Semiconductor CdS:Mn/ZnS quantum dots for sensing applications

Since past several years, quantum dot (Qdot) nanotechnology has advanced our capabilities towards sensitive and reliable imaging of biological specimens such as cells, tissues etc. It is well understood that surface passivation is extremely important in obtaining bright and photostable Qdots. Traditionally, an inorganic wide band-gap epitaxially-matched shell material (such as ZnS, ZnSe etc.) is used over the Qdot core (such as CdS, CdSe etc.). Surface passivation minimizes surface related defects and improves quantum efficiency as well as photostability. This is also applicable to dopant based Qdots such as CdS:Mn/ZnS Qdots. In this work we present our research data on CdS:Mn/ZnS Qdots that are further surface modified with appropriate organic ligands for selective sensing applications. These ligands are capable of quenching Qdot luminescence via electron transfer process. Qdot luminescence is restored when electron transfer process is blocked. Using this quenching mechanism, we have demonstrated selective sensing of cadmium ions, alkali metal ions and glutathione in a highly sensitive manner.