Optical and luminescence properties of pure, iron-doped, and glucose capped ZnO nanoparticles

Pure, iron-doped, and glucose capped ZnO nanoparticles (NPs) have been synthesized by a chemical precipitation method. The structural, optical, and photoluminescence properties of all the prepared samples are examined systematically. X-ray diffraction patterns of all the samples exhibited a single hexagonal wurtzite structure with an average crystallite size ranging from 1.01 to 1.78 nm. Transmission electron microscope images showed the spherical shaped NPs in the range of between 17 and 19 nm. Fourier transform of infrared spectroscopy (FTIR) studies confirmed the presence of octahedral sites around 470-489 cm(-1) and tetrahedral sites at 616 cm(-1) in pristine and doped samples. The calculated optical bandgap energy for pure, Fe doped and glucose capped ZnO NPs are found to be 3.82, 3.80, and 3.63 eV, respectively, and the variations in the bandgap is ascribed to the Fermi level, which is in the conduction band resulting in the absorption edge shifting towards the higher/lower energy. It is observed that Fe doped and glucose capped ZnO NPs showed a strong photoluminescence signal than the pure ZnO NPs. The green emission is quenched. The blue emission is enhanced due to the deactivation of oxygen vacancies on the surfaces due to the smaller particle sizes as a result of the quantum confinement effect.