Design of nano webs for hybrid sensor devices
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Design of nano webs for hybrid sensor devices Nandhinee Radha Shanmugam1, Milin Nilesh Rana2 and Shalini Prasad1 1 Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, U.S.A. 2 Department of Molecular and Cell Biology, University of Texas at Dallas, Richardson, TX 75080, U.S.A. ABSTRACT Hybrid organic/inorganic nanostructures are engineered to function as two terminal devices with enhanced functionality. The devices are the building blocks for designing hybrid organic/inorganic circuits in the nanoscale. In our work, we have demonstrated the sensing capabilities of polymer nanocomposite thin films for designing nanoweb devices towards detection of biomolecules. Biomolecules with surface charge such as troponin-T were detected on this device by interfacing them with the polymer/metal composites. The change in electrical properties due to modulation in charge transport at the crossbar junction was identified as the measured electrical signal for designing switch based sensors. Nanotextured surface offers strong charge carrier transport and hence enhances the strength of the detected signal. The antibodyantigen interactions at the junction effectively modulate the charge transfer kinetics and modify the junction characteristics due to the surface potential associated with the organic molecules. The net change in surface charge can be measured either as changes in the diode current in the two terminal configuration or as changes in the source- drain current in the three terminal configuration. Detection sensitivity in the order of pg/mL was targeted by measuring the voltammetric current response (in microamperes). Keywords: polymer nanocomposites, thin films, charge transport, surface potential, voltammetry. INTRODUCTION Conducting polymer nanocomposites has recently emerged as promising candidate for many applications due to their easy processing, scalability and low cost [1, 2]. New hybrid functional materials derived from nanocomposites of conducting polymers and inorganic nanoparticles are of great interest for following reasons: i) ability to tailor their optical and electronic properties; ii) enhanced electron confinement and charge storage capabilities[3]; iii) stability of redox polymer matrix [4] and iv) presence of electron mediating nanoparticles [3]. These unique synergistic properties offers characteristics such as high sensitivity and improved charge transfer kinetics [5] much needed for designing an electrochemical sensor with bistable behavior. In our work, nanocomposites sandwiched between metal electrodes in a crossbar array pattern have been chosen for switch implementation. Electrode pattern enables sensor design with simple two-terminal device architecture and high dense region for building a biosensor. Among conducting polymers, Polypyrrole (PPy) and Polyaniline (PANI) are chosen for our design of hybrid sensor due to their tunable electrical conductivity, stability and biocompatibility [1]. The carbon atoms of the polymer chain in sp2 hybridized state gives rise to fo
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