The Preparation Of Metal Doped Nanocomposites And Their Application In Colorimetric Sensing

Due to the high surface binding energy,van der Waals forces and intrinsic magnetic interactions,nanometals tend to aggregate,resulting in decreasing peroxide mimetic enzyme activity of nanomaterials.In order to solve this problem,we provided a research idea of preparing metal-doped nanocomposites to enhance the peroxidase-like activity of nanomaterials from the strong synergistic effect between metal and the support.The main contents are as follows:(1)Gold-doped cobalt oxide and cerium oxide nanocomposites(Au/Co3O4-CeOx NCs),iron-doped copper hydroxystannate(Fe/CuSn(OH)6)together with platinum-doped cobalt hydroxystannate nanocube(Pt/CoSn(OH)6 NC)were successfully prepared by a simple two-step in-situ reductive coprecipitation method.The nanocomposites were characterized by high-angle annular dark field image scanning transmission electron microscopy(HADDF-STEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and other physiochemical techniques.The results of the peroxidase assay indicated that all of three materials possessed peroxidase-like activity.The specific performance is as follows:nanomaterials could rapidly catalyze the oxidation of colorless 3,3’,5,5’-tetramethylbenzidine(TMB)by H2O2 to blue oxidized TMB(oxTMB).The obvious color change could be observed in less than 30 s.(2)To verify the catalytic mechanism of three nanocomposites,terephthalic acid(TA)was chosen as a fluorescent probe to capture hydroxyl radicals generated during the catalytic reaction and produced a fluorescent 2-hydroxy terephthalic acid.The experimental results indicated that all of reaction mechanisms were attributed to the hydroxyl radicals mechanism.(3)Based on the superior peroxidase-like activity of the three materials,we constructed colorimetric sensors for the detection of H2O2 and dopamine,respectively.The detection results are described as follows:for H2O2 detection,Au/Co3O4-CeOx system had a limit detection of 5.29 μM with a linear range from 10 to 100 μM,Fe/CuSn(OH)6 system had a limit detection of 9.49 μM with a linear range from 30 to 1000 μM and Pt/CoSn(OH)6 system had a limit detection of 4.42 μM with a linear range from 5 to 200 μM,respectively.Besides,the Pt/CoSn(OH)6 system had a detection limit of 0.76 μM for dopamine and a linear range of 5-60μM.The results suggest that our proposed colorimetric sensors did detect hydrogen peroxide and dopamine with high sensitivity and good linear response.