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.

The mesoporous solid acid–base Cs–B–Zr mixed oxides were synthesized using the co-precipitation method followed by a subsequent thermal treatment. The catalytic activity of solid Cs–B–Zr mixed oxide was tested for solvent free acid–base catalysed direct alkylolamines with alcohols as green alkylating agent. The effects of Cs/B/Zr ratio, calcination temperature, reaction conditions, and reaction substrate on the catalytic performance of the catalysts were investigated. The XRD, N2 adsorption–desorption, ICP-OES, FT-IR and NH3/CO2-TPD results showed that the mesoporous structure and acid–base properties of the catalysts play important roles in the reaction. A suitable number of acid and basic sites on the catalyst lead to a high activity for the N-alkylation reaction.

We herein designed a ratiometric fluorescent probe by hybridizing fluorescein isothiocyanate-doped silica nanoparticles with CdTe/CdS quantum dots and demonstrated its efficiency for visual detection of Hg2+. The color of the solution gradually turned from red to green along with the increase of Hg2+ concentration.