Carbon Quantum Dots Fabrication And Application

Due to excellent physical and chemical properties,nanomaterials are widely in used in fields of biomedical,catalysis,solar cells and electronic sensor,which is strongly associated with people's daily life.The prosperity of nanotechnology significantly benefits the progress of human society.Carbon quantum dots(CQDs),as a new kind of nano-family member,have recently received tremendous attention because of the novel combination of tunable photoluminescence,excellent photo-stability,well biocompatibility,and chemical inertness.The emerge of carbon quantum dots brings favourable opportunity and promising prospect in broadening the application of nanoparticles.The first chapter,the paper will firstly and systematically introduce the origin,basic definition and recent research progress of nanoparticles.Since the door of nano-research opened by great Faraday in the mid-nineteenth century,unique quantum property of nanoparticles is rapidly revealed and confirmed by scientists.The material property evolution caused by quantum property has raised tremendous research attention and been widely applied in numerous fields such as biomedicine,electronic and solar cell.Since the research direction is based on CQDs fabrication and its biological application,the main context of this chapter is focused on preparation methods and biomedical research progress.The second chapter describes preparing of an ultrastable,highly luminescent graphene quantum dots(GQDs)by pyrolysis of folic acid and trihydroxyamino methane.The new GQDs present step changes compared to common folic acid through an?6250times increase in water solubility(to?10 mg m L^-1),more than 150 times in QYs(up to?77%),while maintaining luminescence stability up to 98%when subjected to UV,visible light,and heating over 360 min.The research also reveals that the prepared GQDs successfully inherit the cancer targeting ability of folic acid and can selectively binding to divers cancer cells over expressing with folate receptors.It is shown that the suppression of nonradiative transitions by amino groups pyrolyzed from pterin plays a key role in determining the high QYs.Inherent stability of graphene nucleus,surface molecular structure of oxhydryl(OH^·),and relatively low reactive oxygen species(ROS)level collectively lead to high stability against photobleaching.Functional groups that are likely responsible for the selective targeting of cancer cells with different levels of folate receptor expression on the surface are identified.The third chapter presents the preparation of acid sensitive carbon dots(AS-CDs)respectively featuring yellow(550 nm)and red(620 and 630 nm)fluorescence emission at p H=7 and p H=1.Further characterization demonstrates that both yellow and red fluorescence of prepared CDs can be induced under one-photon and near-infrared two-photon excitation.The analysis results revealed that surface functional groups of aromatic amino and phenazine structure may responsible for the one/two-photon yellow fluorescence emission at p H=7.When encountered with p H=1condition,the protonation of amino groups narrows down the band gap of CQDs and further causes red shift of fluorescence emission into red light region.Additionally,the research demonstrates the prepared AS-CDs can be applied in light emitting diodes fabrication and Escherichia coli confocal imaging.The fourth chapter shows the environmentally friendly synthesis of carbon nanoprticles(C-NPs)by microplasma processing folic acid(FA)in saturated sodium bicarbonate solution.The research reveals that with plasma processing,carbon atoms of FA are involved in sp² hybridization and amine(-NH₂),N-H and-COOH functional groups are converted into ROOC-NH-COOR group.As a consequence,the electron donating ability of aromatic ring is enhanced,lead to enhancement in fluorescence of FA C-NPs.Finally,the promising application of FA C-NPs in bioimaging is also demonstrated by fluorescence labeling of MCF-7 cancer cells.The fifth chapter presents the summery of the research work mentioned in chapter2?4,and then,then outlooks the further research direction based on the findings and drawbacks in this paper.