Research On Polarization Characteristics Of Liquid Crystal/gold Nanorod Composites Based On Photo-alignment

Liquid crystal has the characteristics of crystal anisotropy and liquid fluidity,and can respond to small external field stimuli.After doping nanoparticles into the liquid crystal material to form a nanomaterial/liquid crystal mixture,the nanoparticles will not significantly disturb the liquid crystal phase state.In terms of composite materials composed of metal nanostructures and liquid crystals,the liquid crystals are excited by an external field to change the orientation of the liquid crystals,thereby regulating the distribution of metal nanomaterials into an orderly arrangement,and the change of the surface plasmon resonance effect of metal nanomaterials can be studied.Gold nanorods and silver nanowires have lengths and diameters in the nanometer range,exhibiting distinct physical and chemical properties from bulk materials.By using different orientation methods,onedimensional nanomaterials such as gold nanorods and silver nanowires were orderly arranged into a specific structure,which could obtain low-cost,large-area materials for applications in optics and energy storage,including photovoltaic thin films,metamaterials,antennas,and nano computers.Based on photo-alignment technology,this thesis selected nematic liquid crystals and two representative one-dimensional nanomaterials as research objects,and conducted researches on their related properties such as orientation and polarization.First of all,this thesis used the method of "ligand replacement" to functioned the surface of gold nanorods,and realized the transfer of gold nanorods from aqueous solution to organic solution,so that the gold nanorods after ligand replacement could exist stably on a long time.The UV-Vis absorption spectrum of gold nanorods in organic solution was tested.Based on the above experimental results,the nematic liquid crystal/gold nanorod composites were prepared for this thesis,and their polarized light absorption characteristics after being oriented by photo-alignment technology were tested.The research data shows that the gold nanorods doped in the nematic liquid crystal could be oriented by the liquid crystal molecules to form an orderly arrangement,and the composite material have good polarization absorption characteristics.When the angle between the orientations was 0°,the polarization absorption intensity was the strongest,while the angle between the orientation and the polarization direction of the composite material is 90°,the polarization absorption intensity was the weakest.Secondly,based on the "bottom-up" approach,this thesis assembled gold nanorods and silver nanowires into two-dimensional nano-superstructures,three-dimensional dynamic control of gold nanorods/silver nanowires/liquid crystal composites based on photo-alignment technology was studied and analyzed.We first explored the adsorption effect of gold nanorods with different aspect ratios on the surface of silver nanowires.Then doped the prepared nano-superstructures into the nematic liquid crystals,the metal nano/liquid crystal composites were oriented by light-controlled orientation technology,and the effect of the gold nanorod/silver nanowire composite structure on the optoelectronic properties of liquid crystal was explored.The experimental data showed that the gold nanorod/silver nanowire composite material could be oriented in liquid crystal to form an ordered distribution,and the orientation order parameter S was 0.90.Through research and analysis,it was inferred that the composite material had polarization absorption characteristics.The gold nanorod/silver nanowire composite material reduced the threshold voltage and response time of the liquid crystal,and could well improve the optoelectronic properties of the liquid crystal.To sum up,this thesis studied the orientation,polarization absorption and electro-optic properties of one-dimensional nanomaterials in liquid crystals based on photo-alignment technology,and explored the preparation method and process of the principle optical components of composite materials composed of one-dimensional nanomaterials and liquid crystals,which could lay the foundation for the orderly construction of one-dimensional nanomaterials and their application in the field of optoelectronics.