As a new peroxidase mimetics: The synthesis of selenium doped graphitic carbon nitride nanosheets and applications on colorimetric detection of H2O2 and xanthine

Selenium has been successfully doped into graphite phase carbon nitride (g-C 3 N 4 ) by a simple thermal condensation method through calcinating the mixture of dicyandiamide, cyanuric acid and selenium dioxide. The morphology and composition of thus-prepared selenium doped graphite phase carbon nitride (Se-g-C 3 N 4 ) nanosheets were characterized by transmission electron microscopy (TEM), high resolution TEM, X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS). Characterization results revealed that the resultant products have typical ultrathin lamellar structure with the uniform lateral diameter of 20   nm. The amount of Se dopant is ca. 2.1   at% based on the XPS result. For the first time, ultrathin Se-g-C 3 N 4 nanosheets have been demonstrated to possess an intrinsic peroxidase activity by following the Michaelis–Menten kinetics and even have higher affinity to peroxidase substrates TMB and H 2 O 2 in comparison to that of HRP. Se-g-C 3 N 4 nanosheets is conducive to mediating electron transfer and thus to enhancing the catalytic oxidation of the substrate TMB in the presence of H 2 O 2 to produce a blue color change in aqueous solution. More importantly, a sensitive and selective method for xanthine detection was developed using xanthine oxidase and the as-prepared Se-g-C 3 N 4 nanosheets. On the basis of the high catalytic activity of Se-g-C 3 N 4 nanosheets, a rapid, sensitive, and convenient approach was developed for colorimetric detection of xanthine with detection limit 1.6   ×   10 −8   mol   L −1 . Taking the advantages of this, the novel Se-g-C 3 N 4 nanosheets represent a promising candidate as an enzyme mimic and may find a wide range of new applications in diagnostics and biotechnology fields.