Date Published: November 22, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Youshen Wu, Hui Zhang, Aizhao Pan, Qi Wang, Yanfeng Zhang, Guijiang Zhou, Ling He.
Graphene quantum dot (GQD) encapsulated melamine‐formaldehyde (MF) polymer microspheres with uniform particle size and tunable high‐quality white‐light emissions are prepared via a polymer‐mediated GQD assembly and encapsulation strategy. In solution, GQDs are first aggregated with MF prepolymer through electrostatic interaction and further encapsulated inside the microspheres formed by polymerization of MF prepolymer under acid catalysis and heating. During this process, the aggregated GQDs are fixed in the MF polymer matrix with their emission extended from blue to full visible range, presenting bright white luminescence under ultraviolet excitation. The prepared white‐light‐emitting GQD‐MF microspheres exhibit uniform morphology with an average particle size of 2.0 ± 0.08 µm and their luminescence properties are effectively regulated by the doping concentration of GQDs in the MF polymer matrix. A series of white‐light‐emitting GQD‐MF microspheres with quantum yields from 0.83 to 0.43, Commission Internationale de L’Eclairage coordinates from (0.28, 0.28) to (0.33, 0.32), and color rendering index from 0.75 to 0.88 are obtained with excellent photostability and thermal stability. By dispersing the GQD‐MF microspheres in cross‐linked polydimethylsiloxane matrix, flexible film with dual functions of high‐quality white‐light‐emitting and light diffusion is obtained and successfully applied for white light‐emitting diode fabrication.
Materials: Melamine, paraformaldehyde, citric acid monohydrate, ethylenediamine, PVA 203, fluorescein, and Rhodamine 110 were purchased from Aladdin Chemistry Co., Ltd. THF, DMF, DMSO, dichloromethane, chloroform, and ethanol were purchased from Sinopharm Chemical Reagent Co., Ltd. PMMA (average molecular weight = 350 000 kDa) was purchased from J&K Chemical Ltd. The SYLGARD 184 silicone elastomer kit was purchased from Dow Corning. All chemicals used were of analytical grade and were used without further purification. Deionized water was used in all experiments.
The authors declare no conflict of interest.