Synthesis and Characterization of Two Green Nano pigments Based on Chromium Oxide

Green nano pigments of Cr2O3 and CoCr2O4 were successfully prepared by polyol method followed by calcination at 770°C. The Cr2O3 and CoCr2O4 samples were characterized by X-ray diffraction XRD, scanning electron microscopy SEM, diffuse reflectance spectroscopy DRS, dynamic light scattering DLS, UV–Vis spectroscopy and CIE-Lab colorimetry methods. Dynamic light scattering analysis confirmed the formation of nanoparticles in suspensions. XRD data of Cr2O3 and CoCr2O4 powders displayed the formation of crystallized rhombohedral and spinel structures, respectively. The average crystallite size of Cr2O3 and CoCr2O4 are calculated ~54 and 39 nm, respectively. The SEM results showed the average size of Cr2O3 and CoCr2O4 nano pigments is about 70-80 nm, while CoCr2O4 nano pigments were more agglomerated than Cr2O3. The calorimetric and DRS data confirmed the formation of green pigments in both samples.