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Prashant Sonar1

1, Queensland University of Technology, Brisbane, Queensland, Australia

Recently, advances in chemical sensing based on organic thin film transistors (OTFTs) with solution processed conjugated polymers as an active layer semiconductor have shown great improvements in sensing performance.1 Using such OTFT sensors, wide range of analytes such as volatile aliphatic and aromatic organic compounds, explosive gases and toxic solvent vapours can be detected precisely with higher sensitivity and appropriate selectivity. The sensing performance is strongly depends on the choice of organic semiconductors as an active organic channel semiconductor and its morphology at nanoscale. Thanks to the state-of-the-art solution processable diketopyrrolopyrole (DPP) based donor-acceptor (D-A) polymers which have shown tremendous progress in high performance organic electronic devices.2

In the present work, we report the detection and identification of toxic xylene isomers in gas phase using DPP polymer based OFET devices since Xylene isomers has great importance in human safety and health.3 Our ambipolar poly(diketopyrrolopyrrole-terthiophene) based OFET can detect xylene isomers at 80 ppm level, which is below the long-term permissible exposure limit (100 ppm) by the U.S. National Institute for Occupational Safety and Health. Other organic volatile analytes such as alkanes (hexane, octane and decane) as well as aromatics (benzene and toluene) have been also detected in OFET sensors.4 Additionally, we have also successfully demonstrated nitrobenzene, dinitrobenzene, nitromethane, trinitrotoluene and RDX based explosive OFET sensors. The sensitivity of the OFET based device has been estimated to be 1.7 µA for ppb range of TNT, 27.5 µA for ppb range of RDX at ambient conditions.5 The results presented in this work signify a great potential of DPP polymers for the various types of OFET based chemical sensors.

1. T. Someya, A. Dodabalapur, J. Huang, K.C. See, H.E. Katz, Chemical and Physical Sensing by Organic Field-Effect Transistors and Related Devices, Adv Mater, 2010, 22, 3799.
2. Y. Li, P. Sonar, L. Murphy, W. Hong, High mobility diketopyrrolopyrrole (DPP)-based organic semiconductor materials for organic thin film transistors and photovoltaics, Energy Environ Sci, 2013, 6, 1684.
3. Wang, T.P. Huynh, W.W. Wu, N. Hayek, T.T. Do, J.C. Cancilla, J. S. Torrecilla, M. M. Nahid, J. M. Colwell, Oz M Gazit, S. Reddy Puniredd, C. R. McNeill, P. Sonar, H. Haick, A Highly Sensitive Diketopyrrolopyrrole-Based Ambipolar Transistor for Selective Detection and Discrimination of Xylene Isomers, Adv Mater, 2016, 28, 4012.
4. B. Wang, P. Sonar, S. Manzhos, H. Haick, Diketopyrrolopyrrole copolymers based chemical sensors for the detection and discrimination of volatile organic compounds, Sens. Actuator B-Chem., 2017, 251, 49.
5. S. G. Surya, S. S. Nagarkar, S. K. Ghosh, P. Sonar, V Ramgopal Rao, OFET based explosive sensors using diketopyrrolopyrrole and metal organic framework composite active channel material, Sens. Actuator B-Chem., 2016, 223, 113.

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