Sensors (Jun 2012)

Synergistic Effects in the Gas Sensitivity of Polypyrrole/Single Wall Carbon Nanotube Composites

  • Nguyen Duc Thien,
  • Duong Ngoc Huyen,
  • Tran Dinh Vinh,
  • Nguyen Trong Tung

DOI
https://doi.org/10.3390/s120607965
Journal volume & issue
Vol. 12, no. 6
pp. 7965 – 7974

Abstract

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Polypyrrole/single wall carbon nanotube composites were synthesized by <em>in-situ</em> 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 <em>n-p</em> 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, <em>i.e.</em>, 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 adsorption band (bipolaron transition) experiences a blue shift indicating a change in electronic structure and a relocation of polaron levels in the band gap of PPy. The modification in PPy electronic structure brings in a synergistic effect in sensing feature. Upon exposure to oxygen (an oxidizing agent) and NH<sub>3</sub> gas (a reducing agent), the PPy/SWNTs nanocomposite shows an enhancement in sensitivity exceeding ten folds in comparison with those of PPy or SWNTs.

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