Study Of Luminescence Characteristics Of Doped Fluorescence Liquid Crystals

Liquid crystal display device belongs to passive light-emitting display device.In order to improve its light utilization,we tried to explore three kinds of Novel Fluorescent Liquid Crystals.In this paper,a novel fluorescent liquid crystal was prepared by physical doping method.The method has the advantages of wide selection range of dopant particles,simple synthesis steps,low viscosity of the obtained liquid crystal material and good electro-optical characteristics.This method is mainly focused on the application of nano-particle doping,fluorescent molecular doping.Polyoxometalates are a class of nanocomplexes with well-defined structures and diverse compositions.It has many interesting properties,such as catalysis,nonlinear optics,photophysical properties and magnetism.In this paper,the elliptical polyoxometalates were modified by the alkyl chain of mono-octyl dimethyl ammonium bromide to form SEP.The SEP was used as the guest material to mix with the nematic liquid crystal BHR33400 to form a novel fluorescent liquid crystal with fluorescence characteristics.By different proportion of SEP doped liquid crystal to test its liquid crystal characteristic and fluorescence characteristic,we have obtained a 20% doped SEP doped liquid crystal with the widest nematic liquid crystal temperature range.The polarization ratio and order parameter of SEP doped liquid crystal decrease with the increase of SEP doping concentration.Quantum dots(QDs)are a new kind of fluorescent material with continuous excitation spectrum and narrow emission spectrum,which have long lifetime and high stability fluorescent.The CdSe QDs were dispersed in the nematic liquid crystal 5CB,and the response time of liquid crystal doped with different concentration CdSe QDs was studied.It was found that when the doping concentration reached 11.47wt%,the liquid crystalline state of the QDs doping liquid crystal disappeared.When the doping concentration of quantum dots is 1%,the response time of quantum dot doping liquid crystal is shortest,reaching 0.54 ms,and the shortening amplitude of response time was 49.5%.With the further increase of the concentration of quantum dots,doped liquid crystal conductivity increased,the response of the liquid crystal disappears in the electric field.Polyoxometalates and CdS QDs are all nanoparticles,and ZnO nanowires are one-dimensional nanomaterials.The influence of different size and shape of nano-particles on the luminescent and polarizing properties of nanoparticles-doped liquid crystals needs to be explored.It was found that the doping of ZnO nanowires had more influence on the homogeneity of liquid crystal orientation than that of quantum dots and Polyoxometalates.The polarization ratio and order parameter of ZnO nanowire doped liquid crystal fist increased and then decreased with the increase of ZnO nanowires doping amount.0.30% ZnO nanowire doped liquid crystal has the largest polarization ratio and order degree parameters,respectively 5.664 and 0.609.The experimental results show that the fluorescence polarization of the one-dimensional ZnO nanowire-doped liquid crystal is greatly enhanced,compared with the SEP-doped fluorescent liquid crystal.