The Visible‐Light Photocatalytic Activity and Antibacterial Performance of Ag/AgBr/TiO2 Immobilized on Activated Carbon

Visible‐light‐driven Ag/AgBr/TiO₂/activated carbon (AC) composite was prepared by solgel method coupled with photoreduction method. For comparison, TiO₂, TiO₂/AC, and Ag/AgBr/TiO₂ were also synthesized. Their characteristics were analyzed by XRD, SEM‐EDS, TG‐DSC and UV–vis techniques. Photocatalytic activity and antibacterial performance under visible‐light irradiation were investigated by ICP‐AES, ATR‐FT‐IR and spectrophotometry methods using methylene blue and Escherichia coli as target systems, respectively. The results showed that Ag/AgBr was successfully deposited on anatase TiO₂/AC surface, and exhibited a distinct light absorption in the visible region. Ag/AgBr/TiO₂/AC displayed excellent antibacterial performance both in dark and under visible‐light illumination. The growth of E. coli cell was inhibited in the presence of Ag/AgBr/TiO₂/AC in dark. Moreover, upon visible‐light illumination, a significant damage of cell membrane was noticed. Ag/AgBr/TiO₂/AC was also shown higher photocatalytic efficiency for methylene blue degradation than those of TiO₂, TiO₂/AC, and Ag/AgBr/TiO₂. This is attributed to the synergetic effect between AC and Ag/AgBr/TiO₂, of which AC acts as the role of increasing reaction areas, continuous enriching, and transferring the adsorbed MB molecules to the surface of supported photocatalysts, and the Ag/AgBr/TiO₂ acts as a highly active photocatalyst for degrading MB molecules under visible‐light irradiation.     

Correlation of the Catalytic Activity for Oxidation Taking Place on Various TiO2 Surfaces with Surface OH Groups and Surface Oxygen Vacancies

Three catalytic oxidation reactions have been studied: The ultraviolet (UV) light induced photocatalytic decomposition of the synthetic dye sulforhodamine B (SRB) in the presence of TiO₂ nanostructures in water, together with two reactions employing Au/TiO₂ nanostructure catalysts, namely, CO oxidation in air and the decomposition of formaldehyde under visible light irradiation. Four kinds of TiO₂ nanotubes and nanorods with different phases and compositions were prepared for this study, and gold nanoparticle (Au‐NP) catalysts were supported on some of these TiO₂ nanostructures (to form Au/TiO₂ catalysts). FTIR emission spectroscopy (IES) measurements provided evidence that the order of the surface OH regeneration ability of the four types of TiO₂ nanostructures studied gave the same trend as the catalytic activities of the TiO₂ nanostructures or their respective Au/TiO₂ catalysts for the three oxidation reactions. Both IES and X‐ray photoelectron spectroscopy (XPS) proved that anatase TiO₂ had the strongest OH regeneration ability among the four types of TiO₂ phases or compositions. Based on these results, a model for the surface OH group generation, absorption, and activation of molecular oxygen has been proposed: The oxygen vacancies at the bridging O^2? sites on TiO₂ surfaces dissociatively absorb water molecules to form OH groups that facilitate adsorption and activation of O₂ molecules in nearby oxygen vacancies by lowering the absorption energy of molecular O₂. A new mechanism for the photocatalytic formaldehyde decomposition with the Au/TiO₂ catalysts is also proposed, based on the photocatalytic activity of the Au‐NPs under visible light. The Au‐NPs absorb the light owing to the surface plasmon resonance effect and mediate the electron transfers that the reaction needs.     

Photocatalytic Oxidation Based on Modified Titanium Dioxide with Reduced Graphene Oxide and CdSe/CdS as Nanohybrid Materials

Photocatalytic activity of TiO₂ nanoparticles in the visible light region was enhanced. TiO₂–CdSe and TiO₂–CdSe/CdS nanohybrids were supported on the reduced graphene oxide. These nanohybrid materials were applied as photocatalyst toward oxidation of aromatic alcohols under a mild condition and the molecular oxygen as oxidant. A plausible mechanism for the photocatalytic oxidation was also proposed. Desired nanohybrids were obtained via in situ fixation of CdSe/CdS on the surface of nanosheets of reduced graphene oxide (rGO). Finally, it was modified by TiO₂ sol nanoparticles through a hydrothermal method. The obtained nanomaterials, were characterized by SEM, TEM imaging, XRD, EDAX, DRS and XPS analyses. The size of nanohybrids materials were distributed mostly in a narrow range of 50–65 and 60–75 nm for TiO₂–rGO–CdSe and TiO₂–rGO–CdSe/CdS, respectively. These photocatalysts showed high catalytic activity under visible light irradiation in a short reaction time and even higher selectivity rather than UV irradiation. The yield of catalytic oxidation increased at least 25–30% for TiO₂–CdSe/CdS on rGO, which could be related to its higher light sensitivity and lower energy band gap. The photocatalysts were recycled and reused 8 times without significant loss of their activities due to their stability under visible light.     

Au/TiO<Subscript>2</Subscript>/Graphene Composite with Enhanced Photocatalytic Activity Under Both UV and Visible Light Irradiation

Au/TiO₂/graphene composite was synthesized by the combination of electrostatic attraction and photo-reduction method. In the composite, graphene sheets act as an adsorption site for dye molecules to provide a high concentration of dye near to the TiO₂ and Au nanoparticles (NPs), and work as an excellent electron transporter to separate photoinduced e ^?/h ⁺ pairs. Under UV irradiation, photogenerated electrons of TiO₂ are transferred effectively to Au NPs and graphene sheets, respectively, retarding the recombination of electron–hole pairs. Under visible light irradiation, the Au NPs are photo-excited due to the surface plasmon resonance effect, and charge separation is accomplished by the interfacial electron injection from the Au NPs to the conduction band of TiO₂ and then transfer further to graphene sheets. As a result, compared with pure TiO₂, Au/TiO₂/graphene composite exhibited much higher photocatalytic activity for degradation of methylene blue under both UV and visible light irradiation, based on the synergistic effect of Au, graphene in contact with TiO₂, allowing response to the visible light, effective separation of photoinduced charges, and better adsorption of the dye molecules.     

Photocatalytic Activity for Water Decomposition to Hydrogen over Nitrogen‐doped TiO2 Nanoparticle

Nitrogen-doped TiO2 nanoparticle photocatalysts were obtained by an annealing method with gaseous ammonia and nitrogen. The influence of dopant N on the crystal structure was characterized by XRD, XPS, BET, TEM and UV-Vis spectra. The results of XRD indicate that, the crystal phase transforms from anatase to rutile structure gradually with increase of annealing temperature from 300 to 700 ℃. XPS studies indicate that the nitrogen atom enters the TiO2 lattice and occupies the position of oxygen atom. Agglomeration of particles is found in TEM images after annealing. BET results show that the specific surface areas of N-doped samples from 44.61 to 38.27 m2/g are smaller than that of Degussa TiO2. UV-Vis spectra indicate that the absorption threshold shifts gradually with increase of annealing temperature, which shows absorption in the visible region. The influence of annealing condition on the photocatalytic property has been researched over water decomposition to hydrogen, indicating that nitrogen raises the photocatalytic activity for hydrogen evolution, and the modified TiO2 annealed for 2 h at 400 ℃ under gas of NH3/N2 (V/V＝1/2) mixture shows better efficiency of hydrogen evolution. Furthermore, the N-doped TiO2 nanoparticle catalysts have obvious visible light activity, evidenced by hydrogen evolution under visible light (λ＞400 nm) irradiation. However, the catalytic activity under visible light irradiation is absent for Degussa as reference and the N-doped TiO2 annealed at 700 ℃.     

Photo Catalytic Degradation of Azo Dyes over Mn2+ Doped TiO2 Catalyst under UV/Solar Light:An Insight to the Route of Electron Transfer in the Mixed Phase of Anatase and Rutile

Mn²⁺ ion was doped into the TiO₂ matrix and its photocatalytic activity was evaluated for the degradation of a mono azo dye methyl orange (MO) and a di‐azo dye brilliant yellow (BY) under UV/solar light. X‐ray diffraction results revealed the phase transformation from anatase to rutile due to the inclusion of Mn²⁺ ion into the TiO₂ matrix. All the doped catalysts showed a red shift in the band gap to the visible region. The degradation reaction of the dyes was found to be dependent on its structure. It was found that mono azo dye degrades faster than di azo dye under UV/solar light. The rate constant under identical conditions calculated for the degradation of MO is 2.4 times (under UV light) and 4.5 times (under solar light) higher compared to BY. Among the photocatalysts studied, Mn²⁺(0.06 at.%)‐TiO₂ showed higher activity under both UV and solar light illumination. The synergestic effect in the bicrystalline framework of anatase and rutile effectively suppresses the charge carrier recombination and enhances the photocatalytic activity. The degradation reaction was followed by UV‐visible spectroscopy and the photoproducts formed were analyzed by GC‐MS techniques.     

Photocatalytic activity of nitrogen and copper doped TiO2 nanoparticles prepared by microwave-assisted sol-gel process

Cu and N-doped TiO₂ photocatalysts were synthesized from titanium (IV) isopropoxide via a microwave-assisted sol-gel method. The synthesized materials were characterized by X-ray diffraction, UV-vis diffuse reflectance, photoluminescence (PL) spectroscopy, SEM, TEM, FT-IR, Raman spectroscopy, photocurrent measurement technique, and nitrogen adsorption–desorption isotherms. Raman spectra and XRD showed an anatase phase structure. The SEM and TEM images revealed the formation of an almost spheroid mono disperse TiO₂ with particle sizes in the range of 9-17 nm. Analysis of N₂ isotherm measurements showed that all investigated TiO₂ samples have mesoporous structures with high surface areas. The optical absorption edge for the doped TiO₂ was significantly shifted to the visible light region. The photocurrent and photocatalytic activity of pure and doped TiO₂ were evaluated with the degradation of methyl orange (MO) and methylene blue (MB) solution under both UV and visible light illumination. The doped TiO₂ nanoparticles exhibit higher catalytic activity under each of visible light and UV irradiation in contrast to pure TiO₂. The photocatalytic activity and photocurrent ability of TiO₂ have been enhanced by doping of the titania in the following order: (Cu, N) - codoped TiO₂ > N-doped TiO₂ > Cu-doped TiO₂ > TiO₂. COD result for (Cu, N)-codoped TiO₂ reveals ∼92% mineralization of the MO dye on six h of visible light irradiation.     

Application of cyclodextrins in cancer treatment

Four novel porphyrins and their corresponding zinc complexes were synthesized and characterized spectroscopically. Effects of the spacer length of peripheral substituents of porphyrin are investigated in TiO₂-porphyrins hybrid systems by photodegradation of methyl orange in aqueous solution under visible light. The photocatalysts were characterized by means of scanning X-ray diffraction, UV–Vis spectra, X-ray photoelectron spectroscopy and FT-IR spectra. The results indicated that zinc porphyrins were successfully loaded and interacted with the surface of TiO₂ microsphere, which is crucial to enhance the activity of the catalytic composite under visible light. All the new photocatalysts showed much enhanced photoactivity than bare TiO₂. Especially, the photocatalytic activity of 5,10,15-triphenyl-20-[4-(4-naphthoxy)butoxy] phenyl zinc porphyrin-TiO₂ is higher than others.     

Mesoporous interstitial and substitutional nitrogen-containing titanium dioxide photocatalysts prepared by acid-assisted sol–gel procedure

Two different types of nitrogen-containing TiO₂ were synthesized via an acid-modified sol–gel method. Yellow-colored interstitial and white substitutional nitrogen-containing TiO₂ powders were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller specific surface area and Barrett–Joyner–Halenda pore size distribution analyses, scanning electron microscopy, transmission electron microscopy and UV–vis absorption spectroscopy. The band gaps of interstitial and substitutional nitrogen-containing TiO₂ ceramics were estimated from UV–vis spectroscopy data to be 2.6 and 2.8 eV, respectively. Prepared substitutional nitrogen-containing TiO₂ featured steep light absorption edge with an approximately parallel characteristic to that in pure TiO₂. This fact is due to band-to-band visible light absorption ability of substitutional nitrogen-containing TiO₂. The photocatalytic properties of the produced nitrogen-containing TiO₂ samples were compared for the degradation of Direct Red 28 azo dye. Further studies were also devised to compare the catalytic efficiency of the nitrogen-containing TiO₂ powders with the pure TiO₂ synthesized via the similar sol–gel method. The produced nitrogen-containing TiO₂ samples revealed superior photocatalytic properties in comparison with pure TiO₂ due to their remarkable band gap narrowing, surface oxygen vacancies and much more surface defects. The results also revealed that the substitutional nitrogen-containing TiO₂ is the most effective photocatalyst under ultraviolet and visible light irradiation.     

Elaboration of nano titania-magnetic reduced graphene oxide for degradation of tartrazine dye in aqueous solution

In this paper, magnetic nanocomposites are synthesized by loading reduced graphene oxide (RG) with two components of nanoparticles consisting of titanium dioxide (TiO₂) and magnetite (Fe₃O₄) with varying amounts. The structural and magnetic features of the prepared composite photocatalysts were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (UV–vis/DRS), Raman and vibrating sample magnetometer (VSM). The resulting TiO₂/magnetite reduced graphene oxide (MRGT) composite demonstrated intrinsic visible light photocatalytic activity, on degradation of tartrazine (TZ) dye from a synthetic aqueous solution. Specifically, it exhibits higher photocatalytic activity than magnetite reduced graphene oxide (MRG) and TiO₂ nanoparticles. The photocatalytic degradation of TZ dye when using MRG and TiO₂ for 3 h under visible light was 35% and 10% respectively, whereas for MRGT it was more than 95%. The higher photocatalytic efficiency of MRGT is due to the existence of reduced graphene oxide and magnetite which enhances the photocatalytic efficiency of the composite in visible light towards the degradation of harmful soluble azo dye (tartrazine).     

Controlled crystal phase and particle size of loaded-TiO2 using clinoptilolite as support via hydrothermal method for degradation of crystal violet dye in aqueous solution

TiO₂-supported clinoptilolites (TiO₂/clinoptilolites) were successfully synthesized with controlled crystal phase and particle size via hydrothermal method to enhance photocatalytic performance of TiO₂. The effects of various parameters including temperature, acidity and concentration of Ti-containing solutions on the particle size, crystal phase and agglomeration of TiO₂ supported on clinoptilolite were investigated thoroughly by characterizations of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), BET isotherm, UV–visible (UV–vis) spectrophotometer and Malvern zetasizer. The results demonstrate that increasing temperature and strengthen acidity are beneficial to enhance the crystallinity and particle size of supported TiO₂. Increase in acidity also leads to more uniform distribution of TiO₂ on the surface of clinoptilolite. The TiO₂ nano-crystals deposited on the surface of clinoptilolite, exhibit rutile or anatase phase, strongly depending on the preparation procedure. The resultant TiO₂/clinoptilolites could be used as photo-catalysts for the degradation of crystal violet (CV) dye in aqueous solution, showing a higher photo-catalytic activity with 89% degradation within 100 min. The effect of operational parameters, such as pH values of reaction media, dose of used catalyst, and concentration of CV dye on the CV degradation performance were investigated, in which the kinetics of CV dye degradation was found to follow the pseudo-first order kinetic model.     

Removal of an organic pollutant from waste water by photocatalytic behavior of AgX/TiO2 loaded on mordenite nanocrystals

Mordenite (MOR) nanocrystals were synthesized using the hydrothermal method. Sol–gel and deposition methods were utilized to modify the zeolite surface with TiO₂ and then AgBr or AgCl particles. Photocatalysts were characterized by using X-ray diffraction, Brunauer–Emmett–Teller (BET), and scanning electron microscopy techniques. Activity was evaluated by photodegradation of Acid Blue 92 as an azo dye. The effect of silver halide deposition on the photocatalytic behavior of the prepared nanocomposites was studied under both ultraviolet (UV) and visible light, and the results were compared. The results showed that AgCl/TiO₂/MOR was more active under UV, while with visible source, AgBr/TiO₂/MOR exhibited better photocatalytic performance. A mechanism for the reaction is also proposed.     

Visible‐Light‐Induced Photoredox Catalysis of Dye‐Sensitized Titanium Dioxide: Selective Aerobic Oxidation of Organic Sulfides

TiO₂ photoredox catalysis has recently attracted much interest for use in performing challenging organic transformations under mild reaction conditions. However, the reaction scheme is hampered by the fact that TiO₂ can only be excited by UV light of wavelengths λ shorter than 385 nm. One promising strategy to overcome this issue is to anchor an organic, preferably metal‐free dye onto the surface of TiO₂. Importantly, we observed that the introduction of a catalytic amount of the redox mediator TEMPO [(2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl] ensured the stability of the anchored dye, alizarin red S, thereby resulting in the selective oxidation of organic sulfides with O₂. This result affirms the essential role of the redox mediator in enabling the organic transformations by visible‐light photoredox catalysis.     

Efficient and Robust Cu/TiO2 Nanorod Photocatalysts for Simultaneous Removal of Cr(VI) and Methylene Blue under Solar Light

Because of its large bandgap, TiO₂ can function only under UV light. TiO₂ surface modification with noble metal nanoparticles can extend the light absorption from UV to visible light region and enhance the photocatalytic quantum yield. In this work, TiO₂ nanorods (Cu/TiO₂) modified by copper nanoparticles were prepared by a one‐step solvothermal method at low cost. The resultant Cu/TiO₂ nanorods show excellent synergistic effect in the oxidation of methylene blue (MB) and the reduction of aqueous Cr(VI) under solar light irradiation. Mechanistic investigation suggests that the Cr(VI) species could effectively scavenge the electrons from MB in the presence of the as‐prepared photocatalyst, leading to the simultaneous removal of both pollutants. Being economically viable, environmentally sustainable, and highly efficient, the proposed photocatalyst holds promise for technologies involving simultaneous organic degradation and heavy metal removal in wastewater treatment.     

Eliminated Phototoxicity of TiO2 Particles by an Atomic‐Layer‐Deposited Al2O3 Coating Layer for UV‐Protection Applications

We demonstrate the conformal coating of an ultrathin Al₂O₃ layer on TiO₂ nanoparticles through atomic layer deposition by using a specifically designed rotary reactor to eliminate the phototoxicity of the particles for cosmetic use. The ALD reactor is modified to improve the coating efficiency as well as the agitation of the particles for conformal coating. Elemental and microstructural analyses show that ultrathin Al₂O₃ layers are conformally deposited on the TiO₂ nanoparticles with a controlled thickness. Rhodamine B dye molecules on Al₂O₃‐coated TiO₂ exhibited a long life time under UV irradiation, that is, more than 2 h, compared to that on bare TiO₂, that is, 8 min, indicating mitigation of photocatalytic activity by the coated layer. The effect of carbon impurities in the film resulting from various deposition temperatures and thicknesses of the Al₂O₃ layer on the photocatalytic activity are also thoroughly investigated with controlled experimental condition by using dye molecules on the surface. Our results reveal that an increased carbon impurity resulting from a low processing temperature provides a charge conduction path and generates reactive oxygen species causing the degradation of dye molecule. A thin coated layer, that is, less than 3 nm, also induced the tunneling of electrons and holes to the surface, hence oxidizing dye molecules. Furthermore, the introduction of an Al₂O₃ layer on TiO₂ improves the light trapping thus, enhances the UV absorption.     

Photodegradation of dye pollutants on one-dimensional TiO2 nanoparticles under UV and visible irradiation

Titanium dioxides (TiO₂) nanoparticles with one-dimensional (1D) geometry, nanorods and nanostripes, were used as photocatalysts to photodegrade Rhodamine B (RhB) under ultraviolet (UV) and visible irradiation. The nanorods catalyst exhibited very interesting photocatalytic properties: under the UV irradiation its catalytic activity was slightly below that of the well-known TiO₂ catalyst P25, while under visible light it exhibited a better activity than P25.This fact indicates that the nanorods have a superior ability to utilize less energetic but more abundant visible light. Moreover, the 1D TiO₂ nanoparticles can be readily separated from aqueous suspensions by sedimentation after the reaction. With these advantages the 1D TiO₂ catalysts have a great potential for environmental applications. Various analytical techniques were employed to characterize TiO₂ catalysts and monitor the photocatalytic reaction. It was found that the catalytic performance of the catalysts is greatly dependent on their structures: The superior activity of P25 (consists of anatase and rutile nanocrystals) under UV light results probably from the interfacial interaction between anatase and rutile nanocrystals in this solid, which do not exist in the nanorods (only anatase). The titanate nanostripes (titanate) can absorb UV photons with shorter wavelength only.     

Preparation and characterization of mesoporous TiO2-CeO2 nanopowders respond to visible wavelength

Mesoporous TiO₂-CeO₂ nanopowders responding to visible wavelength were synthesized by using a surfactant assisted sol-gel technique. They were obtained using metal alkoxide precursors modified with acetylacetone (ACA) and laurylamine hydrochloride (LAHC) as surfactant. The samples were characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and selected area electron diffraction (SAED), respectively. The 95 mol% TiO₂-5 mol% CeO₂ system yielded single anatase phase, however, further addition of the CeO₂ formed cubic CeO₂ structure while anatase TiO₂ decreased. Additions of 5 and 10 mol% CeO₂ increased the surface area, but those of 25, 50, and 75 mol% CeO₂ did not affect it very much. By using this mixed metal oxides system, TiO₂ can be modified to respond to the visible wavelength. The mixed metal oxides had catalytic activity (evaluating the formation rate of I₃⁻) about 2-3 times higher than pure CeO₂, while nanosize anatase type TiO₂ materials had no catalytic activity under visible light. The catalytic activity was almost proportional to the specific surface area. The formation rate of I₃⁻ was much improved by changing the calcination temperature and calcination period. Highest catalytic activity in this study was obtained for the 50 mol% TiO₂-50 mol% CeO₂ nanopowders calcined at 250 °C for 24 h.     

Photodegradation of the aminoazobenzene acid orange 52 by three advanced oxidation processes: UV/H2O2, UV/TiO2 and VIS/TiO2: Comparative mechanistic and kinetic investigations

This paper presents the results obtained from the oxidation of the aminoazobenzene dye AO52 by the UV/H₂O₂, UV/TiO₂ and VIS/TiO₂ systems. In the former case, we investigated the formation of first by-products by means of GC/MS, HPLC and ¹H NMR. spectroscopy. We conclude that hydroxyl radicals are added to aromatic rings in the ipso position with respect to the sulfonate group or to the azo-linkage-bearing carbon. The reaction of the inorganic radical with the N,N-dimethylamino substituent, leading to demethylation, adds to the multiplicity of the possible pathways. Degradation by the UV/TiO₂ system is pH dependent. Whereas hydroxyl radicals are the main oxidative agent in neutral and alkaline solutions, positive hole-induced oxidation competes with the reduction of the protonated dye molecules in acid media. Moreover, FTIR spectroscopy of AO52/TiO₂ wafers provided an insight to the nature of the photoproducts. This process is very efficient since only ultimate breakdown products, i.e. aliphatic acids and inorganic salts, are detected. Similar results were obtained using visible light as the irradiation source in the case of wafers whereas in heterogeneous solutions, the dye seems to be resistant to degradation.     

Surface Modifications and Optoelectronic Characterization of TiO2‐Nanoparticles: Design of New Photo‐Electronic Materials

TiO₂ nanoparticles are of great current interest for applications in photo‐electronic materials including light‐energy conversion, artificial photosynthetic systems as well as photocatalysis. The success of these applications relies on the exciton recombination dynamics and visible‐light sensitivity of the TiO₂ nanomaterials. Thus, in order to develop the highly efficient photo‐electronic materials absorbing visible light, different low dimensional TiO₂ nanostructures such as nanodiscs, nanofibers and nanochains were synthesized, and thereafter their surfaces were modified by incorporating with Sn‐porphyrins and heteropoly acid. The optoelectronic properties of the surface‐modified nanomaterials were investigated with regard to the optical properties and the surface exciton dynamics by using both steady‐state and ultrafast time‐resolved laser spectroscopic techniques including single nanoparticle photoluminescence technique. These results were correlated with the photo‐electronic properties including photocatalytic activities and solar cell efficiencies, indicating that the electron transfer mechanism in the modified nanostructures may be similar to the “Z‐scheme” of the plant photosynthetic system so that both photocatalytic activity and solar cell efficiencies were synergistically enhanced by using two color illumination.     

Preparation of magnetically supported chromium and sulfur co-doped TiO2 and use for photocatalysis under visible light

Novel magnetic chromium and sulfur co-doped TiO₂ photocatalysts (M-Cr/S/TiO₂) have been prepared by a sol?Cgel process, using magnetic hollow fly ash microspheres as support material. The crystal phase of M-Cr/S/TiO₂ was characterized by X-ray diffraction, UV?Cvisible absorption spectroscopy, and transmission electron microscopy. The photocatalytic activity of the photocatalysts was examined by photodegradation of methyl orange in aqueous solution under visible light irradiation. The results showed that chromium and sulfur co-doped catalysts (Cr/S/TiO₂) containing 0.60?% (atomic ratio) chromium and 1.2?% (atomic ratio) sulfur calcined at 450?°C for 2?h had high catalytic efficiency under visible irradiation. It is worth mentioning that the floating M-Cr/S/TiO₂ catalyst had greater photocatalytic activity than Cr/S/TiO₂ powder. Therefore, M-Cr/S/TiO₂ is a promising, high-performing, visible-light-driven photocatalyst.