Ultrasensitive photoelectrochemical platform with micro-emulsion-based p-type hollow silver iodide enabled by low solubility product (K_(sp)) for H₂S sensing

Since visible-light (VL) accounting for massive solar radiation energy, a large amount of attention has been paid to the development of highly efficient visible-light-driven (VLD) semiconductor materials. However, despite recent efforts to construct VL active material, hollow structure-based silver iodide (AgI) with appropriate band gap and a large surface area are limited because of lack of a proper synthesis method. Herein, hollow AgI with p-type semiconductor behavior is constructed on the basis of micro-emulsion strategy, which enables admirable cathode photoelectrochemical (PEC) response. The as-prepared hollow AgI is applied to fabricate the PEC sensing platform and reveals a low limit of detection of 0.04 fM and a wide dynamic range up to 5 orders of magnitude toward H₂S. The PEC sensing mechanism is supposed to the 'signal-off' pattern on account of the ultralow solubility product (K_(sp)) of Ag₂S, derived from the precipitation reaction due to the high affinity between sulfide ion and Ag⁺. Besides, the hollow structure of AgI provides sufficient surface area for in situ producing Ag₂S that serves as recombination center of carrier, thus causing the efficient quenching of photocurrent signals. This work broadens the horizon of structuring VLD semiconductor nanomaterials and K_(sp)-based H₂S sensing.