Enhancement of photoluminescence of different quantum dots by Ag@SiO2 core–shell nanoparticles

The enhancement of photoluminescence of several quantum dots, namely CdS/ZnS, Cd0.3Pb0.7S and pure ZnS, by Ag@SiO2 core–shell nanoparticles is studied and reported in this work. 3-Aminopropyltriethoxysilane (APS) was used to link QDs to the core–shell nanoparticles. For CdS/ZnS, the Ag@SiO2 nanoparticles showed a maximum enhancement of about 2.5 due to surface plasmon resonance of silver particles when the shell thickness was 16 nm. When the shell thickness increased to 30 nm, the enhancement effect became negligible. Conversely, when the thickness decreased to 6 nm, the effect was also smaller due to possible capture of excited electrons by silver particles. For Cd0.3Pb0.7S, a similar enhancement effect was observed. However when pure ZnS was the QD, the photoluminescence went zero after the QD was linked to Ag@SiO2 nanoparticles. This was caused by the fact that for ZnS QDs, the emission wavelength was 415 nm, which also corresponds to the absorbance peak of silver particles.