Polymer composite-based OFET sensor with improved sensitivity towards nitro based explosive vapors

Sensors based on the organic field effect transistors (OFETs) have been used for detection of vapors of explosives, e.g. 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 2,4,6-trinitrotoluene (TNT), and dinitrobenzene (DNB). The organic composite used was a combination of P3HT (poly 3-hexylthiophene), CuTPP (CuII tetraphenylporphyrin) and ADB (copolymer of diethynyl-pentiptycene and dibenzyl-ProDOT). The incorporation of ADB into P3HT/CuTPP composite makes the film porous and thereby increases the sensitivity of the sensors by increasing the permeability of the analyte into the sensing polymeric matrix. Secondly, it increases the surface roughness which eventually increases the surface area resulting in an increased sensitivity. Along with an improved sensitivity (enhances the response by around 30% to nitro based explosive compounds), the sensors exhibit an excellent selectivity for nitro based explosive analytes like TNT, RDX, DNB as compared to the vapors of non-explosive oxidizing agents such as nitrobenzene (NB), benzoquinone (BQ) and benzophenone (BP). Porosity was analysed using gas (N2) sorption techniques (BET analysis). Surface roughness was characterized by AFM (atomic force microscopy). EFM (electrostatic force microscopy) was also done to see the effect of ADB polymer in reducing the initial conductivity of the film.