Candy S. Lin1, Frank Leung-Yuk Lam1, Xijun Hu1, Wing Yim Tam2, and Ka M. Ng3. (1) Department of Chemical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China, (2) Department of Physics and Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China, (3) Department of Chemical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
The synthesis of metallic nanostructures has been, in the current decade, vastly investigated due to its extraordinary properties exerted at such small scales. These nanostructures can be used in many different industries including electronic, photonics and act as building blocks for future nanodevices. These techniques are developed to produce nanostructures suited to perform tasks according to the properties they possess at a particular scale range. One method developed to guarantee nanowire diameter is by using templates to mold out the necessary nanostructures. The chemical fluid deposition (CFD) process involves a metal precursor be dissolved in supercritical fluid and then reduced to deposit metal particles in the porous channels of the selected template.
Platinum nanostructures have been fabricated by CFD method using supercritical carbon dioxide (CO2) as the reaction medium. Ordered platinum nanowires were molded out from a mesoporous silica template, SBA-15, with a pore channel diameter of 7 nm. Solubility study of the platinum precursor, platinum(II) dimethylcyclooctadiene, in the supercritical CO2 was first carried out to obtain a phase diagram in order to optimize the operating parameters required to enhance the infiltration of metal precursor into the porous channels prior to the deposition process. High purity and uniform nanowire bundles resulted after template removal with large aspect ratio of 200:1 carried out at moderate operating temperatures and pressures.