Hydrothermal synthesis and characterization of carbon spheres using citric-acid-catalyzed carbonization of starch

The synthesis of well-dispersed carbon spheres using starch as a carbon source, citric acid as a catalyst, and distilled water as a medium without involving any organic solvent at 120-150 degrees C for 16 h under hydrothermal treatment is presented. The use of citric acid promoted starch dehydration and allowed the use of a lower hydrolysis temperature. Under similar conditions the formation of carbon spheres was not possible in the absence of citric acid. We noticed the significant effect of temperature on the particle size and shape. The particle size increased with the increase in temperature. The synthesized carbon spheres were characterized using field-emission scanning electron microscope (FE-SEM), scanning electron microscope (SEM), X-ray diffraction, Fourier-transform infrared (FTIR) and Raman spectroscopy.