Application of diazo-thiourea and gold nano-particles in the design of a highly sensitive and selective DNA biosensor

An effective procedure for constructing a DNA biosensor is developed based on covalent immobilization of NH_2 labeled,single strand DNA(NH_2-ssDNA) onto a self-assembled diazo-thiourea and gold nanoparticles modified Au electrode(diazo-thiourea/GNM/Au).Gold nano-particles expand the electrode surface area and increase the amount of immobilized thiourea and single stranded DNA(ssDNA) onto the electrode surface.Diazo-thiourea film provides a surface with high conductibility for electron transfer and a bed for the covalent coupling of NH_2-ssDNA onto the electrode surface.The immobilization and hybridization of the probe DNA on the modified electrode is studied by differential pulse voltammetry(DPV) using methylene blue(MB) as a well-known electrochemical hybridization indicator.The linear range for the determination of complementary target ssDNA is from 9.5(±0.1) × 10~(-13) mol/L to1.2(±0.2) x 10~(-9) mol/L with a detection limit of 1.2(±0.1) 10~(-13) mol/L.     

A study of a simulated low Earth environment on the degradation of FEP polymer

Spacecraft flying in a low Earth orbit environment require thermal blankets to provide protection from direct solar heat from the sun. Fluorinated ethylene propylene copolymer is one of the major components of these thermal blankets. In this study, the effect of a simulated low Earth orbit environment on FEP was investigated. UV and VUV degradation of fluorinated ethylene propylene (FEP) copolymer was studied using ESR and XPS. The ESR study revealed the formation of a terminal polymer chain radical. The stability of this radical has been investigated under different environments. An XPS study of FEP film exposed to VUV and atomic oxygen showed that oxidation takes place on the polymer surface. The study revealed also that the percentage of CF₂ in the polymer surface decreased with exposure time and the percentage of CF, CF₃ and carbon attached to oxygen increased. SEM micrographs of FEP film exposed to VUV and atomic oxygen produced a rough surface with regular undulations similar to sand dunes. © 1998 John Wiley & Sons, Ltd.     

Electrochemical Sensing of Uric Acid Using a ZnO/Graphene Nanocomposite Modified Graphite Screen Printed Electrode

Russian Journal of Electrochemistry - An electrochemical sensor has been fabricated using ZnO/GR nanocomposite for selective determination of uric acid (UA) in a phosphate buffer solution (PBS, pH...     

Impact of MHD on hybrid nanomaterial free convective flow within a permeable region

Journal of Thermal Analysis and Calorimetry - Computational modeling was employed to scrutinize the nanomaterial influence of flow patterns and thermal treatment within a porous region....     

The double negation of the intermediate value theorem

In the context of intuitionistic analysis, we consider the set F consisting of all continuous functions ? from [0,1] to R such that ?(0)=0 and ?(1)=1, and the set I₀ consisting of ?’s in F where there exists x∈[0,1] such that . It is well-known that there are weak counterexamples to the intermediate value theorem, and with Brouwer’s continuity principle we have I₀≠F. However, there exists no satisfying answer to . We try to answer to this question by reducing it to a schema (which we call ) about intuitionistic decidability that asserts “there exists an intuitionistically enumerable set that is not intuitionistically decidable”. We also introduce the notion of strong Specker double sequence, and prove that the existence of such a double sequence is equivalent to the existence of a function ?∈F_mon where .     

Current trends in direct transformation of waste printed circuit boards (WPCBs) into value-added materials and products

1. Download : Download high-res image (174KB)
2. Download : Download full-size image

     

Investigation of Electrochemical Oxidation of Methanol at a Carbon Paste Electrode Modified with Ni(II)‐BS Complex and Reduced Graphene Oxide Nano Sheets

In the present research, the electro oxidation of methanol was investigated by different electrochemical methods at a carbon paste electrode (CPE) modified with bis(salicylaldehyde)‐nickel(II)‐dihydrate complex (Ni(II)‐BS) and reduced graphene oxide (RGO) (which named Ni(II)‐BS/RGO/CPE) in an alkaline solution. This modified electrode showed very efficient activity for oxidation of methanol. It was found that methanol was oxidized by NiOOH groups generated by further electrochemical oxidation of nickel (II) hydroxide on the surface of the modified electrode. The rate constant and electron transfer coefficient were calculated to be 2.18 s^?1 and 0.4, respectively. The anodic peak currents revealed a linear dependency with the square root of scan rate. This behaviour is the characteristic of a diffusion controlled process, so the diffusion coefficient of methanol was found to be 1.16×10^?5 cm² s^?1 and the number of transferred electron was calculated to be 1. Moreover, differential pulse voltammetry (DPV) investigations showed that the peak current values were proportional to the concentration of methanol in two linear ranges. The obtained linear ranges were from 0.5 to 100.0 µM (R²=0.991) and 400.0 to 1300.0 µM (R²=0.992), and the detection limit was found to be 0.19 µM for methanol determination. Generally, the Ni(II)‐BS/RGO/CPE sensor was used for determination of methanol in an industrial ethanol solution containing 4.0 % methanol.     

A Highly Sensitive Sensor Based on Reduced Graphene Oxide,Carbon Nanotube and a Co(II) Complex Modified Carbon Paste Electrode: Simultaneous Determination of Isoprenaline,Captopril and Tryptophan

This paper describes the development of a reduced graphene oxide (RGO), carbon nanotube (CNT) and Co(II) complex (cobalt(II) bis (benzoylacetone) ethylenediimino) (CBE) modified carbon paste electrode (CPE) for simultaneous determination of isoprenaline (IP), captopril (CAP) and tryptophan (Try). A pair of well‐defined redox peaks of Co(II) complex were obtained through a direct electron transfer between the Co(II) complex and the CPE. The proposed sensor showed very efficient electrocatalytic activity for anodic oxidation of IP in a 0.1 M phosphate buffer solution (pH 7.0). Square wave voltammetry (SWV) exhibited two linear dynamic ranges of 0.125–30.0 µM and 30.0–300.0 µM for IP. The detection limit for IP was found to be 50 nM. The proposed sensor was successfully applied for the determination of IP in real samples such as human blood serum, urine and IP ampoule.     

Effect of a novel green modification of alumina nanoparticles on the curing kinetics and electrical insulation properties of epoxy composites

A novel green surface modification was successfully implemented on alumina nanoparticles using chitosan (CS) to prevent nanoparticles' aggregation. To evaluate the surface changes of nanoparticles, FTIR, TGA, TEM, and SEM analyses were used. The cure kinetics of the uncured samples was analyzed by DSC. Different methods such as KAS, Friedman, Starink, and FWO were applied to measure the activation energy. The activation energy of epoxy reinforced with chitosan-functionalized alumina (epoxy/[CS-EPO-alumina]) was less than that of epoxy reinforced with alumina (epoxy/alumina), which was a confirmation of the positive effect of CS on curing reaction kinetics. Using the Malek method, the Sestak-Berggren autocatalytic equation was chosen to investigate the cure kinetics of the epoxy. It was found that the Sestak-Berggren equation is well matched with the experimental data and the model was suitable to predict the epoxy curing reaction reliably. Moreover, the glass transition temperatures of all samples were approximately the same. The effect of surface modification of alumina on the electrical insulating behavior of epoxy was also studied. It was found that CS functionalized alumina (CS-EPO-alumina) increased volume resistivity of epoxy at a temperature range of 30 to 80°C more than that of alumina. Electric stability and breakdown strength of epoxy/alumina and epoxy/(CS-EPO-alumina) also enhanced, where epoxy/(CS-EPO-alumina) experienced a further increase compared to epoxy.