Abstract
Cracks and defects, which could result in lower reflectivity and larger full width at half maximum (FWHM), are the major obstacles for obtaining highly ordered structures of colloidal crystals (CCs). The high-quality CCs with high reflectivity (more than 90%) and 9.2 nm narrow FWHM have been successfully fabricated using a fixed proportion of a soft matter system composed of silica particles (SPs), polyethylene glycol diacrylate (PEGDA), and ethanol. The influences of refractivity difference, volume fractions, and particle dimension on FWHM were illuminated. Firstly, we clarified the influences of the planar interface and the bending interface on the self-assembly. The CCs had been successfully fabricated on the planar interface and presented unfavorable results on the bending interface. Secondly, a hard sphere system consisting of SPs, PEGDA, and ethanol was established, and the entropy-driven phase transition mechanism of a polydisperse system was expounded. The FWHM and reflectivity of CCs showed an increasing trend with increasing temperature. Consequently, high-quality CCs were obtained by adjusting temperatures (ordered structure formed at 90 °C and solidified at 0 °C) based on the surface phase rule of the system. We acquired a profound understanding of the principle and process of self-assembly, which is significant for preparation and application of CCs such as optical filters.
Highlights
Yablonovitch and John have proposed a kind of material with a periodic dielectric structure—photonic crystals (PCs) [1,2]—whose enormous influence is comparable to that of semiconductor technology
The particle dimensions of the silica particles (SPs) were characterized by scanning electron microscopy (SEM), the crystalline state was determined by XRD, and the surface group was examined by the Brook infrared spectrometer
A hard sphere system was established using a fixed proportional three-component system composed by SPs, polyethylene glycol diacrylate (PEGDA), and ethanol to produce colloidal crystals (CCs) based on self-assembly behavior of the soft matter
Summary
Yablonovitch and John have proposed a kind of material with a periodic dielectric structure—photonic crystals (PCs) [1,2]—whose enormous influence is comparable to that of semiconductor technology. The action of gravity [8,9], centrifugal force [10], pressure [11], surface tension [12,13], electric force [14], or magnetic force [15] create conditions (concentration, temperature, fluidity, uniformity, and stability over time), under which the forces of attraction prevail over the repulsive forces on average. These attractive forces could make the directional movement of mono-dispersed particles, leading to the formation of a two-dimensional or three-dimensional ordered structure of colloidal crystal (CC)
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