Thermodynamic and microstructural analyses of photocatalytic TiO2 from the anodization of biomedical-grade Ti6Al4V in phosphoric acid or sulfuric acid

TiO₂ coatings were fabricated by anodization of Ti6Al4V in 1 M H₃PO₄ or H₂SO₄, at room temperature at 120 V for 10 min, and followed by annealing at 300° or 500 °C for 8 h. Analyses include mineralogy (GAXRD, Raman), chemistry (XPS), morphology and microstructure (FESEM, FIB, 3D confocal microscopy), thermodynamic, optical (UV–Vis), and photocatalytic performance (MB degradation). The present work highlights factors that govern the nature of the materials and their performance. The influence of the oxidation strength of the acid is pervasive in that it impacts on the crystallinity, microstructural homogeneity, coating thickness, Ti³⁺ concentration, gas generation during arcing to form pores, and resultant pore size and distribution density. A key observation is that the pores form a subsurface network of variable continuity, which has a significant impact on the surface area and associated density of photocatalytically active sites, access by liquids and gases inside the coating, penetration depth of incident radiation, gas condensation, and residual liquid trapping. These data and the related thermodynamic analyses of the acids, anodization processes, and oxidation processes facilitate the generation of schematic models for the anodization mechanisms and the resultant surface, bulk, and microstructural effects that dominate the photocatalytic performance.     

Photothermal,photocatalytic, and anti-bacterial Ti-Ag-O nanoporous powders for interfacial solar driven water evaporation

Interfacial solar driven water evaporation is an attractive and green method to alleviate the scarcity of clean and fresh water, and tremendous efforts have been devoted to prepare efficient photothermal materials. However, the practical condition for interfacial solar driven water evaporation is complex, increasing contamination by pollutants and bacterial can inactive the photothermal materials. Herein, to address this problem, Ti-Ag-O nanoporous powders, which possess photothermal, photocatalytic and anti-bacterial properties, were prepared by TiAg alloy anodization and subsequent laser irradiation method. It was found that metallic Ag nanoparticles, which were mainly formed by TiAg alloy anodization, will be oxidized into Ag₂O nanoparticles after laser irradiation. Through this laser induced transformation, the surface wettability of Ti-Ag-O powders can be improved for the hydrophilicity nature of Ag₂O, and the Ti-Ag-O powders with Ti90Ag10 alloy anodization and subsequent laser irradiation for 10 min showed the highest water evaporation rate (2.27 kg m^?2 h^?1). Meanwhile, this Ti-Ag-O powders also showed the highest photocatalytic property due to the junction between TiO₂ and Ag₂O. Moreover, the diffusion inhibition test indicated that antibacterial property of this Ti-Ag-O powders was excellent for the incorporation of Ag/Ag₂O nanoparticles. The as-prepared trifunctional Ti-Ag-O nanoporous powders holds potential for the practical application of interfacial solar driven water evaporation technology, the TiAg alloy anodization and subsequent laser irradiation method could be extended to prepare other multifunctional photothermal materials.     

Stable and highly efficient natural sunlight driven photo-degradation of organic pollutants using hierarchical porous flower-like spinel nickel cobaltite nanoflakes

Hierarchical porous flower-like spinel nickel cobaltite (NiCo₂O₄) nanoflakes was synthesized by using simple and economical chemical method. The structure, morphology and optical properties of synthesizes nanoflakes were analyzed by using XRD, FE-SEM and UV–visible. The NiCo₂O₄ nanoflakes showed 96% degradation of TBO in 50 min and after 10 cycles of operation, the photocatalytic activity was enough for the 89% degradation of TBO under natural sun light. When compared with other photocatalysts materials, porous NiCo₂O₄nanoflakes showed excellent thermal and chemical stability and offer exceptional electron transfer rate during photocatalytic reactions for real environmental pollution cleanup applications. The efficient photocatalytic efficiency and stability of NiCo₂O₄ nanoflakes is attributed to its inimitable structure with large surface area along with maximum active sites. This augments the efficiency of harvesting sun light, and spread active species over surface to decrease e^-/h⁺ pair recombination. On the whole, this work demonstrates that the synthesis of nanoflower NiCo₂O₄ can be used as potential candidate to remove organic pollutant and infections from water under natural sun light irradiations for industrial applications.     

Preparation of graphene film decorated TiO2 nano-tube array photoelectrode and its enhanced visible light photocatalytic mechanism

Graphene film decorated TiO₂ nano-tube array (GF/TiO₂ NTA) photoelectrodes were prepared through anodization, followed by electrodeposition strategy. Morphologies and structures of the resulting GF/TiO₂ NTA samples were characterized by scanning electrons microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. In addition, the optical and photoelectrochemical properties were investigated through UV–visible light diffuse reflection spectroscopy, photocurrent response and Mott–Schottky analysis. Furthermore, the photodecomposition performances were investigated through yield of hydroxyl radicals and photocatalytic (PC) degradation of methyl blue (MB) under visible light irradiation. It was found that GF/TiO₂ NTA photoelectrode exhibited intense light absorption both in UV light and visible region, higher transient photoinduced current of 0.107 mA cm⁻² and charge carrier concentration of 0.84 × 10¹⁹ cm⁻³, as well as effective PC performance of 65.9% for the degradation of MB. Furthermore, contribution of several reactive species to the PC efficiency of GF/TiO₂ NTA photoelectrode was distinguished. Moreover, the enhanced visible light PC mechanism was proposed and confirmed in detail.     

The construction of TiO2 NTs/Ag3PO4–AgBr by SILAR deposition as promising photocatalysts for hydrogen production and pollutant treatment

The construction of ternary TiO₂ NTs/Ag₃PO₄–AgBr photocatalysts was carried out by the SILAR deposition of Ag₃PO₄ and AgBr on TiO₂ nanotube arrays (TiO₂ NTs) for enhancing the photocatalytic application in H₂ evolution and dyeing wastewater remediation. The adjustment of Ag₃PO₄/AgBr deposition cycles was used to optimize the optical absorption and photocatalytic property. The TiO₂ NTs/Ag₃PO₄–AgBr (5) prepared with 5 cycle deposition of Ag₃PO₄ and AgBr exhibited the optimal photoelectric activity and photocatalytic performances. The photocatalytic rate constants for the degradation of MO, RhB and MB dyes achieved 1.35 × 10⁻², 3.30 × 10⁻² and 4.47 × 10⁻² min⁻¹, respectively, and the visible light-driven photocatalytic H₂ evolution rate achieves 46.87 μmol cm⁻² h⁻¹. •O₂⁻ radicals exhibited the key influence on the organic dye degradation, and the as-prepared photocatalysts showed exceedingly high photocatalytic activity and stability. Furthermore, the photocatalytic mechanism was proposed based on the ESR result.     

Synthesis of Ni doped barium hexaferrite by microemulsion route to enhance the visible light-driven photocatalytic degradation of crystal violet dye

The pristine and Ni doped BaNi_xFe_12-xO₁₉ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) NPs have been fabricated via facile microemulsion approach and the impact of dopants was explored based dielectric, optical, structural and the photocatalytic properties of BaNi_xFe_12-xO₁₉ nanoparticles. X-ray diffraction and Raman study confirmed the formation of regular hexagonal geometry with space group P6₃/mmc with crystallite size in 32–50 nm range. Functional groups were identified using FTIR analysis. The remanence (Pr), saturation polarization (Ps) and coercivity (Hc) was explored by P-E loop analysis and the value of Pr and Ps was enhanced with the concentration of dopant. According to PL spectra, highly doped materials had a higher charge separation (e^?- h⁺) and low recombination rate, which resulted in higher photocatalytic degradation activity of fabricated nanomaterials. The optical band gap was found to be 1.78 eV versus undoped (2.60 eV for pristine BaFe₁₂O₁₉). Due to polarizations, the dielectric loss, dielectric constant and tangent loss values were declined, while AC conductivity was enhanced. Photocatalytic performance of doped and undoped samples under visible right irradiation was studied for crystal violet dye. For 100 min exposure to visible light, the highly doped catalyst exhibits 97% degradation versus 60% in case of pristine this is attributed to efficient electron-hole pair separation. Furthermore, quenching effect of different scavengers indicated that hydroxyl radical had a main role, and e^? or h⁺ played a minimal role in CV dye degradation. The enhanced properties due to doping make BaNi_xFe_12-xO₁₉ a potential candidate for photocatalytic applications under visible light irradiation.     

Mn-modified HfO2 nanoparticles with enhanced photocatalytic activity

Round shaped Mn-modified HfO₂ nanoparticles were prepared by the Pechini type sol-gel method. The effects of Mn ions on the structure, particle growth, composition, optical properties and photocatalytic performance of HfO₂ particles were investigated. The structure analysis revealed that the insertion of Mn²⁺, Mn³⁺, and Mn⁴⁺ ions inhibited the complete stabilization of tetragonal HfO₂. Also, the decrease of particle size to values lower than 5 nm and the shift of optical band gap from 5.7 to 2.1 eV was obtained as effect of increasing the Mn content. HfO₂ nanoparticles modified with 10 w% Mn exhibited the highest photocatalytic performance, reaching an efficiency of 91.93% in the decomposition of methylene blue, after 120 min of sunlight irradiation. The efficient trapping of photogenerated electrons on the surface of these nanoparticles generated •O₂⁻ radicals, which were the main oxidative species involved in the degradation of the dye. The improved photocatalytic performance of these nanoparticles is then attributable to their increased surface area, suitable photoactivation, and effective transport of photoexcited charge carriers. Based in studies of band gap, valence band position and active species, a mechanism of photodegradation for this photocatalyst was also proposed and discussed.     

A novel Ni doped BaTiO3/h-BN nanocomposite for visible light assisted enhanced photocatalytic degradation of textile effluent and phytotoxicity evaluation

The objective of this research is to synthesize novel Ni–BaTiO₃/h-BN nanocomposites. XRD, UV–Vis, PL, FT-IR, SEM, TEM, Zeta potential, XPS, BET, EIS, Mott- Schottky and LC-MS analyses were used to analyze the nanocomposite phase structure, band gap, electron-hole recombination rate, vibrational modes, morphology, elemental analysis stability, oxidation state, pore size distribution, and electron distribution. The nanocomposites have an average particle size of 32 nm, as measured using HR-TEM microscopy. The band gap of synthesized h-BN was found to be 3.82 eV, whereas the Ni–BaTiO₃/h-BN binary nanocomposite shifts it to 2.43 eV. The nanocomposite photocatalytic efficiency was used to degrade textile effluent, followed by a phytotoxicity assessment of real textile effluent. Furthermore, the photocatalytic treatment analysis revealed that the 40 mg Ni–BaTiO₃/h-BN catalyst degraded up to 81.4% and 86% against textile effluent and crystal violet (CV) dye within 120 min under visible light, respectively, and the concentrations of numerous Physico-chemical parameters of textile effluent have significantly decreased in deteriorated textile effluent. According to a pot study, the toxicity of the degraded textile effluent was reduced following photocatalytic treatment. To examine the mechanism, the photodegradation effectiveness of the catalyst was investigated utilizing various scavengers. From the scavenger study, it is found that the holes (h⁺) contribute more to the degradation process. In real textile dye wastewater, the Ni–BaTiO₃/h-BN nanocatalyst was proved to be an excellent and low-cost degrading technique.     

Structural,optical and photocatalytic properties of ZnO nanorods: Effect of aging time and number of layers

ZnO thin films were prepared by sol–gel dip coating method onto glass substrates. The effects of aging time of the starting solution (2, 10 and 30 days) and the number of coats (2, 5 and 10 coatings) on structural, morphological and optical properties were investigated. Photocatalytic efficiency was also assessed. X-ray diffraction analysis indicates that all the films exhibit a Zincite-type structure with a preferred grains orientation along the [002] direction. The preferred orientation factor (POF) increases with aging time while the crystallite size decreases. The field emission scanning electron microscopy observations reveals nanorods morphology. The length of ZnO nanorods increase with increasing number of layers whereas their length decreases as a function of aging time while adopting a random orientation. A high optical transparency is observed for all ZnO thin films, ranging from 90 up to 96%. Methylene Blue (MB) dye photocatalytic degradation was found increases with aging time, reaching almost 94% after 10 h under UV irradiation. The apparent reaction rate (K_app) obtained by Langmuir-Hinshelwood model increases with increasing aging time from, from 0.218 h⁻¹ for 2 days to reach a steady state around 0.270 h⁻¹. Nevertheless, a small variation of K_app was recorded when varying the number of coats; 0.223–0.226 h⁻¹.     

Solvothermal synthesis and characterizations of graphene-ZnBi12O20 nanocomposites for visible-light driven photocatalytic applications

The Bismuth based Zinc metal oxide (ZnBi₁₂O₂₀) nanorods were synthesized via single step solvothermal approach. The characterization of synthesized hybridized structure was done by several analysis such as X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UVvis–DRS), Fourier transform-infrared spectroscopy (FT–IR), Thermogravimetric analysis (TGA), Raman spectroscopy, Field-Emission scanning electron microscopy (FESEM), Energy dispersive analysis of X-rays (EDX), High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy. The photocatalytic activity of ZnBi₁₂O₂₀ and an incorporation of varying weight percentages of GO (1–4 wt %) into ZnBi₁₂O₂₀ catalyst (GZBC) were analyzed under visible light irradiation by the degradation of an aqueous solution of Methylene blue (MB) and Methyl orange (MO) dye. Among various developed nanocomposites, 3 wt% GZBC reduced graphene oxide exfoliated nanocomposites has revealed the degradation efficiency as 96.04, 94.52% at 100 and 120 min for MB and MO respectively with enriched visible light absorption range. The photocatalytic property of 3 wt % reduced graphene oxide exhibits higher degradation behavior than that of other synthesized nano-composites.     

Cu2O/TiO2 heterostructure nanotube arrays prepared by an electrodeposition method exhibiting enhanced photocatalytic activity for CO2 reduction to methanol

Cu₂O/TiO₂ composite nanotube arrays demonstrating enhanced photocatalytic performance were synthesized using an electrodeposition method to impregnate the p-type Cu₂O into the n-type titanium dioxide nanotube arrays (TNTs). The morphological results confirmed that the TNTs are wrapped by the Cu₂O nanoparticles and the UV–Vis absorption spectra showed that the Cu₂O/TNTs display a better ability for visible light absorption compared to the pure TNTs. CO₂ photocatalytic reduction experiments carried out by using Cu₂O/TNT nanocomposites proved that Cu₂O/TNTs exhibit high photocatalytic activity in conversion of CO₂ to methanol, while pure TNT arrays were almost inactive. Furthermore, Cu₂O/TNTs also exhibited augmented activity in degradation of target organic pollutant like acid orange (AO) under visible light irradiation. The ultra enhanced photocatalytic activity noticed by using Cu₂O/TNTs in CO₂ reduction and degradation of organic pollutant could be attributed to the formation of Cu₂O/TiO₂ heterostructures with higher charge separation efficiency.     

Construction of CaTiO3 nanosheets with boron nitride quantum dots as effective photogenerated hole extractor for boosting photocatalytic performance under simulated sunlight

Herein, titanate-based perovskite CaTiO₃ nanosheets were successfully designed via boron nitride quantum dots (BNQDs) to fabricate CaTiO₃/BNQDs catalyst. The as-fabricated composite catalysts were analysed by transmission electron microscope (TEM), scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), X-ray diffraction (XRD), UV–vis spectroscopy (UV-DRS), photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) techniques. SEM-Mapping analysis showed that the boron and nitrogen elements dispersed well over the CaTiO₃ surface which was useful for building electronic channels for rapid transport of photo-induced charge pairs. TEM images verified the attachment of BNQDs around the surface of host CaTiO₃ forming intimate interface while the distribution of chemical states was observed by XPS analysis demonstrating strong coupling effect between BNQDs and CaTiO₃ through Ti–O–N and Ti–O–B bonds. Moreover, PL and light absorption properties enhanced with the quantum confinement effect of BNQDs. As expected, the photocatalytic degradation rate of CaTiO₃/BNQDs was increased to k_app = 0.015 min^{? 1} with optimum BNQDs loading, which was 2.31 times folder than that of bare CaTiO₃ (0.006 min^{? 1}). The enhanced photocatalytic efficiency was observed for CaTiO₃/BNQDs than pristine perovskite on account of formation of electron tapping sites, decreased band gap energy and hindered recombination rate. On the other hand, in the presence of H₂O₂, the degradation percentage increased from 88.5% to 92.1% at the end of 120 min of irradiation while 96.8% of TC was quickly degraded within 60 min after activating with peroxymonosulfate which created strong sulphate radicals. Radical trapping tests indicated that the photo-generated holes were the primary active species in the photocatalytic mechanism. Moreover, CaTiO₃/BNQDs catalyst showed excellent stability in recycling tests. Besides, the possible degradation mechanism was proposed. This study shed light on the significance of BNQDs in the enhancement of the photocatalytic activities of titanate-based perovskite for effective degradation of tetracycline antibiotic in contaminated water.     

Nano Ca–Mg–Zn ferrites as tuneable photocatalyst for UV light-induced degradation of rhodamine B dye and antimicrobial behavior for water purification

We report the synthesis of Ca-doped Mg–Zn ferrite Mg_0.4Zn_(0.6-x)Ca_xFe₂O₄ nanomaterials with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 through citrate precursor approach and their structural, morphological, optical, photocatalytic, and antimicrobial properties were systematically studied. The prepared nanoferrites's cubic spinel structure with an average crystallite size of 15–38 nm was evaluated by the XRD examination. The spherical morphology of these ferrite nanoparticles was seen from scanning electron microscopy (SEM). The observed bands at 560 cm⁻¹ and 406 cm⁻¹ in the FTIR spectra confirmed the spinel structure of the synthesized nanoferrite. The optical study confirmed an optical band gap of 1.60 eV–1.86 eV. The photocatalysis was done for the degradation of rhodamine B dye solution under UV light. All the synthesized nano ferrites displayed a promising antimicrobial potential upon Candida albicans fungi. Mg_0.4Zn_0.1Ca_0.5Fe₂O₄ nanoparticles have a better photocatalytic response (99.5%) for the degradation of rhodamine B dye and show superior antimicrobial activity (96.1%) for the inhibition of Candida albicans fungi.     

Ultrasound assisted sol-gel TiO2 powders and thin films for photocatalytic removal of toxic pollutants

The paper presents a study on the structural, surface and photocatalytic properties of the ultrasound assisted sol-gel titanium dioxide particles, as part of stable photocatalytic ink formulations deposited on fabrics. The photocatalytic activity was validated using methylene blue as reference pollutant, under UV, VIS and combined UV+VIS radiation and allowed selecting the optimum TiO₂ samples for inks preparation. To minimize the particles agglomeration stabilizing agents were added and the stability was quantitatively evaluated considering the relative increase in the VIS transmittance for a pre-set period of 30 min. Further on, the ink(s) were deposited by cold spraying on cotton woven fabrics and a removal efficiency higher than 95% was observed in the degradation of the highly toxic mustard gas, after 30 min of UV irradiation.     

Facile synthesis of Cu<Subscript>x</Subscript>O (x = 1, 2)/TiO<Subscript>2</Subscript> nanotube arrays as an efficient visible-light driven photocatalysts

TiO₂ nanotube arrays (TNTs) modified with Cu_xO (x = 1, 2) were prepared by a simple impregnation-calcinations method. The obtained samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy , UV–Vis diffuse reflectance spectroscopy and photocurrent tests. The photocatalytic ability of the as-prepared photocatalysts was evaluated using rhodamine B (RhB) as a target pollutant. Compared with pure TNTs, the Cu_xO/TNTs composite exhibited much higher photocatalytic activity under visible-light irradiation (λ > 420 nm). The photocatalytic activity of the composite was related to impregnation time of the copper nitrate solution, and an optimal time was 2 h. The activity of 2-Cu_xO/TNTs displayed 4.9 times as high as that of pure TNTs. The enhanced photocatalytic performance is mainly attributed to the synergistic effects of initiating visible-light absorption and the matched band edge positions of Cu₂O, CuO and TiO₂. Also, a possible mechanism on the Cu_xO/TNTs photocatalytic degradation of RhB is proposed. Overall, the inexpensive and environmentally friendly photocatalyst, as promising materials, could be used to remove some aquatic pollutants in the field of water purification.     

Spinel nickel cobaltite nanoflakes anchored multiwalled carbon nanotubes driven photocatalyst for highly efficient degradation of organic pollutants using natural sunlight irradiation

Natural sun light driven photocatalytic materials have received remarkable attention due to their imminent applications in environmental remediation and energy conversions. In this study, natural sun light driven hierarchal spinel nickel cobaltite nanoflakes (NiCo₂O₄) anchored multiwalled carbon nanotubes (MWCNTs) nanocomposite was synthesized by using simple chemical route. The structural, morphological and functional group of as-prepared NiCo₂O₄ anchored MWCNTs was studied by using X-ray diffractometry, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The UV–vis diffusive reflectance spectroscopy results demonstrated decrease in optical bandgap from 1.32 to 1.16eV compared with pristine spinel NiCo₂O₄ nanoflakes. MWCNTs anchored NiCo₂O₄ showed extremely good photocatalytic behavior and we verified 98% degradation of MB in 35 min under natural sun light. NiCo₂O₄ anchored MWCNTs also confirmed its excellent stability and reusability by retaining 96% of photocatalytic efficiency after 7 cycles of operation. Improved photocatalytic behavior of NiCo₂O₄ anchored MWCNTs nanocomposite in comparison to NiCo₂O₄ nanoflakes is mainly attributed to excellent electron storage ability of MWCNTs which made catalyst a great acceptor. Moreover, porous structure of MWCNTs not only provides large surface area with more active sites but also increases conductivity and decreases agglomerations on the surface of material which render e^-/h⁺ pair recombination. Overall, this work shed new light for the synthesis of NiCo₂O₄ anchored MWCNTs with enhanced photocatalytic properties.     

Efficient sunlight and UV photocatalytic degradation of Methyl Orange,Methylene Blue and Rhodamine B,using Citrus×paradisi synthesized SnO2 semiconductor nanoparticles

In this work, tin dioxide (SnO2) Nanoparticles (NPs) were synthesized through green synthesis, using Citrus × paradisi extract as a stabilizing (capping). The extract concentrations used were 1, 2 and 4% in relation to the aqueous solution. The resulting SnO2 NPs were used for the degradation of Methyl Orange (MO), Methylene Blue (MB) and Rhodamine B (RhB), under both solar and UV radiation. The NPs were characterized via Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM-SAED), the Brunauer-Emmett-Teller (BET) theory, Ultraviolet to Visible spectroscopy (UV–Vis), and Photoluminescence spectroscopy (PL); while the photocatalytic degradation was evaluated using UV-VIS. The results showed that the Citrus × paradisi extract is a good medium for the formation of SnO2 NPs. These NPs presented quasi-spherical morphology, particle sizes of 4–8 nm, with a rutile phase crystalline structure, and with banned gap of 2.69 at 3.28 eV. The NPs had excellent photocatalytic properties under solar radiation, degrading 100% of the OM in 180 min. Furthermore, under UV radiation, 100% degradation of the three dyes was achieved in a short time; 20 min for MO, and 60 min for MB and RhB. Therefore, green synthesis is a feasible medium for the formation of SnO2 NPs with good photocatalytic properties.     

Synthesis of sponge like Gd3+ doped vanadium oxide/2D MXene composites for improved degradation of industrial effluents and pathogens

Current report is based on the synthesis of Gd⁺³ doped V₂O₅ nanostructures (GVO) along with fabrication of GVO/MXene binary nanocomposite. As synthesized GVO and GVO/MXene were characterized by XRD (X-ray diffraction), FESEM (Field emission scanning electron microscopy), EDX (Energy dispersive X-ray), BET (Brunauer Emmett Teller technique) and UV–Visible spectroscopy. Diffraction and elemental analysis confirmed the substitution of Gd⁺³ ions in VO layers. Orthorhombic phase of VO was observed in both GVO and GVO/MXene samples with crystallite size range of 17.02–17.51 nm. FESEM analysis indicated asymmetrical VO particles and sheets distributed on MXene layers, giving out a sponge like appearance. Surface area of GVO and GVO/MXene was enhanced to 20.46 and 23.69 nm, respectively. Effect of Gd⁺³ contents was significant on optical properties, which reduced the band gap energy of VO to 2.33 eV. The photocatalytic performance of prepared samples was analysed by the degradation of Methylene blue (MB) under direct sunlight. Gd⁺³ ion doping was found useful to enhance degradation of MB up to ～71%. Among all samples, GVO/MXene showed maximum degradation (～92%) within 120 min. Meanwhile, GVO/MXene showed good recyclability for successive five cycles. In addition, GVO and GVO/MXene were effective antibacterial agents against Gram positive (S. aureus) and Gram negative (P. vulgaris) strains of bacteria. The results suggested that the GVO and GVO/MXene could serve as potential candidates for large scale treatment of organic pollutants and pathogens.     

Comparison of two synthesis methods on the preparation of Fe,N-Co-doped TiO2 materials for degradation of pharmaceutical compounds under visible light

In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe³⁺-TiO_2−xN_x) nanostructured catalyst. Fe³⁺-TiO_2−xN_x was synthesized using two different chemical approaches: sol-gel (SG) and microwave (MW) methods. The materials were fully characterized using several techniques (SEM, UV–Vis diffuse reflectance DRS, X-ray diffraction XRD, and X-ray photoelectron spectroscopy XPS). The photocatalytic activity of the nanostructured materials synthesized by both methods was evaluated for the degradation of amoxicillin (AMX), streptomycin (STR) and diclofenac (DCF) in aqueous solution. Higher degradation efficiencies were encountered for the materials synthesized by the SG method, for instance, degradation efficiencies values of 58.61% (SG) and 46.12% (MW) were observed for AMX after 240 min of photocatalytic treatment under visible light at pH 3.5. With STR the following results removal efficiencies were obtained: 49.67% (SG) and 39.90% (MW) at pH 8. It was observed the increasing of degradation efficiencies values at longer treatment periods, i.e., after 300 min of photocatalytic treatment under visible light, AMX had a degradation efficiency value of 69.15% (MW) at pH 3.5, DCF 72.3% (MW) at pH 5, and STR 58.49% (MW) at pH 8.     

In situ synthesis of Bi2O3/Bi2MoO6 heterostructured microspheres for efficiently removal of acid orange 7

Flower-like Bi₂O₃/Bi₂MoO₆ heterostructured microspheres with excellent photocatalytic performance were successfully constructed by in situ ion exchange and calcination, employing Bi₂MoO₆ microspheres prepared by solvothermal method as raw material and template. Various characterization techniques including XRD, FE-SEM, EDS, UV–vis DRS and XPS have been adopted to analyze the composition, structure and optical absorption property of the obtained sample. Their photocatalytic properties for degrading acid orange 7 (AO7) were investigated with visible light. Experimental results show that all Bi₂O₃/Bi₂MoO₆ composites have a higher catalytic activities than pure Bi₂MoO₆. Remarkably, 0.2Bi₂O₃/Bi₂MoO₆ show best activity and the degradation efficiency is up to 99% under visible light for 100?min, which is ascribed to the synergistic effect and big heterojunction interface, and promoting rapid transmission of photogenerated charge. Moreover, There is negligible reduction on the degradation efficiency after catalysts was reused for 4 times. The photogenerated holes (h⁺) and superoxide radical anions (?O₂^-) were major active species by radical scavenger experiments. A possible mechanism is proposed to explain rationally enhancement of photocatalytic activity.