Au NPs@SiO2 assisted solid-state electrochemiluminescence sensor of Cu4RuO5 for ultrasensitive detection of tilmicosin in milk

In this study, a porous bimetallic oxide Cu 4 RuO 5 with a high specific surface area was prepared via electrospinning followed by high-temperature calcination. This oxide exhibited a significant electrochemiluminescence (ECL) signal when reacting with S 2 O 8 2− . Utilizing this bimetallic oxide as an ECL material, we constructed a simple solid-state ECL sensor, in conjunction with Au NPs@SiO 2 , for the sensitive detection of tilmicosin in milk. The sensor was constructed using a layered modification approach. Initially, the bimetallic oxide Cu 4 RuO 5 was modified onto the electrode surface. Cu 4 RuO 5 not only serves as a luminescent reagent but also promotes electron transfer within the system due to its large specific surface area and porosity, achieving amplification of the first-stage ECL signal. Subsequently, Au NPs@SiO 2 was modified onto the oxide surface. The SiO 2 shell effectively shields the system from complex matrix interferences while providing a large specific surface area for the immobilization of Au NPs. The Au NPs further accelerate electron transfer, thereby achieving amplification of the second-stage signal. Based on this two-step amplification strategy, the constructed ECL sensor exhibits a linear response range for tilmicosin from 1.0 × 10 −13 to 1.0× 10 −6  mol L −1 , yielding a detection limit of 2.01 × 10 −14  mol L −1 (3σ/m). This sensor combines high sensitivity, good selectivity, and excellent stability, providing a novel method for the rapid determination of antibiotic residues in food, successfully implemented to enable rapid determination of tilmicosin in milk matrices.