Amperometric Determination of Hydrogen Peroxide and its Mathematical Simulation for Horseradish Peroxidase Immobilized on a Sonogel Carbon Electrode

A mathematical model of a horseradish peroxidase biosensor was applied to simulate the amperometric response for the detection of hydrogen peroxide. The development of the mathematical model was based on the Michaelis–Menten equation and Fick’s Second Law. The theoretical study is based on the determination of physico-chemical and geometric parameters of a horseradish peroxidase biosensor as well as the kinetic parameters of reaction mechanism such as diffusion coefficients of hydrogen peroxide, the thickness of enzymatic layer, and the Michaelis–Menten kinetic constant. The theoretical analysis provides an accurate estimate of parameters affecting the biosensor performance such as the diffusion coefficient of hydrogen peroxide in the biomembrane that was estimated to be 56?×?10^?12 m²/s. The thickness of diffusion layer was estimated to be 80–100?µm and the biomembrane 7.5?µm. The experimental and numerical values of kinetic parameters were 0.92 and 0.98?µM for the Michaelis–Menten constants and 0.010 and 0.012?µM/s for the catalytic activity rates. The model was validated for hydrogen peroxide detection and exhibited a good agreement with the experimental measurements.     

Design and characterization of new advanced energetic biopolymers based on surface functionalized cellulosic materials

A new class of energetic biopolymers, which contain nitrate ester (O-NO₂) and nitramine (N-NO₂) as explosophoric groups, was successfully synthesized by surface modification of renewable pristine cellulose (PC) and microcrystalline cellulose (MCC) via epichlorohydrin-mediated amination followed by nitration process to produce new promising energetic aminated and nitrated cellulose and microcrystalline cellulose (APCN and AMCCN). Their structural, thermal, crystallinity and morphological features were examined and compared to those of the common cellulose nitrate. Furthermore, their energetic performances were evaluated by EXPLO5 V6.04 software. Experimental results confirm the successful chemical functionalization process to develop insensitive APCN and AMCCN with outstanding features such as nitrogen content of 15.01% and 15.39%, density of 1.692 g/cm³ and 1.708 g/cm³, and detonation velocity of 7526 m/s and 7752 m/s, respectively, which are significantly higher than those of the nitrated unmodified cellulosic biopolymers. The present investigation provides a suitable pathway to design new insensitive and energy-rich dense cellulosic biopolymers for potential application in high-performance solid propellants and composite explosives.

     

Mechanical,thermal, and UV‐shielding behavior of silane surface modified ZnO‐reinforced phthalonitrile nanocomposites

In the present work, zinc oxide nanoparticles were treated with aminopropyl trimethoxy silane‐coupling agent and used as a new kind of reinforcement for a typical high performance bisphenol‐A‐based phthalonitrile resin. The resulted nanocomposites were characterized for their mechanical, thermal, and optical properties. Results from the tensile test indicated that the tensile strength and modulus as well as the toughness state of the matrix were all enhanced with the increasing of the nanoparticles amount. Thermogravimetric analysis showed that the starting decomposition temperatures and the residual weight at 800°C were highly improved upon adding the nanofillers. At 6 wt% nanoloading, the glass transition temperature and the storage modulus were considerably enhanced reaching about 359°C and 3.7 GPa, respectively. The optical tests revealed that the neat resin possesses excellent UV‐shielding properties, which were further enhanced by adding the nanofillers. Furthermore, the fractured surfaces of the nanocomposites analyzed by scanning electron microscope exhibited homogeneous and rougher surfaces compared with that of the pristine resin. Finally, the good dispersion of the reinforcing phase into the matrix was confirmed by a high resolution transmission electron microscope. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of acid and alkali treatments of a forest waste,Pinus brutia cones,on adsorption efficiency of methyl green

The removal of methyl green (MG) dye from aqueous solutions using acid- or alkali-treated Pinus brutia cones (PBH and PBN) waste was investigated in this work. Adsorption removal of MG was conducted at natural pH, namely, 4.5 ± 0.10 for PBH and near 4.8 ± 0.10 for PBN. The pseudo-second-order model appeared to be the most appropriate to describe the adsorption process of MG on both PBN and PBH with a correlation coefficient R² > 0.999. Among the tested isotherm models, the Langmuir isotherm was found to be the most relevant to describe MG sorption onto modified P. brutia cones with a correlation factor R² > 0.999. The ionic strength (presence of other ions: Cl^?, Na⁺, and SO₄^2?) also influences the adsorption due to the change in the surface properties; it had a negative impact on the adsorption of MG on these two supports. A reduction of 68.5% of the adsorption capacity for an equilibrium dye concentration Ce of 30 mg/L was found for the PBH; while with PBN no significant influence of the ionic strength on adsorption was observed, especially in the presence of NaCl for dye concentrations superior to 120 mg L^?1.