title: Nonlinear photoluminescence imaging of isotropic and liquid crystalline dispersions of graphene oxide.
abstract: We report a visible-range nonlinear photoluminescence (PL) from graphene oxide (GO) flakes excited by near-infrared femtosecond laser light. PL intensity has nonlinear dependence on the laser power, implying a multiphoton excitation process, and also strongly depends on a linear polarization orientation of excitation light, being at maximum when it is parallel to flakes. We show that PL can be used for a fully three-dimensional label-free imaging of isotropic, nematic, and lamellar liquid crystalline dispersions of GO flakes in water. This nonlinear PL is of interest for applications in direct label-free imaging of composite materials and study of orientational ordering in mesomorphic phases formed by these flakes, as well as in biomedical and sensing applications utilizing GO.
authors.affiliation: Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States.
authors.forename: Bohdan
authors.initials: B
authors.lastname: Senyuk
authors.forename: Natnael
authors.initials: N
authors.lastname: Behabtu
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Pacheco
authors.forename: Taewoo
authors.initials: T
authors.lastname: Lee
authors.forename: Gabriel
authors.initials: G
authors.lastname: Ceriotti
authors.forename: James M
authors.initials: JM
authors.lastname: Tour
authors.forename: Matteo
authors.initials: M
authors.lastname: Pasquali
authors.forename: Ivan I
authors.initials: II
authors.lastname: Smalyukh
mesh_terms: D016880:Anisotropy; D006108:Graphite / Q000737:chemistry*; D007834:Lasers; D050866:Liquid Crystals / Q000032:analysis / Q000737:chemistry*; D008163:Luminescent Measurements / Q000379:methods*; D008422:Materials Testing / Q000379:methods; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D017711:Nonlinear Dynamics; D010087:Oxides / Q000737:chemistry; D010316:Particle Size
chemical_list: D010087:Oxides; D006108:Graphite