Silver Modification Research Articles

Synthesis of Ag/ZnO nanorods array with enhanced photocatalytic performance

Silver-modified ZnO nanorods array has been prepared and the effect of silver modification has been studied. ZnO nanorods array were fabricated through a wet chemical route and a photo deposition method was taken to fabricate silver nano particulate on the ZnO nanorods. The structural and optical properties were characterized by field emission scanning electron microscope, high resolution transmission electron microscope, X-ray photoelectron spectroscopy, Raman, UV–vis and photoluminescence (PL) spectra. The UV photocatalytic activity of these materials was studied by analyzing the degradation of methylene blue (MB) in aqueous solution. The photocatalytic performance indicated that Ag deposit acted as not only electron sinks to enhance the separation of photoexcited electrons from holes, but also charge carrier recombination centers, so the optimized amount of Ag deposit was investigated.

Novel modification of elemental silver formed in Ag4[Fe(CN)6]-gelatin-immobilized matrix Implants

Abstract Ag4[Fe(CN)6]→Ag reduction process occurring in Ag4[Fe(CN)6]- gelatin-immobilized matrices, has been studied. In the course of reduction, these matrices are in a contact with water-alkaline solu-tion containing tin(II) dichloride along with an organic or inorganic compound capable of forming a stable soluble complex with Ag(I). It has been found that the substance formed in the gelatin matrix, is almost pure elemental silver, which consists two various phases which are distinguished by their optical and X-ray diffraction parameters.

Enhanced photocatalytic disinfection of microorganisms by transition-metal-ion-modification of nitrogen-doped titanium oxide

In this article, palladium modification and silver modification were used as examples to demonstrate the disinfection effects on microorganisms in aqueous environment of photocatalytic transition-metal-ion-modified nitrogen-doped titanium oxide (TiON/M) materials. Transition metal ion modification was applied to TiON to take advantage of the coupling between transition metal ion addition and TiON semiconductor matrix under visible light illumination. The coupling promotes the separation of electron and hole pairs produced by photon excitation, thus it could reduce the intrinsic charge carrier recombination from anion-doping, which largely limits the photoactivity of TiON under visible light illumination. Large enhancements on the hydroxyl radical production and the photocatalytic disinfection efficiency on microorganisms under visible light illumination were observed for TiON with both palladium and silver modifications. The superior photocatalytic performance under visible light illumination suggests that the transition metal ion modification is an effective approach to reduce the massive charge carrier recombination from anion-doping and to enhance the photocatalytic performance of anion-doped TiO2. The resulting photocatalytic materials have the potential for a wide range of environmental applications.

The impact of silver modification on the catalytic activity of iodine-doped titania for p-chlorophenol degradation under visible-light irradiation

Iodine-doped titania photocatalysts (I-TiO 2) were improved by doping the catalysts with different contents of silver (Ag-I-TiO 2) to investigate the effect of silver modification on the structure and activity of the photocatalysts. The chemical and physical properties of the catalysts were determined by X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), selected area electron diffraction pattern (SAED), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra. The impact of silver modification on the photocatalytic activity was investigated via the photodegradation of p-chlorophenol (PCP) under visible-light irradiation. The significant enhancement of PCP degradation using Ag-I-TiO 2, with an optimum silver content of 3% can be ascribed to the fact that the doped silver trapped photogenerated electrons and promoted the formation of Ti 3+ and, hence, the inhibition of the recombination of electron–hole pairs. The probable pathway of PCP mineralization was mainly a surface charge process, caused by adsorbed OH radicals ( OH ads), valence band holes (h vb +) and electrons (e cb −), which was verified by studying the effects of scavengers and nitrogen purging.

PREPARATION AND SILVER MODIFICATION OF LIFEPO4/C FOR LI-ION BATTERIES

LiFePO 4 /C and LiFePO 4 /C+Ag samples were prepared by sol-gel method. Samples were characterized by XRD, SEM, EIS and electrochemical discharge and charge tests. Silver modification does not affect the olivine structure of LiFePO 4 but enhances its electrochemical performance in terms of discharge capacity and rate capacity. Discharge capacities are improved from 130.8 mAhg-1 of LiFePO 4 /C to 149.8mAhg-1 of LiFePO 4 /C+Ag cathodes. EIS measurements show that Silver modification slightly decreases the charge transfer resistance of LiFePO 4 /C, and lithium ion diffusion coefficient is enhanced from 2.89×10-14 to 8.17×10-13 m2 s-1. 1 , the phosphor- olivine LiFePO 4 has been recognized as a potential positive electrode material for use in lithium ion batteries. Although LiFePO 4 possesses a number of advantages (high capacity, high stability during lithium extraction/insertion, environmental friendliness, etc) 2 , its main drawback is poor electrochemical performance due to its sluggish charge/discharge kinetics. In order to increase the charge capacity and improve the conductivity, many attempts have been performed, using approaches such as decreasing active particle size 3-5 , carbon coating 6-9 , ion doping 10-12 and surface modification 13-15 etc. Surface modifications are of great importance in developing electrode materials 15 . In the present paper we investigate the role of silver modification in improving the performance of LiFePO 4 , Wherein we took silver mirror reaction to coat each particle with a thin silver coating. Particles are prepared via a sol-gel route using Fe(Ш) citrate as chelating agent. The impacts of silver coating on the electrochemical properties of LiFePO 4 -based cathodes are systematically studied. EXPERIMENT LiFePO 4 /C composites were prepared by a sol-gel method with subsequent firing of xerogel in argon(purity≥99.99%) atmosphere. First, Fe(Ш) citrate(Sigma, Technical Grade) was dissolved at 70°C in deionized water. Second, equimolar aqueous solution of LiH 2 PO 4 was prepared from NH 4 H 2 PO 4 (GR, sinopharm) and Li 2 CO 3 (99.84%, self-made). The solutions were mixed together and the obtained transparent sol was dryed at 70°C for at least 20h after grinding with mortar and pestle for 10min, the obtained material was fired in argon atmosphere at 700 °C for 18h the heating rate being 10K/ min. The surface modification was performed by silver mirror reaction 13-14

The state of nickel in the silver modified NiMg/SiO2 vegetable oil hydrogenation catalysts

Two series of silver modified Ni-Mg materials were synthesized by precipitation-deposition on SiO2 support derived from two silica sources: diatomite activated at 800°C (Series a; Mg/Ni = 0.1 and SiO2/Ni = 1.07) and synthetic water glass (Series b; Mg/Ni = 0.1 and SiO2/Ni = 1.15). The modification with silver was made at three molar Ag/Ni ratios, namely 0.0025, 0.025, and 0.1. The effects of the source of the silica support and the silver presence and content on the nickel state in the silver modified reduced-passivated NiMg/SiO2 precursors of the vegetable oil hydrogenation catalyst were established by X-ray diffraction and X-ray photoelectron spectroscopy techniques. The passivation procedure was applied in order to protect the metallic nickel particles from further oxidation. The crystallization of the formed nickel hydrosilicate phases depends on the source of the silica support, more expressed in the diatomite supported samples. It was shown that the silver modification of the NiMg/SiO2 precursors enhances the reduction of the nickel hydrosilicates accompanied by formation of relatively smaller metallic nickel particles, more pronounced in the water glass supported precursors. The increase of the silver content in the water glass deposited samples is responsible for the metallic nickel dispersion increase. The higher content of the Ni0 particles on the surface of the diatomite deposited samples is in accordance with the higher stability of the larger metallic nickel crystallites to oxidation during the passivation step. On contrary, higher dispersed Ni0 particles on the surface of the water glass supported samples are more susceptible to the oxida

Effect of silver modification on structure and catalytic performance of Ni-Mg/diatomite catalysts for edible oil hydrogenation

Silver modified Mg-Ni/diatomite materials with ratios of SiO 2/Ni = 1.07 and Mg/Ni = 0.1, differing in Ag content (Ag/Ni = 0.025 and 0.1) were prepared by the precipitation–deposition method. The effects of silver presence and content on the structure, morphology, texture and H 2-adsorption capacity of the obtained precursors were studied by X-ray diffraction, scanning electron microscopy, Hg-porosimetry and H 2-chemisorption techniques. The catalytic performance of the corresponding catalysts in the soybean oil hydrogenation was investigated. The increase of the silver loading resulted in the development of macroporosity and increase in the total sample porosity. The decrease of both H 2-adsorption capacity and hydrogenation activity are related to the metallic silver covering and blocking effects on the Ni 2+ species, thus hampering the access of hydrogen. The decrease of hydrogenation activity and favorable limiting of cis– trans isomerization on the silver modified catalyst are explained by Horiuti–Polanyi mechanism based on the assumption that hydrogenation and isomerization proceed at the same active metallic nickel sites via half-hydrogenated intermediates. It was shown that the adjustment of the catalyst composition by changing the content of silver modifier offers the possibility to control the total amount of solid fat content, stearic acid and detrimental trans fatty acids in the hydrogenated derivatives. The catalyst with higher silver content is proposed as a promising candidate for selective edible oil hydrogenation catalyst.

A Highly Efficient Ag-ZnO Photocatalyst: Synthesis, Properties, and Mechanism

Highly photocatalytically active silver-modified ZnO has been prepared and the effect of silver modification was studied. The structural and optical properties were characterized by X-ray diffraction, Fourier transform IR, differential scanning calorimetry, BET surface area, Raman, UV−vis, and photoluminescence spectroscopy. The photocatalytic activity of these materials was studied by analyzing the degradation of an organic dye, rhodamine 6G (R6G), and it is found that 3 mol % silver-modified ZnO at 400 °C shows approximately four times higher rate of degradation than that of unmodified ZnO and a three times higher rate than that of commercial TiO2 photocatalyst Degussa P-25. It was also noted that the photocatalytic activity for the modified ZnO sample was five times higher than the unmodified sample using sunlight. The effect of silver in enhancing the photocatalytic activity has been studied by analyzing the emission properties of both ZnO and silver-modified ZnO in the presence (emission increases) a...

Electrospun Polyacrylonitrile-Based Carbon Nanofibers and Their Silver Modifications:Surface Morphologies and Properties

Polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) were prepared via the electrospinning process. Silver (Ag) modifications of these CNFs were carried out using in-situ Ag reaction as well as Ag coating methods. Ag modified CNFs from both methods yielded higher electrical conductivity than the neat CNFs due to the synergetic effect from the Ag nanoparticles. The effects of fiber diameter, fiber aspect ratio and the interconnecting network nature of the non-woven fiber mat on the electrical and thermal decompositional properties of as-prepared fibers were also investigated. The structural characterizations of as-prepared fibers were performed using SEM, Raman spectroscopy, WAXD, and TGA methods.

Antibacterial activity of montmorillonites modified with silver

The antibacterial properties of silver modified montmorillonites from Pellegrini Lake, Argentina were tested in growth inhibition of Escherichia coli bacteria. Montmorillonite was first submitted to different treatments: (a) calcination at 550 °C for 3 h and (b) grinding during 300 s. After that, the samples were loaded with silver by ion exchange. Structural characterization was performed by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), and BET specific surface area measurements. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTM) showed that metallic silver nanoparticles precipitates over the clay surface after silver modification. Nevertheless, the displacement of the (0 0 1) reflection observed by XRD in the calcined sample, and the diminution in Na + content evaluated by energy dispersive X-ray spectroscopy (EDXS), indicate that Ag ions were interchanged in the structure of the clays. Both samples showed good antibacterial activity against E. coli, measured by the disk susceptibility and the minimum inhibitory concentration (MIC) tests. The ground montmorillonite required a lower MIC than the thermally treated, although the last one presented a bigger inhibition zone in the disk method. The results shows that the antibacterial activity is generated by the Ag + present in the clay, as confirmed by X-ray photoelectronic spectroscopy (XPS); however the overall antibacterial properties are affected by the availability of the ionic silver to be in contact with the bacteria.

Reliability and validity study of Silver's test for Hong Kong–Chinese with dementia

There has been great concern regarding the functional and cognitive abilities of elderly people in performing activities of daily living. 'Silver's test' has been widely used to assess the abilities and mental functions of the aging population in Hong Kong. The purpose of this study was to establish the validity and reliability of a Chinese version of Silver's test (CVST) for Hong Kong-Chinese with dementia. A sample of 78 (21 male and 57 female) elderly subjects was recruited through two-stage cluster sampling. They were administered both the CVST and the Chinese Mini-Mental Status Examination (MMSE). Spearman rank-order correlation coefficient (rs) and intra-class correlation coefficient (ICC) showed that the CVST had a very good inter-rater reliability (rs=0.9573, P=0.000; ICC=0.9966) and test-retest reliability (rs=0.9693, P<0.001; ICC=0.9769). The internal consistency of the test was satisfactory (Cronbach's alpha=0.8396). The Mann-Whitney U-test showed that the CVST could discriminate the demented elderly subjects from the non-demented subjects, suggesting the best cut-off score to be 34, yielding a high sensitivity of 96.4% and equally good specificity of 96.7%. There was also a high positive correlation (rs=0.9218, P<0.001) between the total scores of the CVST and the MMSE. Suggestions for the modification of Silver's test were also made. In conclusion, the initial reliability and validity of the CVST has been established for Hong Kong-Chinese with dementia. It appears to be a sensitive and practical cognitive assessment acceptable to this population.

Mechanism of Silver Modification for the Enhanced Photocatalytic Activity of Cr(VI) Reduction on TiO&lt;sub&gt;2&lt;/sub&gt; Photocatalyst

Under the condition that negative effects of proton starvation and photo-generated electron-hole recombination to the Cr6 + photocatalytic reduction process were minimized for the photocatalytic activities of TiO2 and Ag/TiO2 for Cr6 + reduction were comparatively investigated. Combined with the results of EPR, the mechanism of silver modification for the enhanced photocatalytic reduction of Cr6 + on TiO2 was discussed. The result revealed that Cr6 + reduction by the UV-Ag/TiO2 process was more effective than the UV-TiO2 process under the same conditions. Electron transfer from surface Ti3 + to Cr6 + was the key step for Cr6 + reduction. Cr6 + photocatalytic reduction by directly capturing photo-generated electrons is possible, but it occurs mainly indirectly by getting electrons from surface Ti3 +. The higher reduction activity of Ag/TiO2 photocatalyst came mainly from the higher number of surface Ti3 +.

Lung parasites of shrews from Pennsylvania.

We examined lung parasites of three species of soricids, Sorex cinereus (n = 58), Sorex fumeus (n = 23) and Blarina brevicauda (n = 45) collected from Pennsylvania (USA), from 1990 to 1995. Yeast-like cells of Hisfoplasma capsulatum var. capsulatum were found in lung sections stained with Grocott's modification of Gomori's methenamine silver, periodic acid-Schiff, Giemsa, and hematoxylin-eosin in two (3%) S. cinereus, eight (35%) S. fumeus and two (4%) B. brevicauda. The number of spores of H. capsulatum in the lungs was low and no inflammatory reaction was evident. The infection was not disseminated to other organs. This is the first report of H. capsulatum infection in any species of shrews of the genus Sorex and the prevalence in S. fumeus was remarkably high compared to those reported for other wild mammals. A nematode, possibly Angiostrongylus michiganensis, was found in the lungs of one S. fumeus on necropsy and in a stained lung section of one S. cinereus. In both cases the host was also infected with the fungus. Pneumocystis carinii, which is the most common lung parasite in Sorex araneus (the numerically dominant Eurasian species of shrew), was not found in any of the North American species of shrew examined in this study.

Formation of alumina-silver-palladium systems

Diffuse-reflection electron spectroscopy was used to investigate the state of alumina-silver-palladium catalysts as a function of the conditions of synthesis and heat treatment. Mono- and bimetallic particles were found to be present on the surface of a catalyst manufactured by impregnation of the carrier from one impregnating solution. Premodification of the carrier with palladium is accompanied by formation of metal implantation structures in the carrier lattice, while silver modification does not produce such structures. In the Pd/Ag/Al2O3 catalyst, palladium occurs at several oxidation levels.

Zeolite catalyzed ring opening of styrene oxide

Activation of styrene oxide for ring opening reactions has been achieved over acidic forms of zeolites possessing two dimensional intersecting channels of different sizes (HZSM-5 and HZSM-35), as well as over two silver modifications of the latter. Zeolite type Beta has been tested for determining the influence of the channel structure to the reactions' selectivity. Selective formation of 2-phenylethanol on HZSM-35 has been observed. On the silver modifications of zeolite ZSM-35 significant quantities of phenylacetic acid have been determined together with the expected product 2-phenylethanol.

Incremental order quantity for the case of very lumpy demand

There are many procedures that can be used to determine both the Lot-size and delivery date of an order when the user demand rate is not constant. The Wagner—Whitin algorithm provides an optimal solution to the problem, but seems to be difficult to apply in practice. Incremental Order Quantity (IOQ) and Silver and Meal's Technique are the closest to the Wagner—Whitin technique. Later, Silver and Miltenburg has shown that demand patterns with a large fraction of periods with no demand can cause poor performance by the Silver—Meal heuristic. They presented a modification of the basic Silver—Meal heuristic for the situation of frequent periods with zero demand. The Incremental Order Quantity algorithm is even simpler to use than the Silver—Meal algorithm. This article shows that the IOQ can also be used for the situation of frequent periods with zero demand. Without any modification or additional calculation, the IOQ algorithm can give the same result of the Silver—Miltenburg modification.

An XPS study of air corona discharge-induced corrosion products at Cu, Ag and Au ground planes

DC air corona discharge-induced modification of copper (Cu), silver (Ag) and gold (Au) planar ground electrodes is addressed. X-ray photoemission spectroscopy (XPS) is used to monitor the initial phases of corrosion. Negative discharges yield products identifiable by binding energy referencing and semi-quantitative spectral intensity ratios as Au 2O 3, Ag 2CO 3+Ag 2O and CuCO 3 +Cu 2O. Reactivity is in the order Cu > Ag > Au. Ag and Au ground electrodes appear unreactive to positive discharges, whereas copper is converted to Cu(OH) 2. Exposed surfaces exhibit carbonaceous material whose binding energies appear related to the product. A carbidic or graphitic species is found on all negative corona exposed foils. Relatively large concentrations of “adsorbed” oxygen was associated with Au 2O 3, CuCO 3 and Cu(OH) 2 formation. This was attributed to O 2, H 2O and/or OH “adsorption” by comparison with similar components noted in literature XPS studies on electrochemically prepared Au 2O 3 and air-exposed Cu compounds. The reacted silver electrode remained relatively free of excess oxygen.

StainingPneumocystis Cariniiand Fungi in Unfixed Specimens with Ammoniacal Silver Using a Microwave Oven

AbstractA staining method for demonstrating Pneumocystis Carinii and fungi in unfixed specimens is described. The method is similar to Grocott's modification of Gomori's methenamine silver (GMS)method,but periodic acid is substitutedin place of chromic acid and very dilute ammoniacal silver in place of methenamine silver. Dilute ammoniacal silver is much more stableat high temperatures than methenamine silver and, therefore. is suitable for use in a microwave oven.The staining results are consistent and reliable and are indistinguishable from those obtained with Grocott's method. P. cariniiare easily identified because of nuclear-like staining, which may be sporozoites, often seen within the cysts. (The J Histotechnol 11: 19, 1988.)

The Jamarri Silver Technique: A New Staining Modification for Senile Plaques and Neurofibrillary Tangles

A rapid, economical, and simple silver modification, the Jamarri silver technique, has been developed for senile plaques and neurofibrillary tangles using a 10% aqueous solution of silver nitrate. It has applications in both the clinical and research areas of histotechnology, for it may be used on a single slide or a rack of 30 slides.

Pseudo-sulfur granules associated with intrauterine contraceptive devices.

A structure resembling a sulfur granule found in histologic sections of endometrium from patients with intrauterine contraceptive devices is described. It is distinguished from a true sulfur granule on morphologic grounds and is further characterized as a foreign substance, most probably fragments of the synthetic contraceptive device. It is not associated with clinical disease. Microbiologic cultures of removed intrauterine contraceptive devices show no consistent or predominant growth pattern.