# Enhancing Methyl Orange Degradation with Laser-Generated ZnO and Ce-Doped ZnO Nanoparticles
## 1 Introduction  
Water pollution due to organic dyes has been a global phenomenon. For the past five decades, a considerable quantity of organic dye pollutants, including Methyl Orange (MO), has been discharged into the natural environment, including water bodies. MO, as a prevalent synthetic dye, finds extensive application in numerous industries such as textiles, paper manufacturing, plastics, and cosmetics, substantially impacting both human life and the biosphere [1]. Numerous methodologies have been utilized to remediate effluents containing pollutants. However, these conventional approaches often generate secondary waste products that require additional treatment [2]. In recent years, significant attention has been directed toward the photodegradation of organic dyes employing semiconducting nanoparticles (NPs) through photoexcited electron-hole pairs, with semiconductors like TiO\({}_{2}\) and Zinc Oxide (ZnO) under the influence of light [3]. This method has garnered substantial interest owing to its manifold benefits [2]. ZnO is a prominent metal oxide semiconductor characterized by its substantial direct band gap of 3.37 eV, a high binding energy of 60 meV, and remarkable thermal and chemical stability [4]. The photogenerated holes in ZnO exhibit strong oxidizing capabilities, attributed to their valence band (VB) position, enabling effective degradation of a wide range of organic dye compounds, making it a valuable component in wastewater treatment for environmental remediation [5]. Additionally, ZnO nanoparticles (ZnO NPs) have been extensively investigated due to the beneficial effects of nano-crystallization on the physical and optical properties of water treatment processes [6]. This has further contributed to the widespread exploration and application of ZnO NPs in various environmental purification efforts. Various methodologies have been utilized to augment the photocatalytic activity of ZnO. One well-known approach involves the introduction of specific cations through doping, which can create trapping sites for photogenerated charge carriers, leading to a reduction in the recombination rate of electron-hole pairs. Additionally, doping ZnO with transition and rare earth metals has been found to be a beneficial and feasible means of achieving a delicate equilibrium between enhanced chemical stability and favorable physical properties [7]. Cerium (Ce), a rare earth element, serves as an effective dopant capable of creating trapping sites for photogenerated charge carriers. Beyond its advantageous attributes of being cost-effective, low in toxicity, and environmentally friendly, Ce finds application as an oxygen storage promoter, leading to a reduction in the recombination rate of electron-hole pairs and the narrowing of the band gap through the generation of additional energy levels [8; 9]. Typically, such dopants are integrated into the ZnO matrix, occupying either substitutional or interstitial sites. This strategic inclusion of dopants has yielded a broader absorption range and improved light utilization, culminating in a notable enhancement of the overall photocatalytic performance [10; 11]. A variety of techniques, including the sol-gel spin-coating method, spray pyrolysis, hydrothermal synthesis, RF magnetron sputtering, pulse laser deposition, and other approaches, have been employed to synthesize Ce-doped ZnO (ZnOCe) nanorods. For instance, a study focused on the photodegradation capabilities of ZnO:Ce nanorods and the effects of Ce doping on the optical, structural, and electronic properties of ZnO rods was reported [12]. The results highlighted that ZnO:Ce nanorods exhibit dependable photocatalytic activity under solar-light irradiation. Interestingly, it was also elsewhere demonstrated that the synthesis of highly efficient Ce-doped ZnO nanorods as photocatalyst samples exhibited superior photocatalytic performance compared to pure ZnO nanorods [13].