Boron-containing phenolic–siloxane hybrid polymers through facile click chemistry route

Realization of easily processable, tough phenolic functional polymer materials is of high demand for composite applications. Herein, we report the synthesis of boron-containing phenolic–siloxane hybrid polymers through a facile copper-catalysed azide–alkyne click chemistry (CuAAC) approach. For this, phenolic resoles incorporated with boron (PFB) was propargyl-derivatized and then bridged through triazole moieties using telechelic α, ω azidated polydimethylsiloxane (AZ-PDMS). The propargylated boronated PF (PFBPr) resins exhibited high heat of reaction during thermal cure due to the prevalence of multiple reactions. PFBPr-siloxane hybrid co-polymers exhibited glass transitions in the ranges – 100 to – 75 °C and at 25–35 °C corresponding to soft segment and hard segments. Pyrolysed PFBPr-siloxane products showed mixed phase heterogeneous systems of B and SiC. Introduction of boron and silicon improved the degree of graphitization and reduced the graphite crystallite size of the carbonization products. The pyrolysed compounds of silicon and boron formed during high temperature were conducive for creating a layer of void-free graphitic ordered carbon that improved with boron and silicon content, as revealed by SEM images.     

119Sn magic angle spinning NMR of nanocrystalline SnO2

Nanocrystalline SnO2 samples of different grain sizes, prepared by inert gas condensation technique (IGCT) and chemical precipitation method and conforming to the tetragonal phase, have been studied by variable speed (3-10 kHz) 119Sn MAS NMR at 11.74 Tesla field. 119Sn solid-state NMR results show that the IGCT prepared samples have good crystallinity and phase purity compared to the samples prepared by the chemical method. The determination of 119Sn chemical shielding parameters (delta iso, delta delta and eta) from slow MAS spectra shows that the 119Sn isotropic chemical shift (delta iso) is strongly influenced at smaller grain sizes, attributable to the change in the O2- local symmetry for the surface 119Sn ions at smaller grain sizes. The observed line widths in MAS spectra are significantly larger than the life-time broadening due to spin-lattice (T1) and spin-spin (T2) relaxation. The 119Sn MAS NMR spectra are thus inhomogeneously broadened by a distribution of isotropic chemical shifts, the line broadening increasing with decrease in grain size.     

Removal of dyes from a synthetic textile dye effluent by biosorption on apple pomace and wheat straw

This paper deals with two low-cost, locally available, renewable biosorbents; apple pomace and wheat straw for textile dye removal. Experiments at total dye concentrations of 10, 20, 30, 40, 50, 100, 150, and 200 mg/l were carried out with a synthetic effluent consisting of an equal mixture of five textile dyes. The effect of initial dye concentration, biosorbent particle size, quantity of biosorbent, effective adsorbance, dye removal and the applicability of the Langmuir and Freundlich isotherms were examined. One gram apple pomace was found to be a better biosorbent, removing 81% of dyes from the synthetic effluent at a particle size of 2 mm x 4 mm and 91% at 600 microm. Adsorption of dyes by apple pomace occurred at a faster rate in comparison to wheat straw. Both the isotherms were found to be applicable in the case of dye adsorption using apple pomace.     

Differential nano-bio interactions and toxicity effects of pristine versus functionalized graphene

We report the effect of carboxyl functionalization of graphene in pacifying its strong hydrophobic interaction with cells and associated toxic effects. Pristine graphene was found to accumulate on the cell membrane causing high oxidative stress leading to apoptosis, whereas carboxyl functionalized hydrophilic graphene was internalized by the cells without causing any toxicity.     

A comparative study of the tensile properties of compression molded and 3D printed PLA specimens in dry and water saturated conditions

Journal of Mechanical Science and Technology - This research work presents a comparative study of the tensile properties of polylactic acid (PLA) specimens per ASTM D638-14 fabricated by...     

Surface energy and separation mechanics of droplet interface phospholipid bilayers

Droplet interface bilayers are a convenient model system to study the physio-chemical properties of phospholipid bilayers, the major component of the cell membrane. The mechanical response of these bilayers to various external mechanical stimuli is an active area of research because of its implications for cellular viability and the development of artificial cells. In this article, we characterize the separation mechanics of droplet interface bilayers under step strain using a combination of experiments and numerical modelling. Initially, we show that the bilayer surface energy can be obtained using principles of energy conservation. Subsequently, we subject the system to a step strain by separating the drops in a step-wise manner, and track the evolution of the bilayer contact angle and radius. The relaxation time of the bilayer contact angle and radius along with the decay magnitude of the bilayer radius were observed to increase with each separation step. By analysing the forces acting on the bilayer and the rate of separation, we show that the bilayer separates primarily through the peeling process with the dominant resistance to separation coming from viscous dissipation associated with corner flows. Finally, we explain the intrinsic features of the observed bilayer separation by means of a mathematical model comprising the Young–Laplace equation and an evolution equation. We believe that the reported experimental and numerical results extend the scientific understanding of lipid bilayer mechanics, and that the developed experimental and numerical tools offer a convenient platform to study the mechanics of other types of bilayers.     

Highly Sensitive Electro‐Plasmonic Switches Based on Fivefold Stellate Polyhedral Gold Nanoparticles

Electron–photon coupling in metal nanostructures has raised a new trend for active plasmonic switch devices in both fundamental understanding and technological applications. However, low sensitivity switches with an on/off ratio less than 5 have restricted applications. In this work, an electrically modulated plasmonic switch based on a surface‐enhanced Raman spectroscopy (SERS) system with a single fivefold stellate polyhedral gold nanoparticle (FSPAuNP) is reported. The reversible switch of the SERS signal shows high sensitivity with an on/off ratio larger than 30. Such a high on/off ratio arises primarily from the plasmonic resonance shift of the FSPAuNP with the incident laser due to the altered free electron density on the nanoparticle under an applied electrochemical potential. This highly sensitive electro‐plasmonic switch may enable further development of plasmonic devices.