Colorimetric Determination of Antioxidant Capacity by Peroxidase Mimics Based on Ruthenium Nanoparticles Supported on Carbon Nanosheets

Lattice strain ruthenium nanoparticles uniformly and stably supported on nitrogen-modified carbon nanosheets (RuNPs/NC) were prepared via simple wet-chemical and subsequent pyrolysis method. The nitrogen doped NC could effectively improve their uniform dispersion and lattice compression of RuNPs. Through changing the pyrolysis temperature, the nitrogen content, types and degree of lattice strain of RuNPs could be effectively tuned, which could be used to adjust and control their peroxidase-like activity. The as-prepared RuNPs/NC-900 exhibited highest peroxidase-like activity, and could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue product with the maximum absorption at 652 nm in the presence of H2O2. The steady-state kinetic analysis indicated that the reaction catalyzed by RuNPs/NC followed the Michaelis-Menten kinetic model. Tannic acid (TA), gallic acid (GA) and ascorbic acid (AA) could effectively inhibit the RuNPs/NC-H2O2 -triggered chromogenic reaction of TMB, resulting in color fading and decrease in absorbance. Based on this, a sensitive and accurate system was constructed for detection of TA, GA and AA. The detection limits (3s/S) for TA, GA and AA were 0.014, 0.014 and 0.29 mu mol/L, respectively. This study not only developed a colorimetric sensing method based on RuNPs/NC nanozyme but also offered a new approach for the sensitive detection of antioxidants in food.