Diffusion on Silver Nanorod Surfaces: Mechanisms of Fast Diffusion at Low Temperature

Ag nanorods may serve as sensors in the detection of trace amounts of chemical agents, even single molecules, through surface enhanced Raman spectroscopy (SERS). However, thermal coarsening of Ag nanorods near room temperature limits their applications. In this work, we examine this thermal instability through molecular dynamics simulations and molecular statics calculations in order to elucidate the process. From these computational methods, it is realized that the thermal instability of Ag nanorods is the result of rapid surface diffusion, and we hypothesize that the thermal stability can be enhanced by the addition of a thin dielectric cap. This hypothesis is then tested through the use physical vapor deposition, electron microscopy characterization, and SERS tests. It is shown that the proposed method is effective in stabilizing both morphology and sensitivity of Ag nanorods, confirming the findings of the computational study and the prediction based on those findings. The results of this work extend the applicability of Ag nanorods as chemical sensors to higher temperatures