Angle-Dependent and Liquid-Responsive Photonic Crystals for Anti-Counterfeiting and Optical Sensing

More and more attention has been attracted by the structural color recently, which is attributed to its superiority of being eco-friendly and excellent color fastness. As a type of structural color material, the construction of photonic crystals (PCs) has become mature. However, there are still some problems that limit its applicability, such as the low color saturation and complicated process. Herein, a multi-step dropwise addition of precursor is adopted to achieve controllable preparation of monodispersed nano-silica and quick-dry SiO 2 PCs with heterochromatic characteristics from different angles are constructed. Inspired by the wing scales of Parides Sesostris butterfly, static deposition and layering method is proposed to fabricate SiO 2 PCs with biomimetic structure. The SiO 2 suspension is left standing for 72 hours to remove the supernatant, then self-assembly of the SiO 2 sediment is carried out. It can be found that the SiO 2 PCs assembled at the dish bottom are brightly colored with angle-dependence while the SiO 2 PCs assembled on the dish wall are liquid-responsive with good reversibility and recyclability. Therefore, a simple and rapid method for the preparation of angle-dependent and liquid-responsive SiO 2 PCs is provided. This will broaden applications of PCs in anti-counterfeiting, holographic displaying, information encryption, liquid/optical sensing, et al.