X-ray diffraction technique was used toexamine the crystal structure of the ZnO nanoparticles, as shown in Fig. 2. The XRD results obtained werecompared to the Joint Committee on Powder Diffraction Standards (JCPDS) X raydata file.
Patterns peak of XRD shows a good agreement with Hexagonal structurebase on. In the observed XRD patterns, no other diffraction peaks related withany impurity is detected, confirms the high purity of synthesized ZnO particles17. Average crystal size of synthesized particles obtained fromScherrer equation (Eq. (2)) 18.D= (180 K ?) / (? B Cos?) (2) WhereD, B, K, ? and ? are the average crystallite size, width of the maximum band inhalf of height, Scherrer constant equation (equal to 0.89), angle and wavelengthof the X-ray, respectively. From Scherer equation, the crystallize size of ZnO nanoparticles is estimated to 20 nm.The morphology and the grain size of ZnO nanoparticles were examined by transmission electron spectroscopy (TEM).
Fig. 3 shows theTEM images of nanoparticles withhexagonal polyhedral structure and grain average size of 30 nm. Due to thepolyhedral grains, crystalline structure of particles is observable. Thisobservation confirms the high degree of crystallinity of produced powder 19. The absorption spectra and band gap energyof the ZnO nanoparticles are shown in Fig. 4.
Accordingto the UV–vis absorption spectra, intense absorption peak is observed in 370 nm. The results reveal that the prepared ZnO particlesare sensitive to light radiation. Quantitiesof the band gap of the particles are determined by following Eq. (3) 20.(?h?)2 = B (h?-Eg) (3) Where ?, B, h?, and Eg are the absorption coefficient, constant ofthe equation, photon energy, and band gap, respectively. The function of (?h?)2versus photon energy (h?) depicted in Fig.
4. The band gap energy of particles wascalculated to be 3 eV. The narrow band gap of particles is prone to beingexcited by light to produce •OH radicals in solution 21.