Role of polyaniline/molybdenum trioxide nanocomposites in tuning the characteristics of humidity sensors

Real time humidity monitoring is crucial in several fields such as pharmaceuticals, electronic device manufacturing, in agricultural irrigation system due to drastic changing climates and so forth. In this work, we studied humidity sensing behavior of molybdenum trioxide (MoO3) in composition with conductive polyaniline (PAni). The conductive PAni used in the present study was in the emeraldine salt (ES) form and was doped with amino tris-methylene phosphonic acid (PAni-ATMPA) as a potential candidate for humidity sensors. PAni-ATMPA is synthesized by oxidative polymerization of aniline monomers and ATMPA in the ratio of 1:1. Thus synthesized PAni and hydrothermally synthesized MoO3 were mixed together to form nanocomposites. The synthesized composites were then used to fabricate planar sensors on alumina substrate with pre-deposited silver electrodes. XRD analysis of synthesized MoO3 shows an orthorhombic crystal structure whereas synthesized PAni shows amorphous nature. FESEM analysis of synthesized MoO3 shows sheet-type morphology. Different compositions of MoO3:PAni were prepared by varying MoO3 and PAni wt %. The fabricated sensors were then tested over the range of 20%-90% RH and concluded that the sensitivity of the composite is seen to be higher for the composite with 20% PANi and 80% MoO3 with response time, recovery time and the linearity 7 s, 4 s, 13-62 RH% respectively. The above mentioned parameters are found to be improved in the composites as a result of PAni addition to MoO3 than the pristine MoO3. The experimental knowledge demonstrates that the films showed good repeatability (with +/-4%uncertaintyTHORN and reproducibility (with +/-3% uncertainty). Altogether, these results indicate that it is possible to tune the humidity sensing characteristics by optimizing the amount of MoO3 and PAni in MoO3:PAni composite.