Synthesis, functionalization and photoelectrochemical immunosensing application of WO3-based semiconductor materials

Photoelectrochemical (PEC) immunosensing, as an essential direction of PEC bioanalysis, has attracted substantial research in the analytical and biological science due to its desirable combination of high sensitivity of PEC signal detection and high specificity of immune-reactions. Photoelectrode material, as the suits of photo-to-electric converter and signal generator, mainly determines the performances of PEC immunosensor. Thus, the exploitation and preparation of semiconductor materials with excellent PEC performance have become a research hotspot in PEC immunoassay field. With moderate band gap (2.5–2.8 eV), high valence band potential (>3.0 eV), good resistance to photo-corrosion, low toxicity and high biocompatibility, WO3 has been widely investigated and applied in the PEC immunosensing filed as a good photoelectrode material. This paper comprehensively reviews the synthesis, functionalization and immunosensor applications of WO3 materials in recent years. It focuses on six functionalization methods of WO3, including morphology modulation, crystal facet tailoring, element doping, hetero/homojunction construction, metal deposition, and dye sensitization, and highlights the impacts of functionalization on their morphology, composition, structure and properties. More importantly, from the perspective of immunoassay formats (i.e., unlabeled and labeled immunoassay), the signal amplification strategies and sensing mechanisms of WO3-based PEC immunosensors are discussed in detail. Finally, the challenges and opportunities for the WO3-based PEC immunosensors are prospected.