Na3CA-assisted post-necking treatment of Bi4TaO8Cl photoelectrode for improved photoelectrochemical sensing of cysteine

Bi₄MO₈X-based nanomaterials exhibit promising potential for bioanalytical applications owing to their wide visible light absorption and strong affinity for thiol ligands. However, their photoelectrochemical (PEC) sensing performance is hindered by the low charge separation efficiency. In this study, particulate Bi₄TaO₈Cl photoelectrodes were prepared via a drop-coating method, and their charge separation behavior was optimized through trisodium citrate (Na3CA)-assisted post-necking treatment. This treatment facilitated the substitution of Na⁺ ions for Bi³⁺ ions, which enhanced oxygen vacancy generation. Additionally, it improved inter-particle connectivity. Benefiting from these modifications, the newly fabricated Na-Bi₄TaO₈Cl photoelectrode demonstrated significantly enhanced charge separation and transfer efficiency. Subsequently, a visible-light-driven PEC sensor based on the Na-Bi₄TaO₈Cl electrode was developed for cysteine detection, leveraging the specificity of Bi-S bond. Under visible-light irradiation, the PEC sensor exhibited superior PEC detection performance for cysteine, achieving a sensitivity of 360.00nA·cm⁻²·mM⁻¹ and a linear detection range of 0–3.00 mM. The sensor also demonstrates good selectivity and stability. Moreover, it showed satisfactory recoveries in the detection of cysteine in real samples such as egg white. All these prove the practicability of the PEC sensor. This work provides a novel strategy for designing advanced nanomaterials for biological sensing applications.