A MOF-on-MOF based photoelectrochemical sensor for hydrogen sulfide detection in food quality assessment

The development of high-selectivity and high-sensitivity detection methods for hydrogen sulfide (H2S) released during food spoilage has become a prominent research focus. This study presents a novel photoelectrochemical (PEC) sensor based on a MOF-on-MOF structure for detecting H2S released during food spoilage. The composite material is assembled by van der Waals forces (vdW) from two MOFs, namely Cu-HHTP and Zn-TCPP. CuHHTP@Zn-TCPP exhibits significant photocurrent quenching due to electron transfer from Zn-TCPP to Cu-HHTP, reducing the availability of free charge carriers. Upon reaction with sulfides, the copper nodes in Cu-HHTP coordinate with sulfur to form CuS, which inhibits the transfer of electrons from Zn-TCPP to Cu-HHTP, thereby decreasing electron consumption. This allows a greater number of electrons to participate in the reaction to generate superoxide radicals (& sdot;O2- ), resulting in a recovery of photocurrent response. Based on this "signalon" strategy, a PEC sensing method for sulfide detection has been successfully established, exhibiting a wide linear detection range (0.1 - 1500 mu M) and a low detection limit (0.62 mu M). Furthermore, by integrating a smartphone with a miniaturized electrochemical analyzer, a portable PEC sensing platform with high sensitivity and selectivity has been constructed, enabling precise detection of H2S released during the spoilage of various foods, such as egg, pork, and shrimp. This proposed MOF-on-MOF PEC signal conversion mechanism may provide a new approach for further developing novel PEC sensing platforms.