A multicolor electrochemiluminescence device based on closed bipolar electrode for rapid visual screening of Salmonella typhimurium

A multicolor electrochemiluminescence (ECL) device was constructed based on closed bipolar electrode (BPE) for visualized sensing of Salmonella typhimurium (S. typhimurium). Since the emission color of concomitant electrochemiluminophores ([Ir(ppy)3] and [Ru(bpy)3]2+) is potentially distinguish, selective excitation of ECL could be obtained by regulating the interfacial potential at the poles of BPE. Via modulating the resistance of BPE, bidirectional color change from dark-orange to yellow to forest-green could be observed at the anode, which was ascribed to the dual-potential excitation property of the concomitant electrochemiluminophores. The presence of S. typhimurium on the cathode of BPE increases the resistance in the circuit, generating ECL reporting color at the other pole switched. In accordance with this multicolor BPE-ECL sensor, a low detection limit of 10 CFU mL−1 of S. typhimurium could be identified in 25 mL (g) sample with naked eyes. In this work, physical isolation of the cathode and anode of closed BPE not only avoids target and electrochemiluminophores mutual interference, but also the surface of the BPE need nothing modified, just added immunomagnetic beads (IMBs)-S. typhimurium compound to the cathode. Moreover, without complex pre-enrichment bacterial, the whole experiment time also can be greatly shortened with only 0.5 h. On the other hand, the electrochemical signal is converted into a more intuitive optical readout for visualized sensing of S. typhimurium in food. The multicolor ECL device is merging the sensitivity of electrochemistry with the intuitive of an optical readout, which may apply in the site of rapid detection of food safety.