Carbon dots as artificial peroxidases for analytical applications

Nanozymes have become attractive in analytical and biomedical fields, mainly because of their low cost, long shelf life, and less environmental sensitivity. Particularly, nanozymes formed from nanomaterials having high surface area and rich active sites are interesting since their activities can be tuned through carefully controlling their size, morphology, and surface properties. This review article focuses on preparation of carbon dots (C dots) possessing peroxidase-like activity and their analytical applications. We highlight the important roles of the oxidation states and surface residues of C dots and their nanocomposites with metal, metal oxides, or metal sulfides playing on determining their specificity and sensitivity toward H₂O₂. Examples of C dot nanozymes (CDzymes) for developing sensitive and selective absorption, fluorescence, and electrochemical sensing systems in the presence of substrates are presented to show their potential in analytical applications. For example, CDzymes couple with glucose oxidase and cholesterol oxidase are specific and sensitive for quantitation of glucose and cholesterol, separately, when using 3,3′,5,5′-tetrame-thylbenzidine as the signal probe. This review article concludes with possible strategies for enhancing and tuning the catalytic activity of CDzymes.