Preparation And Performance Of Solid-state Fluorescence Carbonized Polymer Dots

Carbonized polymer dots(CPDs)are luminescent materials with carbon cores and polymer shells,which have the unique properties of both carbon dots and polymers and are therefore widely used in LEDs,bioimaging,catalysis,fluorescent probes,and anti-counterfeiting.However,most CPDs are not only difficult to achieve solid-state fluorescence(SSF),which leads to fluorescence quenching of CPDs under high loading in the matrix,but also the fluorescence emission wavelength is mainly concentrated in the blue region.Therefore,it remains a great challenge to synthesize a CPDs with matrix-free SSF and tunable colorful fluorescence.In this context,two nitrogen-doped carbonized polymer dots were designed and synthesized for the construction of LEDs as well as fingerprinting by using monomers of polymers as raw materials,modulating the SSF properties of CPDs through monomers of polymers,and modulating the colorful fluorescence of CPDs through the introduction of N elements,the following studies were conducted:(1)Nitrogen-doped carbide polymer dots(HNCDs)with a particle size distribution range of about 3-8 nm were prepared by a one-step solvothermal method in ethanol solution using citric acid,urea and hydroxyethyl methacrylate as raw materials,and the fluorescence properties of HNCDs were investigated.HNCDs not only have bright green SSF(545 nm),but also have excellent fluorescence tunable properties,with the emission wavelength of HNCDs red-shifted from blue to red(453 nm-635 nm)with increasing concentration in ethanol solution,therefore,HNCDs were mixed with silica sol to prepare composites with concentrations of 0.5 wt%-45 wt%,which not only have controllable SSF but also have good stability.A series of LEDs with blue to red and white fluorescence in the wavelength range of464-656 nm were prepared by changing the type of LEDs chips and adjusting the content of HNCDs in the silica sol,with yellow,orange and red LEDs having high color saturation.(2)Nitrogen-doped polymer carbide dots(NCPDs)with a particle size distribution range of about 12-22 nm were prepared by a one-step solvothermal method in ethanol solution using citric acid,urea and acrylonitrile as raw materials.The fluorescence properties of NCPDs were investigated.The NCPDs powder not only has yellow SSF(570 nm)but also has excellent fluorescence tunable properties,the emission wavelength of NCPDs in ethanol solution shifts from blue to red(444 nm-600 nm)with increasing concentration,therefore,NCPDs were dissolved in silica sol to prepare composites with concentrations of 0.15 wt%-45wt%,and the NCPDs composites showed controllable SSF and good stability,and the composites were applied to make LEDs,the fabricated LEDs have multicolor fluorescence from blue to red in the light-emitting wavelength range of 453-638 nm,among which yellow-green to red LEDs have high color saturation.The excellent SSF performance of NCPDs expands their application in fingerprint identification,and the applicability of NCPDs in fingerprint identification is evaluated.