Efficient Synthesis of Highly Photoluminescent Short Dendritic CdSeS/ZnS Quantum Dots for Biolabeling

A convenient and efficient approach is reported to synthesize CdSeS with low-cost and low-toxic materials. The influence of the Se/S ratio and reaction time on the photoluminescent properties of CdSeS QDs is investigated through researching the temporal evolution of the absorption and the emission. Following, the high photoluminescent short dendritic green-emitting CdSeS/ZnS QDs are prepared using the method inspired by the successive ion layer adsorption and reaction procedure, which are composed of a CdSeS core and ZnS branches. Transmission electronic microscopy and X-ray diffraction show that the CdSeS/ZnS QDs is in a cubic zinc blende structure. The photoluminescence intensity increase significantly when the ZnS branches form as a result of the charge carriers being confined in the core. The photoluminescence quantum yield of the obtained CdSeS/ZnS core-shell QDs can be up to 90%, which is much higher than that of initial CdSeS QDs (39%). In addition, CdSeS/ZnS QDs have good photoluminescence intensity after they are transferred from organic solvent into aqueous media through ligand replacement using mercaptoacetic acid. Afterwards, the E. Coli O-157 are not only successfully conjugated with CdSeS/ZnS QDs but also present clear images under UV irradiation.