In-situ synthesis of CdS-ZnS core-shell structure quantum dots inside PAMAM dendrimer templates

CdS-ZnS core-shell structure quantum dots (QDs) were in-situ synthesized inside PAMAM dendrimer templates of generation 4.5 (containing 64 ester end groups). The size distribution of the well-dispersed QDs was narrow and the average diameter was about 2.3 nm as shown in HRTEM images. The red shift of the absorption spectra suggested the formation of the core-shell structure. Also the EDS confirmed that the QDs were comprised of CdS and ZnS. ZnS shell of appropriate thickness effectively eliminated the noradiactive centers and the PL efficiency was improved to 31%. An organic shell covering the CdS-ZnS core-shell QDs formed via the PAMAM dendrimers, which prevented the conglomeration of QDs, passivated the hanging bonds and improved the PL efficiency. Furthermore, the excellent solubility of PAMAM dendrimers in solvents with different polarities endowed the QDs good solubility and made the QDs more stable.