NUCLEATION AND GROWTH OF PBS NANOCRYSTALS AND SIMULATION OF X-RAY-DIFFRACTION PATTERNS

Ultrasmall particles of lead sulfide were synthesized from lead ions a nd long-chain thiols in a non-aqueous medium. The growth of nanocrysta ls with the macroscopic rocksalt lattice (up to size > 10 nm) proceeds through several steps: Pb-thiolate complexes with no solid phase, sma ll nuclei at the beginning of crystal lattice formation, and nanometer particles with a bulk-like structure. This process is studied by X-ra y diffraction (XRD), scanning tunneling microscopy (STM), and atomic f orce microscopy (AFM). XRD patterns are simulated with sufficiently go od fit to the experiment for rocksalt-type model lattices including 27 , 75, 125, and 729 atoms. Lead sulfide particles formed at the differe nt steps show the pronounced quantum-size effect in optical spectra, T hey can be precipitated from colloids in the form of a stable solid ph ase. (C) 1998 Published by Elsevier Science B.V. All rights reserved.