synergistic effects in the gas sensitivity of polypyrrolesingle wall carbon nanotube composites协同效应的气体灵敏度polypyrrolesingle壁碳纳米管复合材料.pdf

Sensors 2012, 12, 7965-7974; doi:10.3390/s120607965 OPEN ACCESS sensors ISSN 1424-8220 /journal/sensors Article Synergistic Effects in the Gas Sensitivity of Polypyrrole/Single Wall Carbon Nanotube Composites Duong Ngoc Huyen *, Nguyen Trong Tung, Tran Dinh Vinh and Nguyen Duc Thien School of Engineering Physics, Hanoi University of Science and Technology, No.1, Daicoviet, Hanoi 10000, Vietnam; E-Mails: trongtung227@ (N.T.T.); trandinhvinhht@ (T.D.V.); ducthien_ly@ (N.D.T.) * Author to whom correspondence should be addressed; E-Mail: duonghuyen@.vn; Tel.: +84-4-3869-3350; Fax: +84-4-3869-3498. Received: 19 April 2012; in revised form: 24 May 2012 / Accepted: 25 May 2012 / Published: 8 June 2012 Abstract: Polypyrrole/single wall carbon nanotube composites were synthesized by in-situ chemical polymerization using pyrrole (PPy) as precursor and single wall carbon nanotubes (SWNTs) as additive component. Electron microscope images reveal that SWNTs component acts as nucleation sites for PPy growth in the form of spherical and cylindrical core-shell structures. The SWNTs/PPy core-shell results in thin n-p junctions which modify the PPy bandgap and reduce the work function of electrons. As a result of the strong coupling, Raman and IR spectra show that the PPy undergoes a transition from polaron to bipolaron state, i.e., indicating an increase in the conductivity. In the UV-Vis spectra, the 340 nm adsorption band (π*-π transition) exhibits a red shift, while the 460 nm ad