Optical properties and surface conditions of CdSe quantum dots

We prepare CdSe QDs having various surface conditions and note the change in emission according to the surface conditions. A chemical colloidal method is used to grow CdSe QDs with sizes between 3 and 5 nm. The QD size is determined by X-ray diffraction. We observe the increase of emission in CdSe QDs having fewer organic ligands on the surface and also surface-passivated CdSe QDs. It is understood that the low emission of QDs is induced due to the deep-trap levels of the imperfect surface and the attached ligands on the surface. The emission spectrum of CdSe QDs shows a blue shift as time passes. CdSe/ZnS QD size remains constant as time passes, while the CdSe core size decreases. Core/shell-structured CdSe QDs are safer than core CdSe QDs for use as biosensors.