Syntheses of micrometer-long Pt and Ag nanowires through SBA-15 templating

We synthesized Pt and Ag nanowires using a mesoporous silica, SBA-15, as templates. The obtained nanowires are a few micrometers (̃4 μm) long and 7 nm in diameter. The nanowires are free from bundling and, thus, can be separated as single nanowires. The successful synthesis of such nanowires requires a few considerations. In general, SBA-15 has microchannels on the walls through which the mesopores are interconnected when synthesized at 100 °C or higher. We, therefore, synthesized SBA-15 at a low temperature (80 °C) to eliminate the microchannels. Impregnation of the metal precursors and reduction of them into metals forms metal particles outside the pores in addition to the desired metal nanowires inside the pores. Surface alkylation of SBA-15 prohibits the nucleation of metal on the external surface and exclusively forms the nanowires. Finally, the introduction of surface passivating agent, an alkylthiol, during the removal of the template keeps the nanowires from interacting with one another. The Pt and Ag nanowires so-synthesized were characterized by electron microscopy.