Laser-induced changes in silver metal nanoparticles incorporated in viscous media

The effect of laser pulse irradiation on silver metal nanoparticles in ethylene glycol and glycerol is studied and compared with the parallel processes in aqueous solutions. The influence of 355 nm laser pulse irradiation at the surface plasmon frequency and on the size of the silver nanoparticles is examined by UV-Vis absorption spectroscopy and by transmission electron microscopy. It appears that viscosity of the medium plays a crucial role for the stabilization of the melted particles in the absence of the stabilizer. In ethylene glycol containing PVP, fragmentation of particles was observed. In neat glycerol, similar excitation led to morphological changes as the nanoparticles fused to produce particles of larger size. The changes in reduction of shape and size are considered to occur through melting and vaporization of the silver nanoparticles.     

Measurement of reaction cross-sections for 64Ni(n, γ) 65Ni at E n = 0.025 eV and 58Ni(n, p) 58Co at E n = 3.7 MeV

The reaction cross-sections for ⁶⁴Ni(n, γ) ⁶⁵Ni at E _n  = 0.025 eV and ⁵⁸Ni (n, p) ⁵⁸Co at E _n  = 3.7 MeV have been experimentally determined using activation and off-line γ-ray spectrometric technique. The thermal neutron flux used is from the thermal Column of the reactor APSARA at BARC, Mumbai, whereas the neutron energy of 3.7 MeV is from the ⁷Li(p, n) reaction at Pelletron facility, TIFR, Mumbai. The ⁶⁴Ni(n, γ) ⁶⁵Ni and ⁵⁸Ni(n, p) ⁵⁸Co reactions cross-sections from present work are compared with the available literature data and found to be in good agreement. The ⁵⁸Ni(n, p) ⁵⁸Co reaction as a function of neutron energy is also calculated theoretically using TALYS computer code version 1.2 and found to be higher than the experimental data.     

Bismuth-Oxide-Decorated Graphene Oxide Hybrids for Catalytic and Electrocatalytic Reduction of CO2

Global warming challenges are fueling the demand to develop an efficient catalytic system for the reduction of CO₂, which would contribute significantly to the control of climate change. Herein, as-synthesized bismuthoxide-decorated graphene oxide (Bi₂O₃@GO) was used as an electro/thermal catalyst for CO₂ reduction. Bi₂O₃@GO is found to be distributed uniformly, as confirmed by scanning electron and transmission electron microscopic analysis. The X-ray diffraction (XRD) pattern shows that the Bi₂O₃ has a β-phase with 23.4 m² g⁻¹ BET surface area. Significantly, the D and G bands from Raman spectroscopic analysis and their intensity ratio (I_D/I_G) reveal the increment in defective sites on GO after surface decoration. X-ray photoelectron spectroscopic (XPS) analysis shows clear signals for Bi, C, and O, along with their oxidation states. An ultra-low onset potential (−0.534 V vs. RHE) for the reduction of CO₂ on Bi₂O₃@GO is achieved. Furthermore, potential-dependent (−0.534, −0.734, and −0.934 vs. RHE) bulk electrolysis of CO₂ to formate provides Faradaic efficiencies (FE) of approximately 39.72, 61.48, and 83.00 %, respectively. Additionally, in time-dependent electrolysis at a potential of −0.934 versus RHE for 3 and 5 h, the observed FEs are around 84.20 % and 87.17 % respectively. This catalyst is also used for the thermal reduction of CO₂ to formate. It is shown that the thermal reduction provides a path for industrial applications, as this catalyst converts a large amount of CO₂ to formate (10 mm ).     

Evaluation of Probiotic Characteristics of Siderophoregenic <Emphasis Type="Italic">Bacillus</Emphasis> spp. Isolated from Dairy Waste

Siderophoregenic Bacillus strain DET9 has been selectively isolated from dairy waste. It was evaluated for probiotic characteristics and susceptibility pattern against antibiotics. Its spores showed excellent tolerance to simulated gastrointestinal tract conditions and exhibited antimicrobial activity against organisms such as Escherichia coli, Micrococcus flavus, and Staphylococcus aureus. Its susceptibility to antibiotics reduces the prospect to donate resistance determinants if administered in the form of probiotic preparations. It was observed to produce ∼60 mg/l catecholate type of siderophore under iron stressed conditions, identified as a 2,3-dihydroxy benzoic acid by high-performance liquid chromatography, infrared spectroscopy, nuclear magnetic resonance, and mass spectral analysis. Partial 16S-rRNA gene sequencing analysis shows that the isolate exhibited homology with Bacillus thuringiensis and Bacillus weihenstephanensis, whereas biochemical characterization revealed its novelty. DET9 exhibited no mortality of fishes in a 60-day trial, when fishes (surfi tetra) were challenged up to 100 ppm cell concentration, with their daily diet.     

Density functional studies on chromium catalyzed ethylene trimerization

Mechanism of ethylene trimerization using chromium catalyst is investigated using density functional methods. Recent experimental results indicate Cr-based homogeneous catalysts to follow metallacycle pathway in ethylene tri-, teta- and oligomerization reactions. Given the importance of chlorinated Cr-based active catalysts in these reactions, we have used “bare” minimal ligands like Cl^? and considered catalytic cycles with neutral or cationic intermediates starting with [Cr(II)Cl₂(ethylene)₂] and [Cr(II)Cl(ethylene)₂]⁺, respectively. We have compared both ‘Cossee’ and the ‘metallacycle’ mechanisms on these model systems utilizing density functional computations at B3LYP/LANL2DZ(d,p) level. The metallacycle mechanism with cationic Cr(II)–Cr(IV) intermediates is found to be the most favored path, with oxidative coupling of two coordinated ethylene to form the chromacyclopentane being the rate determining step (RDS). We also found that with neutral intermediates the Cossee pathway rather than the metallacycle mechanism is followed. Thus in spite of the simplicity of using just Cl^? as ligand in the model catalytic intermediates, our computational results match remarkably well with many recent and important experimental findings.     

"Click chemistry" inspired synthesis of pseudo-oligosaccharides and amino acid glycoconjugates

[reaction: see text] Various pseudo-oligosacchardies and amino acid glycoconjugates were synthesized via an intermolecular 1,3-dipolar cycloaddition ("click") reaction using easily accessible carbohydrate and amino acid derived azides and alkynes as building blocks. It is pertinent to mention that the conjugation reaction is highly regioselective and high yielding and can be carried out under mild reaction conditions.     

Sensitive extractive spectrophotometric methods for the determination of trazodone hydrochloride in pharmaceutical formulations

Two simple, rapid and sensitive extractive spectrophotometric methods have been developed for the assay of trazodone hydrochloride (TRH) in pure and pharmaceutical formulations. These methods are based on the formation of chloroform soluble ion-association complexes of TRH with bromothymol blue (BTB) and with bromocresol purple (BCP) in KCl-HCl buffer of pH 2.0 (for BTB) and in NaOAc-AcOH buffer of pH of 3.6 (for BCP) with absorption maximum at 423 nm and at 408 nm for BTB and BCP, respectively. Reaction conditions were optimized to obtain the maximum color intensity. The absorbance was found to increase linearly with increase in concentration of TRH, which was corroborated by the calculated correlation coefficient values (0.9996, 0.9945). The systems obeyed Beer's law in the range of 0.2-14.5 and 0.2-14.1 microg/ml for BTB and BCP, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data. No interference was observed from common excipients present in pharmaceutical formulations. The proposed methods are simple, accurate and suitable for quality control applications.     

Propargyl glycosides as stable glycosyl donors: anomeric activation and glycoside syntheses

The advantages of stable glycosyl donors for saccharide coupling are many, and we describe herein the utility of propargyl glycosides for anomeric activation and glycoside synthesis exploiting the alkynophilicity of AuCl3. Various aglycones were reacted with propargyl glycosides, resulting in the formation of an alpha,beta-mixture of glycosides and disaccharides in good yields.     

Neutrino masses from SUSY: Different contributions and their implications

We discuss the various sources of neutrino masses in supersymmetric standard models with explicit lepton number violation. We show that the bilinear lepton number violating soft terms in models with either bilinear or trilinear lepton number violating couplings in the superpotential, play an important role in determining the neutrino mass spectrum. A comparative study of the neutrino mass spectrum and its implications for the present neutrino anomalies in these models is presented.     

Study of the structural phase transformation,and optical behavior of the as synthesized ZnO–SnO2–TiO2 nanocomposite

Bulk nanocomposites ZnO–SnO₂–TiO₂ were synthesized by solid-state reaction method. The X-ray diffraction patterns and Raman spectra of bulk nanocomposite as a function of sintering temperature (700 °C–1300 °C) indicate that the structural phases of SnO₂ and TiO₂ depend on the sintering temperature while the ZnO retains its hexagonal wurtzite phase at all sintering temperatures and SnO₂ started to transform into SnO at 900 °C and completely converted into SnO at 1100 °C, whereas the titanium dioxide (TiO₂) exhibits its most stable phase such as rutile at low sintering temperature (≤900°C) and it transforms partially into brookite phase at high sintering temperature (≥ 900 °C). The optical band gap of nanocomposite ZnO–SnO₂–TiO₂ sintered at 700 °C, 900 °C, 1100 °C and 1300 °C for 16 hours is calculated using the transformed diffuse reflectance ultra violet visible near infra red (UV–VisNIR) spectra and has been found to be 3.28, 3.29, 3.31 and 3.32 eV, respectively.