Site selective electrodeposition of metals and conductive polymer nano-structures on isolated carbon nanopipes using ele
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Site selective electrodeposition of metals and conductive polymer nano-structures on isolated carbon nanopipes using electric fields
Jean-Claude Bradley, Sundar Babu and Patrick Ndungu Department of Chemistry, Drexel University, 32nd and Chestnut Streets, Philadelphia, PA 19104, U.S.A
ABSTRACT We report the successful application of bipolar electrochemistry for depositing metals and conducting polymer nano-structures on isolated template-grown carbon nanopipes (CVD-CNP). Metals such as tin, cobalt and nickel were reduced electrochemically at the tips of isolated CVDCNP from their chloride or nitrate salts. Polypyrrole dendrites could also be grown on both ends of selected CVD-CNP. The potential applications of thus encapsulated CVD-CNP in nanofluidics and other areas will be discussed.
INTRODUCTION Copper has been electrodeposited onto multi-walled carbon nanotubes (MWNT) in order to study the electrochemical behavior of the nanotubes [1]. Gold was electrodeposited onto singlewalled carbon nanotubes deposited across two prefabricated electrodes to study the contact resistance in a carbon nanotube field-effect transistor [2]. This approach however, required direct electrical contact to the nanotubes and lithography. A composite of nanotube/polypyrrole was synthesized by electropolymerization with potentials applications of the resulting composite in super capacitors, secondary batteries, and sensors [3]. Composites with superior wear resistance have also been synthesized by co-deposition of MWNT’s and nickel [4]. Bipolar electrochemistry refers to the generation of an anode-cathode pair on an isolated conductive substrate exposed to an external electric field [5]. We followed this method for synthesizing palladium supported on graphite platelets for use in catalysis [6]. Depositing metals and conducting polymers on carbon nanotubes by conventional electrodeposition results in encapsulating the nanotube completely. In contrast, targeted functionalizing of tips can be achieved by following the bipolar electrodeposition method. In this report we demonstrate the application of bipolar electrochemistry to deposit metals and conducting polymers onto selected tips of CVD-CNPs synthesized by a template assisted method or nanotubes obtained commercially.
EXPERIMENTAL DESCRIPTION Metals like cobalt and nickel were deposited on commercially available multiwalled nanotubes from NanoLab Inc. These nanotubes were 50nm (nominal) in diameter and 10µm (nominal) in length and they were used as received. CVD-CNPs of diameter 275±25nm were
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synthesized by the template assisted chemical vapor deposition method proposed by Martin et al [7]. Details of the template assisted synthesis process can be found elsewhere [8]. Deposited CVD-CNPs were then removed from the alumina template using 4.0 M sodium hydroxide. After separating the CVD-CNPs from the template they were rinsed with distilled water and acetone and suspended in toluene. Suspended CVD-CNPs and MWNT (~0.1µg/mL) were then immobilized on 13mm nuclepore track
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