Synthesis of glutathione-capped US quantum dots and preliminary studies on protein detection and cell fluorescence image

A series of glutathione (GSH)-capped aqueous CdS quantum dots (QDs) with strong photoluminescence (PL) were prepared by changing the reaction temperatures and times on the basis of optimization of the mole ratio of S to Cd. The reaction time was shortened to about 1/10 compared with that reported previously by increasing the reaction temperature. The absorption and fluorescence spectra indicated good optical properties with PL full width of half-maximum (FWHM) of about 100 nm. The excitation spectrum was broad and continuous in the range 200-480 nm. The PL quantum efficiency (QE) of the prepared QDs was about 36% compared with rhodamine 6G (95%). The shape and size of the CdS QDs were characterized using high-resolution transmission electron microscopy (HRTEM). The prepared QDs were conjugated with bovine serum albumin (BSA) and onion inner pellicle cells and used as fluorescence probes for the first time. The results demonstrated that the fluorescence of CdS can be enhanced by BSA and the enhanced fluorescence intensity is proportional to the concentration of BSA in the range 1.0-10 mg/L. The aggregation of CdS in onion inner pellicle cells and its fluorescence images indicated that the QDs can aggregate around cells soaked for 8 h in CdS solution but enter the interior of cells and become aggregated to the nucleus when they are soaked in CdS solution for longer, e.g. 98 h. Copyright (C) 2007 John Wiley & Sons, Ltd.