A comparative study of ZnAl2O4 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.