Visual detection of vitamin C in fruits and vegetables using UiO-66 loaded Ce-MnO2 mimetic oxidase

A nanocomposite (UiO-66/Ce-MnO 2 ) was fabricated by combining UiO-66 with cerium-doped manganese dioxide (Ce-MnO 2 ) for colorimetric detecting vitamin C (Vc). Compared with traditional artificial enzymes, the as-synthesized UiO-66/Ce-MnO 2 were simple to prepare and did not require the participation of other active substances. The doping of cerium increased the oxygen vacancies and the UiO-66 as a carrier improved the dispersibility. The formation of superoxide anion (O 2 − ) and the inside Ce 4+ /Ce 3+ and Mn 4+ /Mn 3+ redox couples of UiO-66/Ce-MnO 2 endowed UiO-66/Ce-MnO 2 with a high catalytic capability, which could catalytically oxidize 3, 3′, 5, 5′-tetramethylbenzidine (TMB) into oxidation state TMB (oxTMB) without H 2 O 2 , accompanying with color change and a prominent peak at 652 nm in UV–vis spectra. Based on the inhibitory effects of Vc on catalytic oxidation of TMB, detection of Vc can be achieved, exhibiting a linear relationship in the concentration of 1.13–17.01 μmol L −1 with a low detection limit of 65.82 nmol L −1 . This system can also be detected by smartphone, the linear detection range is 12.47–22.67 μmol L −1 . Vc contents in fruits and vegetables detected by the sensor were in good agreement with the 2, 4-Dinitrophenylhydrazine colorimetry method ( P  > 0.05), indicating a reliable sensor for Vc detection.