Ag Decoration Research Articles

Silver-decorated hierarchical cuprous oxide micro/nanospheres as highly effective surface-enhanced Raman scattering substrates.

A facile and simple route to manufacture active surface-enhanced Raman scattering (SERS) substrate based on Ag-decorated Cu2O micro/nanospheres on Cu foil was systematically investigated. Hierarchical Cu2O micro/nanostructure transfers from CuO nanosheets and Cu(OH)2 nanowires by means of thermally reducing the oxides from Cu2+ to Cu1+ at temperature of 500 °Cunder nitrogen atmosphere. The subsequent decoration of Ag on Cu2O nanostructural substrate was carried out by means of thermal evaporator deposition. Using 4-aminothiophenol (4-ATP) as probing molecules, the SERS experiments showed that the Ag-decorated Cu2O micro/nanospheres exhibit excellent detecting performance, which could be used as effective SERS substrate for ultrasensitive detection. Additionally, these novel hierarchical SERS substrates showed good reproducibility and a linear dependence between analyte concentrations and intensities, revealing the advantage of this method for easily scale-up production.

Preparation and antibacterial property of silver decorated carbon microspheres

Carbon microspheres (CMSs) were prepared by glucose hydrothermal method. The effects of glucose concentration and reaction time on the size and morphology of CMSs were studied. CMSs with surface area of 642.5m2/g and pore size of 0.8nm were exploited to design hybrid material of CMSs with Ag decoration by radio frequency plasma (RF plasma). A series of investigations using X-ray diffraction, UV–vis spectrometry, Fourier transform infrared spectrometry, X-ray photoelectron spectrometry, thermogravimetric analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy was carried out to characterize the Ag decorated CMSs. RF plasma was employed to reduce Ag+ ions to metallic nano-particles with the particle size of 10–20nm and form a clean metal-support (Ag-CMSs) interface. The mechanism for the structure formation of Ag decorated CMSs was discussed. Plasma produced Ag/CMSs showed antibacterial property and proved suitable for potential biological and environmental applications.

Diameter selective behavior of human nasal epithelial cell on Ag-coated TiO2 nanotubes

Titanium oxide (TiO2), a light, strong, corrosion resistant, biocompatible and non-toxic metal, is widely used as dental or orthopedic implants, but is rarely used in nasal applications. There are three potential clinical applications for titanium in nasal surgery, including nasal septal perforation repairment, nasal reconstruction or rhinoplasty, and cerebral spinal fluid (CSF) rhinorrhea repairment. Nasal cavity is a contaminated cavity, thus to develop a nasal implant with antibacterial activity has its importance. We have developed self-organized TiO2 nanotubes with different diameters by utilizing an electrochemical anodization method and further decorated the TiO2 nanotubes with silver (Ag) layer by electron-beam deposition. The human nasal epithelial cells (HNEpCs) was used for evaluating the cytocompatibility of TiO2 nanotubes with or without Ag decoration, including cell adhesion, cell proliferation assay for analyzing cell growth condition, and scanning electronic microscopy (SEM) for observing cell morphology. Furthermore, Pseudomonus aeruginosa was used for assessing the antibacterial activity of titanium implants. Our results showed that 25-nm-diameter Ag-coated TiO2 nanotubes possess both good cytocompatibility with cultured HNEpCs and antibacterial activity against P. aeruginosa, as compared to 100-nm-diameter nanotubes. In conclusion, the small-diameter Ag-decorated TiO2 nanotubes have high biocompatibility and good antibacterial activity, and there is potential of its usage for future clinical applications as novel nasal implants.

Hydrogen-assisted quasi-cleavage fracture in a single crystalline type 316 austenitic stainless steel

Abstract Hydrogen embrittlement properties were examined in a single crystalline type 316 austenitic stainless steel. Tensile tests were conducted along the 〈1 1 1〉 and 〈0 0 1〉 directions under hydrogen charging. Hydrogen-assisted {1 1 1} quasi-cleavage fracture was observed in both tensile orientations. The degradation of fracture stress and elongation, hydrogen uptake, and hydrogen-induced fracture surface were dependent on the tensile orientation. The tensile orientation dependence of the hydrogen embrittlement properties was shown to result from the deformation twinning behavior. In addition, Ag decoration technique clarified that hydrogen localizes on regions where hydrogen-assisted quasi-cleavage fracture appeared.

Fast Process To Decorate Silver Nanoparticles on Carbon Nanomaterials for Preparing High-Performance Flexible Transparent Conductive Films

This work demonstrates a fast process to decorate silver (Ag) nanoparticles onto the functionalized few-walled carbon nanotubes (f-FWCNTs) and graphene nanosheets (f-GNs). The Ag-coated carbon nanomaterials were used as fillers, which mixed with poly(3,4-ethylenedioxythiophene)-poly(4-stryensulfonate) (PEDOT:PSS) for preparing high optoelectronic performances of flexible transparent conductive films (TCFs). The Ag nanoparticles with a particle size of approximate 5 nm were uniformly distributed on the surfaces of the f-FWCNTs (Ag@f-FWCNTs) and the f-GNs (Ag@f-GNs). The Ag ions play the role of electron acceptors during the reduction process, which increases the hole concentrations in PEDOT:PSS, f-FWCNTs, and f-GNs, therefore enhancing the electrical conductivity of the TCFs. Additionally, the Schottky barrier was decreased because of the increase of work functions of the carbon fillers caused by Ag decoration. The X-ray diffraction spectrum of Ag@f-GNs depicts the formations of the face-centered cubic Ag nanoparticles, and the peak of the (002) graphene plane slightly shifted to the lower frequency, indicating that the f-GN interlayer was intercalated with Ag ions or Ag nanoparticles. When the mixture of 2.0 wt % Ag@f-FWCNTs and 8.0 wt % Ag@f-GNs containing PEDOT:PSS dispersant was coated onto a poly(ethylene terephthalate) (PET) substrate, outstanding optoelectronic properties with a sheet resistance of 50.3 Ω/sq and a transmittance of 79.73% at a wavelength of 550 nm were achieved.

銀デコレーション法を用いた鉄鋼中の水素の可視化

The relation between hydrogen distribution and metallographic microstructure was investigated by means of Ag decoration technique for a SUS304 austenitic stainless steel, and martensitic and spheroidized SCM440 steels precharged with hydrogen. Preferential distribution of Ag particles was seen on the slip lines of the deformed and hydrogen-charged SUS304 stainless steel, suggesting that the slip lines act as hydrogen trap sites. The martensitic SCM440 steel showed almost no selective Ag deposition, indicative of apparently homogeneous distribution of hydrogen. This is probably because the distribution of dislocations with relatively high concentration and the fine structure including lath boundaries etc. acting as hydrogen traps is homogeneous. The spheroidized SCM440 steel showed almost no Ag deposition on the coarse cementite particles and the Ag particle distribution on the other areas did not show clear selectivity. This result suggests that the hydrogen does not diffuse through the cementite particles. The smallest Ag particle size observed by means of atomic force microscope was in the order of 10nm. Though the minimum size of the Ag particle does not necessarily indicate the resolution of the hydrogen visualization, Ag decoration technique is useful to observe the hydrogen distribution. [doi:10.2320/matertrans.M2014431]

Decoration of TiO2 Nanotubes with Metal Nanoparticles Using Polyoxometalate as a UV-Switchable Reducing Agent for Enhanced Visible and Solar Light Photocatalysis

We present the employment of the Keggin ion 12-phosphotungstic acid as a UV-switchable reducing agent for the decoration of Au, Ag, Pt, and Cu nanoparticles onto the surface of TiO(2) nanotubes synthesized by electrochemical anodization. The synthesized composites were studied using SEM, GADDS XRD, and EDX, and the photocatalytic activity of the composites was examined by measuring the photodegradation of the organic dye "Congo red" under simulated solar light. Decoration with metal nanoparticles was observed to enhance the activity of the photocatalytic process by upward of 100% with respect to unmodified TiO(2) nanotubes.

Ag-Nanoparticle-Decorated SiO2 Nanospheres Exhibiting Remarkable Plasmon-Mediated Photocatalytic Properties

We demonstrated for the first time that Ag-nanoparticle-decorated SiO2 nanospheres (NSs) may display noticeable photocatalytic activities upon surface plasmon resonance (SPR) excitation. The samples were prepared by reacting SiO2 NSs with AgNO3 in the seed-mediated growth process, from which the Ag particle size and decoration density can be readily controlled. The dependence of the SPR-mediated photocatalytic performance of Ag-decorated SiO2 NSs on the Ag morphology was investigated and presented. The as-prepared Ag-decorated SiO2 NSs showed a significantly red shifted and relatively broad SPR absorption when compared with the individually dispersed Ag nanoparticles. Owing to the considerably broad SPR absorption that spanned from the visible to the near-infrared region, Ag-decorated SiO2 NSs surpassed N-doped P-25 TiO2 powder and individually dispersed Ag nanoparticles in photocatalytic activity, demonstrating their potential as an active photocatalyst in nearly all the current photocatalysis applicatio...

Facile Control of C2H5OH Sensing Characteristics by Decorating Discrete Ag Nanoclusters on SnO2 Nanowire Networks

The effect of Ag decoration on the gas sensing characteristics of SnO(2) nanowire (NW) networks was investigated. The Ag layers with thicknesses of 5-50 nm were uniformly coated on the surface of SnO(2) NWs via e-beam evaporation, which were converted into isolated or continuous configurations of Ag islands by heat treatment at 450 °C for 2 h. The SnO(2) NWs decorated by isolated Ag nano-islands displayed a 3.7-fold enhancement in gas response to 100 ppm C(2)H(5)OH at 450 °C compared to pristine SnO(2) NWs. In contrast, as the Ag decoration layers became continuous, the response to C(2)H(5)OH decreased significantly. The enhancement and deterioration of the C(2)H(5)OH sensing characteristics by the introduction of the Ag decoration layer were strongly governed by the morphological configurations of the Ag catalysts on SnO(2) NWs and their sensitization mechanism.

Surface charge transfer properties of high-performance Ag-decorated ZnO photocatalysts

Silver-decorated ZnO (Ag/ZnO) chain-like nanoparticle aggregates were prepared by a facile nonaqueous sol–gel method. The influence of Ag decoration on the surface photo-induced charge transfer behaviour of ZnO was investigated by means of surface photovoltage spectroscopy, electric field-induced surface photovoltage spectroscopy and transient photovoltage techniques. The photovoltage spectra revealed that an electronic interaction between Ag and ZnO formed. Ag acted as electron acceptors and effectively inhibited the charge recombination in ZnO with UV light illumination, while under the illumination of visible light a redshift was observed due to the appearance of a plasmon-induced band resulting from the formation of Ag nanoparticle clusters. These were responsible for the significant enhancement in the photocatalytic activity of the Ag/ZnO sample. The results also suggested that the high-performance visible light photocatalytic activity could be manipulated by external biases.

Movement of Hydrogen during SCC of SUS310S Stainless Steel

We have found that less noble potential region existed near the crack tip on SUS304 and SUS316L stainless steel and around the crack on SUS310S stainless steel. Ag decoration was done at the same time to study the relation between the less noble potential region and hydrogen distribution. The results showed there is a good correlation between them. MFM and KFM observation at less noble potential region on SUS316L and SUS310S stainless steel revealed that hydrogen-induced martensite existed at less noble potential region. In present work, repeated crack growth tests were done to study the relation between the movement of hydrogen and the crack formation. The results show that small cracks are produced when hydrogen-induced martensite phase is formed ahead of the crack tip and join together with hydrogen-induced martensite phase becomes former austenite phase.

Functionalized Silica Nanoparticles by Nanometallic Ag Decoration for Optical Sensing of Organic Molecule

Sensing technologies based on metallic nanoparticles, known as Ag, Au, and so on, have raised enormous interest for their extraordinary sensing resolution and sensitivity to analytes of chemical or biological importance under optical detection have received wide attention in recent decades. Currently, a discrete nanoparticle in a free-standing form, either being organically or biologically modified on the nanoparticle surface, on a given substrate surface region has been employed for photosensing purpose. However, metallic nanoparticles suffering from physical and chemical instability such as oxidation, interparticle coupling, agglomeration, and so on during the processing stages may render undesirable outcomes, which further results in poorer performance than the theoretical expectation. Here we propose a facile and elegant concept to prepare an Ag-decorated silica nanoparticle (hereinafter termed core−shell SiO2@Ag nanosphere) based on the modified Stöber method. The Ag nanoparticles with an average size controlled at about 1, 3, and 5 nm deposited over the surface of the silica nanocarrier were well separated, making the resulting SiO2@Ag nanospheres. The nanospheres showed physically and optically stable surface plasmon resonance spectra and also demonstrated a relatively high Ag-sized dependent sensitivity to ppb level for the detection of analyte molecule, that is, melamine. Theoretical model fitting has been well managed to correlate the optical behavior of the nanosensors, and the outcomes strongly indicated a promising potential of the Ag-decorated SiO2 core−shell nanospheres for sensory applications.

Interaction between silver nanowires and CO on a stepped platinum surface

We studied the interplay between Ag decoration of a stepped Pt(355) surface and CO adsorption by in situ high-resolution x-ray photoelectron spectroscopy. Varying amounts of Ag deposited at 300 K initially lead to a row-by-row growth starting from the lower Pt step edges. Such decoration of the step sites results in a change in the CO adsorption behavior. An apparent blocking of step sites for low CO coverages is attributed to a change in the electronic structure, resulting in a C 1s binding energy of CO at step sites being equal to that for CO at terrace on-top sites in the presence of Ag. Higher CO coverages induce the formation of embedded Ag clusters within the upper terraces, thus freeing up a part of the original Pt step sites for CO adsorption, as was derived by a comparison to density functional theory calculations in the corresponding surface models.

Mechanism of SCC on SUS310S Stainless Steel

The author have developed a new SCC test method that enables the super Kelvin force microscope (SKFM) and the Kelvin force microscope (KFM) observations. By using this test device, the crack tip deformation and surface po- tential distribution were observed on SUS310S stainless steel by SKFM and KFM. At the same time, the distribution of hydrogen was examined by the Ag decoration method with the EDX image mapping analysis combined. Moreover, the existence of hydrogen-induced martensite was examined by the magnetic force microscope (MFM) observations. The re- sults showed that the less noble potential region existed at whole crack and Ag precipitated at less noble potential region in most cases. The MFM and KFM observation showed hydrogen-induced martensite existed at the less noble potential part. SCC is caused by the formation of hydrogen-induced martensite ahead of the crack tip.

Hydrogen Mapping in Steels by Means of Ag Decoration Technique

not Available.

Mechanism of SCC on SUS310S Stainless Steel

The author have developed a new SCC test method that enables the super Kelvin force microscope (SKFM) and the Kelvin force microscope (KFM) observations. By using this test device, the crack tip deformation and surface po- tential distribution were observed on SUS310S stainless steel by SKFM and KFM. At the same time, the distribution of hydrogen was examined by the Ag decoration method with the EDX image mapping analysis combined. Moreover, the existence of hydrogen-induced martensite was examined by the magnetic force microscope (MFM) observations. The re- sults showed that the less noble potential region existed at whole crack and Ag precipitated at less noble potential region in most cases. The MFM and KFM observation showed hydrogen-induced martensite existed at the less noble potential part. SCC is caused by the formation of hydrogen-induced martensite ahead of the crack tip.

The structure of the cell envelope of Micrococcus radiodurans as revealed by metal shadowing and decoration

The cell envelope of Micrococcus radiodurans has been examined by Ta/W shadowing complemented by Ag decoration. Particular attention was paid to the structure determination of the HPI layer, a hexagonally patterned monolayer of protein, and its association with the outer membranous layer of the bacterium. By combining the information from the several structural aspects found, a model is proposed for the structure of the HPI-layer protein and its orientation in the cell envelope is established.