A simple and sensitive detection method for the pesticide dichlorvos in solution using Eu(III)-β-diketonate as a luminescent probe

Abstract

We developed a novel detection method for the pesticide dichlorvos (2,2-dichlorovinyl dimethyl phosphate) in which tris[4,4,5,5,6,6,6-heptafluoro-1-(2-naphthyl)-1,3-hexanedionato]europium(III) [Eu(III)(hfnh)3] served as a highly sensitive luminescent probe. The photoluminescence intensity of Eu(III)(hfnh)3 was drastically and rapidly decreased by the action of dichlorvos in ethyl acetate. The quantum yield of Eu(III)(hfnh)3 decreased monotonically with increasing dichlorvos concentration, explaining the decrease in photoluminescence intensity. Dynamic and static quenching mechanisms possibly co-existed in ethyl acetate because the Stern–Volmer plot of Eu(III)(hfnh)3 and dichlorvos could be approximated by a quadratic function. 31P-NMR revealed that dichlorvos molecules coordinated to Eu(III) and exhibited dynamic behavior supporting a dynamic quenching mechanism. When dichlorvos was mixed with Eu(III)(hfnh)3 1, ΦET drastically decreased from 0.64 to 0.15. A plausible mechanism is that quenching of Eu(III)(hfnh)3 1 occurred between the dichlorvos molecules and the β-diketonates before energy transfer from the β-diketonates to Eu(III). Density functional theory calculations support this mechanism.