A versatile cathodic "signal-on" photoelectrochemical platform based on a dual-signal amplification strategy

Novel cathodic photoelectrochemical (PEC) aptasensors for sensitive and selective determination of thrombin and Pb²⁺ were developed based on a new dual-signal amplification strategy. The presence of gold nanoparticles (AuNPs) could quench the PEC signal of bismuth oxyiodide (BiOI). At the same time, the redox moiety G-quadruplex/hemin or ferrocene (Fc) was found to enhance the PEC signal of BiOI. So, in the presence of thrombin or Pb²⁺, the interaction between target and the aptamer resulted in the releasement of the AuNPs, as well as shorter distance between the redox moiety and the electrode surface. Hence dual-enhanced cathodic PEC biosensor strategy was realized. Under the optimized conditions, the detection limits of thrombin and Pb²⁺ were 17.3 fM and 3.16 pM, respectively with good selectivity. At the same time, the PEC performance of redox moiety G-quadruplex/hemin and Fc was compared.