Abstract:

Photonic crystals (PCs) are a kind of nanostructure with periodically varying refraction rates, which contain photonic band gaps that can regulate the propagation of light. PCs show beautiful structural colors if the band gaps occur in the visible light band. Due to their unique optical features, PCs have a wide range of applications, such as those in photoelectric material, chemical sensors, and ink-free printing. We introduced the frontier scientific field to the undergraduates. Using the improved Stöber method, we synthesized diameter-controllable monodisperse silica nanoparticles. As a simple and rapid method to obtain a thin layer, drop-coating is innovatively used here to assemble PCs. This experiment can be completed in 4 h. The method is inexpensive, and it helps students understand significant phenomena with interest. As a result, students can consolidate their experimental skills and learn nano-chemistry and colloidal self-assembly. The experiment is related to structural chemistry and optics theories. By integrating these theories, students can understand how structural colors are generated.

Key words: Photonic crystals, St?ber method, Drop-coating, Colloidal self-assembly, Structural color