Preparation And Application Of High Fluorescent Carbon Dots With Aromatic Hydrocarbon

Carbon dots?CDs?are a new type of fluorescent nanomaterials,which have attracted much attention due to their excellent properties including water solubility,low toxicity,biocompatibility,small size,fluorescence and easy modification.At present,the main problems facing the prepared CDs are:?1?Short emission wavelength and low quantum yield;?2?relatively few methods for direct synthesis of white fluorescence CDs;?3?Solid-state CDs are easy quenched.Therefore,the preparation of high-performance CDs is still an urgent problem to be solved.A large number of studies have shown that carbon sources with large conjugated structures and doping elements can improve their fluorescence properties.In this paper,different aromatic hydrocarbon compounds used as carbon sources and doping elements are performed to prepare CDs with excellent properties.Specific work includes the following three parts:?1?We synthesized red fluorescence CDs under visible light excitation using m-dihydroxybenzene as carbon source and urea as doping reagent through solvothermal method,shown in Scheme 1.As-prepared CDs showed red fluorescence with maximum emission at 598 nm excited at 578 nm.The quantum yield of as-prepared CDs reached up to32.8%.As-prepared CDs can serve as very effective fluorescent probes for Hela cell imaging.In addition,the fluorescence of CDs solution was quenched directly by formaldehyde solution,and non-fluorescent CDs?NF-CDs?solution were recovered in the presence of ammonia water.Polyvinyl butyral?PVB?loaded NF-CDs?NF-CDs/PVB?films displayed significant color changes to detect ammonia gas directly under visible light without UV light.?2?We prepared the W-CDs using 1,6-Dihydroxynaphthalene?1,6-DHN?and L-Asparagine?L-Asn?as carbon sources through a simple in situ solvent-free carbonization method.The yield of W-CDs reached up to 95%.As-prepared W-CDs had dual-emissive peak at 451 and 518 nm under 365 nm excitation.By exploring the functional groups and hydroxyl positions of the carbon source,we speculated a possible reaction mechanism.In order to conquer solid-state fluorescence quenching of W-CDs,we used polyvinyl butyral?PVB?to disperse W-CDs.Due to the well-dissolved CDs in PVB,we had fabricated CDs/PVB composites for LEDs,as well as WLEDs with Commission Internationale de L'Eclairage?CIE?coordinates of?0.32,0.31?under UV excitation of 365 nm.?3?In order to obtain solid fluorescence and long-wavelength CDs that do not need to add any matrix,we chose 1,8-diaminonaphthalene with both amino groups and benzene ring,containing 5-sulfosalicylic acid as the carbon source.The yellow-green CDs solution was synthesized by solvothermal method.According to a series of proofs,the prepared CDs are hydrophobic.According to this property,different proportions of water are added to the CDs solution.When the proportion of water is 90%,the dispersed CDs in the solution are precipitated to obtain solid CDs.Under the irradiation of yellow-green fluorescence.By changing the functional groups on 5-sulfosalicylic acid to obtain sulfonic acid groups,the wavelength of CDs is red-shifted,and-OH,-COOH reacts with-NH₂ on1,8-diaminonaphthalene,after polymerization,dehydration and carbonization Yellow-green fluorescent CDs are obtained,and water-induced solid fluorescent CDs are obtained due to the hydrophobicity.