Gold Nanoclusters Decorated Hollow ZIF-8 Encapsulating Iron-catecholates as Oxidase Mimetics for Ratiometric Colorimetric Detection of Nitrite

Nitrite detection is of profound significance for guaranteeing food safety and avoiding poisoning incidents. Gold nanoclusters decorated hollow ZIF-8 encapsulating iron-catecholates (Fe-HHTP@HZIF-8@ AuNCs) was formed through self-assembly of Fe ³⁺ and 2,3,6,7,10,11 -hexahydroxytriphenylene (HHTP), in situ embedding of ZIF-8, and Au ³⁺ -Zn ²⁺ exchange reaction. Its morphology and structure were fully characterized by HRTEM, XRD, TEM element mapping and XPS. Additionally, its oxidase-like activity was explored with K _m of 0.21 mM and V _max of 1.74×10 ^− 6 M·s ^− 1 towards 3,3',5,5'-tetramethylbenzidine (TMB). Due to its excellent catalytic activity and nitrite mediated diazotization of oxTMB, a ratiometric colorimetric method for nitrite detection was established and validated with wide linear range (2.0-400.0 µM), low LOD (0.12 µM), high accuracy (recovery of 95.11-102.14%) and fine selectivity. This method was then utilized to analyze nitrite content in sausages and tap water. This study provided a new idea for developing efficient nanozymes, and offered an accurate approach for nitrite determination.