Structurally colored silica photonic crystal coatings modified by Ce or Eu rare-earth dopants

Recently three-dimensional photonic crystal (PC) materials with inverse opal morphology are very popular due to their high application capacity. The structural color that is one of these popular application areas attracts attention with fadeless bright color, low toxicity and eco-friendly features. With this respect, silica based inverse opal photonic crystals were deposited on borosilicate glass substrates and the effect of the cerium (Ce) and europium (Eu) dopants on the properties of these coatings were investigated in detail. Thermal, structural and physical properties were characterized via differential thermal analysis (DTA-TGA), x-ray photoelectron spectroscopy (XPS), x-ray diffractometer (XRD), scanning electron microscope (SEM), UV spectrophotometer (UV–vis) and optical microscope (OM), respectively. The results reveal that the ordered porous honeycomb like morphology surrounds the entire 3-D structure. Periodically ordered photonic crystal morphologies are achieved at the coatings with the lowest dopant ratios. SiO₂ based PC coatings possess blue and purple structural colors. It was found that the photonic band gap value was red-shifted by Ce doping in the coating while blue-shifting by Eu doping.