Novel Bi₂₊WO₆ p-n Homojunction Nanostructure: Preparation, Characterization, and Application for a Self-Powered...

Synthesizing novel cathodic photoactive materials with high photoelectrochemical (PEC) performance is urgently important for the development of photocathodic sensors. Herein, a novel photocathode material, Bi self-doped Bi₂WO₆ (i.e., Bi₂₊WO₆) p-n homojunction, is prepared via a simple ethylene glycol-assisted solvothermal reduction for the first time. Compared with pristine Bi₂WO₆, Bi₂₊WO₆ possesses a narrower band gap and higher light harvesting ability. Among the synthesized materials, Bi_2.1WO₆ exhibits the highest photocurrent response, which is 23 times that of pure Bi₂WO₆ because of the synergistic effect of doped Bi and the p-n homojunction. The open circuit potential, "V-shaped" Mott-Schottky plot, linear sweep voltammetry curve, and transient photocurrent demonstrate the p-n homojunction characteristics of the material well. By using the Bi₂₊WO₆ p-n homojunction as the photocathode for sensing and the plasmonic WO₃/Au composite as the photoanode for signal amplification, a new self-powered membraneless PEC immunosensor is established for a highly sensitive detection of human epididymal protein 4. This study offers a new idea for designing novel photocatalysts with satisfactory performance, and the Bi₂₊WO₆ p-n homojunction is expected to act as a promising PEC platform for developing various self-powered biosensors.