Silver Ion Exchange Research Articles

Sensitive immunoassay for porcine pseudorabies antibody based on fluorescence signal amplification induced by cation exchange in CdSe nanocrystals

We report on a novel immunoassay for porcine pseudorabies virus (PRV) antibody that is based on fluorescence signal amplification induced by silver(I) ion exchange in CdSe nanocrystals. An antigen-antibody-secondary antibody sandwich structure was first formed from PRV, PRV antibody, and CdSe-labeled rabbit anti-pig antibody. Then, the Cd(II) ions in the CdSe labels were released by a cation exchange reaction with Ag(I). Released Cd(II) was finally quantified using the sensitive fluorescent probe Rhodamine 5 N. Due to this signal amplification, the sensitivity and linear range of the immunoassay were largely improved (compared to the traditional ELISA) in having a limit of detection as low as 1.2 ng mL−1 of PRV antibody and a linear range from 2.44 to 312 ng mL−1. The successful determination of PRV antibody in pig serum samples is proof for the utility of the method.

Preparation and Characterization of AgA Zeolite/Polysulfone Membranes

In present study, a few polysulfone composite membranes with the introduction of silver ion-exchange treated zeolite were prepared and evaluated by several characterization methods. Regularly-ordered zeolite particles were generally finely dispersed in the continuous PSF phase with appreciated organic-inorganic interfacial interactions as reflected by SEM and FTIR results. Gas permeation test shows that after incorporating zeolite the polysulfone membrane exhibits significantly decreased gas permeability for H2, N2, and CO2 whereas they show increased permselectivity for CO2/N2, H2/CO2 and H2/N2 gas pairs as compared to neat polysulfone membrane.

Irreversible Silver(I) Interconversion in Ag:ZSM-5 and Ag:SAPO-5 by Propene and Hydrogen

Hydrogen reportedly enhances the activity of silver catalytic systems for the selective catalytic reduction (SCR) of nitrogen oxides by hydrocarbons. This can be ascribed to the formation of silver nanoclusters, which act as active sites for removing NOx. Two bifunctional catalysts were prepared by initial conventional and hydrothermal silver(I) ion exchange of two microporous systems to form Ag:ZSM-5 and Ag:SAPO-5. The redox behavior of the metal for the SCR deNOx process was monitored using either propene or hydrogen as the reducing agents. Reversibility in NO was also investigated with the emphasis of identifying the reoxidized silver species. XAS was used to establish reversibility between ion-exchanged silver(I) and silver metallic particles formed during the process. It is evident that silver(I) is reduced by both hydrogen and propene to metallic silver nanoclusters in both the Ag:ZSM-5 and the Ag:SAPO-5 systems. A promoting effect of H2 for the SCR-HC deNOx process is believed to be the reduction o...

The influence of ETFs on the price discovery of gold, silver and oil

In this study we examine gold, silver and oil exchange traded funds (ETFs) and their relation to their respective futures instruments and underlying commodities by using intradaily data. We find that the gold, silver and oil ETFs closely track the performance of their underlying assets by using tracking error and pricing deviation metrics. It has been documented in the finance literature that price discovery occurs in the futures market. We test whether in recent times the existence of ETFs has changed the dominating role of the futures market in price discovery. We find that the availability of ETFs has shifted price discovery for gold and silver to the ETF market, while the oil market has price discovery occurring still predominantly in the futures market.

Ag nanoparticles embedded in glass by two-step ion exchange and their SERS application

Silver nanoparticles embedded in glass are prepared by a two-step ion exchange process, where silver ions are introduced into glass in silver ion exchange, and reduced into metallic silver in subsequent potassium ion exchange. The formation of the particles can be explained by the combination effect of the galvanic replacement reaction and the electrolytic deposition. The formed particles are characterized by optical absorption measurements, transmission electron microscopy and atomic force microscopy. Their application in SERS is demonstrated, and the optimal surface features in terms of SERS enhancement are also discussed.

The ‘Galleon System’ and Chinese Trade in Manila at the Turn of the 16th Century

When the mission of the Basque adelantado Miguel López de Legazpi reached Luzon – the northernmost isle of the Philippine archipelago – in 1570, the ambitious Spanish conquistadores met the ‘Sangley’ merchants for the first time. During the 1570s many Chinese junks started to connect Manila with the ports of Fujian province and transformed the Philippine capital in a crossroads of the silk to silver exchange between China, Japan and the two Americas. Following the establishment of the Manila-Acapulco-Callao triangular trade line and with the influx of the precious ‘reals of eight’ from Mexico, the so-called ‘Naos de China’ started to enrich both the Spaniards and the ‘Sangleys’, triggering an irreversible process that led to the establishment of a ‘Galleon System’ in just two decades. This paper will discuss the role of Chinese trade in the Philippines at the close of the 16th century from the founding of Manila in 1571 to the establishment of the ‘Galleon System’ by the early 1590s.

La reforma monetaria de 1905 y la flexibilización de los medios de pago en México

This essay explores an important phase in the historical evolution of the Mexican monetary system, stressing the relationship between its reformation of 1905 and the operation of the bank system. Besides revising previous literature, it also studies the perception Mexican authorities had of the presumed inexorability of the Silver Exchange Standard in relation to the Gold Exchange Standard, linking it as much to national interests as to the international situation. Some of the problems of the delay with which the reformation was adopted were technical and to solve them authorities created a regulation fund that had an unexpected success due to external phenomena. This success seemed to guarantee the flexibility of the monetary system; however it also postponed the reformation of the financial system. This delay in addition to the theoretical convictions of those “regulators” left open the way to new channels of uncertainty.

Ion exchange behaviour of silver-doped apatite micro- and nanoparticles as antibacterial biomaterial

Hydroxyapatite (HAp) micro- and nanoparticles have been widely used as highly promising bioactive materials in different ways because of their bone growth induction. As microbial infection of HAp might be frequently occurred, silver (Ag) can be doped in the HAp lattice to enhance the antimicrobial properties. Herein, Ag-doped HAp was successfully synthesised through an ion exchange reaction. This study describes experiments on the preparation and testing of Ag-loaded HAp as an antibacterial biomaterial. The effects of synthesis conditions such as maturation state and silver ion exchange were investigated on the samples by the Taguchi method. Also, chemical analysis was conducted by atomic absorption spectrophotometers, and the antibacterial activity of the prepared samples against bacterium of Escherichia coli was tested. The effectiveness of the material depends upon the synthesis conditions that were assessed statistically. In addition, the material was examined by scanning electron microscopy and its antibacterial action given a physical basis. Finally, the obtained results indicated that maturation caused an increase in the homogeneity of particles, with a decrease in silver absorption ability and antibacterial activity.

Optical waveguides formed by silver ion exchange in Schott SG11 glass for waveguide evanescent field fluorescence microscopy: evanescent images of HEK293 cells

Planar glass waveguides with a specific number of modes were fabricated by Ag(+)-Na(+) exchange in Schott SG11 glass. The effective refractive indices were determined using m-line spectroscopy in both s- and p-polarization. By using the reversed Wentzel-Kramers-Brillouin approximation, the index profiles were described by a nonlinear diffusion equation. The diffusion coefficients for Ag(+) were established, as well as the penetration depth of the evanescent field in an aqueous environment for the different modes. The integrals of \E\(2) fields for the evanescent-guided fields were investigated. These are important when evanescent fields are used for illumination in interface microscopy, an alternative method to total internal reflection fluorescence (TIRF) microscopy. The photoluminescent behavior of the waveguides was investigated as a function of ion exchange time and excitation wavelengths. Comparable images were obtained of fluorescently labeled HEK293 cells using TIRF microscopy and waveguide evanescent field fluorescence microscopy. Imaging was performed using HEK293 cells, delivering similar images and information.

Magnetic Multi‐Functional Nano Composites for Environmental Applications

AbstractA novel concept is proposed to synthesize a new class of composites featuring magnetic, molecular sieve and metallic nanoparticle properties. These multi‐functional materials have potential applications as recyclable catalysts, disinfectants and sorbents. The magnetic property enables effective separation of the spent composites from complex multiphase systems for regeneration and recycle, safe disposal of the waste and/or recovery of loaded valuable species. The zeolite molecular sieve provides a matrix which supports a remarkably new, simple, efficient and economical method to make stable, supported silver nanoparticles by silver ion exchange and controlled thermal reduction. The silver nanoparticles generated in this way have excellent properties such as high reactivity and good thermal stability without aggregation, which act as nano reactors for desired functionality in a wide range of applications. Magnetic component (Fe3O4), molecular sieve matrix (zeolite) and silver nanoparticles generated by ion exchange followed by controlled reduction, together form this unique novel composite with designed functions. It represents a practically operational, economical, sustainable and environmentally friendly new advanced functional material. This paper focuses on the novel synthesis and characterization of the composite, with an example of applications as sorbents for the removal of vapor‐phase mercury from the flue gas of coal‐fired power plants.

Antibacterial properties of nanostructured silver titanate thin films formed on a titanium plate

Antibacterial activity of various surfaces against methicillin-resistant Staphylococcus aureus (MRSA) was studied. Sodium titanate thin film with a porous network structure and sodium titanate nanotube thin film were formed on titanium surfaces through the reaction of titanium plates with NaOH solutions. Through a silver ion-exchange treatment, Na(+) ions in sodium titanate were exchanged with Ag(+) ions in silver acetate solution, along with the loading of silver nanoparticles on the titanate surfaces. Results of silver ion elution tests of the thin films in fetal bovine serum solution indicate that the release period and the number of silver ions released from the silver titanate thin films can be controlled by altering the crystal structure, nanostructure, and thickness of the titanate phase. The silver ion-exchanged titanate thin films showed high antibacterial activity against MRSA. It was also revealed that although the crystal structure of titanate itself has no large antibacterial effect, higher antibacterial activity mainly arises from the silver ions held in the interlayer spacing of the titanate. The obtained results should aid the development of more convenient and inexpensive antibacterial implants.

Preparation and Characterization of Nano-Sized Silver Particles

This study presents an approach to prepare nano-sized silver particles via in-situ reduction process. First, a reversible addition fragmentation chain transfer (RAFT) agent, 2-(dodecylthiocarbonothioylthio)propanoic acid (DTPA), was synthesized and characterized. Acrylic acid (AA) was polymerized in the presence of DTPA to afford an amphiphilic macro RAFT agent (DTPA-AC-10) with a calculated average degree of polymerization of ten. Latex particles with a sodium salt-containing shell were prepared by using sodium DTPA-AC-10 as a reactive surfactant. Then, through silver ion-exchange processs of the latex particles, the latex particles with silver salt at the surface were obtained. Finally, the silver salt at the particle surface was reduced through chemical reduction to give the silver-coated polymer particles. Dynamic Laser Scattering (DLS) was used to measure the particle size and distribution; X ray diffraction analysis (XRD) was employed to characterize the formed silver crystal in the particle surface. The diameter of the silver particles was about 76 nm and was narrowly distributed. The silver nanoparticles might be used to prepare conductive ink for ink-jet applications.

The partitioning behavior of silver in a vapor–brine–rhyolite melt assemblage

The partitioning of silver in a sulfur-free rhyolite melt–vapor–brine assemblage has been quantified at 800 °C, pressures of 100 and 140 MPa and f O 2 ≈ NNO (nickel–nickel oxide). Silver solubility (±2 σ) in rhyolite increases 5-fold from 105 ± 21 to 675 ± 98 μg/g as pressure increases from 100 to 140 MPa. Nernst-type partition coefficients ( D Ag i , j ± 2 σ ) describing the mass transfer of silver at 100 MPa between vapor and melt, brine and melt and vapor and brine are 32 ± 30, 1151 ± 238 and 0.026 ± 0.004, respectively. At 140 MPa, values for D Ag i , j ( ± 2 σ ) for vapor and melt, brine and melt, and vapor and brine are 32 ± 10, 413 ± 172 and 0.06 ± 0.03, respectively. Apparent equilibrium constant values (±2 σ) describing the exchange of silver and sodium between vapor and melt, K Ag , Na v / m , at 100 and 140 MPa are 105 ± 68 and 14 ± 6. The average values (±2 σ) for silver and sodium exchange between brine and melt, K Ag , Na b / m , at 100 and 140 MPa are 313 ± 288 and 65 ± 12. These data indicate that the mass transfer of silver from rhyolite melt to an exsolved volatile phase(s) is enhanced at 100 MPa relative to 140 MPa, suggesting that decompression increases the silver ore-generative potential of an evolving silicate magma. Model calculations using the new data suggest that the evolution of low-density, aqueous fluid (i.e., vapor) may be responsible for the the silver tonnage of many porphyry-type and perhaps epithermal-type ore deposits. For example, Halter et al. (Halter W. E., Pettke T. and Heinrich C. A. (2002) The origin of Cu/Au ratios in porphyry-type ore deposits. Science 296, 1842–1844) used detailed silicate and sulfide melt inclusion and vapor and brine fluid inclusions analyses to estimate a melt volume on the order of 15 km 3 to satisfy the copper budget at the Bajo de la Alumbrera copper-, gold-, silver-ore deposit. Using their melt volume estimate with the data presented here, model calculations for a 15-km 3 felsic melt, saturated with pyrrhotite and magnetite, suggest that a low-salinity magmatic vapor may scavenge on the order of 7 × 10 12 g of silver from the melt. This quantity of silver exceeds the discovered 2 × 10 9 g of Ag at Alumbrera. Calculated tonnages for numerous other deposits yield similar results. The excess silver in the vapor, remaining after porphyry formation, is then available to precipitate at lower PTconditions in the stratigraphically higher epithermal environment. These data suggest that silver, and perhaps other ore metals, in the porphyry-epithermal continuum may be derived solely from the time-integrated flux of dominantly low-salinity vapor exsolved from a series of sequential magma batches.

Phosphate glasses for GRIN structures by ion exchange

Abstract Phosphate glasses were treated as a material for GRIN-lens production by silver-alkaline ion exchange. Glass durability (in salt melts) known to be a general obstacle for using these glasses in ion exchange technologies was found to profoundly increase in the sequence of meta ⇒ piro ⇒ orthophosphate. It is supposed to be due to the structure of phosphate glasses, which transforms in this sequence from 1D to 3D space arrangement of the glass-forming network. Ion exchange properties of these glasses were studied as well, and the maximal index variation in sodium–silver ion exchange was found to be 0.17.

Study on the structure and antibacterial activity of silver-carried zirconium phosphate

The structure and antibacterial activity of silver-carried zirconium phosphate (AgZrP) were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and viable cell counting method. There existed the exchange of sodium ions with silver ions in carrier, and the silver in AgZrP was in ionic state. Moreover, no significant changes in crystal structure of carrier were found by the exchange of silver ions except for its crystal space distance and crystallinity. The antibacterial tests showed that 100 mg l − 1 of AgZrP possessed high antibacterial activity and was capable of killing all the Escherichia coli ( E. coli) and more than 99.9% of the Staphylococci aureus ( S. aureus) within 8.0 h of contact.

Structure and antibacterial activity of new layered perovskite compounds

New layered perovskite compounds, Ag xNa 2-xLa 2Ti 3O 10 ( x=0.2,0.3 and 0.5) were synthesized by an ion-exchange reaction of Na 2La 2Ti 3O 10 with AgNO 3 solution and characterized by energy dispersive X-ray analysis(EDX), X-ray diffractometry(XRD), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). The ion-exchange processes were optimized, and the antibacterial activity, light permanency and water-resistance were evaluated. Surprisedly, no significant changes in crystal structure of Na 2La 2Ti 3O 10 are found by the exchange of silver ions. The Ag 0.3Na 1.7La 2Ti 3O 10 particles conglomerate obviously with irregular shape and size. Ag 0.3Na 1.7La 2Ti 3O 10, possessing the minimum inhibitory concentrations(MICs) against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) of 180 mg/L and 240 mg/L, has high antibacterial activity, good light permanency and water-resistance. The ionic state silver in Ag xNa 2-xLa 2Ti 3O 10 is the antibacterial active component.

Systematic modeling study of channel waveguide fabrication by thermal silver ion exchange

A systematic study of thermal silver ion exchange used for the fabrication of optical channel waveguides is reported in a single-alkali glass. The diffusion equilibrium and diffusion dynamics are experimentally studied, and the concentration-dependent diffusion coefficients are determined. The relationship between the fabrication conditions, i.e., time, temperature, and melt concentration, and the induced waveguide refractive index profile is established. It is demonstrated that the diffusion equation can be solved, without use of any free parameters, to predict the refractive index profiles of both planar and channel waveguides. A 1.6 cm diameter integrated optic ring resonator, with a propagation loss of 0.1 dB/cm, is fabricated in a glass by thermal silver ion exchange. The induced refractive index profile is related to the optical characteristics of the functional device.

Preparation and study of superficially coloured lead glass

Superficially coloured lead crystal glass was obtained by ion-exchange with silver. Both red and yellow ruby colouring were achieved by the presence of small silver particles (colloids) dispersed into the ion-exchanged glass surface. Direct silver ion-exchange of the glass yielded yellow colouring (optical absorption around 410 nm). Silver ion-exchange of lead glass previously doped with a reducing agent (i.e., arsenic oxide) yielded red colouring, (optical absorption around 600 nm), which indicated special arrangement for silver colloids in the exchanged layer. Parameters that influenced the ion-exchange process, such as temperature, exchange time, dopant percentage and composition of molten salts bath (where the ion-exchange took place), were examined in order to select the best conditions to obtain colours with decorative interest. Optical absorption spectroscopy and scanning electron microscopy were used to determine colour coordinates and silver diffusion profiles, respectively. Direct observation of the silver colloids were performed by means of transmission electron microscopy. Finally, once the optimum process parameters were tested, an intense red ruby colouring (more than 98% colour purity) was reached. Industrial application of this process arises positively, since some handicaps from traditional bulk colouring could be avoided.

Prism coupling characterization of planar optical waveguides made by silver ion exchange in glass

Laboratorio de Optica Integrada, Facultad de Ciencias, Universidad de Oviedo, Spain Received 11 October 2004, revised 6 May 2005, accepted 3 June 2005 Published online 29 July 2005 PACS 02.30.Zz, 07.05.Hd, 42.79.Gn, 78.20.Bh, 78.20.Ci, 82.39.Wj A modified dark-lines method of prism-coupling technique is utilized for the experimental determination of the effective index of propagating modes in a glass planar waveguide. We use to make the waveguides a silver-sodium ion exchange in a nitrate solution and sodalime glass as substrate (microscope slides). The measurements were accomplished by direct HeNe laser beam incidence and sensing the reflected light by a Thorlabs Dec110 optical detector linked to a Protek500 digital multimeter. A LabView virtual instru-ment was implemented for the automation of the measurement process. The effective indexes measured have been used to calculate the refractive index profile by IWKB method. A comparison with other results shows that our experimental setup is suitable for slab waveguide modes characterization.

Exchange of sodium and silver ions in Na3Sc2(PO4)3 single crystals

Sodium-and silver-ion exchange in single crystals of two polymorphous modifications of the Na3Sc2(PO4)3 compound has been studied. It is established that in the process of ion exchange, the samples undergo phase transitions similar to the well-known temperature transformations observed in these systems. It is shown that the phases with ferroelectric, ionic, and superionic properties may simultaneously coexist in one sample.