Cyclometallated ruthenium complex-modified upconversion nanophosphors for selective detection of Hg2+ ions in water.

Upconversion detection nanocomposites were assembled for the selective luminescent detection of mercury ions in water. A hydrophobic cyclometallated ruthenium complex [Ru(II)(bpy)2(thpy)]PF6 (abbreviated as Ru1; bpy = 2,2'-bipyridine and thpy = 2-(2-thienyl)pyridine) is employed as a chemodosimeter to assemble on amphiphilic polymer-coating upconversion nanophosphors (UCNPs) based on the hydrophobic-hydrophobic interaction. Upon addition of Hg(2+), the nanocomposite not only exhibits a remarkable color change from deep-red to yellow, but also an enhanced upconversion luminescence (UCL) emission by hindering the luminescent resonance energy transfer (LRET) process from the upconversion emission of UCNPs to Ru1. Using the ratiometric UCL emission as a detection signal, the detection limit of Hg(2+) for this nanoprobe in aqueous solution is 8.2 ppb, which is much lower than that (329 ppb) determined by UV/Vis technology. Such an Hg(2+)-tunable LRET process provides a general strategy for fabricating a water-soluble upconversion-based nanoprobe for some special analyte.