Magnetic Circular Dichroism of Chiral Quantum Rods

Abstract

Circular dichroism (CD) and magnetic circular dichroism (MCD) are two distinct spectroscopic techniques that offer valuable insights into the properties of materials. Generally speaking, CD spectroscopy reveals information about the ground electronic states of chiral materials, while MCD spectroscopy is sensitive to the degeneracy splitting of energy states in achiral materials under an applied magnetic field. For typical chiral molecules, the measurement of their MCD spectra invariably involves an intrinsic CD signal, which arises from their chiral structure. Consequently, the MCD spectrum can be dissected into two components: one is the CD spectrum arising from the asymmetry of the geometric structure inherent to the chiral molecules; the other is the MCD spectrum associated with the corresponding racemic mixtures. This principle of spectral decomposition is well-established in molecular systems; however, a natural question arises: what is the situation like in inorganic nanosystems? To address this query, an in-depth analysis was conducted of the MCD spectra of chiral quantum rods (QRs) with the same diameter but varying lengths. Intriguingly, it was discovered that the analytical approach applicable to chiral molecules can also be extended to chiral quantum rods (QRs), especially when chiral molecules are present on the surfaces of these materials. This finding holds great significance, as it paves the way for a more accurate and comprehensive MCD analysis of inorganic nanoparticles, potentially enabling new insights and applications in nanomaterials research.