A sensitive colorimetric sensor for glutathione on the basis of the oxidase-like activity of polyoxometalate-based helical compound and its nanocomposite with SWNT-COOH

Here, a new Keggin-type POMs based supramolecular compound with the 4-fold meso-helixes, [PW12O40]4MI·3H2O (PWMI) (MI = 2-methylimizole), was successfully synthesized and characterized by routine method. As one new kind of nanozymes, compound PWMI was found to possess oxidase-like activity for the first time, namely, it can effectively catalyze the oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB). With functionalized single-walled carbon nanotubes (SWNTs-COOH) introduced into PWMI, the oxidase-like activity of nanocomposite PWMI/SWNTs-COOH was further enhanced. More importantly, the PWMI/SWNTs-COOH-based colorimetric sensor exhibits the fastest response time (30 s) among all reported nanozymes for glutathione (GSH) detection to date, to the best our knowledges, and the limit of detection (LOD) as low as 0.017 μM, and the linear range as wide as 5 to 150 μM.