Sustainable approach on the biodegradation of azo dyes: A short review

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Immobilization of redox mediators on functionalized carbon nanotube: A material for chemical sensor fabrication and amperometric determination of hydrogen peroxide

Chemical functionalization of single-walled carbon nanotubes with redox mediators, namely, toluidine blue and thionin have been carried out and the performance of graphite electrode modified with functionalized carbon nanotubes is described. Mechanical immobilization of functionalized single-walled nanotube (SWNT) on graphite electrode was achieved by gently rubbing the electrode surface on carbon nanotubes supported on a glass slide. The electrochemical behaviour of the modified electrodes was investigated by cyclic voltammetry. The SWNT-modified electrodes showed excellent electrocatalytic effect for the reduction of hydrogen peroxide. A decrease in overvoltage was observed as well as an enhanced peak current compared to a bare graphite electrode for the reduction of hydrogen peroxide. The catalytic current was found to be directly proportional to the amount of hydrogen peroxide taken.     

Detection of Aluminum Chlorohydrate Content in Antiperspirant Deodorants Using Screen‐Printed Silver Electrodes by One Drop Analysis

Aluminum chlorohydrate (Al₂(OH)₅Cl?2H₂O, ACH) is an active ingredient in many antiperspirants and deodorants formulation to reduce the body odors (mainly sweat) through interaction with apocrine sweat glands to produce insoluble aluminum hydroxide and free chloride, which then plugs the sweat gland that stops the flow of sweat to the skin's surface. We demonstrated here an one drop (50 μL) electrochemical sensing of the ACH using an in‐built three screen‐printed electrodes assembly containing Ag as working and pseudo reference and carbon as counter electrode system (AgSPE). The free Cl^? ion librated from ACH/H₂O reaction was detected at AgSPE surface at 0.072 V vs. pseudo Ag reference electrode system in pH 2 phosphate solution by Cyclic voltammetric Technique. Under optimal working condition the AgSPE shows a linear calibration plot in the window of 30–2000 ppm of ACH with sensitivity and regression values of 0.104 μA/ppm and 0.998 respectively. Calculated detection limit is 3.03 ppm. RSD values of intra‐ and interassays were 0.19% and 2.79% respectively. Finally, real sample (antiperspirant deodorant lotions) assays were successfully demonstrated with results comparable to the predicted values.     

Ferrocene‐based organophosphorus liquid–crystalline polymers: Synthesis and characterization

Ferrocene‐containing polyphosphate and phosphonate esters were synthesized by the solution polycondensation method. The structure of the polymers was confirmed using various spectroscopic techniques. The formation of two types of chain blocks was confirmed by ³¹P NMR spectroscopy. Hot stage optical polarized microscope (HOPM) analysis revealed that all the polymers have a liquid–crystalline property. The char yields of the synthesized similar polymers were much higher than those of nonphosphorus polymers already reported in the literature. DSC analysis confirmed our predictions over the liquid–crystalline property, glass‐transition temperature, isotropization temperature, and thermal stability of the polymers. The effects of substitution on the side chain, structure of the liquid‐–crystalline phase, and thermal stability of the polymers have also been discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2396–2403, 2001     

Nafion–RuO2–Ru(bpy)3 composite electrodes for efficient electrocatalytic water oxidation

Electrocatalytic water oxidation to evolve O₂ was studied on a Nafion–RuO₂–Ru(bpy)₃²⁺ composite electrode. The O₂ evolution current efficiency was largely improved for the multi-component electrode over the Nafion–RuO₂ and Nafion–Ru(bpy)₃²⁺ individuals. The redox mediation through the Ru(bpy)₃²⁺ was found to dominate over the RuO₂ catalytic effect in the water oxidation mechanism. The specific surface area of the RuO₂, which was prepared at different temperatures (300–700°C), used in fabricating the composite electrode also played an important role in the overall water oxidation mechanism. Both the reaction and electrode parameters were optimized to get effective electrocatalytic current values in this study.     

A highly stable and sensitive chemically modified screen-printed electrode for sulfide analysis

We report here a highly stable and sensitive chemically modified screen-printed carbon electrode (CMSPE) for sulfide analysis. The CMSPE was prepared by first ion-exchanging ferricyanide into a Tosflex anion-exchange polymer and then sealing with a tetraethyl orthosilicate sol-gel layer. The sol-gel overlayer coating was crucial to stabilize the electron mediator (i.e., Fe(CN)₆³⁻) from leaching. The strong interaction between the oxy-hydroxy functional group of sol-gel and the hydrophilic sites of Tosflex makes the composite highly rigid to trap the ferricyanide mediator. An obvious electrocatalytic sulfide oxidation current signal at ∼0.20 V versus Ag/AgCl in pH 7 phosphate buffer solution was observed at the CMSPE. A linear calibration plot over a wide range of 0.1 μM to 1 mM with a slope of 5.6 nA/μM was obtained by flow injection analysis. The detection limit (S/N = 3) was 8.9 nM (i.e., 25.6 ppt). Practical utility of the system was applied to the determination of sulfide trapped from cigarette smoke and sulfide content in hot spring water.     

Preparation and characterization of LiNi<Subscript>0.495</Subscript>M<Subscript>0.01</Subscript>Mn<Subscript>0.495</Subscript>O<Subscript>2</Subscript> (M = Zn,Co, and Y) for lithium ion batteries

Layered structured LiNi_0.5Mn_0.5O₂ and LiNi_0.495M_0.01Mn_0.495O₂ (M = Zn, Co, and Y) compounds were prepared by PVP (poly(vinyl pyrrolidone))-assisted sol-gel method, and their structural, morphological, vibrational, transport, and electrochemical properties were characterized by XRD, SEM, FTIR, Raman, AC impedance, and galvanostatic charge and discharge analysis. XRD patterns reveal that doping does not change the crystal structure of the LiNi_0.5Mn_0.5O₂ compound. SEM images show that the average size of the particle is in sub-micron ranges. The AC impedance studies shows an electrical conductivity of ～2.5 × 10^?7 S/cm for the parent compound. The introduction of Zn/Co/Y at equivalent sites increased the electrical conductivity by one order ～10^?6 S/cm. The compound LiNi_0.495Co_0.01Mn_0.495O₂ shows the highest electrical conductivity of 2.85 × 10^?6 S/cm and delivers a specific discharge capacity of 110 mAh/g at the end of the 25th cycle in the voltage window of 2.5–4.4 V for a current density of 30 mA/g.     

Temperature-dependent carbon incorporation into the Si1−yCy film during gas-source molecular beam epitaxy using monomethylsilane

Coverage and adsorption state of hydrogen atoms on the growing surface of Si_1−yC_y film using monomethylsilane has been investigated by using temperature-programmed desorption (TPD) and multiple-internal-reflection Fourier-transform infrared spectroscopy (MIR-FT-IR). The surface hydrogen coverage decreases with the growth temperature T_g until it disappears at 800 °C. All the H₂-TPD spectra are well resolved into six SiH-related and one CH_n-related hydrogen desorption peaks. The SiH-related FT-IR peak showed a blue shift with increasing T_g, which, in conjunction with the TPD, is related to enhanced C incorporation at backbonds of SiH.     

Vortices and quasiparticles near the superconductor-insulator transition in thin films

We study the low temperature behavior of an amorphous superconducting film driven normal by a perpendicular magnetic-field (B). For this purpose we introduce a new two-fluid formulation consisting of fermionized field-induced vortices and electrically neutralized Bogoliubov quasiparticles (spinons) interacting via a long-ranged statistical interaction. This approach allows us to access a novel non-Fermi-liquid phase, which naturally interpolates between the low B superconductor and the high B normal metal. We discuss the properties of the resulting "vortex metal" phase.