Thermally assisted photoreduction of vertical silver nanowires

Abstract

Vertically grown silver nanowires (Ag NWs) 100–150 nm in diameter and 5–10 µm in length have been successfully prepared by thermally assisted photoreduction (TAP) of aqueous silver nitrate (AgNO₃) solution on anatase films without using surfactants, templates or seeds. X-Ray diffraction (XRD) and transmission electron microscopy (TEM) show that the Ag NWs thus produced are single-crystalline with a preferred growth direction along [10]. Investigation of their electrical behavior, using a scanning electron microscope (SEM) equipped with a nano-manipulation device, showed that the resistivity of the Ag NWs is about 18.79 µΩ cm, indicating their excellent quality. The nucleation and yield (i.e. number of NWs per 100 µm²) are closely related to the crystallinity, surface morphology, and the photocatalytic ability of the anatase substrates. The length distribution of the Ag NWs is dominated by the temperature of the post-heat treatment, which affects the supply of thermal electrons for NW growth. It is also demonstrated that various face-centered cubic (FCC) metallic NWs, including gold and copper, can also be obtained by the TAP process. The yield of NWs is inversely proportional to the charge number of the metallic cations in aqueous solution.