FORMATION OF BRANCHED FRACTAL CDS PATTERNS IN OLIGOMER LB MONOLAYERS - A STUDY USING TRANSMISSION ELECTRON-MICROSCOPY

Transmission electron microscopy images of the treelike fractal aggreg ates of CdS nanoparticles in amphiphilic oligomer (polymaleic acid wit h octadecanol ester) LB matrix were observed. The features of these ag gregates were developed into the micrometer regime. By changing the ra tio between carboxylic groups and hydrocarbon chains, as well as the s urface pressure, different fractal CdS patterns could be obtained. The se results lead us to propose the mechanism of the formation of branch like patterns, very much analogous to two-dimensional irreversible fra ctal-growth models such as diffusion-limited aggregates (DLA). Weak hy drophobic and hydrophilic interaction for interfacial molecular recogn ition at the organic/inorganic interface had been proposed as providin g a possible elucidation for the formation of some aspects of a self-s imilar fractal-like pattern. At a ratio of 7:1, the fractal dimension was calculated by the box-counting method, and the dominant value was 1.69 +/- 0.03, which was in good agreement with two-dimensional DLA.