Ag System Research Articles

Silver-induced activation of 8-hydroxyquinolinato lithium as electron injection material in single-stack and tandem OLED devices

Abstract The 8-hydroxyquinolinato lithium (Liq)|Ag system has been evaluated as the electron-injection layer for the MoOx| N,N′-di (1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) charge-generation layer in tandem organic light-emitting diode (OLED) devices. From current-voltage studies of single-stack devices, it is determined that Liq is a relatively poor electron-transport material. However, Liq is found to be useful as an electron-injection layer with activation by Ag. Efficient tandem devices have been obtained using Liq|Ag as the electron-injection layer adjacent to the MoOx|NPB charge-generation layer, where the optimal Ag thickness is about 20–40 A and the activation of Liq can be seen with as little as 1 A of Ag.

(Keynote) Surface Capping and the Shape Evolution of Colloidal Metal Nanocrystals

Surface capping plays a critical role in determining the final shape taken by colloidal metals nanocrystals. However, the mechanism is not always clear as it is still a challenging task to even determine the coverage density of capping agents on the final nanocrystals. In this talk, I will use a few examples from our own research to illustrate the critical importance of a quantitative measure of surface capping in understanding the shape evolution of colloidal metal nanocrystals, as well as in predicting the shape evolution process. The examples include bromide ions for the Pd system and poly(vinyl pyrrolidone) for the Ag system. In addition to experimental measurements, computational simulation also offers insightful guidance for the identification of effective capping agents for shape-controlled synthesis.

How Do Different Liquid Metal Films Coalesce on Carbon Substrates?

Droplet coalescence plays an indispensable role in diverse natural and industrial processes. However, it is still unclear that how the wettability and microstructure of the substrates influence the coalescence. Molecular dynamics simulations were used to investigate the coalescence behaviors of liquid metal films on carbon substrates. Two different coalescence regimes climbing-coalescence and coating-coalescence were, respectively, observed in Cu–Al and Cu–Ag systems on graphene. The balance of metal–substrate and metal–metal interactions was regarded as the key factor to determine the coalescence regimes. Additionally, the effects of surface roughness and atomic arrangement of substrates on the movements of droplets were also analyzed on other carbon materials. Our findings offer a thorough understanding of the relationship between coalescence and wettability and could have important implications in self-assembly, three-dimensional printing, and microfluidic devices.

Catalytic stereoselective total synthesis of a spiro-oxindole alkaloid and the pentacyclic core of tryptoquivalines.

An expedient route to the pentacyclic core of the tryptoquivaline alkaloids and the total synthesis of natural product (+)-3'-(4-oxoquinazolin-3-yl)spiro[1H-indole-3,5'-oxolane]-2,2'-dione (1) have been achieved. The route is enabled by a key, highly stereoselective, aldol reaction catalysed by a Ag(i) and cinchona-derived aminophosphine ligand system, forming a highly substituted oxazoline ring, and setting the C1 spirocyclic stereocentre for downstream manipulation.

Intrinsic stress response of low and high mobility solute additions to Cu thin films

Thin film stress is frequently controlled through adjustments applied to the processing parameters used during film deposition. In this work, we explore how the use of solutes with different intrinsic growth properties influences the residual growth stress development for a common solvent Cu film. The findings demonstrated that the addition of a high atomic mobility solute, Ag, or a low atomic mobility solute, V, results in both alloy films undergoing grain refinement that scaled with increases in the solute content. This grain refinement was associated with solute segregation and was more pronounced in the Cu(Ag) system. The grain size reduction was also associated with an increase in the tensile stresses observed in both alloy sets. These findings indicate that solutes can be used to control the grain size under the same deposition conditions, as well as alter the stress evolution of a growing thin film.

Truncated and spheroidal Ag nanoparticles: a matter of size transformation

The ordered arrays of anisotropic mesostructure metal nanoparticle (diameter size in the range of 15 to 200 nm) characteristics are indeed influenced by the combined effect of packing constraints and inter-particle interactions, that is, the two morphological factors that strongly influence the creation of the particles’ shape. In this work, we studied on how the degree of truncation of Ag nanoparticles authorised the mesostructured morphologies and particle orientation preferences within the mesosparticle arrays. The Ag represented the best and most versatile candidate and known for its highest electrical conductivities among other transition metals in periodic table. The interest is motivated by the need to understand the inevitable morphological transformation from mesoscopic to microscopic states evolve within the scope of progressive aggregation of atomic constituents of Ag system. The grazing information obtained from HR-TEM shows that Ag mesosparticles of highly truncated flake are assembled in fcc-type mesostructure, similar to the arrays formed by microscopic quasi-spherical structure, but with significantly reduced packing density and different growth orientations. The detailed information on the size and microstructure transformation have been gathered by fast Fourier transform (FFT) of HR-TEM images, allowing us to figure out the role of Ag defects that anchored the variation in crystallite growth of different mean diameter size particles. The influences on the details of the nanostructures have to be deeply understood to promote practical applications for such outstanding Ag material.

Crack Resistance of an Alloy of the Al – Cu – Mg – Ag System

Cyclic crack resistance of an aluminum alloy of the Al – Cu – Mg – Ag system with a high content of doping elements is studied. It is shown that the alloy possesses a high threshold value of the stress intensity factor for nucleation of fatigue cracks. However, the nonuniform distribution of second-phase particles in the material reduces the crack resistance. Special features and main differences of the relief of fatigue fracture surfaces of the alloy in various regions of the kinetic diagram are considered. Coefficients of the Paris’ equation for the region of linear fatigue-crack growth are determined.

THE ROLE OF COMPETITION EFFECT IN THE SELF-ASSEMBLY STRUCTURE OF 3,5-DIPHENYLBENZOIC ACID AND 2,2′:6′,2″-TERPYRIDINE-4′-CARBOXYLIC ACID ON Ag(110)

The self-assembly structures of 2,2[Formula: see text]:6[Formula: see text],2[Formula: see text]-terpyridine-4[Formula: see text]-carboxylic acid (C[Formula: see text]H[Formula: see text]N3O2; [Formula: see text]) molecules and 3,5-diphenylbenzoic acid (C[Formula: see text]H[Formula: see text]O2; [Formula: see text]) molecules on Ag(110) surface have been investigated by scanning tunneling microscopy (STM) and Density Functional Theory (DFT) calculation. The [Formula: see text] molecules form two different well-organized structures due to the [Formula: see text]–[Formula: see text] stacking and dipole–dipole interactions. When three C atoms of [Formula: see text] molecules are replaced by three N atoms to form [Formula: see text] molecules, the main driving force to form ordered assembly structures of [Formula: see text] molecule is changed to metal–organic coordination bond and hydrogen bond. The dramatic changes of main driving force between [Formula: see text]/Ag(110) and [Formula: see text]/Ag(110) system demonstrate that the N atoms are apt to form metal–organic coordination bond and hydrogen bond but dipole–dipole interactions and [Formula: see text]–[Formula: see text] stacking are relative to C atoms. These findings further reveal that the optimization design of organic molecules could vary the main driving force and then lead to the change of the molecular self-assembly structures.

Square Wave Voltammetry Measurements of Low Concentrations of Nitrate Using Au/AgNPs Electrode in Chloride Solutions

AbstractThe aim of this work is to highlight the potential of using a modified gold electrode with controlled quantity of silver nanoparticles as a working electrode to detect low concentrations of nitrate in chloride solutions. Optimal charge for silver deposition has been determined to obtain the highest signal for the nitrate reduction as the electrocatalytic properties of the bimetallic electrode were directly influenced by its composition. According to the Volcano plot obtained the charge chosen was −52 μC for a 3 mm diameter electrode, corresponding to 4.6×1015 Ag atoms cm−2. It has been shown that dioxygen did not participate to the nitrate reduction mechanism. In order to decrease the limit of quantification, square wave voltammetry was preferred to less sensitive cyclic voltammetry. Nitrate was quantified in chloride solutions in the concentration range found in the open ocean, i. e. 0.39–50 μmol L−1 with a good linear regression (R2=0.9969). The stability of the bimetallic Au−Ag systems has been evaluated and showed almost no difference on the signal recorded over a 26 days period which is suitable to consider an in situ sensor development for marine applications.

Simultaneous Determination of Transport Properties of Some Multi-Component Glasses of Se–Te–Sn–Ag (STSA) System

Simultaneous Determination of Transport Properties of Some Multi-Component Glasses of Se–Te–Sn–Ag (STSA) System

First-Principles Study on Solution Strengthening Effect of Cu and Zn in Ag Alloy

A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the mechanical properties and electronic properties of AgCu and AgZn solid solution. The VCA models have been set up for solid solution, and elastic constants, bulk modulus and shear modulus, Young modulus and density of states of Cu or Zn doped Ag system were also analysed. The results show that Cu and Zn in Ag alloy play a role of solution strengthening, the solid solution strengthening effect was obviously improved by adding a small amount of Cu(less than 2at.%) or Zn(less than 1at.%). The total DOS of AgCu(Zn) Solid solution is mainly constituted by the Ag 4d and Cu(Zn) 4d states. The AgZn Solid solution has a more stable structure than AgCu solid solution.

Detection Study Based on the Surface Plasmon Resonance Effect of the MoS2–Ag System

Detection Study Based on the Surface Plasmon Resonance Effect of the MoS₂–Ag System

Tuning electronic and magnetic properties in monolayer MoSe2 by metal adsorption

We have systematically explored the electronic structures and magnetic properties of metal Pd, Pt, Cu, Ag, Au and Zn adsorbed MoSe2 monolayer by means of first-principles calculations. It reveals that stable chemical adsorption has been formed between the adatoms Pd, Pt, Cu, Ag, Au and MoSe2 monolayer, however, weak physical interaction is found between Zn and MoSe2 monolayer owing to the small adsorption energy. Both the framework structure and electronic property of the metal adsorbed MoSe2 monolayer are slightly tuned by the adatoms. More importantly, magnetic character is introduced in Cu, Ag and Au systems.

Prediction of Ternary Liquidus Temperatures by Statistical Modeling of Binary and Ternary Ag-Al-Sn-Zn Systems.

The relationship of liquidus temperatures among six binary and four ternary phases in a Ag–Al–Sn–Zn system was analyzed by means of statistical modeling. Four statistical models to predict changes in the liquidus temperatures in Ag–Al–Sn–Zn were proposed on the basis of different hypotheses derived from macroscopic and microscopic standpoints. The results of interpolation tests to evaluate the prediction accuracies of the ternary liquidus temperatures suggested that the multivariate regression model based on binary liquidus temperatures, interactive binary liquidus temperatures, and products of atomic ratios was found to be the most effective among the four models. It was numerically shown that the prediction accuracies of the liquidus temperatures in local ternary systems of Ag–Al–Sn–Zn can be improved further by using the models identified in their neighboring systems. Finally, the possibility to extract the general trend and the abnormal combination of elements for the prediction of liquidus temperatures was discussed on the basis of the statistical framework we considered.

Two-step fabrication of nanoporous copper films with tunable morphology for SERS application

It is important to design and fabricate nanoporous metals (NPMs) with optimized microstructures for specific applications. In this contribution, nanoporous coppers (NPCs) with controllable thicknesses and pore sizes were fabricated via the combination of a co-sputtering of Cu/Ti with a subsequent dealloying process. The effect of dealloying time on porous morphology and the corresponding surface enhanced Raman scattering (SERS) behaviors were systematically investigated. Transmission electron microscopy (TEM) identified the presences of the gaps formed between ligaments and also the nanobumps on the nanoparticle-aggregated ligament surface, which were likely to contribute as the “hot spots” for electromagnetic enhancement. The optimal NPC film exhibited excellent SERS performance towards Rhodamine 6G (R6G) with a low limiting detection (10−9M), along with good uniformity and reproducibility. The calculated enhancement factor of ca. 4.71×107 was over Au substrates and comparable to Ag systems, promising the proposed NPC as a cheap candidate for high-performance SERS substrate.

Exploring the mechanism and kinetics of Fe–Cu–Ag trimetallic particles for p-nitrophenol reduction

Preparation conditions of Fe–Cu–Ag trimetallic particles were optimized by single-factor and response surface methodology (RSM) batch experiments to obtain high-reactive Fe0-based materials for p-nitrophenol (PNP) removal. Under the optimal conditions (i.e., Fe0 dosage of 34.86 g L−1, theoretical Cu mass loading of 81.87 mg Cu/g Fe, theoretical Ag mass loading of 1.15 mg Ag/g Fe, and preparation temperature of 52.1 °C), the actual rate constant (kobs) of PNP reduction in 5 min was 1.64 min−1, which shows a good agreement between the model prediction (1.85 min−1) of RSM and the experimental data. Furthermore, the high reactivity of Fe0-based trimetals was mainly attributed to the plating order of transition metals (i.e., Ag and Cu). Furthermore, we propose a new theory that the pyramid trimetallic structure of Fe–Cu–Ag could improve the electron transport and create active sites with high electron density at the surface (Ag layer) that could enhance the generation of surface-bonded atomic hydrogen ([H]abs) or the direct reduction of pollutant. Moreover, Fe–Cu–Ag trimetallic particles were characterized by SEM, EDS, and XPS, which also could confirm the proposed theory. In addition, the leached Cu2+(<10 μg L−1) and Ag+ (below detection limits) in Fe–Cu–Ag system could be neglected completely, which suggests that Fe–Cu–Ag is reliable, safe, and environment friendly. Therefore, Fe–Cu–Ag trimetallic system would be promising for the removal of pollutants from industrial wastewater.

High cyclic fatigue performance of Al–Cu–Mg–Ag alloy under T6 and T840 conditions

High cyclic fatigue (HCF) behavior of an AA2139 alloy belonging to Al–Cu–Mg–Ag system in T6 and T840 conditions was examined. The T840 treatment involving cold rolling with a 40% reduction prior to peak ageing provides an increase in tensile strength compared with the T6 condition. However, fatigue lifetime for two material conditions was nearly the same since there is weak effect of thermomechanical processing on micro-mechanisms of crack initiation and growth.

Enhanced stability and fluorescence of mixed-proteins-protected gold/silver clusters used for mercury ions detection

We have synthesized gold/silver nanoclusters (NCs) under the protection of both bovine-serum-albumin (BSA) and lysozyme (Lyz) and found that the NCs protected by the mixed-proteins give rise to largely enhanced stability and fluorescence, enabling promising applications for chemosensing and bioimaging. The enhanced fluorescence of Au NCs was found to be exclusively quenched at the presence of Hg2+ ions with an ultralow detection limit up to ∼0.7nM. It is also interesting to find that the BSA-Lyz-Au NCs are nontoxic and available for fluorescence imaging of Hg2+ detection in MCF-7 cells. The low cytotoxicity, good penetrability and fluorescence sensitivity of BSA-Lyz-Au NCs suggest promising biological applications. Similar observations were also addressed for the Ag system, indicating general applicability of this facile strategy based on BSA-Lyz mixed proteins for the protection of metal NCs.

One‐pot carboxylative cyclization of propargylic alcohols and CO2 catalysed by N‐heterocyclic carbene/Ag systems

A series of N‐heterocyclic carbene (NHC)/Ag systems were developed for the carboxylative assembly of propargylic alcohols and carbon dioxide (CO2). With the catalysis of these catalytic systems, a variety of target α‐alkylidene cyclic carbonates could be obtained smoothly under atmospheric CO2 pressure in straightforward one‐pot processes. Particularly, these reactions could be performed without any stoichiometric addition of bases or additives. Further mechanistic investigation reveals that the excellent activities are attributed to the effective activations of CO2 accomplished by the NHCs via the formation of the NHC‐CO2 adducts.

The development of new phosphors of Tb3+/Eu3+ co-doped Gd3Al5O12 with tunable emission

The gadolinium aluminum garnets Gd3Al5O12 (GdAG) activated with Tb3+/Eu3+ were successfully prepared via co-precipitation method at 1500 °C in this work. The crystal structure stabilization, elements analysis, microphotograph, PL/PLE spectra, decay behavior and quantum efficiency were discussed in detail. The metastable GdAG compounds been effectively stabilized by doping with smaller 10 at.% Tb3+, which then allows the development of new phosphors of (Gd0.9-xTb0.1Eux)3Al5O12 (GdAG:Tb3+/Eu3+, x = 0–0.03) for opto-functionality explorations. The PLE/PL spectra displays that the strongest PLE peak was located at ∼276 nm, which overlaps the 8S7/2 → 6IJ transition of Gd3+. Under 276 nm excitation, the phosphors exhibited both Tb3+ and Eu3+ emissions at 548 nm (green, 5D4 → 7F5 transition of Tb3+) and 592 nm (orange-red, 5D0 → 7F1 transition of Eu3+), respectively. The emission intensities of Tb3+ and Eu3+ remarkably varied with the Eu3+ incorporation. As a consequence, the emission color can be readily tuned from approximately green to orange-red. Fluorescence decay analysis found that the lifetime for the Tb3+ emission rapidly decreased conforming to the Tb3+ → Eu3+ energy transfer, and the energy transfer efficiency was calculated. Owing to the Gd3+ → Eu3+ and Gd3+ → Tb3+ energy transfer, the emission intensities of Tb3+ and Eu3+ in (Gd0.9-xTb0.1Eux)AG phosphor were higher than (Y0.87Tb0.1Eu0.03)AG and (Lu0.87Tb0.1Eu0.03)AG system. The (Gd0.9-xTb0.1Eux)AG garnet phosphors developed in this work may serve as a new type of phosphor which hopefully meets the requirements of various lighting and optical display applications.