The Study On Silver Nanoparticles And Liquid Crystal Composites Base On Plasmon Resonance Effect

Surface plasmon resonance (SPR) is a specific optical phenomenon which is generated by the interaction between free electrons of matel and light, and the researches on plasmonic device have attracted people’s attention in recent years with the improvement of nano-processing technology. The structural color and medium sensitivity that base on SPR effect have important applications in high resolution displays, color filters, nonlinear optics, biological sensers, and other fields. Among them, active switching of SPR structural color and refractive index sensitivity is an important branch of relevant researches. Liquid crystal (LC) materials are ideal candidates for active regulating of surface plasmons since the feature of external stimulation response. In this thesis, we combine silver nanoparticles (Ag NPs) and LC materials to construct composites, and actively regulate the structural color and optical behavior base on localized surface plasmon resonance (LSPR) of Ag NPs. The mains are as followed:1. The Ag NPs were prepared by oleylamine and oleic acid as ligands and assembled to close packed monolayer array through air-liquid interface assembly. The absorption, reflectance spectra and structural color angle dependency of Ag NPs array have been studied. Subsequently, we investigate the proportion of liquid crystal elastomer (LCE) in detail, especially the influence of crosslinker HDDA and LC monomer A6OCB contents on the clear point (Tc) and deformation of LCE, and confirm the proportion of LCE at last. Finally, we study the orientation effect of Ag NPs array on LC molecules, and the results suggest Ag NPs array can induce LC molecules to form vertical orientation. Vertical and hybrid orientation composites can be fabricated if combining Ag NPs array with vertical and planar orientation layer.2. Vertical and hybrid orientation Ag NPs/LCE composites were prepared by combining Ag NPs array and LCE through photopolymerization. The distribution of Ag NPs in LCE is investigated and the active regulating reflectance spectra of composites are achieved by temperature control. For studying the mechanism, we use finite element simulation software COMSOL which base on finite-difference time-domain method to simulate the process of spectra regulation. The simulation results suggest that the reason of reflectance spectra changes are because the deformation of LCE induces the LSPR change of Ag NPs. At last, according to the characteristics of two composites, we design the applications as "thermal camouflage skin" and temperature sensitive color changing switch, respectively.3. We synthesize six achiral bend and T-shaped hydrogen bonded assembles (HBAs), and study their form, thermal stability, phase state and the effect on blue phase (BP) stability. It is found the doping of HBAs can broaden BP temperature range. We study the mechanism of HBAs stabilizing BP by calculating the molecular configuration at the lowest energy, bend angle, hydrogen bound interaction energy and surface electronic distribution of HBAs through computer molecule simulation. Subsequently, we use polymer stabilized BP (PSBP) to broaden BP temperature range, and study the influence of HBAs, monofunctional monomer and bifunctional monomer contents on BP stability. It is suggested BP polymer network has "memory effect" which can retain the specific cubical lattice structure of BP. These results provide the foundation for the fabrication of BP template in Ag NPs/BP polymer template composite.4. Ag NPs/BP polymer template plasmonic composites were prepared by in situ reducing silver nitrate in BP polymer template, and the optical activity and medium sensitivity are studied. There’s a feature signal which is very sensitive to surrounding medium at Ag NPs plasmon resonance wavelength in circular dichroism (CD) spectrum of the composite. We find the chiral driving force of the composite originates from BP periodic cubic lattice structure which is memorized by BP template. The metal-dielectric interface is formed since Ag NPs loads on the surface of BP polymer network. When the LSPR of Ag NPs is excited, the composite will show a CD signal at the feature wavelength due to the macroscopic chiral assembly of Ag NPs.