Enhanced Photocatalytic Performances of CeO2/TiO2 Nanobelt Heterostructures

CeO₂/TiO₂ nanobelt heterostructures are synthesized via a cost‐effective hydrothermal method. The as‐prepared nanocomposites consist of CeO₂ nanoparticles assembled on the rough surface of TiO₂ nanobelts. In comparison with P25 TiO₂ colloids, surface‐coarsened TiO₂ nanobelts, and CeO₂ nanoparticles, the CeO₂/TiO₂ nanobelt heterostructures exhibit a markedly enhanced photocatalytic activity in the degradation of organic pollutants such as methyl orange (MO) under either UV or visible light irradiation. The enhanced photocatalytic performance is attributed to a novel capture–photodegradation–release mechanism. During the photocatalytic process, MO molecules are captured by CeO₂ nanoparticles, degraded by photogenerated free radicals, and then released to the solution. With its high degradation efficiency, broad active light wavelength, and good stability, the CeO₂/TiO₂ nanobelt heterostructures represent a new effective photocatalyst that is low‐cost, recyclable, and will have wide application in photodegradation of various organic pollutants. The new capture–photodegradation–release mechanism for improved photocatalysis properties is of importance in the rational design and synthesis of new photocatalysts.     

In-situ synthesis of TiO2 nanostructures on Ti foil for enhanced and stable photocatalytic performance

TiO_2 nanostructures with strong interfacial adhesion and diverse morphologies have been in-situ grown on Ti foil substrate through a multiple-step method based on conventional plasma electrolytic oxidation(PEO) technology, hydrothermal reaction and ion exchange process. The PEO process is critical to the formation of TiO_2 seeding layer for the nucleation of Na_2Ti_3O_7 and H_2Ti_3O_7 mediates that are strongly attached to the Ti foil. An ion exchange reaction can finally lead to the formation of H_2Ti_3O_7 nanostructures with diverse morphologies and the calcination process can turn the H_2Ti_3O_7 nanostructures into TiO_2 nanostructures with enhanced crystallinity. The morphology of the TiO_2 nanostructures including nanoparticles(NP), nanowhiskers(NWK), nanowires(NW) and nanosheets(NS) can be easily tailored by controlling the NaOH concentration and reaction time during hydrothermal process. The morphology, composition and optical properties of TiO_2 photocatalysts were analyzed using scanning electron microscope(SEM), X-ray diffraction(XRD), photoluminescence(PL) spectroscopy and UV–vis absorption spectrum. Photocatalytic tests indicate that the TiO_2 nanosheets calcined at 500?C show good crystallization and the best capability of decomposing organic pollutants. The decoration of Ag cocatalyst can further improve the photocatalytic performance of the TiO_2 nanosheets as a result of the enhanced charger separation efficiency. Cyclic photocatalytic test using TiO_2 nanostructures grown on Ti foil substrate demonstrates the superior stability in the photodegradation of organic pollutant, suggesting the promising potential of in-situ growth technology for industrial application.     

Solar photocatalysts from Gd–La codoped TiO2 nanoparticles

Gd–La codoped TiO₂ nanoparticles with diameter of 10 nm were successfully synthesized via a sol–gel method. The photocatalytic activity of the Gd–La codoped TiO₂ nanoparticles evaluated by photodegrading methyl orange has been significantly enhanced compared to that of undoped or Gd or La monodoped TiO₂. Ti⁴⁺ may substitute for La³⁺ and Gd³⁺ in the lattices of rare earth oxides to create abundant oxygen vacancies and surface defects for electron trapping and dye adsorption, accelerating the separation of photogenerated electron–hole pairs and methyl orange photodegradation. The formation of an excitation energy level below the conduction band of TiO₂ from the binding of electrons and oxygen vacancies decreases the excitation energy of Gd–La codoped TiO₂, resulting in versatile solar photocatalysts. The results suggest that Gd–La codoped TiO₂ nanoparticles are promising for future solar photocatalysts.     

Graphdiyne-hybridized N-doped TiO<Subscript>2</Subscript> nanosheets for enhanced visible light photocatalytic activity

In this study, graphdiyne (GD)-hybridized nitrogen-doped TiO₂ nanosheets with exposed (001) facets (GD-NTNS) have been prepared via a hydrothermal reaction and utilized as photocatalyst for the photodegradation of rhodamine B (RhB) under visible light illumination. The resultant GD-NTNS composites exhibit superior visible light photocatalytic activity than that of the bare TiO₂ nanosheets (TNS) and nitrogen-doped TiO₂ nanosheets (NTNS). The enhanced photoactivity can be attributed to the synergistic effects of GD and nitrogen doping with efficient electron transfer and strong visible light absorption. It has been revealed that ^·O^2? and h⁺ are the major species for the enhanced photoactivity under visible light. Our work will facilitate the potential for future design of hybrid materials for practical applications beyond photocatalysts.     

Removal of fluoride from aqueous solution by polypyrrole/Fe3O4 magnetic nanocomposite

Highly efficient visible light TiO₂ photocatalyst was prepared by the sol-gel method at lower temperature (≤300 °C), and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and differential scanning calorimetry-thermogravimetric analysis (DSC-TGA). The effects of the heat treatment temperature and time of the as-prepared TiO₂ on its visible light photocatalytic activity were investigated by monitoring the degradation of methyl orange solution under visible light irradiation (wavelength ≥ 400 nm). Results show that the as-prepared TiO₂ nanoparticles possess an anatase phase and mesoporous structure with carbon self-doping and visible photosensitive organic groups. The visible light photocatalytic activity of the as-prepared TiO₂ is greatly higher than those of the commercial TiO₂ (P-25) and other visible photocatalysts reported in literature (such as PPy/TiO₂, P3HT/TiO₂, PANI/TiO₂, N-TiO₂ and Fe³⁺-TiO₂) and its photocatalytic stability is excellent. The reasons for improving the visible light photocatalytic activity of the as-prepared TiO₂ can be explained by carbon self-doping and a large amount of visible photosensitive groups existing in the as-prepared TiO₂. The apparent optical thickness (τ_app), local volumetric rate of photo absorption (LVRPA) and kinetic constant (k_T) of the photodegradation system were calculated.     

Ferroin adsorption on TiO<Subscript>2</Subscript>-based photocatalytic materials

We have studied ferroin adsorption on photocatalytically active nanocomposites based on TiO₂ doped with Fe³⁺, Nb⁵⁺, or W⁶⁺. The results demonstrate that the mass of an adsorbed organic substance correlates with the photocatalytic activity of the photocatalysts. High-temperature heat treatment of the nanocomposites increases manyfold the mass of an organic substance adsorbed from an aqueous solution for unit free surface area of the photocatalyst.     

Iron promotion of the TiO2 photosensitization process towards the photocatalytic oxidation of azo dyes under solar-simulated light irradiation

The photocatalytic oxidation of the azo dye Orange-II (Or-II) using Fe loaded TiO₂ (Fe–TiO₂) was studied under ultraviolet (UV), visible (vis) and simultaneous UV–vis irradiations using a solar light simulator. Photocatalysts were characterized by means of XRD, SEM-EDX, FTIR and DRS. Fe³⁺ species, identified in XPS analyses, were responsible of the increased absorption of visible light. Moreover, DRS analyses showed a decrease in the bandgap due to Fe³⁺ loading. Photocatalystic tests proved that Fe modification enhanced the TiO₂ photocatalytic activity towards Or-II photodegradation under simultaneous UV–vis irradiation. Even so, the performance of the Fe–TiO₂ samples towards the photodegradation of phenol, under UV irradiation, was lower than TiO₂ suggesting the recombination of the UV photogenerated electron–hole pair. Therefore, results evidence a Fe³⁺ promotion of the electron caption in the photosensitization process of TiO₂ by Or-II acting as a sensitizer. Such process leads to the Or-II photooxidation under UV–vis irradiation by losing energy in electron transferring processes to sensitize TiO₂, and, the formation of reactive oxygen species promoted by the injected electron to the TiO₂ conduction band.     

Synthesis of novel Cu doped anatase TiO<Subscript>2</Subscript> catalysts and assessment of the influence of Nb concentration on the photocatalytic and electrochemical properties

In the present study, Cu doped (Ti_0.8Cu_xO_2?x/2) and (Cu, Nb) co-doped (Ti_0.8Cu_x?y Nb_yO_2?(x?y/2+y)) TiO₂ photocatalysts were fabricated by sol–gel method. The catalysts were polycrystalline in nature with preferential orientation along (101) plane answering to anatase phase of TiO₂. Higher Nb concentration results in the formation of secondary phase (Nb₂O₅). A decrease in average crystallite size was noticed with the addition of Nb concentration in Cu doped TiO₂ photocatalyst. The formation of anatase phase was also fixed by Raman spectra. The TEM photograph confirmed the co-doped TiO₂ photocatalyst in nanometer range of about 15 nm and the particles were in hexagonal shape. The doping of Nb⁵⁺ ions inspired a shift in the absorption threshold towards the visible spectral range (red shift) compared to Cu doped TiO₂ catalyst. The photocatalysts have direct bandgaps of 3.253 to 2.974 eV. Semiconducting properties were investigated through electrochemical impedance spectroscopy. The results indicate that the presence of Nb⁵⁺ ions into Cu doped TiO₂ has enhanced the efficiency of electrochemical conductivity. Photocatalytic performance was assessed from the sample degradation by illuminating methylene blue dye under visible light exposure. It is found that TCN3 photocatalyst bleaches MB much faster than all others. Also it exhibits great improvement of photocatalytic activity (96.86%) within 120 min. The photocatalytic degradation process is explained using the pseudo first order kinetics and it fits well with higher correlation coefficient. All these analyses elucidate that the incorporation of Nb⁵⁺ ions might tune the structural, optical, electrochemical and phocatalytic properties of Cu doped TiO₂ photocatalysts.     

Preparation, characterization and application of TiO2 nanoparticles surface-modified by DDAT

DDAT(S-1-Dodecyl-S′-(α, α′-dimethyl-α″-acetic acid) trithiocarbonate) modified TiO₂ photocatalysts were prepared by hydrothermal treatment before TiO₂ crystallization. The adsorption of DDAT onto the surface of titania nanoparticles led the shifting of the onset wavelength of the optical absorption in the visible range corresponding to ligand-to-metal charge transfer transition within the surface-modified complex. The interaction of TiO₂ nanoparticles with DDAT was investigated by infrared spectra. The XRD indicated that the modification process could not influence the crystallite phase of TiO₂. The photocatalytic studies suggested that the DDAT modified TiO₂ photocatalysts showed enhanced photocatalytic efficiency of photodegradation of 2,4-dichlorophenol compared with the as-prepared TiO₂ under visible-light irradiation.     

Synthesis,characterization, photocatalytic evaluation,and toxicity studies of TiO2–Fe3+ nanocatalyst

Based on our previous work on the green preparation of Ag–TiO₂ photocatalyst with bactericidal activity under visible light, we extended our studies to the synthesis of TiO₂–Fe³⁺ materials with enhanced photocatalytic activity for the degradation of recalcitrant organic pollutants in water. TiO₂–Fe³⁺ nanopowders were synthesized using a robust, environmentally friendly procedure. Established amounts of Fe(NO₃)₃·9H₂O and titanium tetraisopropoxide (TTIP) were mixed using glacial acetic acid as solvent. Hydrolysis of TTIP–Fe³⁺ was accomplished using a 30 % (W/V) Arabic gum aqueous solution. TiO₂–Fe³⁺ nanopowders were obtained by thermal treatment at 400 °C. In order to elucidate the structure of these photocatalysts, microscopic and spectroscopic characterization techniques were applied. The high resolution transmission electron microscopy (HRTEM) analysis indicated the presence of uniformly distributed particles with average particle size of about 9 nm. According to the HRTEM lattice fringes, ring pattern, and selected area electron diffraction pattern, the crystalline part of the samples consists of anatase (PDF 01-086-1157 with the lattice constant of 3.7852, 9.5139 Å and 90°) as dominant phase. X-ray photoelectron spectroscopy (XPS) was applied to determine the oxidation state of iron. The XPS provides evidence for Fe³⁺ surface species in the TiO₂–Fe³⁺ composite. Complete degradation of aqueous solutions (20 ppm) of methylene blue and/or methyl orange was accomplished after 4 h of treatment using 150 mg of TiO₂–Fe³⁺/150 mL of dye solution. The in vitro toxicity of the materials was tested. The materials showed no toxicity against human red blood cells.     

Efficient SiO2/WO3–TiO2@rGO nanocomposite photocatalyst for visible-light degradation of colored pollutant in water

The photoactive SiO₂/WO₃–TiO₂@rGO nanocomposite was fabricated through sol–gel, microwave, and hydrothermal approaches for the photodegradation of methylene blue (MB) as an organic-colored pollutant. The nanocomposite photocatalysts were formulated by adjustment of the ingredients content to achieve efficient synergic effects on photocatalyst performance. The results exhibited that optimum amount of SiO₂ and rise in WO₃/TiO₂ ratio as well as incorporation of reduced graphene oxide in structure can be led to further efficiency of degradation under visible light. The effect of sunlight irradiation, pH of MB solution, MB concentration, and lamp distance on photodegradation reaction were also investigated. The best performance about 99.9% MB degradation was obtained based on using 0.3 g/L of optimum photocatalyst to remove the 5 ppm MB solution with pH of 5.41 during 3 h irradiation by visible-light source with 30 cm distance from MB solution. As well, results showed that photocatalyst performance under visible light is better than sunlight irradiation. The most favorable photocatalyst indicated surface area of 60.9 m²/g. Furthermore, the reusability test indicated a proper activity after three cycles under the same conditions. So, the introduced efficient visible photoactive SiO₂/WO₃–TiO₂@rGO nanocomposite can be considered as an appropriate potential to remove organic pollutants in colored effluents.

     

Electrospun mesoporous W-doped TiO2 thin films for efficient visible-light photocatalysis

Mesoporous W⁶⁺-doped TiO₂ thin films photocatalysts were prepared via electrospinning and sol-gel chemistry, employing a triblock copolymer as structure-directing agent, and were characterized by SEM, TEM, XRD as well as N₂ adsoption/desorption isotherm. The photocatalytic activity of the films was investigated by employing the methylene blue (MB) as probe. In this study, 3% was the most suitable content of W⁶⁺ in TiO₂, at which the recombination of photoinduced electrons and holes could be effectively inhibited. In the mean time, making the photocatalysts at nanoscale and with mesopores in the films could produce more reactive sites to adsorbe and oxidize pollutants.     

Upconversion nanotubes with tunable fluorescence properties based on Gd2 O2 S:Ln3+ (Ln3+ = Yb3+, Er3+) and derivatives for photodynamic therapy

In this study, Gd₂ O₂ S:Ln³⁺ (Ln³⁺  = Yb³⁺, Er³⁺) upconversion nanotubes (UCNTs) were synthesised by using Gd(OH)₃ :Ln³⁺ (Ln³⁺  = Yb³⁺, Er³⁺) nanotubes as the template. The luminescent and biological properties of Gd₂ O₂ S:Ln³⁺ (Ln³⁺  = Yb³⁺, Er³⁺) UCNTs, along with photodynamic therapy (PDT) applications of the Gd₂ O₂ S:8%Yb³⁺, 2%Er³⁺ UCNT–Ce6 (chlorin e6) nanocomposites, were systematically studied. The resultant UCNTs showed excellent biocompatibility with human retinal pigment cells (ARPE‐19) even after a prolonged incubation time of 72 h, and could be used as luminescent probes. Microscopic imaging revealed that the UCNTs existed mainly in cytoplasm. PDT studies on the Gd₂ O₂ S:8%Yb³⁺, 2%Er³⁺ UCNT–Ce6 nanocomposites indicate that the growth of the tumour (cell) could be inhibited dramatically when it was injected (incubated) with Gd₂ O₂ S:8%Yb³⁺, 2%Er³⁺ UCNT–Ce6 nanocomposites under the irradiation of 980 nm laser.Inspec keywords: biomedical materials, nanofabrication, tumours, cellular biophysics, nanomedicine, eye, biomedical optical imaging, nanocomposites, gadolinium compounds, ytterbium, photodynamic therapy, fluorescence, erbium, laser beam effectsOther keywords: luminescent properties, biological properties, photodynamic therapy applications, UCNT–Ce6 nanocomposites, upconversion nanotubes, tunable fluorescence properties, biocompatibility, human retinal pigment cells, microscopic imaging, PDT studies, tumour, laser irradiation, wavelength 980.0 nm, time 72.0 hour, Gd₂ O₂ S:Yb,Er     

Applying Ag–TiO2/functional filter for abating odor exhausted from semiconductor and opti-electronic industries

Some of the odor-related problems from the semiconductor and opti-electronic industries are caused by the volatile organic compounds, acetic acid, and dimethyl sulfide. These odorous exhausts would persecute residents’ health and lower the environmental quality. In this study, Ag–TiO₂/functional filter was applied to removal these odorous compounds. The results indicated that K₂CO₃/activated carbon filter (ACF) would be the better composition of functional filter, which attributed to larger surface area of ACF and mid-alkalinity of K₂CO₃. Comparing the TiO₂ type, P25 TiO₂ (Degussa, Germany)/functional filter showed the more superior photodegradation efficiency than ST01 TiO₂ (Ishihra Sangyo, Japan)/functional filter. In addition, Ag-modifying TiO₂/functional filter enhanced the photocatalysis via postponing the recombination between electrons and holes. The 0.001 M AgNO₃ solution was the optimal immersing concentration to make Ag dispersed uniformly on TiO₂ surface. Operating from 25 to 50 °C, the rising temperature was contributive to photodegradation efficiency due to the increase of system reaction energy. Processing photocatalysis below 75 % of relative humidity, existing humidity could be combined with holes to from hydronium (H₃O⁺) and hydroxyl radical (OH^?) to improve photodegradation. Assisted with ozone concentration ratio of 0.7 times, the removal efficiency for high pollutant concentration via Ag–TiO₂/functional filter could be improved up to 90 % until operating 180 min; this combined method could save the oxidant consumption more than single advanced oxidation method for processing pollutant.     

Ultraviolet upconversion luminescence in Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Yb<Superscript>3+</Superscript>,Tm<Superscript>3+</Superscript> nanocrystals and its application in photocatalysis

Infrared-to-ultraviolet upconversion luminescence agent Y₂O₃:Yb³⁺,Tm³⁺ was prepared by a combustion method using citrate as a fuel/reductant. The prepared sample was characterized by X-ray diffraction, SEM, and fluorescence spectrophotometer. Two unusual ¹I₆ → ³H₆ (~297 nm) and ¹D₂ → ³H₆ (~363 nm) emissions from Tm³⁺ ions were observed at room temperature under 980-nm laser excitation. The change of upconversion emission intensity depending on the Yb³⁺ concentrations was discussed. The results showed that modest Yb³⁺ doping could make the upconversion emission of Tm³⁺ intense, and high Yb³⁺ concentrations might lead to fluorescence quenching. Moreover, the influence of ultraviolet upconversion luminescence on the photodegradation of methyl orange aqueous solution under solar light irradiation in the presence of TiO₂ catalyst doped with Y₂O₃:Yb³⁺,Tm³⁺ was also investigated. It was concluded from the experiment of this study that TiO₂/Y₂O₃:Yb³⁺,Tm³⁺ composite had higher photocatalytic activity than pure TiO₂ under solar light. This study would make TiO₂ utilize sunlight more efficiently and accelerate the practical application of photocatalytic technology in water treatment region.     

Photocatalytic activity of β-MnO2 nanotubes grown on PET fibre under visible light irradiation

Development of visible light response semiconductor photocatalysts in degradation of organic compounds (pollutants) is one of the current research focuses due to the severe environmental pollution from various industrial and agricultural pollutants in water bodies. In this work, β-MnO₂ particles were successfully prepared by sol-gel method with potassium permanganate and manganese (II) sulphate as precursors. The transmission electron microscope/selected area electron diffraction analysis indicates that the particles were polycrystals with tubular structure. The photodegradation of Rhodamine B (RhB) solution using β-MnO₂ nanotubes under visible irradiation followed 1^st order kinetic with rate constant of 0.022 ± 0.003 min^?1 and photodegradation efficiency of 90.3% after 120 min under visible light irradiation. The N-deethylation was the dominant process in photodegradation of RhB dye by β-MnO₂ nanotubes as compared to cycloreversion process. By applying similar synthesis condition, the β-MnO₂ nanotubes were successfully synthesised on PET fibre. The photodegradation efficiency of RhB dye under circulation condition by β-MnO₂ nanotubes grown on PET fibre under visible light irradiation was 1.23 h^?1. The result suggests that β-MnO₂ nanotubes grown on PET fibre could be used as visible light-driven photocatalysts for wastewater purifier application.     

Hybridized 2D Nanomaterials Toward Highly Efficient Photocatalysis for Degrading Pollutants: Current Status and Future Perspectives

Organic pollutants including industrial dyes and chemicals and agricultural waste have become a major environmental issue in recent years. As an alternative to simple adsorption, photocatalytic decontamination is an efficient and energy‐saving technology to eliminate these pollutants from water environment, utilizing the energy of external light, and unique function of photocatalysts. Having a large specific surface area, numerous active sites, and varied band structures, 2D nanosheets have exhibited promising applications as an efficient photocatalyst for degrading organic pollutants, particularly hybridization with other functional components. The novel hybridization of 2D nanomaterials with various functional species is summarized systematically with emphasis on their enhanced photocatalytic activities and outstanding performances in environmental remediation. First, the mechanism of photocatalytic degradation is given for discussing the advantages/shortcomings of regular 2D materials and identifying the importance of constructing hybrid 2D photocatalysts. An overview of several types of intensively investigated 2D nanomaterials (i.e., graphene, g‐C₃N₄, MoS₂, WO₃, Bi₂O₃, and BiOX) is then given to indicate their hybridized methodologies, synergistic effect, and improved applications in decontamination of organic dyes and other pollutants. Finally, future research directions are rationally suggested based on the current challenges.     

Synthesis of β–NaYF4: Yb3+, Tm3+ @ TiO2 and β–NaYF4: Yb3+, Tm3+ @ TiO2 @ Au nanocomposites and effective upconversion–driven photocatalytic properties

The β–NaYF₄: Yb³⁺, Tm³⁺ @ TiO₂ nanocomposite has been prepared by a facile hydrothermal method followed by the hydrolysis of TBOT, and then NaYF₄: Yb³⁺, Tm³⁺ @ TiO₂, HAuCl₄ and sodium citrate were put into an oil bath for reaction to obtain the β–NaYF₄: Yb³⁺, Tm³⁺ @ TiO₂ @ Au core–shell nanocomposite. XRD and HRTEM show that the samples exhibit the hexagonal phase NaYF₄, anatase TiO₂ and cubic Au, indicating that the core–shell phases of NaYF₄−TiO₂ or NaYF₄−TiO₂−Au coexist in these samples. EDS and XPS results show the presence of Na, Y, F, Ti, O and Au elements. When TiO₂ was coated on the surface of upconversion nanomaterials of NaYF₄: Yb³⁺, Tm³⁺, the photocatalytic activity was improved significantly, and the β–NaYF₄: Yb³⁺, Tm³⁺ @ TiO₂ nanocomposite gives the highest photodegradation efficiency for MB and RhB, and decomposes about 73% of MB or 80% of RhB within 4.5 h under simulated solar light irradiation respectively. When the ultraviolet light from simulated sunlight irradiation was removed by the addition of a UV filter, the β–NaYF₄: Yb³⁺, Tm³⁺ @ TiO₂ nanocomposite decomposes about 42% of MB or 48% of RhB within 4.5 h. It means that the upconversion–driven photocatalytic performance (decomposes 42% of MB or 48% of RhB) is more effective than UV light–driven photocatalytic performance (31% of MB or 32% of RhB) in the photodegradation process. In addition, the β–NaYF₄: Yb³⁺, Tm³⁺ @ TiO₂ @ Au core–shell nanocomposite does not exhibit the better photocatalytic activity, and the optimal research will be carried out in the future.     

Undoped visible-light-sensitive titania photocatalyst

Colorful rutile TiO₂ was prepared by heating Ti₂O₃ at 550–900 °C to develop novel visible-light-sensitive and eco-friendly photocatalysts for environmental remediation under visible-light irradiation. The colors of the prepared samples, which ranged from grayish green to yellowish off-white via yellow differed from the reported colors of reduced TiO₂, such as blue and black. The TiO₂ prepared in this study was characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and UV–Visible spectroscopy. These measurements showed that the TiO₂ contained Ti³⁺-interstitial sites. The TiO₂ was sensitive to visible light, and calculation of the band diagram demonstrated that this visible-light absorption is caused mainly by formation of Ti³⁺-interstitial sites in rutile TiO₂. Among the prepared samples, the TiO₂ prepared by heating Ti₂O₃ at 700 °C shows the highest photocatalytic activity under visible-light irradiation. In addition, the sample was further and mildly ground using a bead-milling machine. The ground sample possessed higher surface area and better photocatalytic activity.     

Rapid microwave-assisted solvothermal synthesis and visible-light-induced photocatalytic activity of Er3+-doped BiOI nanosheets

BiOI nanosheet photocatalysts with different Er³⁺ doping contents were rapidly synthesized by microwave-assisted solvothermal method using water and ethylene glycol as a mixed solvent. All synthesized photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), N₂ adsorption, photoluminescence (PL) spectra, and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic activities of the as-prepared Er³⁺-doped BiOI nanosheets were investigated by the photodegradation of Rhodamine B (RhB) dye in aqueous solution under visible light irradiation. The photodegradation results indicate the optimal doping of 1?mol.% Er³⁺ in BiOI nanosheets (doping content is from 0?mol.% to 4?mol.%) to be the most beneficial for photodegradation of RhB. 1Er-BiOI nanosheets also possesses good photocatalytic activity for representative anionic methyl orange (MO). From the scavenger testing results, the reactive species of holes (h⁺) and superoxide radical anions (O^2?) show major impacts on the photodegradation progress of RhB and MO dyes over 1Er-BiOI photocatalyst under visible light irradiation.