فایل ورد کامل حسگرهای زیستی الکتروشیمیایی مبتنی بر نانوذرات طلای اصلاح شده با آنزیم

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تعداد صفحات این فایل: ۱۸ صفحه

بخشی از مقاله انگلیسیعنوان انگلیسی:Enzyme-modified nanoporous gold-based electrochemical biosensors~~en~~

Abstract

On the basis of the unique physical and chemical properties of nanoporous gold (NPG), which was obtained simply by dealloying Ag from Au/Ag alloy, an attempt was made in the present study to develop NPG-based electrochemical biosensors. The NPG-modified glassy carbon electrode (NPG/GCE) exhibited high-electrocatalytic activity toward the oxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2), which resulted in a remarkable decrease in the overpotential of NADH and H2O2 electro-oxidation when compared with the gold sheet electrode. The high density of edge-plane-like defective sites and large specific surface area of NPG should be responsible for the electrocatalytic behavior. Such electrocatalytic behavior of the NPG/GCE permitted effective low-potential amperometric biosensing of ethanol or glucose via the incorporation of alcohol dehydrogenase (ADH) or glucose oxidase (GOD) within the three-dimensional matrix of NPG. The ADH- and GOD-modified NPG-based biosensors showed good analytical performance for biosensing ethanol and glucose due to the clean, reproducible and uniformly distributed microstructure of NPG. The stabilization effect of NPG on the incorporated enzymes also made the constructed biosensors very stable. After 1 month storage at 4 °C, the ADH- and GOD-based biosensors lost only 5.0% and 4.2% of the original current response. All these indicated that NPG was a promising electrode material for biosensors construction.

۱ Introduction

lectrochemical sensors and/or biosensors has aroused the interest of analysts (Manso et al., 2008; Pingarron et al., 2008; Wang, 2005; Wang and Musameh, 2003; Zhou et al., 2008). As far as Au nanoparticles are concerned, the great enhancement in electrochemical response toward nicotinamide adenine dinuclcotide (NADH) and hydrogen peroxide at the Au nanoparticle-modified electrode makes them attractive for the construction of dehydrogenase- and oxidase-based biosensors (Jena and Raj, 2006; Manesh et al., 2008; Pingarron et al., 2008). It is now believed that the excellent catalytic activity of Au nanoparticles relies on the low-coordinated Au atoms, i.e., the atoms on the corners and edges (Hvolbk et al., 2007).

Nanoporous gold (NPG) is another kind of nanostructured gold. It possesses a three-dimensional spongy morphology with tunable pore and ligament sizes at nanometer scale (Ding et al., 2004; Xu et al., 2007). As compared with Au nanoparticle, NPG has a series of unique characteristics: (1) it is bulk in nature yet nanoscale in microstructure, which means it can be easily applied and recovered; (2) its pore size is tunable in a wide range from a few nanometers to many microns, which facilitates the study on the pore size-dependent effect; (3) prepared by simply dealloying Ag from Ag/Au alloys in concentrated HNO3, NPG has very clean surfaces, which eliminates the possible poisoning or passivating effects from unwanted molecules or ions such as polymer surfactants and Cl, as often used in Au nanoparticle preparation; (4) unlike Au particles, NPG avoids the particle aggregation, thus improving the stability of the NPG-based electrode and prolonging its lifetime.

In addition to its excellent catalytic activity (Xu et al., 2007; Yin et al., 2008; Zhang et al., 2007), NPG was also demonstrated to be a good carrier for biomacromolecule due to its well-ordered pore structure, high-specific surface area and high-specific pore volume (Qiu et al., 2008, 2009; Shulga et al., 2007). Compared with porous silica materials that are electronic semiconductors, NPG is an excellent conductor. Thus, for electrochemical sensors and/or biosensors construction, NPG may have some advantages over Au particles as well as porous silica. In this work, an attempt was made to construct NPG-based electrochemical biosensor. A comparison between the NPG-based biosensors and the gold sheet-based ones was also made to demonstrate the advantages of the NPG as an electrode material.

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