Label-free Electrochemical Biosensor Based on Graphene/Ionic Liquid Nanocomposite for the Detection of Organophosphate P
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Label-free Electrochemical Biosensor Based on Graphene/Ionic Liquid Nanocomposite for the Detection of Organophosphate Pesticides Tae Jung Park1, MinHo Yang2, Bong Gill Choi2, Nam Su Heo1, Seok Jae Lee3, Won Hi Hong2, and Sang Yup Lee1,2,4 1
BioProcess Engineering Research Center, Center for Systems & Synthetic Biotechnology, and Institute for the BioCentury, KAIST, Daejeon 305-701, Republic of Korea 2 Department of Chemical & Biomolecular Engineering (BK21 program), KAIST, Daejeon 305701, Republic of Korea 3 NTD&I Team, National Nanofab Center, Daejeon 305-806, Republic of Korea 4 Department of Bio & Brain Engineering, Department of Biological Sciences, and Bioinformatics Research Center, KAIST, Daejeon 305-701, Republic of Korea ABSTRACT The advanced electrodes for detecting organophosphate pesticides were prepared by modification of the gold (Au) electrode with the reduced graphene oxide/ionic liquid (RGO/IL) nanohybrids. Due to the cationic and anionic parts, the ILs on RGO sheets provide the amount of functional groups for dispersion of hybrids and immobilization of organophosphorus hydrolase (OPH) enzymes. After the immobilization of OPH on the RGO/IL-modified Au electrodes, the modified electrodes represent faster electron transfer than that of Au electrode, resulting in high performance of biosensor with response time (~ 10 s) and sensitivity (4.56 nA μM−1). In addition, the OPH/RGO/IL-modified Au electrode displayed good stability and reproducibility. INTRODUCTION Organophosphate (OP) chemical is the most toxic substance, which is commonly used as pesticides in agriculture and can be a potential use as chemical warfare agents1. To detect OP compounds, electrochemical biosensors in particular have been widely investigated with using carbon nanotubes (CNTs) due to their large accessible surface area, electronic conductivity, and capacity to immobilize enzymes2. Although CNT is an attractive material for application to electrochemical devices, it is difficult to process into applications due to its tangled bundles and high cost. The recent discovery of graphene has triggered enormous interest both in academic studies and biotechnological applications, due to its physicochemical and electrochemical properties. Two-dimensional lattice of a single layer of carbon atoms in graphene provides a more affordable alternative to CNT in applications of field effect transistors, high sensitive sensors, microelectrical devices, and nanocomposites3. Here, we present the fabrication and characterization of electrochemical sensor for OP chemicals based on the electrode using reduced graphene oxide (RGO)/ionic liquid (IL) composite. EXPERIMENTS Graphite oxide was synthesized from graphite by a modified Hummers method4 and a reduced graphite oxide was then obtained by chemical reduction of hydrazine solution. A total of 1 mg of RGO was added to 1 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) as an IL. A volume of 5 μL of the resulting reduced graphite oxide coated with [bmim][PF6] was dropped onto the gol
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