Inelastic neutron scattering and lattice dynamics of GaPO<Subscript>4</Subscript>

We report here measurements of phonon spectrum and lattice dynamical calculations for GaPO₄. The measurements in low-cristobalite phase of GaPO₄ are carried out using high-resolution medium-energy chopper spectrometer at ANL, USA in the energy transfer range 0–160 meV. Semiempirical interatomic potential in GaPO₄, previously determined using ab-initio calculations have been widely used in studying the phase transitions among various polymorphs. The calculated phonon spectrum using the available potential show fair agreement with the experimental data. However, the agreement between the two is improved by including the polarisability of the oxygen atoms in the framework of the shell model. The lattice dynamical models are also exploited for calculations of various thermodynamic properties of GaPO₄.     

Cascade One-Pot Synthesis of Orange-Red-Fluorescent Polycyclic Cinnolino[2,3-f]phenanthridin-9-ium Salts by Palladium(II)-Catalyzed C−H Bond Activation of 2-Azobiaryl Compounds and Alkenes

Quaternary ammonium salts were synthesized in moderate to good yields through double oxidative C−H bond activation on azobenzenes. The mechanism of the highly regioselective reaction of 2-azobiaryls with alkenes to give orange-red-fluorescent cinnolino[2,3-f]phenanthridin-9-ium salts and 15H-cinnolino[2,3-f]phenanthridin-9-ium-10-ide is proposed to involve ortho C−H olefination of the 2-azobiaryl compound with the alkene, intramolecular aza-Michael addition, concerted metalation–deprotonation (CMD), reductive elimination, and oxidation.     

Simple and Efficient One-Pot Synthesis of Nitriles from Amides and Oximes Using in Situ–Generated Burgess-Type Reagent

The dehydration of aldoximes and amides, and oxidation of benzoin are accomplished in one-pot using in situ–generated Burgess-type reagent.

RhIII‐Catalyzed C?H Activation: A Versatile Route towards Various Polycyclic Pyridinium Salts

An efficient and convenient method for the synthesis of highly substituted polycyclic pyridinium salts from the reaction of various 2‐aryl‐pyridines and 2‐aryl‐sp²‐nitrogen‐atom‐containing heterocycles with alkynes through rhodium(III)‐catalyzed C? H activation and annulation under an O₂ atmosphere is described. A possible mechanism that involves the chelation‐assisted C? H activation of the 2‐aryl‐pyridine substrate, insertion of the alkyne, and reductive elimination is proposed. This mechanism was supported by the isolation of a five‐membered rhodacycle ( I′ ). In addition, kinetic isotope studies were performed to understand the intimate reaction mechanism.     

Preparation of Silver Nanoparticles Incorporated Electrospun Polyurethane Nano-fibrous Mat for Wound Dressing

Polyurethane foam is currently used as an exudate absorptive wound dressing material. In this study silver (Ag) nanoparticles were incorporated into electrospun polyurethane (PU) nanofiber to enhance the antibacterial as well as wound healing properties. The electrospinning parameters were optimized for PU with and without silver nanoparticles. Silver nanoparticles were synthesized by aqueous and organic methods. The water absorption, antibacterial and cytocompatibility of the PU-Ag nanofibers were studied and compared to that of conventional PU foam. The results indicated that the PU-Ag nanofibers could be used for wound dressing applications.     

Fabrication of Immunosensor Based on Polyaniline,Fullerene‐C60 and Palladium Nanoparticles Nanocomposite: An Electrochemical Detection Tool for Prostate Cancer

Present work demonstrates the fabrication of new and facile sandwich‐type electrochemical immunosensor based on palladium nanoparticles (PdNPs), polyaniline (PANI) and fullerene‐C₆₀ nanocomposite film modified glassy carbon electrode (PdNP@PANI‐C₆₀/GCE) for ultrasensitive detection of Prostate‐specific antigen (PSA) biomarker. PdNP@PANI‐C₆₀ was electrochemically synthesized on GCE and used as an electroactive substrate. PdNP@PANI‐C₆₀ was characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Primary antibody anti‐PSA (Ab1) was covalently immobilized on PdNP@PANI‐C₆₀/GCE using NHS/EDC linkers. In the presence of PSA antigen, horseradish peroxidase secondary antibody (HRP‐Ab2) was brought into the surface of the electrode, developing stable amplified signals of H₂O₂ reduction. Under the optimal conditions, a linear curve for determination of PSA at the proposed immunosensor was 1.6×10^?4 ng.mL^?1 to 38 ng.mL^?1 with a limit of detection (LOD) of 1.95×10^?5 ng.mL^?1. The proposed immunosensor was successfully validated in serum and urine samples towards PSA detection with satisfactory and acceptable results.     

Mittag-leffler process

First-order autoregressive Mittag-Leffler process is studied. Methods for generating dependent (first-order autoregressive Markovian) sequences of random variables with Mittag-Leffier marginal distributions are discussed. Comparison of the first-order autoregressive Mittag-Leffler process with the first-order autoregressive exponential process of Gaver and Lewis [1] is done. As an application, the first-order autoregressive Mittag-Leffier process is fitted to weakly stream flows of the Kallada River in Kerala, India.     

An inorganic-organic diblock copolymer photoresist for direct mesoporous SiCN ceramic patterns via photolithography

A high resolution negative-tone-type of inorganic-organic diblock copolymer photoresist was synthesized as a novel precursor for simple and direct fabrication of SiCN ceramic mesoporous patterns with ordered nanoscale pores by using a "top-down" photolithographic technique and the subsequent sacrificial processes of a "bottom-up" self-assembled nanostructure.     

Structural studies of nano silica employing on-line ultrasonic studies

Monodispersed, nano silica particles have been prepared by sol-gel hydrolysis and condensation of the metal alkoxide using pH buffer. The prepared particles are characterised by XRD, FTIR, BET, SEM, TEM measurements. The measurements reveal that the size and shape of silica particles depend on concentration of water. In addition, the ultrasonic longitudinal velocity and attenuation of the nano silica particles have been measured at a frequency of 5?MHz over a wide range of temperatures from 300?K to 1150?K in nano silica. The different structural transitions, such as monoclinic, orthorhombic, orthorhombic with a non-integral super lattice, stable orthorhombic and hexagonal, which exist in silica are explained based on on-line high-temperature ultrasonic velocity and attenuation measurements.     

喹啉及其衍生物的多相不对称氢转移反应

喹啉及其衍生物的多相不对称氢转移是制备杂环手性化合物的理想策略.多相手性催化体系具有催化剂可循环利用及产物分离提纯容易等优势.然而,喹啉及其衍生物的多相手性高效催化体系鲜有报道.这主要是由于多相手性氢转移为水-油-固三相反应,在反应的过程中,传质问题极大影响固体催化剂的催化性能.因此,发展具有相转移功能的手性催化材料,是提高多相氢转移体系催化效率的有效途径.本文采用一锅法合成策略,通过离子液体(ILs)为连接基团实现了TsDPEN手性配体在SBA-15介孔孔道中的嫁接.与Rh盐配位后,获得手性固体催化剂SBA-ILBF4-TsDPEN-Rh.FI-IR光谱和13C NMR结果表明,手性催化活性中心成功负载在SBA-15中,随着手性活性中心负载量的增加,SBA-ILBF4-TsDPEN-Rh的比表面积、孔径和孔容逐渐降低.在喹啉衍生物不对称氢转移反应中,SBA-ILBF4-TsDPEN-Rh系列催化剂催化得到产物的ee值为91％,表明多相手性催化剂具有较高的手性选择性.多相手性催化剂的催化活性随着活性中心负载量的上升而呈现下降的趋势,这主要是由于活性中心负载量较低的多相催化剂具有更高的比表面积和孔容,更有利于催化过程中的传质.与均相手性催化剂相比,优化后的多相手性催化剂表现出更高的催化活性(TOF值分别为75和92 h-1).作为对比,本文还合成了采用烷基链为连接基团的SBA-TsDPEN25-Rh,并以其为基础进一步嫁接了ILs基团,得到SBA-TsDPEN20-ILBF4-Rh.在相同的反应条件下,SBA-ILBF4-TsDPEN50-Rh表现出更高的催化活性.上述结果证实了ILs基团在反应过程中起到相转移以及富集氢源甲酸盐的作用,极大促进了喹哪啶不对称氢转移多相催化体系的活性,并且ILs基团和手性活性中心在空间距离上的接近更有利于催化活性的提高.此外,本文还研究了反应体系pH值对固体催化剂上反应速率的影响,随着反应的进行,反应溶液的pH会呈现明显上升的趋势,导致反应速率减缓以及底物转化受限.通过在反应过程中加入适量甲酸或者选用浓度更高的缓冲溶液可以有效防止催化过程中反应速率的减慢.综上可见,负载手性催化剂中的连接基团对多相手性催化剂的催化性能有重要影响.通过改变手性配体的连接基团提高手性固体催化剂的催化活性和手性选择性的策略可以拓展到其他多相手性催化体系.