Me. Nicho et al., Polyaniline composite coatings interrogated by a nulling optical-transmittance bridge for sensing low concentrations of ammonia gas, SENS ACTU-B, 76(1-3), 2001, pp. 18-24
Polyaniline (PANI) is a pi -conjugated polymer that shows electric and opti
cal property changes, when it is in contact with oxidant/reductor chemicals
. In particular, the interaction between the conductive form of PANI, the e
meraldine salt (ES), and the NH3 gas results in a decrease of the polaron d
ensities inside the band gap of the organic material. In this work, the opt
ical-transmittance changes detected in PANI coatings as a function of the s
ensing ammonia gas concentrations are studied by using a nulling optical-tr
ansmittance bridge with a 632 nm laser (He-Ne) source, which allows a sensi
tive monitoring of optical property changes. It is observed that the conduc
tive PANI-polymethyl methacrylate (PMMA) composite coatings are sensitive f
or very low concentrations of HN3 (from similar to 10 to 4000 ppm, dependin
g on the PANI films' electrical conductivity), and their optical response i
s reversible as the reduction gas is removed by N-2. (C) 2001 Elsevier Scie
nce B.V. All rights reserved.