Synthesis And Properties Of Photoluminescent Carbon Dots And Graphene

Carbon nanomaterial is an important part in nanomaterials investigation. Withthe rapid development of carbon nanomaterials, carbon related nanostructures haveinspired extensive interest, especially after the discovery of carbon nanotube,fullerene, fluorescent carbon dots and graphene. Fluorescent carbon dots, with thesizes below20nm, belong to the zero-dimension carbon nanomaterials. With thestable chemical composition, good biocompatibility and low cytotoxicity, carbondots are potential substitution for semiconductor quantum dots to become the newbioprobe. Graphene, with unique physical structure and excellent chemicalperformance, is a flat monolayer of carbon atom tightly packed into a two-dimensionhoneycomb lattice, which attracts extensive attention since discovery at the first timein2004. In this dissertation, we focus on the processing of synthesis fluorescencecarbon dots and graphene. The main contents are as follows:1. With the small size, carbon dots tend to aggregation during the calcination atthe high temperature, which lead to uneven sizes and broaden the perk width at halfheight of photoluminescence emission pattern, thus influence the optical properties.To solve this problem, we present an unprecedented soft-hard template approachtoward photoluminescent CDs with uniform morphologies by using copolymerPluronic P123as soft template and ordered mesoporous silica (OMS) SBA-15ashard template. In this method, organic molecules with different aromatic framework,including1,3,5-trimethylbenzene (TMB), diaminebenzene (DAB), pyrene (PY) andphenanthroline (PHA), can serve as carbon sources for CDs with tunable sizes,compositions and crystalline degrees. We also select different organic precursors tomodify the sizes, structures, compositions and photoluminescent behaviors ofresultant CDs.2. Graphene quantum dots (GQDs), with stable structure and composed of several carbon atoms, exhibit potential application in electronic devices, spin devicesand optoelectronic devices. However, the most research are based on startingmaterials such as graphene oxide, which is typically prepared from oxidation ofcrystalline flake graphite via a series of chemical treatments which often needseveral days and involve a deal of chemical reagents. Generally, the GQDs preparedby these ways have one emission color (blue or green). Here, we offered a newmethod to synthesis GQDs by using fullerence as carbon source and refluxcondensation. GQDs will have different photoluminescense emission spectra throughchanging the temperature and time of relux condensation.3. With the unique physical structure, graphene show great potential applicationin the field of electricity, thermotics, hydrogen storage and optics. At present, themethods to synthesis graphene have a lot of shortages, which limit the application inmicroelectronic devices to a large extent. For example, some approaches requirerigid experiment condition, high temperature and elaborate equipments and strongacid or alkali. Even, the prepared graphene often have many defects. Different fromreported in literatures, we attempt to adopt soft-hard templates and “bottom-up”method to synthesis graphene. Surfactant CTAB regarded as the soft template,TMOS severed as hard template and organic molecular pyrene acted as startingmaterials. Based on this approach, the thickness of graphene can adjust easily bychanging the mass of pyrene.