Search Results (224)

A simple and rapid precipitation process was successfully employed to prepare silver phosphate (SP, Ag₃PO₄). Two different phosphate sources: diammonium hydrogen phosphate ((NH₄)₂HPO₄) and dipotassium hydrogen phosphate (K₂HPO₄) were applied separately as the precursor, obtaining ((NH₄)₂HPO₄)⁻ and K₂HPO₄⁻ derived SP powders, named SP-A or SP-P, respectively. Fourier transform infrared (FTIR) spectra pointed out the vibrational characteristics of P–O and O–P–O interactions, confirming the presence of the PO43– functional group for SP. X-ray diffraction (XRD) patterns revealed that the SP crystallized in a cubic crystal structure. Whereas the field emission scanning electron microscope (FESEM) exposed spherical SP particles. The potentially antibacterial activity of SP-A and SP-P against bacterial Bacillus stratosphericus, yeast Meyerozyma guilliermondii, and fungal Phanerodontia chrysosporium was subsequently investigated. All studied microorganisms were recovered and isolated from the aquatic plant during the tissue culture process. The preliminary result of the antimicrobial test revealed that SP-A has higher antimicrobial activity than SP-P. The superior antimicrobial efficiency of SP-A compared to SP-P may be attributed to its purity and crystallite size, which provide a higher surface area and more active sites. In addition, the presence of potassium-related impurities in SP-P could have negatively affected its antimicrobial performance. These findings suggest that SP holds potential as an antimicrobial agent for maintaining sterility in tissue cultures, particularly in aquatic plant systems. The growth of both B. stratosphericus and M. guilliermondii was suppressed effectively at 30 ppm SP-A, whereas 10 ppm of SP-A can suppress P. chrysosporium development. This present work also highlights the potential of SP at very low concentrations (10–30 ppm) for utilization as an effective antimicrobial agent in tissue culture, compared to a commercial antimicrobial agent, viz., acetic acid, at the same concentration. Full article

In the present study, for the first time, a biodegradable and non-toxic polyphosphoramidate glycohydrogel (PPAGHGel) was prepared by crosslinking a polyphosphoramidate glycoconjugate (PPAG) with hexamethylene diisocyanate (HMDI) under mild conditions. Poly(oxyethylene H-phosphonate) (POEHP) was used as a precursor and was converted into PPAG via the Staudinger reaction with glucose-containing azide (2-p-azidobenzamide-2-deoxy-1,3,4,6-tetra-O-trimethylsilyl-α-D-glucopyranose). Then, crosslinking of PPAG was performed to yield PPAGHGel, which was thoroughly characterized. The gel showed a gel fraction of 83%, a swelling degree of 1426 ± 98%, and G″ = 1560 ± 65 Pa. The gel was fully degraded by alkaline phosphatase (400 U/L, pH 9) in 19 days, while hydrolytically, up to 52% degradation was observed under similar conditions. Multivalent studies of the obtained hydrogel with lectin–Concanavalin A were performed. PPAGHGel binds 92% of Concanavalin A within 24 h and the complex remains stable until the amount of glucose reaches 0.3 mM. PPAGHGel acts as a stabilizer for silver nanoparticles (12 nm). SEM shows pores measuring 10 µm (surface) and 0.1 mm (interior) with capillary channels, confirming the gel’s suitability for biosensors, drug delivery, or wound dressings. The cytotoxic (IC50) and cell-adhesive properties of the obtained hydrogel were investigated on human cell lines (HeLa). Antibacterial activity tests were also performed with gel containing silver nanoparticles against skin-associated pathogenic bacteria. The results show that PPAGHGel possesses excellent biocompatibility, non-adhesive properties and antibacterial activity. Full article

A ceramic–metal composite was synthesized using sol–gel and electrospinning methods to serve as a SERS substrate. The precursors used were tetraethyl orthosilicate, aluminum nitrate, and zirconium, and polyvinylpyrrolidone was added to electrospun nonwoven fibrous membranes. The membranes were sintered, decorated with silver nanoparticles. The enhancement substrates were made of fibers of cylindric morphology with an average diameter of approximately 190 nm, a smooth surface, and 9 nm spherical particles decorating the surface of the fibers. The enhancement capacity of the substrates was tested using pyridine, methyl orange, methylene blue, crystal violet, and Eriochrome black T at different concentrations with Raman spectroscopy to determine whether the size and complexity of the analyte has an impact on the enhancement capacity. Enhancement factors of 2.53 × 10², 3.06 × 10¹, 2.97 × 10³, 4.66 × 10³, and 1.45 × 10³ times were obtained for the signal of pyridine, methyl orange, methylene blue, crystal violet, and Eriochrome black T at concentrations of 1 nM. Full article

The use of plasmonic nanoparticles for biosensor technology is dependent on nanoparticle size and morphology. This study determined the effect of pH and pressure on synthesizing silver nanoparticle size. In Method 1, a mixture of NaBH₄ and sodium citrate was added to a solution of AgNO₃ monodispersed by ultrasound energy. In Method 2, the reducer was added to the precursor–dispersant mixture solution. The effect of pH was evaluated by using buffer solutions at pH 4.0, pH 7.0, and pH 10.0 and water as control. To determine the effect of pressure, AgNPs were subjected to 0, 4, and 23 h to 1.75 MPa at 200 °C. AgNPs produced with Method 1 showed a more symmetric SPR and a smaller nanoparticle diameter (±6 nm). The SPR with Method 1 at pH 10.0 produced a higher UV peak with a shift around 20 nm. In the case of the pressure treatment, a shift of approximately 20 nm was observed at all time conditions studied, and a higher AgNP diameter was found in contrast to Method 1. Finally, EDX and Raman analysis confirm the presence of AgNPs and a mild oxidation of these. These results suggest that alkalinity and pressure can affect the diameter of AgNPs. Full article

Materials derived from metal–organic frameworks (MOFs) as MOF-derived oxides retain a highly porous and active structure from the MOF precursor, exhibiting excellent sensing properties. In addition, the tunable nature of MOFs allows the structural and chemical properties of the resulting oxides to be specifically tuned to enhance their performance as sensing materials. In this work, zinc-based MOF structures belonging to the family of zeolitic imidazolate frameworks (ZIFs) were synthesized, characterized and then subjected to a high-temperature calcination process to obtain the corresponding oxides. To improve sensing performance, various silver doping strategies (1 wt.%) were explored, specifically through a growth process and an impregnation process. Among these approaches, the oxide obtained via the growth process demonstrates superior performance, exhibiting a response 5.8 times higher than pristine ZnO when exposed to 80 ppm of ethanol at 300 °C in a humidity-controlled chamber. These results highlight the potential of silver doping via growth process as an effective strategy to enhance the sensing performance of MOF-derived ZnO. Full article

Silver nanostructures exhibit exceptional surface-enhanced Raman scattering (SERS) performance due to their strong plasmonic resonance. However, their practical applications are often hindered by structural instability, leading to deformation and performance degradation. In this study, we developed a kinetics-controlled synthetic strategy to fabricate gold-encapsulated silver (Au@Ag) hierarchical superstructures (HSs) with enhanced SERS activity and stability. By leveraging polyvinylpyrrolidone (PVP) as a surface modifier and precisely regulating the introduction rate of reaction precursors, we achieved meticulous control over the galvanic replacement kinetics, thereby preserving the structural integrity of pre-synthesized Ag HSs during the formation of Au@Ag HSs. The resulting well-defined Au@Ag HSs demonstrated superior SERS performance, achieving a detection limit of 10⁻⁹ M for crystal violet (CV) while exhibiting outstanding signal reproducibility (relative standard deviation, RSD = 11.60%). This work provides a robust and scalable approach to designing stable, high-efficiency SERS-active nanostructures with broad potential in analytical and sensing applications. Full article

A new active composite film intended for bread packaging is described here. The active film has the aim of prolonging bread’s shelf life while avoiding the use of nanoparticles that, with very few exceptions, are a type of material not allowed by regulatory agencies like EFSA (European Food Safety Agency) and FDA (US Food and Drug Administration) in food contact materials. Moreover, the increasing consumer demand for natural and wholesome products, possibly “clean label”, and packaged in natural, non-petroleum-based materials has been taken into consideration. Accordingly, precursor materials from renewable sources were used to prepare the active film: pectin from citrus peel (PEC) and carboxymethyl cellulose (CMC) were used as the matrix, with oleic acid (OA) as plasticizer. Moreover, the bread preservative calcium propionate (CaP) was used as the crosslinker, and also zeolite microparticles loaded with silver ions (AgZ) were added to the films as an additional antimold agent. This strategy allows us to avoid the addition to bread of the now commonly used preservatives ethanol and calcium propionate, moving the latter to the packaging. Permeance measurements revealed excellent barrier properties against O₂ and CO₂, while the typical high water vapor permeance of polysaccharide films was mitigated by the non-hydrophilic OA plasticizer. Moreover, the quantities of Ag⁺ and CaP released in bread are low and below the limits imposed by regulatory agencies. The antimold activity of the films is excellent, with Aspergillus niger, Penicillium janthinellum, and wild-type Penicillim molds reduction on bread in the 99.20–99.95% range for the films containing only CaP and in the 99.97–99.998% range for the films containing both CaP and AgZ. Finally, the rheological properties of the film-forming solutions were investigated, demonstrating their potential application as coatings on natural packaging materials for bread, such as paper. Full article

Numerous mineral microinclusions discovered in the Triassic Ildeus mafic–ultramafic intrusion are dominated by base metal sulfides, gold, silver, and their alloys, as well as rare earth element (REE) minerals. These mineral microinclusions were formed through both the magmatic differentiation of the Ildeus intrusion and the multi-stage interaction of intrusive rocks with late-magmatic, post-magmatic and post-collisional fluids. A comparison of the results of our microinclusions study with ore mineralization discovered within the Ildeus intrusion suggests that microinclusion assemblages in igneous rocks are, in some cases, precursors of potentially economic mineralization. In the case of the Ildeus rocks, sulfide microinclusions correspond to potentially economic disseminated nickel–cobalt sulfide ores, while microinclusions of gold and its alloys correlate with intrusion-hosted, erratic gold mineralization. The occurrence of silver and rare earth element minerals in Ildeus plutonic rocks indicates the possible presence of silver and REE mineralization, which is supported by sub-economic whole-rock silver and REE grades in parts of the Ildeus intrusion. The results of our investigation suggest that studies of mineral microinclusions in magmatic rocks may be useful in the evaluation of their metallogenic specialization and ore-forming potential and could possibly be utilized as an additional prospecting tool in the regional exploration for precious, base, and rare metals. Full article

Copper nanowires (Cu NWs) are considered a promising alternative to indium tin oxide (ITO) and silver nanowires (Ag NWs) due to their excellent electrical conductivity, mechanical properties, abundant reserves, and low cost. They have been widely applied in various optoelectronic devices. In this study, Cu NWs were synthesized using copper chloride (CuCl₂) as the precursor, monoethanolamine (MEA) as the complexing agent, and hydrated hydrazine (N₂H₄) as the reducing agent under strongly alkaline conditions at 60 °C. Notably, this is the first time that MEA has been employed as a complexing agent in this synthesis method for Cu NWs. Through a series of experiments, the optimal conditions for the CuCl₂–MEA–N₂H₄ system in Cu NWs synthesis were determined. This study revealed that the presence of amines plays a crucial role in nanowire formation, as the co-ordination of MEA with copper in this system provides selectivity for the nanowire growth direction. MEA prevents the excessive conversion of Cu(I) complexes into Cu₂O octahedral precipitates and exhibits an adsorption effect during Cu NWs formation. The different adsorption tendencies of MEA at the nanowire ends and lateral surfaces, depending on its concentration, influence the growth of the Cu NWs, as directly reflected by changes in their diameter and length. At an MEA concentration of 210 mM, the synthesized Cu NWs have an average diameter of approximately 101 nm and a length of about 28 μm. To fabricate transparent conductive films, the Cu NW network was transferred onto a polyethylene terephthalate (PET) substrate by applying a pressure of 20 MPa using a tablet press to ensure strong adhesion between the Cu NW-coated mixed cellulose ester (MCE) filter membrane and the PET substrate. Subsequently, the MCE membrane was dissolved by acetone and isopropanol immersion. The resulting Cu NW transparent conductive film exhibited a sheet resistance of 52 Ω sq⁻¹ with an optical transmittance of 86.7%. Full article

Nowadays, there is a growing need to develop environmentally friendly procedures that reduce the use of toxic chemicals in synthesis. Green synthesis methods have an advantage over conventional chemical methods because they do not pollute the environment significantly. This has generated more interest in using readily available plants to create nanomaterials. In this work, silver nanoparticles were obtained through green chemistry using natural reducing agents present in apple extract. The research focused on optimizing the synthesis conditions to obtain predictable structures. The characterization of the nanoparticles was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), UV–Vis spectroscopy, and infrared spectroscopy (IR). The achieved results led to the conclusion that the use of apple extract was suitable for obtaining homogenous and spherical silver nanoparticles at a wide range of core precursor concentrations and a variable pH. The diameter of the studied nanoparticles ranged from 6 to 22 nm. The nanoparticles obtained with apple extract were highly active against Gram-positive bacteria and fungus, but less active against Gram-negative bacteria. The development of nanotechnology in green chemistry processes will gradually increase with technological advances, being a key component in developing new synthesis processes for nano-object formation. Full article

In this work, an analysis was made of the microstructural effects derived from the incorporation of silver (Ag) at different concentrations (0.5, 1, 2, 3, and 8% wt) to obtain ZnO-Ag nanocomposites. The results show an increase in the particle size of Ag in relation to the increase in the weight percentage of the precursor. ZnO-Ag is obtained through an infusion of Origanum vulgare as a reducing agent for Ag in the first stage. Subsequently, the solid-state method was used, resulting in the formation of Zinc Oxide (ZnO) and the ZnO-Ag nanoparticles (NPs). The physicochemical characterization was carried out using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and High-Resolution Transmission Electron Microscopy (HRTEM). The XRD results confirm the presence of Ag and ZnO. Ag shows a preferred orientation of [111] with a crystallite size ranging from 28.46 to 44.92 nm, which increases with the percentage of Ag in the system over ZnO. The wurtzite ZnO presents a preferential orientation of [101] with an increasing crystallite size from 24.9 to 29.84 nm. In the FTIR analysis, a stretching band at 682 cm⁻¹, characteristic of the Zn-O bond, as well as a strain vibration band at 457 cm⁻¹ of ZnO, were observed. The nanoparticle size is attributed to the phytochemical composition of Origanum vulgare, which includes secondary metabolites such as phenolic acids, flavonoids, terpenoids, and flavonoid-based reducing compounds. These compounds help reduce the agglomeration of the particles. Full article

The goal of this work was to prepare modified titanium dioxide catalysts applicable for self-cleaning and disinfecting surfaces, possessing both antibacterial and photocatalytic activity in the visible-light region, via green and affordable synthesis. For this purpose, silverization was chosen due to its antibacterial and electron-capturing effects, and to achieve efficient visible-light excitation, urea was used as a precursor for nitrogen doping. Mechanochemical activation with grinding, as an environmentally friendly process, was applied for the catalyst modification under various conditions, such as the amounts of the modifying substances, the milling time, the ratio of the weights of the material to be ground, and the grinding balls. The photocatalytic activity in the UV and visible range was tested in suspensions with oxalic acid and coumarin as model compounds. The antibacterial effect was measured by the bioluminescence of Vibrio fischeri bacteria. The highest photocatalytic activity in the visible range was observed with the nitrogen-doped titanium dioxide (N-TiO₂) prepared with 10% urea. Silveration of N-TiO₂ (up to 0.2%) decreased photocatalytic activity while improving the antibacterial efficiency. To maximize both effects, mechanical mixtures of the separately modified catalysts (N-TiO₂ and Ag-TiO₂) were also examined in different ratios. The 1:1 mixture provided the optimum combination. Full article

The cyclization of propargyl alcohols with CO₂ represents a highly significant method for the utilization of CO₂. The resulting cyclic carbonates possesses high chemical value and hold great potential for applications in battery electrolytes, polymer precursors, and pharmaceutical intermediates. However, most existing reports on this cyclization have been limited to simple propargyl alcohol substrates that are substituted with inert alkyl, cycloalkyl, and phenyl groups. For functionalized propargyl alcohols, such as alkyne-1,2-diols, only a single report has been documented thus far. In this study, we have developed an innovative catalytic system comprising cost-effective copper salts and environmentally friendly ionic liquids (CuCl/1-ethyl-3-methylimidazolium acetate) for the cyclization of alkyne-1,2-diols with CO₂. Compared to the previously reported AgF/bulky monophosphine ligand (BrettPhos) system, our system is free of traditional volatile solvents, phosphine ligands, and additives. Notably, this is the first reported Cu(I)-catalyzed system for this cyclization, offering significant advantages in terms of cost-effectiveness and reduced toxicity compared to silver salts. Moreover, the use of ionic liquids ensures considerable recyclability, further enhancing the sustainability and practicality of this approach. Full article

In this work, we present a low-cost, label-free cellulose-based paper SERS (Surface-Enhanced Raman Scattering) substrate for the sensitive detection of thiol compounds. Uniform silver nanoparticles (AgNPs) were synthesized on cellulose filter paper via in situ reduction of a silver precursor under UVC irradiation, achieving a high SERS enhancement factor of 8.5 × 10⁶. The Ag-cellulose substrate demonstrated reliable detection of benzenethiol, capturing its characteristic SERS signals with remarkable sensitivity. Quantitative analysis was enabled by adjusting exposure times for accurate calibration. Furthermore, Principal Component Analysis (PCA) was successfully employed to distinguish mixed samples of benzenethiol, hexanethiol, and propanethiol, showcasing the substrate’s capability in separating complex mixtures. This cellulose-based AgNP platform offers a sustainable, cost-effective solution for rapid chemical detection, with significant potential for real-world applications such as environmental monitoring and food safety. Full article

A rapid microwave-assisted process minimizing waste was set up to produce bio-based benzoxazine-like monomers produced from vanillylamine and melamine. Without excessive purification, different viscous liquid precursors had a remarkable ability to form four strong and transparent different solid cross-linked thermosets, displaying lower curing temperatures under 130 °C. The long and strong adhesive performance of the cured materials was observed using glass slides or aluminum surfaces and they could become a good alternative to adhesive epoxy resin for metal surfaces. At the higher temperatures, these solids could act as efficient flame-retardants proven by thermogravimetric measurements. The best candidates gave a limiting oxidation index value of 41.9. In order to improve the intrinsic surface hydrophobicity of the phenolic resins, slight amounts of silica and iron oxide nanoparticles were dispersed in the polymer matrix, and finally mechanical resistance was pointed out. The most promising of our melamine-based resin was loaded with aluminum pigment to furnish a silver-colored paste ready for being cured to afford a robust solid, which does not undergo contraction or deformation. Full article