Study on the complexes between PAMAM dendrimer and Cd²⁺ and the preparation of CdS/PAMAM dendrimer nanocomposite

The complexation between PAMAM dendrimers and Cd²⁺ was studied by titrating PAMAM dendrimers with dilute cadmium acetate methanol solution under the monitoring of UV-Vis spectrophotometry. The results showed that the average number of Cd²⁺ complexed with a PAMAM dendrimer is 34 for a primary amine-terminated G5.0 dendrimer and 16 for an ester-terminated G4.5 dendrimer. A series of CdS/PAMAM dendrimer nanocomposites of different diameters were prepared by leading H₂S into the methanol solution of Cd ²⁺/PAMAM complexes with different Cd²⁺/PAMAM ratio. The gained CdS/PAMAM dendrimer nanocomposites were characterized by UV-Vis spectrophotometry and TEM. The study implied that G4.5 PAMAM dendrimers were better templates. The stability, diameter and dispersion of the CdS clusters were affected remarkably by the changes of the ratio of Cd²⁺ to G4.5 PAMAM dendrimer and pH of the solution. The results showed that in neutral solution the stability and the dispersion of CdS/PAMAM dendrimer nanocomposites were better and the diameters were smaller.