Colorimetric And Photothermal Sensing Of Metal Ions Based On Prussian Blue Nanozyme

Point-of-care testing（POCT）methods based on nanozymes is a promising rapid detection and analysis method with simple,fast,portable and economical advantages,and have been widely used in medical diagnosis,environmental monitoring and food safety.Due to the presence Fe³⁺and Fe²⁺on the surface of Prussian blue nanoparticles（PBNPs）,which possess good peroxidase-like（POD-like）activity and therefore show great potential in POCT.However,the catalytic activity and stability are easily affected by hydroxyl radical（·OH）produced by hydrogen peroxide（H₂O₂）.Therefore,it is necessary to modify it to further improve the catalytic activity and stability to expand its analytical applications.Fe₃O₄nanoparticles have been intensively studied due to their excellent magnetic properties and enzyme-like activity.Based on this,a magnetic Prussian blue（MPBNs）nanozyme with a core-shell structure was prepared by using Fe₃O₄as nuclear and PBNPs as shell.The excellent POD-like activity of MPBNs nanozymes could further enable the production of color and temperature signal by catalyzing the substrate 3,3′,5,5′-tetramethylbenzidine（TMB）,and finally realizing point of care testing of Cr（Ⅵ）and Ag⁺.This paper is divided into the following four parts.Chapter 1.Introducing the concept and development of POCT,and summarizes the synthesis strategy,development and enzyme-like activity of PBNPs nanozyme;and summarizes the practical POCT application of PBNPs nanozyme in protein,molecule,nucleic acid and ions.Chapter 2.The magnetic Prussian blue（MPBNs）nanozyme with an excellent core-shell structure and peroxidase-like（POD）activity under acidic condition is prepared.It was found that MPBNs nanozyme can efficiently catalyze H₂O₂to generate·OH and which can further oxidize the colorless substrate TMB to produce the blue colored ox TMB.8-Hydroxyquinoline（8-HQ）can reduce blue colored ox TMB to colorless TMB.However,when the target Cr（Ⅵ）was introduced,the reduced ox TMB in the system was decreased due to the strong bidentate chelation between Cr（Ⅵ）and 8-HQ.Based on this,a simple and efficient colorimetric sensing method of Cr（Ⅵ）in water samples was successfully constructed.The detection limit was 0.1517μM（3δ/k）,which is lower than the Cr（Ⅵ）concentration of drinking water standard stipulated by the Ministry of Ecology and Environment of China（0.96μM）.It also can be used to point of care testing Cr（Ⅵ）in Yellow River water and tap water samples.Chapter 3.Through the study of magnetic MPBNs nanozyme,we found that Ag⁺may specifically react with Fe₄[Fe（CN）₆]₃ on the surface of MPBNs to produce Ag₄[Fe（CN）₆].It subsequently decreases the POD-like activity and intrinsic photothermal properties of MPBNs,and finally eventually inhibiting the color and temperature signal responses through the oxidation process of the substrate TMB.Based on this,a simple,and efficient colorimetric and photothermal detection method of Ag⁺in water samples was successfully constructed.The experimental results show that the limits of detection of colorimetric and photothermal sensing was 4.086μM（S/N=3）and 3.371μM（S/N=3）,respectively.The recovery experiments of colori-metric and photothermal methods was 95.08-102.3%and 103.5-104.9%,respectively,demonstrating the accuracy and reliability of the proposed nanozymes-based method.Chapter 4.Summarizing the advantages and disadvantages of colorimetric and photothermal sensing metal ions based on MPBNs,and discusseing how to further improve the analytical performance and expand their application,as well as the future development direction and application prospect.