Contactless photoelectrochemical biosensors based on hierarchical MXene/BiS nanosheets with the branched hybridization chain reaction.

Ethyl carbamate, a substance frequently occurring in fermented foods, seriously affects people's health; however, poor sensitivity constrains the development of ethyl carbamate sensors. In this work, hierarchical BiS/MXene nanosheets were synthesized using a hydrothermal method, and experimentally their coupled UV light is an efficient NH sensing material. Meanwhile, the density functional theory (DFT) confirms that the MXene/BiS nanosheet interface has an excellent ability to adsorb NH, resulting in a change of photocurrent. As a proof-of-concept, a highly sensitive ethyl carbamate photoelectrochemical (PEC) biosensor was constructed based on the ammonia generation strategy of glutamate dehydrogenase coupled to the branched hybridization chain reaction (bHCR). Specifically, the target-triggered bHCR enriches a large number of enzyme-encapsulated liposomes, while the enzymatic NH-generation reaction will cause a change in the BiS/MXene photocurrent, which completes the target detection process. Under optimal conditions, the constructed PEC biosensors exhibited superior analytical performance toward ethyl carbamate in the range of 0.01 μg/mL to 1 μg/mL and limit of detection (LOD) down to 0.001 μg/mL. In addition, it offers an effective method for food safety monitoring due to its excellent stability, fast response, and maneuverability on real samples (red wine, yellow wine, and brandy).