title: Light-Driven Reversible Alignment Switching of Liquid Crystals Enabled by Azo Thiol Grafted Gold Nanoparticles.
abstract: Stimuli-directed alignment control of liquid crystals (LCs) with desired molecular orientation is currently in the limelight for the development of smart functional materials and devices. Here, photoresponsive azo thiol (AzoSH) was grafted onto gold nanoparticles (GNPs). The resulting hybrid GNPs were able to homogeneously mix with a commercially available nematic LC host, as evidenced by Cryo-TEM. Interestingly, the LC nanocomposites were found to undergo reversible alignment transition upon light irradiation as a consequence of the trans-cis photoisomerization of the azo groups on the GNP surface. LC molecules in either planar or bare glass cells were able to change their alignment to vertical upon UV irradiation, while the vertically aligned LC molecules returned to the planar or random orientation under visible irradiation. Neither the azo thiol molecules nor the unfunctionalized GNPs alone promoted the alignment of the LC molecules in the system upon light irradiation. The photoinduced vertical alignment without applied electric or magnetic field was very stable over time and with respect to temperature. Furthermore, an optically switchable device based on the photostimulated reversible alignment control of LCs was demonstrated.
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Chenming
authors.initials: C
authors.lastname: Xue
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Jie
authors.initials: J
authors.lastname: Xiang
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Hossein
authors.initials: H
authors.lastname: Nemati
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Hari Krishna
authors.initials: HK
authors.lastname: Bisoyi
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Karla
authors.initials: K
authors.lastname: Gutierrez-Cuevas
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 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, Ohio 44242 (USA).
authors.forename: Min
authors.initials: M
authors.lastname: Gao
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Shuang
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Deng-ke
authors.initials: DK
authors.lastname: Yang
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA).
authors.forename: Oleg D
authors.initials: OD
authors.lastname: Lavrentovich
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Dayton, OH 45433 (USA).
authors.forename: Augustine
authors.initials: A
authors.lastname: Urbas
authors.affiliation: Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242 (USA). qli1@kent.edu.
authors.forename: Quan
authors.initials: Q
authors.lastname: Li
keywords: gold nanoparticles; liquid crystals; photoisomerization; reversible switching; stimuli-responsive materials