Artificially Engineered Nonlinear Circular Dichroism with Chiral Nanoscrolling of 2D Materials

Nonlinear chiroptical response, particularly nonlinear circular dichroism (CD), holds significant potential for advancing nanotechnology, biophotonics, and molecular imaging. While conventional approaches rely on intrinsic chiral materials, we demonstrate a novel strategy to engineer this effect by transforming achiral two-dimensional (2D) transition-metal dichalcogenides (TMDs) into chiral nanostructures. By scrolling monolayer TMDs into geometrically chiral nanoscrolls, we achieve pronounced nonlinear CD (up to 0.8), evidenced by circular-polarization-dependent second-harmonic generation (SHG). Notably, the SHG-CD degree is tailored by controlling the nanoscrolls' scrolling axes, demonstrating, for the first time, programmable chirality-dependent nonlinear responses in TMD nanoscrolls. Furthermore, the confined electromagnetic fields within the scrolled geometry amplify the SHG intensity by up to 100-fold compared to monolayers. This chiral nanoscrolling is anticipated to enable innovative functionalities in the realm of compact nonlinear light sources and modulators, heralding a new era of advanced photonic applications.