Oxidized 3,3',5,5'-tetramethylbenzidine nanobelts enhance colorimetric sensing of HO.

Herein, oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB) nanobelts were developed to enhance the colorimetric and paper-based sensing of HO. It was found that the minor component of Fe in NaSO reagent could catalyze the oxidization of TMB by HO into positively charged oxTMB, which was further assembled into dark blue oxTMB nanobelts via electrostatic interaction with SO. The extinction originating from the absorption and scattering of oxTMB nanobelts was utilized to quantitatively detect HO with a wide linear detection range (1.0-300 μM) and a low limit of detection (0.48 μM). In addition, no coffee-ring effect was observed in the test zone of the paper-based colorimetric array, which was beneficial to judge the color by naked eye. Finally, the colorimetric method was applied to detect HO in contact lens care solution. This work not only proposed a new colorimetric sensing platform for HO, but also highlighted the minor component in the reagent might influence the experimental result.