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

Abstract

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.