Visible Light-induced Photocatalysis Research Articles

Decorating hierarchical Bi2MoO6 microspheres with uniformly dispersed ultrafine Ag nanoparticles by an in situ reduction process for enhanced visible light-induced photocatalysis

In this work, we have demonstrated an efficient Sn (II) mediated in situ reduction strategy to assemble silver nanoparticles on Bi2MoO6 microspheres. The Ag loading can be readily controlled by varying the volume of Ag (NH3)2OH aqueous solution. Meanwhile, the ultrafine silver spherical nanoparticles with uniform diameters are free of protection ligands and are well dispersed on the surface of Bi2MoO6 nanosheet without aggregation even at high loading. Photocatalytic test demonstrated that as-adopted in situ reduction strategy was an effective means to enhance the photocatalytic activity of Bi2MoO6 nanosheet-based microspheres under visible light irradiation (λ>420nm). The enhancement performance is believed to be induced by the intimate contact interface, where silver nanoparticles serve as good electron acceptor for facilitating quick photoexcited electron transfer and thus decreasing electron–hole recombination.

ChemInform Abstract: Photocatalysis by Inorganic Solid Materials: Revisiting Its Definition, Concepts, and Experimental Procedures

AbstractReview: 70 refs.

Visible light-induced photocatalysis through surface plasmon excitation of platinum-metallized titania for photocatalytic bleaching of rhodamine B

Nanocomposites consisting of titania nanoparticles and metallic platinum were prepared via a soft chemical reduction method. The detailed structural, compositional, and optical characterization and physicochemical properties of the obtained products were analyzed by X-ray diffraction, nitrogen adsorption, Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and FT-IR spectroscopy techniques. Employing photodegradation of rhodamine B as the model reaction, we found that the as-prepared Pt/TiO2 nanocomposite showed an excellent photocatalytic oxidation activity under visible light irradiation. On the basis of these results, the intrinsic mechanism of visible light-induced photocatalytic oxidation of organic compounds on the platinized titania is proposed and discussed. The superior visible light-driven photocatalytic efficiency of the Pt/TiO2 nanocomposite photocatalyst can be ascribed to the high efficiency of charge-pair separation due to the presence of deposited Pt serving as electron sinks to retard the rapid e−–h+ couple recombination; the good photoabsorption capacity in the visible light region; and the higher concentration of surface hydroxyl groups, which are able to effectively scavenge photogenerated valence band holes. Accumulation of the holes at the catalyst surface increases the probability of the formation of OH· as a reactive species that readily oxidizes the organic dye molecule.

Visible Light Induced Photocatalytic Degradation of Methyl Orange by Polythiophene/TiO2 Composite Particles

The adsorption and photocatalytic degradation of methyl orange (MO) aqueous solution under visible light illumination by polythiophene/titanium dioxide (PTh/TiO2) composite particles were studied. The experimental observations from UV–vis spectrophotometer indicate that MO molecules were degraded in a different degree during the visible light-induced photocatalysis reaction. We propose a new degradation mechanism of MO during the photocatalytic reaction, based on blue shift of UV–vis absorption spectra of MO solution and other researches. The data from total organic carbon analyzer definitely prove that MO can be mineralized to CO2 and H2O, and some intermediate products are generated during the photocatalysis degradation of MO.

Carbon-Deposited TiO2: Synthesis, Characterization, and Visible Photocatalytic Performance

Carbon-deposited TiO2 (TiO2@C) was prepared with a one-pot hydrothermal process by using glucose as a carbon source. The physical properties of TiO2@C were studied by XRD, TG-DTA, HRTEM, and UV−vis diffuse reflectance spectra (DRS), while the chemical states of carbon were discussed via X-ray photoelectron spectroscopy (XPS). A graphite carbon layer was formed out of the TiO2 grain during the hydrothermal process via the dehydration of glucose, which consisted of not only Cn but also C—OH (and C—O—C) and C═O (and COO). TiO2@C has remarkable light absorption in the visible region. It was found that the photocatalytic activity of TiO2@C was greatly enhanced compared to noncarbon-TiO2 under visible irradiation. The photocatalyst with the highest photocatalytic activity for the degradation of Acid Orange 7 (AO7) was G15 TiO2@C, while that for the degradation of 2,4-dichlorophenol (2,4-DCP) was G5 TiO2@C. Two kinds of sensitization processes, carbon sensitization and dye sensitization, are responsible for the visible light-induced photocatalysis of TiO2@C. Carbon sensitization reached its optimal condition in G5, while dye sensitization occurred in its maximum efficiency in G15.

A facile preparation and visible light-induced photocatalysis of indium sulfide superstructure

β-In2S3 superstructure comprised of nanoflakes with the sizes of 200–450 nm has been synthesized by a facile reflux method with the assistance of the sodium dodecylsulfate at low temperature (80 °C). XRD, SEM, TEM, HRTEM, and UV–vis spectra were used to characterize the In2S3 superstructure. Prepared In2S3 superstructures exhibited high photocatalytic activities in the degradation of rhodamine B under visible light irradiation (λ > 420 nm), in which 97.5% RhB was photodegraded after 60 min.

Role of Visible Light-Activated Photocatalyst on the Reduction of Anthrax Spore-Induced Mortality in Mice

BackgroundPhotocatalysis of titanium dioxide (TiO2) substrates is primarily induced by ultraviolet light irradiation. Anion-doped TiO2 substrates were shown to exhibit photocatalytic activities under visible-light illumination, relative environmentally-friendly materials. Their anti-spore activity against Bacillus anthracis, however, remains to be investigated. We evaluated these visible-light activated photocatalysts on the reduction of anthrax spore-induced pathogenesis.Methodology/Principal FindingsStandard plating method was used to determine the inactivation of anthrax spore by visible light-induced photocatalysis. Mouse models were further employed to investigate the suppressive effects of the photocatalysis on anthrax toxin- and spore-mediated mortality. We found that anti-spore activities of visible light illuminated nitrogen- or carbon-doped titania thin films significantly reduced viability of anthrax spores. Even though the spore-killing efficiency is only approximately 25%, our data indicate that spores from photocatalyzed groups but not untreated groups have a less survival rate after macrophage clearance. In addition, the photocatalysis could directly inactivate lethal toxin, the major virulence factor of B. anthracis. In agreement with these results, we found that the photocatalyzed spores have tenfold less potency to induce mortality in mice. These data suggest that the photocatalysis might injury the spores through inactivating spore components.Conclusion/SignificancePhotocatalysis induced injuries of the spores might be more important than direct killing of spores to reduce pathogenicity in the host.

Enhanced Photocatalytic Degradation of RhB Driven by Visible Light-Induced MMCT of Ti(IV)−O−Fe(II) Formed in Fe-Doped SrTiO3

It is important to reveal the origin of the visible light-induced photocatalytic activity of transition metal-doped SrTiO3 in which an isolated energy level is created by the dopant in the forbidden band gap. In this particle, the photocatalytic and photophysical properties of pure SrTiO3 and Fe-doped SrTiO3 were investigated comparatively. The Fe-doped SrTiO3 has been shown to have a much higher photocatalytic activity than pure SrTiO3 for the degradation of RhB under visible light irradiation. It was showed that doping Fe into SrTiO3 exhibited an absorption extending up to the visible region in the optical absorption spectrum and established the TiIV−O−FeII heterobimetallic linkages in the host. Difference diffuse reflectance spectra revealed that the absorption in the visible region is partly attributed to the metal-to-metal charge-transfer (MMCT) excitation of TiIV−O−FeII linkage formed in the Fe-doped SrTiO3. The visible light excitation of TiIV−O−FeII linkage was demonstrated to be the cause of the enhanced degradation of RhB. Furthermore, it was noted that the TiIV−O−FeII linkages only onto and nearest the surface of the Fe-doped SrTiO3 behavior as active sites for the visible light-induced photocatalysis.

Effect of Pt/TiO 2 characteristics on temporal behavior of o-cresol decomposition by visible light-induced photocatalysis

Platinum deposited TiO 2 films were prepared on quartz substrates by dip-coating process for the photodecomposition of o-cresol. The characteristics of Pt/TiO 2 and the temporal behavior of o-cresol decomposition by Pt/TiO 2 photocatalysis under visible light irradiation were investigated. Platinum deposited on TiO 2 photocatalysts was characterized by Brunauer–Emmett–Teller (BET) surface area measurement, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), diffuse reflectance UV–Vis spectra (DRS) and photoluminescence (PL) emission spectra. The results indicated that the deposition of platinum on TiO 2 promoted the optical absorption in the visible region and made it possible to be excited by visible light. The decomposition rate of o-cresol under visible light irradiation from a fluorescent lamp was enhanced to noticeably extents for experiments conducted with Pt/TiO 2 containing platinum up to 0.50 wt% platinum because of the presence of Ti 3+ resulted from the platinum deposited on the TiO 2 surface; and the formation of Schottky Barrier between platinum and TiO 2 preventing the recombination of electric holes and electrons. Specifically, the reaction rate of o-cresol photodegradation at pH 9 using the 0.50 wt% Pt/TiO 2 was 4.8 times than that of using pure TiO 2. The intermediates identified by GC/MS spectroscopy during the photocatalytic oxidation of o-cresol. The proposed kinetic model could be adequately applied to describe the temporal behavior of the o-cresol decomposition with and without the dosage of Pt on TiO 2 in aqueous solution by UV/TiO 2 process.

Investigation of structure and properties of N-doped TiO 2 thin films grown by APCVD

Using TiCl 4, O 2, and NH 3 as gas precursors, N-doped titanium dioxide films with large areas and continuous surfaces were deposited by atmospheric pressure chemical vapor deposition (APCVD). Measurements were performed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet visible (UV–vis) transmission spectra. Using NH 3 as the N-doping source, Ti 4O 7 is induced into the thin films, and anatase–rutile transformation is inhibited. Compared to pure TiO 2, N-doped TiO 2 films deposited with lower NH 3 flows (<90 sccm) give a relatively narrow band gap (from 3.21 to 2.76 eV), and their visible light-induced photocatalysis and hydrophilicity are much enhanced without a decrease in ultraviolet light activity. Preparation of N-doped TiO 2 films by APCVD with low cost and high deposition rate (150 nm/min) is compatible with float glass processing, and has a potential industrial application.