scholarly journals Fabricación y caracterización óptica de cristales coloidales de alta calidad formados por esferas de SiO2 de 225 nm de diámetro con empaquetamiento fcc crecidos por el método convectivo de auto-ensamblado de deposición vertical.

2010 ◽  
Vol 15 (2) ◽  
pp. 150 ◽  
Author(s):  
Octavio Alejandro Castañeda-Uribe ◽  
Juan Carlos Salcedo-Reyes ◽  
Henry Alberto Méndez-Pinzón ◽  
Aura Marina Pedroza-Rodríguez
Keyword(s):  
Photonic Crystals ◽  
Self Assembly ◽  
Volume Fraction ◽  
Colloidal Crystals ◽  
Optical Characterization ◽  
Bragg Diffraction ◽  
Face Centered Cubic ◽  
High Quality ◽  
Assembly Method ◽  
Face Centered

<p><strong>Objective:</strong> Fabrication and optical characterization of close-packed 225 nm SiO<sub>2</sub> -based colloidal crystals<strong>. Materials and methods:</strong> The vertical convective self-assembly method is used to grow high-quality 225 nm close-packed SiO<sub>2</sub>-based colloidal crystals. An annealing process (550°C) is made in order to improve the mechanical stability of the sample. Optical characterization is done by angle-resolved transmission spectroscopy (A-RTS) and structural characterization by Scanning Electron Microscopy (SEM). <strong>Results:</strong> Both, A-RTS and SEM, show that with the vertical convective self-assembly method, with the appropriate parameters of temperature of evaporation (60°C), volume fraction of the colloidal suspension (0.2% w/w) and acidity (pH=6), highly ordered close packed face centered cubic (fcc) SiO<sub>2</sub> based colloidal crystals are obtained. <strong>Conclusions:</strong> The growth of high-quality (long range order and defect-free) face centered cubic opal-based photonic crystals is reported.</p> <p><strong>Key words:</strong><em> </em>Photonic crystals, colloidal crystals, artificial opals, vertical convective deposition method, Bragg diffraction</p><br /><br />

Preparation and Characterization of the Ordered SiO2 Colloidal Crystallization Films

2008 ◽  
Vol 368-372 ◽  
pp. 1389-1391 ◽  
Author(s):  
Shuan Gui Qing ◽  
Bo Liu ◽  
Xun Liang ◽  
Hai Yang Li ◽  
Wei Zhong Lv ◽  
...  
Keyword(s):  
Self Assembly ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Assembly Method ◽  
Colloidal Crystallization ◽  
The Face ◽  
Infrared Spectrometer ◽  
Face Centered ◽  
Sio2 Spheres

Multilayer SiO2 crystals modified by alkoxysilanes were fabricated by the vertical deposition technique combined with self-assembly method. The SiO2 colloidal crystallization was prepared by the traditional Stöber-Fink-Bohn method, and modified by different alkoxysilanes to investigate the properties of the films. The films fabricated by the ordering of SiO2 spheres were investigated by infrared spectrometer, X-ray diffraction, scanning electron microscope, UV-visible spectrophotometer. The results showed that thin film is the face-centered cubic structures and the spheres are [111]-oriented.

scholarly journals Synthesis and Study of the Optical Properties of PMMA Microspheres and Opals

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2171
Author(s):  
Mayra Matamoros-Ambrocio ◽  
Enrique Sánchez-Mora ◽  
Estela Gómez-Barojas ◽  
José Alberto Luna-López
Keyword(s):  
Band Gap ◽  
Self Assembly ◽  
Photonic Band Gap ◽  
Average Diameter ◽  
Reflectance Spectra ◽  
Face Centered Cubic ◽  
Indirect Transition ◽  
Specular Reflectance ◽  
Assembly Method ◽  
Face Centered

Polymethylmethacrylate (PMMA) microspheres were synthesized by surfactant-free emulsion polymerization. These microspheres were used to obtain opals by the self-assembly method. Monomer and initiator quantities were varied systematically to monitor the size of PMMA microspheres. From SEM and DLS measurements, a trend was observed showing as the monomer and initiator amounts increased the average diameter of PMMA microspheres increased except when a minimum monomer amount was reached, for which the size of the microspheres remained practically constant. Diffuse reflectance spectra were processed by the Kubelka–Munk treatment to estimate the energy band gap (Eg) of the PMMA microspheres. It was found that PMMA microspheres present an indirect transition. From SEM micrographs, it is seen that PMMA opals photonic crystals are formed by microspheres in a uniform periodic face-centered cubic (fcc) array. Variable-angle specular reflectance spectra show that the opals possess a pseudo photonic band gap (PBG) in the visible and near-IR regions. Furthermore, it was found that PBGs shift towards larger wavelengths as the average diameter of the PMMA microspheres increases.

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