Occurrence of structural color by assembling single-particle layers of organo-modified nanodiamond

Structural color was realized for the first time by using organo-modified nanodiamonds with a particle size of 5 nm and by the transferring their single particle layers to the substrate as multilayers. The occurrence of various gradations of structural colors was achieved by obtaining step-like multilayers in which the thickness of assembly of the single-particle layer was changed stepwise. It was found that the occurrence of structural color by organomodified inorganic nanoparticles requires densification of particle packing in the plane by a process of twodimensional particle integration. As a two-dimensional particle integration process, the method of "repeating compression-expansion" at the air/water interface was effective. In addition, the color tone of each layer was systematically changed by annealing the organo-modified nanodiamond multilayers. Annealing improved the layered regularity, pseudo-lattice distortion, and crystallite size; however, the direct cause of the color phase change was expected to be the uniformity of the mesoscopic particle layer thickness accompanied by defect reduction.