J. Rockenberger et al., SIZE DEPENDENCE OF STRUCTURAL AND DYNAMIC PROPERTIES OF CDS-NANOPARTICLES, Berichte der Bunsengesellschaft fur Physikalische Chemie, 101(11), 1997, pp. 1613-1616
Citations number
13
Categorie Soggetti
Chemistry Physical
Journal title
Berichte der Bunsengesellschaft fur Physikalische Chemie
Temperature-dependent EXAFS (Extended X-ray Absorption Fine Structure)
measurements between 5 and 290 K show that structural and dynamic pro
perties of CdS nanoparticles with 13 - 120 Angstrom diameter depend on
their particle size and the way of surface stabilization. The mean Cd
-S distance of thiolcapped CdS nanoparticles (13-40 Angstrom) increase
s with decreasing particle size with respect to CdS bulk. In contrast,
mean interatomic distances in polyphosphate-stabilized particles (30-
120 Angstrom) are slightly contracted. This demonstrates that the cova
lently bound thiol ligands induce the nanocluster lattice expansion. F
rom the temperature dependence of the mean-square relative displacemen
t (MSRD), a slight stiffening of the Cd-S bond can be observed with de
creasing particle size. The static part of the MSRD, reflecting static
disorder of the Cd-S bond, exhibits a maximum al cluster sizes of abo
ut 30 Angstrom. For particles larger than 30 Angstrom diameter, the in
crease of the static disorder follows the change of the surface to vol
ume ratio. This ratio also determines the size dependence of the asymm
etry of the interatomic Cd-S pair potential. Furthermore, in CdS bulk
and CdS nanoparticles with the thermodynamically favored wurtzite stru
cture this asymmetry is significantly enlarged in comparison to nanopa
rticles with zinc blende structure.