SIZE-DEPENDENT STRUCTURE AND DYNAMICS OF CDS NANOCLUSTERS

CdS nanoparticles with diameters from 14 -120 Angstrom and very narrow size distributions are studied by x-ray absorption fine structure spe ctroscopy between 5 and 296 K. Clear trends in the Cd-S distance as a function of size and surface stabilization of the nanoparticles could be observed. Particles with thiols as ligands show an expansion of the Cd-S distance with decreasing particle size whereas polyphosphate sta bilized samples are slightly contracted with respect to CdS bulk. The static disorder of the nanoparticles is enlarged with respect to the b ulk. In contrast, the dynamic behavior of the nanoparticles shows a sl ight stiffening of the Cd-S vibration with decreasing particle size. M easurements of the third moment of the pair distribution function indi cate the possibility to distinguish between cubic and hexagonal struct ures in CdS nanoparticles.