The effect of citric acid on morphology and photoluminescence properties of white light emitting ZnO–SiO2 nanocomposites

• The ZnO–SiO2 nanocomposites were prepared by sol-gel combustion method.
• The citric acid content was varied as 1, 5 and 10 ratio with respect to one mole of zinc.
• The SEM images showed the spherical, flower, and platelet like morphology.
• The photoluminescence properties of the nanocomposites were investigated in detail.
• The Zn:CA – 1:1 ratio shows the CIE value in the white light region could be applied for SSL.

The white light emitting ZnO–SiO2 nanocomposites were synthesized by sol-gel combustion method using zinc nitrate, citric acid and tetraethoxysilane. To analyze the effect of fuel content on the photoluminescence properties of ZnO–SiO2 nanocomposites, the citric acid content was varied as 1, 5, and 10 moles with respect to one mole of zinc. The SEM images of the nanocomposites revealed the spherical, flower and platelet like morphology with variation in citric acid content and annealing temperatures. The ZnO–SiO2 nanocomposites prepared with various Zn:CA ratio excited at UV (280 nm), near UV (365 nm), violet (405 nm) and blue (465 nm) wavelength showed blue and greenish–yellow emission. Among all ratios, the ZnO–SiO2 nanocomposites with Zn:CA – 1:1 ratio showed the intense broad band emission compared to Zn:CA – 1:5 and 1:10 values. This particular composition of sample excited under violet (405 nm) LED source shows white light, as confirmed by the CIE chromaticity coordinates (x = 0.342, y = 0.318).