Results 1 - 10 of 2326
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[en] We have demonstrated the colorimetric chemosensor for detection of Ag+ via formation of nanoparticles which is based on the intramolecular CT interaction between the electron-rich (2,6-dialkoxynaphthalene; Np) moiety and the electron-deficient (methyl viologen; MV2+) moiety of a single sensor molecule. Under irradiation of light, Ag+ was reduced to very small silver nanoparticle by CT interaction in the presence of OEGs as flexible recognition moiety of Ag+ and stabilizer for Ag nanoparticles, thus Ag nanoparticles resulted to reddish brown in the color change of sensor solution, gradually. Therefore, the charge-transfer interaction between an electron-deficient and an electron-rich units existing at a sensor molecule can be regarded as a new and efficient method to construct various colorimetric chemosensors. Donor.acceptor interactions or charge transfer (CT) interactions are an important class of non-covalent interactions and have been widely exploited in self-assembling systems. Beyond molecular chemistry, supramolecular chemistry aims at constituting highly complex, functional chemical systems from components held together by intermolecular forces. Chemosensors are the molecules of abiotic origin that bind selectively and reversibly with the analyte with concomitant change in one or more properties of the system. The recognition and signaling of ionic and neutral species of varying complexity is one of the most intensively studied areas of contemporary supramolecular chemistry
[en] Precipitation and solvent extraction methods have been investigated for the purification of plutonium from silver from the solution generated during oxidative dissolution of plutonium oxide using Ag(II) ions. Initial experiments have been carried out using thorium as representative of plutonium. Selecting the optimum conditions, the experiments were repeated with plutonium. The results revealed that Pu can be purified from silver ions either by precipitating silver as silver chloride or silver metal followed by Pu(IV) oxalate precipitation or by selective extraction of Pu(IV) into 20% Aliquat-336 or 30% TBP. (author)
[en] A PVC membrane electrode for silver ion based on a new cone shaped calixarene (CASCA) as membrane carrier was prepared. The electrode exhibits a Nernstian response for Ag+ over a wide concentration range (1.0 x 10-1-8.0 x 10-6 M) with a slope of 58.2 ± 0.5 mV per decade. The limit of detection of the sensor is 5.0 x 10-6 M. The sensor has a very fast response time (∼5 s) in the concentration range of ≤ = 1.0 x 10-3 M, and a useful working pH range of 4.0-9.5. The proposed sensor displays excellent discriminating ability toward Ag+ ion with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of Ag+ with EDTA and in direct determination of silver ion in wastewater of silver electroplating
[en] Highlights: • Thiourea-immobilized polystyrene (TA-PS) nanoparticles were synthesized. • TA-PS is highly acid resistant. • The maximum Ag+ sorption capacity of TA-PS was estimated to be 190 ± 5 mg/g. - Abstract: Although a thiourea-immobilized polystyrene sorbent has been reported to exhibit high Ag+ sorption capacity (135 mg/g), it is not stable under the acidic conditions commonly employed for desorption. In this research, we synthesized novel thiourea-immobilized polystyrene (TA-PS) nanoparticles to be highly acid resistant via a two-step procedure from polystyrene nanoparticles: acetylation and the subsequent immobilization of thiourea. We investigated the influences of pH, contact time, and initial concentration of AgNO3 solution on the Ag+ sorption of the polymer nanoparticles and estimated the maximum Ag+ sorption capacity to be 190 ± 5 mg/g at a pH of 6. The sorption performance did not significantly decrease in tap water containing competing ions. The sorption kinetic data were well fitted to the pseudo-second-order kinetic model. Overall, the TA-PS nanoparticles exhibited a high Ag+ sorption capacity and high selectivity against alkaline and alkaline earth-metal ions. In particular, their high acid resistance allows them to be used for long time periods in sorption–desorption processes.
[en] SiC is a promising material for nuclear applications and is a critical component in the construction of tristructural isotropic (TRISO) fuel. A primary issue with TRISO fuel operation is the observed release of 110mAg from intact fuel particles. The release of Ag has prompted research efforts to directly measure the transport mechanism of Ag in bulk SiC. Recent experimental efforts have focused primarily on Ag ion implantation designs. The effect of the thermal exposure system on the ion implantation surface has been investigated. Results indicate the utilization of a mated sample geometry and the establishment of a static thermal exposure environment is critical to maintaining an intact surface for diffusion analysis. The nature of the implantation surface and its potential role in Ag diffusion analysis are discussed
[en] Highlights: • Our sensor offers a simple solution for highly sensitive and selective detection of ellagic acid from realistic samples. • Growth of Au@Ag core-shell nanorods from Au nanorods mediated by ellagic acid is applied to analytical chemistry. • Sensing is based on monitoring of blue-shifts of the LSPR band accompanying formation of Au@Ag core-shell nanorods. • This strategy can also be extended to other systems for antioxidant sensing. - Abstract: Seed-mediated growth has been employed as a simple and powerful means to the shape-controlled synthesis of metal nanocrystals. In this work, we apply the principle of seed-mediated growth in analytical chemistry, and achieve improved sensitivity due to the low energy barrier in the target-induced formation of bimetallic nanoparticles with core-shell structure. As a result, a simple, reliable, highly sensitive and selective method for the detection of ellagic acid (EA), a naturally occurring polyphenolic antioxidant, has been developed. With the aid of EA in alkaline solution, Ag+ ions can be transformed to Ag atoms and deposit on the surfaces of Au nanorods (AuNRs, act as seeds here) to generate Au@Ag core-shell nanorods, accompanied by blue shift of the longitudinal localized surface plasmon resonance (LSPR) band of AuNRs from near-infrared region to shorter wavelengths. Based on the linear relationship between the wavelength change of longitudinal LSPR band and the concentration of EA, our method achieves a detectable range of 0.2–20 μM and a limit of detection as low as 40 nM toward EA. This approach is highlighted by its high sensitivity for EA assay, which benefits from the viewpoint of thermodynamics in the nucleation/growth mode of metal nanoparticles. Moreover, this method shows high selectivity for EA detection when potential species coexist, and thus has been successfully applied in the detection of EA in skin-whitening cosmetics. The proposed strategy of seed-mediated growth herein can also be extended to other systems for sensing.
[en] The aim of this investigation is to determinate the effects of parameters and additives on the kinetics of dissolution of chalcopyrite on moderated conditions by means of dissolutions test with chalcopyrite concentrate and pure chalcopyrite in shake flasks and instrumented stirred reactors. A study of the dissolution of chalcopyrite in chloride solutions has demonstrated that the rate of dissolution of chalcopyrite is strongly dependent on the potential of the solution within a range of 540 to 630 mV (versus SHE). Leaching at pH around 2.5 results in increased rates of copper dissolution suggesting the possibility to keep the solution potential within the range. Both pyrite and silver ions enhance the dissolution of chalcopyrite and this effect increases when both species are present. The MnO2 has a negative effect on the dissolution increasing the solution potential to values where the rate decreases considerably. (Author)
[en] A simple method of synthesizing silver nanoparticles (AgNps) using rhizome extract of galangal, Alpinia galangal was presented. Antioxidant contains in galangal served as greener and stable reducing agents in this one-pot synthesis. The antioxidant from galangal was extracted in water at ambient environment and quantitative analysis of antioxidant content was carried out using Total Phenolic Content (TPC) assay. Fourier-Transform Infrared (FTIR) spectroscopy analysis confirmed the presence of v(O-H), v(C=C) and v(C-O) peaks that contributed from polyphenol groups stretching vibrations. The formation of AgNps was tracked by ultraviolet-visible spectrophotometer through the presence of absorption peak at 430 nm, while the morphology and crystallinity of AgNps were determined by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses. The results from this study prove that antioxidants found in galangal rhizome extract act as effective reducing agent in the synthesis of AgNps. (author)
[en] The silver cementation on metallic copper was investigated in the presence or absence of oxygen. The influence of sulphuric acid and copper sulphate concentration on the silver cement morphology was studied in details, and results were linked with the previously determined kinetics data of the process. The morpgology of silver depopsit was found to be independent of the prosence of oxygen in the system in as well as the sulphuric acide concentration. Contrary, the concentration of copper sulphate strongly influenced the morphology of silver deposite. Two-stage mechanism of cementation was proposed. (authors).
[en] Infection associated with titanium implants remains the most common serious complication in hard tissue replacement surgery. Since such postoperative infections are usually difficult to cure, it is critical to find optimal strategies for preventing infections. In this study, TiO_2 coating incorporating silver (Ag) nanoparticles were fabricated on pure titanium by micro arc oxidation and ion implantation. The antibacterial activity was evaluated by exposing the specimens to Staphylococcus aureus and comparing the reaction of the pathogens to Ti-MAO-Ag with Ti-MAO controls. Ti-MAO-Ag clearly inhibited bacterial colonization more than the control specimen. The coating’s antibacterial ability was enhanced by increasing the dose of silver ion implantation, and Ti-MAO-Ag 20.0 had the best antibacterial ability. In addition, cytocompatibility was assessed by culturing cell colonies on the specimens. The cells grew well on both specimens. These findings indicate that surface modification by means of this process combining MAO and silver ion implantation is useful in providing antibacterial activity and exhibits cytocompatibility with titanium implants