Synthesis Of Fluorescent Carbon Nanomaterials And The Research Of Their Properties

Fluorescent carbon nanomaterials (FCNPs), as a new type of fluorescent material, have shown superior properties in both optical and bioanalytical applications compared with conventional fluorescent materials. For example, the application of organic dyes was limited due to their poor photochemical stability and the interference of photo-dissociation product on organisms.As for traditional quantum dots, although they have been well studied and used widely, there are still issues of potential biological toxicity and light blinking associated with their usage. Fortunately, the development of FCNPs can overcome aforementioned problems to a certain extent. Generally, FCNPs offer four obvious advantages:(1) The excitation spectrum is wide extending from the UV region to the visible region;(2) The fluorescence is so stable that after being excited for several continuous hours, the fluorescence intensity remains unchanged;(3) The particle size is only several nanometers therefore they have a strong penetration ability into cells;(4) Excellent biocompatibility and low toxicity enable them to replace quantum dots to become the most promising fluorescent marker in the biomedical field. So far, FCNPs have been applied in bioimaging, drug delivery, environment detection, photocatalysis, energy conversion, optoelectronics, and sensing. Synthesis methods for FCNPs include laser ablation, template, electrochemical, hydrothermal, concentrated acid oxidation and organic substance carbonization and so on. Among them, hydrothermal methods are favored for relatively good controllability, ease of operation and mild reaction conditions. By adjusting the reaction temperature, time, material proportion and other relevant parameters, the fluorescent nanoparticles could be manufactured with tunable sizes, compositions and surface structure, which allows for the modification of optical properties. Therefore, hydrothermal methods are regarded as important means in preparing fluorescent nanomaterials. In this dissertation, we focus on hydrothermal synthesis of carbon dots (CDs) and study of their optical properties. The main contents are as follows:(1) A scalable synthesis of water-dispersible fluorescent carbon nanodots based on the simple hydrothermal method of kitchen wastes (grape peel as an instance) was reported. We discuss the feasibility of synthesis from kitchen wastes both experimentally and theoretically. The experimental results show that, the as-prepared nanodots shows excellent resistance to salt and have high selectivity for Hg2+ions based on fluorescence quenching which is due to the complexes of nanodots and metal ions.(2) Water-dispersible, ultralong pH-stable and highly luminescent graphite-like poly(L-proline) dots (GPDs) have been sythesized using biomolecule (L-proline) as the monomer. The obtained dots were applied to the cytoplasm staining of CBRH7919cells, showing well-biocompatibility, and could act as an excellent bioimaging reagent.(3) N-doped carbon dots (NCDs) from hybrid carbon source (glucose and glycine) which exhibit a stronger fluorescence than the carbon dots from single source (glucose or glycine) are obtained by one-pot hydrothermal treatment. The experimental results show that the NCDs can be used as an effective fluorescent probe for the detection of iron ions with good selectivity and sensitivity in an aqueous solution.