Direct Electron Transfer at a Glucose Oxidase–Chitosan-Modified Vulcan Carbon Paste Electrode for Electrochemical Biosensing of Glucose

This article describes the investigation of direct electron transfer (DET) between glucose oxidase (GOD) and the electrode materials in an enzyme-catalyzed reaction for the development of improved bioelectrocatalytic system. The GOD pedestal electrochemical reaction takes place by means of DET in a tailored Vulcan carbon paste electrode surfaces with GOD and chitosan (CS), allowing efficient electron transfer between the electrode and enzyme. The key understanding of the stability, biocatalytic activity, selectivity, and redox properties of these enzyme-based glucose biosensors is studied without using any reagents, and the properties are characterized using electrochemical techniques like cyclic voltammogram, amperometry, and electrochemical impedance spectroscopy. Furthermore, the interaction between the enzyme and the electrode surface is studied using ultraviolet–visible (UV–Vis) and Fourier transform infrared (FTIR) spectroscopy. The present glucose biosensor exhibited better linearity, limit of detection (LOD?=?0.37?±?0.02 mol/L) and a Michaelis–Menten constant of 0.40?±?0.01 mol/L. The proposed enzyme electrode exhibited excellent sensitivity, selectivity, reproducibility, and stability. This provides a simple “reagent-less” approach and efficient platform for the direct electrochemistry of GOD and developing novel bioelectrocatalytic systems.     

Polynomials hardly commuting with increasing bijections

Let I be an interval in the real line ℝ. Among the real polynomials that take I to I, we ask which ones do not commute with any increasing bijection of I other than identity. For this purely algebraic problem, the solution involves concepts in topological dynamics. Our main characterizations are in terms of full orbits of critical points and periodic points. Using these, we obtain simpler criterion, namely, that for no nontrivial subinterval K⊂I, the successive images {f ⁿ (K):n=0,1,2,…} form a pairwise disjoint collection. This problem is of interest in topological dynamics because it is about characterization of polynomials with unique self-topological-conjugacy.     

Actinides selective extractants coated magnetite nanoparticles for analytical applications

N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and bis(2-ethylhexy)phosphoric acid (HDEHP) were coated on Fe₃O₄ nanoparticles under different chemical conditions. The TODGA-coated magnetite nanoparticles (Fe₃O₄@TODGA) captured representative actinides Am(III) and Pu(IV) at 3–4 M HNO₃ with high efficiency. However, the HNO₃ induced pre-organization of TODGA, before coating on the magnetite nanoparticles, was found to be important for the sorption of Am(III) and Pu(IV) ions. The Fe₃O₄@HDEHP particles exhibited selectivity toward Pu(IV), and Am(III) did not sorb from 3 to 4 M HNO₃. The quantification of Pu(IV) preconcentrated on coated particles was carried out by removing the extractant coating in dioxane based scintillator, followed by liquid scintillation counting.

     

Thin film of poly(bis[2-(methacryloyloxy)ethyl]phosphate) grafted on surface of poly(ether sulfone) membrane for plutonium(IV)-selective alpha tracks registration in CR-39 detector

Journal of Radioanalytical and Nuclear Chemistry - To impart chemical selectivity in the solid state nuclear track detector based quantification of Pu(IV) ions, a thin film of polymer of...     

Supported liquid membrane based loading technique for thermal ionization mass spectrometry: an application to plutonium isotopic composition and concentration determination

Supported liquid membrane (SLM) was prepared by immobilizing the extractant tricaprylmethyl ammonium chloride (Aliquat-336) into the microporous poly(propylene) membrane. The formed SLM with optimize composition was found be selective toward Pu⁴⁺ ions over UO₂²⁺ and Am³⁺ ions in a wide range of high acid concentrations (3–7 mol L^?1 HNO₃). The composition of SLM was optimized by using varying proportions of Aliquat-336 with solvents/diluents such as dioctyl phthalate (DOP), 2-nitrophenyl octyl ether and tris(2-ethylhexyl) phosphate. Among these diluents, DOP was found to be stable and causing uniform distribution of the extractant on the membrane. The surface morphology was characterized by atomic force microscopy. Stability and change in physical structure of SLM was characterized by capillary flow porometry. The Pu pre-concentrated in SLM was used to find out isotopic composition and concentration of the plutonium with help of thermal ionization mass spectrometry. The SLM was found to be stable and amenable to routine analyses.