crystals Article Phytosynthetic Fabrication of Lanthanum Ion-Doped Nickel Oxide Nanoparticles Using Sesbania grandiflora Leaf Extract and Their Anti-Microbial Properties Srihasam Saiganesh 1 , Thyagarajan Krishnan 2, *, Golla Narasimha 3 , Hesham S. Almoallim 4 , Sulaiman Ali Alhari 5 , Lebaka Veeranjaneya Reddy 6 , Koduru Mallikarjuna 7,8 , Arifullah Mohammed 9,10, * and Vattikuti S. V. Prabhakar 11, *   Citation: Saiganesh, S.; Krishnan, T.; Narasimha, G.; Almoallim, H.S; Alhari, S.A.; Reddy, L.V.; Mallikarjuna, K.; Mohammed, A.; Prabhakar, V.S.V. Phytosynthetic Fabrication of Lanthanum Ion-Doped Nickel Oxide Nanoparticles Using Sesbania grandiflora Leaf Extract and Their Anti-Microbial Properties. Crystals 2021, 11, 124. https:// doi.org/10.3390/cryst11020124 Academic Editors: Leonid Kustov and Chinho Park Received: 11 December 2020 Accepted: 23 January 2021 Published: 27 January 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Physics, JNTU Ananthapuramu, Anantapur 515002, India; srihasamsaiganesh@gmail.com 2 Department of Physics, JNTU College of Engineering Pulivendula, Pradesh 516390, India 3 Department of Virology, S. V. University, Tirupati 517502, India; gnsimha123ster@gmail.com 4 Department of Oral and Maxillofacial Surgery, College of Dentistry, King Saudi University, PO Box-60169, Riyadh-11545, Saudi Arabia; hkhalil@ksu.edu.sa 5 Department of Botany and Microbiology, College of Science, King Saudi University, PO Box-60169, Riyadh-11545, Saudi Arabia; sharbi@ksu.edu.sa 6 Department of Microbiology, Yogi Vemana University, Kadapa, Andhra Pradesh 516005, India; lvereddy@yahoo.com 7 Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam; koduru.mallikarjuna@tdtu.edu.vn 8 Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam 9 Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli 17600, Malaysia 10 Institute of Food Security and Sustainable Agriculture, Universiti Malaysia Kelantan, Jeli 17600, Malaysia 11 School of Mechanical Engineering, Yeungnam University, 280 Daehak-ro, Gyeongsan-si, Gyeongsangbuk-do 38533, Korea * Correspondence: ktrjntu@gmail.com (T.K.); aurifullah@umk.edu.my (A.M.); vsvprabu@gmail.com (V.S.V.P.) Abstract: Over the past few years, the photogenic fabrication of metal oxide nanoparticles has at- tracted considerable attention, owing to the simple, eco-friendly, and non-toxic procedure. Herein, we fabricated NiO nanoparticles and altered their optical properties by doping with a rare earth element (lanthanum) using Sesbania grandiflora broth for antibacterial applications. The doping of lanthanum with NiO was systematically studied. The optical properties of the prepared nanoma- terials were investigated through UV-Vis diffuse reflectance spectra (UV-DRS) analysis, and their structures were studied using X-ray diffraction analysis. The morphological features of the pre- pared nanomaterials were examined by scanning electron microscopy and transmission electron microscopy, their elemental structure was analyzed by energy-dispersive X-ray spectral analysis, and their oxidation states were analyzed by X-ray photoelectron spectroscopy. Furthermore, the an- tibacterial action of NiO and La-doped NiO nanoparticles was studied by the zone of inhibition method for Gram-negative and Gram-positive bacterial strains such as Escherichia coli and Bacillus sublitis. It was evident from the obtained results that the optimized compound NiOLa-04 performed better than the other prepared compounds. To the best of our knowledge, this is the first report on the phytosynthetic fabrication of rare-earth ion Lanthanum (La 3+ )-doped Nickel Oxide (NiO) nanoparticles and their anti-microbial studies. Keywords: Sesbania grandiflora leaf extract; green synthesis; NiO nanoparticles; characterization; antibacterial activity 1. Introduction Transition metal oxide nanoparticles (NPs), such as Cu 2 O, MnO 2 , NiO, TiO 2 , Co 3 O 4, SnO 2, and Fe 2 O 3 , are excellent candidates for use in electrocatalytic activity as they promote electron-transfer reactions and in medicinal applications. Among these, semiconductor Crystals 2021, 11, 124. https://doi.org/10.3390/cryst11020124 https://www.mdpi.com/journal/crystals