Single-molecule nanoprobes explore defects in spin-grown crystals.

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Single crystals of p-terphenyl (PT) doped with terrylene impurity molecules are prepared via spin-coating.
• Observing molecular motion within solid-state materials is crucial for understanding their properties.

Purpose of the Study:

• To investigate the dynamics of individual terrylene molecules within p-terphenyl single crystals.
• To utilize single-molecule fluorescence imaging to probe internal crystal structures and defects.

Main Methods:

• Spin-coating technique for crystal preparation.
• Single-molecule fluorescence imaging at room temperature.
• Single-particle tracking and correlation analysis.

Main Results:

• Individual terrylene molecules were observed moving micrometers within the crystal.
• Molecular motion revealed long, thin, crack-like defects with correlated orientations.
• Three distinct terrylene populations were identified: traveling, fixed (c-axis dipole), and fixed (other orientation).
• Traveling molecules exhibited photobleaching in ~32 s, while fixed populations showed much longer or shorter photobleaching times.

Conclusions:

• Terrylene molecules serve as effective nanoprobes for exploring internal crystal defects.
• The observed molecular motion highlights the presence of accessible internal pathways within the crystal.
• The study demonstrates a novel method for visualizing sub-micrometer defects in crystalline materials.