Quantum dots (QDs) are nanocrystals with particle sizes less than 10 nm . Cadmium sulfide (CdS) quantum dots were used for selective biosensing of Staphylococcus aureus and proteomics . It can be used as a surface for the analysis of several analytes using SALDI-MS . It enabled soft ionization offering the analysis of labile compounds such as metallodrugs . It can also be used for fluorescence spectroscopy . CdS QDs were insitu grown into chitosan (CTS) enabling CdS QDs@CTS . The material CdS@CTS exhibited selective interaction with Cu 2+ due to the formation of Cd1-xCuxS . The positive charge on chitosan exhibited also high interaction with the negative charge on the bacteria cell membranes . CdS@CTS was also reported as a carrier for drug delivery of a natural anticancer drug called sesamol .