Anisotropic shift of surface plasmon resonance of gold nanoparticles doped in nematic liquid crystal

Abstract

Study of the liquid crystal (LC) director around nanoparticles has been an important topic of research very recently, since it allows design and fabrication of next-generation LC devices that are impossible in the past. In our experiment, alkanethiol-capped gold nanoparticles (GNPs) were dispersed in nematic LC. Analysis of the LC director around GNPs was performed by investigating the behavior of surface plasmon polariton (SPP) absorption peaks of the GNPs using spectrophotometry technique. It is found that the incident linearly polarized light orientated at 0°, 45°, and 90° angles with respect to the rubbing direction experiences varying interaction with the LC medium. The corresponding transmission of light reveals the anisotropic shift in wavelength of SPP peak. The anisotropic behavior of SPPs of the GNPs is in agreement with theoretical calculations. Science 275(5307), 1770-1773 (1997). 8. R. Yamamoto, "Simulating particle dispersions in nematic liquid-crystal solvents," Phys. Rev. Lett. 87(7), 075502 (2001). 9. J. Fukuda, M. Yoneya, and H. Yokoyama, "Nematic liquid crystal around a spherical particle: Investigation of the defect structure and its stability using adaptive mesh refinement," Eur Phys J E Soft Matter 13(1), 87-98 (2004). 10. M. A. Bates, "Nanospheres in a nematic liquid crystal solvent: the influence of particle size," Liq. Cryst. 32(11-12), 1525-1529 (2005 ©2014 Optical Society of America

Impact of titanium dioxide nanoparticles on purification and contamination of nematic liquid crystals

“…The application of LCs includes metamaterials [4], photonic crystals [5], plasmonic structures [6], THz devices [7], sensors [8], diffractive optics [9], adaptive lens technologies [10] and vision correction [11], as well as tunable filters [12] and dispersion for imaging [13]. In addition, nanoparticles can induce other new functions in liquid crystals, including improved response time [14–15], surface plasmon resonance [16], and improvements in alignment [17]. …”

Conjugation of Nanomaterials and Nematic Liquid Crystals for Futuristic Applications and Biosensors

“…The conducting electrodes are designed using a transparent indium-tin-oxide (ITO) thin film deposited on a glass substrate. A desired pattern of the ITO electrode can be carved using photolithography techniques [ 44 , 55 , 56 , 57 , 58 , 64 ]. In order to achieve alignment of the NLC molecules, one needs to pre-treat these electrodes with appropriate chemicals.…”

“…Such structures could be like Saturn rings, boojams, and hedghogs, which have been studied both theoretically and experimentally, showing the dependence on their size and shape [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. The anisotropic molecular alignment around gold nanoparticles (GNPs) has been verified in experimental observations of NLC materials [ 44 ]. The addition of GNPs in NLCs has shown a remarkable red shift of the surface plasmon polaritons (SPP) peak in the absorption spectra of NLC/GNP composite systems due to an increment in the refractive index of an NLC when light is polarized parallel to the director of the NLC [ 45 ].…”

MOF‐on‐MOF: Oriented Growth of Multiple Layered Thin Films of Metal–Organic Frameworks

“…[23] Theo bserved anisotropic plasmon damping may thus result by anisotropic thermal conductivity (phonon diffusion) in the host MOF matrix as it is expected that for the Cu 2 (BPYDC) 2 MOF the thermal conductivity is larger along b-axis (pore direction). [24] Theo bserved shift in the plasmon resonance peak to longer wavelengths with increasing angle between light polarization and a-axis of Cu 2 (BPYDC) 2 likely results from dielectric constant anisotropy of MOF matrix [25] as it is well-known that plasmon resonance wavelengths are longer when metal nanoparticles are accommodated in am atrix with larger dielectric constants. [26] Thep recise alignment of this MOF-on-MOF system allows for the plasmon resonance of guest Ag NPs to be modulated by changing the orientation of the MOF thin film.…”

“…[22] Figure 5b shows the polarization-dependent UV/Vis absorption spectra measured with an integrated sphere in areflection mode.The difference absorption spectra before and after the Ag NPs impregnation are also shown in Figure 5c.W en ote there are two types of polarization-dependent changes in the plasmon resonance of Ag NPs:plasmon damping and peak shift. [24] Theo bserved shift in the plasmon resonance peak to longer wavelengths with increasing angle between light polarization and a-axis of Cu 2 (BPYDC) 2 likely results from dielectric constant anisotropy of MOF matrix [25] as it is well-known that plasmon resonance wavelengths are longer when metal nanoparticles are accommodated in am atrix with larger dielectric constants. 400-500 nm (Figure 5b)c learly decreases when the angle between the aaxis of MOF and the light polarization increases from 08 8 to 908 8.P revious reports indicated that the damping of plasmon resonance can take place through an electron-phonon interaction.…”