Synthesis And Applications Of Highly Emissive Solid-state Luminescent Carbondots

Carbon dots?CDs?have attracted widely attention in recent years due to their unique luminescence characteristics,good biocompatibility,low toxicity,and good photostability.These characteristics make them have potential application value in the fields of optoelectronic devices,biological imaging,tumor therapy and other fields.The abundant hydrophilic functional groups such as carboxyl group,hydroxyl group and amine group on the surface of CDs make them easily soluble in water and have strong light-emitting properties in solution,but have no emission in the solid state due to aggregation-induced fluorescence quenching,which greatly inhibits the application of CDs in solid-state lighting and other fields.In this thesis,CDs are taken as the research object,aiming at the problem of aggregation-induced fluorescence quenching existing in most CDs,the design idea is as follows:dispersing CDs in the graphitic carbon nitride?g-C₃N₄?grid to realize solid-state luminescence.The microwave-assisted heating method is used to in-situ synthesize CDs and graphitic carbon nitride,and finally a green emission CDs-based composite phosphor with high photoluminescence quantum yield is obtained,and a highly power efficiency WLED device is realized using this phosphor as color conversion layer.The specific work is as follows:1.Prepare solid-state light-emitting CDs@g-C₃N₄.Using citric acid and urea as procursor materials,the solid-state luminescent CDs@g-C₃N₄ composite phosphor is prepared through a two-step green microwave assisted in situ heating method.The loading of CDs can be adjusted by adjusting the ratio of citric acid and urea.With CDs loading of 1 wt%,CDs@g-C₃N₄ has a photoluminescence quantum efficiency of up to62%.2.The structure,composition,and photophysical properities of CDs@g-C₃N₄ are characterized and studied.3.Explore the luminescence mechanism of solid-state CDs@g-C₃N₄.According to the excitation spectra and emission spectra of CDs and graphitic carbon nitride,and the fluorescence lifetime curves of CDs@g-C₃N₄ with different CDs loadings,it is proved that the energy transfer of CDs@g-C₃N₄ exists and the fluorescence emission is enhanced.4.Explore the potential applications of CDs@g-C₃N₄ in solid-state lighting.The solid-state luminescent CDs@g-C₃N₄ composite was used as the light conversion layer of the InGaN blue-emissive LED chip,and a high efficiency WLED with a light efficiency of 42 lm/W was prepared.