Chiral selectivity in lithium niobate crystals: investigating the role of l- and d-alanine as chiral inducers†

Abstract

Lithium niobate is an achiral crystal that intriguingly exhibits chiral selectivity, as well as properties typically associated with chiral crystals such as nonlinear polarization and piezoelectricity. Here, we explore L-alanine and D-alanine as chiral inducers during the hydrothermal synthesis of LiNbO₃ nanocrystals. Structural and morphological analyses using X-ray diffraction, Fourier-transform infrared spectroscopy, high-resolution scanning electron microscopy, and transmission electron microscopy reveal clear differences between pristine and induced crystals. Low-frequency Raman and circular dichroism spectroscopy, high-performance liquid chromatography, and isothermal titration calorimetry were employed to investigate the chirality and enantiomeric selectivity. L-Ala-induced LiNbO₃ crystals preferentially adsorbed L-enantiomers, while D-Ala-induced crystals favored D-enantiomers. This study sheds light on the mechanisms of chiral induction in inorganic crystals, highlighting the potential of LiNbO₃ for chiral sensing, enantioselective catalysis and biomolecular recognition.