Preparation and characterization of platinum nanoparticles protected by alkyltrimethylammonium chlorides

Alkyltrimethylammonium chloride-protected platinum nanoparticles were prepared by the photo-reduction method, Transmission Electron Microscopy (TEM) observations were made and the size of the metal core was found to be independent of the chain-length and the concentration of. the protective surfactants. Diffusion coefficients of the Pt nanoparticles were measured and found to be essentially the same as those of the respective surfactant micelles, suggesting that the protective surfactant molecules are tilted. Fluorescence decays for an anionic porphyrin adsorbed on the protective layers of Pt nanoparticles were measured. The dependence of the fluorescence quenching rare constants on the chain-length of protective surfactants was found to be 0.45 per methylene unit. This small value is interpreted in terms of the penetration of the porphyrin ion into the protective layer.