Eosin Y as a high-efficient photooxidase mimic for colorimetric detection of sodium azide

The reported fluorescent dye-based artificial light-responsive oxidase mimics are suffering from their low catalytic efficiency. To overcome the limitation, we report the photooxidase-mimicking activity of Eosin Y which can catalyze the oxidation of various chromogenic substrates such as 3,3',5,5'-tetramethylbenzydine (TMB), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 3,3'-diaminobenzidine (DAB), and o-phenylenediamine (OPD) by dissolved oxygen. The photooxidase-like activity of Eosin Y is highly efficient for TMB substrate, and its catalytic efficiency is higher than that of the reported fluorescein (130 fold) and 9-mesityl-10-methylacridinium ion (7.7-fold) mimetic photooxidase. Moreover, the photosensitized Eosin Y-TMB chromogenic system is utilized for colorimetric detection of highly toxic and explosive sodium azide (NaN₃) in a linear range from 5 to 500 μM with a limit of detection of 3.5 μM. The resulting colorimetric assay is selective and applied to determine NaN₃ in real lake water samples.