A novel graphene-chitosan-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocomposite modified sensor for sensitive and selective electrochemical determination of a monoamine neurotransmitter epinephrine

A novel sensitive electrochemical sensor has been developed by modification of glassy carbon electrode (GCE) with graphene (GRP), chitosan (CHIT), and bismuth oxide (Bi₂O₃) nanoparticles. The morphological characteristics of nanocomposite (GRP-CHIT-Bi₂O₃ or GCB) were studied by scanning electron microscope and atomic force microscopy. The electrochemical behavior of epinephrine at nanocomposite modified GCE (GCB/GCE) was investigated in pH 7.4 phosphate buffer solution using cyclic voltammetry and square wave voltammetry. GCB/GCE showed an enhancement in the current response as compared to bare GCE. Electrochemical impedance spectra showed a reduction of charge transfer resistance and higher electrocatalytic behavior of the sensor. The electrooxidation process of epinephrine at the modified sensor was found to be diffusion controlled. GCB/GCE showed a linear response to epinephrine in the range 100 to 500 nM. The limit of detection and limit of quantification were found to be 3.56 and 11.85 nM, respectively, which is lower than many other sensors reported for epinephrine in literature. The modified sensor showed high sensitivity (1.3 nA/nM) and selectivity for epinephrine. The method was employed for quantification of epinephrine in pharmaceutical formulation and human blood serum samples.     

Characterization of novel natural cellulosic fibers from purple bauhinia for potential reinforcement in polymer composites

Cellulose - The aim of the present work was to extract novel natural cellulosic fibers from the leaves of purple bauhinia trees. To the best of our knowledge, this is the first time that, the...     

Thermal kinetics and morphological investigation of alkaline treated rice husk biomass

Agro waste bio mass are creating challenges for environment in term of air pollution due to improper disposal. Rice milling is the process in which rice husk is produced as by-product. The agro-waste rice husk has tremendous potential to be used either in its raw form or in ash form. The inherent component of this waste cellulose provides enhanced properties in a reinforced composite when used as filler. Rice husk is the hard outer layer and covering rice seed, which makes reinforcement challenging in its original form. Fiber surface treatment significantly improves adhesion with matrix and various thermo chemical properties of filler as well as of composites. NaOH treatment is cost-effective and it ensures the adhesion with matrix by removal of hemicellulose and lignin. The chemical treatment of agro-waste (rice husk) is performed with 5% alkali solutions of NaOH in water. Results are compared with the properties of untreated rice husk for thermal and morphological characterizations. In the present work, we are trying to quantify the impact of chemical treatment on rice husk thermal decomposition and its kinetics. Thermogravimetric analysis and kinetics study of thermal degradation, provide key input towards pyrolysis pattern of rice husk, while FTIR and SEM analysis provide the prospects of this bio filler using a reinforcing agent to develop green composite and productive disposal. The FTIR data helps to find the possibilities of blending different bio fillers and natural fibers to find suitable reinforcing substances. The average activation energy of treated fiber is noted as 137.95 by KAS method and 108.08 by FWO method as compared to 55.56 by KAS method & 54.26 by FWO method for untreated rice husk.     

ZrO2-Graphene-Chitosan nanocomposite modified carbon paste sensor for sensitive and selective determination of dopamine

A sensitive and stable electrochemical sensor was developed by modification of carbon paste electrode with ZrO₂/graphene/chitosan nanocomposite. The modified sensor served as a potential electrocatalytic platform for dopamine. Electrochemical impedance spectroscopy studies indicated reduction of charge transfer resistance at the modified electrode surface thereby facilitating the electron transfer process which resulted in higher current response to dopamine. The electrochemical behavior of dopamine at the modified electrode was studied using cyclic and square wave voltammetry. The maximum current response for the electro-oxidation of dopamine was observed at pH 7.4 and the process was realized to be diffusion controlled. The modified sensor demonstrated linearity in the range 1000–5000 nM, with high sensitivity (22 nA/nM), detection limit of 11.3 nM and selectivity for dopamine in the presence of ascorbic and uric acid which are found to co-exist with dopamine in physiological media. The method was employed for quantification of dopamine in a pharmaceutical formulation.