nanomaterials Article The Effect of Precursor Concentration on the Particle Size, Crystal Size, and Optical Energy Gap of Ce x Sn 1-x O 2 Nanofabrication Naif Mohammed Al-Hada 1,2,3, * , Rafiziana Md. Kasmani 2 , Hairoladenan Kasim 4, *, Abbas M. Al-Ghaili 5, *, Muneer Aziz Saleh 2 , Essam M. Banoqitah 6 , Abdulsalam M. Alhawsawi 6,7 , Anwar Ali Baqer 8 , Jian Liu 1 , Shicai Xu 1 , Qiang Li 1 , Azlan Muhammad Noorazlan 9 , Abdullah A. A. Ahmed 3,10 , Moayad Husein Flaifel 11,12 , Suriati Paiman 13 , Nazirul Nazrin 13 , Bandar Ali Al-Asbahi 14 and Jihua Wang 1, *   Citation: Al-Hada, N.M.; Md. Kasmani, R.; Kasim, H.; Al-Ghaili, A.M.; Saleh, M.A.; Banoqitah, E.M.; Alhawsawi, A.M.; Baqer, A.A.; Liu, J.; Xu, S.; et al. The Effect of Precursor Concentration on the Particle Size, Crystal Size, and Optical Energy Gap of Ce x Sn 1−x O 2 Nanofabrication. Nanomaterials 2021, 11, 2143. https:// doi.org/10.3390/nano11082143 Academic Editor: Sotirios Baskoutas Received: 15 July 2021 Accepted: 14 August 2021 Published: 22 August 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 Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou 253023, China; liujian.cn@live.com (J.L.); shicaixu@dzu.edu.cn (S.X.); qiangli_chem@hotmail.com (Q.L.) 2 School of Chemical and Energy Engineering, Universiti Teknologi Malaysia, Skudai, Johor Bahru 81310, Malaysia; rafiziana@utm.my (R.M.K.); mouneersaleh@yahoo.com (M.A.S.) 3 Department of Physics, Faculty of Applied Science, Thamar University, Dhamar 87246, Yemen; abdullah2803@gmail.com 4 College of Computing & Informatics (CCI), Universiti Tenaga Nasional (UNITEN), Kajang 43000, Malaysia 5 Institute of Informatics and Computing in Energy (IICE), Universiti Tenaga Nasional (UNITEN), Kajang 43000, Malaysia 6 Department of Nuclear Engineering, Faculty of Engineering, K. A. CARE Energy Research and Innovation Center, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia; ebanoqitah@kau.edu.sa (E.M.B.); amalhawsawi@kau.edu.sa (A.M.A.) 7 Center for Training & Radiation Prevention, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia 8 Department of Physics, Faculty of Science for Women, University of Baghdad, Baghdad 10071, Iraq; anwaralibaqerkram@yahoo.com 9 Physics Department, Faculty of Science and Mathematics, University Pendidikan Sultan Idris, Tanjong Malim 35900, Malaysia; Azlanmn@fsmt.upsi.edu.my 10 Fachbereich Physik, Center for Hybrid Nanostructures (CHyN), Universität Hamburg, 20146 Hamburg, Germany 11 Department of Physics, College of Science, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia; physci2007@gmail.com 12 Basic and Applied Scientific Research Center, College of Science, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia 13 Department of Physics, Faculty of Science, University Putra Malaysia, Serdang 43400, Malaysia; suriati@upm.edu.my (S.P.); nazirulnazrin@ymail.com (N.N.) 14 Department of Physics & Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia; balasbahi@ksu.edu.sa * Correspondence: naifalhada@yahoo.com (N.M.A.-H.); hairol@uniten.edu.my (H.K.); abbas@uniten.edu.my (A.M.A.-G.); jhw25336@126.com (J.W.) Abstract: In the present work, a thermal treatment technique is applied for the synthesis of Ce x Sn 1−x O 2 nanoparticles. Using this method has developed understanding of how lower and higher precur- sor values affect the morphology, structure, and optical properties of Ce x Sn 1−x O 2 nanoparticles. Ce x Sn 1−x O 2 nanoparticle synthesis involves a reaction between cerium and tin sources, namely, cerium nitrate hexahydrate and tin (II) chloride dihydrate, respectively, and the capping agent, polyvinylpyrrolidone (PVP). The findings indicate that lower x values yield smaller particle size with a higher energy band gap, while higher x values yield a larger particle size with a smaller energy band gap. Thus, products with lower x values may be suitable for antibacterial activity applications as smaller particles can diffuse through the cell wall faster, while products with higher x values may be suitable for solar cell energy applications as more electrons can be generated at larger particle sizes. The synthesized samples were profiled via a number of methods, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). As revealed by the XRD pattern analysis, the Ce x Sn 1−x O 2 Nanomaterials 2021, 11, 2143. https://doi.org/10.3390/nano11082143 https://www.mdpi.com/journal/nanomaterials