Simultaneous Measurement of Circular Dichroism and Circular Differential Scattering

Abstract: Chiroptical spectroscopy provides a non-invasive, label-free approach for resolving microscopic structural details via interactions with circularly polarized light. Despite the widespread application and complementary information provided for chiroptical materials characterization, the simultaneous acquisition of circular dichroism (CD) and circular differential scattering (CDS) spectra has remained challenging. In this work, we develop a dual-channel spectrometer that enables the acquisition of CD and CDS spectra from the same solution. To address the challenge of CDS baseline correction, we introduce a scattering spectral matching method. The performance of the instrument is validated using two representative model systems: a mixture of ammonium d-10 camphor sulfonate and polystyrene nanoparticles (PSNPs), and plasmonic gold helicoid nanoparticles, which exhibit both chiral absorption and scattering. For the former case, the CDS spectra show opposite signs to the CD spectra because the PSNPs are achiral scattering particles and the CDS spectra are affected by the chiral absorption. For the latter case, both CD and CDS spectra exhibit matched resonance wavelengths and stronger responses to the right-handed circularly polarized light, indicating that the chiral absorption and scattering arise from the same plasmonic resonance modes. To the best of our knowledge, this work represents the first experimental demonstration of the concurrent acquisition of ensemble-averaged CD and CDS spectra. The presented technique enables a direct and accurate comparison of CD and CDS spectra acquired under identical conditions.