Ahi Evran University

About: Ahi Evran University is a education organization based out in Kırşehir, Turkey. It is known for research contribution in the topics: Density functional theory & Ab initio. The organization has 842 authors who have published 2270 publications receiving 21904 citations.

Synthesis and characterization of a novel polyphosphazene and its application to biosensor in combination with a conducting polymer

Abstract: An amperometric glucose biosensor was prepared successfully based on a conducting polymer, poly(4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine) (poly(SNS-NH2)) and a flexible hydrophilic polyphosphazene polymer, poly[(methoxyethoxy)ethoxy-co-3-formylphenoxy]phosphazene (PPA). Poly(SNS-NH2) was electrochemically polymerized on a graphite electrode to achieve a conducting immobilization matrix to improve the enzyme immobilization on the transducer surface. Moreover, to strengthen the immobilization, a polyphosphazene derivate bearing functional aldehyde group was designed, synthesized and used in the immobilization of glucose oxidase. Not only the amino groups in the structure of poly(SNS-NH2), but also the aldehyde groups in PPA were contributed to the covalent immobilization as well as the entrapping the biomolecules in PPA network during the immobilization process. This afforded an effective and long-life analysis of glucose. Amperometric measurements were conducted at −0.7 V vs. Ag/AgCl in 50 mM sodium acetate buffer at pH 4.5. KMapp (0.677 mM), Imax (20.91 μA), LOD (1.3 μM) values were determined. Moreover, biosensor showed an extremely high sensitivity as 237.1 μA mM−1 cm−2 owing to the newly synthesized and combined highly flexible hydrophilic polymeric immobilization matrix. Finally, the proposed biosensor was successfully applied for determination of glucose content in several beverages, successfully.

Study on the electrical properties of ZnSe/Si heterojunction diode

Abstract: ZnSe thin film is e-beam evaporated on monocrystalline p-Si to fabricate n-ZnSe/p-Si heterojunction. The electrical properties were investigated by current–voltage (I–V), capacitance–voltage (C–V) and conductance–voltage (G/w–V) measurements. The forward bias I–V characteristics were analyzed in the temperature range of 220–360 K. The fabricated diode structure exhibited rectifying characteristics with a two order rectification ratio. The current transport in the junction was modeled by the modification of thermionic emission (TE) in which the observed anomaly was related to the interfacial disorder at the junction. From this analysis, the zero-bias barrier height and ideality factor at room temperature condition were determined as 0.775 and 3.195 eV, respectively. The TE anomaly was also evaluated by considering the fluctuations due to the barrier inhomogeneity and the assumption of Gaussian distribution in barrier height. Therefore, the forward bias I–V results were used to determine the density of interface states. The frequency dependence of C–V and G/w–V characteristics of the n-ZnSe/p-Si heterostructure were studied by taking into account of the effect of the series resistance and interface states at room temperature. According to the high-low frequency capacitance and Hill-Coleman methods, density of interface states was calculated and these experimental values were found in decreasing behavior with increasing frequency. The voltage and frequency dependence of series resistance values obtained from C–V and G/w–V measurements were also related to the insulator layer and the distribution density of interface states.