A comparative study of ZnAl2O4 nanoparticles synthesized from different aluminum salts for use as fluorescence materials.

Three ZnAl2O4 samples were prepared via a modified polyacrylamide gel method using a citric acid solution with different aluminum salt starting materials, including AlCl3 ∙ 6H2O, Al2(SO4)3 ∙ 18H2O, and Al(NO3)3 ∙ 9H2O under identical conditions. The influence of different aluminum salts on the morphologies, phase purity, and optical and fluorescence properties of the as-prepared ZnAl2O4 nanoparticles were studied. The experimental results demonstrate that the phase purity, particle size, morphology, and optical and fluorescence properties of ZnAl2O4 nanoparticles can be manipulated by the use of different aluminum salts as starting materials. The energy bandgap (Eg) values of ZnAl2O4 nanoparticles increase with a decrease in particle size. The fluorescence spectra show that a major blue emission band around 400 nm and two weaker side bands located at 410 and 445 nm are observed when the excitation wavelength is 325 nm. The ZnAl2O4 nanoparticles prepared from Al(NO3)3 ∙ 9H2O exhibit the largest emission intensity among the three ZnAl2O4 samples, followed in turn by the ZnAl2O4 nanoparticles prepared from Al2(SO4)3 ∙ 18H2O and AlCl3∙6H2O. These differences are attributed to combinational changes in Eg and the defect types of the ZnAl2O4 nanoparticles.