Polymer Functionalized Carbon nanotubes for sensor application
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HH13.22.1
Polymer Functionalized Carbon nanotubes for sensor application Narasimha Harindra Vedala, Young C. Choi, X.Y.Zhou1, Gene Kim2, WonBong Choi Mechanical and Materials Engineering Department, Florida International University, 1 Hemispheric Center for Environmental Technology, Florida International University, Miami, FL 33174, U.S.A. 2 Motorola Inc, 8000 W. Sunrise Blvd, Fort Lauderdale, FL 33322, U.S.A. ABSTRACT Surface modification of carbon nanotubes with polyvinyl alcohol (PVOH) showed detection for humidity variation implying a possible application as a nanoscale humidity sensor. Wettability studies on single-wall, Y junction single wall and multiwall carbon nanotubes revealed that these nanotubes tend to become highly hydrophilic surfaces by this functionalisation. From the raman analysis it was determined that the majority of the nanotubes in our Y-junction single wall nanotubes were semiconducting in nature. The conductivity studies revealed that the Y junction nanotubes with PVOH functionalisation show large change in conductivity for varying relative humidity (RH). We propose a possible charge transport mechanism in these functionalized nanotubes.
INTRODUCTION The amazing material properties of carbon nanotubes have attracted their application in various fields including sensors, interconnects, field emission [1], and composites. Their large specific surface area and excellent electrical properties are the most promising features which are essential for developing nanoscale sensors. These sensors could have various advantages over the current micro sensors in terms of sensitivity and selectivity and operation conditions. Nanotubes have been shown to have high sensitivity for various toxic gases like ammonia [2] and organic vapors like ethanol [3]. Though the sensing mechanism is not clearly understood, it is proposed that the adsorption (physio or chemical) of analyte might result in doping the nanotubes with charged ions resulting in increase or decrease in conductance. Functionalisation of the nanotube is one the promising routes which not only enhances the sensitivity of nanotubes for various gases but also shows sensitivity to other gases and biomolecules which are otherwise undetected. It has been reported that by functionalizing nanotubes with polymers like Polyethylenemine and Nafion, high selective sensitivity to NO2 and NH3 respectively can be achieved [2]. Interaction of nanotubes with water molecule has also been investigated by several groups for understanding the effect on electrical properties of nanotube [4], or for flow behavior of water molecule inside the nanotube [5], or for application in humidity sensing [6] [7]. Polyvinyl alcohol (PVOH) is one of the polymers which have very good hygroscopic properties [8-11]. It consists of an OH group at every other carbon in the chain. It was proposed that the conductivity in PVOH depends upon the migration of hydrolyzed proton ions when water molecules are adsorbed [12]. Earlier works on PVOH functionalisation of nanotube was focused on im
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