Friedel–Crafts catalysis using supported reagents. Synthesis, characterization and catalytic application of ZnCl2 supported on fluoride‐modified sol–gel‐derived aluminosilicates

ZnCl₂–aluminosilicate catalysts were prepared via a sol–gel route involving fluoride‐catalyzed hydrolysis of aluminum and silicon alkoxides in the presence of NaF, KF, NH₄F and ZnF₂. The catalysts were characterized by employing ²⁹Si, ²⁷Al and ¹⁹F solid‐state MAS NMR. The dependence of the activities of the catalysts on the nature and amount of fluoride present in the catalysts were investigated using Friedel–Crafts alkylation reaction of benzene with benzyl chloride. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improvement of energy recovery from water hyacinth by using integrated system

The conventional methods for biofuel production provide a clean and renewable approach for bioenergy generation. However, the efficiency of these processes is still too low to compete with the existing technologies. Integrated bioprocesses could help in improving the overall yield and cost-effectiveness of the process. The present study deals with the evaluation of process efficiency in single, two and three-stage operation of dark fermentation, biomethanation and microbial fuels cells for recovering maximum energy from the invasive aquatic plant, water hyacinth. The merits and demerits of each process operated individually or in combination were evaluated. The results showed the integrated three-stage process yielded maximum energy recovery of 60% in the form of hydrogen, methane, and electricity with an overall COD removal of 94%. The present research work thus highlights the possibility of integrated hydrogen or methane-based biorefinery approach for the recovery of bioenergy from biomass.     

Enhanced wound healing activity of Ag–ZnO composite NPs in Wistar Albino rats

In the present study, silver (Ag) and Ag–zinc oxide (ZnO) composite nanoparticles (NPs) were synthesised and studied their wound‐healing efficacy on rat model. Ultraviolet–visible spectroscopy of AgNPs displayed an intense surface plasmon (SP) resonance absorption at 450 nm. After the addition of aqueous Zn acetate solution, SP resonance band has shown at 413.2 nm indicating a distinct blue shift of about 37 nm. X‐ray diffraction analysis Ag–ZnO composite NPs displayed existence of two mixed sets of diffraction peaks, i.e. both Ag and ZnO, whereas AgNPs exhibited face‐centred cubic structures of metallic Ag. Scanning electron microscope (EM) and transmission EM analyses of Ag–ZnO composite NPs revealed the morphology to be monodispersed hexagonal and quasi‐hexagonal NPs with distribution of particle size of 20–40 nm. Furthermore, the authors investigated the wound‐healing properties of Ag–ZnO composite NPs in an animal model and found that rapid healing within 10 days when compared with pure AgNPs and standard drug dermazin.Inspec keywords: wounds, tissue engineering, biomedical materials, nanocomposites, nanofabrication, nanomedicine, silver, zinc compounds, II‐VI semiconductors, wide band gap semiconductors, ultraviolet spectra, visible spectra, nanoparticles, particle size, surface plasmon resonance, spectral line shift, X‐ray diffraction, scanning electron microscopy, transmission electron microscopyOther keywords: enhanced wound healing activity, Ag‐ZnO composite nanoparticles, Wistar Albino rats, wound‐healing efficacy, ultraviolet‐visible spectroscopy, intense surface plasmon resonance absorption, aqueous Zn acetate solution, SP resonance band, blue shift, X‐ray diffraction analysis, diffraction peaks, face‐centred cubic structures, scanning electron microscope, SEM, transmission electron microscope, TEM, monodispersed hexagonal nanoparticles, quasihexagonal nanoparticles, particle size, animal model, time 10 d, size 20 nm to 40 nm, Ag‐ZnO     

Diospyros assimilis root extract assisted biosynthesised silver nanoparticles and their evaluation of antimicrobial activity

The current research study focuses on biosynthesis of silver nanoparticles (Ag NPs) for the first time from silver acetate employing methanolic root extract of Diospyros assimilis. The UV–Vis absorption spectrum of biologically synthesised nanoparticles displayed a surface plasmon peak at 428 nm indicating the formation of Ag NPs. The influence of metal ion concentration, reaction time and amount of root extract in forming Ag NPs by microscopic and spectral analysis was thoroughly investigated. Structural analysis from transmission electron microscopy confirmed the nature of metallic silver as face‐centered cubic (FCC) crystalline with an average diameter of 17 nm, which correlates with an average crystallite size (19 nm) calculated from X‐ray diffraction analysis. Further, the work was extended for the preliminary examination of antimicrobial activity of biologically synthesised Ag NPs that displayed promising activity against all the tested pathogenic strains.Inspec keywords: antibacterial activity, nanoparticles, silver, particle size, nanofabrication, nanomedicine, biomedical materials, ultraviolet spectra, visible spectra, optical microscopy, surface plasmon resonance, transmission electron microscopy, crystallites, X‐ray diffraction, microorganismsOther keywords: Diospyros assimilis root extract assisted biosynthesised silver nanoparticles, antimicrobial activity, silver acetate, methanolic root extract, UV‐visible absorption spectrum, biologically synthesised nanoparticles, surface plasmon peak, Ag NPs formation, metal ion concentration, reaction time, microscopic analysis, spectral analysis, structural analysis, transmission electron microscopy, metallic silver, FCC crystalline phase, average crystallite size, X‐ray diffraction analysis, pathogenic strains, Ag     

Substrate temperature-dependent physical properties of nanocrystalline zirconium titanate thin films

Nanocrystalline zirconium titanate thin films were deposited by direct current magnetron reactive sputtering on to glass substrates at room temperature and at different substrate temperatures of 423, 473, 523, and 573 K under high vacuum conditions. The deposited films have been characterized to study the physical properties of the films as a function of substrate temperature. Though the film exhibited amorphous characteristics at room temperature the higher temperatures resulted in the evolution of crystallites in the films. The crystallinity increased with temperature from 423 K onwards and the film deposited at 523 K exhibited a high crystallite size of 22 nm. The SEM images of the films revealed the improvement in the crystallinity from 423 to 523 K with dense columnar structure normal to the substrate. Further higher treatment deteriorated the film properties. The films showed a good transmittance of above 80%. A high optical transmittance of 91% and a high packing density of 96% have been observed for the film deposited at 523 K. The thickness of the films remained consistent at ~230 nm (±6 nm). It is noticed that an increase in the substrate temperature enhanced the structural, optical, and electrical properties of the films up to 523 K.     

V2O5 catalysts supported on Al2O3–SiO2 mixed oxide: V, H MAS solid-state NMR, DRIFTS and methanol oxidation studies

Alumina–silica mixed oxide, synthesized by the sol–gel technique, was used as a support for dispersing and stabilizing the active vanadia phase. The catalysts were characterized employing ⁵¹V and ¹H solid-state MAS NMR, diffuse reflectance FT-IR, BET surface area measurements. The partial oxidation activities of the catalysts were tested using methanol oxidation as a model reaction. ⁵¹V solid-state NMR studies on the calcined catalysts showed the peaks corresponding to the presence of both tetrahedral and distorted octahedral vanadia species at low vanadia loadings and with an increase in V₂O₅ content, the ⁵¹V chemical shifts corresponding to amorphous V₂O₅ like phases were observed. DRIFTS studies of the catalysts indicated the vibrations corresponding tetrahedral vanadia species at low and medium loadings and at high V₂O₅ contents the vibrations corresponding V=O bonds of V₂O₅ agglomerates were observed. The V/Al–Si catalysts exhibited high selectivity for the dehydration product dimethyl ether in the methanol partial oxidation studies showing the predominance of the acidic nature of the alumina–silica support over the redox properties of the active vanadia phase.