Studies on the Development of Functional Carbon Nanomaterials for Optical Sensing and Photocatalysis

Abstract

Carbon nanomaterials, which exhibit excellent optical properties, are the next generation materials that are attracting attention in the field of applying various optical properties such as biosensing, imaging and photocatalysis. Such carbon nanomaterials have excellent dispersibility in various solvents due to various functional groups generated during synthesis which are useful for surface functionalization. In addition, it has excellent photostability and its optical properties can be varied by controlling the size, composition and atomic control of the carbon nanomaterial. In this thesis, the methodology to control the size and composition of carbon nanomaterials to give new functionalities and investigated the effect of structural changes on optical properties. Based on this research, we have developed carbon nanomaterials that exhibit excellent performance as biosensors and photocatalysts. In Chapter 2, we will develop graphene oxide-amino acid-metal ion (GO-AA-Me) nanostructures showing excellent optical properties and fluorescence properties. GO-AA-Me nanostructures can modulate the binding affinity and redox reaction which induces the change of the fluorescence signal in the presence of the catecholamine neurotransmitters. Finally, the neurotransmitter can be selectively and highly sensitively detected even secreted from living cells. In Chapter 3, fluorescent carbon dots was simply synthesized in a short time by irradiating microwave to the carbon dot precursor, and confirmed the potential as a photocatalyst to promote organic synthesis reaction. Norepinephrine employing bottom-up approach was developed to produce both nitrogen/sulfur co-doped CDs (NS-CDs) and nitrogen-doped CDs (N-CDs) by simply varying solvents. As-prepared NS-CDs and N-CDs included different dopant types and doping constitution and content, which led to changes in photocatalytic activity in aerobic oxidative coupling reactions of various amines. The mechanism responsible for the outstanding photocatalytic activity of NS-CDs in visible light-driven oxidative coupling reactions of amines was also fully investigated. In Chapter 4, fluorescent target selective carbon dots were prepared by using tri-peptide and showed the possibility of selective binding affinity to target protein biomarkers. Peptide carbon dots were prepared by solvothermal reaction in mild condition and exhibited the outstanding optical properties. Tripeptide bearing carbon dots maintained the tripeptide corona on the surface and also had a markedly improved binding affinity to the target protein for myocardial infraction biomarker.