MS-1-P-2352 Growth and packaging of ultrathin Au nanowires for enhanced thermal stability: An in-situ TEM study

Ultrathin Au nanowires are potential candidate for catalysis, sensing, plasmonic and biological applications. Most of these applications require a clean interface for better performance. Fragility on polar solvent cleaning and hydrophobicity due to the associated linkers limit the use of the nanowires in their as-synthesized form. We have developed a strategy for growth of these nanowires directly on substrates (Figure 1) that imparts stability to the wires. The study on growth and mechanism of nanowire formation on substrates has been carried out using electron microscopy (SEM & TEM) and other techniques.
Poor thermal stability limits the use of these nanowires to low temperature applications only. Hence, for high temperature applications proper packaging of the nanowires is required. A simple wet-chemical method has been developed to coat these nanowires with mesoporous SiO₂ (Figure-2) and TiO₂ coatings. The SiO₂ layer thickness could be controlled very easily by this method by varying the reaction time. Coating thickness of a few nanometers could be obtained. In-situ TEM thermal stability studies have been carried out on the SiO₂ coated nanowires. Figure 3 shows the TEM images of the nanowires as the temperature is increased over a period of 4-5 hours. Bare nanowires had been drop-casted on the same grid for comparison. The non-coated nanowires (marked in red) break into nanoparticles at very low temperature as shown in the set of images. Coated nanowires became segmented at similar temperatures but the segments show remarkable stability at high temperature (553⁰C) for long times.