Spectral analysis of oxidation on localized surface plasmon resonance of copper nanoparticles thin film

Zhonghua Liu; Bin Xu; Yuqing Cheng; Mengting Si; Xiangqian Chu; Mengtao Sun; Yingcui Fang

doi:10.1016/j.saa.2023.123202

Spectral analysis of oxidation on localized surface plasmon resonance of copper nanoparticles thin film

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Dec 15:303:123202. doi: 10.1016/j.saa.2023.123202. Epub 2023 Jul 27.

Authors

Zhonghua Liu¹, Bin Xu¹, Yuqing Cheng², Mengting Si³, Xiangqian Chu¹, Mengtao Sun⁴, Yingcui Fang⁵

Affiliations

¹ Department of Vacuum Science and Technology, Hefei University of Technology, Hefei 230009, China.
² School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China.
³ School of Physics, Peking University, Beijing 100083, China.
⁴ School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China. Electronic address: mengtaosun@ustb.edu.cn.
⁵ Department of Vacuum Science and Technology, Hefei University of Technology, Hefei 230009, China. Electronic address: ycfang@hfut.edu.cn.

PMID: 37531684
DOI: 10.1016/j.saa.2023.123202

Abstract

Copper nanoparticles (CuNPs) possess localized surface plasmon resonance (LSPR) effect. Cu thin films composed of individual CuNPs exhibit stronger LSPR than the individual CuNPs due to the LSPR coupling among CuNPs. However, CuNPs are easy to be oxidized, which results in the rapid LSPR damping of the CuNPs thin films. Simulation of the variations of the coupled LSPR of two adjacent CuNPs with the thickness of oxide shells formed during oxidation is of great importance for understanding the mechanisms of the strong LSPR of CuNPs thin films and its rapid attenuation. In this paper, Discrete-dipole approximation method is used to simulate the extinction spectra of two adjacent spherical CuNPs as a function of the shell thickness (t), the ambient refractive index (n), the diameter (D) of the CuNPs, and the inter-nanoparticle spacing (L). The calculation is validated by experimental results. According to our model, for a definite CuNPs thin films, the oxide shell thickness of CuNPs can be calculated only if the extinction spectra and the morphology are provided. Further, it is found when the oxide shell thickness is small (t/R< 0.3), increasing n and decreasing L/D have an obvious synergistic effect on enhancing the coupled LSPR, but this synergistic effect weakens with the deepening of oxidation, and disappeared when t/R > 0.5. This study provides a calculation method for coupled core-shell nanoparticles and throws light on the role of oxidation on the rapid damped LSPR of CuNPs thin films.

Keywords: Copper thin film; Localized surface plasmon resonance; Nanoparticles; Oxidation; Spectral analysis.