Synthesis of beta-cyclodextrin-modified water-dispersible Ag-TiO2 core-shell nanoparticles and their photocatalytic activity

The beta-cyclodextrin-modified Ag-TiO2 core-shell nanoparticles were prepared by sodium borohydrate reduction of AgNO3 and the subsequent hydrolysis of the tetraisopropyl orthotitanate in an aqueous medium. Inversely in the preparation of beta-cyclodextrin-modified TiO2-Ag core-shell nanoparticles, first hydrolysis and then following reduction were carried out. The synthesized spherical core-shell nanoparticles were highly water-dispersible and had an average diameter in the range of 9 to 12 nm. A significant shifting of surface plasmon band was observed for the synthesized Ag-TiO2 and TiO2-Ag core-shell nanoparticles. On a model reaction, namely, the photodegradation of phenol by the UV light irradiation, the photocatalytic property of TiO2 nanoparticles was enhanced, when the Ag nanoparticle was embedded in the core of TiO2 nanoparticles but TiO2 nanoparticles coated by Ag shell decreased the photocatalytic property of TiO2 nanoparticles. The mechanism is ascribed to the surface plasmon characteristics of Ag in the core of the TiO2 nanoparticles under the acceleration by host-guest inclusion characteristics.     

Synthesis and characterization of Zr4+, La3+ and Ce3+ doped mesoporous TiO2: evaluation of their photocatalytic activity

Sol-gel method was used to synthesize Zr(4+), La(3+) and Ce(3+) doped mesoporous TiO(2) materials with different weight percentage (0.5, 1.0, 2.0 and 3.0 wt%) using triblock copolymer as the structure directing template in ethanol/water medium. Characterization revealed the isomorphic substitution of Zr(4+) ion into the lattice of TiO(2), and surface binding nature of La(3+) and Ce(3+) ions on mesoporous TiO(2). Microscopic examination confirmed the surface adsorption of foreign ion which could alter the particle morphology. The size of the particles was less than 20 nm. Photocatalytic activity of metal ions doped mesoporous TiO(2) was evaluated using aqueous alachlor as a model pollutant. It was found that 1 wt% Ce(3+) doped mesoporous TiO(2) exhibited higher activity than pure and other metal ions doped mesoporous TiO(2). The change of oxidation state of Ce(3+) is suggested to be the cause for enhanced photocatalytic activity.     

Template-free synthesis of beta-In2S3 superstructures and their photocatalytic activity

In this article, we have successfully fabricated various morphological beta-Indium sulfide (In2S3) superstructures by using indium thiocyanate complex at acidic pH. All the synthesis has been performed by a template-free, hydrothermal method at 195 degrees C for 3 h. The photocatalytic activity of synthesized In2S3 have been investigated by using UV-B (lamda = 365 nm) light with Methyl Orange dye as a model pollutant. The synthesized photocatalyst was characterized by using XRD, FE-SEM, HR-TEM, DRS spectra and nitrogen adsorption analysis. The influence of indium precursors and solvents on the morphology as well as the surface properties has also been discussed. The XRD result shows that cubic phase beta-In2S3 formed under all experimental conditions. A plausible mechanism of the In2S3 microsphere formation has been discussed based on experimental observations.     

Synthesis, characterization, and assembly of beta-In2S3 nanoparticles

Semiconductor nanoparticles of Indium Sulphide were synthesized by a hydrothermal method using InCl3 and Na2S. Powder X-ray Diffraction analysis confirmed that the product obtained was nanocrystals of single-phase beta-In2S3. The crystallite size distribution was obtained from the diffraction profile and the average size was approximately 5 nm. The compositional analyses performed on the as-prepared powder showed that the material was devoid of any impurity with an In:S ratio very close to 2:3. A colloid of very fine In2S3 particles was obtained from the as-prepared powder by suspending them in acetonitrile. The optical absorption of this colloid showed evidence of strong quantum confinement of excitons and as a result the particles yielded intense photoluminescence in the violet-blue region. These colloidal particles were then electrophoretically driven on to a transparent conducting substrate to assemble into a nanostructure. A Grazing Incidence X-ray Diffraction analysis of the deposited layer revealed that the preferred orientation noticed in the native powder was removed in the deposit. The surface morphology of the deposit studied using SEM and AFM displayed an inherent ordering behaviour in the clusters organized into a two-dimensional film. The locus of the cluster lines tend to form closed circles, at the nanoscopic as well as microscopic scales, indicative of certain strong neighborhood correlations. Such structures may be expected to exhibit novel correlated properties also.     

Synthesis and characterization of indium xanthates and their use for the preparation of beta-In2S3 nanoparticles

Synthesis and characterization of various classical indium xanthate complexes of the type [InCl(3-n)(S2COR)n] (n = 1, 2, or 3; R = Me, Et, Pr(i), and Bu(s)) have been discussed. Crystalline beta-ln2S3 nanoparticles were obtained by the solvent thermolysis of indium tris-alkylxanthates in ethylene glycol at 196 degrees C, and were characterized by elemental analysis, IR, powder XRD, and XPS techniques. TEM results showed that the size of beta-In2S3 nanoparticles depended on the nature of the precursor used. The optical properties of beta-In2S3 nanocrystals have shown quantum confinement of the excitonic transition.     

Preparation, characterization, and photocatalytic activity of Gd3+ doped TiO2 nanoparticles

TiO2 and Gd3+ doped TiO2 nanoparticles were prepared by sol-gel method and the materials were characterized by XRD, TEM, SEM-EDX, BET, FT-IR, UV-Vis absorption, and Raman spectral analysis. The photocatalytic activity of nano TiO2 and Gd/TiO2 nanoparticles was evaluated using a model pollutant propoxur, a carbamate pesticide, in a batch type UV photoreactor. The results revealed higher photocatalytic activity for Gd/TiO2 nanoparticles than both TiO2 nanoparticles and commercial TiO2 (Degussa P-25). The enhanced photocatalytic activity of Gd/TiO2 relative to TiO2 is attributed to its increased band gap energy as evidenced from the blue shift to shorter wavelength observed in the UV-Vis abso4ption spectra. The recombination rate of photogenerated electron-hole pair decreased due to increase in the band gap, which enhanced the charge transfer efficiency of Gd/TiO2 nanoparticles. Gd3+ with its half filled 7 f subshell facilitated rapid electron transfer at solid-liquid interface by shallowly trapping the electrons. Among the various dopant level of gadolinium, 0.3 wt% Gd/TiO2 nanoparticles showed higher activity than others due to its higher surface area.     

Chemical synthesis of faceted α-Fe2O3 single-crystalline nanoparticles and their photocatalytic activity

Faceted hematite nanocrystals have been synthesized via a hydrothermal route and their different morphologies can be tuned by appropriate stabilizer molecules. Detailed observation by high-resolution transmission electron microscopy and atomic force microscopy has revealed many terraces, steps, and kinks on the faceted surface of hematite nanoparticles, and thus, one growth mechanism of the terrace-step-kink model has been suggested to play a major role in determining the equilibrium morphology, together with effect of surface chemistry via the interaction between outer surfaces of iron and oxygen ions and functional groups. The photocatalytic activities were evaluated by decomposing rhodamine B dye. It has been shown that polyhedron hematite particles enclosed by high-index surface planes exhibited higher photoactivity. Density functional theory calculations revealed that the higher photoactivity originates from the more flat band edge in directions normal to the surface planes.     

Synthesis and characterization of polyaniline/MCM-41 nanocomposites and their photocatalytic activity

The novel organic-inorganic nanocomposites were synthesized via in-situ polymerization of polyaniline (PANI) with mesoporous silica (MCM-41) for methylene blue (MB) dye degradation under visible light. The synthesized PANI/MCM-41 nanocomposites were characterized through Fourier transform infrared (FTIR), X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and UV-visible studies. The structural and optical properties confirmed the interaction between PANI and MCM-41. The photocatalytic experiments showed that the MB dye was efficiently degraded by approximately 70% under light irradiation over the surface of the PANI/MCM-41 nanocomposites. The degradation might occur due to the efficient charge separation of the e(-)-h+ pairs at the interface of PANI and MCM-41 in the excited state under light irradiation.     

Synthesis, characterization and photocatalytic H2 generation over ternary indium titanate nanoparticles

A low temperature surfactant-free solution-phase method has been successfully developed for the synthesis of ternary In2TiO5, nanoparticles using a solvothermal route. The mechanistic aspects of synthesis of In2TiO5 nanoparticles from precursors, In(acac)3 and Ti(IV) isopropoxide in benzyl alcohol at 220 degrees C under solvothermal conditions, were investigated by GC-MS and 13C{1H} NMR analysis. The N2-BET surface area of the 5-8 nm sized In2TiO5 nanoparticles was found to be 60 m2 g(-1), which decreased with increase in calcination temperature; 38 m2 g(-1) at 800 degrees C; 5 m2 g(-1) at 1200 degrees C. The High resolution transmission electron microscopy (HR-TEM) shows well-developed lattice fringes of the crystalline nanoparticles, and selected area electron diffraction (SAED), pattern was indexed to be orthorhombic In2TiO5. The nanoparticles show better photocatalytic hydrogen generation from water-methanol mixtures over bulk In2TiO5, anatase TiO2 nanoparticles prepared by identical route and commercial TiO2 photocatalyst (Degussa, P25) under UV-visible irradiation (16% UV + 84% visible). Photocatalytic properties as a function of crystallinity and surface area of indium titanate nanoparticles have also been investigated. The high photoactivity obtained is correlated with the electronic and crystal structure of In2TiO5.     

Synthesis, characterization and photocatalytic evaluation of visible light activated C-doped TiO2 nanoparticles

We have demonstrated heterogeneous photocatalytic degradation of microcystin-LR (MC-LR) by visible light activated carbon doped TiO(2) (C-TiO(2)) nanoparticles, synthesized by a modified sol-gel route based on the self-assembly technique exploiting oleic acid as a pore directing agent and carbon source. The C-TiO(2) nanoparticles crystallize in anatase phase despite the low calcination temperature of 350 °C and exhibit a highly porous structure that can be optimized by tuning the concentration of the oleic acid surfactant. The carbon modified nanomaterials exhibited enhanced absorption in the broad visible light region together with an apparent red shift in the optical absorption edge by 0.5 eV (2.69 eV), compared to the 3.18 eV of reference anatase TiO(2). Carbon species were identified by x-ray photoelectron spectroscopy analysis through the formation of both Ti-C and C-O bonds, indicative of substitution of carbon for oxygen atoms and the formation of carbonates, respectively. Electron paramagnetic resonance spectroscopy revealed the formation of two carbon related paramagnetic centers in C-TiO(2), whose intensity was markedly enhanced under visible light illumination, pointing to the formation of localized states within the anatase band gap, following carbon doping. The photocatalytic activity of C-TiO(2) nanomaterials was evaluated for the degradation of MC-LR at pH 3.0 under visible light (λ > 420 nm) irradiation. The doped materials showed a higher MC-LR degradation rate than reference TiO(2), behavior that is attributed to the incorporation of carbon into the titania lattice.     

花状Bi_2WO_6光催化剂的制备及性能研究

采用简单水热法制备了具有三维花状结构的斜方晶Bi2WO6光催化剂,利用XRD、SEM、BET等分析技术对催化剂的结构和形貌进行了表征。考察了反应时间、Bi2WO6加入量、染料罗丹明B初始浓度和光源对罗丹明B光催化降解效果的影响。实验结果表明,180℃下水热12h合成的Bi2WO6催化剂,在加入量为2g/L,溶液pH为6.5,并以模拟日光500W氙灯(不加滤光片)为光源,光照30min内,对浓度为10mg/L的罗丹明B去除率最高达99.6%。水热制备的花状Bi2WO6具有较高的光催化活性。     

Synthesis,characterization and photocatalytic activity of ZnO-SnO2 nanocomposites

Nanocomposites of coupled ZnO-SnO₂ photocatalysts were synthesized by the coprecipitation method and were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, surface area analyzer and scanning electron microscopy. Their photocatalytic activity was investigated under UV, visible and solar light and evaluated using methylene blue (MB) as a model pollutant. The performance of the coupled ZnO-SnO₂ photocatalysts was found to be related to the Zn/Sn molar ratio and to the calcination conditions. The photocatalyst with a Zn/Sn molar ratio of 1:0.05 calcined at 600 °C for 2 h showed the maximum degradation rate of MB under different lights used. Its photocatalytic activity was found to be about two times that of ZnO and about 10 times that of SnO₂ which can be explained by the heterojunction effect. Charge separation mechanism has been studied.     

Self-assembling behaviour of Pt nanoparticles onto surface of TiO2 and their resulting photocatalytic activity

In the present study, self-assembling behaviour of guest nanoparticles (platinum) onto the surface of host support (titanium dioxide) during photodeposition process as a function of solution pH has been explored in detail by means of transmission electron microscope (TEM). The photocatalytic activity of the resulting bimetallic nanoassembly (Pt/TiO₂) was evaluated by studying the degradation of two organic pollutants viz. triclopyr and methyl orange. Microscopic studies revealed that the deposition and/or distribution of Pt nanoparticles onto the surface of TiO₂ were strongly guided by the ionization state of support which in turn was regulated by the solution pH of photodeposition process. A direct relationship between the solution pH of deposition process and the photocatalytic activity of resulting bimetallic catalyst has been observed. A mechanism based on the interparticle interaction between TiO₂ and hydrolytic products of metal ions has been proposed for the differences in the photocatalytic activity of the resulting nanocomposite.     

Synthesis of TiO2/Bi2S3 heterojunction with a nuclear-shell structure and its high photocatalytic activity

TiO₂/Bi₂S₃ heterojunctions with a nuclear-shell structure were prepared by the coprecipitation method. The products were characterized by X-ray diffraction analysis, Raman spectra, transmission electron microscope images and energy dispersion X-ray spectra. Results showed that as-prepared Bi₂S₃ was urchin-like, made from many nanorods, and TiO₂/Bi₂S₃ heterojunctions have a similar nuclear-shell structure, with Bi₂S₃ as the shell and TiO₂ as the nuclear. The photocatalytic experiments performed under UV irradiation using methyl orange as the pollutant revealed that the photocatalytic activity of TiO₂ could be improved by introduction of an appropriate amount of Bi₂S₃. However, excessive amount of Bi₂S₃ would result in the decrease of photocatalytic activity of TiO₂. The relative mechanism was proposed.     

Hydrothermal synthesis of nanostructured TiO2 particles and characterization of their photocatalytic antimicrobial activity

Nanostructured titania particles were synthesized by using hydrothermal processing and the photocatalytic antimicrobial activities were characterized. Both sol-gel synthesized and commercial TiO2 (anatase) samples were processed with two step hydrothermal treatments, under alkaline and neutral conditions. Scanning Electron Microscope (SEM) images showed that alkaline treatment yields nanofibers and lamellar structured particles from the commercial anatase and sol-gel synthesized samples respectively. Further treatment of nanofibers and nanostructured lamellar particles with distilled water results with crystal growth and the formation of nano structured bipyramidal crystalline particles. The photocatalytic antimicrobial activities of the samples were determined against Escherichia coil under irradiation. It was observed that the samples treated under alkaline conditions have improved activity than the original anatase samples. Limited activity and resulting time lag in bacterial inactivation were observed for hydrothermally treated samples with distilled water. However, a post treatment comprising the UV irradiation in aqueous conditions enhanced the photocatalytic activity.     

Synthesis,characterization, photocatalytic and reusability studies of capped ZnS nanoparticles

This paper presents results of a study on the structural and morphological properties of 2-mercaptoethanol (2-ME) capped ZnS nanoparticles (NPs). The photocatalytic and reusability study of the synthesized NPs to degrade dyes was also done. ZnS semiconductor NPs were synthesized via chemical precipitation route using 2-ME as a stabilizing agent. The as-prepared NPs were characterized by X-ray diffraction (XRD) technique to confirm the nanometer sized particle formation. Morphological features of capped ZnS NPs were determined by transmission electron microscopy (TEM). Dynamic light scattering (DLS) technique was used to determine the hydrodynamic size of capped ZnS NPs. UV-Vis studies were done to determine the absorption edge and bandgap of the capped ZnS NPs. Fourier transform infrared spectroscopy (FT-IR) studies were done to confirm the presence of 2-ME on the surface of NPs. Photocatalytic studies of the as-prepared ZnS NPs were done by taking Ponceau S and crystal violet dyes as model pollutants. Their comparative degradation behaviour has been discussed. Reusability study of ZnS NPs was done to ensure its applicability as recycled catalyst in photocatalysis. The result showed photocatalytic enhancement of reused catalyst. Possible reason has been discussed in this work.     

Synthesis,characterization, and its photocatalytic activity of double-walled carbon nanotubes-TiO2 hybrid

Double-walled carbon nanotube (DWCNT)-TiO₂ hybrid was prepared by hydrothermal method and characterized by X-ray diffraction, electron microscopy, N₂-adsorption analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of DWCNT-TiO₂ hybrid was tested by the photocatalytic degradation of sulfathiazole. The experimental results showed that the introduction of the DWCNTs provides DWCNT-TiO₂ hybrid with visible light-induced photoactivity and a large surface area. The DWCNTs were coated with TiO₂ nanoparticles, which generated an intimate contact between the DWCNTs and TiO₂. The DWCNT-TiO₂ hybrid showed an excellent visible-light-induced activity, compared with multi-walled carbon nanotube-TiO₂ and single-walled carbon nanotube-TiO₂ hybrids, which can be attributed to the unique electronic structure of the DWCNTs that can work well as not only a photosensitizer but also an electron conductor. In addition, DWCNT-TiO₂ hybrid with the DWCNTs of long length showed higher degradation efficiency than that with the short length.     

Synthesis and characterization of silver nanoparticles and their antimicrobial efficacy

An efficient protocol for synthesis of silver nanoparticles (AgNPs) using the combination of aqueous extract of Tinospora cordifolia leaves and 5 mM silver nitrate (AgNO₃) solution was developed. This study revealed that bioactive compounds present in the extract function as stabilizing and capping agent for AgNPs. Scanning electron microscope and transmission electron microscope studies confirm the structure and surface morphology of the AgNPs. The size of synthesized AgNPs was in the range of 30–50 nm having spherical morphology. The crystalline nature of NPs was defined by the X-ray diffraction pattern. The AgNPs were found to be toxic against pathogenic bacteria such as Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Staphylococcus aureus (ATCC 29213) and against plant pathogenic fungi Fusarium oxysporum (MTCC 8608) and Sclerotinia sclerotiorum (MTCC 8785). The use of AgNPs as antibacterial and antifungal agent is advantageous over other methods for control of pathogenic microorganisms, and it can be of great importance in developing novel drugs for curing many lethal diseases.     

Synthesis,defect characterization and photocatalytic degradation efficiency of Tb doped CuO nanoparticles

Monoclinic undoped and Tb doped CuO are prepared by solution combustion method and annealed at different temperatures. The effect of annealing and doping on their structural and optical properties of CuO are examined using XRD, FTIR and DRS. The surface and lattice defects in CuO and Tb doped CuO is analyzed qualitatively and quantitatively using positron lifetime and Doppler broadening spectroscopy. The average positron lifetime and electron momentum (energy) S parameter increases owing to the number of vacancies in the CuO lattice upon doping and decreases with increasing temperature. The migration of vacancies from grain to grain boundary region is observed at 600 °C annealed samples. At 800 °C, the overall behavior of lifetime value denotes that the vacancy type defect is recovered, cluster vacancy and microvoids exists with reducing size. The photocatalytic performance of undoped and Tb doped CuO on degradation of methylene blue (MB) and methyl orange (MO) is investigated under visible light for two different lamp power and dye concentration. The influence of annealing temperature and dopant ion on the efficiency is also elaborated. Enhanced photocatalytic efficiency in Tb doped CuO is observed upon annealing. X-ray photoelectron spectroscopy (XPS) result indicates that the valence states of Cu, O and Tb ions exist at the surface of the particles. Brunauer–Emmett–Teller N₂ adsorption–desorption analyses were employed to characterize specific surface area and porosity of Tb doped CuO. The doped CuO with pore size of about ～34 nm have a surface area of 16–28 m²/g. The surface area effect plays an important role in the enhanced catalytic performance on Tb doped catalysts.     

TEM microstructure characterization of nano TiO2 coated on nano ZrO2 powders and their photocatalytic activity

Nano TiO₂ coated commercial nano ZrO₂ powders (20 and 80 wt.%) were synthesized by a sol–gel process. Their microstructure and crystal structure depending on the calcination temperatures were investigated using XRD and HRTEM techniques. In the as-received powders, the nano TiO₂ particles attached to the ZrO₂ particles existed in an amorphous phase. After calcination at 450 and 600 °C, most of the TiO₂ powders were crystallized to an anatase type, whereas at 750 °C, they were changed to a rutile phase.From the comparison of photocatalytic activity, the nano TiO₂ coated ZrO₂ powders calcined at 450 and 600 °C showed excellent efficiency for the removal of methyl orange (MO). However, in the powders calcined at 750 °C, the photocatalytic activity was decreased due to the appearance of a rutile phase.