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Title: The preparation and characterization of graphene-based nanoparticles and carbon nanodots with tunable photoluminescent properties
Author: Geng, Xiangshuai
ISNI:       0000 0004 8501 2368
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2019
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Recently, luminescent carbon-based dots (CDs) have received more and more attention because of their excellent performance, such as tunable photoluminescence (PL), simple synthesis, easy surface functionalization, good biocompatibility, no heavy metal element and various potential applications. In this thesis, two kinds of luminescent CDs were successfully synthesized by employing two different approaches, respectively. At first, a series of graphene oxide quantum dots (GOQDs) were prepared from graphite powder via the chemical oxidation method using different reaction condition and procedures. Various techniques were used to characterize the nanoparticles, such as atomic force microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, Ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy and photoluminescence spectroscopy. The resultant GOQDs had a size distribution from 30 to 120 nm in diameter and abundant oxygen-containing functional groups. The GOQDs showed bright green-yellow fluorescence with a quantum yield (QY) of 0.41%. With the help of further hydrothermal treatment, the QY could be increased to 5.15%. By changing the reaction condition and modifying the experimental procedure, the difference in the structure of all GOQDs was investigated, and their relationship between the structure and PL properties was analyzed. It has been confirmed that some oxygen-containing functional groups like ketone and carboxyl groups are able to influence the PL properties. Cell viability and photodynamic therapeutic effect of the GOQDs were also investigated. Low toxicity and high production of reactive singlet oxygen make the GOQDs have potential in applications in bioimaging and photodynamic therapy. Another series of carbon dots samples were synthesized with three different phenylenediamine monomers via a coupling process with the help of potassium persulfate. The coupling process of the three isomers of phenylenediamine was significantly different, resulting in different structures of carbon nanodots (CNDs). These three kinds of CNDs had a size distribution from 30 to 100 nm in diameter and exhibited blue, green, yellow and orange, even light red fluorescence, which make them promising in various imaging fields.
Supervisor: Hayes, Simon ; Foreman, Joel ; Chen, Biqiong Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available