Optimizing Growth Rates and Thermal Stability of Silver Nanowires
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Optimizing Growth Rates and Thermal Stability of Silver Nanowires Elham Majidi, and Byron D. Gates Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada ABSTRACT A solution-phase synthesis of silver nanowires is presented along with insight into the mechanism of growth and stabilization of the nanowires. Solution-phase synthetic methods are attractive for the ease of scaling to production of large quantities of nanowires. Impurities in solution can, however, minimize this yield. The yield of silver nanowires is reduced by the oxidation of silver or the presence of impurities. The quantity of spherical nanoparticle byproduct can be reduced by incorporating metal etchants within the solution. The yield of nanowires is also optimized by changing the reaction temperature to balance the rate of growth, rate of etching, and stability of surfactants on specific crystalline facets of the nanowires. INTRODUCTION We have demonstrated the ability to synthesize silver nanowires by a high-yield solutionphase synthesis. The insight we have gained into the mechanism of growth of the nanowires and stability of their surface chemistry will be essential for scaling-up this synthesis. One of our goals was to decrease the by-products from the synthesis, such as the formation of spherical (or near spherical) nanoparticles and other low-aspect ratio nanostructures. These by-products are common to many solution-phase syntheses. Nanowire growth initiates from a nucleation event within solution. The number of nucleation events and their frequency dictate the nanowire yield and uniformity of growth. Growth of the nanowire proceeds as material deposits preferential onto certain crystalline facets of the seed particle, while the remaining facets are of sufficiently lower surface energy to prevent material deposition. The direction of growth can be controlled by either the crystal structure of the seed particles [1,2] or by capping other crystalline facets with surfactants [3-5]. The challenge in designing these syntheses is to identify molecules that specifically bind to the facets of the crystal on which one wants to prevent growth, but not along the direction of preferred growth. Our second goal was to understand the thermal stability of the interactions between the surfactant and the different surfaces of the crystalline silver nanowires. Further insight into controlling the nanowire yield and stability of their surface chemistry could assist in the improvement of other solution-phase syntheses of nanostructures. Our study focuses on the synthesis of silver nanowires. Silver is of interest for its high electronic conductivity, ability to form important alloys,[6] and ease of surface modification [7]. The synthesis of silver nanowires has been explored [3,8]. Some of the most notable work has provided an understanding of the dependence of nanowire formation on the presence of water and impurities [9,10]. Many aspects of the synthesis are, however, still unknown. We modified the pu
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