Effect of nitrogen and oxygen in the formation of graphitic structures from pyrolysis of amino acids at high pressures

- Pyrolisis of amino acids under high pressure produced disordered graphitic structures.
- Product of pyrolisis under high pressure depends on the (N + O)/C ratio of the amino acids.
- Pyrolisis of L-alanine at 1100 °C and 2.5 GPa during 1 min produced spheres of ∼3 μm diameter.
- Degree of crystallinity of the graphitic structures strongly depended on the (N + O)/C ratio.
- Raman and infrared spectra of the pyrolisis of amino acids under high pressure revealed poor graphitization.

This paper presents an experimental study about the structural modifications of aminoacids L-leucine (C6H13NO2), L-alanine (C3H7NO2), L-aspartic acid (C4H7NO4) and glycine (C2H5NO2) after processing at high pressure and high temperature. Experiments were performed at 2.5 and 7.7 GPa at 1100 °C during 1 min, leading to the formation of graphitic structures with low degree of crystallinity. Evidences from Raman and infrared spectroscopy, X-ray diffraction, elemental analysis (CHN) and scanning electron microscopy (SEM) suggested that the resulting graphitic nanostructures depended on the initial concentration of nitrogen and oxygen of the starting samples. The results were compared to the behavior of paraffin, which does not contain nitrogen and oxygen atoms, and 5-Azacytosine (C3H4N4O), containing nitrogen and oxygen but in a cyclic structure.