Terbium-functionalized silica nanoparticles for metal ion sensing by fluorescence quenching

Abstract

We describe preparation of a new luminescent material based on silica nanoparticles functionalized with terbium (Tb3+) complex of a polyamino polycarboxylic chelator, which displayed fluorescence when dispersed in aqueous and organic solvents. The functionalized material, TbL@SiO2, was firstly characterized by FTIR, UV–Vis and photoluminescent (PL) measurements. Further, it was used for various metal ions sensing as monitored by fluorescence quenching, indicating the highest decrease for iron(III), copper(II) and cobalt(II) metal ions. The calculated Stern-Volmer constants (KSV) equalled 2.21 × 105 M−1 for Fe3+, 6.81 × 105 M−1 for Cu2+ and 9.26 × 105 M−1 for Co2+, while the resulted lower detection limits reached 0.17 μM, 0.10 μM and 0.13 μM for Fe3+, Cu2+ and Co2+ respectively. In addition, the quenching mechanism was investigated through lifetime measurements which revealed a dynamic nature upon increase of the transition metal ion concentration. This was evidenced by changes in the emission lifetime (from τ0 = 1600 μs to τq = 1102 μs, thus a decrease of 31% in lifetime in presence of 8.6 μM Cu2+), most probably due to the collision interactions that affected the energy transfer of the ligand towards terbium ions.