Alexander B. Smetana

Biocidal Activity of Nanocrystalline Silver Powders and Particles

While the activity of the SMAD powders is lower than that of pure silver nitrate, it has the ability to kill bacteria very effectively and over long periods of time.

Depositing ordered arrays of metal sulfide nanoparticles in nanostructures using supercritical fluid carbon dioxide.

Silver sulfide and cadmium sulfide nanoparticles of controllable sizes are synthesized using a water-in-hexane microemulsion method and stabilized by dodecanethiol. The stabilized metal sulfide nanoparticles can be deposited homogenously on flat substrates forming ordered 2-D arrays in supercritical fluid carbon dioxide (Sc-CO(2)). The use of Sc-CO(2) leaves the particles unaffected by dewetting effects caused by traditional solvents and produces uniform arrays. The Sc-CO(2) deposition technique is capable of filling nanoparticles in nanostructures of silicon wafers which is difficult to accomplish by conventional solvent evaporation methods.

Directed/localized growth of multiwalled carbon nanotubes catalyzed by cobalt nanoclusters

Tip based lithography was used to print arbitrary patterns of cobalt oxide nanoclusters from single features to large repeatable arrays over square millimeter areas. Cobalt ions were mixed with a P2VP-PEO block-copolymer and were delivered in sub-micron sized droplets to a surface. These droplets were heat treated at 360 °C, which removed the organic polymer and formed Co3O4 nanoclusters. The deposited material was used as a catalyst to grow multiwalled carbon nanotubes (MCNTs) at each printed location. AFM and SEM imaging were used to examine the morphology of the cobalt oxide nanoclusters and multiwalled carbon nanotubes. Powder X-ray diffraction was used to identify the catalytic material, while Raman spectroscopy was used to interrogate the resulting carbon structures. This directed multiwalled carbon nanotube growth method can be applied directly for sensor fabrication.