Large Amount Of Ag Research Articles

Tetrad metal ion mediated molecular switch aptamer sensor for fluorescence assay of plasma IP-10 in clinical tuberculosis

Interferon-γ-inducible protein 10 (IP-10) has demonstrated enormous potential as a novel biomarker for tuberculosis (TB), particularly in the monitoring of patient progression for active or latent tuberculosis infection (LTBI). Herein, we established a tetrad metal ion-mediated molecular switch aptamer sensor for the convenient detection of IP-10 in plasma and the diagnosis of TB. The simple sensor relied on the partially complementary IP-10 aptamer and four DNA hairpin strands rich in cytosine (C), which can form a relatively stable tetrad C-Ag+-C structure when combined with Ag+ without additional modification. Based on the specific recognition of IP-10 and aptamer, a large amount of Ag+ could be released in a short time. Combining with cadmium telluride quantum dots (CdTe QDs) as the signal reporter, we achieved superior analytical performance, with the limits of detection (LOD) reaching 3 fg/mL for IP-10 analysis in 1 h. Clinical practicality was confirmed by evaluating 38 clinical samples (19 TB-positive patients, 14 non-TB patients, and 5 latent TB infection patients). The results showed that the detected IP-10 levels were significantly different between the non-TB and TB/LTBI groups, and the results aligned with clinical computed tomography (CT) results, indicating that the method could represent a reliable diagnostic technique for TB.

A novel split-type photoelectrochemical biosensor based on liposome-induced in situ formation of Bi2S3@BiOI/Ag2S heterojunction for the sensitive detection of CEA

A novel split-type photoelectrochemical (PEC) biosensor was constructed for the sensitive detection of carcinoembryonic antigen (CEA) based on the Ag+-liposome (ALL) signal amplification strategy and Bi2S3@BiOI heterojunction as the substrate material. The split-type sensing mode effectively avoids the complex fixation of biomolecules on the electrode surface and preserves the activity of biomolecules. The sandwich complex was formed between CEA and aptamer-anchored streptavidin-functionalized magnetic beads (SMB-Apt) and ALL-labeled aptamer (ALL-Apt). After the methanol was added, a large amount of Ag+ was released from the liposome. The released Ag+ was transferred to the Bi2S3@BiOI modified electrode surface for incubation and then soaked in Na2S solution to form a narrow band gap photosensitive material Ag2S on the electrode surface. Bi2S3@BiOI/Ag2S ternary heterojunction in situ was formed due to the band gap matching relationship between Ag2S and the Bi2S3@BiOI heterojunction, which effectively expanded the light absorption range and enhanced the photocurrent signal. Under the optimal experimental conditions, the constructed PEC sensing platform exhibited good analytical performance for CEA with a linear range of 0.005 ∼ 50 ng mL−1 and a detection limit of 1.21 pg mL−1. Additionally, the PEC sensor had good selectivity, reproducibility, and stability, which provided a new research idea for the detection of clinical tumor biomarkers.

“Reduction-aggregation” strategy to construct a low-cost and high-efficiency Ag/Al2O3 catalyst for NH3-SCO

Ammonia (NH3) is the main alkaline gas in the atmosphere and neutralizes acidic gases to form haze. Ag-based catalysts are widely used in the field of ammonia selective catalytic oxidation (NH3-SCO) due to their low cost and high efficiency. However, Ag-based catalysts with high activity at low temperatures are usually loaded with large amounts of Ag. To further reduce the cost of Ag-based catalysts, we used a “reduction-aggregation” strategy to aggregate isolated Ag atoms that were highly dispersed into Ag nanoparticles (AgNPs) so that more active centers could be exposed under low Ag loading conditions. Significant AgNPs size effects in the NH3-SCO reaction were found, including the effect of AgNPs size on catalyst activity and stability. Finally, novel Ag/Al2O3 catalysts with high efficiency and stability were developed at a low Ag loading of 1 wt % and achieved better NH3-SCO performance than 10% Ag/Al2O3, which significantly reduced the catalyst cost.

Ag2S quantum dots loaded dendritic mesoporous silica nanospheres as signal amplification labels for ultrasensitive electrochemical immuno-biosensor for Staphylococcus aureus

An electrochemical immuno-biosensor based on Ag 2 S/DMSNs labels was established to detect S. aureus . • An electrochemical immuno-biosensor based on Ag 2 S/DMSNs labels was established to detect S. aureus . • Using DMSNs for Ag 2 S QDs enrichment and signal amplification to improve the detection sensitivity. • A wide linear detection range from 10 to 10 8 CFU mL −1 , with a detection limit of 2 CFU mL −1 . • The immuno-biosensor showed excellent selectivity and stability. • The immuno-biosensor was successfully applied to detect actual samples. Developing novel signal amplification labels in electrochemical immuno-biosensors for ultrasensitive, fast and selective detection of foodborne pathogen is urgent and significant for people's health and life safety. Herein, dendritic mesoporous silica nanospheres (DMSNs) loaded with silver sulfide quantum dots (Ag 2 S QDs) were fabricated and employed as signal amplification labels for highly sensitive electrochemical detection of Staphylococcus aureus ( S. aureus ). DMSNs were treated with 3-aminopropyltrioxysilane to introduce amino group on surfaces to facilitate the immobilization of Ag 2 S QDs. Benefiting from the highly accessible surface areas and large pore channels characteristics given by the unique radial flower-like structure of DMSNs, large amount of Ag 2 S QDs were loaded into the surfaces and pores of the DMSNs to form Ag 2 S/DMSNs. To specifically recognize S. aureus cells, Ag 2 S/DMSNs were modified by anti- S. aureus antibody (Ab) to form Ab-Ag 2 S/DMSNs. When the sandwich-type electrochemical immuno-biosensor operated, Ag(Ⅰ) ions were released from the Ag 2 S/DMSNs label by HNO 3 leaching, and the detection of S. aureus was realized by the differential pulse voltammetry. The electrochemical signal of the prepared immuno-biosensor was substantially magnified when compared to the immuno-biosensor employing Ag 2 S QDs as signal label, since much more Ag 2 S QDs were labeled to each bacterial cell due to the high loading of Ag 2 S QDs on the DMSNs. As a consequence, the developed immuno-biosensor was capable of detecting S. aureus cells down to a limit of 2 colony forming units per mL (CFU mL −1 ) and exhibited a wide linear detection range from 10 CFU mL −1 to 10 8 CFU mL −1 . In addition, the immuno-biosensor showed excellent selectivity and stability for the detection of S. aureus , and was successfully applied to detected S. aureus in milk samples.

Structural Origin of the Optical Properties of Ag-Doped Fluorophosphate and Sulfophosphate Glasses.

Given the ubiquity of glass formulations that are functionalized with silver compounds, the electronic interaction between isolated silver cations and the glass network deserves more attention. Here, we report the structural origin of the optical properties that result from silver doping in fluorophosphate (PF) and sulfophosphate (PS) glasses. To achieve this, solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) are combined with optical spectroscopic analysis and physical property measurements. Comparing the 31P NMR, 27Al 1d NMR, and 27Al multi-quantum magic-angle spinning NMR of doped glasses and glasses with large amounts of Ag+ added, we deduce silver's bonding preference in these mixed-anion aluminophosphate glasses. We show that such understanding provides an explanation for the large Stokes shift observed for Ag+ in PF and PS glasses, which is related to absorption by the ionic Ag+···-O-P species and transfer of the excitation energy within more covalently bonded Ag2O-like clusters. This is corroborated by DFT calculations, which show that the Ag+···-O-P and Ag+···-O-S bonds in corresponding crystals are mostly ionic. The introduction of more silver ions into the crystal structure results in more covalent bonding between Ag+ and the phosphate matrix.

Analysis of In Situ Synthesis and Cross-Sectional Evolution of Wear Scars of TiAl-Ag Composites

The need for reducing the energy consumption and volume of materials used in the aerospace industry has been driving the further optimization of the behavior of TiAl alloy under friction and wear. Therefore, investigating the micro-/nanostructures of the wear scar cross sections when TiAl-Ag composites slide against an immobile Si3N4 ball should help to analyze the friction and wear behaviors. Plastic deformation was observed to occur in the cross sections of the analyzed wear scar during the initial −25 min of the experiments; consequently, a work-hardened layer formed, and the friction coefficient and wear rate rapidly decreased. During the 25-60 min interval, the wear debris was refined in succession and formed a lubrication film, and the friction resistance and material loss were reduced. During the 60-120 min interval, a remarkably large amount of Ag was determined to be well distributed across the wear scar. It coincided with excellent deformation; moreover, the friction coefficients and wear rates of the TiAl-10 wt.% Ag composites were low.

Combined Antibacterial Property and Mechanism of Nanosilver Composites and Antibiotics against Bacteria

The abuse of antibiotics has caused increasingly serious problem of bacterial resistance, thus it is urgent to develop new antibacterial drugs to alleviate this problem. The nanosilver composites that was synthesized from single nanosilver can not only overcome the shortcomings of nanosilver, such as the rapid release rate of Ag+ and unstable physicochemical property, but also reduce the bacterial resistance, which are regarded as a new kind of antibacterial agents with broad application prospects. Previous studies have showed that the combination of single nanosilver and some antibiotics could exhibit the synergistic antibacterial effect. However, little information is available on the performance and mechanism of nanosilver composites combined with antibiotics. In this paper, three kinds of nanosilver composites with different structures were synthesized: silica-polydopamine-nanosilver (SiO2-PD-AgNPs), nanosilver@silica (AgNPs@SiO2) and nanosilver@silica-polydopamine-nanosilver (AgNPs@SiO2-PD-AgNPs). Subsequently, the single toxicity of nanosilver composites to Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) was determined. The results showed that the toxicity of AgNPs@SiO2-PD-AgNPs to the two kinds of bacteria were greater than that of the other two nanosilver composites. Therefore, AgNPs@SiO2-PD-AgNPs was selected as the representative to determine its combined antibacterial property with KS (kanamycin sulfate)/OH (oxytetracycline hydrochloride), and it was found that the combination of AgNPs@SiO2-PD-AgNPs and KS could display synergistic effect on E. coli/. The nanosilver released by AgNPs@SiO2-PD-AgNPs could react with KS to form the KS-nanosilver complex, resulting in a large amount of Ag+ released from nanosilver. The increase of Ag+ enhanced the permeability of cell membrane, so the amount of Ag+ and KS entering the bacteria were more than that of the antibacterial agents when acting alone, which resulted in greater antibacterial property and a synergistic effect. This study explores the optimal combination and related mechanism of new nanosilver composite and specific antibiotics based on the combined toxicity experiments, which will provide new insight into the development of new antibacterial materials and give a reference for the related combination application of drugs.

Effects of reduced graphene oxide on humic acid-mediated transformation and environmental risks of silver ions

The reduction of Ag+ mediated by natural organic matters has been demonstrated to be an important process of Ag+ transformation and would influence the risks of Ag+ and Ag-containing materials in aquatic environment. Considering the large production of carbon nanomaterials (CNMs) and their inevitable release into the environment, the effects of CNMs on Ag transformation are of considerable interest. This study demonstrated that the humic acid-mediated reduction of Ag+ to free Ag nanoparticles (AgNPs) in aqueous phase was suppressed by coexisting reduced graphene oxide (rGO). A large amount of Ag+ was reduced on rGO surface, resulting in the generation of AgNPs-rGO composites. rGO at concentrations of 1–2 orders of magnitude lower than those of Ag+ would exhibit significant effects. The X-ray absorption fine structure spectroscopy study showed that Ag+ was first adsorbed on rGO surface cooperatively with humic acid and then rapidly reduced to AgNPs. The hydroxylic-OH on rGO could participate in the AgNPs formation and was oxidized to carbonyl during the reduction of Ag+. Additionally, the formed AgNPs-rGO had a relatively lower environmental risk compared to AgNPs or rGO alone. Overall, these results improve our understanding of the interaction between CNMs and Ag+ in aquatic systems.

Ag x Cu y Ni z Trimetallic Alloy Catalysts for the Electrocatalytic Reduction of Benzyl Bromide in the Presence of Carbon Dioxide.

Different compositions of trimetallic alloy containing silver, copper, and nickel (AgxCuyNiz) were electrodecorated in a protic ionic liquid medium on glassy carbon electrodes in order to investigate the suitability of the materials as catalysts for electrochemical reduction of carbon dioxide (CO2). Surface characteristic morphology obtained by scanning electron microscopy shows cauliflower crystallites for the deposit of Ag, whereas materials of Cu and Ni exhibit cubic grains and fine particles, respectively. Deposits of trimetallic alloy containing Ag, Cu, and Ni exhibit the mixture of the three characteristic features. Further, trimetallic alloy containing a large amount of Ag provides high crystallinity, whereas predominance of Cu as well as Ni results in porous structures, as revealed by X-ray diffraction analysis. Atomic absorption spectroscopy () was used to determine the compositions of different alloy materials. The suitability of nanomaterials as cathodes for electroreduction of benzyl bromide in CO2 containing 0.1 M tetra-n-butylammonium tetrafluoroborate (DMF/TBABF4)/N,N-dimethylformamide medium was explored. The linear sweep voltammogram reveals that Ag46Cu40Ni14 shows higher cathodic peak current and lower cathodic peak potential than those of other deposited nanomaterials as well as alloys, indicating its higher catalytic activity for such an electroreduction process, whereas potentiostatic electrolysis confirms the abovementioned results.

Effects of Ag addition on properties and structure of Ge–Ga–Se–AgI chalcohalide glasses

An increasing amount of Ag metal was introduced in two GeSe2–Ga2Se3–AgI chalcohalide glasses with GeSe2/Ga2Se3 molar ratios of 1:1 and 2:1. Up to 25mol% Ag can be added in this GeSe2–Ga2Se3–AgI glass. The effects of Ag addition on some basic properties such as density, thermal stability, and optical band gap were investigated to have an overall understanding of GeSe2–Ga2Se3–AgI–Ag chalcohalide glasses. The modification of glass networks can be observed by Raman spectra and DSC measurements. Specifically, electrical conductivity was characterized by AC impedance spectra. The activation energy values of conductivity (Eσ) were obtained through Arrhenius linear fitting. The large amount of Ag in the systems led to high conductivity and low Eσ values. In general, several basic properties of the two series of novel glasses with different GeSe2/Ga2Se3 ratios were investigated in parallel and their potential as solid state conductive materials was evaluated.

Gas-phase selective oxidation of alcohols: In situ electrolytic nano-silver/zeolite film/copper grid catalyst

The selective oxidation of a series of alcohols to their corresponding carbonyl products was carried out over a rationally designed in situ electrolytic nano-silver/zeolite film/copper grid (SZF) catalyst, which was prepared by a combination of the seed-film method for the fabrication of an ultrathin zeolite film and the in situ electrolytic process for the formation of highly dispersed silver nanoparticles. At a relatively low reaction temperature (ca. 320 °C), the SZF catalyst with highly dispersed in situ electrolytic silver nanoparticles exhibited much higher activity for the oxidation of mono-alcohols and higher selectivity for ketonic aldehyde in the oxidation of di-alcohols than the conventional bulk electrolytic silver catalyst. On the basis of the combination of diffuse reflectance ultraviolet visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and thermoanalysis, the remarkably high activity and selectivity of the SZF catalyst was attributed to the highly dispersed silver nanoparticles, which were stabilized by the zeolite film against sintering, and, accordingly, a large amount of Ag + ions and Ag n δ + clusters existed in the silver nanoparticles. The improvements of the catalytic performance of the SZF catalyst in a wide application extension will bring new concerns in both theoretical and applied fields.

Preparation and characterization of Ag(Au) bimetallic core–shell nanoparticles with new seed growth method

Ag(Au) bimetallic core–shell nanoparticles were prepared by a new seed growth method. Ascorbic acid was used to reduce the complex of HAuCl 4 and hexadecyltrimethylammoniumbromide (CTAB). This resulted in the forming of colorless Au(I) (AuCl 2 −). It was used as the growth solution to prepare these bimetallic core–shell nanoparticles. These nanoparticles were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed these nanoparticles exhibited core–shell shape and there was large amount of Ag in the shell. These nanoparticles could be produced in a few minutes without violent stirring and the method was easy and convenient compared with others. The effect of amount of AuCl 2 − on the shape of nanoparticles was also studied. Many small gold nanoparticles were formed on the surface of bimetallic core–shell nanoparticles in the presence of excess AuCl 2 −. The mechanisms were also proposed to explain the process of colloidal preparation.

Iron sulphides at the epithermal gold-copper deposit of Palai-Islica (Almería, SE Spain)

AbstractAu-Cu mineralization at Palai-Islica occurs as disseminations in massive silicified volcanic rocks and, more abundantly, in sulphide-bearing quartz veins. The major ore minerals in the deposit are pyrite ± chalcopyrite, sphalerite and galena and there is a great variety of accessory minerals, including Au-Ag alloys and native gold. Pyrite, the most abundant sulphide, is closely associated with gold. Seven different types of pyrite have been distinguished with a variable concentration of different trace elements. Among these, the only one free of trace elements (type IV) is related to Au-Ag alloys. Pyrite associated with these Au-Ag alloys has cubic and pentagonal dodecahedral habits, whereas pyrite with pentagonal dodecahedral habit only is from barren zones. In addition, there is no significant invisible gold in the pyrite, but there is a relatively large amount of Ag in collomorphic pyrite (up to 0.20 wt.%) or type III pyrite (up to 1.47 wt.%). Arsenic is the most abundant trace element in pyrite (up to 6.11 wt.%), present as a metastable solid solution or as a non-stoichiometric element. A variety of marcasite related to the gold levels also has a considerable amount of trace elements (As up to 1.15 wt.%, Sb up to 0.40 wt.%).

多量の銀を含むガラスの光化学反応と構造 金属銀微粒子の光表面析出

多量の銀を含むガラスの光化学反応と構造 金属銀微粒子の光表面析出

Human peripheral blood lymphocytes transplanted into SCID mice constitute an in vivo culture system exhibiting several parameters found in a normal humoral immune response and are a source of immunocytes for the production of human monoclonal antibodies.

Human PBL from vaccinated healthy blood donors, which was transplanted i.p. into mice with severe combined immunodeficiency (SCID), exhibited an Ag-dependent humoral Ir against tetanus toxoid. This Ir was dose dependent and was completely abrogated by immunizing with large amounts of Ag, suggesting a high dose tolerization of the B cells. A dose-dependent selection of specific, high affinity B clonotypes was also suggested, since immunization with low concentrations of tetanus toxoid produced antisera with higher avidity than immunizations using a high dose of Ag. The production of human Ig and the clonal outgrowth of normal human B cells in the SCID mouse was strongly down-regulated by human NK cells. Human immune B lymphocytes were also recovered from immunized SCID mice and transformed with EBV, yielding lymphoblastoid cell lines producing high affinity antitetanus human IgG antibodies. These results suggest that SCID mice, repopulated with human PBL, can constitute a functional model of several parameters of a normal human humoral Ir and can provide a source of immune B cells for the production of human mAb.

The analysis of iron(III) using solvent extraction with phenylacetic and n-decanoic acids

The extraction of Fe(III) from aqueous solutions by phenylacetic acid in chloroform solution provides a simple, rapid, and accurate method for the determination of low amounts of iron. Concentrations less than 1 μg/ml can be easily determined particularly if advantage is taken of the amplification procedure afforded by the solvent extraction technique by using a large aqueous to organic phase ratio. A maximum concentration of iron(III) of about 18 μg/ml in the aqueous phase (aqueous to organic phase ratio of 2.5:1) can be determined; however, above this concentration deviations from Beer's Law occur for the absorbance of the organic phase. The method is very selective, particularly in the presence of copper, provided care is taken to adjust the aqueous pH to a value of 2.8. n-Decanoic acid could also be used in the method in place of phenylacetic acid and would have some advantage in selectivity, particularly in cases where very large amounts of Ag(I) and Pb(II) were present.