Plasmon-Enhanced Optical Chiral Molecule Detection Using Gold Nanoparticle Dimer Sensors

Chiral detection plays a crucial role in exploring the potential applications of chiral molecules in biomedicine, chemistry, and pharmaceutical industries. Gold nanoparticle dimers (GND) have unique plasmonic optical properties, offering a promising approach to enhance the sensitivity of chiral optical detection for biomolecules. Coupling these dimers with chiral molecules leads to substantial plasmon-coupled circular dichroism within the visible light spectrum. However, the plasmonic properties of these dimers are dependent on their geometric characteristics, emphasizing the critical need for selecting an effective structure to amplify the optical detection signal and develop high-sensitivity nanosensors. This study utilized the finite element method to explore how geometric factors influence the enhancement of CD in chiral molecules using typical gold nanoparticle dimer sensors. Our findings unveil the optimal radius for gold nanosphere dimers, maximizing the enhancement of CD. Additionally, we identified the optimal radius and aspect ratios for gold nanorod dimers. Furthermore, we investigated the ideal aspect ratio for gold nanobipyramid dimers, which demonstrate superior field enhancements and optical cross sections. In comparison to other nanoparticle dimers, gold nanobipyramid dimers show a 20-fold enhancement factor. Consequently, GND significantly enhance the sensitivity of chiral molecular optical detection and have resonance wavelengths at the optimal aspect ratio within the visible light range, enabling direct optical detection in practical applications. These findings offer valuable theoretical guidance for effectively utilizing gold nanoparticle dimer structures to enhance the sensitivity of chiral molecular optical detection.