Synthesis and Characterization of Zinc Oxide Nanoparticles Using Moringa Leaf Extract

Department of Physics, College of Natural and Computational Science, Dambi Dollo University, Ethiopia Centre for Excellence-Indigenous Knowledge, Innovative Technology Transfer and Entrepreneurship, Dambi Dollo University, Ethiopia Department of Mechanical Engineering, ULTRA College of Engineering and Technology, Madurai, Tamil Nadu, India TIFAC CORE HD, Department of Pharmacognosy, JSS Academy of Higher Education and Research, Ooty, Tamil Nadu, India Department of Pharmacognosy, JSS Academy of Higher Education and Research, Ooty, Tamil Nadu, India Department of Mechanical Engineering, College of Engineering and Technology, Dambi Dollo University, Ethiopia


Introduction
Currently, nanotechnology is one of the best dynamic investigations for researchers to endeavor widespread research for the synthesis of nanoparticles by the leaf extract of plants and increase the biosynthesis of inorganic metallic oxide nanoparticles like zinc oxide, copper oxide, and titanium oxide NPs. NPs display absolutely enhanced properties depending on specific features such as size, delivery, and morphology [1]. An eco-friendly green-intermediated preparation of inorganic nanoparticles is a fast increasing research in the member of nanosciences [2] than that of physical method and chemical solution method. Biosynthesis techniques that retain plant extraction have pinched consideration as a humble and feasible alternative to chemical processes and physical techniques [3]. Zinc oxide is selected for the present work. It goes to a cluster of metal oxides for photooxidization and photocatalytic capability alongside chemical solutions and biological types [4]. Zinc oxide NPs have extensive applicable attention because of their antimicrobial, ultraviolet blocking, and maximum catalytic and photochemical actions [4]. Zinc oxide NPs revealed antimicrobial activities even at minor concentrations, appropriate for thin coating applications [5]. Chemical techniques of synthesis of NPs are also excessive in the atmosphere [6]. So, for many causes, mainly for eco-friendly benefits, the green synthesis techniques or green preparation of NPs has been deliberated by scholars [7]. In these new techniques (i.e., green deposition), plants, microbiology, or fungus serve as the root to depose NPs. They specified an effective way to feat the biological tools that existed in nature [8,9]. Plant life might be broadly used because of its richness, easy obtainability, and eco-friendly compatibility without prompting opposing atmospherical impacts [10].
The processes of preparing nanoparticles from various types of plants are technically simpler than chemical techniques. Hence, organic ingredients play an essential role in the preparation of nanoparticles, and they are taken as unique solutions that might replace with chemical techniques. Floras such as Aloe vera, Glycosmis pentaphylla leaf, Limonia acidissima, and Moringa oleifera are used to prepare zinc oxide nanoparticles. Even if the implication of plants for the formation of NPs has been emphasized inappropriately [11][12][13][14], only a few numbers of investigations have been conducted on this area in Ethiopia. Since Ethiopia is regarded by an amazing diversity of medicinal plants, supplementary studies are necessary to be carried out in this repute. The analysis of nanoparticle activities on antibacteria is using gram-positive and gram-negative bacteria. M. oleifera is classified into the family Moringaceae. It is a moderate-sized plant that matures to the length of 5 to 12 meters. The leaves of the Moringa oleifera tree are bi-and trijaunt inherent with the inner elliptical-shaped brochures [15] and serve as a cultural medical plant. Different bodies of it are active in treating different diseases like anemia, blindness, arthritis, hyperthyroidism, rheumatism, epilepsy, Crohn's disease, herpes simplex virus, gout, and sexually transmitted diseases [16][17][18]. M. oleifera is filled in nourishment due to the presence of essential phytochemicals. The phytochemical profile of its leaves exhibited the presence of essential minerals, vitamins, sterols, anthraquinones, alkaloids, terpenoids, flavonoids, tannins, and saponins [19]. These phytoconstituents lead to anti-inflammatory, antiulcer, antidiabetic [20], anticancer [21], antimicrobial, antioxidant, and antifungal properties [22].
Synthesization of nanoparticles from leaf extraction using plants is simpler to use. It is not toxic, and there is no poison released to the environment. Moreover, it should be replaced with other methods of preparation of nanoparticles. Because of paramount mentioned facts about the medical ideals of this plant, the present study brought a biomimetic approach for the green synthesis of ecofriendly zinc oxide nanoparticles from Moringa oleifera through bioreduction, UV-visible spectroscopy, scanning electron microscopy, X-ray diffraction characterization, and antimicrobial studies.

Material and Methods
For the preparation of nanoparticles extracted from moringa, zinc nitrate hexahydrate, deionized water was bought from shops of chemicals. All instruments are purified with weak acid like nitric acid and additionally by deionized water then dried up by putting it in the oven before the next procedure. The leaves of Moringa oleifera were collected from Dambi Dollo University, Ethiopia.

Synthesis of Aqueous Extract from Moringa oleifera
Leaves. The fresh leaves of Moringa oleifera (Figure 1) are gathered, and new leaves were washed using water to eliminate dirt and dust spots. The leaves of the plant were dried in the air for two weeks because the time at which this study was conducted was the rainy season, and then, leaves were ground with the help of a mortar with pestle till the leaves were well powdered finely. The aqueous extract of Moringa oleifera leaves was prepared using 10 grams of powder of moringa leaves and put to 90 ml of deionized water at 70°C to 90°C for 20 minutes. The extract was purified through strainer paper. Finally, the filtered solution was kept in the refrigerator at 6°C for the next works.

Synthesis of Zinc Oxide Nanoparticles from Leaf
Extraction. The source of zinc ion was zinc nitrate hydroxide used in the present study which was bought from chemical shop, Addis Ababa, Ethiopia. The solution of (Zn(NO 3 ) 2 ·6H 2 O) was prepared in deionized water. For the preparation of zinc oxide NPs, the flask containing 50 ml of zinc nitrate hydroxide (0.2 M) was reacted with 10 mm of the aqueous leaf extract of Moringa oleifera and stirred using a magnetic stirrer heated at 70°C and stirring is nonstop until a homogenous mixture of the solution is attained.
The uniform solution is desiccated in a warm air oven at the temperature of 100-110°C for 90 minutes and annealed at 300-350°C for 1 h in a muffle boiler. The particles with yellow color obtained are wrinkled in a metallic mortar and pestle to get green-synthesized zinc oxide nanoparticles.
The crystal phase analysis of the ZnO nanoparticles was characterized by using the Bruker D8 diffract meter with CuKα (1.5406 A°) radiation occupied at 40 mA and 40 kV. The nanoparticles were scanned, regulating the diffractometer in the 2θ range of 25-45°at a step size of 0.12 and scanning rate of 0.6 sec -1 . The optical properties of the ZnO nanoparticles were recorded by a Shimadzu UV-3600 plus UV-Vis spectrophotometer with PerkinElmer. The morphology of the films was studied by scanning electron microscopy (SEM) integrated with an X-ray diffraction (XRD) analyzer.

X-Ray Diffraction Analysis of ZnO NPs from Moringa
Leaf Extract. X-ray deflection configurations of equipped zinc oxide nanoparticles reveal that all peaks agree with the standard data. The appeared peaks of X-ray diffraction ( Figure 2) are wonderfully arranged with the hexagonal crystal structure [23]. The sharpness, as well as peaks having intensity in Figure 2, expresses that the nanoparticles are extremely crystalline. The pattern can be indexed for diffractions from the (111), (110), and (101) planes. There are no other peaks conforming to impurity that is found, revealing the high purity of the prepared outcomes.
By using XRD data, it was created that the peaks are broad; signifying that the crystallites have sizes in the nm range, and the diameter (D) was calculated using Scherrer's formula where K stands for Debye Scherrer constant, λ is for Xray wavelength, β is the width of the peak of half maximum, and θ is the diffraction angle [24]. The estimated crystalline size of ZnO is measured by X-ray diffraction data, and it was obtained around 50 nm.
The calculation of the crystal size of ZnO nanoparticles is summarized in Table 1.

UV-Vis Analysis of ZnO NPs from Moringa Leaf Extract.
As illustrated in Figure 3, the absorption spectrum of the prepared zinc oxide nanoparticles with the absorption peak nearby is 350 nanometers. It expresses that ZnO nanoparticles exhibit excitation absorption (at 350 nm) due to their huge excitation binding energy at 37°C. The existed sharp bands of Zn colloids were perceived at 350 nm, which demonstrates that the Zn ion is competently reduced by the M. oleifera leaf extract. The existence of blue-shifted absorption spectrum is with deference to the large value (375 nm) of the zinc oxide nanoparticles approved by the wavelength of 350 nm absorption peak, because of the quantum imprisonment effect, which is in excellent match with the beforehand report [25][26][27][28][29][30][31].

Scanning Electron Microscopy Analysis of ZnO NPs from
Moringa Leaf Extracts. Afterward, the confirmation of the sample's X-ray diffraction results was further headed for the scanning electron microscopy study. The size of the crystal, the shape of the crystal, and the morphology of the zinc oxide nanoparticle are clearly shown by the scanning electron microscope image as displayed in Figure 4. Detailed structural characterizations demonstrate that the synthesized products are flower-like shapes and crystal in arrangement, and the measured diameters were about 50 nm. These results also agree with those previously reported [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49].

Conclusion
The green synthesis of zinc oxide NPs was efficaciously produced from leaf extract of Moringa oleifera. The biosynthesis technique used is modest and easily biodegradable and conducted in a short period. The revealed yellow color indicates the preparation of zinc oxide NPs, which further established the reduction of Zn ions into ZnO nanoparticles by using ultraviolet-visible spectroscopy. The ultraviolet spectroscopic absorption peak is at 350 nanometers. XRD and SEM analysis show that the particle property prepared was polycrystalline and had no void and flower-like shape. The antibacterial study demonstrated that the gram-negative (G − ) and gram-positive (G + ) bacteria are profound to the zinc oxide nanoparticles.

Data Availability
The data used to support the findings of this study are included within the article.

Disclosure
This study was performed as a part of the employment of the authors.

Conflicts of Interest
The authors declare that there are no conflicts of interest.