C60 aggregate structure and geometry in nonpolar o-xylene
Alok D Bokare1, Archita Patnaik
1Department of Chemistry, Indian Institute of Technology Madras, Chennai-600036, India.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Fullerenes form stable colloidal aggregates in o-xylene, changing shape with concentration. Positronium probes reveal microcrystal structures in these C(60) fullerene aggregates.
Area of Science:
- Materials Science
- Physical Chemistry
- Nanotechnology
Background:
- Previous studies investigated C(60) colloidal aggregates in CS(2) and their electron density.
- Understanding fullerene aggregation in different solvents is crucial for materials applications.
Purpose of the Study:
- To investigate the solution-phase structure of C(60) fullerene in nonpolar o-xylene.
- To map changes in local electron density and aggregate morphology using a positronium probe.
Main Methods:
- Utilized positronium (Ps) atom as a probe for local electron density.
- Observed aggregate formation and stability across a concentration range (0.14-0.36 g/dm³).
- Employed pyrene fluorescence quenching to confirm aggregation onset.
- Analyzed aggregate geometry changes using transmission electron microscopy (TEM).
Main Results:
- Stable C(60) colloidal aggregates (90-150 nm) formed in o-xylene above 0.14 g/dm³.
- Aggregate formation onset (0.14 g/dm³) differs from that in CS₂ (0.06 g/dm³).
- Observed a sphere-to-nonuniform cylinder transition in aggregate geometry with increasing concentration.
- TEM and Ps annihilation data indicated hexagonally close-packed microcrystal structures.
Conclusions:
- C(60) fullerene forms stable, hexagonally close-packed microcrystalline aggregates in o-xylene.
- Aggregate morphology is concentration-dependent and influenced by solvent interactions.
- Positronium probing provides insights into the microenvironment of fullerene aggregates.
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