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 (NaN 3 ) 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 NaN 3 in real lake water samples.