Doping, as an important strategy, can change the conductivity type of semiconductor and has been used to construct p-n homojunction. However, the effect of doping style on the conductivity type has not been well ascertained. Herein, taking Bi₂WO₆ with layered crystal structure as the model, the effect of Bi doping type on the conductivity type of Bi₂WO₆ is studied through density functional theory (DFT) and experiments. Detailed investigations reveal that Bi substitutes W site rather than fills O site or interlayer, is critical for changing the conductivity type of Bi₂WO₆ (i.e. from n to p), thus producing a p-n homojunction structure in Bi₂WO₆ and enabling it cathodic photoelectrochemical (PEC) performance. To further study and improve the PEC properties of Bi-doped Bi₂WO₆ (marked as Bi_2+xWO₆), a novel p-n/n homo/heterojunction photocathode material of Z-scheme Bi_2+xWO₆/Bi₂S₃ has been synthesized by an in-situ ion-exchange reaction. Benefiting from the internal built-in electric field of homojunction and Z-scheme heterojunction, the bulk and interface charges of Bi_2+xWO₆/Bi₂S₃-3 (i.e. treated with 1 mM of Na₂S) are sufficiently separated and transferred, and thus a quite high cathodic photocurrent response occurs, which is about 5 and 100 times of those induced by Bi_2+xWO₆ and Bi₂S₃, respectively. To explore the applicability of this homo/heterojunction structure, a novel “signal-on” cathodic PEC immunosensor is constructed with Z-scheme Bi_2+xWO₆/Bi₂S₃-3 as substrate and self-assembled 3D Ti₃C₂@Au as label for the ultrasensitive detection of neuron-specific enolase (NSE). The immunosensor exhibits high sensitivity and selectivity.

掺杂作为一种重要的策略，可以改变半导体的导电类型，已被用于构建 pn 同质结。然而，掺杂类型对导电类型的影响尚未得到很好的确定。在此，以具有层状晶体结构的Bi ₂ WO ₆为模型，通过密度泛函理论(DFT)和实验研究了Bi掺杂类型对Bi ₂ WO ₆导电类型的影响。详细研究表明，Bi 取代 W 位点而不是填充 O 位点或中间层，对于改变 Bi ₂ WO ₆的导电类型（即从 n 到 p）至关重要，从而在 Bi _{2 中}产生 pn 同质结结构WO ₆并使其具有阴极光电化学 (PEC) 性能。为进一步研究和改善Bi掺杂Bi ₂ WO ₆ (标记为Bi _2+x WO ₆ )的PEC性能，Z型Bi _2+x WO ₆ /Bi ₂新型pn/n同质/异质结光电阴极材料S ₃是通过原位离子交换反应合成的。受益于同质结和Z型异质结的内建电场，Bi _2+x WO ₆ /Bi ₂ S ₃ -3 (即用1 mM Na₂ S) 被充分分离和转移，因此产生相当高的阴极光电流响应，分别是Bi _2+x WO ₆和Bi ₂ S ₃诱导的响应的5倍和100倍。为了探索这种同质/异质结结构的适用性，以Z-scheme Bi _2+x WO ₆ /Bi ₂ S ₃ -3 为底物和自组装3D Ti ₃ C构建了一种新型的“信号开启”阴极PEC免疫传感器₂ @Au 作为超灵敏检测神经元特异性烯醇化酶 (NSE) 的标签。免疫传感器表现出高灵敏度和选择性。