Controlled synthesis of a dual-emission hierarchical quantum dot hybrid nanostructure as a robust ratiometric fluorescent sensor

Constructing robust dual/multi-emission fluorescence nanoparticles with tunable intensity ratios and colors is of particular interest in highly sensitive ratiometric probe development. Herein, we have fabricated a novel silica-coated dual-emission hierarchical hybrid nanostructure (CdTe@SiO2@CdTe@SiO2), with two sizes of CdTe quantum dots (QDs) that were spatially separated, which was composed of green-emitting QDs grown in situ on the surface of silica nanoparticles embedded with red-emitting QDs. Both fluorescence intensity ratios and colors can be effectively adjusted by simple control of refluxing time or precursor concentrations of the outer QDs. This complex CdTe@SiO2@CdTe@SiO2 nanoparticle exhibited stronger photo- and chemical-stability as well as better biocompatibility than previously reported QDs-silica-QDs analogues. As a proof of principle, the dual-emission fluorescent silica nanohybrid was used as a reliable ratiometric probe to precisely monitor gold nanoparticle concentration through a fluorescence energy transfer mechanism.