A research team led by Prof. YANG Liangbao from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences proposed an electromagnetic field enhancement mechanism based on the near neighbor electron orbit coupling effect, explaining the mechanism of two-dimensional (2D)-layered material Au-2H-TaS₂ used for surface-enhanced Raman scattering (SERS) enhancement.

The results were published in Journal of Physical Chemistry Letters.

2D materials are a hot topic in the field of analytical chemistry due to their potential as ideal metal-free substrates for SERS. However, compared to precious metals, 2D materials have a relatively low enhancement factor due to their mainly chemical enhancement mechanism. Therefore, further research is needed on the mixed metal nanoparticle 2D material or chemically doped 2D material system and its SERS enhancement mechanism in order to achieve high SERS performance.

In this study, the researchers used single-atom gold (Au) clusters to intercalate 2H-TaS₂, achieving a SERS enhancement effect of two orders of magnitude relative to the parent 2H-TaS₂.

In order to accurately elucidate the SERS enhancement mechanism of Au-2H-TaS₂, a single atomic layer Au cluster intercalation bilayer 2H-TaS₂ model was established, and an innovative electromagnetic field enhancement mechanism based on the coupling effect of neighboring electron orbitals was proposed.

Through experimental analysis and theoretical calculations, it was shown that the d-orbital electrons on the Au surface are coupled with the neighboring 2H-TaS₂, increasing the local electron density, resulting in a strong local electromagnetic field.

This work provides new insights for SERS enhancement of non-precious metal compounds and guides the development of new SERS substrates, according to the team.

SERS enhancement principle of Au-2H-TaS₂ based on the coupling effect of nearest-neighbor electron orbits. (Image by WEN Shirui)