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. 2012;12(6):7965-74.
doi: 10.3390/s120607965. Epub 2012 Jun 8.

Synergistic effects in the gas sensitivity of polypyrrole/single wall carbon nanotube composites

Duong Ngoc Huyen  1 , Nguyen Trong Tung, Tran Dinh Vinh, Nguyen Duc Thien
Affiliations

Synergistic effects in the gas sensitivity of polypyrrole/single wall carbon nanotube composites

Duong Ngoc Huyen et al. Sensors (Basel). 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 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(3) gas (a reducing agent), the PPy/SWNTs nanocomposite shows an enhancement in sensitivity exceeding ten folds in comparison with those of PPy or SWNTs.

Keywords: PPy; gas sensor; nanocomposite; single wall carbon nanotube.

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Figures

Figure 1.
Figure 1.
FESEM images of (a) PPy, scale bar 1 μm; (b) SWNTs, scale bar 500 nm; (c) PPy/SWNTs nanocomposite, scale bar 500 nm.
Figure 2.
Figure 2.
TEM images of SWNTs (a); PPy/SWNTs nanocomposites (b) and PPy layer/shell on the surface of amorphous carbon and out of SWNTs bundle core (c).
Figure 3.
Figure 3.
FTIR spectra images of SWNTs and PPy/SWNTs nanocomposites: (a) PPy; (b) PPy /SWNTs nanocomposite; (c) AP-grade SWNTs and (d) purified SWNTs.
Figure 4.
Figure 4.
(A) Raman spectra of PPy (a), PPy/SWNTs (b), SWNTs (c), purified SWNTs (d) at 1,064 nm laser excitation; (B) Raman spectra of PPy and PPy/SWNTs in fingerprint spectral region.
Figure 5.
Figure 5.
UV-Vis spectra of PPy and PPy/SWNTs nanocomposite.
Figure 6.
Figure 6.
Oxygen sensitivity of PPy, SWNTs and PPy/SWNTs upon exposure to open air (P: low air presure as pump on, O: open air).
Figure 7.
Figure 7.
NH3 sensitivity of PPy, SWNTs and PPy/SWNTs upon exposure to 750 ppm NH3. (A: NH3 on, B: NH3 gas off).
See this image and copyright information in PMC

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