Synthesis and Morphology Control of Carbon Nanotube/Polyaniline Composite for Chemical Sensing
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Synthesis and Morphology Control of Carbon Nanotube/Polyaniline Composite for Chemical Sensing Mengning Ding1,2 and Alexander Star1,2 1 U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA 15236, U.S.A. 2 Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A. ABSTRACT Composites of single-walled carbon nanotubes (SWNTs) and polyaniline (PAni) were synthesized using different approaches. SWNT/PAni nanocomposite with controlled core/shell morphology was achieved. Our chemical sensing tests showed that such core/shell morphology resulted in superior sensor performance, with an increased sensitivity to acetone vapors, and a reversible detection of hydrazine vapors. The reversible detection of parts-per-billion concentrations of hydrazine offers promise for a portable solid-state detector that has potential application in aerospace. INTRODUCTION Chemiresistor based on single-walled carbon nanotubes (SWNTs) network is an ideal chemical sensing platform due to many of unique SWNT properties such as high surface area, mechanical strength, chemical stability and electrical conductivity that change dramatically upon adsorption of analyte molecules.[1,2] Functionalization of SWNTs was usually employed in order to provide additional sensitivity or selectivity to a specific analyte. Among many functional additives, polyaniline (PAni) appeared to be extremely attractive because of their high sensitivities as sensing materials themselves.[3] The composites of carbon nanotubes and PAni were typically synthesized either by in situ polymerization of aniline in the nanotube suspension,[4, 5] or by electropolymerization on nanotube electrode,[6, 7] most with improved sensitivities to chemical gases such as ammonia.[4-6] The reported composites were based on both multi-walled carbon nanotubes (MWNTs) and SWNTs with different functionalities. Here we report the synthesis and chemical sensitivities of different SWNT-PAni composites, including SWNT-PAni mixture, SWNT-PAni nanoparticles, and SWNT/PAni core/shell nanocomposite. We demonstrate that with fine control of the composite morphology at nanoscale, advanced sensor performance could be achieved.
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EXPERIMENT Pristine single-walled carbon nanotubes (P2-SWNTs) were obtained from Carbon Solution Inc. 1-Pyrenesulfonic acid hydrate (1-PSA, C16H10O3S 噝 xH2O), aniline (C6H5NH2), ammonium persulfate ((NH4)2S2O8, ı98%) and organic solvents were purchased from Sigma Aldrich and used as received. 40-pin ceramic sidebraze (CERDIP) packages (cavity .310 × .310) were procured from Global Chip Materials, LLC. Polyaniline nanofibers (PAni NFs) were synthesized using a rapid-mixing method described previously.[8] Briefly, an aqueous solution of aniline (1.5 mmol) in 1M HCl (10 mL) and an aqueous solution of ammonium persulfate (0.4 mmol) were mixed together followed by vigorous stirring for 40 min. The final product was separated by centrifugation and washed with DI water, and then suspended into 20 mL of DI water. HCl or NaOH solutions (1 M) w
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