Author ORCID Identifier
Document Type
Thesis
Date of Award
2024
Degree Name
Master of Science (MS)
Department
Chemistry
First Advisor
Steven Wu
Abstract
Phosphorescent materials are essential in bioimaging, anti-counterfeiting, and other applications due to their prolonged light emission. However, current phosphorescent materials face challenges such as complex synthesis, high costs, and instability. Carbon dots (CDs), with size less than 10 nm, are a promising alternative due to their biocompatibility, tunable optical properties, and simple synthesis. This thesis explores the synthesis of CDs using ethylenediamine (EDA) and phosphoric acid via a microwave-assisted method, followed by silica encapsulation using a modified Stöber process to form CDs@SiO2, aiming to enhance their stability and optical properties. Optical characterization showed a slight blue shift in the excitation wavelength of CDs@SiO2, with emission wavelengths remaining nearly identical to uncoated CDs. Neutral CDs@SiO2 samples were chosen for further experiments due to their practical suitability and comparable performance to acidic samples. The phosphorescence time of neutral CDs@SiO2 solution was up to 10 s. The presence of a peak at 1074 cm⁻¹ in the IR spectra confirmed successful silica coating, supported by zeta potential measurements indicating enhanced colloidal stability. Additionally, doping CDs@SiO2 with various dyes using a modified Stöber process resulted in dye-doped particles retaining fluorescence and phosphorescence properties while exhibiting additional fluorescence peaks. Dynamic light scattering (DLS) and zeta potential measurements indicated changes in size and surface charge, suggesting successful doping and potential for Förster Resonance Energy Transfer (FRET). In conclusion, this study demonstrates the successful synthesis and silica coating of CDs, leading to improved stability and distinct optical properties. These advancements highlight the potential applications of these nanomaterials in anti-counterfeiting and biosensing. Future work will focus on shifting phosphorescence from green to the near-infrared (NIR) region using FRET mechanisms, enhancing their applicability in advanced technological and biomedical fields.
Subject Categories
Materials Chemistry
Keywords
Carbon Dots, Microwave-Assisted, Phosphorescence, Silica Nanoparticles, Stöber Method
Number of Pages
72
Publisher
University of South Dakota
Recommended Citation
Liu, Weichao, "PHOSPHORESCENT CARBON DOTS DOPED SILICA NANOMATERIALS VIA MICROWAVE-ASSISTED AND MODIFIED STÖBER METHODS FOR ANTI-COUNTERFEITING AND BIOSENSING" (2024). Dissertations and Theses. 229.
https://red.library.usd.edu/diss-thesis/229