Salih Zeki Bas

Amperometric biosensors based on deposition of gold and platinum nanoparticles on polyvinylferrocene modified electrode for xanthine detection.

In this study, new xanthine biosensors, XO/Au/PVF/Pt and XO/Pt/PVF/Pt, based on electroless deposition of gold(Au) and platinum(Pt) nanoparticles on polyvinylferrocene(PVF) coated Pt electrode for detection of xanthine were presented. The amperometric responses of the enzyme electrodes were measured at the constant potential, which was due to the electrooxidation of enzymatically produced H(2)O(2). Compared with XO/PVF/Pt electrode, XO/Au/PVF/Pt and XO/Pt/PVF/Pt exhibited excellent electrocatalytic activity towards the oxidation of the analyte. Effect of Au and Pt nanoparticles was investigated by monitoring the response currents at the different deposition times and the different concentrations of KAuCl(4) and PtBr(2). Under the optimal conditions, the calibration curves of XO/Au/PVF/Pt and XO/Pt/PVF/Pt were obtained over the range of 2.5 × 10(-3) to 0.56 mM and 2.0 × 10(-3) to 0.66 mM, respectively. The detection limits were 7.5 × 10(-4)mM for XO/Au/PVF/Pt and 6.0 × 10(-4)mM for XO/Pt/PVF/Pt. The effects of interferents, the operational and the storage stabilities of the biosensors and the applicabilities of the proposed biosensors to the drug samples analysis were also evaluated.

Novel humic acid-bonded magnetite nanoparticles for protein immobilization

The present paper is the first report that introduces (i) a useful methodology for chemical immobilization of humic acid (HA) to aminopropyltriethoxysilane-functionalized magnetite iron oxide nanoparticles (APS-MNPs) and (ii) human serum albumin (HSA) binding to the obtained material (HA-APS-MNPs). The newly prepared magnetite nanoparticle was characterized by using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and elemental analysis. Results indicated that surface modification of the bare magnetite nanoparticles (MNPs) with aminopropyltriethoxysilane (APS) and HA was successfully performed. The protein binding studies that were evaluated in batch mode exhibited that HA-APS-MNPs could be efficiently used as a substrate for the binding of HSA from aqueous solutions. Usually, recovery values higher than 90% were found to be feasible by HA-APS-MNPs, while that value was around 2% and 70% in the cases of MNPs and APS-MNPs, respectively. Hence, the capacity of MNPs was found to be significantly improved by immobilization of HA. Furthermore, thermal degradation of HA-APS-MNPs and HSA bonded HA-APS-MNPs was evaluated in terms of the Horowitz-Metzger equation in order to determine kinetic parameters for thermal decomposition. Activation energies calculated for HA-APS-MNPs (20.74 kJmol(-1)) and HSA bonded HA-APS-MNPs (33.42 kJmol(-1)) implied chemical immobilization of HA to APS-MNPs, and tight interactions between HA and HA-APS-MNPs.

A gold nanoparticle functionalized multiwalled carbon nanotube–poly(o-phenylenediamine) composite film for glucose biosensing applications

A new biosensor based on immobilization of glucose oxidase on a multiwalled carbon nanotube–gold nanoparticle coated glassy carbon electrode (GCE) was fabricated for the electrochemical determination of glucose. First, a carboxylated multiwalled carbon nanotube (cMWCNT) was functionalized with 4-aminothiophenol (ATP) by a coupling agent, N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride, and then gold nanoparticles (AuNPs) were covalently linked to the ATP–cMWCNT via the formation of a covalent Au–S bond. Finally, glucose oxidase was immobilized simultaneously by the electropolymerization of o-phenylenediamine on the AuNP–ATP–cMWCNT coated GCE. The biosensor showed a linear range from 0.05 mM to 8.85 mM with a sensitivity of 27.93 μA mM−1 cm−2 and a detection limit of 0.015 mM for the detection of glucose. The biosensor was successfully applied to estimate the glucose concentration in human blood serum samples. Furthermore, the AuNP–ATP–cMWCNT was investigated for the non-enzymatic detection of hydrogen peroxide by using voltammetric and amperometric techniques, indicating a linear relationship in the range of 5 × 10−3 to 13.10 mM.

Electrochemical Sensing of Hydrogen Peroxide Using Block Copolymer Templated Iron Oxide Nanopatterns

A new enzyme-free sensor based on iron oxide (Fe3O4) nanodots fabricated on an indium tin oxide (ITO) substrate via a block copolymer template was developed for highly sensitive and selective detection of hydrogen peroxide (H2O2). The self-assembly-based process described here for Fe3O4 formation is a simple, cost-effective, and reproducible process. The H2O2 response of the fabricated electrodes was linear from 2.5 × 10-3 to 6.5 mM with a sensitivity of 191.6 μA mM-1cm-2 and a detection limit of 1.1 × 10-3 mM. The electrocatalytic activity of Fe3O4 nanodots toward the electroreduction of H2O2 was described by cyclic voltammetric and amperometric techniques. The sensor described here has a strong anti-interference ability to a variety of common biological and inorganic substances.

Synthesis, Characterization, and Spectroscopic Properties of a Symmetrical Schiff Base Ligand and its Bimetallic Complexes

This article presents the synthesis of new Schiff base ligand and preparation of its transition metal complexes with copper (II), nickel (II), zinc (II), and cobalt (II). Furthermore, absorption and fluorescence properties of ligand and its metal complexes are investigated. The effect of the solvents, such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, methanol, 1,4-dioxane on fluorescence properties of metal complexes, are performed and obtained results are summarized. All of the structures were characterized by using spectroscopic techniques.

Hypoxanthine Biosensor Based on Immobilization of Xanthine Oxidase on Modified Pt Electrode and Its Application for Fish Meat

In this study, hypoxanthine biosensor based on immobilization of xanthine oxidase on polyvinylferrocenium perchlorate matrix coated Pt electrode for detection of hypoxanthine was presented. The steady-state background current of the biosensor was measured at+0.5V, which was due to the electrooxidation of enzymatically produced H2O2. The biosensor exhibited a linear range from 2.15 × 10−3mM to 1.03mM (r = 0.9963) with a detection limit of 6.5 × 10−4mM (S/N = 3) for the detection of hypoxanthine. The storage stability of the biosensor, the effect of interference by uric acid, and the applicability to fish sample of the biosensor analysis were also evaluated.