Next generation multi-color carbon dots: A comprehensive understanding of their photophysical properties and subsequent use for biomedical applications

As an upcoming and emerging class of carbon-based nanomaterials, carbon dots (CDs) have garnered widespread attention amongst researchers over the past decade owing to their strong optical properties, water solubility, excellent biocompatibility, and easy synthetic procedures. These remarkable properties of CDs have resulted in utilizing them for a wide variety of biomedical application ranging from bioimaging, cell labeling, drug delivery, and sensors. For synthesizing these CDs, multitude of different raw materials and synthetic approaches have been reported. The reported raw materials utilized range from natural products such as glucose, citric acid, etc. to laboratory-synthesized chemical. Furthermore, the synthetic approaches used vary from laser ablation, hydrothermal reactions, microwave treatment, pyrolysis, etc. However, in most of those studies, the photoluminescence (PL) of CDs is broad, with emission raging between blue and green region, and show excitation-dependent emission characteristics indicating that these CDs are produced in complex mixtures. To separate this, a variety of separation techniques including high performance liquid chromatography (HPLC), polyacrylamide gel electrophoresis (PAGE) were the yield is very less. Furthermore, the quantum yield (QY) of these CDs are low with no clear understanding of their PL properties limit their applications in biological applications such as in vivo imaging. In this thesis, I attempted to perform a comprehensive understanding of the photophysical properties of CDs so that they could be tuned to produce brighter, high QY emitting which could be eventually used in wide variety of biological applications including in vivo animal imaging. Towards this goal, I first performed an in-depth understanding of the PL mechanisms of CDs both at ensemble level as well as single-particle level and found it’s PL to be correlated with their surface defects as well as abundance of oxygen-rich groups on the nanoscale surface of CDs. Subsequently, extrapolating this information, I fabricated CDs with high quantum yield and mutli-color CDs so that they could be used for multiscale in-vivo imaging. Additionally, I synthesized CDs having switchable PL which can switch off-switch on their PL by an external trigger such as surface passivation, UV light or hypoxia. I also attempted to study its interaction with enzymes: studying their biodegradation patterns in presence of human digestive enzymes, proteins: examining the protein corona formation with varying surface chemistry using an on-chip electrical monitoring setup, and oligonucleotides: utilizing them to deliver intracellular cargo and monitoring of biological events. Overall, I believe that this thesis provides a comprehensive understanding , a of the photophysical phenomenon of these CDs so that it would allow any researchers to fabricate them in an application-specific manner as well as knowing the likely mechanism of their complete degradation in living systems could pave a faster route for their applications in a clinically relevant setup.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Bioengineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Srivastava, Indrajit

Contributors dc:contributor

• Pan, Dipanjan
• Nie, Shuming
• Irudayaraj, Joseph
• Zhang, Kai

• Carbon dots
• Fluorescence origins
• Surface defects
• Multi-color
• Switchable Fluorescence
• Bioimaging
• Nano-bio interactions
• Cell labeling
• Drug-delivery
• Biosensing

Statement dc:rights

• Copyright 2020 Indrajit Srivastava

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108282

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108282