Self-cascade colorimetric sensing of profenofos synergistically driven by phosphatase- and laccase-like activities of Ce-MOF nanozymes

To address the need for rapid detection of profenofos (PFF) residues, we developed a self-cascaded colorimetric sensor using the bifunctional nanozyme Ce-UiO-66@His, prepared by doping histidine (His) into Ce-UiO-66. The introduction of His optimized the valence state distribution of cerium and increased the concentration of oxygen vacancies, thereby endowing Ce-UiO-66@His with enhanced phosphatase-like and laccase-like activities. Crucially, these two enzymes can efficiently catalyze in sequence under the same catalytic conditions, thereby achieving an integrated self-cascaded catalytic reaction of PFF. Specifically, the phosphatase-like activity hydrolyzes PFF to generate 4-bromo-2-chlorophenol, which is then oxidized by the laccase-like activity and coupled with 4-aminoantipyrine to form a red quinone-imine dye with strong absorbance. This self-cascaded, dual-recognition system provides exceptional selectivity and high sensitivity for PFF, with a detection limit of 0.71 µg/mL. Furthermore, by integrating smartphones and RGB recognition, a portable photo-colorimetric method was developed that realizes rapid and visual quantification of PFF. This work not only presents a new strategy for rapid monitoring of PFF residues but also offers insights into designing efficient biomimetic self-cascaded sensing systems. Graphical abstract