Charge transport and ammonia sensing properties of flexible polypyrrole nanosheets grown at air–liquid interface

Flexible polypyrrole nanosheets (thickness ∼150 nm) grown at the air–liquid interface have been investigated for charge transport and NH3 sensing application. Polypyrrole nanosheets films exhibited a uniform and dense morphology. Temperature dependent charge transport measurements revealed that the PPy films obey Mottʹs 3-D variable range hopping mechanism. The mobility values calculated using temperature dependent current voltage characteristics indicated them to obey Arrhenius behaviour. These films exhibited a reversible response towards NH3 at room temperature. The sensor exhibited a sensitivity of ∼12% with a typical response and recovery times of 240 s and 50 min, respectively towards 50 ppm of NH3. Raman studies indicated that there is an increase in the antisymmetrical C–N stretching upon exposure to higher concentration of NH3 (500 ppm) and could be assigned to the interaction of NH3 with the carbon backbone of PPy film. Our results clearly emphasize that these flexible PPy films could be used to realize flexible sensors.