Study of products of hydrothermal treatment of oligochitosan solutions

By hydrothermal synthesis of polysaccharides porous carbon spheres of tens to thousand nanometers size and luminescent carbon nanodots of less than 10 nanometer size can be formed. Both types of carbon structures have a wide range of applications. However, the phase separation between carbon nanodots and carbon spheres during the hydrothermal treatment was not studied. In the current work, both phases formed by hydrodynamic treatment of dilute aqueous dispersions of oligochitosan were studied. The luminescence and UV/vis absorption of carbon nanodots were examined; the carbon spheres were characterized by light scattering and scanning electron microscopy. Upon increasing the duration of hydrothermal treatment, the carbonization degree of both components and the size of carbon spheres increased. For the first time, the luminescence of carbon nanodots originating from oligochitosan was shown to depend on the autoclave filling.