Dye-assembled nanocomposites for rapid upconversion luminescence sensing of Cu2+

Abstract

An upconversion luminescence (UCL) probe for the detection of Cu2+ is constructed by assembling meso-tetra(4-sulfonatophenyl)porphine dihydrochlorid (TSPP) on SiO2-encapsulated β-NaYF4:Yb,Er,Gd nanorods which were synthesized by hydrothermal reaction and encapsulated with a layer of ultrathin silica through a water-in-oil reverse microemulsion strategy. Under excitation of 980nm, the nanorods emit upconversion lights at 545nm and 659nm, respectively. While in the presence of Cu2+, Cu2+ forms complex with TSPP, which shifts the maximum absorption of TSPP from 515 to 545nm. As the maximum absorption of TSPP-Cu2+ is overlapped with the emission at 545nm of the nanorods, the luminescence energy of the nanorods can be transferred to TSPP–Cu2+ complex, resulting in a quench of the emission at 545nm, while the upconversion emission at 659nm is not affected by Cu2+, and can be used as a reference. Cu2+ was therefore quantified based on the ratio of the upconversion luminescence at 545 to that at 659nm. Using the ratiometric upconversion luminescence as detection signal, the nanoprobe shows high selectivity and sensitivity towards Cu2+ with a limit of detection of 2.16μM, and a quick response time of within 10s. The analysis of Cu2+ in Hela cell lysates indicates the potential applications of this nanoprobe in the near-infrared fluorescent imaging of Cu2+ in cells.