Enhanced antibacterial properties of green synthesized nano ceria via Agathosma betulina natural extract F.T. Thema a,b,d,⇑ , D. Letsholathebe a,c , K. Mphale c a UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria, South Africa b Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape, South Africa c Department of Physics, University of Botswana, P/Bag 0022, Gaborone, Botswana d Department of Animal Science and Production, Botswana University of Agriculture and Natural Resources, P/Bag 0027, Gaborone, Botswana article info Article history: Received 16 April 2020 Received in revised form 29 April 2020 Accepted 1 May 2020 Available online xxxx Keywords: Green synthesis Cerium oxide Nanoparticles Antibacterial activity Agathosma betulina flower’s extract abstract In this contribution, it is reported for the first time from literature the possibility of synthesizing CeO 2 nanoparticles using entirely new green process. This is in view of using natural extract of Agathosma betu- lina as a chelating agent at room temperature. The antibacterial activity of CeO 2 nanoparticles is there- fore, investigated. The high-resolution transmission electron microscopy (HRTEM) and the selected area electron diffraction (SAED) confirmed the polycrystallinity of the CeO 2 nanoparticles annealed at various temperatures. X-ray diffraction showed complementary investigations that substantiated the sin- gle phase and the elementary purity of the CeO 2 nano-scaled particles as shown by the EDS. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the NANOSMATAFRICA- 2018. 1. Introduction Currently nanoparticles (NPs) are attracting attention due to their exceptionally small size, large surface to volume ratio and many technological applications which cannot be achieved when compared to bulk of the same chemical composition [1,2]. Design and fabrication of materials with novel applications can, therefore, be achieved by controlling their size and shape at nano meter scale [3,4]. Cerium (Ce), a rare earth element belonging to the lanthanide series, is one of the most abundant rare earth elements. It exists both in the trivalent state (Ce 3+ , cerous) and tetravalent state (Ce 4+, ceric), which can switch from one state to another. The band- gap energy of pure CeO 2 is 3.2 eV [5] and a large exciton binding energy. CeO 2 is a crystal structure with space group Fm3m [6]. Ceria a crystalline material, has received significant attention in recent years due to many distinctive characteristics such as unique ultraviolet radiation, absorbing ability, high stability at higher tem- perature, high hardness index and its reactivity [7]. Cerium oxide (CeO 2 ) nanoparticles have therefore, also attracted tremendous attention due to their unique applications as catalysts or catalyst support, superconductor buffer layer, oxy- gen storage materials, fuel cell electrolyte, and UV absorbents [8]. Most importantly, the excellent antibacterial activity of CeO 2 nanoparticles against both Gram-negative and Gram-positive bac- teria has been demonstrated in recent studies [9-12]. In compar- ison to ZnO and TiO 2 , CeO 2 possesses a relatively small band gap, making it a better UV absorbent for textile fiber coating [13]. The absorption spectra of CeO 2 nanoparticles demonstrate the better UV absorption property of CeO 2 nanoparticles in the UV wave- length range (315 nm  400 nm). However, in the field of nanoscience and nanotechnology, design and synthesis of NPs with tailor-made structural properties is a very challenging task. Hence sseveral synthetic methods of ceria by different methods such as sol–gel [14], hydrothermal [15], sonochemical [16], micro emul- sion [17], precipitation [18] and combustion [19] have been reported. Among these various techniques employed to synthesize CeO 2 nanoparticles, combustion synthesis proved to be effective, low-cost, and rapid preparation process [20]. This method is unique to produce homogeneous and well crystalline multi com- ponent oxides, without the intermediate decomposition or calcina- tion step. Consequently, appropriate synthetic routes are still developed to ensure that reliable supply of such NPs is enough and effective quantities [8,21]. The use of extracts obtained from plants, partic- ularly the easily available parts such as leaves, and stem bark are highly useful [9,10]. Also, the collection of these plant parts does https://doi.org/10.1016/j.matpr.2020.05.010 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the NANOSMATAFRICA-2018. ⇑ Corresponding author. E-mail address: ftthema@gmail.com (F.T. Thema). Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: F. T. Thema, D. Letsholathebe and K. Mphale, Enhanced antibacterial properties of green synthesized nano ceria via Agathosma betulina natural extract, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.05.010