Large-scale, and ultra-long silver nanowire via polyol process with successive multistep growth and characterization

Abstract

Nanostructures including quantum dot, nanoparticles, carbon-nanotube (CNT), graphene, and nanowires have been extensively studied and explored for applications such as optical devices, electrical device, and biosensors due to their promising characteristics. One dimensional noble metal nanowires are vigorously applied through their unique properties which cannot be found in bulk state. For instance, Silver nanowires have been extensively studied since they play important roles in practical devices. Among the various strategies for Ag nanowire synthesis, polyol process is regarded as an ideal method due to such advantages as rapidity, high yield ratio and repeatability. In spite of these advantages, controlling the length is difficult and the aspect ratio of a silver nanowire is usually limited to 100 ~ 400. In this study, we developed a novel approach to synthesize longer and higher aspect ratio Ag nanowires with higher yield. First, We performed extensive parametric studies to find the optimum condition for ultra-long Ag nanowire synthesis by controlling external conditions, such as different types and combinations of stir bar, RPM, sonication effect and injection speed. Second, a novel synthesis approach called a successive multi-step growth (SMG) is introduced to increase the aspect ratio of silver nanowire even further. It has been confirmed that the silver nanowire, after its initial growth, can continue to grow as long as the Ag-ion rich condition is repeatedly provided. Through the scheme of a SMG method, we successfully obtained extremely high aspect ratio (1000 to 3000) silver nanowires of 300 μm in length with 150 nm diameter. This value is almost an order of magnitude enhancement from previous work and such nanowires are expected to be particularly valuable for flexible and transparent electrodes. Moreover, the mean length of silver nanowires also increased. The production of ultra-long metal nanowires at a large scale has significant impact on the...