Ratiometric fluorescent sensor with molecularly imprinted mesoporous microspheres for malachite green detection

A dual-emission molecularly imprinted mesoporous microspheres was designed for specific recognition and highly sensitive and selective determination of malachite green (MG). In this ratiometric fluorescent sensor, green fluorescent CdTe quantum dots (QDs)-doped into the core of silica mesoporous microspheres serves as a reference and provides a built-in correction for environmental effects. The other red fluorescent CdTe QDs are embedded around the pores of the silica microspheres as analytical tag. Then, molecular imprinting technique are integrated with the ratiometric sensor to provide high selectivity for MG. When the photoluminescence (PL) of red CdTe QDs is selectively quenched in the presence of MG, a visual color change from orange to green can be observed by naked eyes. The sensing method has a linear response in the range of 27.4 nM-137 μM with a detection limit of 17.0 nM. Moreover, there is an excellent recognition specificity for MG over other water pollutants. The applicability of this method is evaluated through the determination of MG in river water and lake water samples with satisfactory results.