“…Photonic crystal devices defined as periodic nanostructures of dielectric materials with different refractive indices, [ 23,27 ] particularly 3D PC devices, [ 28 ] promising complete control over the photons emission and transmission in space due to the complete photonic bandgaps attributed to their periodic nanostructures. [ 11,20,29,30 ] Although most emergency applications take advantage of light reflection properties in fundamental sciences (Related to reflective coatings on lenses, [ 31,32 ] sensors, [ 33–35 ] color pigments in paints and inks, [ 36,37 ] energy management, [ 38–40 ] waveguides for directing the propagation of light along a specific path, [ 41,42 ] highly reflective mirrors in laser cavities, [ 43,44 ] and many other optical components), and here in order to obtain high transparency, we subtly control the optical bandgap beyond visible light by controlling the size of the PC nanospheres. As shown in Figure a, the optical properties of transparent optical devices can be described by Bragg's law, as shown in the following equations, [ 45,46 ] where d is the distance between two neighboring crystalline planes in the (111) direction for a face‐centered cubic (fcc) close‐packed structure, and its relation with the sphere diameter D is shown in Equation ().…”