Fabrication of ratiometric molecular imprinting electrochemiluminescence sensor based on polyethyleneimine hydrogel loading layered bimetallic hydroxide and MIL-125@Ru(bpy)32+ for sensitive tetracycline detection

In this work, layered Co-Ni bimetallic hydroxide was synthesized and combined with polyethyleneimine hydrogel (PEI@LDH) as substrate material, then the metal-organic framework MIL-125 loaded Ru(bpy)₃²⁺ (MIL@Ru) was added as single luminophore, followed by electrochemical deposition of tetracycline (TC) imprinted copolymer of hydroquinone and o-phenylenediamine to construct an electrochemiluminescent (ECL) sensor for TC detection. The stable and sensitive luminophore MIL@Ru associating with co-reactant K₂S₂O₈ in the solution could cause a cathode ECL signal sensing TC, it could also associate with the immobilized co-reactant PEI hydrogel to produce a stable anode ECL signal acting as a reference. The LDH had catalysis and could efficiently amplify both anode and cathode ECL signals. Therefore, the constructed single luminophore based ratiometric ECL sensor displayed high selectivity, sensitivity and reproducibility. Under the selected testing conditions, the linear response range was 0.01 μmol L⁻¹ to 1 mmol L⁻¹ and the detection limit reached 8 nmol L⁻¹. Its good practicability was validated by determining TC in different actual samples. Hence, the ratiometric MIP-ECL sensor was quite promising.