Eu3+-postdoped MOFs are used for fluorescence sensing of TNP, TC and pesticides and for anti-counterfeiting ink application

Two europium-postdoped metal organic frameworks (MOFs) Eu3+@1 and Eu3+@2 [1:{[Zn2(bta)(bpy)(H2O)2]·2H2O}n, 2:{[Ni(bta)(bpy)(H2O)2][Ni(bpy)·(H2O)4]·4H2O}n (H4bta = 1, 2, 3, 5-benzenetetracarboxylic acid, bpy = 4, 4′-dipyridine)] were prepared by hydrothermal synthesis and post-synthesis modification. MOFs 1–2 are all three-dimensional network structure connected by (bta)4- and bpy ligands. Eu3+@1 and Eu3+@2 in aqueous solution can achieve the quantitative detection of 2, 4, 6-trinitrobenzene (TNP), tetracycline (TC) and pesticides with high sensitivity and selectivity. In particular, when the volume of TNP increases to 50 μL, the luminescence quenching rate of Eu3+@2 can reach 99.7% and the LOD for TNP can reach 78 nM. Interestingly, Eu3+@1 has a good response to PTH (Pyrimethanil), while Eu3+@2 has a good selectivity to FLU (Fluazinam), and both can be used for rapid in-situ imaging detection of simulated pesticide residues on fresh vegetables. Under UV lamp, Eu3+@1 showed a significant fluorescence quenching effect on PTH in beans, while the fluorescence quenching effect of Eu3+@2 on FLU on cabbage was obvious. Surprisingly, two kinds of composite materials can be used as anti-counterfeiting ink functional material with strong anti-counterfeiting ability and long term stability.