【作者】 王磊；

【导师】 王春雷； 杨和逸；

【作者基本信息】 东南大学 ， 电子信息（专业学位）， 2023， 硕士

【摘要】 碳点基室温磷光材料的研究取得了很大进展,并在许多领域展示了广阔的应用前景。然而,尽管取得了一些重要成果,该类材料仍面临一些挑战和限制。一方面,碳点基室温磷光材料的磷光效率相对较低,限制了其在实际应用中的应用范围。另一方面,碳点基室温磷光材料目前主要表现为单一的磷光颜色。在许多应用场景中,需要具备多色磷光的材料来实现更丰富的功能和效果。针对以上问题,本论文对碳点与三聚氰胺(Melamine,MA)制备的复合材料的磷光性质进行了深入研究,主要研究内容如下:(1)采用氮掺杂碳点(N-doped Carbon Dots,NCDs)与MA基质复合的方式,成功制备了NCDs@MA复合材料。这种复合材料既有黄绿色的荧光,荧光量子效率为31.64%,而且能够在室温环境下发射出蓝绿色的磷光,并持续7秒。TEM、XRD、XPS和FT-IR表征发现水热法制备的NCDs的平均粒径大小为3.1 nm,表面具有丰富的氨基和羧基;NCDs@MA材料主体是MA,且XPS结果中O的含量为3.2%,证明了NCDs成功嵌入到了NCDs@MA中。实验确定了制备过程中MA的最佳量为0.375 g,最佳的加热时长为3 h。(2)确定了NCDs@MA的荧光和高强度、长时间室温磷光的来源。实验发现NCDs固体无荧光,而嵌入到MA中后生成的NCDs@MA具有固体荧光。进一步研究确定NCDs无固态荧光主要是因为其具有聚集诱导猝灭,当NCDs嵌入MA中后,MA充当了类似溶剂的作用,避免了聚集诱导猝灭。通过对比实验确定了NCDs@MA的荧光来源其内部的NCDs,磷光来自于MA。同时FT-IR确定了NCDs@MA的磷光强度远高于MA的磷光强度的原因是由于NCDs与MA之间的氢键作用。基于NCDs@MA的长波长荧光-短波长磷光特性,将其成功地应用在防伪和指纹识别领域。(3)利用NCDs-1与MA结合,成功制备了NCDs-1@MA复合材料,这种材料表现出激发依赖的蓝色固态荧光。通过对激发光谱、吸收光谱和FT-IR光谱的分析,可以确定NCDs-1@MA的固态荧光来源于C=O。另外,实验发现用MA包裹的其他碳点也能表现出固态荧光,证明了MA包裹实现碳点固态发光的策略具有通用性,对大多数碳点适用。(4)首次制备了具有双色固态磷光的NCDs-1@MA,其在365 nm激发时具有绿色磷光,而在450 nm激发时具有橙色磷光。研究结果表明绿色磷光来源于MA,橙色的磷光来自于NCDs-1。进一步研究发现,复合材料的磷光取决于NCDs-1和基质之间的相互作用,NCDs-1可以和PVA与MA形成氢键,与PEG不能形成氢键,因此NCDs-1@PVA和NCDs-1@MA表现出450 nm激发下的橙色磷光,NCDs-1@PEG在450 nm激发下无磷光。基于NCDs-1@MA的磷光性质,制备了双色的高级防伪材料。更多还原

【Abstract】 The research on carbon dot-based room temperature phosphorescent materials has made significant progress and demonstrated broad application prospects in various fields.However,despite the important achievements,these materials still face challenges and limitations.On one hand,the phosphorescent efficiency of carbon dot-based room temperature phosphorescent materials is relatively low,limiting their practical applications.On the other hand,these materials currently exhibit a single phosphorescent color,whereas many applications require materials with multiple phosphorescent colors to achieve richer functionality and effects.In response to these issues,this study conducted in-depth research on the phosphorescent properties of carbon dots and their composite materials with melamine(MA).The main research contents are as follows:(1)NCDs@MA composite materials were successfully prepared by combining nitrogendoped carbon dots(NCDs)with the MA matrix.These composite materials exhibited yellowgreen fluorescence with a fluorescence quantum efficiency of 31.64%.Moreover,they emitted blue-green phosphorescence at room temperature,lasting for 7 seconds.Characterization using TEM,XRD,XPS,and FT-IR revealed that the average particle size of NCDs synthesized by the hydrothermal method was 3.1 nm,and the NCDs possessed abundant amino and carboxyl groups on the surface.The main component of NCDs@MA material was MA,with an oxygen content of 3.2% according to XPS analysis,confirming the successful incorporation of NCDs into NCDs@MA.The optimized amount of MA in the preparation process was determined to be 0.375 g,with an optimized heating duration of 3 hours.(2)The origins of the fluorescence and high-intensity,long-lasting room temperature phosphorescence in NCDs@MA were investigated.It was observed that NCDs themselves did not exhibit solid-state fluorescence,but the fluorescence was obtained when NCDs were embedded in MA.Further research revealed that the lack of solid-state fluorescence in NCDs was mainly due to aggregation-caused quenching(ACQ).However,when NCDs were embedded in MA,MA acted as a solvent-like medium,preventing aggregation-caused quenching.Comparative experiments confirmed that the fluorescence of NCDs@MA originated from NCDs,while the phosphorescence originated from MA.FT-IR analysis also revealed that the significantly enhanced phosphorescence intensity of NCDs@MA compared with that of MA can be attributed to the hydrogen bonding interactions between NCDs and MA.Based on the long-wavelength fluorescence and short-wavelength phosphorescence characteristics of NCDs@MA,this material was successfully applied in anti-counterfeiting and fingerprint recognition.(3)NCDs-1@MA composite materials were prepared by combining NCDs-1 with MA,exhibiting excitation-dependent blue solid-state fluorescence.Analysis of the photoluminescence excitation(PLE)spectra,absorption spectra,and FT-IR spectra confirmed that the solid-state fluorescence of NCDs-1@MA originated from the C=O group.Additionally,it was observed that other CDs wrapped with MA also exhibited solid-state fluorescence,indicating the generality of the strategy to achieve solid-state emission of CDs through MA encapsulation.(4)For the first time,a novel dual-color solid-state phosphorescent material,NCDs-1@MA,was prepared,emitting green phosphorescence after 365 nm excitation and orange phosphorescence after 450 nm excitation.The research results showed that the green phosphorescence originated from MA,while the orange phosphorescence originated from NCDs-1.Further investigations revealed that the orange phosphorescence of the composite material depended on the interaction between NCDs-1 and the matrix.NCDs-1 could form hydrogen bonding with PVA and MA but not with PEG.Therefore,NCDs-1@PVA and NCDs-1@MA both exhibited orange phosphorescence after 450 nm excitation,while NCDs-1@PEG showed no phosphorescence after 450 nm excitation.Based on the phosphorescent properties of NCDs-1@MA,advanced anti-counterfeiting materials with dual colors were developed.更多还原