Electrospinning as a cost-effective process to synthesize nanofiber with controlled morphology and structure has regained attention in the last decade as result of rapid advancements in nanoscale science and engineering and their applications. Although there are a few works demonstrated the ability to fabricate nano gas sensor using electrospun nanofibers as sensing materials, there are limited works to show the optimization of the sensing performance by understanding the electron transport properties and their sensing mechanism. The overall objective of this work is to electrospun conducting polymer/insulating polymer composite nanofibers (i.e., (+)- camphor-10-sulfonic acid (HCSA) doped polyanline PANI (conductive) blended with PEO (non-conductive)) with different compositions (i.e., 12 to 68 wt.%) and apply them as chemiresistive sensing material to detect ammonia at room temperature. The diameter, defects, and morphology of nanofibers were adjusted by controlling solution composition, processing parameters and their effect toward the sensing performance were also investigated.
Viscosity of electrospinning solutions was found to have a pronounced impact on fiber diameter and morphology of PANI/PEO nanofibers. Diameters around 350nm of different compositions of PANI/PEO nanofibers were achieved, where decreasing solution viscosity by increasing the PANI content resulted in a morphology changing from individual fibers to junctions. Although all the compositions of PANI/PEO nanofibers show semiconducting behavior and fit a three dimensional variable hopping range model, the activation energy and hopping distance increased as the PANI content decreased.
The PANI/PEO nanofibers exhibited excellent sensitivity towards NH3 with fast response and recovery times where a low detection limit of 0.5 ppm with the sensitivity of 5.6 %/ppm of NH3 was achieved from 26 wt.% PANI/PEO nanofibers. Additionally, the PANI/PEO nanofibers response toward water vapor changed from positive to negative indicating the humidity independent ammonia gas sensor can be fabricated by controlling the composition of PANI/PEO nanofibers.
