Synthesis of Zinc Oxide Nano-Particles by Sol-Gel Method and Drop Wise Mixing Process

In the present study the authors report the synthesis of zinc oxide nanoparticles by sol-gel method. ZnO is prepared by conventional precipitation method using sodium hydroxide and zinc sulphate solutions. A homogeneous solution of NaOH was prepared by dissolving 1.6 gm of NaOH in 40 cc of distilled water. The PH value was recorded as 11.57. Another solution of zinc sulphate was prepared by dissolving 9.68 gm of zinc sulphate in 120 ml of distilled water. The NaOH solution already prepared was allowed to mix with ZnSO₄ solution by drop wise method at regular interval of time with continuous stirring for 65 minutes. The mixture was left for 48 hours then it was filtered out using whatmann paper and washed with deionised water several times. The residue was spread on a glass plate and placed in an oven for five hours where alternate heating and cooling was applied. It was heated for one hour at 1500°C then allowed to cool for 30 minutes. The zinc oxide was collected in fine powder form named as ZnO-A. Next the NaOH solution was suddenly mixed with ZnSO₄ solution and after passing through same operation, the ZnO nanoparticles were collected in powder form named ZnO-B. The X-ray diffraction pattern shows that ZnO-A nanoparticle are highly crystalline with respect to ZnO-B. The surface morphology was recorded by SEM which indicates that the nanoparticles prepared by drop wise method (ZnO-A) are in cluster form where as ZnO-B are in the form of nanosheets. The X-ray diffraction pattern also shows that both ZnO-A and ZnO-B, nanoparticles are of hexagonal structure and grain size was calculated to be very small. The size of ZnO-A and ZnO-B are reported as 34.58 nm and 21.8 nm respectively.