Versatile fullerenes as sensor materials

The last century outstanding discovery of fullerenes (or C₆₀), as they are popularly called ‘buckyball’ structured molecules with icosahedral spherical structure, consists of 60 sp^2-hybridized carbon atoms. These fullerenes have created immense applications in various fields, such as catalysts, sensors, photocatalysts, energy production, and storage materials. Fullerenes because of their improved conductivity, charge transfer, and photophysical properties have gained considerable attention, particularly in sensor area. The activity of sensors depends upon the interactions between fullerene and the sensing material. Among all the types of fullerenes, C₆₀ has been extensively used. This review is an attempt to cover different aspects of fullerene-based sensing devices, wherein fullerenes act as important component (s) of the sensor device because of their electron-accepting properties. We will discuss the fullerene-based sensors for diverse applications as strain/gas sensors, electrochemical sensors, and optical sensors as much effort has been recently made to detect different analytes such as gases, volatile organic compounds, metal ions, anions, and biomolecules.     

A Remarkably Efficient MnFe2O4‐based Oxidase Nanozyme

Nanomaterials‐based enzyme mimetics (nanozymes) have attracted considerable interest due to their applications in imaging, diagnostics, and therapeutic treatments. Particularly, metal‐oxide nanozymes have been shown to mimic the interesting redox properties and biological activities of metalloenzymes. Here we describe an efficient synthesis of MnFe₂O₄ nanomaterials and show how the morphology can be controlled by using a simple co‐precipitation method. The nanomaterials prepared by this method exhibit a remarkable oxidase‐like activity. Interestingly, the activity is morphology‐dependent, with nanooctahedra (NOh) exhibiting a catalytic efficiency of 2.21×10⁹ m ^?1 s^?1, the highest activity ever reported for a nanozyme.     

A nonlinear fractional model to describe the population dynamics of two interacting species

In this paper, the approximate analytical solutions of Lotka–Volterra model with fractional derivative have been obtained by using hybrid analytic approach. This approach is amalgamation of homotopy analysis method, Laplace transform, and homotopy polynomials. First, we present an alternative framework of the method that can be used simply and effectively to handle nonlinear problems arising in several physical phenomena. Then, existence and uniqueness of solutions for the fractional Lotka–Volterra equations are discussed. We also carry out a detailed analysis on the stability of equilibrium. Further, we have derived the approximate solutions of predator and prey populations for different particular cases by using initial values. The numerical simulations of the result are depicted through different graphical representations showing that this hybrid analytic method is reliable and powerful method to solve linear and nonlinear fractional models arising in science and engineering. Copyright © 2017 John Wiley & Sons, Ltd.     

Synergistic effect of hybrid graphene and boron nitride on the cure kinetics and thermal conductivity of epoxy adhesives

In the present study, the synergistic effect of hybrid boron nitride (BN) with graphene on the thermal conductivity of epoxy adhesives has been reported. Graphene was prepared by chemical reduction of graphite oxide (GO) in a mixture of concentrated H₂SO₄/H₃PO₄ acid. The particle size distribution of GO was found to be ~10 μm and a low contact angle of 54° with water indicated a hydrophilic surface. The structure of prepared graphene was characterized by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), Raman spectroscopy and atomic force microscopy (AFM). The thermal conductivity of adhesives was measured using guarded hot plate technique. Test results indicated an improvement in the thermal conductivity up to 1.65 W/mK, which was about ninefold increase over pristine epoxy. Mechanical properties of different epoxy formulations were also measured employing lap shear test. The surface characterization of different epoxy adhesive systems was characterized through XRD, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies. Fourier transform infrared also served to determine the nature of interactions between filler particles and epoxy resin. Non‐isothermal differential scanning calorimetric (DSC) technique was used to investigate the effects of graphene and BN particles on the cure kinetics and cross‐linking reaction of epoxy cured with amine curing agent. The Kissinger equation, the model‐free isoconversional Flynn–Wall–Ozawa method and the Ozawa model were used to analyze the kinetic parameter. Copyright © 2017 John Wiley & Sons, Ltd.     

Comparative analysis of the spectrophotometry based total phenolic acid estimation methods

This paper proposes a total phenolic acid estimation technique for samples with unknown phenolic acid composition and preliminary sample screening in resource-constrained settings. Phenolic acids constitute one of the important secondary metabolites for industry and researchers, but appropriate technique for its estimation by rural entrepreneurs is unclear. This study compared spectrophotometric Arnov test (AT) and potassium iodate test (PT) on the basis of seven parameters namely input requirements, process, limit of detection (LOD), limit of quantification (LOQ), linearity range, interferences and different phenolic compounds response. As per the results of the study PT is better than AT in input requirements, process, interference and different phenolic compounds response whereas AT is better than PT in LOD, LOQ and linearity range. Therefore, the study concluded that PT could be more suitable for rural entrepreneurs.     

Guerbet alcohol esters: Practical synthesis and applications

Guerbet alcohols are primary alcohols with beta branching and have lower melting point than their linear counterpart. Due to presence of branching, the products are liquid at lower temperatures; they have low volatility and exhibit better color and oxidation stability. The main advantage of the Guerbet branching material is their biodegradability. Present research work was carried out on synthesis of branch chain alcohols with varying hydrocarbon chain lengths. The main purpose was to study the effects of branching and varying chain length with performance properties. Branch chain esters with mono and di-carboxylic acids were synthesized with varying hydrocarbon chain lengths. The major limitation of Guerbet products is their cost. Guerbet alcohols were esterified with various monobasic and dibasic acids and found to have lower pour points. Load carrying capacity of prepared ester increased with increase in carbon chain. Wear scar of the prepared ester decreased with the increase in carbon number of ester molecule. These properties indicated their potential use as lubricating oil base stock which are environment friendly as they are biodegradable and with excellent liquidity.     

A simplified model of oscillating electrolytes

Unstable electrophoretic transport leading to oscillations in concentration profiles occur in certain electrolyte systems known as oscillating electrolytes whose eigenmobilities are complex valued. The study of the nonlinear behavior of such systems is of great interest but is constrained due to a high degree of complexity in the governing equations. Here we present a simplified model of unstable electrophoretic transport in a binary system that reduces the governing equations to two partial differential equations only and does away with other equations that characterize acid–base dissociation reactions and electroneutrality. We present analytical expressions for electromigration fluxes and validate the model with full nonlinear simulations. The model exhibits similar nonlinear behavior as the actual unstable electrophoretic system under various initial disturbances. For comparison, we also show that similar modeling for a stable system predicts concentration profiles that quantitatively agree with its nonoscillating dynamics. Moreover, the unique feature of electromigration flux in oscillating electrolytes that unfolds from the modeling led us to find an elegant explanation of the instability mechanism. Our theory gives a qualitative understanding of the existence and growth of large oscillation patterns in oscillating electrolytes.     

Extended Corannulenes: Aromatic Bowl/Sheet Hybridization

Among sheet/sheet polynuclear aromatic hydrocarbon (PAH) hybrids, a buckybowl–graphene hybrid has been used as a model to explore the effects of physical properties of PAHs with distinct planar and bowl regions. Activation of a C(Ar)? F bond was used to synthesize this corannulene/graphenic hybrid. Photophysical and voltammetric studies together with high‐level computations revealed curvature and extended π‐effects on the properties of these materials.     

Transition metal-free activation of allylic acetates toward regioselective S-allylation of thiols

Allylic acetates have been used as allylating agents under transition metal-free condition toward an economical and sustainable regioselective S-allylation of aromatic and aliphatic thiols in the presence of potassium carbonate in DMF.     

Stereoselective construction of quaternary chiral centers using Ti(III)-mediated opening of 2,3-epoxy alcohols: studies directed toward the synthesis of penifulvins

A trisubstituted α,β-unsaturated ester moiety was suitably placed in a molecule also bearing an epoxy alcohol moiety at its other end to intramolecularly trap the intermediate radical, which was formed when the molecule was treated with Cp₂Ti(III)Cl to regio- and stereoselectively open its epoxy ring, giving rise to a quaternary chiral center. The method was subsequently used in an attempt to construct the bicyclic core framework of potent insecticides penifulvins.