ZnO nanoparticles have been synthesized by precipitation method from Zinc nitrate. The powder was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, UV-vis optical absorption, and photoluminescence spectroscopy analyses. XRD patterns showed that ZnO nanoparticles have hexagonal unit cell structure. SEM and TEM pictures reveal the morphology and particle size of prepared ZnO nanoparticles. The UV-vis absorption spectrum shows an absorption band at 355？nm due to ZnO nanoparticles. The photoluminescence spectrum exhibits two emission peaks one at 392？nm corresponding to band gap excitonic emission and another located at 520？nm due to the presence of singly ionized oxygen vacancies. The synthesis method has potential for application in manufacturing units due to ease processing and more economical reagents. 1. Introduction Nowadays, there has been an increasing demand for the development of nanosized semiconductors due to their significant electrical and optical properties which are highly useful in fabricating nanoscaled optoelectronic and electronic devices with multifunctionality [1–3]. Among various semiconducting materials, zinc oxide (ZnO) is a distinctive electronic and photonic wurtzite n-type semiconductor with a wide direct band gap of 3.37？eV and a high exciton binding energy (60？meV) at room temperature [4, 5]. The high exciton binding energy of ZnO would allow for excitonic transitions even at room temperature, which could mean high radiative recombination efficiency for spontaneous emission as well as a lower threshold voltage for laser emission. The lack of a centre of symmetry in wurtzite, combined with a large electromechanical coupling, results in strong piezoelectric and pyroelectric properties and hence the use of ZnO in mechanical actuators and piezoelectric sensors [6, 7]. ZnO is potential candidate for optoelectronic applications in the short wavelength range (green, blue, UV), information storage, and sensors as it exhibits similar properties to GaN [8–10]. ZnO nanoparticles are promising candidates for various applications, such as nanogenerators [11], gas sensors [12], biosensors [13], solar cells [14], varistors [15], photodetectors [16], and photocatalysts [17]. From the literature survey, it was found that various approaches for the preparation of ZnO nanopowders have been developed, namely, sol-gel, microemulsion, thermal decomposition of organic precursor, spray pyrolysis, electrodeposition, ultrasonic, microwave-assisted techniques, chemical
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