Preparation Of Carbon Dots/gold And Sodium Composites And Their Application

Carbon dots(CDs),graphene quantum dots(GQDs),and noble metal nanoparticles have exhibited excellent properties in many fields such as photo/electro-catalysis,biological imaging,optoelectronic devices and disease diagnosis owing to the high catalytic performance,good biocompatibility,excellent light stability,well photothermal effect,etc.This thesis is aiming at combining the two materials together with chemical bands to take full use of their respective advantages and exploring new properties and applications.Herein,a green and rapid method for GQDs/Au nanocomposites preparation was studied and the reaction mechanism was explored for the first time.It was thought that there were three roles of GQDs in the reaction:reducing agent,stabilizer and catalyst.A set of methods were provided in the preparation of CDs/nobel metal nanocomposites and they showed wide applicability.Visual analysis of caffeine has been designed by combination of the merits of gold nanoparticles(Au NPs)and CDs,the localized surface plasmon resonance(LSPR)of Au NPs and abundant functional groups of CDs.The preparation of non-aromatic carbon dots salts by heating natural material rutin in concentrated alkaline solution solved the problem of aggregation-induced quenching(AIQ)of CDs.Therefore,they were applied in anti-blue light film preparation without any modification which was the first report about CDs fabricated anti-blue light film.1.To explore how graphene quantum dots(GQDs)worked in Au nano-particles(Au NPs)preparation,three kinds of GQDs(GQDs-2(GQDs heated for 2 h),GQDs-12,Hydroxyl-poor graphene quantum dots(Hp GQDs))and sodium citrate(Na₃Ct)were explored in the reaction with chloroauric acid(HAu Cl₄),respectively.Results showed that GQDs played three roles:the reducing regents,stabilizers and catalysts.In detail,GQDs were ligands(stabilizers),hydroxyl groups were reductants and carbon cores were catalysts.For further,sp²-hybrid carbon decorated on carbon core was thought dominated the catalytic process.The influence of solution p H and GQDs concentration(GQDs-2were employed in the study)were studied in the reaction.The results indicated that protons would weaken the catalysis of carbon core and high concentration of GQDs would increase the proportion of small-sized particles in gold nano-particles(Au NPs)while the influence of big ones were limited.Most importantly,the theory showed broad applicability and a set of methods for preparing GQDs/noble metal nano-composites were provided here.2.Using the reaction mechanism above,a mixture of GQDs-2.5 and HAu Cl₄ was heated for 15 min to obtain graphene quantum dots functionalized nano-gold(GQDs-2.5/Au)composites.A green and rapid mrthod for CDs/Au preparation was provided.Their morphology were characterized by high-resolution transmission electron microscope(Hr TEM),energy dispersive spectrometer(EDS)and X-ray diffraction(XRD).Results showed that GQDs-2.5 combined well with Au NPs and formed core(Au NPs)-shell(GQDs-2.5)structure.The GQDs-2.5/Au solution was used for visual analysis of caffeine which was the first report about GQDs/Au composites used in visual analysis.The colour of GQDs-2.5/Au would change from wine red to blue with the adding of caffeine,because Au NPs functionalized by GQDs-2.5 would aggregate with caffeine through hydrogen bonds.In detail,the wine red faded in the presence of caffeine with the caffeine concentration ranging from 3.2 x10^-6–8.0 x 10^-5 M,and the solution changed from red to blue with the caffeine concentration over 2.0 x 10^-4 M.For accurate determination,the UV-vis absorption peaks of the solution showed good linearity to the concentration of caffeine ranging from 3.2 x 10^-6–4.0 x 10^-4 M.The methods provided showed the merits of fast response speed,cheap reagents,and no restrictions of working environment.3.Generally,natural materials prepared CDs by hydrothermal method faced problems of low quantum yield(QYs)and short photoluminescence(PL)wavelengths(most PL of CDs are blue).Herein,Na⁺on the surface of CDs were prepared by hydrothermally heating the natural material rutin in 1 M Na OH solution.CDs could be well dispersed in methanol and showed yellow PL with the QYs as high as 21.8%.To solve the AIQ of CDs soloids,non-aromatic CDs were prepared to avoid the quench caused by the?-?*stacking of aromatic carbon.As a result,the prepared CDs still showed strong PL in solid state.Dispersing CDs solids in epoxy resin,a red light LED film was prepared and characterized.CDs were dispersed in PMMA and epoxy resin to fabricate anti-blue light films.Results showed that the conversion of blue light was related to CDs concentration.The two kinds of films were characterized and compared with the commercial films in spectral power distribution,light transmittance,blue-light peaks,chromaticity coordinate(CIE),color temperature(CCT)and color rendering index(CRI).