Abstract
Since semiconductor nanocrystal has great potential in biological labeling, the surface chemistry behavior of nanocrystal at liquid-solid interface is of great research interest. To maintain very small (2∼6nm) and narrow distributed (<5%) diameter under certain conditions, it is necessary to coat nanocrystals with appropriate surfactants. However there is little study about the surface replacement reaction kinetics of semiconductor nanocrystals. In this study, it is proposed to analyze the reaction modifying the nanocrystal surface. CdSe/ZnS-TOPO nanocrystal was modified with MUA (mercaptoundecanoic acid) that molecule is generally employed to become CdSe/ZnS-TOPO nanocrystals water-soluble. Some samples were taken at intervals in the modifying process and measured IR spectrum. The quantity of MUA adsorbed on the surface was estimated by the absorption around 1600 cm-1 that indicated -COO- group amount. We found that, at initial, there were already MUA bond with nanocrystal. We also found that rate determining step is not the MUA absorption but TOPO desorption reaction.
