Search Results (84)

A novel single-walled carbon nanotube (SWNT), silver (Ag) nanoparticle, and zinc benzene carboxylate (ZnBDC) metal–organic framework (MOF) composite was synthesised and systematically characterised to develop an efficient platform for mercury ion (Hg²⁺) detection. X-ray diffraction confirmed the successful incorporation of Ag nanoparticles and SWNTs without disrupting the crystalline structure of ZnBDC. Meanwhile, field-emission scanning electron microscopy and energy-dispersive spectroscopy mapping revealed a uniform elemental distribution. Thermogravimetric analysis indicated enhanced thermal stability. Electrochemical measurements (cyclic voltammetry and electrochemical impedance spectroscopy) demonstrated improved charge transfer properties. Electrochemical sensing investigations using differential pulse voltammetry revealed that the SWNTs/Ag@ZnBDC-modified glassy carbon electrode exhibited high selectivity toward Hg²⁺ ions over other metal ions (Cd²⁺, Co²⁺, Cr³⁺, Fe³⁺, and Zn²⁺), with optimal performance at pH 4. The sensor displayed a linear response in the concentration range of 0.1–1.0 nM (R² = 0.9908), with a calculated limit of detection of 0.102 nM, slightly close to the lowest tested point, confirming its high sensitivity for ultra-trace Hg²⁺ detection. The outstanding sensitivity, selectivity, and reproducibility underscore the potential of SWNTs/Ag@ZnBDC as a promising electrochemical platform for detecting trace levels of Hg2+ in environmental monitoring. Full article

Neurodegenerative diseases (NDDs), including Alzheimer’s disease (AD) and Parkinson’s disease (PD), are characterized by progressive neuronal dysfunction and loss and represent a significant global health challenge. Oxidative stress, neuroinflammation, and neurotransmitter dysregulation, particularly affecting acetylcholine (ACh) and monoamines, are key hallmarks of these conditions. The current therapeutic strategies targeting cholinergic and monoaminergic systems have some limitations, highlighting the need for novel approaches. Metallodrugs, especially ruthenium and platinum complexes, are gaining attention for their therapeutic use. Among metal complexes, gold(I) and silver(I) N-heterocyclic carbene (NHC) complexes exhibit several biological activities, but their application in NDDs, particularly as monoamine oxidase (MAO) inhibitors, remains largely unexplored. To advance the understanding of this field, we designed, synthesized, and evaluated the biological activity of a new series of Au(I) and Ag(I) complexes stabilized by NHC ligands and bearing a carboxylate salt of tert-butyloxycarbonyl (Boc)-N-protected proline as an anionic ligand. Through in silico and in vitro studies, we assessed their potential as acetylcholinesterase (AChE) and MAO inhibitors, as well as their antioxidant and anti-inflammatory properties, aiming to contribute to the development of potential novel therapeutic agents for NDD management. Full article

Aiming toward a novel, noninvasive technique, with a real-time potential application in the monitoring of the complexation of steroidal neuromuscular blocker drugs Vecuronium (Vec) and Rocuronium (Roc) with sugammadex (SDX, medication for the reversal of neuromuscular blockade induced by Vec or Roc in general anesthesia), we developed proof-of-principle methodology based on surface-enhanced Raman spectroscopy (SERS). Silver nanoparticles prepared by the reduction of silver ions with hydroxylamine hydrochloride were used as SERS-active substrates, additionally aggregated with calcium nitrate as needed. The Vec and Roc SERS spectra were obtained within the biorelevant 5 × 10⁻⁷–1 × 10⁻⁴ M range, as well as the SERS of SDX, though the latter was observed only in the presence of the aggregating agent. SDX/drug complexes at a 1/1 molar ratio revealed significant spectral changes in the vibrational bands of the SDX glucose rings and the drug steroid rings, implying that the insertion of Vec and Roc molecules into the SDX cavity was not only driven by attractive electrostatic interactions between the positively charged cyclic unit of the drug and the negative carboxylate groups of cyclodextrin but also supported by hydrophobic interactions between the host cyclodextrin and the guest drug molecule. The observed changes in SERS signals are applicable in biorelevant conditions and support further studies of SDX/drug complexes in vivo. Full article

The work focuses on five epithermal Au-Ag deposits of the Kamchatka volcanogenic belts: Rodnikovoe, Baranyevskoe, Kumroch, Lazurnoe (adularia-sericite type–Ad-Ser) and Maletoyvayam (acid-sulfate type–Ac-Sul). The geochemical characteristics of the deposits were presented based on the results of ICP-OES and fire-assay analysis. The compositions and physicochemical parameters of ore-forming fluids were based on microthermometry, Raman spectroscopy and gas chromatography-mass spectrometry. It was shown that all deposits were comparable in terms of temperatures, salinity and the predominance of H₂O and CO₂ in ore-forming fluids. The deposits were formed at temperatures of 160–308 °C by aqueous fluids with salinities of 0.5–6.8 wt. % (NaCl-eq.). The Maletoyvayam deposit differed from the other ones in significant enrichment in Se, Te, Sb, Bi and As, as well as much higher concentrations of hydrocarbons, nitrogenated and sulfonated compounds (31.4 rel.% in total) in the composition of fluid inclusions. This gave us a reason to assume that organic compounds favourably affected the concentrations of these elements in the mineralising fluid. Kumroch and Lazurnoe were distinguished from Rodnikovoe and Baranyevskoe by high Zn, Pb and Cu contents, where each of them represented a single system combining both Ad-Ser type epithermal gold-silver and copper porphyry mineralisations. The presence of alkanes, esters, ketones, carboxylic acids and aldehydes in different quantities at all deposits were indicators of the combination of biogenic and thermogenic origins of organic compounds. The contents of ore-forming elements in ores were consistent with the specificity of mineral assemblages in the Kamchatka deposits. Full article

A number of N-heterocyclic carbene–silver compounds (NHCs)AgX were tested in the direct carboxylation of terminal alkynes using carbon dioxide as the C1 carbon feedstock. The reactions proceed at a pressure of 1 atm of CO₂ at room temperature, in the presence of Cs₂CO₃, and using silver–NHC complexes as catalysts. Thus, phenylacetylene and several alkynes are converted to the corresponding propiolic acids in good to high conversions. The activity of the catalysts is strongly influenced by the substituents on the NHC backbone and the nature of the counterion. Specifically, the most active compound exhibits iodide as the counterion and is stabilized by a benzimidazole derivative. After 24 h of reaction, a quantitative conversion is obtained utilizing DMF as the solvent and phenylacetylene as the substrate. Full article

Glutamate is the most important excitatory neurotransmitter, which is relevant for the study of several diseases such as amyotrophic lateral sclerosis and Alzheimer. It is the form L-glutamic acid (Glu) takes at physiologically relevant pHs. The surface-enhanced Raman spectra of Glu obtained at pH values ranging from 3.3 to 12 are collected in the presence of silver and gold colloids and on solid substrates. The observed bands are compared with the positions of calculated normal modes for free neutral glutamic acid, glutamic acid monohydrate, glutamic acid bound to gold and silver atoms, and sodium glutamate. Although gold atoms prefer to bind to the NH₂ group as compared to carbonyl groups, silver atoms prefer binding to hydroxyl groups more than binding to the amino group. SERS spectra of glutamic acid solutions with a pH value of 12, in which both carboxylic groups are deprotonated, indicate a complexation of the glutamic acid dianion with the sodium cation, which was introduced into the solution to adjust the pH value. Further research towards an optimal substrate is needed. Full article

Two new Ag(I) complexes with coumaric carboxylic acid derivatives have been synthesized. Structural studies of these noncrystalline complexes have been performed using a methodology that combines laboratory and synchrotron techniques, supported by density functional theory calculations. The arrangement of ligands around the Ag(I) cation has been refined using infrared, extended X-ray absorption fine structure, and X-ray absorption near edge structure spectroscopies. Different coordination modes of carboxylate ligands are observed for the studied compounds. Carboxylate bridges are characteristic for the Ag(I) complex with 4-oxo-4H-1-benzopyran-2-carboxylic acid (1), while a bidentate chelating motif was found for the complex with 2-oxo-2H-1-benzopyran-3-carboxylic acid (2). Additionally, the carbonyl oxygen atom of the coumarin ring coordinates to the silver cation in complex 2, while it is inactive in complex 1. Antimicrobial evaluation has been performed for both compounds. The complexes show activity against selected bacteria as well as Candida yeast. This activity is slightly lower for bacteria and the same or higher for Candida in relation to the reference substances: ciprofloxacin or fluconazole. Full article

Antimicrobial coatings are becoming increasingly popular in functional material modification and are essential in addressing microbial infection challenges. In this study, the phytochemical and antimicrobial potential of aqueous, 80% methanol and 80% ethanol pod extracts of Acacia concinna (Willd.) DC (AC) and its application in the green in situ (one pot) synthesis of silver nanoparticles on Cellulose nano fibrils (CNF) and Waterborne polyurethane (WPU) were prepared. The phytochemical evaluation of Acacia concinna crude extracts showed the presence of alkaloids, flavonoids, phenols, tannins, terpenoids, saponins, steroids. The surface plasmon Resonance peak of CNF/AC-AgNPs was 450 nm and the FTIR result confirmed functional groups such as carbonyl, phenols and carboxyl were present which was important for the bio-reduction of silver nanoparticles. The crude AC aqueous pods extract against Gram-positive and Gram-negative bacteria compared with AC ethanol and AC methanol extracts. The WPU/CNF/AC-AgNPs composite dispersion was also good in terms of its antibacterial activities. The WPU/CNF/AC-AgNPs nanocomposites could be applied as bifunctional nanofillers as an antimicrobial agent in food packaging systems and other biological applications. Full article

This work proposes for the first time protecting–reflecting on both sides of plated mirrors and a solution to polycarbonate surface vulnerability to weathering and scratching using tungsten disulfide (WS₂) by mechanical polishing. The ability of the dynamic chemical plating (DCP) technique to deposit Ag films at the nanometer scale on a polycarbonate (PC) substrate and its characteristics to be metallized is also shown. These deposits hold significant promise for concentrated solar power (CSP) applications. Complementarily, the application of WS₂ as a reflective film for CSP by mechanical polishing on smooth polycarbonate surfaces is both novel and practical. This technique is innovative and scalable without needing reactants or electrical potential, making it highly applicable in real-world scenarios, including, potentially, on-site maintenance. The effects of surface morphology and adhesion, and the reflectivity parameters of the silver metallic surfaces were investigated. Wettability was investigated because it is important for polymeric surfaces in the activation and metal deposition immediately after redox reactions. The flame technique improved wettability by modifying the surface with carbonyl and carboxyl functional groups, with PC among the few industrial polymers that resisted such a part of the process. The change in the chemical composition, roughness, and wettability of the surfaces effectively improved the adhesion between the Ag film and the PC substrate. However, it did not significantly affect the adhesion between PC and WS₂ and showed its possible implementation as a first surface mirror. Overall, this work provides a scalable, innovative method for improving the durability and reflectivity of polycarbonate-based mirrors, with significant implications for CSP applications. Full article

A family of silver(I) and copper(I) complexes containing carboxylate ligands were prepared from the corresponding carboxylic acids and Ag₂O. The compounds were characterized by various spectroscopic methods and X-ray diffraction. In the solid state, the silver(I) salts are coordination polymers based on dinuclear silver species with bridging carboxylate ligands. The reaction of these silver salts with Ph₃P gives four-coordinate, tetrahedral bis(phosphine) complexes. Analogous copper(I) bis(phosphine) compounds were prepared by the reduction of copper(II) carboxylates with Ph₃P. Decomposition temperatures and thermal decomposition products were studied by TGA/DSC measurements. The metal compounds decomposed cleanly to their respective metals (silver or copper) at temperatures ranging from 206 to 338 °C. Full article

With the development of microelectronics products with high density and high power, it is urgent to improve the electrical and thermal conductivity of electronic paste to achieve the new requirements of packaging materials. In this work, a new synthesis method of Ag-MWCNTs was designed: Firstly, carboxylated MWCNTs and stannous chloride were used as raw materials to prepare high-loading-rate Sn-MWCNT composite material to ensure the high loading rate of metal on the MWCNT surface. Then, Ag-MWCNT composite material was prepared by the chemical displacement method to solve the problem of the low loading rate of silver nanoparticles on the MWCNT surface. On the basis of this innovation, we analyzed and compared the electrical, thermal, and mechanical properties of Ag-MWCNT composite electronic paste. Compared with the electronic paste without adding Ag-MWCNTs, the resistivity was reduced by 77%, the thermal conductivity was increased by 66%, and the shear strength was increased by 15%. Therefore, the addition of Ag-MWCNTs effectively improves the electrical, thermal, and mechanical properties of the paste, making it a promising and competitive choice for new packaging materials in the future. Full article

Epoxy resins find extensive utility across diverse applications owing to their exceptional adhesion capabilities and robust mechanical and thermal characteristics. However, the demanding reaction conditions, including extended reaction times and elevated reaction temperature requirements, pose significant challenges when using epoxy resins, particularly in advanced applications seeking superior material properties. To surmount these limitations, the conventional approach involves incorporating organic catalysts. Within the ambit of this investigation, we explored the catalytic potential of metallic powders, specifically bismuth (Bi) and silver (Ag), in epoxy resins laden with various curing agents, such as diacids, anhydrides, and amines. Metallic powders exhibited efficacious catalytic activity in epoxy–diacid and epoxy–anhydride systems. In contrast, their influence on epoxy–amine systems was rendered negligible, attributed to the absence of requisite carboxylate functional groups. Additionally, the catalytic performance of Bi and Ag are different, with Bi displaying superior efficiency owing to the presence of inherent metal oxide layers on its powder surfaces. Remarkably, the thermal and mechanical properties of uncatalyzed, fully cured epoxy resins closely paralleled those of their catalyzed counterparts. These findings accentuate the potential of Bi and Ag metal catalysts, particularly in epoxy–diacid and epoxy–anhydride systems, spanning a spectrum of epoxy-based applications. In summary, this investigation elucidates the catalytic capabilities of Bi and Ag metal powders, underscoring their ability to enhance the curing rate of epoxy resin systems involving diacids and anhydrides but not amines. This research points toward a promising trajectory for multifarious epoxy-related applications. Full article

The investigation of interconnection technologies is crucial for advancing semiconductor packaging technology. This study delved into the various methods of achieving electrical interconnections, focusing on the sintering process and composition of the epoxy. Although silver (Ag) has traditionally been utilized in the sintering process, its high cost often precludes widespread commercial applications. Copper (Cu) is a promising alternative that offers advantages, such as cost-effectiveness and high thermal and electrical conductivities. However, the mechanical robustness of the oxide layers formed on Cu surfaces results in several challenges. This research addresses these challenges by integrating epoxy, which has advantages such as adhesive capabilities, chemical resistance, and robust mechanical properties. The chemical reactivity of the epoxy was harnessed to both fortify adhesion and inhibit oxide layer formation. However, the optimal sintering performance required considering both the composite composition (20 wt% epoxy) and the specific sintering conditions (pre-heating at 200 °C and sintering at 250 °C). The experimental findings reveal a balance in the incorporation of epoxy (20 wt%) for the desired electrical and mechanical properties. In particular, the bisphenol A epoxy (Da)-containing sintered Cu chip exhibited the highest lab shear strength (35.9 MPa), whereas the sintered Cu chip without epoxy represented the lowest lab shear strength of 2.7 MPa. Additionally, the introduction of epoxy effectively curtailed the onset of oxidation in the sintered Cu chips, further enhancing their durability. For instance, 30 days after sintering, the percentage of oxygen atoms in the Da-containing sintered Cu chip (4.5%) was significantly lower than that in the sintered Cu chip without epoxy (37.6%), emphasizing the role of epoxy in improving Cu oxidation resistance. Similarly, the samples sintered with bisphenol-based epoxy binders exhibited the highest electrical and thermal conductivities after 1 month. This study provides insights into interactions between epoxy, carboxylic acid, solvents, and Cu during sintering and offers a foundation for refining the sintering conditions. Full article

Rhazya stricta is a major medicinal species used in indigenous medicinal herbal medications in South Asia, the Middle East, Iran, and Iraq to treat a variety of ailments. The current study aimed to investigate the antifungal properties of biosynthesized silver nanoparticles (AgNPs) made from R. stricta aqueous extract and its alkaline aqueous fraction. Fourier transform infrared spectroscopy (FTIR), UV-vis spectrophotometry, dynamic light scattering (DLS), and transmitted electron microscopy (TEM) were used to characterize AgNPs. The produced extracts and AgNPs were tested for their antifungal efficacy against four Fusarium spp. All of the characterization experiments proved the biosynthesis of targeted AgNPs. FTIR showed a wide distribution of hydroxyl, amino, carboxyl, and alkyl functional groups among all preparations. The DLS results showed that the produced Aq-AgNPs and the Alk-AgNPs had an average size of 95.9 nm and 54.04 nm, respectively. On the other hand, TEM results showed that the Aq-AgNPs and Alk-AgNPs had average diameters ranging from 21 to 90 nm and 7.25 to 25.32 nm. Both AgNPs absorbed UV light on average at 405 nm and 415 nm, respectively. Regarding the fungicidal activity, the highest doses of Aq-extract and Aq-AgNPs inhibited the mycelial growth of F. incarnatum (19.8%, 87.5%), F. solani (28.1%, 72.3%), F. proliferatum (37.5%, 75%), and F. verticillioides (27.1%, 62.5%), respectively (p < 0.001). Interestingly, the Alk-fraction had stronger inhibition than the biosynthesized AgNPs, which resulted in complete inhibition at the doses of 10% and 20% (p < 0.001). Furthermore, microscopic analysis demonstrated that both AgNPs caused obvious morphological alterations in the treated organisms when compared to the control. In conclusion, R. stricta’s Aq-extract, alkaline fraction, and their biosynthesized AgNPs show substantial antifungal efficacy against several Fusarium spp. It is the first study to highlight the prospective biological activities of R. stricta Aq-extract and its alkaline fraction against F. incarnatum, F. proliferatum, and F. verticillioides. In addition, it is the first opportunity to deeply investigate the ultrastructural changes induced in the Fusarium species treated with R. stricta crude Aq-extract and its biosynthesized AgNPs. More studies are required to investigate their biological effect against other Fusarium or fungal species. Full article

The integration of hydroxyapatite (HA) with broad-spectrum bactericidal nano-silver within biopolymer-based bone scaffolds not only promotes new bone growth, but also effectively prevents bacterial infections. However, there are problems such as a poor interface compatibility and easy agglomeration. In this project, zeolitic imidazolate frameworks (ZIF-8) were grown in situ on nano-HA to construct a core–shell structure, and silver was loaded into the ZIF-8 shell through ion exchange. Finally, the core–shell structure (HA@Ag) was composited with polylactic acid (PLLA) to prepare bone scaffolds. In this case, the metal zinc ions of ZIF-8 could form ionic bonds with the phosphate groups of HA by replacing calcium ions, and the imidazole ligands of ZIF-8 could form hydrogen bonds with the carboxyl groups of the PLLA, thus enhancing the interface compatibility between the biopolymers and ceramics. Additionally, the frame structure of MOFs enabled controlling the release of silver ions to achieve a long-term antibacterial performance. The test results showed that the HA@Ag nanoparticles endowed the scaffold with good antibacterial and osteogenic activity. Significantly, the HA@Ag naoaprticle exhibited a good interfacial compatibility with the PLLA matrix and could be relatively evenly dispersed within the matrix. Moreover, the HA@ZIF-8 also effectively enhanced the mechanical strength and degradation rate of the PLLA scaffold. Full article