Characterization of Pt microcrystals using high resolution electron microscopy

Small colloidal particles of platinum have been produced with and without a protective agent (polyvinylpyrrolidone), and have been studied by high resolution electron microscopy. Initially, the protected particles have been found to be single crystals in the size range 5-30 Å. After continued beam exposure, the protective coating's effect is lost and the particles coalesce, forming both larger single crystals and multiply-twinned crystals. In contrast, a sample of the unprotected particles shows extensive initial linking and twinning, but no further beam-induced agglomeration.