Fabrication And Multifunctional Analytical Applications Of Metal Doped Carbon Dots Nanozymes

As a new class of nanozymes,carbon dots（CDs）have been used in biosensing,disease diagnosis and treatment,environmental monitoring,photocatalysis and other fields because of their simple preparation process,high stability,easy functionalization and high catalytic activity.Doping metal ions in CDs can change the charge density and electron transfer form of CDs,increase the catalytic active site,and is an effective strategy for the development of CDs nanozymes.Therefore,two metal-doped CDs nanozymes with excellent performance were designed and prepared,their catalytic properties were analyzed,applied to drug analysis and detection,and their application potential as chemodynamic therapeutic（CDT）agents in anti-tumor therapy was explored.The main contents include:Chapter 1:The research and application of CDs nanozymes were reviewed.Firstly,the types of nanozymes and the materials for synthesizing nanozymes were summarized,then CDs nanozymes and their doping were emphasized.Secondly,the applications of CDs nanozymes in sensing,catalysis,antibacterial and cancer treatment were summarized in detail.Finally,the background,research content and innovation points of this paper were briefly summarized.Chapter 2:Cobalt-doped carbon dots（Co-CDs）nanozyme was prepared by one-step pyrolysis with vitamin B12（VB12）and citric acid as precursors.The cobalt ion in the precursor VB12 acted as an active center for nanozymes,imparting excellent peroxidase（POD）-like activity to Co-CDs.Co-CDs exhibited high affinity for H₂O₂ and can catalyze H₂O₂ to produce three reactive oxygen species（ROS）,namely hydroxyl radical（·OH）,superoxide anion（·O₂^-）and singlet oxygen（¹O₂）.Therefore,a sensitive colorimetric sensor for detecting glucose through a cascade reaction was developed by combining Co-CDs with glucose oxidase（GOx）.The response to glucose ranged from0.500μM to 200μM with a limit of detection（LOD）of 0.145μM（S/N=3）.This biosensor enabled accurate detection of glucose in human serum samples.At the same time,due to their excellent catalytic activity,Co-CDs can be used as a CDT reagent.Cytotoxicity and confocal cell imaging experiments have proved that Co-CDs can catalyze the overexpression of H₂O₂ in cancer cells to produce highly toxic ROS,thereby inducing cancer cell death and achieving the purpose of killing cancer cells.Chapter 3:Molybdenum-doped carbon dots（Mo-CDs）nanozyme was prepared by one-step hydrothermal method with ammonium molybdate and ascorbic acid as precursors.Due to unique structural characteristics,Mo-CDs showed excellent POD-like activity and can catalyze the oxidation of H₂O₂ to ¹O₂ through Russell mechanism.Based on the fact that the ¹O₂ produced by Mo-CDs nanozyme can react with ampicillin（AMP）,a new colorimetric detection method for AMP was constructed.Response range to AMP was 0.0500μg/m L to 100μg/m L with LOD as low as 12 ng/m L（S/N=3）.Combining colorimetric test paper with smartphone,a smartphone-assisted sensing platform was developed,which realized convenient and rapid detection of AMP in water samples.At the same time,Mo-CDs can also be used as CDT reagents to catalyze overexpressed H₂O₂ in cancer cells into highly toxic ¹O₂,achieving the purpose of targeted killing tumor cells.