Platinum nanoparticles are usually in the form of a suspension or colloid of sub-micrometre-sized particles of platinum in a fluid, usually water. A colloid is technically defined as particles which remain suspended without forming an ionic, or dissolved solution. The broader commercial definition of "colloidal platinum" includes products that contain various concentrations of ionic platinum, platinum colloids, ionic platinum compounds or platinum nanoparticles in purified water.

The platinum nanoparticle sizes range between 2-3 nanometres (nm). Trillions of platinum nanoparticles are suspended in the brownish red or black colored colloidal solution. Nanoparticles come in wide variety of shapes including spheres, rods, cubes, and caps.

Due to the antioxidant properties of the platinum nanoparticles, they are the subject of substantial research with applications in a wide variety of areas, including nanotechnology, medicine and the synthesis of novel materials with unique properties.

Synthesis

Platinum nanoparticles are fabricated by reduction of hexachloroplatinate. After dissolving hexachloroplatinate, the solution is rapidly stirred while a reducing agent is added. This causes platinum ions to be reduced to neutral platinum atoms. As more and more of these platinum atoms form, the solution becomes supersaturated and platinum gradually starts to precipitate in the form of sub-nanometre particles. The rest of the platinum atoms that form stick to the existing particles, and, if the solution is stirred vigorously enough, the particles will be fairly uniform in size. Various procedures employed to attain platinum nanoparticles include heating, reflux, cooling, stirring, filtration and filling, examinations & tests and packaging. To prevent the particles from aggregating, some sort of stabilizing agent or stabilizer that sticks to the nanoparticle surface is usually added. They can be functionalized with various organic ligands to create organic-inorganic hybrids with advanced functionality.

Biological effects

Research by Yusei Miyamoto at University of Tokyo, Japan, resulted in the use of platinum nanoparticles of the size 2-3 nm to increase the lifespan of the roundworm Caenorhabditis elegans.

Nanoparticles may present possible safety issues both medically and environmentally. Most of these issues usually arise due to the high surface to volume ratio, which can make the particles of some metals very reactive or catalytic . Animal experiments conducted so far have not shown any risks. They are able to pass through cell membranes in organisms and their interactions with biological systems are relatively unknown. However, free nanoparticles in the environment quickly tend to agglomerate and thus leave the nano-regime, and nature itself presents many nanoparticles to which organisms on earth may have evolved immunity (such as salt particulates from ocean aerosols, terpenes from plants, or dust from volcanic eruptions).

See also

• Colloidal gold
• Nanoparticles
• Nanotechnology

References