In situ imaging of CdS and ZnS semiconductor particles in surfactant vesicles

The study of synthetic vesicles and micelles as organized media for photoelectron conversion, molecular electronics, and catalysis is an area of intensive research. In this regard, the study of semiconductor systems is particularly prominent. However, to date there has been no direct evidence for the location of these particles within the organized organic phase. Using a combination of dark field imaging, electron diffraction, and energy dispersive X-ray analysis, we have been successful in determining the structures and morphologies of in situ precipitated, coprecipitated, and sequentially precipitated colloidal CdS and ZnS on the surfaces of dihexadecyl phosphate vesicles. The precipitated particles have diameters in the range of 2-8.5 nm and cubic Zn-blende structures. Nucleation of the particles takes place at the phospholipid headgroups and particle aggregation is inhibited at the organic surface. The results provide information, for the first time, on the crystal chemical nature of these nanometer-size semiconductor particles studied in situ in the presence of an organic phase.