Organic Sensor Platforms for Environmental and Security Applications

Abstract

Organic sensors based on polymer microcantilevers and organic field effect transistors (OFETs) bring orthogonality to the sensing mechanism for different environmental and security applications. Orthogonolity is an important requirement from the point of reducing the false positives, which is of utmost importance for many applications. Development of polymer nanocomposite microcantilever based sensors for explosive vapour detection was reported. These polymer microcantilevers offer a deflection sensitivity of 1.1ppm for 1nm of deflection, which is the highest sensitivity reported till date. The sensor response to trinitrotoluene (TNT) vapours at a few parts per billion concentration levels was demonstrated. OFETs using poly 3-hexylthiophene (P3HT) and CuII tetraphenylporphyrin (CuTPP) composite as their active material were studied as sensors for detection of various nitro-based explosives. Significant changes were observed in the ON current (Ion) and transconductance (gm) of the OFET sensor after exposure to vapours of various explosive compounds. Sensor selectivity to explosive vapours over strong oxidizing agents was also demonstrated. Also, the change in conductivity for organic semiconducting material as a function of ionizing radiation was studied with an organic semiconducting material in resistor and OFET configurations. 30MΩ/Gy sensitivity for the organic resistor sensor and 28fA/Gy/1µm-width sensitivity for OFF current for the OFET sensor were observed. Moreover, changes in various other electrical parameters for an OFET sensor were also found proportional to the ionizing radiation dose.