Document Type
Thesis
Date of Award
2026
Degree Name
Master of Science (MS)
Department
Chemistry
First Advisor
Steven X Wu
Abstract
Silicon quantum dots (SiQDs) and carbon quantum dots (CQDs) have been widely studied as fluorescent nanomaterials for sensing applications. In this thesis, we developed two different nanomaterials, SiQDs and CQDs, and investigated their catalytic activities and applied them for the detection of hydrogen peroxide and glucose. In the first project, Co2+-mediated SiQDs were synthesized through a hydrothermal method. The obtained nanoparticles showed obvious peroxidase-like activity toward the oxidation of tetramethylbenzidine (TMB) in the presence of H2O2 under acidic conditions. Moreover, a weak oxidation of TMB was also observed without H2O2, suggesting the existence of oxidase-like activity. To better understand the role of metal ions in these systems, NH2-functionalized SiQDs were prepared without introducing transition metals during synthesis. Fluorescence measurements showed that Fe3+ strongly quenched the emission of NH2-SiQDs, whereas Fe2+ produced only a slight effect. Since Fe2+ can be oxidized to Fe3+ by H2O2, this difference was used to construct a fluorescence sensing platform for H2O2 detection. The fluorescence intensity decreased with increasing H2O2 concentration and exhibited a good linear response within the studied range. In the second project, NH2-functionalized CQDs were synthesized from D-glucose and urea using a microwave-assisted method. Similarly, we found that the fluorescence of this NH2-functionalized CQDs was also quenched by Fe3+. Based on this phenomenon, we constructed a sensor for glucose by introducing glucose oxidase (GOx), once glucose was converted into H2O2 by GOx in the system, the concentration of glucose was detected indirectly through the CQDs/Fe2+/GOx system. The CQDs/Fe2+/GOx sensor showed a linear response toward glucose concentrations from 0 to 0.4 g/L, with a detection limit of 0.0552 g/L. The results indicate that Fe2+/Fe3+-mediated fluorescence quenching can be utilized in both SiQDs and CQDs systems for analyte detection. This work provides a simple approach for the fluorescence sensing of H2O2 and glucose and offers additional information on the interactions between transition metal ions and amino-functionalized quantum dots.
Subject Categories
Chemistry
Keywords
Carbon quantum dots, Glucose, Hydrogen peroxide, Silicon quantum dots
Number of Pages
64
Publisher
University of South Dakota
Recommended Citation
Qin, Kang, "IRON(II)/COBALT(II)-MEDIATED SILICON AND CARBON QUANTUM DOTS FOR NANOZYME ACTIVITY AND FLUORESCENCE SENSING OF HYDROGEN PEROXIDE AND GLUCOSE" (2026). Dissertations and Theses. 438.
https://red.library.usd.edu/diss-thesis/438