A comparative study of ZnAl(2)O(4) nanoparticles synthesized from different aluminum salts for use as fluorescence materials

Three ZnAl(2)O(4) samples were prepared via a modified polyacrylamide gel method using a citric acid solution with different aluminum salt starting materials, including AlCl(3)∙6H(2)O, Al(2)(SO(4))(3)∙18H(2)O, and Al(NO(3))(3)∙9H(2)O under identical conditions. The influence of different aluminum salts on the morphologies, phase purity, and optical and fluorescence properties of the as-prepared ZnAl(2)O(4) nanoparticles were studied. The experimental results demonstrate that the phase purity, particle size, morphology, and optical and fluorescence properties of ZnAl(2)O(4) nanoparticles can be manipulated by the use of different aluminum salts as starting materials. The energy bandgap (Eg) values of ZnAl(2)O(4) 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 ZnAl(2)O(4) nanoparticles prepared from Al(NO(3))(3)∙9H(2)O exhibit the largest emission intensity among the three ZnAl(2)O(4) samples, followed in turn by the ZnAl(2)O(4) nanoparticles prepared from Al(2)(SO(4))(3)∙18H(2)O and AlCl(3)∙6H(2)O. These differences are attributed to combinational changes in Eg and the defect types of the ZnAl(2)O(4) nanoparticles.