β-NaGdF_(4)∶Yb^(3+),Er^(3+)/纤维素纳米晶胆甾型复合膜制备及光学性能

Preparation and Optical Properties ofβ-NaGdF_(4)∶Yb^(3+),Er^(3+)/Cellulose Nanocrystalline Cholesteric Composite Films

以稀土氯化物为原料、油酸和十八烯为溶剂,采用溶剂热法合成粒径为4.4 nm的β-NaGdF_(4)∶Yb^(3+),Er^(3+)上转换荧光纳米粒子,并将其分散于纤维素纳米晶(CNC)的悬浮液中,随后通过蒸发诱导自组装制备了β-NaGdF_(4)∶Yb^(3+),Er^(3+)/CNC胆甾型复合膜。采用X射线衍射(XRD)、透射电子显微镜(TEM)、傅里叶红外光谱(FTIR)和荧光光谱等分析手段对制备样品的结构、形貌和性能进行分析。结果表明,制备的NaGdF_(4)∶Yb^(3+),Er^(3+)上转换荧光纳米粒子的形貌为球形,结构为纯六方相,有良好的分散性,其分散液在980 nm激光激发下发出肉眼可见的明亮绿光。与纳米纤维素溶液自组装后获得同时具有上转换发光和结构色的β-NaGdF_(4)∶Yb^(3+),Er^(3+)/CNC胆甾型复合膜,少量β-NaGdF_(4)∶Yb^(3+),Er^(3+)的引入不改变纳米纤维素膜的胆甾型液晶结构。此外,纳米纤维素膜作为一维光子晶体在一定程度上可实现对β-NaGdF_(4)∶Yb^(3+),Er^(3+)荧光性能的调控,使其禁带边缘的荧光强度增强2.7倍。

β-NaGdF_(4)∶Yb^(3+),Er^(3+) upconversion fluorescent nanoparticles with the particle size of 4.4 nm were synthesized by solvothermal method using rare earth chlorides as raw material and oleic acid and octadecene as solvent.And then β-NaGdF_(4)∶Yb^(3+),Er^(3+)/CNC cholesteric composite films were prepared by evaporation-induced self-assembly of cellulose nanocrystalline(CNC)suspension with β-NaGdF_(4)∶Yb^(3+),Er^(3+) nanocrystals.The structure,morphology and properties of the prepared samples were analyzed by X-ray diffraction(XRD),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR)and fluorescence spectroscopy.The results show that the prepared NaGdF_(4)∶Yb^(3+),Er^(3+) upconversion material with a spherical morphology has a pure hexagonal phase and good dispersivity.And the solution can emit the bright green light under the excitation of a 980 nm laser.β-NaGdF_(4)∶Yb^(3+),Er^(3+)/CNC cholesteric composite films with both upconversion luminescence and structural colors were obtained after self-assembly with nanocellulose solution.The structure of the cholesteric liquid crystal of the nanocellulose was not changed with adding a small amount of β-NaGdF_(4)∶Yb^(3+),Er^(3+) nanoparticles.Meanwhile,it was found that the assembled chiral film,as a one-dimensional photonic crystal,could regulate the optical properties of β-NaGdF_(4)∶Yb^(3+),Er^(3+) to some extent,and the fluorescence intensity at the bandgap edge of the nanocellulose was enhanced by 2.7 times.