This study investigated the influence of chemical reagent selection on the properties of ZnO nanoparticles synthesized using the microwave-assisted hydrothermal method to control the intensities of near-band-edge (NBE) and defect-related deep-level (DLE) emissions. Two zinc precursors—zinc nitrate and zinc chloride—along with three different precipitating agents (NaOH, KOH, and NH₄OH) were used. ZnO nanoparticles from the ZnCl₂ precursor exhibited two orders of magnitude higher NBE/DLE intensity ratio compared to those obtained from zinc nitrate characterized by a higher contribution from defect-related emissions. Chlorine ions in ZnO nanoparticles play a key role in passivating defects by forming V₀-Cl₂ complexes, quenching luminescence associated with oxygen vacancies (V₀). Thermal treatment in a nitrogen atmosphere enhanced defect-related luminescence, possibly due to chlorine atom diffusion. This study highlights a successful synthesis of ZnO nanoparticles with low defect-related luminescence (DLE) achieved via the microwave-assisted hydrothermal method, a result rarely reported in the literature. The results emphasize the importance of reagent selection in controlling the morphology and optical properties, especially the defect density of ZnO nanoparticles. Optimizing these properties is crucial for biomedical applications such as bioimaging, antibacterial treatments, and photocatalysis.

With the spread of nanotechnology use in industry, exposure to nanomaterials is currently exponentially increasing. With reports indicating nanoparticles’ ability to pass through key biological barriers—gastrointestinal, lung, skin, blood-brain and the placenta barriers—the question of their safety, particularly the risks associated with embryonic development, arises. The aim of this article is to verify the impact of ZnO nanoparticles, which are commonly used and considered to be safe for adult organisms on the developing embryo. In the current study, the influence of the dose and shape of ZnO nanoparticles (oval vs. long) was evaluated in the chicken embryo model. The oxidative stress (superoxide dismutase (SOD)) activity, malondialdehyde (MDA) and carbonylated protein ((CP) levels), and gene expression changes (full genomic microarray study) were tested. We found that at both doses (10 µg/mL and 100 µg/mL, 100 µL into the air chamber) neither elongated nor oval ZnO nanoparticles changed in ovo mortality. Long ZnO nanoparticles had a lesser and more delayed impact on evaluated parameters, regardless of their higher in vitro toxicity. However, both nanoparticle forms induced changes in the oxidoreductive potential and affected expression of a significant number (1487 for oval and 548 for long ZnO nanoparticles) of identified genes during early embryo development.

With the growing use of nanotechnology, the issue of exposure to non-biodegradable nanomaterials is becoming increasingly significant, raising concerns about their potential impact on developing organisms. Their use in dentistry, optoelectronics and biomedicine leads to environmental exposure. Zirconium oxide (ZrO₂) and yttrium oxide (Y₂O₃) nanoparticles are chemically stable and poorly soluble materials; however, their embryotoxicity remains extremely poorly characterised. This study assessed the effect of ZrO₂ and Y₂O₃ nanoparticles on the development of chicken embryos. The nanoparticles were administered into the air chamber of the egg on the first day of incubation at concentrations of 10 and 100 µg/mL. The redox status was assessed based on superoxide dismutase activity, malondialdehyde content and the level of carbonylated proteins. Transcriptomic responses were evaluated using a whole-genome microarray, and selected genes were verified by qPCR. Both types of nanoparticles induced time-dependent changes in markers of oxidative stress. Transcriptomic analysis revealed distinctly different responses, with seven genes showing altered expression following ZrO₂ administration, compared with 555 following Y₂O₃ administration. These results indicate that non-biodegradable metal oxide nanoparticles can influence the redox balance and gene expression during early embryonic development, with the extent of the response depending on the type of nanoparticle.