Controlled dispersion of ZnO nanoparticles produced by basic precipitation in solvothermal processes

Photodynamic Effectiveness of Copper-Iminopyridine Photosensitizers Coupled to Zinc Oxide Nanoparticles Against Klebsiella pneumoniae and the Bacterial Response to Oxidative Stress

One of the most urgent threats to public health worldwide is the ongoing rise of multidrug-resistant (MDR) bacterial strains. Among the most critical pathogens are MDR-Klebsiella pneumoniae strains. The lack of new antibiotics has led to an increased need for non-antibiotic antimicrobial therapies. Photodynamic therapy (PDT) has become increasingly significant in treating MDR bacteria. PDT uses photosensitizer compounds (PS) that generate reactive oxygen species (ROS) when activated by light. These ROS produce localized oxidative stress, damaging the bacterial envelope. A downside of PDT is the limited bioavailability of PSs in vivo, which can be enhanced by conjugating them with carriers like nanoparticles (NPs). Zinc nanoparticles possess antibacterial properties, decreasing the adherence and viability of microorganisms on surfaces. The additive or synergistic effect of the combined NP-PS could improve phototherapeutic action. Therefore, this study evaluated the effectiveness of the copper(I)-based PS CuC1 compound in combination with Zinc Oxide NP, ZnONP, to inhibit the growth of both MDR and sensitive K. pneumoniae strains. The reduction in bacterial viability after exposure to a PS/NP mixture activated by 61.2 J/cm2 of blue light photodynamic treatment was assessed. The optimal PS/NP ratio was determined at 2 µg/mL of CuC1 combined with 64 µg/mL of ZnONP as the minimum effective concentration (MEC). The bacterial gene response aligned with a mechanism of photooxidative stress induced by the treatment, which damages the bacterial cell envelope. Additionally, we found that the PS/NP mixture is not harmful to mammalian cells, such as Hep-G2 and HEK-293. In conclusion, the CuC1/ZnONP combination could effectively aid in enhancing the antimicrobial treatment of infections caused by MDR bacteria.

Eco-friendly synthesis of ZnO, CuO, and ZnO/CuO nanoparticles using extract of spent Pleurotus ostreatus substrate, and their antioxidant and anticancer activities

Biosynthesis techniques for nanomaterials have advanced significantly, promoting eco-friendly synthesis chemistry as a sustainable alternative to conventional methods. This study presents a novel and environmentally friendly approach for synthesizing nanoparticulate ZnO, CuO, and ZnO/CuO nanocomposites using aqueous extracts of Pleurotus ostreatus spent substrate, is reported. The structural, optical, and morphological properties of the synthesized NPs were analysed. A hexagonal phase of ZnO NPs and a monoclinic phase of CuO NPs were obtained according to the X-ray diffraction analysis. A reduction in the peak intensity of these metal oxides was observed in the ZnO/CuO NPs due to reduced crystallinity. The absorption spectra, obtained from the UV-vis analysis, showed peaks at 354, 365, and 525 nm for the ZnO, CuO, and ZnO/CuO NPs, respectively. An anticancer assay of the NPs was conducted using human embryonic kidney (HEK 293) and cervical carcinoma (HeLa) cell lines, while a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay was used for the antioxidant evaluation. The ZnO, CuO, and ZnO/CuO NPs showed higher antioxidant potency with IC50 of 2.15, 2.16, and 3.18 µg/mL, respectively, than the ascorbic acid (4.25 µg/mL). This indicates that the nanoparticles were more effective in capturing DPPH free radicals. Anticancer assays showed strong cytotoxic effects for all nanoparticles, with ZnO NPs exhibiting the highest activity (IC50: 1.94 μM for HEK 293 cells, 3.23 μM for HeLa cells), surpassing CuO and ZnO/CuO NPs. Cell viability for both HEK 293 and HeLa cells decreased as nanoparticle concentration increased, confirming dose-dependent cytotoxicity. The green synthesized metal oxides and their composite have the potential for biomedical applications.

Nanoparticles: a promising tool against environmental stress in plants

With a focus on plant tolerance to environmental challenges, nanotechnology has emerged as a potent instrument for assisting crops and boosting agricultural production in the face of a growing worldwide population. Nanoparticles (NPs) and plant systems may interact molecularly to change stress response, growth, and development. NPs may feed nutrients to plants, prevent plant diseases and pathogens, and detect and monitor trace components in soil by absorbing their signals. More excellent knowledge of the processes of NPs that help plants survive various stressors would aid in creating more long-term strategies to combat these challenges. Despite the many studies on NPs' use in agriculture, we reviewed the various types of NPs and their anticipated molecular and metabolic effects upon entering plant cells. In addition, we discussed different applications of NPs against all environmental stresses. Lastly, we introduced agricultural NPs' risks, difficulties, and prospects.

Green Synthesis of Zinc Oxide Nanoparticles: Preparation, Characterization, and Biomedical Applications - A Review

Over the last decade, biomedical nanomaterials have garnered significant attention due to their remarkable biological properties and diverse applications in biomedicine. Metal oxide nanoparticles (NPs) are particularly notable for their wide range of medicinal uses, including antibacterial, anticancer, biosensing, cell imaging, and drug/gene delivery. Among these, zinc oxide (ZnO) NPs stand out for their versatility and effectiveness. Recently, ZnO NPs have become a primary material in various sectors, such as pharmaceutical, cosmetic, antimicrobials, construction, textile, and automotive industries. ZnO NPs can generate reactive oxygen species and induce cellular apoptosis, thus underpinning their potent anticancer and antibacterial properties. To meet the growing demand, numerous synthetic approaches have been developed to produce ZnO NPs. However, traditional manufacturing processes often involve significant economic and environmental costs, prompting a search for more sustainable alternatives. Intriguingly, biological synthesis methods utilizing plants, plant extracts, or microorganisms have emerged as ideal for producing ZnO NPs. These green production techniques offer numerous medicinal, economic, environmental, and health benefits. This review highlights the latest advancements in the green synthesis of ZnO NPs and their biomedical applications, showcasing their potential to revolutionize the field with eco-friendly and cost-effective solutions.

Emerging ZnO Semiconductors for Photocatalytic CO2 Reduction to Methanol

Carbon recycling is poised to emerge as a prominent trend for mitigating severe climate change and meeting the rising demand for energy. Converting carbon dioxide (CO2) into green energy and valuable feedstocks through photocatalytic CO2 reduction (PCCR) offers a promising solution to global warming and energy needs. Among all semiconductors, zinc oxide (ZnO) has garnered considerable interest due to its ecofriendly nature, biocompatibility, abundance, exceptional semiconducting and optical properties, cost-effectiveness, easy synthesis, and durability. This review thoroughly discusses recent advances in mechanistic insights, fundamental principles, experimental parameters, and modulation of ZnO catalysts for direct PCCR to C1 products (methanol). Various ZnO modification techniques are explored, including atomic size regulation, synthesis strategies, morphology manipulation, doping with cocatalysts, defect engineering, incorporation of plasmonic metals, and single atom modulation to boost its photocatalytic performance. Additionally, the review highlights the importance of photoreactor design, reactor types, geometries, operating modes, and phases. Future research endeavors should prioritize the development of cost-effective catalyst immobilization methods for solid-liquid separation and catalyst recycling, while emphasizing the use of abundant and non-toxic materials to ensure environmental sustainability and economic viability. Finally, the review outlines key challenges and proposes novel directions for further enhancing ZnO-based photocatalytic CO2 conversion processes.

Improvement of the optical, photocatalytic and antibacterial properties of ZnO semiconductor nanoparticles using different pepper aqueous extracts

Peppers are fruits that grow on plants of the genus Capsicum and are popular for their use in gastronomy as a condiment and for their anti-inflammatory and anti-cancer properties due to their phytocompounds such as flavonoids, polyphenols, or alkaloids. Semiconductor zinc oxide (ZnO) nanoparticles (NPs) were synthesized using a green approach employing natural aqueous extracts of several varieties of peppers (jalapeño, morita, and ghost). The obtained NPs were characterized by different techniques, and their photocatalytic and antibacterial activity was studied. The signal at 620 cm-1 in the FTIR spectra belonging to the Zn-O bond, the appearance of the main peaks of a hexagonal wurtzite structure in the XRD pattern, and the characteristic signals in the UV-Vis spectra confirm the correct formation of ZnO NPs. The photocatalytic activity was analyzed against Methylene Blue (MB), Rhodamine B (RB), and Methyl Orange (MO) under UV and sunlight. All syntheses were able to degrade more than 93% of the pollutants under UV light. Antibacterial assays were performed against gram-positive and gram-negative bacteria. All syntheses exhibited antibacterial activity against all bacteria and maximum growth inhibition against Bacillus subtilis. The prominent results demonstrate that natural aqueous extracts obtained from peppers can be used to synthesize ZnO NPs with photocatalytic and biomedical applications.

Investigating of transition state on the Pd-Au decorated ZnO nanoparticle layers for gas sensor application

In this work, the mechanism of the transition state of electron transfer reaction on the surface of the ZnO nanoparticles-based gas sensor has been investigated. The deposited ZnO nanoparticles thick films on glass slides had been synthesized by the current heating method and modified its surface by coating novel metals of gold and palladium with a sputtering technique with different sputtering times of 45-180 s. Field emission electron microscopy (FE-SEM), x-ray diffraction spectroscopy (XRD), and energy dispersive spectroscopy (EDS) were used for the characterization of ZnO nanoparticle thick films. After that, the reflectance spectra of films were investigated using Near-IR spectroscopy in the range of 900-2500 nm to study the surface absorption efficiency. The decrease in reflectance spectra was observed for conditions over 90 s of sputtering time. The particle size distribution and zeta potential of ZnO nanoparticles were analyzed using the dynamic light scattering technique for the calculation of particle size and the electrical charge potential. The results showed that the size particle distribution ranged from 155 to 245 nm and the more extensive range of 360-1100 nm. The optimized zeta potential of -14.44 mV was exhibited at the sputtering time of 45 s. Finally, the gas sensing mechanism in terms of surface charge density was proposed and used to explain the sensitivity enhancement of both resistive and capacitive gas sensors.

Nanofibrous composite membranes based on chitosan-nano zinc oxide and curcumin for Kyoho grapes preservation

Nanofibrous composite membranes consisting of polyvinyl alcohol (PVA), sodium alginate (SA), chitosan-nano zinc oxide nanoparticles (CS-Nano-ZnO) and curcumin (Cur) were prepared by ultrasonic processing and electrospinning. When the ultrasonic power was set to 100 W, the prepared CS-Nano-ZnO had a minimum size (404.67 ± 42.35 nm) and a generally uniform particle size distribution (PDI = 0.32 ± 0.10). The composite fiber membrane with Cur: CS-Nano-ZnO mass ratio of 5:5 exhibited the best water vapor permeability, strain and stress. Furthermore, the inhibitory rates against Escherichia coli and Staphylococcus aureus were 91.93 ± 2.07 % and 93.00 ± 0.83 %, respectively. The Kyoho grape fresh-keeping trial revealed that grape berries wrapped with composite fiber membrane still maintained good quality and a higher rate of good fruit (60.25 ± 1.46 %) after 12 days of storage. The shelf life of grape was extended by at least 4 days. Thus, nanofibrous composite membranes based on CS-Nano-ZnO and Cur was expected to be used as an active material for food packaging.

Transformation of used aluminium foil food container into AlOOH nanoflakes with high catalytic activity in anionic azo dye reduction

Synthesis of aluminium-based nanomaterials from aluminium-waste has received huge attention in current scientific research. Herein, an attempt was made to convert aluminium foil food container into aluminium oxyhydroxide (AlOOH) nanoparticles by a precipitation method. X-ray diffraction (XRD), spectroscopic and electron microscopic studies were employed to characterize impure AlOOH (containing sodium chloride, NaCl) and pure AlOOH samples. The band gap (E_g) of AlOOH nanoparticles was found to be 4.5 eV. The catalytic potential of AlOOH samples was evaluated using reduction of methyl orange (MO) and Eriochrome black T (EBT) dyes. Impure AlOOH nanoparticles could reduce 99.8% of MO and EBT dye within 4 min and 3 min respectively. Effect of the AlOOH dosage and NaBH₄ concentration on catalytic reduction was determined. Used aluminium foil food container-derived AlOOH nanoparticles will become a low-cost and sustainable catalyst in the catalytic treatment of azo dye contaminated waters.

Influence of the Alcohols on the ZnO Synthesis and Its Properties: The Photocatalytic and Antimicrobial Activities

Zinc oxide (ZnO) nanomaterials are used in various health-related applications, from antimicrobial textiles to wound dressing composites and from sunscreens to antimicrobial packaging. Purity, surface defects, size, and morphology of the nanoparticles are the main factors that influence the antimicrobial properties. In this study, we are comparing the properties of the ZnO nanoparticles obtained by solvolysis using a series of alcohols: primary from methanol to 1-hexanol, secondary (2-propanol and 2-butanol), and tertiary (tert-butanol). While the synthesis of ZnO nanoparticles is successfully accomplished in all primary alcohols, the use of secondary or tertiary alcohols does not lead to ZnO as final product, underlining the importance of the used solvent. The shape of the obtained nanoparticles depends on the alcohol used, from quasi-spherical to rods, and consequently, different properties are reported, including photocatalytic and antimicrobial activities. In the photocatalytic study, the ZnO obtained in 1-butanol exhibited the best performance against methylene blue (MB) dye solution, attaining a degradation efficiency of 98.24%. The comparative study among a series of usual model dyes revealed that triarylmethane dyes are less susceptible to photo-degradation. The obtained ZnO nanoparticles present a strong antimicrobial activity on a broad range of microorganisms (bacterial and fungal strains), the size and shape being the important factors. This permits further tailoring for use in medical applications.

Hydrothermal Synthesis of Zinc Oxide Nanoparticles Using Different Chemical Reaction Stimulation Methods and Their Influence on Process Kinetics

The aim of this work was to study the effect of the applied chemical reaction stimulation method on the morphology and structural properties of zinc oxide nanoparticles (ZnONPs). Various methods of chemical reaction induction were applied, including microwave, high potential, conventional resistance heater and autoclave-based methods. A novel, high potential-based ZnONPs synthesis method is herein proposed. Structural properties-phase purity, grain size-were examined with XRD methods, the specific surface area was determined using BET techniques and the morphology was examined using SEM. Based on the results, the microwave and autoclave syntheses allowed us to obtain the desired phase within a short period of time. The impulse-induced method is a promising alternative since it offers a non-equilibrium course of the synthesis process in an highly energy-efficient manner.

Green Facile Synthesis of Silver-Doped Zinc Oxide Nanoparticles and Evaluation of Their Effect on Drug Release

Silver doped zinc oxide nanoparticles (ZANPs) were synthesized by the gelatin mediated and polymerized sol-gel method, and a calcination temperature of 700 °C was applied for 2 h. X-ray diffraction (XRD), FESEM, TGA, DSC, and EDS were performed to study the structure of the prepared nano-powders. Both cubic silver and hexagonal ZnO diffraction peaks were detected in the XRD patterns. The XRD results, analyzed by the size strain plot (SSP) and Scherrer methods, showed that the crystalline sizes of these nanoparticles increased as the Ag concentration increased. The results were observed via transition electron microscopy (TEM), where the particle size of the prepared samples was increased in the presence of silver. Catechin was chosen as a drug model and was loaded into the hydrogels for release studies. The drug content percentage of catechin in the hydrogels showed a high loading of the drug, and the highest rate was 98.59 ± 2.11%, which was attributed to the Zn0.97Ag0.03O hydrogels. The swelling of the samples and in vitro release studies were performed. The results showed that Zn0.91Ag0.09O showed the highest swelling ratio (68 ± 3.40%) and, consequently, the highest release (84 ± 2.18%) within 300 min. The higher amount of silver ions in the hydrogel structure causes it to enhance the osmotic pressure of the inner structure and increases the relaxation of the structure chain.

UV-irradiated sol-gel spin coated AZO thin films: enhanced optoelectronic properties

Thin films of transparent conductive Al doped ZnO (AZO) thin films were produced via sol-gel spin coating route. Structural, optical, and electrical properties were explored for several dopant concentrations. Formation of crystalline AZO was verified by X-ray Diffraction (XRD) Analysis and structural analysis were carried out later from the XRD data. Highest band gap of 3.67 eV was found for 2 mol % AZO thin films. The average transmittance was found to be 84.19% in the visible spectra for the corresponding thin films. 2 mol% AZO also exhibited a minimum resistivity of 2.05 Ω-cm with a maximum value of figure of merit. Prolonged UV irradiation was applied to 2 mol % AZO thin films prior to annealing. It significantly modified the surface morphology of the film and provided shielding near UVA (315–378 nm) spectrum. This also enhanced the conductivity of the thin film by 3-fold compared to non-UV treated sample and decreased optical band gap significantly.

Review on Sol-Gel Synthesis of Perovskite and Oxide Nanomaterials

Sol-Gel is a low cost, well-established and flexible synthetic route to produce a wide range of micro- and nanostructures. Small variations in pH, temperature, precursors, time, pressure, atmosphere, among others, can lead to a wide family of compounds that share the same molecular structures. In this work, we present a general review of the synthesis of LaMnO3, SrTiO3, BaTiO3 perovskites and zinc vanadium oxides nanostructures based on Sol-Gel method. We discuss how small changes in the parameters of the synthesis can modify the morphology, shape, size, homogeneity, aggregation, among others, of the products. We also discuss the different precursors, solvents, working temperature, reaction times used throughout the synthesis. In the last section, we present novel uses of Sol-Gel with organic materials with emphasis on carbon-based compounds. All with a perspective to improve the method for future applications in different technological fields.