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Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry
Published on: March 4, 2021
Unoccupied electronic structure of ball-milled graphite
Adriyan S Milev1, Nguyen H Tran, G S Kamali Kannangara
1School of Natural Sciences, University of Western Sydney, Penrith South, DC NSW 1797, Australia. a.milev@uws.edu.au
Physical Chemistry Chemical Physics : PCCP
|April 27, 2010
Summary
Planetary ball-milling transforms macrocrystalline graphite into nanographite, altering its electronic and vibrational structures. New spectral features indicate zigzag edges and sp(3) hybridization, suggesting defect manipulation can tune electronic properties.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Grinding macrocrystalline graphite using a planetary ball-mill induces significant structural modifications.
- Understanding these changes is crucial for tailoring nanographite properties for advanced applications.
Purpose of the Study:
- To investigate the electronic and vibrational structure changes in graphite upon milling.
- To correlate spectral modifications with crystallite size reduction and defect formation.
Main Methods:
- Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the C K-edge using Total Fluorescence Yield (TFY) and Partial Electron Yield (PEY) detection modes.
- Raman spectroscopy to analyze vibrational modes.
Main Results:
- Milling reduced crystallite size from ~160 nm to ~9 nm.
- NEXAFS TFY revealed a new feature at 284.1 eV (zigzag edges) and a 0.4 eV shift in the pi* band (285.5 to 285.9 eV) due to conjugation breaking.
- NEXAFS also showed features at 287.5 and 288.6 eV, indicating a shift from sp(2) to sp(3) hybridization.
- Raman spectroscopy showed an up-shift of the G band from 1575 to 1583 cm⁻¹.
Conclusions:
- Milling introduces defects and modifies the sub-surface electronic structure of graphite.
- The observed spectral changes, particularly the new edge feature and hybridization shifts, are direct consequences of mechanical processing.
- Defect engineering in nanographite offers a pathway to control its electronic transport properties.
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