Increasing Silver Content Research Articles

Synthesis of monophasic Ag doped hydroxyapatite and evaluation of antibacterial activity

The present study aims to synthesized biomaterial that has antibacterial properties. Currently the surgical implants associated infections are a major cause of implant failure. Synthesis of silver doped hydroxyapatite as an antibacterial agent has potential importance to overcome post-surgical infections in a variety of clinical applications. Five silver doped hydroxyapatite Ca10−xAgx(PO4)6(OH)2 (x = 0, 0.1, 0.3, 0.5, 0.7 M) samples were synthesized by precipitation method and sintered at 900 °C to obtain well crystallized structure. No minor phase developed with silver addition, hexagonal hydroxyapatite (JCPDS# 09-432) was the single phase identified in all silver doped hydroxyapatite samples. The lattice parameter a and c changed with increase in silver concentration. The results of in vitro bioactivity revealed the bone bonding ability of silver doped hydroxyapatite samples. The antibacterial test showed that silver doped hydroxyapatite was sensitive to Staphylococcus aureus bacteria. Addition of silver significantly (P < 0.005) increased the antibacterial activity.

RADIATION SYNTHESIS OF SILVER NANOPARTICLES/CHITOSAN AGAINST Corynespora cassiicola CAUSING LEAF FALL DISEASE ON RUBBER TREES

In this study, silver nanoparticles (AgNPs) were prepared by gamma rays irradiation of 1.0, 2.5, 5.0 and 10 mM silver nitrate solution using chitosan as a stabilizer. UV spectra, morphology and size of AgNPs irradiated at different doses were characterized by using UV-vis spectrophotometer and TEM images. The obtained results indicated that the average size of AgNPs increased by the increase of silver concentration in irradiated solution or the degree of acetylation of chitosan, while the increase of chitosan concentration was found to be a functional key for reducing the average size of particles in AgNPs product. In vitro test, AgNPs inhibited the growth of Corynespora cassiicola. In particularly, the inhibitory efficiency of AgNPs on the growth of C. cassiicola on rubber leaf extract media increased from 52.1 to 100 % when the average particle size of particles in AgNPs product decreased from 15 to 5 nm at the concentration of 50 ppm. In addition, the increase of AgNPs concentration from 10 to 90 ppm also enhanced the antifungal activity to be from 6.3 to 100 %, respectively. It suggests that the silver nanoparticles/chitosan (AgNPs/chitosan) synthesized by γ-rays irradiation method is a very promising fungicidal product applying for treating C. cassiicola, a serious pathogen fungus on rubber trees.

Effect of silver doping on optical and electrochemical properties of ZnO photoanode

In this work, the effect of silver doping on structural, morphological, optical and photoelectrochemical properties have been deeply investigated. A set of photoanodes composed of silver-doped zinc oxide thin films (SZO) deposed onto fluorine doped tin oxide substrates ($${\text{Sn}}{{\text{O}}_2}$$:F) are synthesized using sol–gel technique. Scanning electron microscopy (SEM) analysis reveals that the Ag incorporation leads to an increase of ZnO grain size with uniform spherical size distribution. Surface morphology of silver-doped ZnO thin films (SZO) sounded by Atomic Force Microscopy (AFM) images have shown that surface roughness tends to increase with increasing silver concentration. All the films are highly transparent in the visible region. In addition, band gap energies were found to decrease after Ag doping. A decrease of the photoluminescence intensity is observed for 3% Ag doped photoanode which is attributed to the strong charge separation of the photo-carriers. The overall photoelectrochemical (PEC) performance of the photoanodes was investigated and largely discussed. Moreover, the silver-doped zinc oxide photoanodes are more photoactive than pure ZnO one and the photoanode made with 3% Ag doping yields the highest photocurrent. This behavior is in concordance with photoluminescence measurements. Charge transfer processes at the Ag doped ZnO/electrolyte interface were identified by electrochemical impedance spectroscopy. The donor density and the flat-band potential of ZnO: Ag films were analyzed from the Mott–Schottky plots. It was found that the ZnO photoanode doped with 3% Ag gives the best photoelectrochemical performances.

Influence of micro-alloying with silver on microstructure and mechanical properties of Al-Cu alloy

The present study aims to investigate the microstructure and mechanical properties of Al-Cu-Zn-Fe-Ti-Mg alloy (≈ 2219 Al-alloy), micro-alloyed with silver (Ag in the range 0 − 0.1 wt%), under different thermo-mechanical process conditions. Investigation of the microstructure of cast alloys revealed the presence of intermetallic CuAl2 and metastable Al-Cu-Fe-Zn-Si-Mn phases at the grain boundary regions. The as-cast dendritic structure was eliminated by heat treatment and subsequent rolling process resulting in improved mechanical properties. The strength and hardness increased with the increase in silver content up to 0.07 wt% in combination with reasonable ductility. Maximum strength for the alloy was achieved in the rolled and age hardened condition. Fractographic studies revealed brittle failure in as-cast alloys, whereas the heat treated alloys exhibited features typical of ductile failure.

Tunable near-infrared epsilon-near-zero and plasmonic properties of Ag-ITO co-sputtered composite films

Series of co-sputtered silver-indium tin oxide (Ag-ITO) films are systematically fabricated. By tuning the atomic ratio of silver, composite films are manifested to have different microstructures with limited silver amount (<3 at.%). Two stages for film morphology changing are proposed to describe different status and growth mechanisms. The introduction of silver improves the preferred orientations of In2O3 component significantly. Remarkably, dielectric permittivity of Ag-ITO films is highly adjustable, allowing the cross-over wavelengths λc to be changed by more than 300 nm through rapid post-annealing, and thus resulting in tunable epsilon-near-zero and plasmonic properties in the near-infrared region. Lower imaginary permittivity compared with pure metal films, as well as larger tunability in λc than pure ITO films suggest the potentiality of Ag-ITO films as substituted near-infrared plasmonic materials. Extended Maxwell-Garnett model is applied for effective medium approximation and the red-shifting of epsilon-near-zero region with the increase of silver content is well-fitted. Angle-variable prism coupling is carried out to reveal the surface plasmon polariton features of our films at optical communication wavelength. Broad dips in reflectance curves around 52–56° correspond to the SPP in Ag-ITO films.

The Effect of Silver Ion Occupancy on Hollandite Lattice Structure

ABSTRACTThe effect of tunnel cations on tunnel size in α-MnO2 structured (hollandite, cryptomelane) materials has long been of interest, as the tunnel size effects catalytic and transport properties. Previous research on the tunnel size has focused on potassium cryptomelane (KxMn8O16). This paper uses synthetic control of silver content in AgxMn8O16 to investigate the effect that tunnel silver occupancy has on the lattice parameters. Materials with silver (x) content between 1.14 and 1.66 were synthesized, synchrotron diffraction and Rietveld Refinement was used to determine lattice parameters. The lattice parameters were found to contract as silver content increases (from 9.774 Å to 9.738 Å), in contrast to previous investigations of other tunnel cations.

Antimicrobial activity of Ti-ZrN/Ag coatings for use in biomaterial applications

Severely broken bones often require external bone fixation pins to provide support but they can become infected. In order to reduce such infections, novel solutions are required. Titanium zirconium nitride (Ti-ZrN) and Ti-ZrN silver (Ti-ZrN/Ag) coatings were deposited onto stainless steel. Surface microtopography demonstrated that on the silver containing surfaces, Sa and Sv values demonstrated similar trends whilst the Ra, average height and RMS value and Sp values increased with increasing silver concentration. On the Ti-ZrN/Ag coatings, surface hydrophobicity followed the same trend as the Sa and Sv values. An increase in dead Staphylococcus aureus and Staphylococcus epidermidis cells was observed on the coatings with a higher silver concentration. Using CTC staining, a significant increase in S. aureus respiration on the silver containing surfaces was observed in comparison to the stainless steel control whilst against S. epidermidis, no significant difference in viable cells was observed across the surfaces. Cytotoxicity testing revealed that the TiZrN coatings, both with and without varying silver concentrations, did not possess a detrimental effect to a human monocyte cell line U937. This work demonstrated that such coatings have the potential to reduce the viability of bacteria that result in pin tract infections.

Ionic transport in AgI‐HgS‐As2S3 glasses: Critical percolation and modifier‐controlled domains

AbstractElectrical measurements, dc and ac, show that (AgI)x(HgS)0.5‐x/2(As2S3)0.5‐x/2 glasses, 0.0 ≤ x ≤ 0.6, exhibit drastic changes in ionic conductivity σi with silver iodide additions. The ionic transport increases by 13 orders of magnitude with increasing silver content from ~0.002 to ~23 at.%, and the activation energy decreases from 1.05 to 0.35 eV. Two distinctly different ion transport regimes above the percolation threshold concentration, xc ≈ 30 ppm, were distinguished. The critical percolation regime at low silver content (≤ 2‐5 at.% Ag) is characterized by a random distribution of silver‐related entities and obeys a power‐law composition dependence of σi. The ion transport parameters depend on the host network connectivity, represented by the average coordination number &lt;n0&gt;, via the critical fictive temperature T0; the calculated T0 value is comparable to the glass transition temperature for the glassy (HgS)0.5(As2S3)0.5 host matrix. In contrast, in the modifier‐controlled domain, the silver‐related entities are nonrandomly distributed. The high Ag+ ionic mobility results from interconnected tetrahedral (AgI2/2S2/2)n chains in the silver iodide content range 0.2 &lt; x ≤ 0.5, and from 2D layers (Ag3/3I3/3)n or 3D mixed tetrahedral subnetwork (AgI3/3S1/2) in the range x &gt; 0.5.

Электрические свойства интеркалированных соединений Ag-=SUB=-x-=/SUB=-MoSe-=SUB=-2-=/SUB=- в постоянном и переменном полях

AbstractOn intercalated Ag_ x MoSe_2 samples, in addition to temperature measurements of the direct current electrical resistivity, measurements of the alternating current resistivity using the impedance spectroscopy technique are carried out in a wide frequency range and at different temperatures. The activation behavior of the d.c. conductivity, which increases with increasing silver content in the samples, is shown. The a.c. conductivity undergoes frequency dispersion, described by a “universal dynamic response” (UDR). It is shown that the relaxation processes during charge transfer in a variable field are accelerated with increasing silver content in the samples and with increasing temperature. The data obtained are analyzed using the models of the band and hopping conduction.

Radiation Synthesis of Silver Nanoparticles/Chitosan for Controlling Leaf Fall Disease on Rubber Trees Causing by Corynespora cassiicola

Silver nanoparticles (AgNPs) were successfully prepared by γ-rays irradiation of solution containing 1.0–10 mM of silver nitrate and 1% chitosan. The optical characteristics and particles sizes of AuNPs were determined by UV-Vis spectra and TEM images, respectively. The size of AgNPs increased by the increase of silver concentration or the decrease of chitosan molecular weight in irradiated solution. The in vitro test showed that AgNPs inhibited the growth of Corynespora cassiicola on rubber-leaf extract media with the inhibitory efficiency of 52.1–100% by treatment of AgNPs with particle size from 15 to 5 nm, respectively. In addition, antifungal activity was found to reach ~100% by the addition of 90 ppm AgNPs. The in vivo foliar treatment of AgNPs on 9-month-old rubber plants showed that the treatment with 2.5–12.5 ppm AgNPs on tested plants after inoculation by spraying with C. cassiicola spores enhanced the rate of non-disease-infected plants from 6.0 to 93.3%, respectively, compared to the untreated control. The inhibition effect of AgNPs on fungal growth of C. cassiicola mycelial was also elucidated via SEM images. The AgNPs/chitosan synthesized by γ-irradiation is potentially promising to use as a fungicidal product for treating C. cassiicola, a serious pathogen fungus on rubber trees.

Structure of semiconducting versus fast-ion conducting glasses in the Ag-Ge-Se system.

The transition from a semiconductor to a fast-ion conductor with increasing silver content along the Agx(Ge0.25Se0.75)(100−x) tie line (0≤x≤25) was investigated on multiple length scales by employing a combination of electric force microscopy, X-ray diffraction, and neutron diffraction. The microscopy results show separation into silver-rich and silver-poor phases, where the Ag-rich phase percolates at the onset of fast-ion conductivity. The method of neutron diffraction with Ag isotope substitution was applied to the x=5 and x=25 compositions, and the results indicate an evolution in structure of the Ag-rich phase with change of composition. The Ag–Se nearest-neighbours are distributed about a distance of 2.64(1) Å, and the Ag–Se coordination number increases from 2.6(3) at x=5 to 3.3(2) at x=25. For x=25, the measured Ag–Ag partial pair-distribution function gives 1.9(2) Ag–Ag nearest-neighbours at a distance of 3.02(2) Å. The results show breakage of Se–Se homopolar bonds as silver is added to the Ge0.25Se0.75 base glass, and the limit of glass-formation at x≃28 coincides with an elimination of these bonds. A model is proposed for tracking the breakage of Se–Se homopolar bonds as silver is added to the base glass.

TiNiCuAg shape memory alloy films for biomedical applications

TiNi-based shape memory alloys (SMAs) have been largely utilized in stents, orthopedic endo-prostheses and orthodontic implants. While bacterial infection in medical implants is the most common complication, development of antibacterial TiNi-based SMAs is essential. In the present study, a novel antibacterial TiNiCuAg shape memory alloy film (SMAF) was successfully developed by adding silver into TiNiCu matrix. The structural and biological properties of TiNiCuAg SMAF, including crystal structures, phase transformation temperatures, shape memory effect, antibacterial ability and cell cytotoxicity, were systematically investigated. The results showed that the phase transformation temperature gradually decreased and silver started to precipitate with the increasing silver content. The single-stage B2 ↔ B19′ transformation occurred in TiNiCu and Ti51Ni43.5Cu4.5Ag1 films, while the two-stage B2 ↔ R ↔ B19′ transformation occurred in Ti49.6Ni42Cu6.9Ag1.5, Ti47.4Ni41.2Cu6.4Ag5.6 and Ti47.7Ni41.2Cu4.1Ag7 films. Moreover, compared to TiNiCu films, TiNiCuAg films performed the better shape memory effect with the increasing silver content. For antibacterial tests, the TiNiCuAg films with the Ag content of 5.6 at.% had the best antibacterial ability against S. aureus and E. coli compared to those of TiNi and TiNiCu films. For cytotoxicity assay, all films maintained good biocompatibility and revealed no cell toxicity for L929 cells. As a result, excellent antibacterial ability and good biocompatibility suggested that TiNiCuAg SMAFs had potential applications for medical implant to avoid bacterial infection.

Effect of Strain Rate on Joint Strength and Failure Mode of Lead-Free Solder Joints

In surface mount technology, the Sn-3.0Ag-0.5Cu solder joint has a shorter impact lifetime than a traditional lead–tin solder joint. In order to improve the impact property of SnAgCu lead-free solder joints and identify the effect of silver content on tensile strength and impact property, impact experiments were conducted at various strain rates on three selected SnAgCu based solder joints. It was found that joint failure mainly occurred in the solder material with large plastic deformation under low strain rate, while joint failure occurred at the brittle intermetallic compound layer without any plastic deformation at a high strain rate. Joint strength increased with the silver content in SnAgCu alloys in static tensile tests, while the impact property of the solder joint decreased with increasing silver content. When the strain rate was low, plastic deformation occurred with failure and the tensile strength of the Sn-3.0Ag-0.5Cu solder joint was higher than that of Sn-0.3Ag-0.7Cu; when the strain rate was high, joint failure mainly occurred at the brittle interface layer and the Sn-0.3Ag-0.7Cu solder joint had a better impact resistance with a thinner intermetallic compound layer.

Effect of composition and temperature on the second harmonic generation in silver phosphate glasses

We herein employ nonlinear laser imaging microscopy to explicitly study the dynamics of second harmonic generation (SHG) in silver iodide phosphate glasses. While glasses of this family have gained extensive scientific attention over the years due to their superior conducting properties, considerably less attention has been paid to their unique nonlinear optical characteristics. In the present study, firstly, it is demonstrated that SHG signal intensity is enhanced upon increasing silver content due to the random formation of silver microstructures within the glass network. Secondly, the SHG temperature dynamics were explored near the glass transition temperature (Tg) regime, where significant glass relaxation phenomena occur. It is found that heating towards the Tg improves the SHG efficiency, whereas above Tg, the capacity of glasses to generate second harmonic radiation is drastically suppressed. The novel findings of this work are considered important in terms of the potential employment of these glasses for the realization of advanced photonic applications like optical-switches and wavelength conversion devices.

The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses

The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses is studied. Multicomponent photosensitive glasses of the Na2O–ZnO–Al2O3–SiO2 system with photosensitizing agents (cerium, antimony, silver) and halogenides (fluorine and bromine) are synthesized. Ultraviolet irradiation and thermal treatment below the glass-transition temperature of the glasses cause the formation of silver molecular clusters, which exhibit luminescence in the visible and infrared regions. UV irradiation and thermal treatment of glasses above the glass-transition temperature lead to the growth of silver nanoparticles with plasmon resonance peak in the region of 420 nm. Further thermal treatment of glasses above the glass-transition temperature shifts the plasmon-resonance maximum by 70 nm to longer wavelengths, which is related to the growth of a crystalline shell consisting of mixed silver and sodium bromides on nanoparticles. This formation of a crystalline phase on colloidal centers results in a local increase in the refractive index of the irradiated region by +Δn ~ 900 ppm compared to the nonirradiated region. Photo-thermo-refractive glasses with increased silver concentration are promising photosensitive materials for creating holographic optical elements and devices for line narrowing and stabilizing filters, spectral beam combiners, and filters for increasing the spectral brightness of laser diodes. A positive change in the refractive index of Photo-thermo-refractive glasses provides the possibility of recording in them 3D waveguide and integrated-optical structures.

Understanding Wear Interface Evolution to Overcome Friction and Restrain Wear of TiAl–10 wt%Ag Composite

The main objective of this paper is to study wear interface evolution for analyzing the of friction and wear property of TiAl–10 wt%Ag composite. The results show that the friction coefficient and wear rate of TiAl–10 wt%Ag rapidly reduce at 0–25 min and rhythmically fluctuate at 25–60 min. TiAl–10 wt%Ag at 60–240 min obtains low friction and less wear. It is concluded that silver with the low shearing strength of about 125 MPa shows the eminent plastic deformation on wear interface. It effectively reduces friction resistance and material loss, cause TiAl–10 wt%Ag to obtain low friction coefficient, and less wear rate at 0–25 min. Increased silver content, reduces oxide content, and varies wear mechanisms cause the repeating variation of friction resistance and material loss, which results in the rhythmical fluctuation of friction coefficient and wear rate at 25–60 min. High silver contents exist on smooth wear interfaces, exhibit the eminent plastic deformation to lower friction and reduce wear. TiAl–10 wt%Ag obtains the low friction and less wear at 60–240 min.

Semiconducting Ge-Se-Sb-Ag chalcogenides as prospective materials for thermoelectric applications

Chalcogenide as thermoelectric materials have shown a large power factor to yield a high figure of merit. In this work we report the study of Ag doped Ge20Se60Sb20−xAgx(0 ≤ x ≤ 20at%) chalcogenide materials in thin film form for the thermoelectric behaviour in the temperature range 300–450K. Thin films have been prepared from the bulk samples by thermal evaporation. Electrical characterization analysis has also been reported. The dc conductivity increases while the activation energy decreases with the increase in Ag concentration. The type of the conductivity has been found to be p-type throughout the entire investigative temperature range where the sign of the thermoelectric power is positive. The concentration of the free carriers has been determined from dc conductivity and thermoelectric power measurements. The activation energy obtained from the thermoelectric power decreases while the power factor, which is one of the important thermoelectric parameters, increases with increasing silver content.

Polaronic transport in Ag-based quaternary chalcogenides

Low temperature resistivity measurements on dense polycrystalline quaternary chalcogenides Ag2+xZn1-xSnSe4, with x = 0, 0.1, and 0.3, indicate polaronic type transport which we analyze employing a two-component Holstein model based on itinerant and localized polaron contributions. Electronic structure property calculations via density functional theory simulations on Ag2ZnSnSe4 for both energetically similar kesterite and stannite structure types were also performed in order to compare our results to those of the compositionally similar but well known Cu2ZnSnSe4. This theoretical comparison is crucial in understanding the bonding that results in polaronic type transport for Ag2ZnSnSe4, as well as the structural and electronic properties of both crystal structure types. In addition to possessing this unique electronic transport, the thermal conductivity of Ag2ZnSnSe4 is low and decreases with increasing silver content. This work reveals unique structure-property relationships in materials that continue to be of interest for thermoelectric and photovoltaic applications.

Effect of Ag substitution on structural, magnetic and magnetocaloric properties of Pr0.6Sr0.4–xAgxMnO3 manganites

A systematic investigation on the structural, magnetic and magnetocaloric properties of Pr0.6Sr0.4–xAgxMnO3 (x=0.05 and 0.1) manganites was reported. Rietveld refinements of the X-ray diffraction patterns confirmed that all samples were single phase and crystallized in the orthorhombic structure with Pnma space group. Magnetic measurements in a magnetic applied field of 0.01 T revealed that the ferromagnetic-paramagnetic transition temperature TC decreased from about 293 to 290 K with increasing silver content from x=0.05 to 0.1. The reported magnetocaloric entropy change and relative cooling power for both samples were considerably remarkable with a ΔSmax value of 1.9 J/(kg·K) and maximum RCP values of 100 J/kg, under a magnetic field change (Δµ0H) equal to 1.8 T. The analysis of the universal curves gave an evidence of a second order magnetic transition for the studied samples. The magnetic field influence on both the magnetic entropy change and the relative cooling power was also studied and discussed.

Magnetically Recoverable and Reusable Antimicrobial Nanocomposite Based on Activated Carbon, Magnetite Nanoparticles, and Silver Nanoparticles for Water Disinfection

Recent advancements in nanotechnology have led to the development of innovative, low-cost and highly efficient water disinfection technologies that may replace or enhance the conventional methods. In this study, we introduce a novel procedure for preparing a bifunctional activated carbon nanocomposite in which nanoscale-sized magnetic magnetite and antimicrobial silver nanoparticles are incorporated (MACAg). The antimicrobial efficacy of the nanocomposite was tested against Escherichia coli (E. coli). MACAg (0.5 g, 0.04% Ag) was found to remove and kill 106–107 CFU (colony-forming units) in 30 min via a shaking test and the removing and killing rate of the nanocomposites increased with increasing silver content and decreased with increasing CFU. The inhibition zone tests revealed, among the relevant components, only Ag nanoparticles and Ag+ ions showed antimicrobial activities. The MACAg was easily recoverable from treated water due to its magnetic properties and was able to remove and kill 106 CFU after multiple-repeated use. The MACAg nanocomposite also demonstrated its feasibility and applicability for treating a surface water containing 105 CFU. Combining low cost due to easy synthesis, recoverability, and reusability with high antimicrobial efficiency, MACAg may provide a promising water disinfection technology that will find wide applications.