Tailorable and Angle-Independent Colors from Synthetic Brochosomes.

Although various artificial dyes and pigments have been invented, certain application fields need structural colors because they can last for centuries even under harsh conditions. Here, we report that the antireflective Ag brochosomes (soccer-ball-like microscale granules covered by nanobowls) become colorful when the nanobowls on the Ag brochosomes are filled by polystyrene (PS) nanospheres. The color originates from the enhanced electromagnetic resonances of the PS nanospheres by the surrounding metallic nanobowls, suggested by both the experimental and the simulation results. The color is determined by the size of the PS nanospheres. We can tailor the color simply by reducing the diameter of the PS nanospheres via the plasma etching treatment. The color intensity of the Ag brochosomes filled with PS nanospheres shows weak dependence on the observing angles, benefiting from their spherical shape. Plasma etching treatment of the Ag brochosomes filled with PS nanospheres through different masks can design various structural color patterns. The simple fabrication process and the easy processability make the Ag brochosomes filled with PS nanospheres have promising applications in the structural color fields.