Acid base properties and catalytic activity of vanadium pentoxide supported on cerium oxide

The surface acidity and basicity of vanadium pentoxide supported on CeO₂ were determined using a set of Hammett indicators. The data have been correlated with the catalytic activity of these oxides towards liquid phase acylation of phenol.     

One-pot synthesis of chalcone epoxides—A green chemistry strategy

Waste minimization is a very important aspect of an environmentally benign protocol. A one-pot consecutive process has been developed for chalcone epoxide synthesis that allows compounds to be prepared without having to isolate and purify the intermediates. The strategy utilizes consecutive Claisen Schmidt condensation and epoxidation reactions to prepare chalcone epoxides from substituted benzaldehydes and acetophenones in good yields.     

Ionic conduction behavior in PVC–PEG blend polymer electrolytes upon the addition of TiO2

The blend-based polymer electrolyte consisting of poly (vinyl chloride) (PVC) and poly (ethylene glycol) (PEG) as host polymers and lithium perchlorate (LiClO₄) as the complexing salt was studied. An attempt was made to investigate the effect of TiO₂ concentration in the unplasticized PVC–PEG polymer electrolyte system. The XRD and FTIR studies confirm the formation of a polymer–salt complex. The conductivity results indicate that the incorporation of ceramic filler up to a certain concentration (15 wt.%) increases the ionic conductivity and upon further addition the conductivity decreases. The maximum ionic conductivity 0.012 × 10⁻⁴ S cm⁻¹ is obtained for PVC–PEG–LiClO₄–TiO₂ (75–25–5–15) system. Thermal stability of the polymer electrolyte is ascertained from TG/DTA studies.     

Stability of electrostatic ion cyclotron waves in a multi-ion plasma

We have studied the stability of the electrostatic ion cyclotron wave in a plasma consisting of isotropic hydrogen ions (H⁺) and temperature-anisotropic positively (O⁺) and negatively (O⁻) charged oxygen ions, with the electrons drifting parallel to the magnetic field. Analytical expressions have been derived for the frequency and growth/damping rate of ion cyclotron waves around the first harmonic of both hydrogen and oxygen ion gyrofrequencies. We find that the frequencies and growth/damping rates are dependent on the densities and temperatures of all species of ions. A detailed numerical study, for parameters relevant to comet Halley, shows that the growth rate is dependent on the magnitude of the frequency. The ion cyclotron waves are driven by the electron drift parallel to the magnetic field; the temperature anisotropy of the oxygen ions only slightly enhance the growth rates for small values of temperature anisotropies. A simple explanation, in terms of wave exponentiation times, is offered for the absence of electrostatic ion cyclotron waves in the multi-ion plasma of comet Halley.     

A polymer-anchored cobalt(II) complex as a reusable catalyst for oxidation of benzene,ethylbenzene and cyclohexane

A polymer-supported cobalt complex of 2,6-bis(benzimidazolyl)pyridine (BBP) was synthesized by immobilization of BBP on chloromethylated polystyrene cross-linked with 6.5 % divinylbenzene, followed by complexation with CoCl₂ in methanol, and characterized by physico-chemical and spectroscopic methods. The polymer-bound Co(PS–BBP)Cl₂ was found to be more stable compared to free Co(BBP)Cl₂ as determined by TGA analyses. The catalytic activity of Co(PS–BBP)Cl₂ was investigated towards oxidation of benzene, ethylbenzene and cyclohexane using tert-butylhydroperoxide as oxidant. At optimum conditions, benzene showed 72.6 % conversion with 100 % selectivity towards phenol; ethylbenzene exhibited 97.0 % conversion with 82.5 and 17.4 % selectivity towards benzaldehyde and acetophenone, respectively, whilst conversion of cyclohexane was 60.0 with 75.8 and 24.1 % selectivity towards cyclohexanol and cyclohexanone. The unsupported complex Co(BBP)Cl₂ showed lower activities and selectivities compared to the polymer-supported complex. Co(PS–BBP)Cl₂ was found to be very active and reusable, giving high yields of the desired products. A possible reaction mechanism is proposed for these oxidation reactions.     

In Vitro Antibacterial Activity of Green Synthesized Silver Nanoparticles Using Azadirachta indica Aqueous Leaf Extract against MDR Pathogens

Rice is the most important staple food crop feeding more than 50% of the world’s population. Rice blast is the most devastating fungal disease, caused by Magnaporthe oryzae (M. oryzae) which is widespread in rice growing fields causing a significant reduction in the yield. The present study was initiated to evaluate the effect of green synthesized silver nanoparticles (AgNPs) on the biochemical constituents of rice plants infected with blast. AgNPs were synthesized by using Azadirachta indica leaf extract and their characterization was performed using UV-visible spectroscopy, particle size analyser (PSA), scanning electron microscope (SEM), and X-ray diffraction (XRD) which confirmed the presence of crystalline, spherical shaped silver nanoparticles with an average size of 58.9 nm. After 45 days of sowing, artificial inoculation of rice blast disease was performed. After the onset of disease symptoms, the plants were treated with AgNPs with different concentrations. Application of nanoparticles elevated the activity of antioxidative enzymes such as superoxide dismutase, catalase, peroxidase, glutathione reductase, and phenylalanine ammonia-lyase compared to control plants, and total phenol and reducing sugars were also elevated. The outcome of this study showed that an increase in all biochemical constituents was recorded for A. indica silver nanoparticles-treated plants. The highest values were recorded in 30 ppm and 50 ppm AgNPs-treated plants, which showed the highest resistance towards the pathogen. Green synthesized AgNPs can be used in future for disease control in susceptible varieties of rice. The synthesized AgNPs using A. indica leaf extract have shown promising antibacterial activity when tested against 14 multidrug-resistant (MDR) bacteria comprising Gram-negative bacteria Escherichia coli (n = 6) and Klebsiella pneumoniae (n = 7) with a good zone of inhibition diameter, tested with the disc diffusion method. Based on these findings, it appears that A. indica AgNPs have promise as an antibacterial agent effective against MDR pathogens.