Enhanced Reflective Interference Spectra of Nanoporous Anodic Alumina Films by Double Electrochemical Deposition of Chemical Metal Nanoparticles

Abstract

The effect of selective color reflection enhancement from a double metalized nanoporous anodic alumina (NAA) film surface under proper conditions of electrochemical and chemical metal (Cu—Ag, Cu—Au) deposition has been observed. Selective coloration of the NAA films with high index of the reflection and wide range of the color tones was achieved. The additional chemical deposition of the noble metal leads to the enhancement of the selective reflection ability and the interference contrast of the reflected light. The distribution of the chemically deposited silver nanoparticles on the top surface of electrochemically copper metalized pores of anodized aluminum has been shown by the electron microscopy method. The optical reflection spectra at different angles (10°-85°) of metalized NAA film have been measured, and the effective index of refraction (n ≈ 1.6) and film thickness have been calculated. The effect of the reflected light interference contrast enhancement has been explained as being a result of the more effective separation of the two reflecting surfaces air/Al₂O₃ in the structure of the film similar to a Fabry-Pérot interferometer.