The Synthesis and Mercury-Recognizing Skill of Two Emission "Turn-On" Rhodamine Derivatives Excited by Rare Earth Up-Conversion Lattice.

The present paper focused on the synthesis and Hg(II)-sensing behavior of two rhodamine derived probes. Up-conversion NaYF4 nanocrystals were constructed and applied as the excitation host so that those probes could be lightened by the 980 nm excited up-conversion emission, aiming at better probe photostability. The efficient energy transfer between the up-conversion host and the probes was analyzed and confirmed by spectral analysis and emission decay lifetime comparison. The probes followed a simple complexation stoichiometry of 1:1 with Hg(II) ions. Then two sensing composite systems containing the up-conversion host and the probes were established. Their sensing performance, including spectral response, Stern-Volmer plots, emission stability and selectivity, was explored in detail. It was found that the probe emission linearly increased with increasing Hg(II) ions while was immune to other common metal ions, showing emission "turn-on" effect towards Hg(II) ions with good selectivity.