Visible light induced electron transfer process over nitrogen doped TiO(2) nanocrystals prepared by oxidation of titanium nitride

Nitrogen doped TiO(2) nanocrystals with anatase and rutile mixed phases were prepared by incomplete oxidation of titanium nitride at different temperatures. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), core level X-ray photoelectron spectroscopy (CL XPS), valence band X-ray photoelectron spectroscopy (VB XPS), UV-vis diffuse reflectance spectra (UV-vis DRS), and visible light excited photoluminescence (PL). The photocatalytic activity was evaluated for photocatalytic degradation of toluene in gas phase under visible light irradiation. The visible light absorption and photoactivities of these nitrogen doped TiO(2) nanocrystals can be clearly attributed to the change of the additional electronic (N(-)) states above the valence band of TiO(2) modified by N dopant as revealed by the VB XPS and visible light induced PL. A band gap structure model was established to explain the electron transfer process over nitrogen doped TiO(2) nanocrystals under visible light irradiation, which was consistent with the previous theoretical and experimental results. This model can also be applied to understand visible light induced photocatalysis over other nonmetal doped TiO(2).     

Photocatalytic hydrogen evolution over surface-modified titanate nanotubes by 5-aminosalicylic acid decorated with silver nanoparticles

The efficiency of titanate-nanotubes-based photocatalysts towards hydrogen production was studied in the presence of the sacrificial agent, 2-propanol. The highest hydrogen production rate (~120 μmol h⁻¹ g⁻¹) was observed over surface-modified titanate nanotubes by 5-amino salicylic acid decorated with nanometer-sized silver nanoparticles. The X-ray diffraction analysis, transmission electron microscopy, nitrogen adsorption–desorption isotherms, and diffuse reflection spectroscopy were applied to characterize the prepared photocatalytic materials. The better photocatalytic performance of inorganic–organic hybrid materials in comparison to the pristine titanate nanotubes is a consequence of their improved light-harvesting ability due to the formation of interfacial charge transfer (ICT) complex, as well as the presence of metallic silver nanoparticles that suppress the recombination of photo-generated charge carriers. The spin trapping EPR experiments under irradiation of prepared photocatalysts with either UV or visible light were used to monitor the appearance of hydroxyl radicals and superoxide radical anions. The generation of superoxide radical anions under visible light irradiation was detected for hybrid materials, but not for the pristine titanate nanotubes. These results are a consequence of enhanced promotion of electrons to the conduction band due to extended absorption in visible spectral range in hybrids and support the higher efficiency of hydrogen generation observed for surface-modified titanate nanotubes by 5-amino salicylic acid decorated with silver nanoparticles.     

Synthesis and characterization of AgO nanostructures by precipitation method and its photocatalyst application

In this research, a precipitation method was used in order to synthesize AgO nanostructures with the aid of silver nitrate as the starting reagent in an aqueous solution. To examine the effect of different surfactants such as glucose, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, and cetyltrimethylammonium bromide on the morphology and particle size of final products several tests were performed. The structural, morphological, and optical properties of as-obtained products were characterized by techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and ultraviolet–visible spectroscopy. Furthermore, the hysteresis loop measured at room temperature shows a ferromagnetic behavior of the AgO nanostructures. To evaluate the catalytic properties of nanocrystalline silver oxide (AgO), the photocatalytic degradation of rhodamine-B under visible light irradiation was carried out.     

Preparation of novel CdS-graphene/TiO2 composites with high photocatalytic activity for methylene blue dye under visible light

In this study, CdS combined graphene/TiO₂ (CdS-graphene/TiO₂) composites were prepared by a sol–gel method to improve on the photocatalytic performance of TiO₂. These composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). The photocatalytic activities were examined by the degradation of methylene blue (MB) under visible light irradiation. The photodegradation rate of MB under visible light irradiation reached 90·1% during 150 min. The kinetics of MB degradation were plotted alongside the values calculated from the Langmuir–Hinshelwood equation. 0·1 CGT sample showed the best photocatalytic activity, which was attributed to a cooperative reaction between the increase of photo-absorption effect by graphene and photocatalytic effect by CdS.     

The synthesis and photocatalytic activity of ZnSe microspheres

This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C(4)H(4) Se) and ZnCl(2) without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (～2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed.     

Combination of photocatalytic and antibacterial effects of silver oxide loaded on titania nanotubes

Silver nanoparticles were photodeposited on titania nanotubes and their antibacterial activity was tested. Investigation of the structure and morphology of the nanostructures showed nanometer size silver oxide particles homogeneously distributed on titania nanotubes. Furthermore the modified titania nanotubes were spin-coated as thin films and their antibacterial activity was examined under visible light irradiation and in complete darkness. Although silver oxide loaded titania nanotubes (TiNT-AgO) has a potential for antibacterial activity in both conditions with and without light irradiation, enhanced activity was observed in visible light irradiation condition.     

Green synthesis of stable silver nanoparticles by the main reduction component of green tea (Camellia sinensis L.)

Recently the use of medicinal plants potential in the production of nanoparticles has received serious attention. Here, the main component of Camellia sinensis L. (green tea) extract was detected by spectroscopy and the optimal conditions were determined for their performance in green synthesis of silver nanoparticles at room temperature. Epigallocatechin gallate was identified as the dominant component in the extract as determined by spectroscopy, and it was established that its oxidation was a function of the solution pH. Transmission electron microscopy, dynamic light scattering, and visible absorption spectroscopy (UV‐Vis) confirmed the reduction in silver ions to silver nanoparticles (Ag NPs). Controlling over Ag NPs shape and narrow size distribution was achieved with 10 ml green tea leaf extract solution and in different reaction pH. Spherical colloidal Ag NPs with well‐defined hydrodynamic diameters (with average hydrodynamic size of 27.9–50.2 nm) were produced. Silver nitrate concentrations used in this study were lower than that of reported in similar works, and synthesis efficiency was also higher. Nanoparticles were perfectly spherical and their uniformity, compared to similar studies, was much higher. These NPs showed higher degree of stability and were aqueously stable for >10 months in dark glasses at 4°C.Inspec keywords: hydrodynamics, nanoparticles, particle size, pH, visible spectra, ultraviolet spectra, reduction (chemical), transmission electron microscopy, silver, microorganisms, nanofabrication, colloids, biomedical materials, nanomedicine, drug delivery systemsOther keywords: transmission electron microscopy, dynamic light scattering, visible absorption spectroscopy, silver ions, narrow size distribution, silver nitrate concentrations, green synthesis, medicinal plants, solution pH, green tea leaf, hydrodynamic size, silver nanoparticles, Camellia sinensis L, drug delivery, reduction component, epigallocatechin gallate, UV‐visible spectra, hydrodynamic diameters, spherical colloidal Ag NPs, temperature 4.0 degC, Ag     

Effect of Ag loading on activated carbon doped ZnO for bisphenol A degradation under visible light

Silver modified activated carbon doped zinc oxide (Ag/AC-ZnO) was synthesized via a calcination-electroless deposition route. The samples were characterized by X-ray powder diffractometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the Ag/AC-ZnO was evaluated for bisphenol A degradation in the presence of H₂O₂ under visible light irradiation. The archived results showed that the photocatalytic activity of the Ag/AC-ZnO was higher than that of AC-ZnO and pure ZnO. The cytotoxicity of the bisphenol A after photocatalysis under visible light irradiation was tested using L929 mouse fibroblast cells and the obtained results indicated that the treated bisphenol A solution exhibited no cytotoxicity against normal cells.     

Controlled synthesis in large-scale of CdS mesospheres and photocatalytic activity

In the present work, we reported the controlled synthesis of CdS mesospheres composed of radially arranged nanorods by hydrothermal method without any surfactant. The as-prepared CdS mesospheres were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicated that these CdS mesospheres present a hexagonal structure and free of deleterious phases. SEM micrographs showed that CdS mesospheres are composed of several nanoparticles with growth mechanism via aggregation of particles. The photocatalytic activities were investigated by degradation of reactive brilliant dye X-3B (C.I. Reactive Red 2) under visible light irradiation. Results show that 93% X-3B was degraded after 100 min irradiation by the best one sample. The results indicate that the as-prepared CdS samples are promising candidate materials for visible light responsive photocatalysts.     

Synthesis and characterisation of nano-sized nickel titanate photocatalyst

Visible light activated nickel titanate (NiTiO₃) nanopowders were synthesised by a simple and organic-free co-precipitation method. X-ray diffraction and transmission electron microscopy were used to characterise the crystal structure. The average crystalline size of the synthesised nickel titanate is found to be 100?nm. The visible light photocatalytic activity was evaluated on the basis of photobleaching of methyl orange in aqueous solution. The results show that NiTiO₃ exhibits good photocatalytic activity under visible light irradiation. The enhanced photocatalytic activity of nickel titanate under visible light is due to the lower band-gap value of nickel titanate (3.10?eV) compared to that of TiO₂ (3.23?eV).     

An efficient visible light photocatalyst prepared from TiO<Subscript>2</Subscript> and polyvinyl chloride

An efficient visible light photocatalyst has been prepared from TiO₂ nanoparticles and a partly conjugated polymer derived from polyvinyl chloride (PVC). It was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The visible light photocatalytic activity of the as-prepared photocatalyst was evaluated by the photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The XPS, FT-IR, and Raman spectra show that the partly conjugated polymer derived from PVC exists on the surface of the TiO₂ nanoparticles. The UV–Vis DRS, XRD, and TEM results reveal that the modification of the partly conjugated polymer can obviously improve the absorbance of the TiO₂ nanoparticles in the range of visible light and hardly affect their size and crystallinity. The visible light photocatalytic activity of the as-prepared TiO₂ nanocomposites is higher than that of commercial TiO₂ (Degussa P25) and comparable with those of visible light photocatalysts reported in the literature. Their visible light photocatalytic stability is also good. The reasons for their excellent visible light photocatalytic activity and the major factors affecting their photocatalytic activity are discussed.     

Photocatalytic degradation of organic dyes with manganese-doped ZnO nanoparticles

Manganese-doped and undoped ZnO photocatalysts were synthesized via wet-chemical techniques. Doping of ZnO with manganese (Mn(2+)) was intended to create tail states within the band gap of ZnO. These can subsequently be used as efficient photocatalysts which can effectively degrade organic contaminants only with visible light irradiation. Photocatalysts prepared with these techniques, which were characterized with transmission electron microscopy (TEM), infrared spectroscopy (FTIR), photo-co-relation spectroscopy (PCS) and UV-vis-spectroscopy showed significant difference in the optical absorption of Mn-doped ZnO. Enhancement in optical absorption of Mn-doped ZnO indicates that it can be used as an efficient photocatalyst under visible light irradiation. The photo-reduction activities of photocatalysts were evaluated using a basic aniline dye, methylene blue (MB) as organic contaminant irradiated only with visible light from tungsten bulb. It was found that manganese-doped ZnO (ZnO:Mn(2+)) bleaches MB much faster than undoped ZnO upon its exposure to the visible light. The experiment demonstrated that the photo-degradation efficiency of ZnO:Mn(2+) was significantly higher than that of undoped ZnO and might also be better than the conventional metal oxide semiconductor such as TiO(2) using MB as a contaminant.     

Cationic phenylene ethynylene polymers and oligomers exhibit efficient antiviral activity

The antiviral activities of poly(phenylene ethynylene) (PPE)-based cationic conjugated polyelectrolytes (CPE) and oligo-phenylene ethynylenes (OPE) were investigated using two model viruses, the T4 and MS2 bacteriophages. Under UV/visible light irradiation, significant antiviral activity was observed for all of the CPEs and OPEs; without irradiation, most of these compounds exhibited high inactivation activity against the MS2 phage and moderate inactivation ability against the T4 phage. Transmission electron microscopy (TEM) and SDS polyacrylamide gel electrophoresis (SDS-PAGE) reveal that the CPEs and OPEs exert their antiviral activity by partial disassembly of the phage particle structure in the dark and photochemical damage of the phage capsid protein under UV/visible light irradiation.     

Directly ultraviolet photochemical deposition of silver nanoparticles on silica spheres: Preparation and characterization

A simple method was developed to directly deposit silver nanoparticles on the surface of silica spheres. The photochemical reduction was carried out by ultraviolet irradiation in air atmosphere at room temperature. The [Ag(NH₃)₂]⁺was reduced to silver atoms upon ultraviolet irradiation. Silver atoms subsequently deposited on the surface of silica spheres and agglomerated into silver nanoparticles. Silica spheres with silver nanoparticles of different size and density can be simply controlled by adjusting the UV-light irradiation time. The silver nanoparticles deposited on silica spheres were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy.     

Photocatalytic properties of silver nanoparticles decorated nanobranched TiO2 nanofibers

In this study, nanobranched TiO2 nanofibers and silver loaded nanobranched TiO2 nanofibers were prepared by electrospinning technique followed by TiCl4 aqueous solution treatment and silver photodeposition method. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to investigate the morphology of the products. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) were conducted on the samples to study their chemical composition as well as crystallographic structure. The photocatalytic activities of these produced nanofibers were examined with two organic dyes, methylene blue and methyl orange, under ultraviolet (UV) light irradiation. The effect of nanobranches and silver modification on TiO2 nanofibers was revealed in the photocatalysis process. The photocatalytic degradation rates of silver loaded on nanobranched TiO2 nanofibers were 1.6 and 1.7 times as that of pure TiO2 nanofibers in the presence of methylene blue and methyl orange, respectively, which indicated silver nanoparticles combined nanobranches modified on the surface of TiO2 nanofibers could enhance the photocatalytic ability.     

类石墨相氮化碳二维纳米片的制备及可见光催化性能研究

以三聚氰胺为原料制备类石墨相氮化碳(g-C3N4),采用球磨与超声联用技术制备g-C3N4二维纳米片. 利用X 射线衍射光谱(XRD)、紫外-可见漫反射(UV-Vis)光谱、扫描电镜(SEM)、透射电镜(TEM)、原子力显微镜(AFM)、荧光(PL)光谱等分析手段对制备的催化剂进行了表征. 结果表明: g-C3N4二维纳米片具有与体相g-C3N4相同的晶体结构,片层结构仅有5个原子层厚.g-C3N4二维纳米片增加了对可见光的吸收,提高了光生电子-空穴对的分离效率.以染料罗丹明B的降解反应研究了g-C3N4二维纳米片在可见光下的催化性能. 结果表明,球磨超声1 h后制备的g-C3N4二维纳米片表现出最佳的光催化性能, 150 min 内对罗丹明B的降解率高达94%,是体相g-C3N4的2 倍.     

Preparation of Fe3+-doped TiO2 catalysts by controlled hydrolysis of titanium alkoxide and study on their photocatalytic activity for methyl orange degradation

Fe3+-doped TiO2 (Fe-TiO2) porous microspheres were prepared by controlled hydrolysis of Ti(OC4H9)4 with water generated "in situ" via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption-desorption methods. All of the undoped TiO2 and Fe-TiO2 samples exclusively consist of primary anatase crystallites, which further form porous microspheres with diameters ranging from 150 to 500 nm. The photocatalytic activity of Fe-TiO2 catalysts was evaluated from the photodegradation of methyl orange (MO) aqueous solution both under UV and visible light irradiation. Fe3+ doping effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.1 and 0.2%, respectively. The photocatalytic mechanisms of Fe-TiO2 catalysts were tentatively discussed.     

Synthesis of porous Fe3O4/g-C3N4 nanospheres as highly efficient and recyclable photocatalysts

A facile approach for the preparation of Fe₃O₄/g-C₃N₄ nanospheres with good porous structure has been demonstrated by a hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible light (UV–vis) absorbance spectra and X-ray photoelectron spectroscopy (XPS). The photocatalytic decomposition of methyl orange (MO) by the as-prepared samples was carried out under visible light irradiation. The reusability and magnetic properties were also investigated. The results revealed that the porous Fe₃O₄/g-C₃N₄ nanospheres showed considerable photocatalytic activity, and exhibited excellent reusability and magnetic properties with almost no change after five runs.     

Synthesis of silver and sulphur codoped TiO<Subscript>2</Subscript> nanoparticles for photocatalytic degradation of methylene blue

In the present work, silver and sulphur codoped TiO₂ (Ag–S/TiO₂) photocatalysts were effectively prepared by sol–gel technique. The prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive x-ray analysis (EDX), Fourier transform infrared (FTIR) spectroscopy, diffuse reflectance UV–Vis spectroscopy (UV-DRS) and photoluminescence (PL). The XRD patterns consisted of anatase crystalline phases and the particle size and shape of the prepared samples were observed by SEM and HR-TEM. The presence of doping ions was confirmed by EDX analysis, the decreased band-gap energy of Ag–S codoped TiO₂ nanoparticles was investigated by UV-DRS. The decreased in the intensity of Ag–S codoped TiO₂ was absorbed due to the lower separation of electron–hole pairs were confirmed by PL spectrum. The Ag–S codoped TiO₂ showed higher photocatalytic activity than pure and single-doped TiO₂ in the photodegradation of methylene blue (MB) aqueous solution under visible light irradiation. The given work was a good model to associate the considering of the synergistic effect of metal and non-metal codoped TiO₂ in the photocatalysis and photo electrochemistry.     

Ag掺杂APS改性的TiO2颗粒的制备及其光催化降解作用

为提高Ag/TiO2纳米颗粒的光催化降解作用,采用聚合凝胶工艺路线,以钛酸四丁酯为前驱体,硝酸银为银源,通过向反应体系引入鳌合剂醋酸、表面改性剂γ-氨丙基三乙氧基硅烷(APS)以及还原剂甲醛等添加剂,制备出TiO2粉体及Ag/TiO2纳米复合粉体。利用FT-IR、XRD、TG-DTA、TEM和UV-Vis-NIR等手段对样品进行表征。结果表明,经γ-氨丙基三乙氧基硅烷改性的TiO2颗粒掺Ag后分散性得到改善,粒径约1 nm的Ag颗粒较均匀地分布在10～15 nm TiO2颗粒上;可见光的利用和锐钛矿热稳定性都得到提高;Ag/TiO2纳米颗粒在光照下对甲基橙具有良好的光催化降解效果。