Circular dichroism and enantio-selective catalytic effect of copper sulfide

Abstract

Chiral inorganic nanomaterials provide a platform for a variety of applications. Chiral ligands are commonly used to induce chiroptical activity of nanoparticles through chiral transfer, while few materials have intrinsic chirality and the origins of their chirality are unclear as well. Here, several hexagonal copper sulfide (CuS) structures with achiral morphology which showed negative circular dichroism (CD) signals are reported. Although these CuS structures had variable maximum of anisotropic g-factor, the wavelength dependence of g-factor due to the structure-dependent chiroptical activity were similar for all these CuS structures, indicating that the negative CD activity could derive from some common microstructure in CuS. The simulation based on density functional theory (DFT) and time-dependent DFT (TDDFT) revealed that the CD may originate from (Cu3S3)2 nanostructure existing in hexagonal CuS. The enantio-selective catalysis of these homochiral CuS structure for oxidation of d-DOPA and l-DOPA was also investigated. All samples exhibited preferential catalysis of l-DOPA, which is conducive to distinguishing l-DOPA from d-DOPA. This work not only reveals the origin of CD in CuS inorganic structures with achiral morphology for the first time, but also provides a profound insight of applications of homochiral CuS structures in catalysis.