Defect-driven efficient charge transfer pathways for signal-amplified electrochemiluminescence aptasensing:...

The performance of electrochemiluminescence (ECL) biosensors is highly influenced by the charge transfer efficiency of the substrates. To address the intrinsic limitations of traditional semiconductors, magnesium ions (Mg²⁺) doped titanium dioxide (MTO) has been designed in this study based on the defect-engineered strategy, aiming to construct efficient charge transfer pathways and catalytic interfaces by precisely regulating the band and electronic structures. Specifically, the aliovalent Mg²⁺ on titanium ions (Ti⁴⁺) induced lattice distortion and charge imbalance. Oxygen vacancies generated spontaneously to compensate for the charge imbalance. Electrons released from oxygen vacancies reduced Ti⁴⁺ (3d⁰) to Ti³⁺ (3d¹). Concurrently, density functional theory (DFT) calculations confirmed that a defect level contributed by Ti 3d orbitals was introduced within the band gap. This defect level provided an efficient channel for electron transport, while the Ti³⁺/Ti⁴⁺ redox pair significantly enhanced the electrocatalytic activity towards co-reactants. The results showed that the MTO improved the ECL signal of luminophore by 278.6%, significantly outperforming pure TiO₂ (155.5%). An aptasensor was constructed by applying this defect-engineered MTO as the sensing substrate for detecting domoic acid, providing a robust platform for ultra-trace analysis.