Ruoxue Yan1 2 Yangzhi Zhu1

1, University of California, Riverside, Riverside, California, United States
2, University of California, Riverside, Riverside, California, United States

Ag nanowires (AgNWs) hold great promise for applications such as transparent and flexible displays, solar cells, chemical/biological sensors, photonic circuits and scanning probe microscopies, but their susceptibility to damage from oxidation significantly limit their device life-time and commercialization potential. To address this challenge, we developed a single-step, room-temperature, solution-phase, etch-free deposition technique to grow an ultra-thin, epitaxial layer of Au coating on the AgNW surface, which acts as a reliable and economical anti-oxidation barrier to provide long-term device stability. The Ag@Au core-shell NWs are stable in air and in physiological buffer solution for months. Transparent flexible electrodes fabricated from Ag@Au core-shell NWs shows steady performance in air at 80°C and 100% humidity for 2 months, while those fabricated with bare AgNWs died out within 2 weeks. The ultra-thin Au coating did not introduce significant Au fluorescence in the SERS spectrum, making them feasible for SERS and plasmonic sensing applications. It was also demonstrated that the ultra-thin Au coating does not have adverse effects on the propagation and coupling of surface plasmon polaritons (SPPs) in AgNW waveguides, and the device performance remains stable for weeks, a significant improvement against uncoated AgNW. AgNW-AFM probes are low-cost alternatives of high-aspect-ratio, high-resolution AFM probes, but the major drawback is their short shelf-life (typically a couple of weeks). It was demonstrated that the Ag@Au core-shell NWs functions similarly to bare-AgNW, with a much longer shelf-life for at least 4 weeks in the air.