Aggregation-induced upconversion enhancement and application based on rhodamine derivatives

In this work, we firstly report that one-photon absorption-based upconversion (oPUC) exhibits aggregationinduced emission enhancement (AIEE) based on rhodamine chromophores. Under excitation of 655 nm CW diode laser, the maximum upconversion intensity presents similar to 27-fold increase in the concentration range of 1 mu M-1 mM (while the Stokes fluorescence has already completely quenched at this moment). It was demonstrated that such AIEE feature is attributed to the upconversion radiative decay being activated in the more concentrated solution. A turn-on chemsensor rhodamine thiospirolactone (RhS) was synthesized for the application. The results demonstrated that the oPUC detection with AIEE feature can probe Hg2+ in the range as wide as 0-1.0 mM, showing the potential application of this upconversion detection in the large concentration and wide range ion probing.