Dimensionally Resolved Nanostructures of an Atomically Precise and Optically Active 1D van der Waals Helix

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Physics

Background:

• Inorganic freestanding helices are rare, with chirality imparting unique physical properties.
• III-VI-VII ternary solids are a class of 1D van der Waals (vdW) crystals with helical structures.
• Limited synthetic methods hinder understanding of intrinsic and size-dependent properties of these helical materials.

Purpose of the Study:

• To develop a bottom-up synthetic strategy for high-yield production of freestanding helical nanostructures.
• To investigate the physical properties of Gallium Sulfide Iodide (GaSI) nanostructures.
• To explore the influence of helical structure on electronic properties at the nanoscale.

Main Methods:

• A bottom-up strategy was employed to grow ultrathin nanostructures of GaSI.
• High-temperature synthesis yielded single-crystal 1D nanowires (10-100 nm thickness).
• Lower-temperature synthesis produced quasi-2D nanoribbons.

Main Results:

• High yields of ultrathin GaSI nanostructures, including nanowires and nanoribbons, were achieved.
• GaSI nanowires exhibit a UV bandgap and nonlinear optical behavior, confirming nanoscale noncentrosymmetric structure.
• First-principles calculations revealed handedness-dependent and helicity-imposed spin polarization in single GaSI helix electronic structures.

Conclusions:

• The developed synthetic strategy enables scalable production of helical GaSI nanostructures.
• Nanoscale GaSI retains its noncentrosymmetric chiral structure and exhibits unique optical properties.
• The helical nature significantly influences electronic structure, leading to spin polarization in single helices, opening avenues for spintronics.