Theoretical calculation of optical absorption property of Cu@Ag core–shell composite nanoparticle

Abstract

Because of their unique surface plasmon resonance (SPR) absorption in the visible region of the electromagnetic (EM) wavelength, plasmonic nanoparticles (NPs) such as gold (Au), silver (Ag) and copper (Cu) are utilized to combine with another material in devices. In this work, the optical absorption property exhibited by core–shell NPs composed of Cu cores with Ag shells (Cu@Ag) was investigated by the Discrete Dipole Approximation (DDA) method. In the theoretical calculation, at first, the Ag shell thickness was fixed at 5 nm and the Cu core diameters were varied between 10 and 30 nm. Second, the Cu core size was fixed at 20 nm and the Ag shell thickness was varied from 2 nm to 10 nm. It was observed that as the size of the Cu core increased with a fixed Ag shell thickness, the absorption peak gradually shifted to that of the pure Cu peaks (at ∼358 nm and ∼510 nm). On the other hand, the increasing Ag shell thickness showed the shifting of the absorption peak to the absorption peak of pure Ag NP (∼432 nm). The results revealed that varying either the Cu core size or the Ag shell thickness could result in obtaining tuneable light absorption. Such typical nanomaterials are expected to find application in future medical, solar cell and novel functional devices.