Heavy Metal Ion Sensing Based On The Modulation Of Noble Metal Nanozymes Activity

Due to the excellent catalytic activity,easily regulated enzyme-like properties and high stability,noble metal nanozymes have potential application in many fields,such as disease diagnosis and treatment,biomolecular sensing,environmental pollutant detection and so on.For instance,with the help of heavy metal ions on noble metal nanozymes surface chemical properties regulation and the resultant inhibition or enhancement of nanozymes activity,a series of heavy metal ion sensing methods with the advantages of rapid reaction,high selectivity,low detection limit have been developed.It is true that these methods exhibit more merits such as simple detection process,short analysis period,anti-interference ability and other outstanding advantages over the traditional electrochemical,atomic absorption spectrum,inductive coupling plasma luminescence mass spectrometry detection strategies.Based on this,this paper focuses on the surface chemical effect of noble metal nanozymes and the regulation of their enzyme-like activity,by using the oxidation product TMBox of organic chromogenic substrate 3,3’,5,5’-tetramethylbenzenzidine（TMB）as colorimetric and photothermal analytical signal,constructing colorimetric and photothermal dual-mode sensing methods for Ag⁺and Ce³⁺on the basis of noble metal nanozymes.This paper includes the following four parts.Chapter 1.Introducing the main types,catalytic properties and the regulation strategies of noble metal nanozymes,and summarizing the application prospects and challenges of these nanozymes in the field of analytical sensing.Chapter 2.Polyvinylpyrrolidine-coated platinum nanocube（PVP-Pt NCs）nanozymes were successfully prepared by solvent thermal method.The regulatory mechanism of Ag⁺for PVP-Pt NCs nanozymes enzyme-like activity was studied.It was found that PVP-Pt NCs nanozymes has high peroxidase-like（POD）activity,and can efficiently catalyze TMB to produce blue colored oxidation product of TMBox in acidic media.Because TMBox has good photothermal conversion performance in the near-infrared region,and then can produce both color and temperature signal response.When Ag⁺was present in the system,it could specifically bind to the surface of PVP-Pt NCs and resultantly inhibiting the POD activity of PVP-Pt NCs nanozymes,resulting in a significant weakening of both the color signal and the temperature signal of the system.Based on this,a dual-mode colorimetric and photothermal sensing method for Ag⁺was successfully constructed.The experimental results show that the limits of detection of colorimetric and photothermal sensing Ag⁺was 745.95 n M and 31.18 n M（S/N=3）,respectively.It indicates that the developed method also could be used for the effective detection of Ag⁺in the Yellow River water and tap water sample.Chapter 3.Bare gold nanoparticles（Au NPs）were successfully synthesized by using one-step reduction method.The modulation mechanism of Ce³⁺for Au NPs nanozymes activity was studied.It was found that Au NPs itself has low POD activity and weak catalytic ability for TMB oxidation in an acidic environment.When Ce³⁺was introduced into the system,which could rapidly bind to the Au NPs surface through an electrostatic attraction effect.Then the strong redox cycle capacity of Ce³⁺/Ce⁴⁺further accelerates the electron transport of Au NPs surface,thus enhancing the POD activity of Au NPs nanozymes.Based on this,a colorimetric and photothermal two-mode sensing method for Ce³⁺with an?open?nanozymes activity function was successfully constructed.The experimental results show that the detection limit（LOD）of colorimetric and photothermal detection of Ce³⁺is 0.2865μM and 2.2466μM（S/N=3）,respectively.It also indicates and the sensing method can be used for Ce³⁺analysis in the Yellow River water and tap water samples.Chapter 4.Summarizing the regulation and operate mechanism of noble metal nanozymes（PVP-Pt NCs and Au NPs）and its application in colorimetric and photothermal sensing.And discusseing the potential development and application prospect of noble metal nanozymes in the field of analytical fields.