title: Frequency-Driven Self-Organized Helical Superstructures Loaded with Mesogen-Grafted Silica Nanoparticles.
abstract: Adding colloidal nanoparticles into liquid-crystal media has become a promising pathway either to enhance or to introduce novel properties for improved device performance. Here we designed and synthesized new colloidal hybrid silica nanoparticles passivated with a mesogenic monolayer on the surface to facilitate their organo-solubility and compatibility in a liquid-crystal host. The resulting nanoparticles were identified by1H NMR spectroscopy, TEM, TGA, and UV/Vis techniques, and the hybrid nanoparticles were doped into a dual-frequency cholesteric liquid-crystal host to appraise both their compatibility with the host and the effect of the doping concentration on their electro-optical properties. Interestingly, the silica-nanoparticle-doped liquid-crystalline nanocomposites were found to be able to dynamically self-organize into a helical configuration and exhibit multi-stability, that is, homeotropic (transparent), focal conic (opaque), and planar states (partially transparent), depending on the frequency applied at sustained low voltage. Significantly, a higher contrast ratio between the transparent state and scattering state was accomplished in the nanoparticle-embedded liquid-crystal systems.
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH, 44242, USA.
authors.forename: Karla G
authors.initials: KG
authors.lastname: Gutierrez-Cuevas
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH, 44242, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH, 44242, USA.
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Zheng
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH, 44242, USA.
authors.forename: Hari K
authors.initials: HK
authors.lastname: Bisoyi
authors.affiliation: Department of Ophthalmology and Visual Science and Department of Electrical and Computer Engineering, Ohio State University, Columbus, OH, 43212, USA.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Li
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, OH, 45433, USA.
authors.forename: Loon-Seng
authors.initials: LS
authors.lastname: Tan
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, OH, 45433, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Vaia
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH, 44242, USA. qli1@kent.edu.
authors.forename: Quan
authors.initials: Q
authors.lastname: Li
mesh_terms: D003102:Colloids / Q000138:chemical synthesis / Q000737:chemistry; D050866:Liquid Crystals / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D003102:Colloids; D012822:Silicon Dioxide
keywords: frequency dependence; helical superstructures; liquid crystals; self-organization; silica nanoparticles; tunable transparency