Influence of Combustion Temperature of the Chelating-Fuel Agent on the Morphology of ZnCr2O4 nanoparticles

Zinc chromite nanoparticles are a material with a wide range of properties from catalytic to semiconductor, which find practical application in the fields of catalysis, electronics, sensorics, medicine, etc. The main properties of nanoparticles directly depend from structure, size and shape of each particles. In turn, one of the key factors for varying the properties of the nanomaterials is changes of nanoparticles morphology that can be carried out by thermal action. In this paper, the influence of the combustion temperature during the sol-gel syntheses of chelating-fuel agents on the size, size distribution and structural formation of zinc chromite nanoparticles was studied. Tartaric acid with combustion temperature 505 °C and hexamethylenetetramine with combustion temperature 1100 °C were used as chelating-fuel agents. By transmission electron microscopy the morphology of samples was studied. It was found that tartaric acid allow the formation of ZnCr2O4 nanoparticles with nearly the same morphology and size of about 30-55 nm with exception for a few bigger particles. Found shapes of the obtained nanoparticles by tartaric acid are close to cubic and cubic truncated. From the histogram of sizes it was found that the dominant formed number of nanoparticles is obtained with a size of about 50 nm. In return, hexamethylenetetramine as chelating-fuel agent provokes the formation of nanoparticles with about 50-100 nm in size and none uniform morphology. By X-ray diffraction analysis (XRD) and Fourier transform infrared analysis (FT-IR) were confirmed that all synthesized nanoparticles were obtained with a pure spinel structure. In detail, it was not found the rest of organic compound after burning of the combustion agents and it was not detected any other crystalline compound (ZnO or Cr2O3) during the FT-IR and XRD analyses. Thus, summarizing that tartaric acid as a chelating-fuel agent is a more promising compound in terms of ZnCr2O4 nanoparticles synthesis with approximately uniform morphology. In particular, the optimal conditions for the synthesis of ZnCr2O4 nanoparticles are reported.