Combustion synthesis of Al-doped ZnO nanoparticles using a new fuel and the study of its structural, micro-structural and optical properties

Present work reports the synthesis of Al-doped ZnO nanoparticle by solution combustion method using Leucine as a fuel for the first time. As-synthesized powder samples were extensively studied through XRD, SEM–EDS, FTIR and UV–visible spectroscopy to evaluate the effect of fuel and Al doping on the structural and optical properties. Structural findings demonstrate the formation of polycrystalline, single-phase and nanosized particles attributable to the exothermicity of the oxidizer–fuel redox mixture. The structural parameters were found to be decreasing with Al concentration. SEM micrographs reveal the agglomeration of particles, presence of pores, voids and the formation of nanorods at higher Al concentration of the sample. Good agreement of elemental composition is found in EDS spectra of the synthesized samples. FTIR spectra reveals a strong Zn–O stretching vibrational bond results in the strong absorption which further increases with Al concentration. The energy bandgap is found to be redshifted with Al concentration, which is due to the association of sp–d exchange between the localized d electrons and delocalised sp conduction electrons. In addition, as Al is inserted into the ZnO host matrix, the estimated Urbach energy values are observed to increase, suggesting increased structural disorder. The structural and optical findings obtained show that the prepared nanoparticles could be used for various future opto-electronic applications.