Emission ratiometric sensing for peroxyacetic acid using the codoping of Tb(III) and Eu(III) in MOF matrix: Energy competing between RE(III) via electron-rich ligands

Abstract

The determination and quantification of oxidants related with chemical engineering and chemical industry is always an important issue for modern analytical chemistry. In this paper, a series of electron-rich ligands were synthesized and confirmed by their single crystals. Their cyclic voltammetry curves suggested that they were sensitive towards oxidants. These electron-rich ligands were coordinated with Eu(III) and Tb(III) ions and doped into a MOF (metal-organic-framework) supporting matrix of bio-MOF-1. Here bio-MOF-1 denoted [Zn8(ad)4(BPDC)6O·2(Me2NH2)+]·G, ad = adenine, BPDC = 4,4′-biphenyl dicarboxylic acid, G = N,N-dimetylformamide and water. The resulting composite sample was analyzed and confirmed with SEM, XRD, N2 adsorption/desorption and ICP measurement. It was found that there was an energy competing between Eu(III) and Tb(III) emissive centers. The Eu(III) emission intensity was decreased with increasing peracitic acid concentration, but the Tb(III) emission intensity was increased, showing ratiometric sensing signal. Linear sensing behavior was observed with sensitivity as high as 8.01 and response time of ~93 s. The sensing mechanism was revealed as the energy competing between Eu(III) and Tb(III) ions. In the absence of peracitic acid, the dominant energy transfer was a Eu(III)-based one, showing strong Eu(III) emission and weak Tb(III) emission. After adding peracitic acid, ligand energy transfer for Tb(III) was enhanced but that for Eu(III) was compromised, leading to quenched Eu(III) emission and increased Tb(III) emission. A good sensing selectivity was observed and attributed to the protecting and buffering effect of supporting matrix bio-MOF-1.