2, University at Buffalo, State University of New York, Buffalo, New York, United States
Molecular recognition of adsorbates with very high sensitivity and selectivity is critical in chemical sensing. Nanosystems such as nanowires have been envisioned as a sensor platform for the next generation high performance sensors. In general chemical selectivity in miniature sensors is obtained by using immobilized receptors. However, obtaining chemical selectivity is a challenging task because of the lack of highly selective receptor molecules that can be immobilized on sensor surfaces. In addition immobilizing receptors on nanosensors most often results in irreproducible surface coverage. Therefore, developing receptor-free concepts for obtaining selectivity is very attractive. Molecular adsorption-induced variations in work function and its temperature dependence is an attractive approach for receptor-free chemical sensing. Work function of Pt nanowires investigated with Kelvin Probe Force Microscopy show significant changes due to molecular adsorption. Temperature dependent changes in the differential work function shows peaks corresponding to molecular desorption. Because of their high surface to volume ratio and very low thermal mass of nanowires, this approach can provide high selectivity, sensitivity, and fast operation and offers an elegant route to an extremely sensitive and highly selective sensor platform.