Structure determination in a new type of amorphous molecular solids with different nonlinear optical properties: a...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Organotetrel chalcogenide clusters, specifically adamantane-like {Sn4S6} cores with organic ligands (R), form amorphous molecular solids.
• These materials exhibit significant nonlinear optical (NLO) properties, including frequency doubling and white light emission.

Purpose of the Study:

• To investigate the microscopic and mesoscopic structural differences between two {Sn4S6}-based amorphous solids.
• To correlate these structural variations with their distinct nonlinear optical responses (frequency doubling vs. white light emission).

Main Methods:

• X-ray scattering (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy.
• Molecular Reverse Monte Carlo (RMC) simulations.
• Transmission electron microscopy (TEM) and scanning precession electron diffraction (SPED).

Main Results:

• The white light emitting material ({R=phenyl}) shows close {Sn4S6} core-to-core distances and molecular distortions.
• The frequency-doubling material ({R=naphthyl}) exhibits undistorted molecules and larger core distances.
• SPED revealed nanocrystalline structures within the amorphous matrix of the white light emitter, correlating with suppressed emission.

Conclusions:

• Microscopic and mesoscopic structural features significantly influence the NLO properties of {Sn4S6} amorphous solids.
• Molecular distortions and proximity of {Sn4S6} cores are linked to white light emission.
• The presence of nanocrystallites in the amorphous matrix is identified as the reason for the suppression of white light emission.