Synthesis and luminescence of (3-mercaptopropyl)-trimethoxysilane capped CdS quantum dots

A new synthesis method is presented to make CdS quantum dots in THF and MeOH with mercaptopropyl-trimethoxysilane (MPS) as silica precursor at the surface. The thiol group acts as capping agent of the CdS surface. By varying the MPS concentration, the size and thus the emission colour could be tuned. Nanocrystals with a diameter between 2 and 6 nm could be prepared this way with quantum yields up to almost 20%. The temperature dependence and the lifetime of the emission were studied and explained in terms of a recombination process in which both a trapped electron and hole are involved. The CdS nanocrystals were doped with Zn or Cu resulting in a blue shift a red shift of the emission, respectively.