Quantum Dot-Encoded Mesoporous Beads with High Brightness and Uniformity:  Rapid Readout Using Flow Cytometry

A new generation of optically encoded beads has been prepared by using mesoporous polystyrene beads and surfactant-coated semiconductor quantum dots. In comparison with nonporous beads of similar sizes and chemical compositions, the encoded porous beads are approximately 1000 times brighter and 5 times more uniform in fluorescence intensities. Using both absolute intensity and ratiometric fluorescence coding, we show that the beads can be identified with a standard flow cytometer at 1000 beads/s. This result indicates that the multiple excited-state lifetimes and relaxation pathways of quantum dots do not limit their applications in high-speed optical detection and imaging.