One-Step Synthesis of Charge-Transfer Salt Nanosensors on Microelectrode Patterns

Despite extensive research on nanowires and nanosensors, the lack of manufacturing methods limits nanosensor commercialization. Here a new way of making nanowire sensors is demonstrated. Nanowire crystals of charge-transfer salt, tetrathiafulvalene bromide or (TTF)Br, are electrochemically deposited across lines of microelectrodes made by photolithography to complete the sensor circuitry. A novel concept is the direct synthesis of nanowires on sensor substrates using pre-existing patterns to direct the nanowire nucleation and crystallization. The gas sensing capability of the nanowire assembly is demonstrated for the detection of ammonia at a concentration range of 1-100 ppm by measuring the changes in its electrical impedance. The selectivity toward ammonia against water vapor, one of the most persistent challenges for wide adoption of nanosensors for gas detection, can be tuned by (TTF)Br nanowire chemical composition during synthesis. This work demonstrates a proof of concept toward scalable manufacturing of nanosensor devices via one-step, substrate-directed nucleation and crystallization.