Platinum is a rare element and therefore in demand for use in both jewelry and as a catalyst. In bulk form, platinum is one of the most effective but expensive catalysts available. You probably use platinum as a catalyst every day in the catalytic converter in your car. The platinum in a catalytic converter helps change air-polluting molecules from your car exhaust into less harmful molecules.
The atoms in molecules, such as hydrogen, bond with platinum atoms, and then the platinum atoms release the hydrogen atoms, allowing them to react with other molecules. By breaking up molecules into atoms, platinum facilitates chemical reactions and allows them to occur at a lower temperature than they could without a catalyst. Using nanoparticles of platinum increases the surface area available for a reaction and also increases the percentage of platinum atoms available for contact with molecules involved in the reaction. This difference allows researchers and manufacturers to use smaller quantities of platinum, which is important given its high cost.
These improved catalysts have a better capability to break down air pollutants and also reduce the cost of catalysts used in fuel cells. But platinum comes at a high price, so nanotechnologists may choose other options in some cases.
Excerpted from Nanotechnology For Dummies (2nd edition), from Wiley Publishing