Enhanced photocatalytic performance of carbon quantum dots/BiOBr composite and mechanism investigation

Novel CQDs/BiOBr composite photocatalysts are constructed via a simple hydrothermal synthesis and show superior activity in photocatalytic degradation of organic pollutants.     

Novel organic/inorganic PDI-Urea/BiOBr S-scheme heterojunction for improved photocatalytic antibiotic degradation and H2O2 production

The matched energy band structure and efficient carrier separation efficiency are the keys to heterogeneous photocatalytic reactions. A novel organic/inorganic step scheme (S-scheme) heterojunction PDI-Urea/BiOBr composite photocatalyst was constructed by simple solvothermal reaction combined with in-situ growth strategy. The composite photocatalyst not only has high chemical stability, but also can generate and accumulate a large number of active species (h⁺, ^?O₂^?, ^?OH, H₂O₂). PDI-Urea/BiOBr showed higher photocatalytic activity for the degradation of antibiotic such as ofloxacin (OFLO), tetracycline (TC) and the production of H₂O₂ in the spectral range of 400–800 nm. The apparent rate constant of 15% PDI-Urea/BiOBr for photocatalytic degradation of TC (or OFLO) was 2.7 (or 2.5) times that of pure BiOBr and 1.7 (or 1.8) times that of pure PDI-Urea. The H₂O₂ evolution rate of 15% PDI-Urea/BiOBr was 2.5 times that of PDI-Urea and 1.5 times that of BiOBr, respectively. This work has formed a mature S-scheme heterojunction design thought and method, which offers new visions for the development of heterogeneous photocatalysts.     

Facile synthesis of GO as middle carrier modified flower-like BiOBr and C3N4 nanosheets for simultaneous treatment of chromium(VI) and tetracycline

A novel GO modified g-C₃N₄ nanosheets/flower-like BiOBr hybrid photocatalyst is fabricated by a facile method. The characterization results reveal that wrinkled GO is deposited between g-C₃N₄ nanosheets and flower-like BiOBr forming a Z-scheme heterojunction. As a mediator, plicate GO plays a positive role in prompting photogenerated electrons transferring through its sizeable 2D/2D contact surface area. The g-C₃N₄/GO/BiOBr hybrid displays a superior photocatalytic ability to g-C₃N₄ and BiOBr in photodegrading tetracycline (TC), whose removal efficiency could reach 96% within 2 h. Besides, g-C₃N₄/GO/BiOBr composite can reduce Cr(VI), and simultaneously treat TC and Cr(VI) combination contaminant under the visible light. The g-C₃N₄/GO/BiOBr ternary composite also exhibits satisfactory stability and reusability after four cycling experiments. Further, a feasible mechanism related to the photocatalytic process of g-C₃N₄/GO/BiOBr is put forward. This study offers a ternary hybrid photocatalyst with eco-friendliness and hopeful application in water pollution.     

Photocatalytic degradation of acid blue 74 in water using Ag–Ag2O–Zno nanostuctures anchored on graphene oxide

Water pollution due to industrial effluents from industries which utilize dyes in the manufacturing of their products has serious implications on aquatic lives and the general environment. Thus, there is need for the removal of dyes from wastewater before being discharged into the environment. In this study, a nanocomposite consisting of silver, silver oxide (Ag₂O), zinc oxide (ZnO) and graphene oxide (GO) was synthesized, characterized and photocatalytically applied in the degradation (and possibly mineralization) of organic pollutants in water treatment process. The Ag–Ag₂O–ZnO nanostructure was synthesized by a co-precipitation method and calcined at 400 °C. It was functionalized using 3-aminopropyl triethoxysilane and further anchored on carboxylated graphene oxide via the formation of an amide bond to give the Ag–Ag₂O–ZnO/GO nanocomposite. The prepared nanocomposite was characterized by UV–Vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), energy dispersive X-ray spectrometry (EDX), Fourier transformed infrared spectroscopy (FTIR), and Raman spectroscopy. The applicability of Ag–Ag₂O–ZnO/GO nanocomposite as a photocatalyst was investigated in the photocatalytic degradation of acid blue 74 dye under visible light irradiation in synthetic wastewater containing the dye. The results indicated that Ag–Ag₂O–ZnO/GO nanocomposite has a higher photocatalytic activity (90% removal) compared to Ag–Ag₂O–ZnO (85% removal) and ZnO (75% removal) respectively and thus lends itself to application in water treatment, where the removal of organics is very important.     

Comparative evaluation of antibacterial potentials of nano cobalt oxide with standard antimicrobials

Development of suitable potent antimicrobial is the urgent need of modern era to cope up the problem of antimicrobial resistance. The applications of nanotechnology in metal oxides have shown favorable effects to some extent in this area. Thus, the present study was investigated to evaluate the antibacterial properties of cobalt oxide (Co₃O₄) nanoparticles at different concentrations and their comparison with standard antimicrobials i.e. tetracycline and gentamicin. Nanoparticles were synthesized and characterized by standard techniques. The antibacterial potentials of Co₃O₄ nanoparticles against S. aureus and E. coli were determined at various concentrations. The maximum zone of inhibitions of Co₃O₄ nanoparticles against S. aureus and E. coli at 500 μg/ml were 21.17 mm and 24.00 mm, respectively. The Co₃O₄ nanoparticles seemed more effective than gentamicin against S. aureus and E. coli. The nanoparticles with respect to tetracycline showed higher than 1 activity index at ≥ 125 μg/ml for E. coli and ≥31.25 μg/ml for S. aureus. It was also higher than 1 at all compared concentrations with respect to gentamicin against both bacteria. In conclusion, Co₃O₄ nanoparticles seemed to have potent antibacterial potential and these might be very helpful to replace the conventional antimicrobials to solve the problem of antibacterial resistance.     

Quantum-chemical study of the effect of oxygen on the formation of active sites of silver clusters during the selective adsorption of hydrocarbons

Density functional theory (PBE with a modified Dirac-Coulomb-Breit Hamiltonian) is used to simulate the adsorption of hydrocarbons (C₂H₂, C₂H₄, C₂H₆) on the surface of a sorbent containing Ag⁰, Ag^δ+, and AgO sites. The dynamics of change in the structural characteristics of Ag _n (n ≤ 10) is analyzed and the adsorption of oxygen on Ag₈ and Ag₁₀ is studied to select the adsorption site model. Studying the interaction of hydrocarbons with Ag₈, Ag₁₀, Ag ₁₀ ⁺ , Ag₁₀O, and Ag₁₀O₂ clusters reveals that the presence of oxygen leads to an increase in the activation of unsaturated hydrocarbons, and the adsorption energy of C₂H₂ increases tenfold. It is found that the role of adsorbed oxygen is not only to form adsorption sites of hydrocarbons (Ag^δ+) but also to bind C₂H₂ and C₂H₄ directly to the sorbent’s surface.     

Tetracycline Removal Under Solar Illumination Over Ag3VO4/mpg‐C3N4 Heterojunction Photocatalysts

Ag₃VO₄/mpg‐C₃N₄ (mesoporous graphitic carbon nitride) heterojunction photocatalysts were prepared by anchoring tiny Ag₃VO₄ particles on the nanosheet of mpg‐C₃N₄. The prepared Ag₃VO₄/mpg‐C₃N₄ heterojunctions were used to remove tetracycline (TC), a kind of antibiotics widely released into the aquatic environment under solar irradiation. Compared with pure mpg‐C₃N₄ and Ag₃VO₄, Ag₃VO₄/mpg‐C₃N₄ displayed much higher photocatalytic activity (83.2% removal rate within 90 min under visible‐light irradiation). Importantly, no apparent deactivation was observed for Ag₃VO₄/mpg‐C₃N₄‐40 after five cycles, inferring a good reusability. As confirmed by photocurrent measurement and photoluminescence spectra, the excellent photocatalytic property of Ag₃VO₄/mpg‐C₃N₄ was credit to the electron–hole separation enhancement at the formed heterojunction of two semiconductors. In addition, a possible mechanism and intermediate products for the Ag₃VO₄/mpg‐C₃N₄ photocatalysts toward the photodegradation of TC in aqueous solution under artificial sunlight radiation were proposed based on the scavengers trapping test, ESR spectra and a high‐performance liquid chromatography (HPLC) coupled with mass spectrometer (MS) analysis. This investigation provides a low cost, green and easily practical approach to remove the antibiotics in the aquatic environment.     

ZnO修饰提升花状BiOBr的可见光催化降解罗丹明B性能

以Bi(NO3)3·5H2O、Zn(CH3COO)2·2H2O和NaBr为前驱体,采用简单溶剂热法制备BiOBr/ZnO三维花状微纳米复合材料.采用X射线衍射、扫描电子显微镜、X射线光子能谱、N2吸附-脱附、光致发光和电子顺磁共振等分析技术对其理化性质进行了表征.通过可见光催化降解罗丹明B(RhB)的实验测试了复合材料...     

Synthesis and antibacterial activity of new layered perovskite compounds, AgxNa2-xLa2Ti3O10

Three kinds of new layered perovskite compounds with Ruddlesden-Popper(R-P)phase,Ag_xNa_(2-x)La_2Ti_3O_(10)(x=0.2,0.3 and 0.5),were synthesized by an ion-exchange reaction of Na_2La_2Ti_3O_(10)with AgNO_3 solution.The structures of the compounds were characterized by EDX and XRD,and their antibacterial activity and light-resistance property were evaluated.The results indicated that the molecular formula of Ag_xNa_(2-x)La_2Ti_3O_(10)(x=0.2,0.3 and 0.5)was confirmed,and that the crystalline structure of Na_2La_2Ti_3O_(10)was not obviously affected by exchange of silver ion.The minimum inhibitory concentrations(MICs)of Ag_(0.3)Na_(1.7)La_2Ti_3O_(10)against Escherichia coli(E.coli),Staphylococcus aureus(S.aureus)were 180μg/mL and 240μg/mL, respectively,while its discoloration was not observed after 24 h light ageing test.     

Ternary BiOBr/TiO2/Ti3C2Tx MXene nanocomposites with heterojunction structure and improved photocatalysis performance

The rational design and construction of heterojunction structure is an effective strategy to improve the photocatalytic performance. Herein, a series of BiOBr nanosheets-immobilized TiO₂/Ti₃C₂T_x MXene hybrid materials with heterojunction structure were synthesized by a facial one-step hydrothermal method. The ternary composites show outstanding performance as photocatalysts for the degradation of rhodamine B due to the optimized synergetic effects of BiOBr, TiO₂ and Ti₃C₂T_x. The improved photocatalytic performance is remarkably attributed to the construction of a heterojunction between TiO₂ and BiOBr due to their well-matching of energy band position, which can enhance the absorption for visible light and promote the transfer of photo-generated charge carriers. Moreover, Ti₃C₂T_x acts as an electron trap to further accelerate the separation of photo-generated electrons and holes.     

Preparation of Z-scheme WO3(H2O)0.333/Ag3PO4 composites with enhanced photocatalytic activity and durability

Ag₃PO₄ is widely used in the field of photocatalysis because of its unique activity. However, photocorrosion limits its practical application. Therefore, it is very urgent to find a solution to improve the light corrosion resistance of Ag₃PO₄. Herein, the Z-scheme WO₃(H₂O)_0.333/Ag₃PO₄ composites are successfully prepared through microwave hydrothermal and simple stirring. The WO₃(H₂O)_0.333/Ag₃PO₄ composites are characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-Vis spectroscopy. In the degradation of organic pollutants, WO₃(H₂O)_0.333/Ag₃PO₄ composites exhibit excellent performance under visible light. This is mainly attributed to the synergy of WO₃(H₂O)_0.333 and Ag₃PO₄. Especially, the photocatalytic activity of 15%WO₃(H₂O)_0.333/Ag₃PO₄ is the highest, and the methylene blue can be completely degraded in 4 min. In addition, the stability of the composites is also greatly enhanced. After five cycles of testing, the photocatalytic activity of 15%WO₃(H₂O)_0.333/Ag₃PO₄ is not obviously decreased. However, the degradation efficiency of Ag₃PO₄ was only 20.2%. This indicates that adding WO₃(H₂O)_0.333 can significantly improve the photoetching resistance of Ag₃PO₄. Finally, Z-scheme photocatalytic mechanism is investigated.     

Use of metal composite MOF‐5‐Ag2O‐NPs as an adsorbent for the removal of Auramine O dye under ultrasound energy conditions

In this work, MOF‐5 composited with Ag₂O nanoparticles was prepared and characterized via X‐ray diffraction, field emission‐scanning electron microscopy, energy‐dispersive spectroscopy and FT‐IR analysis. This new material was subsequently employed for removing basic yellow dye [Auramine O (AO)] from aqueous solution under ultrasound irradiation. Several experiments were designed by central composite design in which operational parameters such as such as pH, MOF‐5‐Ag₂O mass and initial concentration of AO involved in the process were optimized. The significance of individual parameters and their possible interactions were investigated using analysis of variance (anova ). The optimum values of 6, 0.025 g and 6 mg l^?1 were obtained for the pH, MOF‐5‐Ag₂O‐NPs mass and the initial concentrations of AO, respectively, with desirability of 1.0. At such conditions, the efficiency for the removal of AO was found to be 89.45%. Various isotherm models for fitting the experimental equilibrium data were studied, and it was found that the Langmuir model has the highest efficiency for correlation of experimental equilibrium data, so that the monolayer adsorption capacity of MOF‐5‐Ag₂O for successful removal of AO was 260.70 mg g^?1 at optimal conditions.     

Efficient solar photocatalyst based on Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>/graphene nanosheets composite for photocatalytic decolorization of dye pollutants

Silver orthophosphate-graphene nanosheets composite (Ag₃PO₄-GNs) has been fabricated using a facile hydrothermal method. The Ag₃PO₄-GNs were characterized using XRD, UV–vis DRS and SEM. The photocatalytic activity of Ag₃PO₄-GNs was evaluated by photocatalytic decolorization of dye aqueous solutions under simulated solar light irradiation. It was observed that Ag₃PO₄ nanoparticles in Ag₃PO₄-GNs were attached on the surface of graphene nanosheets.The introduction of graphene nanosheets enhanced remarkably the visible light absorption region of Ag₃PO₄-GNs compared with bare Ag₃PO₄. The photocatalytic activity of Ag₃PO₄-GNs is nearly twice as high as that of the pure Ag₃PO₄. The removal efficiency can reach more than 90 % by Ag₃PO₄-GNs under simulated solar light irradiation within 25 min, which might mainly be attributed to high adsorption capacity, extended light absorption range and efficient charge separation. After irradiation for 60 min, 84.70 % TOC mineralization was achieved by Ag₃PO₄-GNs. Based on the results of detection of active species, the direct oxidization of dye pollutants in aqueous solution by holes takes a major role in the whole decolorization process by Ag₃PO₄-GNs. As a result, Ag₃PO₄-GNs with the high photocatalytic activity are proven to be an excellent light photocatalyst for potentially scalable removal of dyes in aqueous solutions and other environmental remediation under simulated solar light irradiation.     

Synthesis, crystal structures and antibacterial activities of schiff base ligand and its cobalt(II) complex

The Schiff base ligand, HL · 0.5C₂H₅OH (HL = methyl N-[(4-chlorophenyl)(3-methyl-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-4-ylindene)methyl]valine), was derived from condensation of 1-phenyl-3-methyl-4-(p-chlorbenzyl)-5-pyrazolone with L-valine methyl ester in a 1: 1 molar ratio in methanol, ether and isopropanol solution. Reaction of ligand with Co(ClO₄)₂ · 6H₂O (in a 2: 1 molar ratio) in methanol solution afforded a mononuclear cobalt(II) complex, [Co(L)₂] (I). Molecular structures of HL · 0.5C₂H₅OH and complex I were characterized by elemental analysis, IR and single crystal X-ray diffraction analysis. The enamine-keto form of the ligand has turned to imine form in complex I. Each Co(II) center in complex I is in a octahedral N₂O₄ coordination sphere. Both the Schiff base ligand and its Co(II) complex have been tested in vitro with agar dilution method to evaluate their antibacterial activity against bacteria Escherichia coli and Staphylococcus aureus. It has been found that they have higher activity against Escherichia coli than Staphylococcus aureus, and complex I has higher activity than HL · 0.5C₂H₅OH against the same bacteria.     

Virus and bacterial removal ability of TiO2 nanowire-based self-supported hybrid membranes

Development and application of hybrid membranes containing multi-component materials are increasing day by day in the fields of environmental protection and water treatment. In this research, the efficiency of titania nanowire (TiO₂ NW)-based self-supported hybrid membranes was investigated in the removal of Escherichia coli (E. coli) bacteria and MS2 bacteriophages from contaminated water mimicking the microorganism suspension. Furthermore, toxicology tests on the as-prepared membranes were also performed. TiO₂ NWs were coated with iron(III) oxide (Fe₂O₃) and copper(II) oxide (CuO) nanoparticles, respectively, and cellulose was used as reinforcement material. It was found that, the functionalisation strongly affected the MS2 removal ability of as-prepared membranes, which can be due to the electrostatic interactions between the surface of hybrid membrane and the bacteriophages. The most efficient removal (greater than or equal to 99.99%) was obtained with the TiO₂ NW-CuO-cellulose membrane at pH 7.0. The fabricated hybrid membranes were characterized by micro computed tomography (μCT), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), contact angle measurement and inductively coupled optical emission spectrometry (ICP-OES) techniques. This study shows a simple route of the usage of novel and effective inorganic nanowire-based hybrid membranes for bacteria and virus removal, providing new pathways in the field of water filtration technologies.     

Novel Bi/BiOBr/AgBr composite microspheres: Ion exchange synthesis and photocatalytic performance

Novel Bi/BiOBr/AgBr composite microspheres were prepared by a rational in situ ion exchange reaction between Bi/BiOBr microspheres and AgNO₃. The characteristic of the as-obtained ternary microspheres was tested by X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL). Under visible light irradiation, Bi/BiOBr/AgBr microspheres exhibited an excellent photocatalytic efficiency for rhodamine B (RhB) degradation, which was about 1.4 and 4.9 times as high as that of Bi/BiOBr and BiOBr/AgBr, demonstrating that the highest separation efficiency of charge carriers in the heterostructured Bi/BiOBr/AgBr. The photocatalytic activity of Bi/BiOBr/AgBr microspheres just exhibited a slight decrease after three consecutive cycles. The photocatalytic mechanism investigation confirmed that the superoxide radicals (O₂^•−) were the dominant reactive oxygen species for RhB degradation in Bi/BiOBr/AgBr suspension.     

Crystal structure of mixed-ligand silver(I) hydrogen iminodiacetate

The crystal structure of mixed-ligand silver(I) hydrogen iminodiacetate has been studied. The composition of the [Ag₂(C₄H₆NO₄)(NO₃)(H₂O)] _n ([Ag₂(HIda)(NO₃)(H₂O)] _n ) coordination polymer has been refined. The NO₃ and H₂O ligands in the complex form rather weak coordination bonds with the Ag atoms. The system of hydrogen bonds in the structure has been considered. The formation of a chain of hydrogen bonds between the disordered H₂O molecules was established.     

Synthesis and photocatalytic properties of sunlight-responsive BiOBr–CoWO4 heterostructured nanocomposites

Efficient sunlight-responsive BiOBr–CoWO₄ heterostructured nanocomposite photocatalysts were prepared via a chemical precipitation route at 100°C in 4 hours. The prepared BiOBr–CoWO₄ heterostructures were characterized for phase identification, chemical composition, surface morphology, optical properties and surface area using various techniques. The X-ray diffraction pattern of the BiOBr–CoWO₄ nanocomposite was composed of diffraction peaks equivalent to both the tetragonal phase of BiOBr and the monoclinic phase of CoWO₄ nanoparticles. X-ray photoelectron spectral study of the BiOBr–CoWO₄ nanocomposite revealed orbitals of both BiOBr and CoWO₄ compounds. Transmission electron microscopy images revealed that spherical particles of CoWO₄ (20–25 nm) were dispersed on the surface of BiOBr. UV–visible–near-infrared spectral study of the BiOBr–CoWO₄ nanocomposite showed good visible-light absorption. Among the manufactured materials, BiOBr–CoWO₄-2 nanocomposite showed better charge carrier separation efficiency, as demonstrated by photoluminescence and time-resolved fluorescence. To study the practical utility of the prepared materials, their photocatalytic capability was examined for the degradation of rhodamine B (RhB) aqueous solution under sunlight irradiation. The photodegradation results showed that BiOBr–CoWO₄-2 nanocomposite degraded 98.69% RhB solution and the degradation constant was 0.067 min⁻¹, which was 5.6 and 22.5 times larger than that of pure BiOBr and CoWO₄ nanoparticles, respectively, after 60 minutes of sunlight irradiation. The superior photoactivity was facilitated by electron–hole pair separation and transfer driven by the heterostructure interface between BiOBr particles and CoWO₄ nanoparticles. The removal of RhB was initiated by photogenerated h⁺, O₂^{• −} and ^•OH reactive species based on the scavenger effect.     

Synchronous activation of Ag nanoparticles and BiOBr for boosting solar-driven CO2 reduction

Artificial photosynthesis of valuable chemicals from CO₂ is a potential way to achieve sustainable carbon cycle. The CO₂ conversion activity is still inhibited by the sluggish charge kinetics and poor CO₂ activation. Herein, Ag nanoparticles coupled BiOBr have been constructed by in-situ photoreduction strategy. The crafting of interface between Ag nanoparticles and BiOBr nanosheets, achieving an ultra-fast charge transfer. The BiOBr semiconductor excited electrons and plasmonic Ag nanoparticles generated high-energy hot electrons synchronous accelerates the C=O double bond activation. Thus, the optimized Ag/BiOBr-2 heterostructure shows excellent CO₂ photoreduction activity with CO production of 133.75 and 6.83 µmol/g under 5 h of 300 W Xe lamp and visible light (λ > 400 nm) irradiation, which is 1.51 and 2.81 folds versus the pristine BiOBr, respectively. The mechanism of CO₂ photoreduction was in-depth understood through in-situ FT-IR spectrum and density functional theory calculations. This study provides some new perspectives into efficient photocatalytic CO₂ reduction.     

S掺杂BiOBr的制备及其光催化固氮性能研究

以硫脲、五水硝酸铋为前驱体,采用溶剂热法制备出S掺杂BiOBr光催化剂。利用XRD,SEM,XPS,UV-Vis DRS、光电化学性能等对所制备的光催化材料进行了一系列表征。同时,在可见光照射下对S掺杂BiOBr进行光催化固氮性能研究。结果表明：S掺杂BiOBr的晶体结构未发生改变,比表面积增大。同时,形成的氧空位有利于吸附、活化N2分子和促进光生载流子的迁移,进而提高其光催化固氮性能。与BiOBr相比,S掺杂BiOBr的光催化产氨为25.36 mg?L-1?h-1?g-1cat,是BiOBr的4.6倍。最后,经4次循环实验,S掺杂BiOBr催化剂仍保持稳定的固氮效率。