Ag Interactions Research Articles

Silver(I)-pyridinyl Schiff base complexes: Synthesis, structural characterization and reactivity in ring-opening polymerisation of ε-caprolactone

Reactions of AgO2C2F3 with 2-pyridinyl Schiff base ligands bore five novel complexes of the type [(AgO2C2F3)2.L2]: where L=L1, (E)-N-(1-(pyridin-2-yl)ethylidene)aniline, 1; L=L2 (E)-2,6-diisopropyl-N-(1-(pyridin-2-yl)ethylidene)aniline, 2; L=L3 (E)-N-(pyridin-2-ylmethylene)aniline, 3; L=L4 (E)-2,6-diisopropyl-N-(pyridin-2-ylmethylene)aniline, 4; and [AgO2C2F3.L2] 5, L=(E)-2,6-dimethyl-N-(pyridin-2-ylmethylene)aniline L5. Structural studies revealed that complexes 1 to 4 are dinuclear with each Ag(I) atom chelated by a ligand in a bidentate manner via pyridinyl and imine N atoms. Anion coordination in complexes 1 and 3 is monodentate through an O atom leaving Ag…Ag interactions to complete the coordination spheres. In complexes 2 and 4, two anions bridge two silver(I) centres in a μ2-κ2O:O′ fashion. Complex 5 is a mononuclear salt where the trifluoroacetate anion is entirely kicked out of the Ag(I) coordination sphere. The geometry around the Ag(I) centres in 1 to 4 can best be described as distorted trigonal pyramidal and in complex 5, pseudo-tetrahedral. Complexes 1–5 were studied for ring-opening polymerization of ε-caprolactone where 1 and 3 had higher catalytic activity than 2, 4 and 5. The ε-polycaprolactone polymers obtained were of average molecular weight with good polydispersity indexes.

Detrended analysis of shower track distribution in nucleus-nucleus interactions at CERN SPS energy

We have studied the charged particle density fluctuations in 16O+Ag(Br) and 32S+Ag(Br) interactions at 200A GeV incident energy in the laboratory frame by using the detrended methods. These methods can extract (multi)fractal properties of the underlying distributions after filtering out the average trend of fluctuations associated. Multifractal parameters obtained from data analysis are systematically compared with event samples generated by the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, where Bose–Einstein correlation (BEC) effect is mimicked via a charge reassignment algorithm implemented as an after burner. Both the experimental and the simulated data are subjected to two different statistical techniques namely the multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended moving average (MFDMA) analysis. The results indicate that for both the interactions considered the pseudorapidity distributions of the shower tracks are multifractal in nature. Qualitatively, both methods of analysis and both interactions considered, result in similar behavior of multifractal parameters. We do however notice significant quantitative differences in certain cases.

Synthesis and characterization of new Ag(I) coordination networks based on saccharinate and bis(isopropylimidazole) ligands exhibiting very close C–H⋯Ag interactions

Two Ag(I) coordination networks, formulated as [Ag(sac)(μ-bisopib)]n (1) and [Ag(sac)(μ-pbisopix)]·H2O (2), have been synthesized based on the bis(isopropylimidazole) ligands 1,4-bis(2-isopropyl-1H-imidazol-1-yl)butane (bisopib) and 1,4-bis((2-isopropyl-1H-imidazol-1-yl)methyl)benzene (pbisopix), respectively, along with saccharinate (sac) ligands. All the complexes were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction studies. The X-ray crystallographic studies of 1 and 2 revealed that the Ag(I) ions are μ-bridged by the bis(isopropylimidazole) derivative ligands to generate 1D zig-zag polymer and dinuclear structures, respectively. As far as we know, complex 1 shows the closest C–H⋯Ag interaction distance among similar literature examples. In complex 1 adjacent 1D coordination polymers are further joined by C–H⋯O hydrogen bonds and π⋯π interactions, generating a 3D supramolecular network. The C–H⋯O hydrogen bonds and C–H⋯π interactions play a crucial role in the architecture of the 3D network of complex 2. Thermal decompositions and photoluminescent properties of the Ag(I) complexes are also discussed herein.

Effect of Ag and Cu additions on natural aging and precipitation hardening behavior in Al-Mg-Si alloys

The effects of Ag and/or Cu additions on the natural aging and precipitation hardening behavior of Al-Mg-Si alloys were investigated by using hardness test, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Both Ag and Cu additions enhanced the hardening kinetics of Al-Mg-Si alloys during natural aging (NA) and artificial aging (AA) treatments. The strong interaction of Cu, Ag and Mg atoms is responsible for the improved precipitation kinetics of these alloys, resulting in a refinement of clusters and precipitates. The stronger interaction between Ag and Mg results in lower T4 hardness and higher AA hardness, compared to Cu. This is potentially beneficial for automobile applications where rapid hardening during paint baking is required. Both Ag and Cu additions reduce the detrimental effect of NA on subsequent AA, due to the formation of Ag or Cu-containing clusters. The clear advantage of Ag addition, compared to Cu, is the improvement of precipitation hardening response of Al-Mg-Si alloys.

Colorimetric sensing of silver ion based on anti aggregation of gold nanoparticles

A colorimetric assay with excellent selectivity is reported for detecting silver ion in aqueous solutions. The system works based on the competitive interaction of gold nanoparticles (AuNPs) and Ag+ with tris(hydroxymethyl) aminomethane (tris). The sensing strategy is quite simple, fast, convenient and the detection is by the naked eye. The aggregation of AuNPs with tris was inhibited in the presence of Ag+ ions resulting in a significant hypsochromic spectral shift of the surface plasmon resonance (SPR) of AuNPs and a color change from blue to red. The interaction between tris and Ag+ ion was investigated with cyclic voltammetry. The effect of Ag+ concentration on the aggregation of AuNPs by tris was monitored by UV–vis spectroscopy with the dynamic range of 1–9μM and detection limit of 0.41μM. The recovery analysis of river water and wastewater samples proved that this colorimetric sensor is successfully operational in environmental monitoring.

Bandgap- and Local Field-Dependent Photoactivity of Ag/Black Phosphorus Nanohybrids

Black phosphorus (BP) is the most exciting post-graphene layered nanomaterial that serendipitously bridges the 2D materials gap between semimetallic graphene and large bandgap transition-metal dichalcogenides in terms of high charge-carrier mobility and tunable direct bandgap, yet research into BP-based solar to chemical energy conversion is still in its infancy. Herein, a novel hybrid photocatalyst with Ag nanoparticles supported on BP nanosheets is prepared using a chemical reduction approach. Spin-polarized density functional theory (DFT) calculations show that Ag nanoparticles are stabilized on BP by covalent bonds at the Ag/BP interface and Ag−Ag interactions. In the visible-light photocatalysis of rhodamine B by Ag/BP plasmonic nanohybrids, a significant rise in photoactivity compared with pristine BP nanosheets is observed either by decreasing BP layer thickness or increasing Ag particle size, with the greatest enhancement being up to ∼20-fold. By virtue of finite-difference time domain (FDTD) simu...

Unraveling the Complex Behavior of AgNPs Driving NP-Cell Interactions and Toxicity to Algal Cells.

While the importance of nanoparticle (NP) characterization under relevant test conditions is widely recognized in nanotoxicology, few studies monitor NPs behavior in the presence of exposed organisms. Here we studied the behavior of nine types of silver nanoparticles (AgNPs) during the 48 h algal toxicity test. In particular, we investigated NP aggregation and dissolution by time-resolved inductively coupled plasma mass spectrometry and ultrafiltration and performed mass balance measurements to study the distribution of Ag in the test system. We also determined the amount of extra- and intracellular Ag by chemically etching AgNPs on the surface of algal cells and used dark field microscopy for their imaging. We observed that positively charged branched polyethilenimine (bPEI)-coated AgNPs tend to aggregate in the presence of algae and interact with test vessels and algal cells, while citrate-coated AgNPs have a tendency to dissolve. On the other hand, with large variation of half-maximum effective concentration (EC50) across tested NPs (5.4 to 300 ngAg mL-1), Ag internalized by the algal cells at EC50 was similar (0.8 to 3.6 ngAg mL-1) for all AgNP types. These data show that while sorption to the vessels, dissolution, and aggregation impact on the distribution of AgNPs in the test system and on interactions with algal cells, AgNP toxicity is strongly correlated with the NP-cell surface interaction and internalization of Ag.

Promoting Ag/Al2O3 Performance in Low-Temperature H2-C3H6-SCR by Thermal Pretreatment of γ-Alumina in Water

The present work highlights for the first time that a thermal treatment of γ-Al2O3 in water at 80 °C for 24 h prior to Ag deposition (Ag/Al2O3-OH) leads to a drastic enhancement of H2-C3H6-SCR performance at low temperature. This enhancement is attributed to the higher NO x coverage on Ag/Al2O3-OH compared with that of Ag/Al2O3. The higher NO x adsorption capacity of the sample prepared from the γ-Al2O3 thermally-treated in water is proposed to result from the preferential interaction of Ag with newly-created Al2O3 anchoring sites (Al(OH)3 bayerite domains), which were not available on the untreated pristine support. Graphical Abstract

Facile synthesis of ternary Ag/C/SnO2 hollow spheres with enhanced activity for hydrazine electro-oxidation

Highly dispersed ternary Ag/C/SnO2 hollow spheres have been synthesized for hydrazine electro-oxidation. The sharp XRD peak of Ag shows that Ag nanoparticles of Ag/C/SnO2 have good crystallinity. SEM shows that Ag/C/SnO2 maintained a good spherical morphology with the diameter of about 300nm. TEM shows that Ag nanoparticles with the average diameter of about 10nm disperse well on C/SnO2. The advantages derived from C/SnO2 support including carbon, SnO2 and hollow structures may facilitate the dispersion of Ag and the close interaction of Ag with support. The results of hydrazine electro-oxidation show that C/SnO2 has no activity for hydrazine electro-oxidation while ternary Ag/C/SnO2 exhibits excellent electrocatalytic activity with the negative oxidation peak at −0.25V (vs. SCE) and the high peak current of 473μA at the scan rate of 20mVs−1. The enhancement of activity may be attributed to the small size, homogeneous dispersion of Ag and the synergistic effect derived from Ag/C/SnO2 hollow spheres.

Subtle difference of [SiMo12O40]4− and [PMo12O40]3− inducing two new distinct Keggin-Ag-(1H-Pyrazole) compounds

Two new inorganic-organic hybrid compounds based on α-Keggin clusters and Ag-(1H-Pyrazole) subunits, [AgL2]4[SiMo12O40] (1) and [AgL2]3[PMo12O40] (2) (L = pyrazole), have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction. In 1, there are two kinds of chains, the chains linked by two [AgL2]+ clusters and the other linked only by one [AgL2]+, which further connect by sharing [SiMo12O40]4− anions to construct a 2-D layer. In 2, four-supporting [PMo12O40]3− anions are fused by [Ag(1)L2]+ subunits to form a 1-D chain. Through weak interactions of Ag⋯O (3.091 Å) a 2-D supramolecular layer is constructed. Additionally, the electrochemical properties of title compounds and the photocatalytic properties of 2 have been studied.

Synthesis and structural elucidation of 1-D silver(I) aliphatic carboxylate coordination polymers with 1,3,5-triaza-7-phosphaadamantane/N-methyl-1,3,5-triaza-7-phosphaadamantane

Reactions of silver(I) salts of acetate and trifluoroacetate with 1,3,5-triaza-7-phosphaadamantane (PTA) afforded 1-D coordination polymers [Ag(μ2-PTA-κ2P -:N)(μ2-O2CCH3-κ2O:O′)]n·2nH2O (1) and [Ag(μ2-PTA-κ2P:N)(μ2-O2CCF3-κO)]n·nH2O (2), while a reaction of silver(I)trifluoroacetate with N-methyl-1,3,5-triaza-7-phosphaadamantane (PTAMe) afforded the coordination polymer [Ag(PTAMe)(μ3-O2CCF3-κ3O:O:O’)(μ2-O2CCF3-κ2O:O′)]n (3). The coordination polymers were characterized using single-crystal X-ray diffraction. Nuclear magnetic resonance, infrared, and electron spray ionization mass spectrometries were used to initially establish complexation of Ag(I) to the PTA or PTAMe before recrystallization. In the crystal structures of 1 and 2, coordination of the PTA moieties to Ag(I) is via P and N forming chains that are linked through bridging carboxylates. The resulting structural motif can be described as ladder-like in which –[PTA–Ag–PTA]– chains are the strands while the bridging carboxylates comprising of –[Ag–O–C–O]2– or –[Ag–O]2– metallacycle rungs of the ladder. Compound 3 forms single-stranded coil-like coordination polymers with two non-equivalent Ag(I) centers, both tetrahedrally coordinated by four oxygens from four trifluoroacetates in one and by three oxygens from the trifluoroacetates and in each by the P of the PTAMe with alternating Ag⋯Ag interactions. The crystal structures of all three coordination polymers have a variety of fairly strong hydrogen bonds and intermolecular interactions which contribute stabilization of the crystal lattices.

Syntheses and crystal structures of two new silver–organic frameworks based on N-pyrazinesulfonyl-glycine: weak Ag···O/N interaction affecting the coordination geometry

Abstract Two new metal–organic frameworks, namely, [Ag2(L)] n (1) and {[Ag2.5(L)(bpy)2]·(NO3)0.5·(H2O)4.5} n (2), where H2L=N-pyrazinesulfonyl-glycine and bpy=4,4′-bipyridine, have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. X-ray diffraction crystallographic analyses indicate that 1 displays a silver carboxylate-sulfonamide layer structure containing an uncommon heptanuclear [Ag7] cluster wherein four silver(I) atoms form an Ag4 plane with in a three-connected (6, 3) net. The molecular structure of 2 has three crystallographically independent two-coordinate Ag centers with an intersecting Ag-bpy chain structure in a six-connected (3, 6) or a four-connected (4, 4) topology. The L2− ligand serves as a μ 7-(η 2-O,N), (η 2-O′,N′), O,O″,O″′,N,N″ ligand in 1 and as a μ 3-(η 2-O,N), N,O′ ligand in 2. In the crystal, a 3D supramolecular architecture is formed by coordinative bonding in 1, but through O–H···O bonding as well as π···π stacking in 2. The two compounds show a combination of coordinative bonds, ligand-supported Ag···Ag interactions and weak Ag···O/N coordinative interactions in the solid state.

Temperature- and pressure-dependent utilising dimensionality cross-over of Silver(I) complex supported by short Ag···Ag Interactions

Two Ag(I)-based complexes, a mononuclear [Ag(PPh3)2(2tpCOO)]·EtOH (1) and a tetranuclear [Ag4(PPh3)4(2tpCOO)4] (2) have been prepared by a small tuning on the molar ratio of the reactants as well as the crystallisation method. A 1-D polymeric structure, [Ag2(PPh3)(2tpCOO)2]n (3) was obtained while the crystals of 2 were left under high temperature and autogenous pressure. The study suggests that the formation of 1-D polymeric structure is due to the removal along with the intramolecular and intermolecular reorganisation of the coordinated ligands that leads to dimensionality cross-over from 0-D to 1-D. The rearrangement of the ligands in 3 also resulted the metal centres moving closer together, being separated by 2.9626(3) Å in 3, compared to 3.215(8) Å in 2. The photoluminescence properties have been investigated showing that only complexes 2 and 3 exhibit this property at room temperature in solid state that is due to metal-to-ligand charge transfer.

Detection of Silver Ions Using Dielectrophoretic Tweezers-Based Force Spectroscopy.

Understanding of the interactions of silver ions (Ag+) with polynucleotides is important not only to detect Ag+ over a wide range of concentrations in a simple, robust, and high-throughput manner but also to investigate the intermolecular interactions of hydrogen and coordinate interactions that are generated due to the interplay of Ag+, hydrogen ions (H+), and polynucleotides since it is critical to prevent adverse environmental effects that may cause DNA damage and develop strategies to treat this damage. Here, we demonstrate a novel approach to simultaneously detect Ag+ satisfying the above requirements and examine the combined intermolecular interactions of Ag+-polycytosine and H+-polycytosine DNA complexes using dielectrophoretic tweezers-based force spectroscopy. For this investigation, we detected Ag+ over a range of concentrations (1 nM to 100 μM) by quantifying the rupture force of the combined interactions and examined the interplay between the three factors (Ag+, H+, and polycytosine) using the same assay for the detection of Ag+. Our study provides a new avenue not only for the detection of heavy metal ions but also for the investigation of heavy metal ions-polynucleotide DNA complexes using the same assay.

Coordination Polymers of M2L2 Macrocycles and M3L2 Podands Containing Tris (pyridyl) Tripodal Amide: Anion Bridging, Ag⋅⋅⋅Ag Interactions and Solid‐State Luminescence

AbstractThe tris‐pyridyl‐tripodal amide ligand (L), which is synthesized by the condensation of tris(2‐aminoethyl)amine (tren) and isonicotinic acid, was shown to form coordination polymers (CPs) with AgX (X= CF3SO3−, BF4− and ClO4−), HgX2 (X= Cl− and Br−) and CdI2. The crystal structure analysis of {[Ag3L2(CF3SO3)3].MeOH}n, 1, {[AgL](BF4).2H2O}n, 2, {[AgL](ClO4).MeOH.H2O}n, 3, {[Hg2Cl4L].H2O}n, 4, [Hg3Br6L2], 5, [Cd2I4L2.(H2O)2], 6, reveals that they are constituted by M2L2 macrocycles and M3L2 podand structures. The complexes 1–4 were found to form 1D‐coordination polymers by linking M2L2 units via anions. Complexes 5 and 6 found to contain capsule (podand) like structure with M3L2 and M2L2 H2O compositions in 5 and 6 respectively. The complex 1 contains Ag⋅⋅⋅Ag interactions within the Ag2L2 macrocycle whereas the complex 2 and 3 contains such argentophilic interactions between the macrocycles. These 1D‐CPs linked further via amide‐to‐amide and amide‐to‐water hydrogen bonding to form higher dimensional networks. In these complexes the ligand (L) found to exhibit conformational variations which defines the overall network geometries. The ligand (L) and the coordination complexes 1–6 were found to exhibit intense luminescence emissions upon exciting at a wavelength of 310 nm.

A luminescent novel octanuclear silver(I) cluster framework with potential Cr2O72 − sensing

An unique and novel octanuclear silver(I) cluster compound, [Ag8(ADC)4]n (1) (H2ADC=1,3-adamantanedicarboxylic acid), has been synthesized and characterized. Compound 1 exhibits significant Ag–Ag interactions to form 2D infinite silver layers with multiple unsaturated Ag atoms. Moreover, Luminescent investigations show that 1 can exhibit highly selective response to Cr2O72− through luminescence quenching effect in aqueous solution, which make its good candidate as luminescent sensor.

Effect of MnO2 morphology on the catalytic oxidation of toluene over Ag/MnO2 catalysts

The Ag/MnO2 catalysts with different morphologies (wire-like, rod-like and tube-like) are used as toluene oxidation catalysts in an attempt to investigate how the structures of support affect the interaction of Ag and MnO2, and thus the toluene catalytic activity. Analysis by TEM, H2-TPR and XPS measurements reveals that the structures of MnO2 influence the particle size and dispersion of silver particles and the combination of silver particles with MnO2. Meanwhile, the addition of Ag regulates the performance of MnO2. The small particle size and hemispherically shaped Ag particles are easily to form and homogeneously dispersed on the surface of wire-like MnO2. And this specific form of Ag shows the strongest interaction with MnO2, which promotes the low-temperature reducibility of support and generated more lattice oxygen in metal oxides. The Ag/MnO2 nanowires sample exhibits the highest reactivity for toluene oxidation with a complete conversion at 220°C. Therefore, the excellent catalytic performance of Ag/MnO2 nanowires catalyst for toluene oxidation is clearly connected with the interaction between the Ag and MnO2, which is determined by the morphology of MnO2 support.

A Multinary Silver Cluster, Multicoordinated Silver Supramolecular Framework With a 2D Anionic Water Aggregation

A new 3D supramolecular framework, [Ag6(2-PyBIM)6(ClO4)6(CH3OH)2(H2O)11] (1) (2-PyBIM = bis[(2-pyridinyl)-imidazol-1-yl]methane), has been prepared and structurally characterized. Compound 1 exhibits a 2D cationic network as a wave-like brick wall with a multi-coordinated Ag mode (di-, tri-, and tetranitrogen coordinated Ag centers) and multinary Ag cluster centers (Ag, Ag2, and Ag3) with the ligand-unsupported Ag—Ag interaction, encapsulated in an unprecedented 2D perchlorate-methanol-water layer of [(ClO4)6(CH3OH)4(H2O)11]6– anions. Additionally, the thermal stabilities and photoluminescence spectra of the complex 1 are also discussed.

Silver nanoparticles in silicate glass prepared by UV laser irradiation: dependences of size and atomic structure of particles upon irradiation parameters

Plasmonic Ag nanostructures were generated in glass surfaces by means of UV laser irradiation (193 nm). The aim of the work was to identify the correlations between the atomic structure of such nanoparticles and their optical properties. The structural characterization of the samples, prepared with different number of laser pulses was performed by Ag K-edge EXAFS. The processing of the spectra by the Fourier-transform analysis gave the values of Ag-Ag and Ag-O interactions averaged over ionic and neutral states of silver in the sample. The consistent analysis of the behavior of features in optical spectra and the obtained dependencies of Ag-Ag and Ag-O structural parameters upon the number of laser pulses enabled to suggest the mechanism of plasmonic Ag nanoparticles formation in silicate glass, which is influenced by the interaction with polyvalent ions (for example Fe2+) and by defect centers (for example HTC and NBOHC centers) generated by UV irradiation.

Formation of silver nanoparticles in silicate glass using excimer laser radiation: Structural characterization by HRTEM, XRD, EXAFS and optical absorption spectra

Plasmonic silver nanostructures in surfaces of soda-lime silicate glasses were generated using Ag+ ↔ Na+ ion exchange and UV laser irradiation (ArF laser, 193 nm) with different number of ns laser pulses (from 2 to 5000). To identify the correlations between the optical properties (surface plasmon resonance (SPR) parameters) and atomic structure of silver nanoparticles and their agglomerations, characterization of the samples was performed by HRTEM, XRD, optical absorption in visible range and Ag K-edge EXAFS spectra. Analysis of the optical spectra was performed using a Mie theory approach, accounting for the most plausible defect centers in silicate glass like hole trap centers and non-bridging oxygen hole centers. Processing of Ag K-edge EXAFS yielded values of Ag-Ag and Ag-O interactions averaged over ionic and neutral states of silver. The consistent treatment of HRTEM and XRD data, the behavior of features in optical spectra and the obtained dependence of Ag-Ag and Ag-O structural parameters upon the number of laser pulses enabled to suggest a mechanism of plasmonic Ag nanoparticles formation in silicate glass under UV laser irradiation.