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

An upconversion luminescence (UCL) probe for the detection of Cu 2+ is constructed by assembling meso-tetra(4-sulfonatophenyl)porphine dihydrochlorid (TSPP) on SiO 2 -encapsulated β-NaYF 4 :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 980   nm, the nanorods emit upconversion lights at 545   nm and 659   nm, respectively. While in the presence of Cu 2+ , Cu 2+ forms complex with TSPP, which shifts the maximum absorption of TSPP from 515 to 545   nm. As the maximum absorption of TSPP-Cu 2+ is overlapped with the emission at 545   nm of the nanorods, the luminescence energy of the nanorods can be transferred to TSPP–Cu 2+ complex, resulting in a quench of the emission at 545   nm, while the upconversion emission at 659   nm is not affected by Cu 2+ , and can be used as a reference. Cu 2+ was therefore quantified based on the ratio of the upconversion luminescence at 545 to that at 659   nm. Using the ratiometric upconversion luminescence as detection signal, the nanoprobe shows high selectivity and sensitivity towards Cu 2+ with a limit of detection of 2.16   μM, and a quick response time of within 10   s. The analysis of Cu 2+ in Hela cell lysates indicates the potential applications of this nanoprobe in the near-infrared fluorescent imaging of Cu 2+ in cells.