Papers by Keyword: Colloidal Crystals

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Authors: Pavel Dyshlovenko, Anastasia Batanova, Elena Gladkova, Alexey Nagatkin, Azat Nizametdinov
Abstract: Elasticity of charge stabilized colloidal crystals is studied numerically within the approximation of static lattice. Description of the colloidal systems is based on the non-linear differential Poisson-Boltzmann equation. Corresponding boundary value problems are solved numerically by finite element method. The equilibrium pressure and elastic moduli are obtained for different values of the lattice parameter. The many-body effective interactions are briefly discussed.
Authors: Darrell J. Irvine, Agnieszka Stachowiak, Siddhartha Jain
Authors: Rong Fuh Louh, Yi Jui Huang, Ya Chih Tsai, Danny Ho, Doris Liao
Abstract: Fabrication of high sphericity, monodispersed microspheres (100~600 nm) of various oxides (SiO2, TiO2, ZnO, In2O3, SnO2) via sol-gel process and polystyrene (PS) microspheres (200~400 nm) via emulsion polymerization is presented. A high colloidal stability suspension was obtained by adjusting the zeta potential of such spheres and pH of the colloid. The 3-D photonic crystal (PhC) templates of opaline structure on ITO-coated glasses and silicon wafers were easily formed under electrophoretic self-assembly (EPSA) of microspheres under the influence of exerting electrical forces. Different setups of counter-electrode were attempted to establish an electrical field. The lattice constant of an ordered opal structure by EPSA can also be tuned by the electrical field gradient. Interestingly various self-assembled 3-D structures of silica microspheres in either symmetrical curvilinear profile or triangular ridges can be produced through EPSA route using specific counter-electrode setups. The measured optic properties of such 3-D PhC templates manifest photonic bandgap (PBG) based on planar-wave expansion (PWE) simulation to verify the existence of real PBG in PhC samples with tunable nanostructures. The PS PhC templates are currently used to easily transform into inverse opal structure (IOS) by infiltrating sol of other oxides with high dielectric constant (e.g. ZnO or TiO2) and filled with metallic nanoparticles (Ni or Cu) by electrochemical deposition or chemical bath deposition (CBD).
Authors: Qun Yan Li, Wei Min Gao, Yun Fa Chen, Peng Dong, Zhen Jiang Wu
Abstract: The silica colloidal crystal multilayers were deposited from ethanol suspensions with different particle concentrations by vertical deposition method. The microstructures and thicknesses of silica colloidal multilayers were characterized by scanning electron micrography. The thicknesses of colloidal crystal multilayers increased with the particle concentration increasing within a certain range of particles concentrations. When the particle concentration exceeded 2.48wt%, the thicknesses of colloidal crystal multilayers didn’t increased with the concentration increasing. Colloidal crystal multilayers with few defects could be deposited from the suspensions with the particle concentration 2.48wt%. The optical properties of the silica colloidal multilayers were investigated by a UV-Vis scanning spectrophotometer in normal incidence. They corresponded well to the microstructure obtained by SEM images.
Authors: Andrea Chiappini, Cristina Armellini, Alessandro Carpentiero, Laura Pasquardini, Lorenzo Lunelli, Alessandro Vaccari, Stefano Pelli, Anna Lukowiak, Cecilia Pederzolli, Giancarlo C. Righini, Roberta Ramponi, Maurizio Ferrari
Abstract: In this paper we report on the fabrication and the characterization of colloidal systems considering complementary structures based on responsive artificial opal both in direct and inverse configuration. We will discuss alternative systems such as: (i) chromatic composite structure as chemical sensor based on polystyrene (PS) nanoparticles (NPs) embedded in elastomeric matrix, where the application of specific organic solvents produces a variation of its color; (ii) metallic dielectric structures, where the infiltration of colloidal crystals with metallic nanoparticles permits to modify the optical properties of the common opal and can be usefully exploited as SERS substrates; (iii) inverse silica opal functionalized with fluorescent aptamers in order to develop bio-sensors in dye labelled fluorescence detection scheme.
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