One-step production of structured metal and associated oxidizing nanoparticles using picosecond pulse trains: a novel surface for structural color

This paper presents a novel approach to obtain the structured metal and its associated oxidizing nanoparticles for two types of structural color. The oxidation and surface structuring are governed by thermalization generated by picosecond pulse trains. To begin with, simulation findings indicated that both the layer consisting of pure TiO₂ nanoparticles and the composite structures created by the interaction of TiO₂ with picosecond laser-induced surface periodic structures on titanium (referred to as Ti LIPSSs) exhibited a similar color shift to that of the pure TiO₂ film. A consistent colorful surface across a broad angle is achieved with the TiO₂ nanoparticles covering on the textured Ti surface characterized by laser-induced microstructures. Subsequently, to achieve the deposition of TiO₂ nanoparticles on the surface of Ti LIPSSs, a pulse energy exceeding the threshold for laser-induced processing was utilized. The results indicate that the colorful surface maintains consistency at wide angles under indoor illumination, which is markedly different from that of pure Ti LIPSSs. Nonetheless, under parallel light irradiation, the surface color is only responsive to the angle of incidence. These structural colors might be employed for concealing information.