Abstract
This study is focused on the morphology development of silver nanostructures in the polyol process by means of simultaneous small/wide-angle X-ray scattering (SAXS/WAXS), scanning electron microscopy (SEM), and ultraviolet-visible spectroscopy (UV-Vis). In this study, we carried out the experiment with different conditions by controlling the flow rate of AgNO3 solution as reactant. One is the once-adding and the other is the dropwise-adding whose flow rate is ca. 3.5 mL/min into the reactor. The exact time of silver nanowires appearance is confidently determined from UV-Vis absorption, SEM observations and color evolution. For the once-adding condition, silver nanoparticles appear at the beginning of reaction; after t = 5 min, nanorods begin to show up in the reaction and become the dominating species after t > 8 min. Silver nanorods are unstable during this period and called as embryonic nanorods, simultaneously Ag face-centered cubic (FCC) signals appear in the WAXS profiles. Meanwhile, embryonic nanorod, which is unstable and fragile, would be damaged by electron beam of SEM. Through irradiation of electron beam on embryonic nanorod makes the nanograins emerge from the embryonic nanorod. This implies that silver nanorods are formed by coalescence of silver nanograins. After that, we can see a great amount of silver nanowires in the reaction. For the dropwise-adding condition, the reaction trend is similar to the once-adding and but with a few minutes’ delay. It suggests that silver nanoparticles need to reach an adequate concentration to form nanowires. From all observations, we deduce that sufficient nanoparticles coalesce to form embryonic nanorods, followed with growing in axial direction by probably interacting with PVP chains to form silver nanowires.