DOI: 10.1002/elan.201400266 Electrochemical Behavior of Glucose Oxidase Immobilized on Pd-Nanoparticles Decorated Ionic Liquid Derived Fibrillated Mesoporous Carbon Behzad Haghighi,* [a, b] Babak Karimi, [a] Mojtaba Tavahodi, [a] and Hesam Behzadneia [a] 1 Introduction In recent years, direct electrochemistry of biological mol- ecules such as enzymes has attracted considerable atten- tion due to its significance in fundamental and applied studies. The possibility of direct electron transfer (DET) between redox enzymes and electrode surface permits us to investigate the path of electron transfer (ET) in biolog- ical systems, to explore regularity mechanisms in meta- bolic pathways and also to fabricate new biosensors and biofuels [1, 2]. Glucose oxidase (GOx) as a redox protein has been widely used for the fabrication of different types of biosensors to monitor glucose level in diabetes pa- tients, food and beverage during manufacturing process. GOx exhibits a rather sluggish rate of heterogeneous electron transfer on electrode [3] in electrochemical in- vestigations, although its ET rate is fast in biological sys- tems. It seems that the deep embedding of the electroac- tive prosthetic group of GOx, flavin adenine dinucleotide (FAD), within the enzyme structure and/or the adsorptive denaturation of enzyme on the electrode surface as well as unfavorable orientation of enzyme on electrode are the main reasons for such sluggish rate. The mentioned concept can be extended to the other redox proteins. Var- ious nanostructure materials such as various kinds of metal and metal oxide nanoparticles [4], carbon nano- tubes [5] and mesoporous materials [6] have been utilized to modify the electrode surface in a way to improve the interaction between the redox center of the enzyme and the electrode surface and consequently to enhance the rate of electron transfer. In the past decade, ordered mesoporous carbons (OMCs) have attracted special attention in the field of electrochemistry because of their admirable chemical sta- bility, large surface area, tunable pore sizes and excellent conductivity [7]. The nanostructure and electric proper- ties of the mesoporous carbons depend on the source of carbon and the conditions of reaction medium [8]. Re- cently, a novel protocol for the synthesis of mesoporous carbon using ionic liquid as the source of carbon has been presented by Karimi et al. [9]. They showed that the re- sulting nanostructured carbons, so called ionic liquid de- rived fibrillated mesoporous carbon (IFMC), presented superior electrical conductivity and mechanical property. In addition to the nanostructured carbonous materials, there has been significant interest in the development of metal nanoparticles. Among different kinds of metal nanostructures, palladium nanoparticles (Pd-NPs) are of great interest due to their excellent electrical and catalyt- ic properties [10] and their extensive applications in bio- sensors [11, 12]. In this study, Pd-NPs decorated ionic liquid derived fi- brillated mesoporous carbon (Pd@IFMC) was prepared and used to modify the surface of a glassy carbon elec- trode (GCE) by simple drop casting. Then, a layer of GOx was immobilized on the surface of modified elec- trode (GCE/Pd@IFMC) to fabricate a glucose biosensor. The course of fabrication was optimized and the analyti- cal characteristics of the prepared glucose biosensor (GCE/Pd@IFMC/GOx/Nafion) were evaluated. Direct electron transfer of the immobilized GOx was efficiently [a] B. Haghighi, B. Karimi, M. Tavahodi, H. Behzadneia Department of Chemistry, Institute for Advanced Studies in Basic Sciences P.O. Box 45195-1159, Gava Zang, Zanjan, Iran *e-mail: haghighi@iasbs.ac.ir [b] B. Haghighi Department of Chemistry, College of Sciences Shiraz University, Shiraz 71454, Iran Abstract : Pd nanoparticles with an average diameter of 5 nm were decorated on the surface of ionic liquid de- rived fibrillated mesoporous carbon (IFMC) to prepare a novel nano-hybrid material (Pd@IFMC). Thereafter, glucose oxidase was immobilized on Pd@IFMC modified glassy carbon electrode to fabricate an enzymatic glucose biosensor. A pair of well-defined redox peaks was record- ed for direct electron transfer of the immobilized glucose oxidase at the formal potential of  0.418 V with a peak to peak separation of 25 mV. Electron transfer rate con- stant of was calculated to be 14.6 s 1 . The response of fab- ricated biosensor was linear towards glucose concentra- tion. Keywords: Pd nanoparticles · Ionic liquid derived fibrillated mesoporous carbon · Direct electron transfer · Glucose oxidase · Glucose biosensor www.electroanalysis.wiley-vch.de  2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2014, 26, 1 – 8 &1& These are not the final page numbers! ÞÞ Full Paper Downloaded from http://www.elearnica.ir