2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Polypyrrole-Organoclay Nanocomposites for Gas Sensors

R. Magaraphan and A. Thuimthad
Chulalongkorn University, TH

Keywords:
polypyrrole, nanocomposites, gas sensor, doping

Abstract:
Polypyrrole (PPy) was synthesized in the presence of octadecylammonium-montmorillonite (OC-MMT) 1-9 wt% using ferric chloride as an initiator to result the intercalated nanocomposites. The synthesized PPy and its nanocomposites were tested for volatile organic gases; i.e. CO2, CH4 and C2H4. The resistance under these gases was presented also as sensitivity (1 to -1 %) and cross sensitivity for the mixed gas (-2 to 2%). The response time for all materials was found to be within 1-1.5 minutes. Sensitivity to CO2 was decreased as OC-MMT content increased but for methane and ethylene, there was a critical OC-MMT content at 3 wt% that showed similar sensitivity below this content methane had better sensitivity and vice versa. At the critical content, doping with DBSA can distinguish the sensitivity of methane from ethylene. Thicker samples gave lower resistance than the thin ones. The content of 1 wt% OC-MMT is sufficient and optimum to obtain good sensitivity in order of CO2>CH4>C2H4. For the mixed gas system, CO2: CH4 and CO2:C2H4, increasing methane or ethylene gas ratio and increasing OC-MMT content resulted in better cross sensitivity of methane or ethylene in the mixed gas to CO2 . Increasing doping ratio enhanced cross sensitivity for methane but doping ratio of 0.5 is optimum for ethylene.

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