Structural and optical properties of hematite and L-arginine/hematite nanostructures prepared by thermal spray pyrolysis

Abstract

A study of structural and optical properties of hematite and L-arginine/hematite films was carried out. Hematite films were deposited by thermal spray pyrolysis on fluorine-doped tin oxide at temperatures varying from 280 to 430 °C. X-ray diffraction results revealed (104) and (110) planes, describing the rhombohedral structure of hematite. Scanning electron microscopy on hematite films showed nanoparticles of grain sizes ranging between 40.0 ± 0.5 and 100.0 ± 0.5 nm. Hematite nanoparticles were transformed to nanospheres with uniform size of 35.0 ± 0.5 nm, using chemical bath deposition and L-arginine, a biomolecule as a structure-directing agent. Raman peaks revealed two A1g and five Eg phonon vibrational modes of hematite. Atomic force microscopy confirmed an increase in the surface root mean square roughness from 35 to 40 nm for hematite nanoparticles and L-arginine/hematite, respectively, which is desirable for charge transport. The films exhibited an indirect band gap varying from 2.08 to 2.30 eV and an onset absorbance that ranged between 525 and 560 nm. An improved current density was observed on l-arginine/hematite from pristine hematite nanostructures.