Structure Evolution of CdSe Nanocrystals During Ripening Process Studied by XAFS

The structure evolution of CdSe nanocrystal with different grown sizes (1.9, 2.7 and 3.1 nm, respectively) obtained by size-selective method from colloidal solution is investigated by XAFS. By such purposeful design of samples, we have investigated the isolated ripening process effect on the structure of nanocrystals. The Se K-edge XAFS results of CdSe nanocrystals show that structure disorder of nanocrystal increases from 0.0046 Å to 0.0053 (0.0072) Å while its size grows from 1.9nm to 2.7 (3.1) nm during the ripening growth process. We propose that during ripening process the growth of CdSe nanocyrstal is through the deposition of Cd and Se ions on the surface of CdSe nucleate, and as a consequence, the defects on the nucleate surface lead to larger structural disorder of the resulting CdSe nanocrystal.