Combustion Synthesis of ZnO/ZnS Nanocomposite Phosphors

In the present study, combustion synthesis of zinc oxide and zinc sulfide nanoparticles as well as their composite was studied using zinc nitrate and thioacetamide as starting materials, and ethylene glycol as fuel. The influence of different parameters such as oxidizer to fuel (O:F) ratios and calcination process on the structure, microstructure, photoluminescence and optical properties was studied. X-ray diffraction (XRD) patterns showed different combinations of wurtzite structure for zinc oxide and zinc sulfide phases obtained using different O:F ratios of 1:1 and 2:3. Scanning electron microscopy (SEM) micrographs revealed that particles with different morphologies were synthesized depending on the O:F ratio. Besides, nanometer particles, or even quantum dots, could be obtained. Transmission electron microscopy (TEM) micrographs also showed the formation of zinc oxide/ zinc sulfide quantum dots composite using ethylene glycol fuel with O:F ratio of 2:3. Fourier transformed infrared (FTIR) analysis of samples showed carbon bonds of carbonaceous matters in addition to Zn-O and Zn-S bonds due to incomplete combustion. Photoluminescent emission spectra indicated that the highest intensity of emission in blue-green region was obtained from the particle synthesized using ethylene glycol and O:F ratio of 2:3, which may be related to the high density of lattice defects. Band gaps estimated using UV-visible (UV-Vis) spectra were 3.4 and 5.4 eV which can be assigned to the dual nature of particles: in some parts quantum size and in the other parts nanosize particles.