Novel tungsten carbide nanorods: an intrinsic peroxidase mimetic with high activity and stability in aqueous and organic solvents.

Tungsten carbide nanorods (WC NRs) are demonstrated for the first time to possess intrinsic peroxidase-like activity towards typical peroxidase substrates, such as 3, 3', 5, 5'-tetramethylbenzidine (TMB) and ο-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2). The reactions catalyzed by these nanorods follow the Michaelis-Menten kinetics. The excellent catalytic performance of WC NRs could be attributed to their intrinsic catalytic activity to efficiently accelerate the electron-transfer process and facilitate the decomposition of H2O2 to generate more numbers of reactive oxygen species (ROS). Based upon the strong peroxidase-like activity of these WC NRs, a colorimetric sensor for H2O2 is designed, which provides good response towards H2O2 concentration over a range of 2×10(-7)-8×10(-5) M with a detection limit of 60 nM. Moreover, the peroxidase-like activities of WC NRs with TMB as the substrate are investigated in both protic and aprotic organic media, showing different colorimetric reactions from that performed in aqueous solutions. In comparison with the natural horse radish peroxidase, WC NR exhibits excellent robustness of catalytic activity and considerable reusability, thus making it a promising mimic of peroxidase catalysts.