A novel luminescent optical fibre probe based on immobilized tridentate bis(phosphinic amide)-phosphine oxide for europium(III) ion aqueous detection in situ

A novel optical fibre probe based on a tridentate bis(phosphinic amide)-phosphine oxide PhPO(C6H4POPhN(CH(CH3)2)2)2 (ligand 1) has been developed for the detection of europium(III) ions in water. The dip coating technique was used to deposit the ligand 1 encapsulated on a poly(vinyl chloride) membrane onto an optical fibre. The optimum deposition thickness of the membrane was 280 ± 40 nm. The sensing mechanism relies on the reaction between europium(III) ion and ligand 1, which produces a strong luminescent complex of stoichiometry 1:2 Eu(III):Ligand 1 with a maximum emission peak around 612 nm. Two different configurations, aerial and aqueous, were tested for measuring the luminescence off-line and on-line, respectively. The proposed probe showed a response time of 92 s in the aqueous configuration (in situ detection of europium(III) ions in water). The luminescence of the proposed probe displayed a power-law response for the europium(III) concentration in a broad range of concentrations of at least 5 orders of magnitude, from 10 nM to 1 mM, with a correlation coefficient (R2) of the fitted curve better than 0.99.