Citation: Gatou, M.-A.; Lagopati, N.; Vagena, I.-A.; Gazouli, M.; Pavlatou, E.A. ZnO Nanoparticles from Different Precursors and Their Photocatalytic Potential for Biomedical Use. Nanomaterials 2023, 13, 122. https://doi.org/10.3390/ nano13010122 Academic Editor: Youngdong Yoo Received: 30 November 2022 Revised: 16 December 2022 Accepted: 21 December 2022 Published: 26 December 2022 Copyright: © 2022 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/). nanomaterials Article ZnO Nanoparticles from Different Precursors and Their Photocatalytic Potential for Biomedical Use Maria-Anna Gatou 1,† , Nefeli Lagopati 1,2,† , Ioanna-Aglaia Vagena 2 , Maria Gazouli 2,3 and Evangelia A. Pavlatou 1, * 1 Laboratory of General Chemistry, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, 15772 Athens, Greece 2 Laboratory of Biology, Department of Basic Medical Sciences, Medical School, National and Kapodistrian University of Athens, 11527 Athens, Greece 3 School of Science and Technology, HellenicOpen University, 26335 Patra, Greece * Correspondence: pavlatou@chemeng.ntua.gr; Tel.: +30-210-772-3110 † These authors contributed equally to this work. Abstract: Semiconductor photocatalysts, particularly ZnO nanoparticles, were synthesized via the precipitation method using four different precursors (zinc acetate/zinc nitrate/zinc sulfate/zinc chloride) and compared, according to their optical, structural, photocatalytic, and anticancer proper- ties. The materials were characterized via X-ray Diffraction method (XRD), micro-Raman, Fourier Transform Infrared Spectroscopy(FT-IR), Brunauer–Emmett–Teller (BET), Dynamic Light Scattering (DLS), and Field Emission Scanning Electron Microscope (FESEM) analysis. Photocatalysis was conducted under UV and visible light irradiation, using Rhodamine B as the organic pollutant. It was observed that the highest photocatalysis efficiency was obtained by the nanoparticles synthesized from the zinc acetate used as precursor material. A cell-dependent anticancer efficiency of the tested ZnO nanoparticles was also observed, that was also attributed to the different precursors and the synthesis method, revealing that the nanoparticles that were synthesized from zinc acetate were more bioactive among the four tested precursors. Overall, the data revealed that both the enhanced photocatalytic and biological activity of ZnO nanoparticles derived from zinc acetate precursor could be attributed to the reduced crystalline size, increased surface area, as well as the observed hexagonal crystalline morphology. Keywords: photodegradation; nanomaterials; zinc oxide; photocatalytic response; dye degradation; cytotoxicity; precursors 1. Introduction During the last few decades, rapid industrialization, progressive urbanization, increas- ing population, irrational utilization of non-sustainable resources, as well as irrepressible exploitation of natural resources are leading to harmful and irreversible environmental damage [1]. The wastewater and effluents from several industries, such as textile, paint, leather, plastics, printing inks, cosmetics, food, refineries, and anthropogenic activities are putting at risk natural aquatic resources such as ponds, lakes, rivers, and oceans [2]. As a re- sult, the clean water crisis, declared to be among the most challenging, as well as imminent, global issues, could induce adverse effects in human survival [3,4]. These effluents contain a plethora of pollutant categories, such as organic (dyes, surfactants, phenols, etc.), inor- ganic (metal oxides, heavy metal ions and complexes, salts, etc.), pathogens, and various others. Among these types of pollutants, the organic ones are gaining constantly increasing attention due to certain characteristics, such as (a) extensive applications and subsequent discharge to water reservoirs and land areas, (b) extended persistence, (c) intense resistance, and (d) consequential impacts both on human health as well as the environment [5]. Nanomaterials 2023, 13, 122. https://doi.org/10.3390/nano13010122 https://www.mdpi.com/journal/nanomaterials