and Na2SO4 are favorable for the formation of anatase. By adjusting the concentration of SO2-(4) in the reaction medium, the contents of anatase and rutile phases in the TiO2 powders can be successfully controlled. The morphology of TiO2 crystallites are shown to be strongly related to the type of acid used in the reaction medium.