Chitosan-poly(acrylic acid) nanofiber networks prepared by the doping induction of succinic acid and its ammonia-response studies

Chitosan-poly(acrylic acid) (CS-PAA) composite membrane with a 3D network nano-structure was prepared using an electrostatic interaction process by adding succinic acid as a branch promoter. Variations of the final solution pH values, concentration of CS, and PAA/CS volume ratio were examined systematically for their effects on average fiber diameter size, intensity of surface charge, and tendency of network formation. It was found that nanofiber size was affected by the mixing ratio of PAA and CS, the concentration of CS, and the final pH of the CS-PAA solution. The smallest diameter size distribution of the scaffold can be obtained when the PAA/CS ratio is in the range of 2:1-1:2 in a pH 3 environment. Negative charge nanofibers prepared using PAA and CS in a ratio of 2:1 in pH 3 environments had an average diameter of 215 nm. The formation of the interconnecting 3D self-organized network structure can be built up with limited parasitic branching by crystallized succinic acid. The gas response to ammonia, including sensitivity and response time, was evaluated using impedance spectroscopy at room temperature. The results of sensing experiments indicate that the sensitivity of nanofibrous membrane (NM)-coated sensors was eight times higher than that of continuous film-coated sensors. NM-coated sensors exhibited high sensitivity towards a low concentration of ammonia, as low as 50 ppm at a relative humidity of 45%. Copyright (C) 2008 John Wiley & Sons, Ltd.