Discrete Silver Research Articles

A Novel Approach to Produce Metal–Metal Composites by Leveraging Immiscibility: Laser Powder Bed Fusion of Nanosilver‐Dispersed Titanium

The antimicrobial properties of silver ions are well known and effectively utilized in various biomedical applications. The efficacy of silver‐containing materials, particularly in terms of antimicrobial activity, heavily relies on the oxidizing surface, favoring nanosized silver features. However, producing such structures is challenging due to the high probability of miscibility in the liquid phase. Developing Ti–Ag composite alloys using the laser powder bed fusion technique with supported titanium powders and silver nanoparticles (AgNPs) represents a novel research pursuit, with no prior investigations reported. Incorporating AgNPs into titanium forms nanoislands, directly enhancing the antimicrobial efficacy of biomedical components. In this study, it is aimed to explore the solubility limit of silver in titanium and the feasibility of achieving finely dispersed silver islands. Experimental findings reveal that incorporating AgNPs into Ti‐based alloys results in discrete silver islands (0.01–0.02 μm2) within the microstructure, governed by the solubility limit of silver in titanium. In this study, valuable insights into producing components with augmented biocompatibility and proven antibacterial properties against Staphylococci infections are offered. The successful development of Ti–Ag composite alloys, featuring finely dispersed silver islands, opens promising avenues for biomedical applications, enhancing their antibacterial characteristics and improving patient outcomes.

Sulfide Mineralization of Carbonate–Silicate Veins in Early Proterozoic Metabasites of North Karelia: Mineral Assemblages, Mineral Forms of Silver, and Fluid Inclusions

The work presents the first data on sulfide mineralization in carbonate–silicate veins, which are widespread on the islands and coast of the White Sea (North Karelia), associating with Early Proterozoic metamorphosed gabbroid bodies. The veins with Fe–Cu sulfide mineralization up to ore occurrences are localized within metabasite bodies and along their contacts with host gneisses. During the study of the mineral composition of the veins, the main assemblages of sulfide minerals were identified: chalcopyrite –bornite ± chlorite ± selenides and Pb–Ag tellurides (B1); digenite–bornite ± selenides and Pb, Ag, and Pd tellurides (B2); pyrite–bornite ± chalcopyrite (B3); marcasite–pyrite–bornite–chalcopyrite (B4); and siegenite–chalcopyrite ± acanthite ± chlorargyrite. The development of sulfide associations, as well as quartz–chlorite aggregates, was related to the late stage of vein formation. Inductively coupled plasma and laser ablation mass spectrometry analyses showed that bornite from association B1 has the highest silver content (up to 675 ppm) and, in terms of Ag, Se, and Bi contents, is closest to bornite from low-temperature epithermal, skarn, and high-temperature vein deposits. In general, bornite is the main Ag carrier in the studied associations, while digenite containing up to 1000 ppm Ag, as well as discrete silver minerals (selenides, tellurides, acanthite, and chlorargyrite), occur in subordinate quantities. Fluid inclusions in quartz from sulfide associations, as well as from a sulfide-free carbonate–silicate vein, were studied by cryo- and thermometric methods. It is established that mineralization at the late stages of vein formation was related to heterogeneous CO2–H2O–NaCl metamorphic fluid. Carbon dioxide fluid inclusions were captured by vein quartz at temperature of 253–314°C and pressure of 2 ± 1 kbar. Water–salt inclusions were captured in a wider temperature range of 100–500°С. The highest temperature fluid inclusions with temperatures of homogenization 300°С are characteristic of quartz veinlets of the siegenite–chalcopyrite association with Ag sulfide and chlorargyrite.

In Vitro Study on Effect of Zinc Oxide Nanoparticles on the Biological Activities of Croton tiglium L. Seeds Extracts.

Croton tiglium L. seeds were studied against colon cancer induced chemically in rats after incorporating silver nanoparticles (Ag-NPs) but the body has no the ability to discrete silver or silver ions. Therefore, the present study was designed to reveal the biological activities of different C. tiglium L. seeds extracts incorporated with zinc oxide nanoparticles (ZnO-NPs). It was found that C. tiglium L. seeds provided with high contents of total protein (27.43 g/100g), carbohydrate (18.29 g/100 g) and lipid (46.31 g/100 g). The chromatographic techniques revealed that concentrations of the predominant compounds increased in all studied extracts (ethanolic, aqueous and petroleum ether) after incorporating ZnO-NPs. The in vitro biological activities showed that the aqueous extract possessed the highest antioxidant and scavenging activities. It exhibited the highest inhibitory effect on α-amylase (41.89%) and acetyl cholinesterase (AChE) (23.00%) in addition to its higher anti-arthritic activity. All the biological activities increased after incorporating ZnO-NPs. It showed the highest cytotoxic activity that increased after incorporating ZnO-NPs against human colon carcinoma (CACO-2) cells. Therefore, this extract was selected for undergoing further studies on CACO-2 cells. The aqueous extract incorporated with ZnO-NPs arrested growth of CACO-2 cells at G2/M and increased percentage of total apoptotic cells and necrosis. The median lethal dose (LD50) showed that the extracts incorporated with ZnO-NPs were safer than the native extracts. The study showed that the aqueous extract was the most active extract that consequently exhibited promising biological activities after incorporating ZnO-NPs.

Ultralow loss visible light metamaterials assembled by metaclusters.

Optical metamaterials give birth to the control and regulation of light. However, because of strong energy dissipation and fabrication difficulty in meta-atoms, low-loss isotropic three dimensional negative index metamaterials (NIMs) in the visible spectrum has long been regarded as an extremely challenging. Here, we report an ultralow loss isotropic metamaterials for visible light and its inverse Doppler effect. The ball-thorn-shaped metaclusters with symmetrical structure consisting of the dielectric and its surface dispersed super-thin silver layer was proposed, the surface plasma resonance is formed by discrete silver layer with a thickness of two or three atomic layers. We invented a unique technique for preparing ultralow loss isotropic clusters and three-dimensional large block samples. The negative refractive index and the inverse Doppler effect of green and red light is measured by the prism method for the first time. The discrete super-thin silver layer produced by the photoreduction method greatly reduces the generation of loss and break through noble metal high energy losses of traditional optical frequency metamaterial, the metaclusters unfold bottleneck of the nano-assemble visible light metamaterials, opening a door for disorder assembling ultralow loss isotropic three-dimensional large block NIMs devices of arbitrary shape.

Four Discrete Silver Iodobismuthates/Bromobismuthates with Metal Complexes: Syntheses, Structures, Photocurrent Responses, and Theoretical Studies.

Using in situ formed metal complexes of [Fe(bipy)3]2+ or [Ni(bipy)3]2+ (bipy = 2,2'-bipyridine) as templates, four new Ag-Bi-X (X = I and Br) compounds are first isolated in the metal-complex-decorated heterometallic halobismuthate family, namely [M(bipy)3]AgBiI6 (M = Fe (1), Ni (2)), [Fe(bipy)3]AgBiBr6 (3), and [Ni(bipy)3]AgBiBr6 (4). Compounds 1-4 feature discrete [AgBiX6]n2n- anions, exhibiting three polymorphisms that may be ascribed to the different stackings and the flexible condensations of [BiX6] octahedrons and [AgX4] tetrahedra/[AgX3] triangles. UV-vis diffuse reflectance analyses reveal that they are narrow band gap semiconductor materials (ca. 1.82-2.13 eV). Intriguingly, the title compounds display excellent photoelectrical switching properties, with photocurrent density following the order 3 > 4 > 2 > 1. In addition, the comparative studies of intermolecular interactions, theoretical band structures, density of states, and effective masses of three polymorphisms have also been investigated.

Influence of chemical vapor precursor flow rate on the structure and thermal stability of phase-modulated VSiCN/Ag coatings

Ceramic/silver coatings are of interest for tribological and antimicrobial applications. Here, the amorphous phase volume fraction in VSiCN/Ag coatings was varied and the microstructure, mechanical properties, and vacuum annealing behavior of the phase-modulated VSiCN/Ag coatings were compared with columnar VN/Ag coatings. The coatings were deposited by filament-assisted reactive magnetron sputtering in a gas mixture of argon, nitrogen, and hexamethyldisilazane (HMDS). HMDS vapor flow rates were varied to influence coating amorphous phase content (0 at. % ≤ Si ≤ 10 at. %, 0 at. % ≤ C ≤ 20 at. %), and the sputter power supplied to a V58Ag42 target was manipulated to control metal content (3 at. % ≤ Ag ≤ 8 at. %). Silver surface segregation did not occur during coating growth, nor immediately after deposition. VN/Ag coatings exhibited columnar growth structures with >100 nm B1-VNx grains and 10−50 nm silver inclusions, which preferentially decorated the column boundaries. Columnar growth was completely disrupted in the VSiCN/Ag coatings and discrete silver inclusions were not observed within the microstructure. The hardness of all coatings was similar (12.3–16.5 GPa), while the apparent Young's modulus decreased from 247 to 169 GPa with increasing amorphous phase content. Rockwell indentation tests revealed that coating adhesion began to suffer after deposition at higher HMDS flow rates. Silver surface segregation was observed on all coatings after vacuum annealing at 550 °C for 1 h. The size of the surface particles ranged between 50 and 200 nm for the VN/Ag coating but was below 20 nm for the VSiCN/Ag coatings. Silver segregation occurred preferentially at coating growth defects in the columnar VN/Ag coating while the particle distribution was uniform across the surface of the VSiCN/Ag coatings. The results of this study demonstrate that phase modulation of ceramic/silver coatings may enable high-diffusivity microstructural features to be tailored for improved thermal stability and control of silver surface segregation at elevated temperatures.

Boosting chiral amplification in plasmon-coupled circular dichroism using discrete silver nanorods as amplifiers.

Remarkable chiral amplification in plasmon-coupled circular dichroism spectroscopy (CD) is demonstrated by using discrete Ag nanorods as amplifiers. An unprecedented CD enhancement factor of over 3000 times is achieved without resonant or near-resonant exciton-plasmon couplings.

In Vivo Evaluation of Bioabsorbable Fe-35Mn-1Ag: First Reports on In Vivo Hydrogen Gas Evolution in Fe-Based Implants.

This work investigates the influence of Ag (1 wt%) on the mechanical properties, in vitro and in vivo corrosion, and biocompatibility of Fe-35Mn. The microstructure of Fe-35Mn-1Ag possesses a uniform dispersion of discrete silver particles. Slight improvements in compressive properties are attributed to enhanced density and low porosity volume. Fe-35Mn-1Ag exhibits good in vitro and in vivo corrosion rate of Fe-35Mn due to an increase in microgalvanic corrosion. Gas pockets, which originate from an inflammatory response to the implants, are observed in the rats after 4 weeks implantation but are undetectable after 12 weeks. No chronic toxicity is observed with the Fe-35Mn-1Ag, suggesting acceptable in vivo biocompatibility. The high corrosion rate of the alloy triggers an increased level of nonadverse tissue inflammatory responses 4 weeks after implantation, which subsequently subsides at 12 weeks. The Fe-35Mn-1Ag displays properties that are suitable for orthopedic applications.

Highly Conductive and Highly Dispersed Polythiophene Nanoparticles for Fabricating High-Performance Conductive Adhesives

The continuous advancement of modern electronic equipment requires increasing the conductivity of electrically conductive adhesives (ECAs), but the gap between discrete silver flakes in conventiona...

Facile synthesis of silver alkynide cluster and coordination polymers using picolinic acid as a co-ligand.

We describe five 1D-coordination polymers and two discrete silver clusters consisting of alkynides and picolinic carboxylates as co-ligands. In some cases, DMSO or EtOH further solvated the structural motifs. Utilising the sterically demanding tri-isopropylsilyl acetylene afforded a tridecanuclear cluster that possessed an unprecedented core with a silver center surrounded by six octahedrally arranged silver atoms.

Discrete silver nanoparticle infusion across silica aerogels towards versatile catalytic coatings for 4-nitrophenol reduction

Abstract Hybrid metallic materials generated from the distributions of discrete nanoparticles offer a superior surface to volume ratio as well as enhanced optical, photonic, and electronic properties compared to bulk metallic materials. Such behaviours are correlated to the nano-scale metal inter-grain domains favouring the presence of electronic vacancies. In this work, an infusion strategy was used to incorporate silver nano-particles across a silica aerogel matrix. Furthermore, the enhancement in catalytic potential was correlated to the macro-properties of the hybrid catalytic monoliths, including their specific surface area and relative pore volume. Interestingly the performance of the samples was found to be optimum for very low loadings of silver nanoparticle dispersion capacity on the order of 0.006 vol%, while very high loadings likely generated extremely strong aggregations leading to more surface silver being available. The incorporation of the minute amounts of discrete nanoparticle distributions within the silica matrix increased the catalytic ability of the materials to degrade 4-nitrophenol by up to 20 times compared to bulk silver nanoparticles. This strategy opens new avenues for the design of complex architectures of either single or multi-metal materials encapsulated within silica for environmental remediation applications.

TMV Disk Scaffolds for Making sub-30 nm Silver Nanorings.

Nanosized bioscaffolds can be utilized to tackle the challenge of size reduction of metallic rings owing to their miniature features as well as their well-known biomineralization capacity. The tobacco mosaic virus coat protein is used as a command surface to grow and assemble silver nanoparticles into sub-30 nm rings. The versatility of TMV allows the formation of both solid silver rings and rings consisting of discrete silver nanoparticles. The pH-dependent coulombic surface map along with the annular geometry of the protein aggregate allow the generation of rings with or without a central nanoparticle. Our silver rings are believed to be the smallest to date, and they can offer a test material for existing theories on metallic nanorings of this heretofore unreached size scale.

Carbon-driven synthesis of bi-plasmonic Ag-Cu nanocomposite phosphate glasses

A simple method for the synthesis of Ag-Cu co-doped phosphate glasses displaying dual plasmon resonances is reported. The effective preparation is carried out by melting and heat treatment processes (ambient atmosphere) employing Ag2O and CuO as metal nanoparticle precursors alongside carbon powder as reductant. Melt-quenched material shows optical absorption features characteristic of discrete silver and copper nanoclusters, while the photoluminescence is dominated by monovalent copper. Further thermal processing results in the development of a broad, extended bi-metallic plasmonic absorption. It is primarily influenced by silver nanoparticles, and appears consistent with the precipitation of the metals individually. The facile approach paves the way for further research on glasses with enhanced plasmonic properties.

Discrete Silver(I)-Palladium(II)-Oxo Nanoclusters, {Ag4 Pd13 } and {Ag5 Pd15 }, and the Role of Metal-Metal Bonding Induced by Cation Confinement.

We introduce the class of discrete silver(I)-palladium(II)-oxo nanoclusters with the preparation of {Ag4 Pd13 } and {Ag5 Pd15 }. Both polyanions represent the first examples of noble metal-capped polyoxo-noble-metalates in a fully inorganic assembly, featuring an unprecedented host-guest mode containing hetero- and homometallic Ag-Pd and Ag-Ag bonding interactions. Comprehensive theoretical calculations suggest that the Ag-Pd metallic bonds originate partially from surface confinement of AgI guest ions onto the anionic polyoxopalladate host that is induced by strong electrostatic forces. This work opens the field of fully inorganic silver-palladium-oxo nanoclusters, which can be considered as discrete mixed noble metal precursors for the formation of monodisperse core-shell nanoparticles, with high relevance for catalysis.

Biofabrication of Discrete Silver and Gold Nanoparticles by the Bacterium Azospirillum brasilense: Mechanistic Aspects

We report that the bacterium Azospirillum brasilense can synthesize silver and gold nanoparticles. Discrete spherical nanoparticles of silver and colloidal gold of diverse shapes were found to accumulate in the culture liquid of A. brasilense strain Sp245. We show for the first time that bacterial extracellular Mn-peroxidase is involved in the reduction of silver from silver nitrate and in the reduction of gold from chloroauric acid to a nanoparticle form. The enzymatically fabricated particles were characterized by UV spectroscopy, atomic force and transmission electron microscopy, X-ray fluorescence, and dynamic light scattering. A mechanism is proposed for the Mn-peroxidase-aided biogenesis of metal nanoparticles.

Discrete nanosized metallic coatings produced by EB-PVD

This paper presents new technology variants of electron beam vapour phase deposition (EB-PVD) regarding discrete nanosized metal coatings on the surface of powders and granules of organic and inorganic substances. Examples of Ag, Cu and Fe produced coatings on the surfaces of microsized powders of inorganic (NaCl, Al2O3) and organic (polyvinylpyrrolidone, metronidazole, streptomycin, triazolin) substances, and millimetre organic granules (polyethylene, rice and wheat grains) are presented. Main attention is given to discrete silver coatings. Possibilities of transformation of powder systems with discrete coatings into liquid phase systems, for instance, colloids, following a simple technological schematic are shown, that is, deposition of metal nanoparticles on soluble powders of surfactants and subsequent dissolution of composites in water or other solvents. Directions of further research and development are proposed.

Coating nonfunctionalized silica spheres with a high density of discrete silver nanoparticles

Reducing AgNO $$_3$$ by glucose at basic pH coated the surface of silica spheres were coated with a high density of hemispherical silver nanoparticles by direct reduction. The average diameter of the nanoparticles was 3.2 $$\pm $$ 1 nm. A much lower silver concentration than is a standard favored heterogeneous nucleation of silver on the silica surface at the expense of homogeneous nucleation in solution. The slow growth rate of the nuclei promoted the formation of discrete silver particles rather than a continuous shell. Based on scanning electron microscopy and transmission electron microscopy, the surface coverage of silver seed particles was as high as 25 % at 10 °C without prior functionalization of the silica. The particles were composed of metallic silver based on X-ray photoelectron spectroscopy. There was a sharp increase in the silver surface coverage and a decrease in the particle size when the temperature was raised from 5 to 10 °C and the amount of silica was decreased from 0.2 to 0.025 V/V%. The size was controlled by the diffusion barrier through the ion shell surrounding the silica spheres and by maintaining reaction conditions where the particles on the surface compete for silver.

Grating-Vector-Assisted Plasmonic Coupling in a Hexagonally Arranged Silver Island Array

We experimentally and numerically investigated the attenuated total reflection (ATR) spectra of hexagonally periodic structures of discrete silver nano islands array (NIA) and that of continuous silver film with nanohole array (NHA). Some peculiar reflection fine dips in the ATR spectra of the NIA structures were observed. In comparison with the ATR results between NHA and NIA structures as well as carefully analyzing the multiwavelengths numerical ATR spectra of the NIA, we found out the mechanisms leading to the ATR fine dips. They are resulted from the effects of surface plasmon resonances (SPR) and Wood’s anomalies that occur at the silver/air or silver/prism interface with the assistance of two-dimensional reciprocal grating-vectors provided by the NIA. Particularly, our results demonstrated that there are continuous-film-like SPR modes existing in the NIA structures, which can be excited through the coupling between the incident light and the two-dimensional grating-vectors of the NIA.

Mechanism of Migration of Sintered Nanosilver at High Temperatures in Dry Air for Electronic Packaging

Low-temperature joining of semiconductor chips by sintering of silver paste is emerging as an alternative lead-free solution for die-attaching power electronic device, particularly for high-temperature applications. However, migration of sintered nanosilver should be fully understood for reliability evaluation. In this paper, we reported our findings and possible mechanism on high-temperature migration of sintered nanosilver on alumina substrate. Oxygen plays an important role in the migration of sintered nanosilver at high temperatures. The migrating silver bridges were presented as discrete silver particles on the surface of alumina substrate. The discrete silver particles preferentially emerged at the boundaries of the alumina particles at the initial stage. The mechanism would be useful to alleviate the migration of sintered nanosilver at high temperatures.

Ligands containing pyridyl-carboxylate terminals and their discrete silver and polymeric cadmium compounds: (n-py)–CH[dbnd]N–C10H6–COOH (n = 2 (HL1), 3 (HL2)), [Ag(HL1)2](PF6), [Ag(HL1)2](NO3)(H2O), and [Cd(L2)2

Two potential linking ligands containing pyridyl-carboxylate terminals {(n-py)–CH=N–C10H6–COOH (n=2 (HL1), 3 (HL2)} were synthesized by Schiff-base condensation under solvothermal conditions in methanol. Molecules of ligand HL1 are connected by the intermolecular O–H⋯N hydrogen bonds to create a 1D zigzag network. Ligand HL1 reacted with AgPF6 and AgNO3 to produce discrete Ag(I) complexes [Ag(HL1)2](PF6) (1) and [Ag(HL1)2](NO3)(H2O) (2), respectively. Compounds 1 and 2 form a dimeric structure formed by the intermolecular O–H⋯O hydrogen bonds between two carboxylate terminals of two adjacent molecules. A 3D cadmium coordination polymer, [Cd(L2)2]∞ (3), was prepared from ligand HL2 and Cd(CH3COO)2·2H2O under solvothermal conditions. Ligand HL1 exhibited a red-shift on complex formation in its photoluminescence emission spectrum.