Preparation of SiO₂ microspheres and their structural coloration on wood surface

  Objective  In order to enrich the color system of wood products, this paper discusses the construction and color performance of SiO₂ photonic crystals on the surface of wood.

  Method  In this paper, SiO₂ microspheres with different particle diameters were prepared by the Stöber method, and the SiO₂ photonic crystal structure color was constructed on the wood substrate by the gravity deposition self-assembly method. The chemical composition and structure of SiO₂ microspheres were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The morphology of the microspheres and their arrangement on the wood substrate were characterized by scanning electron microscopy, and the particle diameter distribution of the microspheres under different treatment processes was analyzed. The color parameters and UV-visible reflectance of SiO₂ structure on the wood surface were analyzed by digital camera and UV-visible absorption spectrometer.

  Result  X-ray diffraction, Fourier transform infrared spectroscopy confirmed that the reaction products prepared in this paper were pure amorphous SiO₂, suitable for constructing well-colored structural color coating. The preparation formula only controlled the amount of ethanol added, and the addition amount was 80, 85, 90, 95, 100, and 105 mL, respectively. The monodisperse nano-SiO₂ was generated, and their particle diameters were 294, 246, 226, 214, 194, and 181 nm, respectively. As the particle diameter of SiO₂ involved in self-assembly decreased in turn, the color of the film gradually changed from red to green, blue-green, and finally to deep purple, purple, and lavender. The ultraviolet reflection wavelength gradually decreased and the color blue shifted. The SiO₂ microspheres showed a three-dimensional ordered face-centered cubic structure on the surface of the wood substrate. Due to environmental disturbances, assembly defects such as cracks and missing will occur, but will not affect the overall color.

  Conclusion   Only by controlling the amount of ethanol added, six different particle diameters of nano-SiO₂ particles suitable for constructing photonic crystal structure color can be prepared. Silica microspheres of various particle diameters formed bright structural colors after self-assembly on the wood substrate, and the color of the structural color coating would blue shift due to the particle diameter reduction of the self-assembled microspheres. The above research content provides a simple and novel method for the large-scale preparation of wood surface structural color coatings, which can enrich the color system of wood products.