Novel Nucleic Acid-Assisted Ion-Responsive ECL Biosensor Based on Hollow AuAg Nanoboxes with Excellent SPR and Effective Coreaction Acceleration

Novel hollow AuAg nanoboxes (AuAg NBs) were designed for an innovative electrochemiluminescence (ECL) sensor to ultrasensitively detect Pb2+ and Hg2+ with the aid of DNAzyme and "thymine–Hg2+–thymine" ("T–Hg2+–T") structure. AuAg NBs are employed as an excellent surface plasma resonance (SPR) source, as well as an effective coreaction accelerator for the CoNi NFs/S2O82– system to greatly improve ECL performance. To detect Pb2+, the DNAzyme catalyzes the cleavage of ribonucleic acid targets into numerous small nucleic acid fragments, leading to an ECL signal. When Hg2+ is added, the thymine–thymine (T–T) mismatches of the Hg2+ aptamer bind Hg2+ to form the "T–Hg2+–T" structure, which not only inhibits the SPR process but also produces a large steric hindrance, thus quenching the ECL signal and allowing quantification of Hg2+. The novel ECL sensor quantifies Pb2+ in the range of 0.1 fM to 0.1 μM with a limit of detection of 0.07 fM and Hg2+ in the range of 10 pM to 1 μM with a LOD of 4.07 pM.