Fabrication of high-quality silica photonic crystals on polyester fabrics by gravitational sedimentation self-assembly

A series of monodispersed silica microspheres with favourable sphericity and different diameters in the range 180-380 nm were prepared by adjusting the concentrations of tetraethylorthosilicate, ammonia, and deionised water by the Stober method. In different self-assembly conditions, the quality of silica photonic crystals on a polyester fabric substrate was investigated by field-emission scanning electron microscopy for the morphology of the crystal structures and by spectrometry for their stop band intensities. High-quality silica photonic crystals with a face-centred cubic (fcc) array on polyester fabrics were produced at a low evaporation rate by adopting a high-relative-humidity controlled condition with a medium mass fraction of colloidal silica, and exhibited brilliant and variable structural colours, depending on the photonic band gap regulated by the spherical size of the silica microspheres and the viewing angles.