Nano Focus: Growth of low-temperature Si nanowires suitable for electronic memory devices
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onventional synthesis methods for nanoparticles (NPs) suffer from low uniformity, surface contamination, and poor stability, limiting their practical use. A significant step toward overcoming these problems was recently developed by researchers at Stony Brook University, who devised a novel synthesis route based on helium nanodroplet isolation that produces a narrow distribution of clean and stable gold NPs. “This is a very powerful method for producing active nanoparticles, which can be extended to other metals [beyond gold]. The helium droplet method produces very clean nanoparticles,” says Alexander Orlov, the leader of the research team in the Department of Materials Science and Chemical Engineering at Stony Brook University, The State University of New York. “By depositing them on any substrates this approach can be applied to produce energy in a clean way, and address environmental issues by oxidizing various atmospheric pollutants,” he adds. As reported in the July issue of The Journal of Physical Chemistry Letters (doi:10.1021/acs.jpclett.6b01305), Qiyuan Wu and his colleagues created “nanoscale
cryostats” using helium droplets. These droplets capture and condense the vaporized gold atoms, then carry them to the collector. The helium atoms evaporate immediately once they hit a collector, and simultaneously Au atoms form NPs with pristine surfaces. By varying the nozzle temperature and deposition time, the researchers could tune the size of the resulting NPs, achieving diameters down to
