Green synthesis of nano-titania (TiO2 NPs) utilizing aqueous Eucalyptus globulus leaf extract: applications in the synthesis of 4H-pyran derivatives

Research on Chemical Intermediates - We have presented the green synthesis and characterization of nano-titania (TiO2 NPs) by using Eucalyptus globulus leaf aqueous extract in a greener approach...     

From understanding structures in antiferro-ferri and ferroelelectric liquid crystals to an unusual electro-optic effect in a bent-core nematic; a celebration of innovative materials

ABSTRACT

The field of liquid crystals is truly multidisciplinary with numerous examples of virtuous circles of interaction between chemistry, physics, theory and engineering resulting in breakthroughs in both fundamental understanding and novel applications. This paper, written to mark John Goodby’s 65th birthday, offers a personal perspective of the synergy between chemistry and physics from a collaboration that has spanned three decades. The first part of the paper reviews some of the physics insights that resulted from chiral liquid crystals fundamental to understanding structures in ferroelectric, ferrielectric and antiferroelectric systems. The second part of the paper describes some of the remarkable consequences of the anomalous elasticity and flexoelectricity found in the nematic phases of bent-core materials. In particular, we present unusual bowing of disclination lines in the nematic phase of a bent-core material in the presence of a field. Finally, the paper summarises some future prospects relating for bent-core materials. The paper by no means captures the amazing breadth of contribution that John’s chemistry has made to the subject, but aims to exemplify how his generous collaborative approach coupled with innovative chemistry and physical insight has led to paradigm changes in our subject.     

In situ generation of silver nanoparticles in cellulose matrix using Azadirachta indica leaf extract as a reducing agent

In the present work, silver nanoparticles (AgNPs) were in situ generated in cellulose matrix using leaf extract of Azadirachta indica as a reducing agent. The cellulose/AgNP composite films prepared were characterized by FTIR, X-ray diffraction (XRD), scanning electron microscope, and antibacterial tests. The infrared spectra indicated the association of organic materials with silver nanoparticles to serve as capping agents. Scanning electron micrographs showed that synthesized silver nanoparticles were nearly uniform and spherical in shape with diameter in the range of 61–110?nm. XRD confirmed the formation of AgNPs and Ag–O nanoparticles. The nanocomposite films showed good antibacterial activity against Escherichia coli bacteria.     

Stereochemical Rules Govern the Soft Self-Assembly of Achiral Compounds: Understanding the Heliconical Liquid-Crystalline Phases of Bent-Core Mesogens

A series of bent-shaped 4-cyanoresorcinol bisterephthalates is reported. Some of these achiral compounds spontaneously form a short-pitch heliconical lamellar liquid-crystalline phase with incommensurate 3-layer pitch and the helix axis parallel to the layer normal. It is observed at the paraelectric-(anti)ferroelectric transition, if it coincides with the transition from random to uniform tilt and with the transition from anticlinic to synclinic tilt correlation of the molecules in the layers of the developing tilted smectic phase. For compounds with long chains the heliconical phase is only field-induced, but once formed it is stable in a distinct temperature range, even after switching off the field. The presence of the helix changes the phase properties and the switching mechanism from the naturally preferred rotation around the molecular long axis, which reverses the chirality, to a precession on a cone, which retains the chirality. These observations are explained by diastereomeric relations between two coexisting modes of superstructural chirality. One is the layer chirality, resulting from the combination of tilt and polar order, and the other one is the helical twist evolving between the layers. At lower temperature the helical structure is replaced by a non-tilted and ferreoelectric switching lamellar phase, providing an alternative non-chiral way for the transition from anticlinic to synclinic tilt.