Effect of particle size variation of Ag nanoparticles in Polyaniline composite on humidity sensing.

The results of synthesis of Ag-Polyaniline nanocomposite along with an investigation of optical fiber based humidity sensor using evanescent wave absorption spectroscopy are discussed. The sensor was fabricated using Ag-Polyaniline nanocomposite deposited on an optical fiber clad and tested in the range of 5-95% relative humidity (RH). Optimization of clad length (2-8mm) was done and then particle size (15-30 nm) variation of silver nanoparticles in Polyaniline composite was studied for better performance of sensor. The effect of particle size on sensing humidity was investigated. The reduction of particle size, leads to a dramatic improvement in sensitivity and speed of response. The optimized clad length of 6mm exhibits the better results for 15 nm particle size of Ag nanoparticles dispersed in Polyaniline. The sensor response is fully reversible having almost 1% of standard deviation. Response time of the sensor is 30s with a slow recovery of 90 s.