Circularly Polarized Luminescence from Silicon QDs in the Near-Infrared with Chiral Ligands

Circularly polarized luminescence (CPL) from quantum dots (QDs) is interesting for quantum optics, spintronics, and chiral photonics. We report CPL from Si QDs covalently functionalized via vinyl or acetylene linkers with structurally chiral binaphthyl-based ligands, investigating the interplay between binding geometry, surface structure, and chiroptical response. Circular dichroism (CD) spectroscopy reveals that monodentate ligands do not induce chiral transitions associated with the QD, indicating ineffective chirality transfer. In contrast, bidentate vinyl-bridged ligands induce clear, mirror-image CD and circularly polarized luminescence (CPL) signals associated with electronic transitions from the QD, confirming successful chirality transfer. ATR-IR spectroscopy shows that these chiral binaphthyl ligands transition from bidentate to monodentate binding with increasing surface coverage, correlating with a nonmonotonic trend in electronic absorption and bandedge emission dissymmetry factors, g_abs and g_lum with maxima at 2.34 × 10^-3 and 8.87 × 10^-4 respectively which peak at ∼3 ligands per QD. High-resolution transmission electron microscopy reveals that ligand binding induces lattice compression in the QDs, likely associated with chirality. These findings highlight the crucial role of ligand binding geometry and surface-induced structural distortion in generating chiroptical activity in Si QDs for next-generation chiral nanomaterials.