THz enantiomers of drugs recognized by the polarization enhancement of gold nanoparticles on an asymmetric metasurface

Abstract

Chirality plays an important role in biological processes, and enantiomers often possess similar physical properties and different physiological functions. Thus, chiral detection of enantiomers has become a hot topic in recent years, and methods to enhance chiral molecular recognition are in urgent demand. In this work, a polarization detection method was used for different chiral drugs based on a specially designed metasurface composed of asymmetric double-opened rings and the surface enhancement effect of gold nanoparticles (GNPs). The experiment results show that the frequency shifts caused by the nearfield interaction of the metasurface and biomolecules have been significantly improved by GNPs, and both the limit of detection and detection precision of the metasurface can reach the 10⁻⁵ g ml⁻¹ level. Moreover, the polarization sensing characterized by right circular polarization (RCP), the polarization elliptical angle (PEA), and the polarization rotation angle (PRA) shows that the enantiomers of three drugs can be distinguished, especially using the PEA spectrum; the maximum difference between enantiomers is over 30° with a precision of 6.6 × 10⁻⁷ g mL⁻¹. Our THz polarization sensing and the GNP enhancement method inspire an efficient strategy for the highly sensitive detection of enantiomers.