Synthesis and properties of iridescent Ni–Co composite photonic crystal films by pulse anodization

Abstract

A thin film material, composed of Ni–Co alloy and photonic crystal, is presented in this paper. It not only has good magnetic properties but also shows bright structural color. Alternating current (AC) electrodeposition is used to prepare this composite film in a porous anodic alumina photonic crystal template. It was found that with the increase of the Co content in the deposition solution, the coercivity of the Ni–Co alloy nanorods prepared at the same deposition time first decreases and then increases, the maximum coercivity value is about 1370 Oe. The XRD results show that the Co (002) diffraction peak disappears and a new Co (100) diffraction peak appears as the Co content increases. PPMS results show that the magnetic properties of the Ni–Co alloy nanorods were enhanced due to the decrease of the pore diameter of the photonic crystal template. This happened because the aspect ratio became larger, which is consistent with the uniform rotation mechanism. The results also indicate that the pore size of the photonic crystal template is proportional to the immersion time in the deposition solution. Therefore, the structural color of the composite film has a red shift with the growth of the pore widening time. With good magnetic behavior and the stable structural color, this Ni–Co composite photonic crystal film can be applied in the field of anti-counterfeiting.