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An Eco-friendly Approach to ZnO NP Synthesis Using Citrus reticulata Blanco Peel/Extract: Characterization and Antibacterial and Photocatalytic Activity
No full textEmission of greenhouse gases and infectious diseases caused by improper agro-waste disposal has gained significant attention in recent years. To overcome these hurdles, agro-waste can be valorized into valuable bioactive compounds that act as reducing or stabilizing agents in the synthesis of nanomaterials. Herein, we report a simple circular approach using Citrus reticulata Blanco (C. reticulata) waste (peel powder/aqueous extract) as green reducing and capping/stabilizing agents and Zn nitrate/acetate precursors to synthesize ZnO nanoparticles (NPs) with efficient antimicrobial and photocatalytic activities. The obtained NPs crystallized in a hexagonal wurtzite structure and differed clearly in their morphology. UV-vis analysis of the nanoparticles showed a characteristic broad absorption band between 330 and 414 nm, belonging to ZnO NPs. Fourier transform infrared (FTIR) spectroscopy of ZnO NPs exhibited a Zn–O band close to 450 cm−1. The band gap values were in the range of 2.84-3.14 eV depending on the precursor and agent used. The crystallite size obtained from size-strain plots from measured XRD patterns was between 7 and 26 nm, with the strain between 16 and 4%. The high crystalline nature of obtained ZnO NPs was confirmed by clear ring diffraction patterns and d-spacing values of the observed lattice fringes. ZnNPeelMan_400 and ZnNExtrMan have shown good stability as the Zeta potential was found to be around -20 mV and reduced particle aggregation. Photoluminescence analysis revealed different defects belonging to oxygen vacancies (VO+ and VO++) and zinc interstitial (Zni) sites. The presence of oxygen vacancies on the surface of ZnAcExtrMan_400 and ZnAcPeelMan_400 increased antimicrobial activity, specifically against gram-negative bacteria Escherichia coli (E.coli) and Salmonella enteritidis (S. enteritidis). ZnNextrMan with a minimal inhibitory concentration of 0.156 mg/ml was more effective against gram-positive bacteria, Staphylococcus aureus (S. aureus) revealing a high influence of particle size and shape on antimicrobial activity. In addition, the photocatalytic activity of the ZnO NPs was examined by assessing the degradation of acid green dye in an aqueous solution under UV light irradiation. ZnAcPeelMan_400 exhibited excellent photocatalytic activity (94%) within 90 minutes after irradiation compared to other obtained ZnO NPs
Variability of Morpho-Anatomical Characteristics of Different Willow Clones Contaminated with Heavy Metals
Get PDFIn this paper, the variability of morphological (stem height, stem basal diameter, proportion of pith, wood and bark) and wood anatomical characteristics (fiber length, fiber diameter, fiber lumen diamater, double cell-wall thickness, vessel diameter, wood rays width and height) of three Salix alba clones (B-44, 347 and NS 73/6) and one Salix viminalis clone both in the control plot and in the site contaminated with a mixture of heavy metals (As, Cd, Cr, Cu, Ni, Pb) was investigated. The observed results showed that individuals of all four clones had significantly higher average values of stem height and stem basal diameter at the control plot compared to the polluted site. As for the proportion of pith, bark and wood, heavy metals caused an increase in the share of pith and a decrease in the share of bark and wood in all clones with the exception of clone NS 73/6. The analysis of wood fiber dimensions showed that the values of all parameters were higher at the control site with the exception of fiber lumen diameter where higher values were observed for clones B-44 and NS 73/6 at the polluted site. Higher values of vessel diameter were recorded for all clones at the control plot, while wood rays width of all individuals was greater at the contaminated site. Regarding the wood rays height, only Salix viminalis showed higher value at the polluted site. These results confirmed that pollution-induced heavy metal stress significantly altered the morphological and wood anatomical characteristics of all researched clones and that it may affect their utility properties
Dimensionality crossover of radial discrete diffraction in optically induced Mathieu photonic lattices
No full textWe demonstrate transitional dimensionality crossover of radial discrete diffraction in optically induced radial-elliptical Mathieu photonic lattices. Varying the order, characteristic structure size, and ellipticity of the Mathieu beams used for the photonic lattices generation, we control the shape of discrete diffraction distribution over the combination of the radial direction with the circular or elliptic. We also investigate the transition from one-dimensional to two-dimensional discrete diffraction by varying the input probe beam position. Discrete diffraction is the most pronounced along the crystal anisotropy direction
Encapsulation of Active Components in Chitosan and Pectin for Application in Antimicrobial Food-Packaging
No full textThe main objective of this research was to develop stable encapsulation systems based on natural biopolymers (chitosan, pectin and gelatin) into which different types of active ingredients (lemongrass essential oil, ZnO nanoparticles) can be incorporated to ensure their stability and controlled release over time. Various formulations of biopolymer dispersions and oil-in-water emulsions were developed. The emulsions were prepared by dispersing lemongrass essential oil in biopolymer solutions (chitosan-gelatin or pectin-gelatin). The influence of the polysaccharide-protein biopolymer complexes on the stability and slow release of the encapsulated lemongrass essential oil was studied. Biopolymer films were prepared from emulsions and dispersions by casting method. AFM and SEM /EDS analyses showed a homogeneous distribution of lemongrass essential oil and ZnO nanoparticles in the biopolymer films. The antimicrobial activity of the emulsions and dispersions was investigated in vitro against bacterial species characteristic of food spoilage. Biopolymer coatings were formed by spraying emulsions onto existing packaging and tested in vivo on fresh raspberries as antimicrobial food packaging
Exploring noble metal modifications: enhanced electrocatalytic activity of cobalt and nickel electrodes in alkaline environments
No full textThis research focuses on the development and comprehensive analysis of novel electrocatalysts for energy conversion applications, particularly for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. We investigated the electrocatalytic activity of nickel and cobalt electrodes modified with noble metals such as rhodium, ruthenium, iridium, and platinum. Modified polycrystalline electrodes were prepared via facile galvanic displacement from a highly concentrated acidic solution of noble metals. Our findings show that nickel-based electrodes, especially those modified with rhodium and platinum, demonstrate superior performance, making them promising candidates for alkaline water electrolysis. Because of its high efficiency, we investigated further the rhodium-modified nickel polycrystalline electrodes. This surface modification led to a significant enhancement in both HER and OER activities, although hydrogen oxidation (HOR) and oxygen reduction reaction (ORR) activities were reduced compared to those of polycrystalline platinum. The presence of semiconducting Rh2O3 was found to adversely affect HOR and ORR performance, while metallic Rh and conductive RhO2 were beneficial for the HER and OER. The research further elucidates the mechanisms underlying the enhanced electrode kinetics on these Rh-modified nickel electrodes and highlights the role of rapid galvanic changes in improving electrocatalytic activity. Overall, the studies provide insights into engineering advanced, efficient, and cost-effective electrocatalysts for clean energy applications, critical for achieving energy security in modern society
Effects of chemical activation on properties and hydration mechanism of high volume fly ash binders
No full textProperties and hydration mechanism of high volume fly ash (HVFA) binders, comprising 70 wt.% of fly ash (FA) and 30 wt.% of Portland cement (PC), and chemically activated with several different activators (sodium carbonate, sodium sulphate, sodium silicate, sodium oxalate, and calcium formate) were investigated. Effects of the activators were examined by analysing setting times, compressive strength, heat of hydration, pore solution composition, portlandite and bound water content, microstructure and mineral composition of binders. It was found that the use of activators accelerated PC hydration and led to an earlier start of pozzolanic reaction in HVFA binders. Consequently, setting times of the chemically activated binders were shorter, and early compressive strengths (during the first 7 days) were higher. However, 28-day and 90-day compressive strengths of the activated binders were lower than the strengths of the binder synthesized without an activator, which could be attributed to a higher amount of hydration products formed during the first few days of curing, which hindered further reactions. Negative effects of the chemical activation of HVFA binders were less pronounced in binders activated with sodium silicate and calcium formate
Freeze-thaw, carbonation and sulfate attack resistance of high volume fly ash binders
No full textDurability of high volume fly ash (HVFA) binders, that contained ≥ 50 wt.% of fly ash (FA), was analysed. In order to increase the amount of FA in the binder and to improve early age properties of the HVFA binder, mechanical activation of FA was done and a chemical activator was used for the binder synthesis. Freeze-thaw, carbonation and sulfate attack resistance of the HVFA binders were investigated.
It was found that the HVFA binder fulfilled the standard quality requirements regarding freeze-thaw resistance. After 25 freeze-thaw cycles, compressive strength of the tested samples was 88 % of the strength of the reference sample.
Carbonation depth was 4.6 – 6.3 μm after 28 days and 7.3 – 8.1 μm after 56 days of testing of the HVFA binders. An increase in the compressive strength of the HVFA binder has been observed after 56 days of exposure to the CO2 environment.
Sulfate attack on the HVFA binders has been examined by exposing the binder samples to Na2SO4 and MgSO4 solutions. Resistance of the HVFA binder to the Na2SO4 solution attack was good and even superior to the performance of Portland composite cement CEM II tested under the same conditions. After 6 months of testing the HVFA binder in MgSO4 solution some deterioration at the edges of the samples and a decrease in compressive strength were observed and they were attributed to formation of magnesium-silicate-hydrate.
Based on the obtained results it was concluded that the HVFA binders could be used in applications where good durability of a construction material was expected
USE OF FAST-GROWING WILLOW CLONES FOR PHYTOREMEDIATION OF LANDS CONTAMINATED WITH HEAVY METALS
Get PDFПроблема загрязнения окружающей среды соединениями тяжелых металлов является одной из наиболее значимых, так как загрязнители могут интенсивно накапливаться в произведенной продукции. Одним из направлений решения является метод фиторемедиации или использование растений. Полученная с загрязненных территорий биомасса не может использоваться как продовольствие или корм, но пригодна для технических или энергетических целей. Представленные в публикации исследования направлены на оценку эффективности использования быстрорастущих клонов ивы для фиторемедиации загрязненных тяжелыми металлами почв.The problem of environmental pollution with heavy metal compounds is one of the most significant, since pollutants can intensively accumulate in food products. One of the solutions is the phytoremediation method or the use of plants. The biomass obtained from contaminated areas cannot be used as food or feed, but is suitable for technical or energy purposes. The studies presented in the publication are aimed at assessing the effectiveness of using fast-growing willow clones for phytoremediation of the soils contaminated with heavy metals
Lead-free flexible composite films: properties and potential application
No full textVarious forms of mechanical energy in the surrounding environment offer a valuable resource for piezoelectric energy harvesting. This technology enables the conversion of mechanical stress into electrical energy. The application can be wide-ranging, particularly in low-power devices that require autonomous energy sources. The most successful approach to preparing flexible electronics involves combining functional piezoelectric components with a highly flexible polymer matrix. The main strategy here is to combine the benefits of both materials, polymers' high breakdown strength with excellent piezoelectric properties and dielectric permittivity of the ceramics by preparing ceramic/polymer flexible composites. Driven by concerns over the ecological impact, the chosen piezoelectric material must be lead-free which makes a 0.94[(Bio.sNao.s)Ti03]-0.06BaTi03 (NBT-BT) a good candidate for this purpose. The selected polymer, polyvinylidene difluoride- PVDF, besides the flexibility, will enhance the material's piezoelectric properties [1,2]. Flexible composite films, NBT-BT/PVDF, were prepared by the hot pressing method. The influence of the hot pressing method on the formation of electro-active PVDF phases in the polymer was proven by the FTIR analysis. DSC analysis has shown the change in PVDF crystallinity degree with the addition of ceramic filler particles. The relative dielectric constant of the flexible composites increased from 10 of pure PVDF polymer to 110 of composite films with 50 vol% NBT-BT content, while the piezoelectric d33 constant increased from 0.2 pC/N to 33 pC/N for the same samples, at ultrasound frequencies. Energy harvesting potential was studied by measuring the voltage output under the impulse hammer load. Additionally, the improvement of properties has been investigated through various approaches in film processing [2,3]
Acaricidal Activity of Essential Oil of Satureja montana L. against Dermanyssus gallinae In Vitro Conditions
No full textDermanissus gallinae, commonly known as the poultry red mite, causes great damage in the poultry industry. Plant-derived acaricides offer a strong alternative to chemical acaricides in the control of ectoparasites such as D. gallinae (Radsetoulalova et al., 2020; Ratajac et al. 2024). The aim of this study was to investigate the acaricidal activity of essential oil (EO) Satureja montana L. from the Balkan Peninsula and to evaluate their potential and limitations to be included in formulations for rational control of D. gallinae in the poultry industry. The chemical profile of EO was analyzed by gas chromatography coupled with mass spectrometry. The acaricidal efficacy of EO (0.1; 0.3; 0.5; 1; 3; 5 and 6% concentration) was tested on adult mites using the Petri-dish method, through direct exposure for 1 minute (contact toxicity) and subsequent exposure for 1 hour (residual toxicity). The EO efficiency ranged, in direct exposure-contact, after 48 hours of observation, from 3 to 100% toxicity, depending on the tested concentration, while the residual effect were negligible. George et al. (2010) also demonstrated efficacy after 24h exposure as 77.80% for S. montana L. Thus, the results of the present and other studies suggest a strong effect of EO against D. gallinae through direct
contact and absence of prolonged effect. Plant based formulations are most likely less susceptible to resistance
development and more acceptable in terms of the residues in animal products and the environment in
comparison with chemicals (Abbas et al., 2018)