A novel method to enhance quantum yield of silica-coated quantum dots for biodetection.

In this paper, based on selecting the appropriate type of quantum dots (QDs), a novel method is developed to enhance the quantum yield (QY) of silica-coated QD nanoparticles (SQDNPs). The effect of varying types of QDs on the QY after silica encapsulation is systematically studied. The results show that QDs with appropriate structure and composition of shells can much better retain the initial QY after silanization. The seven-layered shell/core QDs with QY of 47.8% nearly completely retain the original QY and is the best type among six types of QDs for silica modification. In the aspect of shell composition, the CdS plays an important role for QY retention since the lattice mismatch between CdSe and CdS is lower than that of CdSe and ZnS. After the appropriate type of QDs is chosen for silica coating, the highly fluorescent SQDNPs are chemically modified with amine, thiol and carboxyl groups, and then labeled by antibodies for particle-based immunofluorescence assay. The results indicate that the SQDNPs-antibody bioconjugates are alternative fluorescent probes useful for biodetection.