High-efficiency upconversion luminescent sensing and bioimaging of Hg(II) by chromophoric ruthenium complex-assembled nanophosphors.

A chromophoric ruthenium complex-assembled nanophosphor (N719-UCNPs) was achieved as a highly selective water-soluble probe for upconversion luminescence sensing and bioimaging of intracellular mercury ions. The prepared nanophosphors were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDXA), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Further application of N719-UCNPs in sensing Hg(2+) was confirmed by optical titration experiment and upconversion luminescence live cell imaging. Using the ratiometric upconversion luminescence as a detection signal, the detection limit of Hg(2+) for this nanoprobe in water was down to 1.95 ppb, lower than the maximum level (2 ppb) of Hg(2+) in drinking water set by the United States EPA. Importantly, the nanoprobe N719-UCNPs has been shown to be capable of monitoring changes in the distribution of Hg(2+) in living cells by upconversion luminescence bioimaging.