Morphology dependent ammonia sensing with 5-sulfosalicylic acid doped nanostructured polyaniline synthesized by several routes

Polyaniline (PANI) doped with 5-sulfosalicylic acid (SSA) has been synthesized employing several techniques, viz. polymerization, Langmuir Blodgett (LB), spin-coating and electrodeposition. The influence of process variation on the structure, electrical conductivity and ammonia vapour sensing performance (response percentage and response time) has been investigated. The synthesized samples have been structurally characterized by transmission electron microscopy (TEM), UV–vis, and FTIR spectra. TEM analysis reveals formation of nanorods and nanospheres of PANI. Nanorods are formed for the samples synthesized by electrodeposition and LB technique whereas for the samples synthesized by polymerization and spin-coating, nanospheres are formed. Among these four different synthesized samples, the one deposited by LB technique exhibits highest conductivity due to the ordered molecular architecture. An exploration of variation of conductivity of these samples after exposure to ammonia reveals that the polymerized sample having highest surface to volume ratio exhibits fastest response (least response time), while the spin coated sample show sluggish response. The importance lies in the mapping between response percentages of different samples with the surface to volume ratio of the various nanostructures.