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1.
Nanostructured Ag films composed of nanoparticles and nanorods can be formed by the ultrasonication of ethanol solutions containing Ag2O particles. The present work examined the formation process of these films from ethanol solutions by two different agitation methods, including ultrasonication and mechanical stirring. The mass-transfer process from Ag2O particles to ethanol solvent is accelerated by the mechanical effects of ultrasound. Ag+ ions and intermediately reduced Ag clusters were released into the ethanol. These Ag+ ions and Ag clusters provide absorption bands at 210, 275 and 300 nm in UV-vis spectra. These bands were assigned to the absorption of Ag+, Ag 4 2+ and Agn (n?≈?3). The Agn clusters that readily grow to become Ag nanoparticles were formed due to the surface reaction of Ag2O particles with ethanol under ultrasonication. The reactions of Ag+ ions in ethanol to form Ag nanomaterials (through the formation of Ag 4 2+ clusters) were also accelerated by ultrasonication.  相似文献   

2.
The formation of nanoparticles of metallic silver in the reduction of Ag+ ions catalyzed by colloidal Ag2S was investigated. It was established that the position of the surface plasmon resonance bands of the Ag nanoparticles is affected by the concentration of the catalyst, its particle size and the amount of particles with the same size, the stabilization conditions, the concentration of Ag+ ions, and the temperature at which the process is conducted. An explanation for the spectral changes that occur is proposed.  相似文献   

3.

Synthesis of stable mixed nanoparticles (SMNs) by chemical co-reduction of copper and silver complexonates with sodium borohydride in an open system with the access of air oxygen was studied for the first time the. Variation of the Cu2+ to Ag+ molar ratio within 1: (0.05–0.5) enabled targeted formation of differently structured nanoparticles (core-shell type), CucoreAgshell and AgcoreCushell. It was found that, by choosing appropriate synthesis conditions, it is possible to produce oxidation-resistant copper particles protected by a shell of a precious metal or to involve the copper complex of nitrilotrimethylenephosphonic acid in silver reduction. The resulting SMNs may become widely used for obtaining various functional materials.

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4.
Interactions between colloidal copper and silver ions lead to the formation of silver nanoparticles. The reaction proceeds through the intermediate stage of the formation of a copper-silver contact pair. The formation of bimetallic AgcoreCushell nanoparticles is observed in the presence of the “seeding” silver nanoparticles and upon the simultaneous radiochemical reduction of Ag+ and Cu2+ ions.  相似文献   

5.
Platinum colloids in an aqueous solution catalyze the reduction of silver ions by hydrogen to form Pt-Ag core-shell bimetallic nanoparticles. In the presence of the silver nanoparticles, PtII ions are reduced by hydrogen to form AgcorePtshell nanoparticles. The effect of the structure and composition of the nanoparticles on the ability of platinum to catalyze the one-electron reduction of methyl viologen by hydrogen in an aqueous solution was studied. For the PtcoreAgshell nanoparticles, an induction period preceding the start of the reaction was found. The thicker the silver shell on platinum, the longer the lag time of the reaction, which is probably due to a decrease in the rate of hydrogen transfer to the platinum core. For the AgcorePtshell nanoparticles, the size effect was revealed: at the shell thickness less than 1 nm (~4 atomic layers of platinum), platinum loses the ability to catalyze the reaction. The mechanism of the catalytic process is discussed.  相似文献   

6.
The in situ 18F-γ-ray irradiation of SiO2 nanoparticles in an aqueous solution containing Ag+ led to the reduction of Ag+ to Ag0 aggregates or Ag0 nanoparticles in a small volume (0.1 ml) under air. 18F was used in the form of 18F-fluorodeoxyglucose, produced by a cyclotron at our University hospital. The in situ average absorbed dose at the distance of 1 µm in the solution volume (0.1 ml) was calculated to be 12.2 kGy equivalent to a point source of 20 MBq. The SiO2 nanoparticles had two effects; they enhanced the reduction of Ag+ to Ag0 aggregates and they acted as reaction sites to prevent aggregation. When Ag+ adsorbed on the surface of the SiO2 nanoparticles, Ag nanoparticles were formed by 18F γ-rays. The absorption spectra of Ag nanoparticles and Ag0 aggregates were markedly different.  相似文献   

7.
以Cu2O和Ag2O纳米粒子为前驱体,利用Kirkendall效应,在室温条件下制备出Cu7S4和Ag2S的球形空心纳米粒子。用X-射线衍射(XRD)、透射电镜(TEM)、扫描电镜(SEM)等测试手段对产物进行了表征。结果表明,粒子的空心化程度取决于反应物的物质的量之比;空心粒子的形貌与前驱体粒子的形貌很相似。研究了这种反应的机理,并对这两种氧化物发生这类反应的难易程度作了理论探讨。  相似文献   

8.
Within the problem of the synthesis of silver nanoclusters and nanoparticles in polyether media, systems containing silver nitrate AgNO3 and low-molecular-weight polyethers, poly(ethylene glycol) PEG-400 or oxyethylated glycerol OEG-5, were studied by fast atom bombardment (FAB) mass spectrometry. The formation of stable clusters of polyether oligomers (M m ) with silver cations M m · Ag+ was shown, in agreement with the previous data of laser desorption/ionization. Quantum-chemical DFT calculations have shown that the M m · Ag+ clusters are stabilized by wrapping of the polyether chain around the silver cation with the cation coordinating ether oxygen atoms. Silver nanoclusters were not found in the FAB mass spectra of liquid systems, but Ag n + clusters were detected for silver nanoparticles separated from the reaction medium. No products of chemical transformations of PEG-400 or OEG-5 were observed by FAB. A plausible mechanism of the reduction of silver cations involving nitrate anions is discussed.  相似文献   

9.
Regularities of the formation of silver nanoparticles according to the reduction reaction of silver oligostyrylmonocarboxylate with ED-20 resin in the absence of hardening agent were studied at 60–75°C by UV/Vis spectroscopy and IR spectroscopy, transmission electron microscopy, and viscosimetry. Spherical silver nanoparticles with oligostyrylcarboxylate ligands characterized by diameter equal to 1.8 ± 0.2 nm and tendency toward ordered disposition in space were obtained. The process of formation of nanoparticles includes consecutive formation of diphilic complexes of silver carboxylate with epoxy resin, Ag+ → Ag0 reduction, and formation of (Ag0) n nuclei at the ends of the diexpoxy component and/or along the oligomer chain. The activation energy values of formation of nanoparticles during the “inductive period” and at the stage of accumulation as well as the activation energy of viscous flow of ED-20 were measured. The threshold temperature of formation of narrow-size silver nanoparticles in epoxy oligomer ED-20 equals 75°C.  相似文献   

10.
Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006  相似文献   

11.
In this work, MOF‐5 composited with Ag2O nanoparticles was prepared and characterized via X‐ray diffraction, field emission‐scanning electron microscopy, energy‐dispersive spectroscopy and FT‐IR analysis. This new material was subsequently employed for removing basic yellow dye [Auramine O (AO)] from aqueous solution under ultrasound irradiation. Several experiments were designed by central composite design in which operational parameters such as such as pH, MOF‐5‐Ag2O mass and initial concentration of AO involved in the process were optimized. The significance of individual parameters and their possible interactions were investigated using analysis of variance (anova ). The optimum values of 6, 0.025 g and 6 mg l?1 were obtained for the pH, MOF‐5‐Ag2O‐NPs mass and the initial concentrations of AO, respectively, with desirability of 1.0. At such conditions, the efficiency for the removal of AO was found to be 89.45%. Various isotherm models for fitting the experimental equilibrium data were studied, and it was found that the Langmuir model has the highest efficiency for correlation of experimental equilibrium data, so that the monolayer adsorption capacity of MOF‐5‐Ag2O for successful removal of AO was 260.70 mg g?1 at optimal conditions.  相似文献   

12.
G5.0‐OH PAMAM dendrimers were used to prepare fluorescent silver clusters with weaker ultraviolet irradiation reduction method, in which the molar ratio of Ag+ to PAMAM dendrimers was the key factor to determine the geometry and properties of silver nanoparticles. The results showed that because of G5.0‐OH PAMAM dendrimers as strong encapsulatores, when the molar ratios of Ag+ to PAMAM dendrimers was smaller than 5, the obtained Agn clusters (n<5) had line structures and "molecular‐like" properties, which were highly fluorescent and quite stable in aqueous solution. Whereas when the molar ratios were between 5 and 8, the obtained Agn clusters were 2D structures and their fluorescence was weaker. When the molar ratio was larger than 8, the structure of silver nanoparticles was 3D and no fluorescence was observed from the obtained silver nanoparticles.  相似文献   

13.
A novel method was proposed to prepare a series of functionalized Ag2S nanoparticles capped with various aminopolycarboxylic acids. The as-prepared Ag2S nanoparticles were characterized by UV-vis, FTIR, resonance light scattering spectra (RLS) and transmission electron microscopy (TEM). Based on the RLS intensities enhanced by BSA-induced Ag2S nanoparticles aggregation, a sensitive RLS method for the detection BSA at nanogram levels was established. The detection limits for BSA are between 8.6 and 112.6 ng mL−1, depending on the different capping agents. The effects of various capping agents on the detection limits of BSA have been investigated. The detection limit is found to be dependent on the stability constant (log KMY) of the silver-aminopolycarboxyl complexes.  相似文献   

14.
Atomically precise polyoxometalate–Ag2S core–shell nanoparticles were generated in a top‐down approach under solvothermal conditions and structurally confirmed by X‐ray single‐crystal diffraction as an interesting core–shell structure comprising an in situ generated Mo6O228? polyoxometalate core and a mango‐like Ag58S38 shell. This result demonstrates the possibility to integrate polyoxometalate and Ag2S nanoparticles into a core–shell heteronanostructure with precisely controlled atomical compositions of both core and shell.  相似文献   

15.
Formation of silver nanoparticles in the course of chemical reduction of AgNO3 with arabinogalactan in aqueous alkaline solution was studied by electronic absorption spectroscopy and X-ray diffraction analysis. The pH of the solution was found to be the major factor affecting the degree of reduction of Ag+ ions. The probable reaction mechanism was discussed. Composites containing up to 58% Ag, with the metal particle size of 7–16 nm, were prepared. The nanoparticle size can be controlled by varying the reactant ratio AgNO3: arabinogalactan. Chemical modification of arabinogalactan was confirmed by IR and 13C NMR spectroscopy and by TLC.  相似文献   

16.
Silver sulfide nanoparticles dispersed in sol-gel derived hydroxypropyl cellulose (HPC)-silica films have been successfully synthesized using H2S gas diffusion method. This is the first attempt to produce silver sulfide nanoparticles using this technique. Ag2S nanoparticles are generated through reaction of H2S gas with AgNO3 precursor dissolved in the HPC-silica matrix. Transmission electron microscope (TEM) and atomic force microscope (AFM) analysis reveal nanoparticles size distribution from 2.5 nm to 56 nm for H2S gas exposed sample. The surface chemistry of Ag2S nanoparticles and sol-gel derived HPC-silica matrix is confirmed by X-ray photoelectron spectroscopy (XPS). The negative shifts in the core-level XPS Ag (3d) binding energy of Ag2S nanoparticles are attributed to Ag : S surface atomic ratio exhibited by these nanoparticles with varying processing conditions. Following processing and characterization, suitability of the present method to produce silver sulfide ion-selective electrode is demonstrated by depositing Ag2S nanoparticles on a graphite rod. The high reponse function of the electrode is due to the presence of nanoparticles.  相似文献   

17.
The synthesis of tetranuclear gold complexes, a structurally unprecedented octanuclear complex with a planar [AuI8] core, and pentanuclear [AuI4MI] (M=Cu, Ag) complexes is presented. The linear [AuI4] complex undergoes C?H functionalization of carbonyl compounds under mild reaction conditions. In addition, [AuI4AgI] catalyzes the carbonylation of primary amines to form ureas under homogeneous conditions with efficiencies higher than those achieved by gold nanoparticles.  相似文献   

18.
The formation of Ag3 2+ and Ag4 + clusters upon freezing out of aqueous-alcohol glassy solutions of AgClO4 by γ-irradiation at 77 K was established by ESR and optical spectroscopies. The Ag3 2+ cluster is formed by subsequent addition of Ag+ ions to a silver atom, and the Ag4 + cluster is most probably formed by the reduction of the Ag4 2+ cluster by alcohol radicals. The energies of optical transitions and energy gaps far the Ag4 m+ cluster (m = 0 to 3) were calculated. The absorption bands of the clusters shift to the UV region as the charge increases, which agrees with the experimental results.  相似文献   

19.
Alloy nanoparticles represent one of the most important metal materials, finding increasing applications in diverse fields of catalysis, biomedicine, and nano-optics. However, the structural evolution of bimetallic nanoparticles in their full composition spectrum has been rarely explored at the molecular and atomic levels, imparting inherent difficulties to establish a reliable structure–property relationship in practical applications. Here, through an inter-particle reaction between [Au44(SR)26]2− and [Ag44(SR)30]4− nanoparticles or nanoclusters (NCs), which possess the same number of metal atoms, but different atomic packing structures, we reveal the composition-dependent structural evolution of alloy NCs in the alloying process at the molecular and atomic levels. In particular, an inter-cluster reaction can produce three sets of AuxAg44−x NCs in a wide composition range, and the structure of AuxAg44−x NCs evolves from Ag-rich [AuxAg44−x(SR)30]4− (x = 1–12), to evenly mixed [AuxAg44−x(SR)27]3− (x = 19–24), and finally to Au-rich [AuxAg44−x(SR)26]2− (x = 40–43) NCs, with the increase of the Au/Ag atomic ratio in the NC composition. In addition, leveraging on real-time electrospray ionization mass spectrometry (ESI-MS), we reveal the different inter-cluster reaction mechanisms for the alloying process in the sub-3-nm regime, including partial decomposition–reconstruction and metal exchange reactions. The molecular-level inter-cluster reaction demonstrated in this study provides a fine chemistry to customize the composition and structure of bimetallic NCs in their full alloy composition spectrum, which will greatly increase the acceptance of bimetallic NCs in both basic and applied research.

An inter-particle reaction between atomically precise [Au44(SR)26]2− (SR = thiolate) and [Ag44(SR)30]4− nanoparticles reveals the composition-dependent structural evolution of alloy AuxAg44−x nanoparticles at the atomic level.  相似文献   

20.
We presented a new strategy for ultrasensitive detection of DNA sequences based on the novel detection probe which was labeled with Ag+ using metallothionein (MT) as a bridge. The assay relied on a sandwich-type DNA hybridization in which the DNA targets were first hybridized to the captured oligonucleotide probes immobilized on Fe3O4@Au composite magnetic nanoparticles (MNPs), and then the Ag+-modified detection probes were used to monitor the presence of the specific DNA targets. After being anchored on the hybrids, Ag+ was released down through acidic treatment and sensitively determined by a coupling flow injection–chemiluminescent reaction system (Ag+–Mn2+–K2S2O8–H3PO4–luminol) (FI–CL). The experiment results showed that the CL intensities increased linearly with the concentrations of DNA targets in the range from 10 to 500 pmol L−1 with a detection limit of 3.3 pmol L−1. The high sensitivity in this work may be ascribed to the high molar ratio of Ag+–MT, the sensitive determination of Ag+ by the coupling FI–CL reaction system and the perfect magnetic separation based on Fe3O4@Au composite MNPs. Moreover, the proposed strategy exhibited excellent selectivity against the mismatched DNA sequences and could be applied to real samples analysis.  相似文献   

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