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Sodium bisulfite is a food additive, and its excessive intake can be harmful to human health. In this work, a new method for detecting bisulfite was developed based on the Etch-Cu-HCF nanozyme with enhanced polyphenol oxidase-like (PPO-like) activity. The Etch-Cu-HCF nanozyme was obtained from the ammonia erosion of the Cu-HCF nanozyme, and its PPO-like activity was enhanced by nearly 100% than that of the Cu-HCF nanozyme. It is possible that the Cu/Fe ratio of Etch-Cu-HCF increased after ammonia etching and more copper active sites were exposed. In addition, based on the PPO-like activity of the Etch-Cu-HCF nanozyme, 2,4-dichlorophenol (2,4-DP) can be oxidized to its corresponding quinone-like product, which can combine with 4-aminoantipyrine (4-AP) to obtain colorful products with UV absorption at 510 nm. However, the quinone-like product can be consumed by bisulfite via an addition reaction, which reduces the binding of the quinone-like product to 4-AP, resulting in a decrease in the UV absorbance of the system at 510 nm. Therefore, a new method for the detection of bisulfite was developed. The detecting range was 0–50 μM, and the detecting limit was 0.47 μM. The method has good selectivity and was successfully applied for the analysis of bisulfite in food. [ABSTRACT FROM AUTHOR]

A metal-free tandem double hydrophosphination of extended conjugated indandiones has been established. Mechanistic investigations confirmed the consecutive manner of the nucleophilic addition reaction. Complexation of the generated keto-diphosphine resulted in the formation of an unexpected tridentate bridging ligand with an anionic P,O-bidentate and a neutral P-monodentate coordination mode on two palladium units. In the presence of an external chiral auxiliary, the coordinated diphosphines could be separated into their enantiomeric forms. [ABSTRACT FROM AUTHOR]