Double-shell hollow FeCoOx nanozyme-catalyzed colorimetric quantification and discrimination of dihydroxybenzene isomers

Due to the high perniciousness of dihydroxybenzene isomers toward environment and human health, it is imperative to develop simple and rapid strategies for detecting/distinguishing dihydroxybenzene isomers. However, most of the traditional approaches can only respond to single component of dihydroxybenzene isomers, which limits their application in the assay of complex samples. Herein, we develop a colorimetric sensing array based on the peroxidase-like activity of double-shell hollow FeCoOx nanozyme. Since different phenolic substances showed distinct kinetics during the catalytic reaction with the participation of FeCoOx, three different kinds of dihydroxybenzene isomers could be identified by principal component analysis. Moreover, various combinations of mixed dihydroxybenzene isomers with different concentrations can also be completely distinguished within 30min in tap water and environmental water. The method showed a good linear response to catechol, resorcinol, and hydroquinone in the range of 1.5 to 100 µM, 5 to 100 µM, and 1 to 100 µM, respectively, with corresponding detection limit of 1.37 µM, 2.91 μM, and 0.824 μM. Besides, we have constructed a smartphone-based portable platform for analyzing various combinations of mixed dihydroxybenzene in actual water. This work provides a new idea for distinguishing phenolic substances with similar structures, and is promising to identify and monitor phenolic pollutants in industrial wastewater.