Preparing undoped and Mn-doped ZnO nanoparticles: a comparison between sol-gel and gel-combustion methods

Undoped and Mn doped ZnO nanoparticles were synthesized by two wet chemical techniques: sol-gel and gel-combustion. We were able to prepare Mn-doped ZnO nanoparticles free from the second phases at calcining temperatures 400 and 500 A degrees C using sol-gel and gel combustion, respectively. Complete crystallization occurs in both methods, but it is found that the crystallization is better performed in the ZnO based solid solution prepared by the sol-gel method. TEM images show that the average size of the nanoparticles synthesized by gel-combustion is smaller than that of prepared by sol-gel method. Optical characterizations such as vibrational properties, lattice dynamical parameters, absorption edges and optical band gap energies were also carried out by FTIR and UV-Vis spectroscopies. The quantitative estimations led to the conclusion that the effects of the method on the particle size and the optical band gap energy of the prepared samples are very significant.