Nanowire Sensor for Volatile Organic Compounds by Formation of Charge Transfer Complex

Recently, the electrical characteristics of metal-molecule-metal nanowires are studied. Interaction between the junction molecule and the analytes will affect the molecular orbital that alters a conductive path. We have been interested in charge transfer (CT) interaction that induces the partial transfer of electron from an electron donor to an electron acceptor. The measurement result obtained with crossed-wire tunneling junction indicated that the CT interaction provides a significant conductance change of the junction molecule. In this report, we suggest a nanowire sensor to detect volatile organic compounds (VOC) by conductance switching brought on by the charge transfer interaction. The sensor surface possesses a molecular wire network formed by bridging nanogaps between Au nanoparticles (Au-NPs) with electron donor molecules. The Au-NPs were fabricated by sputter deposition with controlling the particle-size and the gap-size. We confirmed the donor oligothiophene bridging by resistance transition and the formation of CT interaction between oligothiophene and analytes by fluorescence quenching. The conductance of the sensor electrode increased by adsorption of electron acceptors, such as iodine and aromatic nitro compounds.