Synthesis and characterization of α/β-Bi2O3 with enhanced photocatalytic activity for 17α-ethynylestradiol

The α/β-Bi₂O₃ photocatalyst was successfully synthesized by a novel solvothermal-calcination method. The physical and chemical properties of as-prepared samples were characterized based on XRD, XPS, SEM, TEM, EDS, BET, UV–vis DRS and PL techniques. The synthesized α/β-Bi₂O₃ photocatalyst exhibited enhanced photocatalytic activity for 17α-ethinylestradiol (EE2), and 96.9% of EE2 was degraded after only 24 min of visible-light irradiation using α/β-Bi₂O₃ as photocatalyst. The reaction rate constant over α/β-Bi₂O₃ photocatalyst was 1.42, 2.23, 9.22 and 54.1 times higher than pure β-Bi₂O₃, α-Bi₂O₃+β-Bi₂O₃, α-Bi₂O₃ and P25 respectively. Effect of catalyst dosage and pH value was investigated. The possible photocatalytic mechanism has been discussed on the basis of the theoretical calculation and the experimental results. α/β-Bi₂O₃ was a fairly stable and efficient photocatalyst under the studied experimental conditions, proving that the α/β-Bi₂O₃ photocatalyst was a promising photocatalyst for the practical application.     

Synthesis,characterization and photocatalytic activity of CdS–montmorillonite nanocomposites

Nanocomposites based on cadmium sulfide (CdS) and Na-montmorillonite (Na⁺-Mt) were prepared by a hydrothermal method using Cd[NH₂CSNH₂]SO₄ complex as precursor of CdS which was derived from cadmium sulfate and thiourea. These nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and X-fluorescence (XF). The nanocomposites consist of nanosized CdS pillars, which tend to increase in size as the amount of complex precursor increases. The CdS crystals have a hexagonal symmetry. The photocatalytic activity of the obtained CdS–Mt nanocomposites is improved significantly compared to that of the Mt and pure CdS. The resulting CdS–Mt nanocomposites could degrade methylene blue and rhodamine 6G under near UV–visible irradiation.     

A novel TiO2 − xNx/BN composite photocatalyst: Synthesis,characterization and enhanced photocatalytic activity for Rhodamine B degradation under visible light

A novel TiO_2 − xN_x/BN composite photocatalyst was prepared via a facile method using melamine–boron acid adducts (M·2B) and tetrabutyl titanate as reactants. The morphological results confirmed that nitrogen-doped TiO₂ nanoparticles were uniformly coated on the surface of porous BN fibers. A red shift of absorption edge from 400 nm (pure TiO₂) to 520 nm (TiO_2 − xN_x/BN composites) was observed in their UV–Vis light absorption spectra. The TiO_2 − xN_x/BN photocatalysts exhibited enhanced photocatalytic activity for the degradation of Rhodamine B (RhB) and the highest photocatalytic degradation efficiency reached 97.8% under visible light irradiation for 40 min. The mechanism of enhanced photocatalytic activity was finally proposed.     

AgBr@Ag/TiO2 core–shell composite with excellent visible light photocatalytic activity and hydrothermal stability

AgBr@Ag/TiO₂ core–shell photocatalysts were fabricated by a facile green route. TiO₂ was uniformly coated on the surface of cubic AgBr, making AgBr@Ag/TiO₂ core–shell photocatalyst show excellent hydrothermal stability. Beneficial from that Ag nanoparticles and AgBr can respond to visible light and core–shell structure can effectively separate the photogenerated electrons and holes, AgBr@Ag/TiO₂ core–shell composites exhibited outstanding visible light photocatalytic activity for the degradation of acid orange 7. The activity of AgBr@Ag/TiO₂ is related to the thickness of TiO₂ shell, and the optimal shell thickness for obtaining the highest activity is 10 nm.     

Synthesis of heterostructured Bi2O3–CeO2–ZnO photocatalyst with enhanced sunlight photocatalytic activity

The development of heterostructured semiconductor photocatalysts makes a noteworthy advancement in environmental purification technology. In this work, a novel heterostructured Bi₂O₃−CeO₂−ZnO, fabricated by a combination of microwave-assisted hydrothermal and thermal decomposition methods, showed an enhanced photocatalytic activity for Rhodamine B (RhB) degradation under sunlight, as compared to pristine ZnO, Bi₂O₃, CeO₂, and commercial Degussa TiO₂-P25. The obtained products were thoroughly characterized by various techniques including X- ray powder diffraction (PXRD), field emission scanning electron microscopy (FE-SEM), elemental color mapping, energy-dispersive X-ray spectroscopy (EDAX), Raman spectrometry, Fourier transform infrared (FT-IR) spectroscopy, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and photoluminescence (PL) spectroscopy. PXRD analysis reveals that the heterostructure has the monoclinic lattice phase of α-Bi₂O₃, the cubic phase of CeO₂ and the hexagonal wurtzite phase of ZnO. FE-SEM images show that Bi₂O₃−CeO₂−ZnO has an ordered mixture of nanorod and nanochain structures. EDAX, elemental color mapping, Raman and FT-IR analyses confirm the successful formation of the heterostructured Bi₂O₃−CeO₂−ZnO. The UV–Vis DRS results demonstrate that Bi₂O₃−CeO₂−ZnO exhibits wide visible-light photoabsorption in 400–780 nm range. Moreover, the reduction in PL intensity of the heterostructured Bi₂O₃−CeO₂−ZnO, when compared to the pristine Bi₂O₃, CeO₂, and ZnO, indicates enhanced charge separation. The study on the mechanism displayed that the improved photocatalytic activity of Bi₂O₃−CeO₂−ZnO could be attributed to (1) the efficient separation of photoinduced electrons and holes of the photocatalysts, caused by the vectorial transfer of electrons and holes among ZnO, CeO₂ and Bi₂O₃, and (2) the wide visible-light photoabsorption range. This study introduces a new class of promising sunlight-driven photocatalysts.     

Preparation,characterization and photocatalytic activity of a novel nanostructure composite film derived from nanopowder TiO2 and sol–gel process using organic dispersant

A novel sol–gel-derived titanium dioxide nanostructure composite has been prepared by spin-coating and investigated for the purpose of producing films. The processing of the composite sol–gel photocatalysts involved utilizing of precalcinated nanopowder titanium dioxide as filler mixed with sol and heat treated. The sol solution was prepared by adding titanium tetra isopropoxide (Ti(OPr)₄ or TTP) to a mixture of ethanol and HCl 35.5% (mole ratio TTP:HCl:EtOH:H₂O = 1:1.1:10:10), then a solution of 2 wt% methylcellulose was added and stirred at room temperature. Precalcinated TiO₂ nanopowder was dispersed in the sol and the prepared mixture was deposited on the microscope glass slide by spin-coating. The inhomogeneity problem in preparation of composite film which causes peeling off and cracking after calcination due to the shrinkage of the films with thermal treatment were overcome by using methylcellulose (MC) as a dispersant. The composite heat treated at approximately 500 °C has the greatest hardness value. Surface morphology of composite deposits by scanning electron microscopy (SEM) showed remarkable increase in the composite surface area. Evaluation of the adhesion and bonding strength between the coating and substrate was carried out by the scratch test technique. The minimum load which caused the complete coating removal, for composite thick film was 200 g/mm² which indicates a strong bond to the substrate. Photocatalytic activity of the composite film was evaluated through the degradation of a textile dye, Light Yellow X6G (C.I. Reactive Yellow 2) as a model pollutant and were compared with those of similar composite thick film without MC, thin film of TiO₂ and TiO₂ nanopowder. The results show that the photocatalytic activity and stability of the composite films are higher than those of nanopowder TiO₂. However, a remarkable increase in the composite surface and good mechanical integrity make this composite film a viable alternative for commercial applications.     

Preparation and visible light photocatalytic activity of Ag/TiO₂/graphene nanocomposite

Great efforts have been made to develop efficient visible light-activated photocatalysts in recent years. In this work, a new nanocomposite consisting of anatase TiO(2), Ag, and graphene was prepared for use as a visible light-activated photocatalyst, which exhibited significantly increased visible light absorption and improved photocatalytic activity, compared with Ag/TiO(2) and TiO(2)/graphene nanocomposites. The increased absorption in visible light region is originated from the strong interaction between TiO(2) nanoparticles and graphene, as well as the surface plasmon resonance effect of Ag nanoparticles that are mainly adsorbed on the surface of TiO(2) nanoparticles. The highly efficient photocatalytic activity is associated with the strong adsorption ability of graphene for aromatic dye molecules, fast photogenerated charge separation due to the formation of Schottky junction between TiO(2) and Ag nanoparticles and the high electron mobility of graphene sheets, as well as the broad absorption in the visible light region. This work suggests that the combination of the excellent electrical properties of graphene and the surface plasmon resonance effect of noble metallic nanoparticles provides a versatile strategy for the synthesis of novel and efficient visible light-activated photocatalysts.     

Visible light responsive titanium dioxide–cyclodextrin–fullerene composite with reduced charge recombination and enhanced photocatalytic activity

Titanium dioxide (TiO₂)–fullerene (C₆₀) composite is prepared from TiO₂ and β-cylcodextrin (CD) encapsulated C₆₀ using the solar light irradiation. The absorption of the composite extends to the visible light region due to the charge transfer from CD and C₆₀ to TiO₂. The composite shows reduced charge recombination compared to that of the bare TiO₂ and TiO₂/CD. The rate constant values for the photodegradation reactions of methylene blue and 4-chlorophenol (4-CP) are significantly higher (∼2–5 times) for the composites with 0.5 and 1.5 wt.% C₆₀ compared to that of the bare TiO₂. Photocatalytic studies in the presence of scavengers reveal that the composites produce higher amount of reactive oxygen species (ROS). The enhanced photocatalytic activity of the composites is attributed to the visible light responsiveness, reduced charge recombination and increased formation of ROS. The photodegradation of 4-CP is significantly faster in the presence of the composite with 1.5 wt.% C₆₀ and is attributed to the synergistic effect of higher adsorption and increased ROS formation. The ROS formation by C₆₀ is possible because of the non-aggregated state of C₆₀ molecules in the composite and is assigned to the method which employs CD molecules to disperse C₆₀ in the composite.     

One-pot synthesis of graphene–BiOBr nanosheets composite for enhanced photocatalytic generation of reactive oxygen species

Graphene oxide (GO), BiOBr and graphene–BiOBr nanosheets composites (BiOBr–RG) were synthesized and characterized. It can be found that except for BiOBr nanosheets with pure tetragonal phase were grown uniformly on the graphene surface, little graphene layer also can load on the surface of BiOBr evenly. And we found that the graphene can change the conduction band (CB) and valence band (VB) of BiOBr toward enhanced photocatalytic activity for reactive oxygen species (ROS) generation than that of BiOBr under visible-light irradiation.     

Synthesis and characterization of chlorapatite–ZnO composite nanopowders

The influence of zinc oxide content on the formation of chlorapatite-based composite nanopowders in the mechanically alloyed CaO–CaCl₂–P₂O₅–ZnO system was studied. To mechanosynthesize composite nanopowders, different amounts of hydrothermally synthesized zinc oxide nanoparticles (0–10 wt%) were mixed with ingredients and then were mechanically activated for 5 h. Results showed that in the absence of zinc oxide, high crystalline chlorapatite nanopowder was obtained after 5 h of milling. In the presence of 4 and 7 wt% zinc oxide, the main product of milling for 5 h was chlorapatite–zinc oxide composite nanopowder. On increasing the zinc oxide content to 10 wt%, composite nanopowder was not formed due to improper stoichiometric ratio of the reactants. The crystallite size, lattice strain, volume fraction of grain boundary, and crystallinity degree of the samples fluctuated significantly during the milling process. In the presence of 7 wt% zinc oxide, the crystallite size and crystallinity degree reached 51±2 nm and 79±2%, respectively. During annealing at 900 °C for 1 h, the crystallization of composite nanopowder occurred and as a result the crystallinity degree rose sharply to 96±3%. In addition, the crystallite size increased to 77±2 nm after annealing at 900 °C. According to SEM and TEM images, the composite nanopowder was composed of both ellipse-like and polygonal particles with a mean size of about 98 nm.     

Preparation of cobalt coated TiO2 and WO3–TiO2 nanotube films via photo-assisted deposition with enhanced photocatalytic activity under visible light illumination

Highly ordered TiO₂ and WO₃–TiO₂ nanotubes were prepared by one-step electrochemical anodizing method and cobalt has been successfully deposited on these nanotubes by photo-assisted deposition process. The morphology, crystal structure, elemental composition and light absorption capability of samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray spectrometer and ultraviolet–visible spectroscopy methods. All cobalt loaded samples show an appearance of red shift relative to the unloaded samples. The degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of these novel visible-light-responsive photocatalysts. Results showed that the photocatalytic activity of bare WO₃–TiO₂ samples is higher than that with undoped TiO₂ sample. Compared with unmodified TiO₂ and WO₃–TiO₂, the Co/TiO₂ and Co/WO₃–TiO₂ samples exhibited enhanced photocatalytic activity in the degradation of methylene blue. Kinetic research showed that the reaction rate constant of Co/WO₃–TiO₂ is approximately 2.26 times higher than the apparent reaction rate constant of bare WO₃–TiO₂. This work provides an insight into designing and synthesizing new TiO₂–WO₃ nanotubes-based hybrid materials for effective visible light-activated photocatalysis. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity.     

Ultrasonic assisted synthesis of TiO2–reduced graphene oxide nanocomposites with superior photovoltaic and photocatalytic activities

In this work, TiO₂–reduced graphene oxide (RGO) nanocomposites were successfully produced by an ultrasonication-assisted reduction process. The reduction of graphene oxide (GO) and the formation TiO₂ crystals occurred simultaneously. The synthesized nanocomposite was characterized by SEM, EDX, Raman spectroscopy, FTIR, XRD, XPS, UV–vis spectroscopy, photoluminescence spectrometer and electrochemical impedance spectroscopy. As a result of the introduction of RGO, the light absorption of octahedral TiO₂ was markedly improved. The photocatalytic results revealed that weight percent of RGO has substantial influence on degradation of Rhodamine B under visible light irradiation. The enhancement of the photocatalytic activity can be attributed to the enhancement of the visible-light irradiation harvesting and efficiently separation of the photogenerated charge carriers. Meanwhile, upon the RGO loading, the photoelectric conversion efficiency of TiO₂–RGO nanocomposite modified electrode was also highly improved.     

Hydrothermal synthesis and visible-light photocatalytic activity of α-Fe2O3/TiO2 composite hollow microspheres

Novel α-Fe₂O₃/TiO₂ composite hollow spheres were successfully synthesized by a template-assisted precipitation reaction using urea as a precipitating agent and carbon spheres as templates in a mixed solvent of water and ethanol, and then calcined at 400 °C for 4 h. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption isotherms, and vibrating sample magnetometer. The influence of calcination temperature and the molar ratio of titanium to iron (R) on the photocatalytic activity of the samples was investigated. The results indicated that the composite spheres show magnetic characteristics at room temperature and good photocatalytic activity under visible-light irradiation compare to the single-component α-Fe₂O₃ particles. This method can be further applied to synthesize nanocomposites of magnetic metal oxide and other metal oxide.     

A novel SnS2–MgFe2O4/reduced graphene oxide flower-like photocatalyst: Solvothermal synthesis,characterization and improved visible-light photocatalytic activity

Flower-like SnS₂ decorated with MgFe₂O₄ nanoparticles and reduced graphene oxide (rGO) nanosheets were successfully synthesized by a facile solvothermal method. The morphological and crystal structure results confirmed that MgFe₂O₄ nanospheres were uniformly anchored on the surface of SnS₂ flower-like structure with the decoration of rGO nanosheets. The UV–vis diffuse reflectance spectra indicated that the SnS₂–MgFe₂O₄/rGO photocatalyst had a strong visible light absorption. The sample exhibited the highest photocatalytic activity for the degradation of methylene blue under visible light irradiation. The mechanism of improved photocatalytic activity was finally proposed.     

A novel TiO2/ZrxTi1−xO2 composite photocatalytic films

TiO₂/Zr_xTi_1−xO₂ composite films have been prepared by sol–gel method and their photocatalytic activity and stability have been investigated for the first time. Their surface morphology and average surface roughness are characterized by AFM. TiO₂ P25 and pure sol–gel TiO₂ films have also been prepared and investigated for comparison. Films with smaller crystallite size and larger surface roughness have been obtained by introduction of Zr_xTi_1−xO₂ intermediate layers between TiO₂ layers and substrate in the composite films. The results show that the photocatalytic activity and stability of the composite films are higher than those of pure sol–gel TiO₂ and TiO₂ P25 films.     

Synthesis and characterization of novel Ti3SiC2–cBN composites

In this paper, synthesis of novel super hard and high performance composites of titanium silicon carbide–cubic boron nitride (Ti₃SiC₂–cBN) was evaluated at three different conditions: (a) high pressure synthesis at ~ 4.5 GPa, (b) hot pressing at ~ 35 MPa, and (c) sintering under ambient pressure (0.1 MPa) in a tube furnace. From the analysis of experimental results, the authors report that the novel Ti₃SiC₂–cBN composites can be successfully fabricated at 1050 °C under a pressure of ~ 4.5 GPa from the mixture of Ti₃SiC₂ powders and cBN powders. The subsequent analysis of the microstructure and hardness studies indicates that these composites are promising candidates for super hard materials.     

Synthesis and characterization of a new polymer–drug conjugate with pH-induced activity

A well-defined, stimuli-responsive tetrapolymer with pH-responsive characteristics and targeting specificity has been synthesized by radical copolymerization of methacrylic acid, N-(2-hydroxypropyl)methacrylamide, methacryloyl glycylglycyl sulfamethoxazole, and N-(methacryloyl)glycylglycine 4-nitrophenyl ester. The structure and properties of tetrapolymer were investigated by NMR, FT-IR, UV–visible absorption, TEM and gel permeation chromatography. Incorporation of maleimide linker into tetrapolymer facilitates its conjugation with antibody fragments, as demonstrated by the solid-phase immunoassay experiments. The TEM image shows that tetrapolymer had self-assembled a spherical micelle with a diameter ranging from 50 to 150 nm. Altering the pH of the solution leads to a different extent of aggregation at pH 6.5–3.5, responding in accordance with the properties associated with the extracellular environment of solid tumors and endocytosis. Furthermore, fluorescence spectroscopy indicated a critical micelle concentration (CMC) of 1 mg/mL. Because of the solvation and ionization effects, the tetrapolymer showed considerably enhanced antibacterial activities against Escherichia coli in the presence of DMSO and the antibacterial activity increased with decreasing pH value.