Enzyme-like Activity Of Manganese-based Nanomaterials And Their Application

Colorimetric sensing has been widely used in environmental monitoring,clinical diagnosis,biotechnology,public safety and other fields because of its simple operation,low cost and with no need for expensive instruments.Due to its high efficiency,high substrate specificity and high selectivity,natural enzymes can be used in colorimetric sensing.Compared with natural enzyme,nano enzyme has relatively high catalytic activity,low cost,controllable synthesis,adjustable catalytic activity and high stability.In this paper,we studied the properties of enzyme mimics based on MnO₂nanocomposites.In addition,according to the characteristics of the related mimic enzymes,a colorimetric sensor was established to detect the concentration of hydroquinone,Ag⁺and ascorbic acid in eco-environmental analysis fields.The details are as follows:(1)Preparation of Ag@MnO₂ NRs for detection of hydroquinone with the colorimetric methodIn this chapter,rod-shaped MnO₂ was synthesized by hydrothermal method.And Ag@MnO₂ NRs were prepared with the Ag nanoparticles grown on the surface of rod-shaped MnO₂ by different reducing agents.The obtained Ag@MnO₂ NRs were characterized by XRD,SEM,TEM and XPS,respectively.And the catalytic performance,catalytic mechanism and kinetic equation of the Ag@MnO₂ NRs were also investigated.Moreover,Ag@MnO₂ NRs exhibited excellent oxidase-like activity,which could catalyze TMB to produce a blue color solution.Due to the inhibition of hydroquinone on TMB oxidation,a colorimetric sensor with high speed,high sensitivity and strong selectivity was constructed and applied to the detection field.Excellent linear relationship(5-30?M)and a low detection limit of 1.7?M were achieved,and the colorimetric sensor exhibited great anti-interference performance.(2)Preparation of Cu-MnO₂ nanoflowers for detection of Ag⁺with the colorimetric methodIn this chapter,Cu-MnO₂ NFs catalysts were prepared by doped transition metal ions of Cu²⁺with hydrothermal method,which were characterized by XRD,SEM,TEM,XPS and UV-vis.The catalytic activity of Cu-MnO₂ NFs enhanced significantly when the doping concentration of Cu²⁺reached 2%.Cu-MnO₂ NFs could catalyze TMB to produce a blue color solution(ox TMB)in the absence of H₂O₂.Due to the inhibition of GSH on the color reaction of TMB,the color of the system could fade.However,when Ag⁺added into the system,Ag⁺and GSH could form a stable complex,which could weaken the inhibitory effect on ox TMB.With the increase of the concentration of Ag⁺,the color of the system could change blue darker and darker.Based on this mechanism,a colorimetric method for quantitative determination of Ag⁺was established with a linear range from 2 to 26?M and with a detection limit of 700nM.And the colorimetric sensor showed excellent anti-interference ability.(3)Preparation of Ag@Cu-MnO₂ nanoflowers for detection of ascorbic acid with the colorimetric methodIn this chapter,Ag@Cu-MnO₂ nanoflowers with high oxidase activity were prepared by hydrothermal method by Ag nanoparticles grown on the surface of the Cu-MnO₂ nanoflowers.The Ag@Cu-MnO₂nanoflowers were characterized by XRD,SEM,TEM,XPS and UV-vis,and the catalytic performance and kinetic equation were investigated.Based on the inhibitory effect of ascorbic acid on the color reaction of TMB,a colorimetric method for the determination of AA was established.Excellent linear ralationship(5-40?M)and a low detection limit of 1.3?M were achieved,and the colorimetric sensor exhibited great anti-interference performance.