1,721,138 research outputs found
Angle-resolved transmission spectroscopy of opal films
No full textThe angular behavior of light transmission through opal films over a broad range of wavelengths and angles was investigated. The opal films were prepared using the capillary deposition method (CDM). Many well-defined diffraction peaks were detected and indicate that the CDM results in opal films with high quality. Peaks coinciding at normal incidence split when samples are rotated. The angular shift of these peaks was found to satisfy the kinematical diffraction theory very well. Furthermore, the variation of intensity with incident angle can be interpreted in terms of a simplified dynamical diffraction theory. Moreover, the presence of two differently oriented domains in CDM-made opal films is essential in discussing the measured spectra
Polarization angular-resolved transmission spectroscopy of opal films
No full textIn this paper, we investigated the angular behavior of light transmission through opal films over a broad range of wavelengths and angles. The opal films were prepared using the capillary deposition method (CDM). The observation of many well-defined diffraction peaks indicates that the CDM results in opal films with high quality. Peaks overlapping at normal incidence split when samples are rotated. The angular shift of these peaks was found to satisfy the kinematical diffraction theory very well. Furthermore, the variation of intensity with incident angle can be interpreted in terms of a simplified dynamical diffraction theory. Moreover, the presence of two differently oriented domains in CDM-made opal films is essential in discussing the measured spectra. These domains can be assigned to parallel microscopic stripes of ABC and ACB type fcc structures. Angular-resolved spectroscopy with polarized incident light shows interesting polarization dependence of light propagation inside opals
Chiral Permselectivity in Surface-Modified Nanoporous Opal Films
No full textNanoporous 7 μm thin opal films comprising 35 layers of 200 nm diameter SiO2 spheres were assembled on Pt electrodes and modified with chiral selector moieties on the silica surface. Diffusion of chiral redox species through the opals was studied by cyclic voltammetry. The chiral opal films demonstrate high selectivity for transport of one enantiomer over the other. This chiral permselectivity is attributed to the surface-facilitated transport utilizing noncovalent interactions between the chiral permeant molecules and surface-bound chiral selectors
Dye‐Loaded Mechanochromic and pH‐Responsive Elastomeric Opal Films
Get PDFIn this work, the preparation and fabrication of elastomeric opal films revealing reversible mechanochromic and pH-responsive features are reported. The core-interlayer-shell (CIS) particles are synthesized via stepwise emulsion polymerization leading to hard core (polystyrene), crosslinked interlayer (poly(methyl methacrylate-co-allyl methacrylate), and soft poly(ethyl acrylate-co-butyl acrylate-co-(2-hydroxyethyl) methacrylate) shell particles featuring a size of 294.9 ± 14.8 nm. This particle architecture enables the application of the melt-shear organization technique leading to elastomeric opal films with orange, respectively, green brilliant reflection colors dependent on the angle of view. Moreover, the hydroxyl moieties as part of the particle shell are advantageously used for subsequent thermally induced crosslinking reactions enabling the preparation of reversibly tunable mechanochromic structural colors based on Bragg's law of diffraction. Additionally, the CIS particles can be loaded upon extrusion or chemically by a postfunctionalization strategy with organic dyes implying pH-responsive features. This convenient protocol for preparing multi-responsive, reversibly stretch-tunable opal films is expected to enable a new material family for anti-counterfeiting applications based on external triggers
Dye‐Loaded Mechanochromic and pH‐Responsive Elastomeric Opal Films
Get PDFIn this work, the preparation and fabrication of elastomeric opal films revealing reversible mechanochromic and pH‐responsive features are reported. The core–interlayer–shell (CIS) particles are synthesized via stepwise emulsion polymerization leading to hard core (polystyrene), crosslinked interlayer (poly(methyl methacrylate‐co‐allyl methacrylate), and soft poly(ethyl acrylate‐co‐butyl acrylate‐co‐(2‐hydroxyethyl) methacrylate) shell particles featuring a size of 294.9 ± 14.8 nm. This particle architecture enables the application of the melt‐shear organization technique leading to elastomeric opal films with orange, respectively, green brilliant reflection colors dependent on the angle of view. Moreover, the hydroxyl moieties as part of the particle shell are advantageously used for subsequent thermally induced crosslinking reactions enabling the preparation of reversibly tunable mechanochromic structural colors based on Bragg's law of diffraction. Additionally, the CIS particles can be loaded upon extrusion or chemically by a postfunctionalization strategy with organic dyes implying pH‐responsive features. This convenient protocol for preparing multi‐responsive, reversibly stretch‐tunable opal films is expected to enable a new material family for anti‐counterfeiting applications based on external triggers
Reversible Light‑, Thermo‑, and Mechano-Responsive Elastomeric Polymer Opal Films
No full textA new strategy to achieve easily
scalable triple stimuli-responsive
elastomeric opal films for applications as stretch-tunable photonic
band gap materials is reported. Novel monodisperse highly functional
core-interlayer-shell beads are obtained by semicontinuous emulsion
polymerization featuring a temperature-sensitive fluorescent rhodamine
dye either locally restricted in the core or the shell of prepared
beads. After extrusion and compression molding, homogeneous elastomeric
opal films with fascinating stretch-tunable and temperature-dependent
fluorescent properties can be obtained. Applying strains of only a
few percent lead to significant blue shift of the reflected colors
making these films excellent candidates for applications as deformation
sensors. Higher strains up to 90% lead to a tremendous Bragg reflection
color change caused by transition from the (111) to the (200) lattice
plane. The well-ordered opaline structure with its stop band at the
emission frequency of the incorporated fluorescent dye shows remarkable
angle-dependent fluorescence suppression. Herein described elastomeric
opal films can be valuable in a wide range of applications such as
rewritable 3D optical data storage, tunable laser action, and sensing
materials
Optical Analysis of the Fine Crystalline Structure of Artificial Opal Films
Get PDFHerein, we present a detailed analysis of the structure of artificial opal films. We demonstrate that, rather than the generally assumed face centered cubic lattice of spheres, opal films are better approximated by rhombohedral assemblies of distorted colloids. Detailed analysis of the optical response in a very wide spectral range (0.4 ≤ a/λ ≤ 2, where a is the conventional lattice constant), as well as at perpendicular and off-normal directions, unambiguously shows that the interparticle distance coincides very approximately with the expected diameter only along directions contained in the same close-packed plane but differs significantly in directions oblique to the [111] one. A full description of the real and reciprocal lattices of actual opal films is provided, as well as of the photonic band structure of the proposed arrangement. The implications of this distortion in the optical response of the lattice are discussed.Peer reviewe
Optical Analysis of the Fine Crystalline Structure of Artificial Opal Films
No full textHerein, we present a detailed analysis of the structure of artificial opal films. We demonstrate that, rather than the generally assumed face centered cubic lattice of spheres, opal films are better approximated by rhombohedral assemblies of distorted colloids. Detailed analysis of the optical response in a very wide spectral range (0.4 ≤ a/λ ≤ 2, where a is the conventional lattice constant), as well as at perpendicular and off-normal directions, unambiguously shows that the interparticle distance coincides very approximately with the expected diameter only along directions contained in the same close-packed plane but differs significantly in directions oblique to the [111] one. A full description of the real and reciprocal lattices of actual opal films is provided, as well as of the photonic band structure of the proposed arrangement. The implications of this distortion in the optical response of the lattice are discussed
Thermo-cross-linked Elastomeric Opal Films
No full textAn efficient and convenient thermal
cross-linking protocol in elastomeric opal films leading to fully
reversible and stretch-tunable optical materials is reported. In this
study, functional monodisperse core–shell particles were arranged
in a face-centered cubic (fcc) lattice structure by a melt flow process.
A problem up to now was that un-cross-linked films could not be drawn
fully reversibly and hence lost their optical and mechanical performance.
After thermal cross-linking reaction, the obtained films can be drawn
like rubbers and the color of their Bragg reflection changes because
of controlled lattice deformation, which makes the cross-linked films
mechanochromic sensors. Different techniques were developed for the
cross-linking of the films a posteriori, after their preparation in
the melt flow process. A photo-cross-linking approach was reported
earlier. This study now deals with a very efficient thermo-cross-linking
approach based on the chemistry of hydroxyl- and isocyanate-functionalities
that form urethane bridges. The focus of the present work is the mechanism
and efficiency of this cross-linking process for elastomeric opal
films with excellent mechanical and optical properties
Additional file 1 of Tailoring conductive inverse opal films with anisotropic elliptical porous patterns for nerve cell orientation
No full textAdditional file 1: Figure S1. SEM images of (a) the silica colloidal crystal template, (b) the PS hybrid colloidal crystal template, (c) the PS inverse opal film. Scale bars are 500 nm. Figure S2. Different stretching degrees. (a) 3-times, (b) 6-times, (c) 9-times, (d) 12-times stretched PS inverse opal films. Scale bars are 1 μm. Figure S3. (a) MTT assays and (b) adhesion properties of PC12 cells cultured on ordinary glass slides, PS substrates stretched at 0°, 15°, 30°, 45° for 1 day, 2 days, and 3 days, respectively. Error bars represent SD. Figure S4. (a) Immunofluorescence image, (b) SEM image, (c) angle distribution of neurites of PC12 cells cultured on ordinary glass slides. Scale bars are 50 μm. Figure S5. Orientation angle frequency distribution of PC12 cells cultured on PS inverse opal films stretched at different angles. θ or θ’ means the angle between the direction of neurite (the red dotted line) and the stretching orientation (the black solid line), respectively. Figure S6. Raman spectrum of PEDOT:PSS-doped PAAm hydrogels. Figure S7. (a) MTT assays and (b) adhesion properties of PC12 cells cultured on ordinary glass slides, PS inverse opal films, composite films for 1 day, 2 days, and 3 days, respectively. Error bars represent SD. Figure S8. (a) Differentiation rates of PC12 cells cultured on ordinary glass slides, PS inverse opal films and composite films on the 7th day. (b) Orientation angle frequency distribution of PC12 cells on PS inverse opal films and composite films
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