Effects of glutathione on the luminescent behavior of CdSe-nanocrystals

Abstract

The luminescent behavior of semiconductor nanocrystals is a sensitive reporter of their electronic properties and of the impact of surface passivation on the excitonic state.In this work, CdSe nanocrystals (CdSe-Nc) are prepared in microemulsions and the effects of tripeptide Glutathione (GSH) as a stabilizing ligand, are examined. The CdSe samples are investigated by steady-state and time-resolved luminescence methods. The luminescent properties of CdSe without GSH spectrally evolve over time, and a dramatic reduction of luminescence intensity and decay times are observed. This behavior suggests that although the colloids are in microemulsion media, they undergo progressive aging that ruins their luminescent properties. The presence of GSH in the microemulsions at the beginning of the synthesis stops the nanocrystal aging, thus acting as an efficient stabilizing agent, freezing the luminescence properties of CdSe nanocrystals. The effects of GSH on the colloids are also documented by a detailed analysis of luminescence decay times, carried out through the Maximum Entropy Method. Interestingly, the addition of GSH on aged CdSe colloids is able to not only stabilize the structures but also recover the luminescent efficiency leading to an attractive “brightening” effect.