Influence Of Silver Ions Research Articles

The Influence of Silver Ions on the Dielectric Dispersion Dipolar Relaxation Dynamics and Dielectric Breakdown Strength of Zinc Selenium Phosphate Glass System

Herein, a study on the dielectric properties of ZnO–P2O5–SeO2 glass ceramics containing varied contents of Ag2O is presented. Structural analysis of the samples by X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, Fourier transform infrared spectra, and optical absorption techniques indicated that the glasses are embedded with Ag3PO4, Ag2SeO3, and Zn3(PO4)2 anisotropic crystal phases along with Ag+ ions and Ag0 particles. Dielectric properties, ac conductivity (σac), and dielectric breakdown strength (DBS) are investigated as functions of Ag2O concentration. The results show the maximal concentration of Ag+ ions and Ag0 metallic particles in the sample containing 0.6 mol% of Ag2O. Dielectric parameters and (σac) increase with increasing Ag2O up to 0.6 mol%, while the DBS and electrical impedance decrease. The observed dipolar effects are quantitatively analyzed and possible dipoles are identified. Ionic contribution is predominant up to 0.6 mol% of Ag2O, beyond which the polaronic tunneling phenomenon prevails. These findings indicate that 0.6 mol% of Ag2O is the optimal concentration for using these glass ceramics as solid electrolytes in ionic batteries. Moreover, glass ceramics containing Ag2O beyond 0.6 mol% have exhibited larger polaronic conductivity, hence such glasses can be considered suitable candidates for electrodes in ionic batteries.

Antibacterial and physical characteristics of silver-loaded hydroxyapatite/alginate composites

The influence of silver ions on the antibacterial properties and morphology of hydroxyapatite-silver (HA-Ag) and hydroxyapatite-alginate-silver (HA-Alg-Ag) nanocomposites was studied. The microstructure and phase composition of the obtained nanocomposites were investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and Fourier transform infrared spectroscopy, and the formation of the crystalline phase of Ag3PO4 was proved. According to the results, silver ions were incorporated into the HA structure, partially replacing calcium ions. Assessment of the antimicrobial activity was carried out on Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacterial test cultures by the co-incubation and modified agar diffusion methods. We demonstrated that the antimicrobial and adhesive properties of both Ag-HA and HA-Alg-Ag are strongly affected by the crystal lattice structure, controlled by the location of silver ions. The composite materials could be of great interest in the biomedical field, including in the design of coatings that prevent or slow the development of bacterial biofilms.

The Influence of Different Forms of Silver on Selected Pathogenic Bacteria.

The application of silver nanoparticles as an antibacterial agent is becoming more common. Unfortunately, their effect on microorganisms is still not fully understood. Therefore, this paper attempts to investigate the influence of silver ions, biologically synthesized silver nanoparticles and nanoparticles functionalized with antibiotics on molecular bacteria profiles. The initial stage of research was aimed at the mechanism determination involved in antibiotics sorption onto nanoparticles’ surface. For this purpose, the kinetics study was performed. Next, the functionalized formulations were characterized by Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS) and a zeta potential study. The results reveal that functionalization is a complex process, but does not significantly affect the stability of biocolloids. Furthermore, the antimicrobial assays, in most cases, have shown no increases in antibacterial activity after nanoparticle functionalization, which suggests that the functionalization process does not always generate the improved antimicrobial effect. Finally, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) technique was employed to characterize the changes in the molecular profile of bacteria treated with various antibacterial agents. The recorded spectra proved many differences in bacterial lipids and proteins profiles compared to untreated cells. In addition, the statistical analysis of recorded spectra revealed the strain-dependent nature of stress factors on the molecular profile of microorganisms.

Influence of silver ions in Eu3+ doped glass for efficient reddish-orange and white light generation

Abstract Borophosphate glasses containing Ag and Eu3+ ions are prepared by melt-quenching method and spectroscopically characterized. Through ATR-FTIR and Raman spectra, the structural behaviour of groups PO4 and BO4 of the glasses were discussed. Using UV-Vis absorption spectra and Judd-Ofelt (J-O) theory, the J-O intensity parameters (Ω2, Ω4 and Ω6) and radiative properties of excited states of Eu3+ ions in borophosphate: Eu and borophosphate: Eu/Ag were calculated. Excitation spectra at 230, 250 nm and 355 nm exhibited broadband emissions in the UV and visible ranges (260–440 nm and 430–500 nm) which were associated to single Ag+ ions and Ag+- Ag0 pairs. Moreover, enhancement of the Eu3+ emission at 612 nm was observed with increasing Ag concentration. The effect was attributed to the energy transfer between Ag species and Eu3+ ions, with a maximum enhancement factor of 4 times. Under 355 nm and 388 nm excitations, warm-white light and reddish-orange emissions were accomplished that may potentially be used in w-LEDs.

Catalytic effect of silver on copper release from chalcopyrite mediated by Acidithiobacillus ferrooxidans

Although silver ion in the solution is an important factor affecting the biodissolution of chalcopyrite, the effect of silver ion on the release of copper ion from chalcopyrite to the environment has not been explored until now. In order to fill this knowledge gap, the effect of silver ion on copper release from chalcopyrite in the presence of Acidithiobacillus ferrooxidans was investigated. The results indicate that silver ion significantly enhanced chalcopyrite biodissolution, thereby releasing more copper ion. In turn, this indicates that the release of copper ion from chalcopyrite to the environment was increased under these conditions. Biodissolution results, bacterial adsorption experiments, elemental composition analysis, and electrochemical analysis reveal that the enhancement of silver ion on copper ion release from chalcopyrite was mainly attributed to the improvement of electrochemical activity of chalcopyrite and the inhibition of the formation of passivation layer (Sn2−/S0) on the chalcopyrite surface. This study provides a better understanding of the effect of silver ion on the release of copper ion from chalcopyrite to the environment. In the future, the influence of silver ion on chalcopyrite biodissolution should be considered in the evaluation of copper ion pollution to ensure reliability.

Synthesis of Small Gold Nanorods and Their Subsequent Functionalization with Hairpin Single Stranded DNA.

Small gold nanorods have a significantly large absorption/scattering ratio and are especially beneficial in exploiting photothermal effects, for example in photothermal therapy and remote drug release. This work systematically investigates the influence of growth conditions on the size, growth yield, and stability of small gold nanorods. The silver-assisted seed-mediated growth method was optimized to synthesize stable small gold nanorods with a high growth yield (>85%). Further study on the influence of silver ions on the growth facilitates the growth of small gold nanorods with tunable longitudinal surface plasmon resonance from 613 to 912 nm, with average dimensions of 13–25 nm in length and 5–6 nm in diameter. Moreover, the small gold nanorods were successfully functionalized with thiol-modified hairpin oligonucleotides (hpDNA) labeled with Cy5. Fluorescence intensity measurements show an increase in the presence of target DNA and an enhanced signal/background ratio when the longitudinal surface plasmon resonance of small gold nanorods overlaps with the excitation and emission wavelength of Cy5. This coincides with a reduced fluorescence lifetime of Cy5 in the hairpin structure, indicating surface plasmon resonance-enhanced energy transfer to the small gold nanorods. This study may provide insight on the synthesis and functionalization of small gold nanorods in biomedical sensing and therapy.

Influence of silver ions on bioleaching of cobalt from spent lithium batteries

The influence of silver ions (Ag+) on the bioleaching of cobalt from spent lithium batteries using Acidithiobacillus ferrooxidans (A. ferrooxidans) bacteria was investigated. The best effect was observed at Ag+ concentration of 0.02g/L, and the amount of leached cobalt was 98.4% in a period of 7days, whereas in the absence of Ag+, the amount of leached cobalt was only 43.1%. Based on the results of SEM, XRD and EDX investigation, it is deduced that Ag+ first reacted with cobalt to form AgCoO2 as an intermediate. A mechanism that is based on catalytic interactions is proposed to explain the enhanced leaching of Co using A. ferrooxidans.

Gold nanorods with finely tunable longitudinal surface plasmon resonance as SERSsubstrates

Advances in nanophotonics have shown the potential of colloidal metal nanoparticles withsharp tips, such as rods, to focalize plasmonic electromagnetic fields. We report onthe synthesis of Au nanorods via a seed mediated approach and the influenceof silver ions on the aspect ratio of the Au nanorods. The longitudinal surfaceplasmon resonance (LSPR) of the Au nanorods was successfully tuned with theconcentration of silver ions. The surface enhanced Raman scattering (SERS)effect of 2-aminothiophenol (2-ATP) as a probe molecule on Au nanorods wassystematically studied by varying the longitudinal surface plasmon resonance ofthe nanorods. The highest electromagnetic enhancement was observed when thelongitudinal surface plasmon resonance of the Au nanorods overlapped with the laserexcitation wavelength. The variation of the SERS enhancement factor with thelongitudinal surface plasmon resonance and laser excitation lines is also discussed indetail.

Experimental switching of copper status in laboratory rodents

There is an emerging link between copper metabolism, tumor growth and efficiency of antitumor treatment with platinum drugs or copper chelators. So there is an urgent need for well-defined and reproduced animal models with different states of copper metabolism. In the present study an animal model (rats and mice) with switching copper status in blood serum (copper concentration, oxidase activity and ceruloplasmin (Cp) protein content) is characterized. The drop of copper status is caused by addition of AgCl to fodder (Ag-animals). In rats and mice, the influence of silver ions on oxidase and ferroxidase activity of blood serum is similar, but copper concentration is reduced by 90% in rats, and by 60% in mice. The absorbed silver ions are transported to liver cells and included to Cp polypeptides, which are secreted to blood serum then. Cp, which circulates in bloodstream of Ag-animals contains silver atoms, and is misfolded, as judged by circular dichroism spectroscopy and differential scanning calorimetry. Single intraperitoneal or per oral injection of Cu(II) salt to Ag-animals causes recovery of oxidase and ferroxidase activity of blood serum within 4 hours in both rodent species, presumably by rapid metabolic insertion of copper into forming Cp in liver. The recovered copper status persists for 3 days under the continuing Ag-diet. The possibilities of use of Ag-rodents with switching copper status in investigation of influence of copper status on tissue-specific intracellular copper metabolism and role of copper in tumor genesis, bone metabolism and neurodegenerative diseases are discussed.

Atomic force microscopy investigation of the characteristic effects of silver ions on Escherichia coli and Staphylococcus epidermidis

The influence of silver ions on Escherichia coli and Staphylococcus epidermidis has been investigated by atomic force microscopy (AFM). Both single cell and cell communities were visualized, and the nanoscale ultrastructure images of these two bacteria strains before and after stimulation of silver ions were obtained. The results showed that in the case of E. coli after treatment with silver ions, vesicles appeared on the cell walls, and the size of vesicles became larger with the increase of the incubation time. However, in the case of S. epidermidis after treatment with silver ions, irregular and deep grooves appeared on the cell walls, and the cytoplasm membrane shrank and became separated from the cell wall. The significant differences in cell wall changes between E. coli and S. epidermidis after treatment with silver ions were related to their structural characters. According to those results, it is shown that AFM can provide new insight into the antimicrobial mechanism of silver ions, and show a new methodological approach to understand the relationship between structure and function of microbial cell when it was exposed to external stimulation.

Influence of silver ions on the growth mode of platinum on gold nanorods

Gold nanorods were used as seeds for platinum growth, using a mild reducing agent, ascorbic acid, in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB). Highly preferential growth on the tips or complete overcoating can be achieved by manipulation of the reduction conditions, among which the presence of silver ions was found to be highly dominant. In either case, the growth was found to be epitaxial, as demonstrated by high resolution electron microscopy and Fourier transform analysis. Additionally, the deposition mode leads to very different effects on the optical properties of the nanoparticles, with tip growth inducing huge surface plasmon red shifts.

Reaction of Bromous Acid with Bromide in the Presence of Silver Ions

Abstract The reaction HBrO2 + Br- + H + →2 HOBr, which is the most important control reaction in the Belousov-Zhabotinsky (BZ) system, is investigated in competition to the AgBr precipitation reaction Ag+ + Br- →AgBr. It turns out that the bromite-bromide reaction starts even in the presence of Ag+ in high concentration; the rate of consumption of bromite by bromide, however, is slowed down significantly if silver ions are present in the system. The experiments reveal that the AgBr precipita­ tion reaction proceeds in a series of several steps, starting with a fast equilibrium. This way different experimental results on the influence of silver ions on the kinetics of the BZ reaction may now be better understood.

The influence of silver ion on the electrochemical response of chalcopyrite and other mineral sulfide electrodes in sulfuric acid

The electrochemical behavior of chalcopyrite electrodes in H 2SO 4 solutions with and without silver ion has been investigated and has provided additional information concerning the enhanced or catalyzed leaching rates previously observed for the ferric sulfate leaching of CuFeS 2 in the presence of Ag +. A careful analysis of the cyclic voltammetry for CuFeS 2 electrodes in the presence of silver ion, indicates the formation of Ag 2S and metallic silver on the chalcopyrite surface, and that cyclic voltammetry for CuFeS 2 in solutions containing Ag + is an integration of the electrochemical responses for CuFeS 2 and Ag 2S. Consistent with previously reported leaching responses, additions of Ag + up to an optimum of approximately 10 -3M result in higher anodic currents for CuFeS 2 electrodes Concentrations of 10 -3M and larger cause a decrease in current which is attributed to the precipitation of Ag 2SO 4. The effect of Ag + on the individual anodic and cathodic half cell reactions has also been examined by means of a dual cell apparatus and has shown that added silver affects the anodic dissolution reaction and has no effect on the cathodic half cell, i.e. the Fe 2+/Fe 3+ couple. These results along with mass balances performed at constant anodic potential are considered in the context of reactions between CuFeS 2 and added silver which are indicated. The apparent catalysis is believed to occur through a change in morphology or conductivity of the normally protective sulfur layer which forms on CuFeS 2 through reactions involving Ag 2S or elemental silver. A preliminary exploration of other systems in which catalysis or enhancement may be found has also been briefly investigated using ZnS and PbS electrodes.