Chiral mesostructured In2O3 films twisted along different crystal orientations

Abstract

Chiral mesostructured In₂O₃ films (CMIFs) composed of nanoflakes with exposed facets of (300) and (104) (referred to as CMIFs-300 and CMIFs-104) were synthesized using a malic acid (Mal)-assisted hydrothermal method, with or without the addition of trisodium citrate dihydrate as the structure directing agent. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations suggest that the asymmetric displacement of In and O atoms generated by the chemical bonding of Mal on the crystal plane of as-prepared InOOH is the geometric basis for triggering the chiral distortion in the In₂O₃ crystal lattice and further hierarchical chirality in the CMIFs. After adding Na₃C₆H₅O₇·2H₂O, the preferential adsorption facet of Mal on InOOH crystal transforms from (0001) to (100) due to the stronger interaction between the Na₃C₆H₅O₇·2H₂O and the (0001) plane, arising from its multiple carboxyl groups. This results in different helical axes of nanoflakes in CMIFs-104 and CMIFs-300. Both CMIFs-104 and CMIFs-300 exhibit spin chiral anisotropy (SChA), with the manifestation of external magnetic field-independent but chirality-dependent asymmetric magnetic circular dichroism (MCD) due to the dominant contribution from chirality-induced effective magnetic fields when electrons move in a helical potential.