| Carbon dots(CDs),as novel zero-dimensional materials,have attracted considerable attention in various fields and have great potential in the future due to their low cost,non-toxic and unique photoelectric properties.In particular,carbon dots have been rapidly developed in the fields of bio-imaging and light-emitting diodes(LEDs).In addition,due to their excellent conductivity and large specific surface area,carbon dots have been gradually used in supercapacitors and batteries.However,the preparation of carbon dots for direct white emission with high quality and long wavelength emission remains a challenge.Moreover,the carbon dots with phosphorus doping are barely reported in the application of lithium-sulfur battery.In this paper,white light emitting carbon dots with high photoluminescence quantum yield(PLQY)were prepared by hydrothermal method,which were investigated for their fluorescence properties and used for solid-state fluorescence materials;carbon dots with narrow emission band and red emission were synthesized by means of acidification,which were investigated for their fluorescence properties and applied in biological imaging;phosphorus-doped carbon dots and graphene aerogel composites were prepared by one-step hydrothermal method and investigated for their potential in lithium-sulfur battery.Related research contents and experimental results are as follows:1.Nitrogen-doped white-light-emitting graphene quantum dots(W-GQDs)were prepared by solvothermal method with 1,5-diaminophenone(1,5-DAN)and tartaric acid(TA)as precursors,which exhibited double fluorescent emission bands concentrated at 413 nm(blue emission)and 558 nm(yellow emission)and excitation-independent emission.In addition,W-GQDs showed good optical stability under 365 nm UV and sunlight,while showed good thermal stability at different temperatures with maximum fluorescence intensity at 25 ℃.The absolute PLQY of the synthesized W-GQDs was measured to be 28.68%.The W-GQDs/polyvinyl alcohol(W-GQDs/PVA)and W-GQDs/epoxy resin(W-GQDs/EP)composites with white fluorescence were obtained by dispersing W-GQDs into polyvinyl alcohol and epoxy resin,which showed high PLQY of9.32% and 11.12%,respectively.In addition,the color rendering index(CRI)of W-GQDs/EP composites was measured up to 80.2,which shows good color rendering as light source.According to the above results,W-GQDs have great potential in the field of white light-emitting diodes(WLED).2.Nitrogen-doped yellow light-emitting graphene quantum dots with wide full-width at half-maximum(FWHM)of 89 nm and emission wavelength at 567 nm were prepared by hydrothermal method using o-phenylenediamine(OPD)as the single precursor.The protonized graphene quantum dots(P-GQDs)with ultra-narrow emission band(FWHM of 33 nm)at 628 nm were obtained after the treatment of acidic condition.The mechanism of emission peak with red-shift caused by acidification of GQDs were investigated by FTIR spectrum and the effects for fluorescent property of GQDs were researched at different pH.Finally,P-GQDs were successfully used for bioimaging of He La cells due to their excellent biocompatibility and excellent fluorescent performance.3.Phosphorus doped carbon nanodots/graphene aerogel materials(P-CNDs/GA)were prepared by one-step hydrothermal process,using biomass-deriving phytic acid(PA)and graphene oxide(GO)as raw materials.The formation of P-CNDs/GA was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy,and the ratio of phosphorus doping was measured up to 2.12%.In addition,compared with graphene aerogel(GA),the adsorption ability of P-CNDs/GA to polysulfide was verified to be much better,which demonstrates its potential in lithium-sulfur battery. |
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