Catalytic performance of Ag/Co-Ce composite oxides during soot combustion in O_2 and NO_x:Insights into the effects of silver

The composite oxides xAg/Co_（0.93）Ce_（0.07）（x=Ag/（Co＋Ce） molar ratio）,intended for use as high performance catalytic materials,were successfully prepared via citric acid complexation.The effects of silver on the performance of these substances during soot combustion were subsequently investigated.Under O_2,the 0.3Ag/Co_（0.93）Ce_（0.07） catalyst resulted in the lowest ignition temperature,T_（10）,of197 ℃,while the minimum light-off temperature was obtained from both 0.2Ag/Co_（0.93）Ce_（0.07） and0.3Ag/Co_（0.93）Ce_（0.07） in the NO_x atmosphere.These materials were also characterized by various techniques,including H_2,soot and NO_x temperature programmed reduction,X-ray diffraction,and electron paramagnetic resonance,Raman,X-ray photoelectron,and Fourier transform infrared spectroscopic analyses.The results demonstrated that silver significantly alters the catalytic behavior under both O_2 and NO_x,even though the lattice structure of the mixed oxide is not affected.Surface silver oxides generated under the O_2 atmosphere favor soot combustion by participating in the redox cycles between soot and the silver oxide,whereas the AgNO_3 that forms in a NO_x-rich atmosphere facilitates soot abatement at a lower temperature.The inferior activity of AgNO_3 relative to that of Ag_2O results in the different catalytic performance in the presence of NO_x or O_2.

Preparation of silver tin oxide powders by hydrothermal reduction and crystallization

Silver tin oxide composite powders were synthesized by the hydrothermal method with a silver ammine solution and a Na2SnO3 solution as raw materials. H2C2O4 was used as the co-precipitator of silver ions and tin ions. The co-precipitation conditions were investigated. The results show that the co-precipitate of Ag2C2O4 and Sn（OH）4 is available when the pH value of the solution is 4.27-8.36. Using the obtained precipitate as precursor,the reduction of Ag＋ and the crystallization of tin oxide were carried out simultaneously by the hydrothermal method and silver tin oxide composite powders were obtained. The composite powders were characterized by X-ray diffraction （XRD） analysis,scanning electron microscope （SEM）,and energy spectrum analysis. The results show that the silver tin oxide composite powders are small with a diameter of about 2 μm and with homogeneous distribution of tin.

The feasibility study of the indium oxide supported silver catalyst for selective hydrogenation of CO_(2)to methanol

Silver catalyst has been extensively investigated for photocatalytic and electrochemical CO_(2) reduction.However,its high activity for selective hydrogenation of CO_(2) to methanol has not been confirmed.Here,the feasibility of the indium oxide supported silver catalyst was investigated for CO_(2) hydrogenation to methanol by the density functional theoretical(DFT)study and then by the experimental investigation.The DFT study shows there exists an intense Ag-In_(2)O_(3) interaction,which causes silver to be positively charged.The positively charged Ag species changes the electronic structure of the metal,facilitates the formation of the Ag-In_(2)O_(3) interfacial site for activation and dissociation of carbon dioxide.The promoted CO_(2) dissociation leads to the enhanced methanol synthesis via the CO hydrogenation route as CO_(2)^(*)→CO^(*)→HCO^(*)→H_(2)CO^(*)→H_(3)CO^(*)→H_(3)COH^(*).The Ag/In_(2)O_(3)catalyst was then prepared using the deposition-precipitation method.The experimental study confirms the theoretical prediction.The methanol selectivity of CO_(2) hydrogenation on Ag/In_(2)O_(3) reaches 100.0%at reaction temperature of 200℃.It remains more than 70.0%between 200 and 275℃.At 300℃and 5 MPa,the methanol selectivity still keeps 58.2%with a CO_(2) conversion of 13.6%and a space-time yield(STY)of methanol of 0.453 g_(methanol)g_(cat)^(-1)h^(-1),which is the highest methanol STY ever reported for silver catalyst.The catalyst characterization confirms the intense Ag-In_(2)O_(3)interaction as well,which causes high Ag dispersion,increases and stabilizes the oxygen vacancies and creates the active Ag-In_(2)O_(3)interfacial site for the enhanced CO_(2)hydrogenation to methanol.

Preparation of nanostructure silver powders by mechanical decomposing and mechanochemical reduction of silver oxide

The mechanical decomposing and mechanochemical reductions of silver oxide for preparation of nanocrystalline silver powders by high planetary ball mill was investigated. XRD and HRSEM techniques were used to characterize the structural evolution and morphological changes of products. The results show that the nanostructured silver with an average crystallite size of 14 nm and internal strain of 0.75% is synthesized by mechanical decomposing of Ag2O after 95 h milling. While, the product of mechanochemical reduction of silver oxide using graphite after 22 h milling is nanostructured silver with an average crystallite size of 28 nm and internal strain of 0.44%.

Effect of Nitric Oxide on Alleviating Cadmium Toxicity in Rice (Oryza sativa L.)

Nitric oxide （NO） is a gaseous signaling molecule in plants that plays a key role in mediating a wide range of physiological processes and responses to biotic and abiotic stresses. The present study was conducted to investigate the effects of the exogenous application of sodium nitroprusside （SNP）, an NO donor, on cadmium （Cd）-induced oxidative stress and Cd uptake in rice plants. Rice plants were exposed to Cd stress （0.2 mmol L^-1 CdC12） and different concentrations of SNP （0.05, 0.1, 0.2, and 0.4 mmol L^-1）. A SNP concentration of 0.1 mmol L^-1 （SNP 10） significantly reduced the Cd-induced decrease in shoot and root dry weights and leaf chlorophyll concentrations. The addition of NO also reduced the malondialdehyde （MDA）, hydrogen peroxide （H202） and ascorbic acid （ASA） concentrations. However, the reduction in glutathione （GSH） concentration was inhibited by NO treatment. Moreover, NO prevented the Cd-induced increase in antioxidative enzyme activity. The amount of Cd accumulation in rice plants was also influenced by the addition of NO. The NO supplied by the SNP enhanced the Cd tolerance of the rice by increasing the Cd uptake by the roots and decreasing the Cd accumulation by the shoots. However, the application of potassium ferrocyanide （Cd＋Fe） or sodium nitrate and nitrite （Cd＋N） （without NO release）, did not exhibit the effects of the SNP. Furthermore, the effects of the SNP were reversed by the addition of hemoglobin （an NO scavenger）. Our results suggested that exogenous NO was involved in the resistance of rice to Cd-toxicity.

Lead and Cadmium Adsorption onto Iron Oxides and Manganese Oxides in the Natural Surface Coatings Collected on Natural Substances in the Songhua River of China

Natural surface coatings collected from natural substances （NSCsNS） were employed to study the roles of the main chemical components （iron oxides, manganese oxides, and other components） in controlling the adsorption of lead（Pb） and cadmium（Cd） in aquatic environments. The selective chemical extraction followed by the adsorption of Pb and Cd experiments and statistical analysis, were used to investigate the adsorption property of each component. Hydroxylamine hydrochloride was used to remove manganese oxides selectively, and sodium dithionite was used to extract iron oxides and manganese oxides. The result indicated that iron oxides and manganese oxides played an important role in the adsorption of Pb and Cd on NSCsNS, and the relative contribution was about two-thirds. The contribution of manganese oxides was the greatest, with a lesser role indicated for other components. The adsorption ability of manganese oxides for Pb and Cd was greater than that of iron oxides or other components for Pb and Cd. The Pb adsorption observed in each component was greater than Cd adsorption.

Silver(I) Oxide Mediated Regioselective Monoacylation of 2,4-Dihydroxyls in L-Rhamnopyranosides

A series of acyls （Ac, Bz and Ts） were introduced regioselectively to the 2-hydroxyl in methyl and ally 3-O-benzyl-α-L-rhamnopyranosides mediated by silver（I） oxide in the presence of a catalytic amount of potassium iodide in 56-78% yields.

Thermodynamic approach to synthesis of silver nanocrystalline by mechanical milling silver oxide

Thermodynamic analysis of the possibility of silver nanocrystalline preparation by high energy milling silver oxide was investigated. The molar Gibbs free energy function of mechanically activated samples was calculated from the structural defects such as amorphization, dislocation and surface energy. According to the molar Gibbs free energy function, the equilibrium temperature of mechanical reduction of silver oxide milled for 21 h was estimated at about 304 K. Consequently, at this temperature silver oxide cannot be stable and will transform to silver during the milling.

Polyimide-silver nanocomposite containing phosphine oxide moieties in the main chain:Synthesis and properties

New flame-retardant polyimide-silver nanocomposite containing phosphine oxide moiety in the main chain was synthesized by a convenient ultraviolet irradiation technique.A precursor such as AgNO_3 was used as the source of the silver particles.Polyimide 6 as a source of polymer was synthesized by polycondensation reaction of bis（3-aminophenyl） phenyl phosphine oxide 4 with pyromellitic anhydride 5 in the presence of iso-quinoline as base and in m-cresol solution.The resulting composite film was characterized by FTIR spectroscopy,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,thermogravimetry（TGA） and differential scanning calorimetry（DSC）.The average size of the nanometer Ag particles is about 10 nm.The temperature of 5 and 10%weight loss and also the char yield at 600℃of polyimide-silver nanocomposite 6a were higher than the pure PI 6.

Studies on the Preparation of Bioactive Oligomerstilbene by Oxidative Coupling Reaction(Ⅰ)-Preparation of Shegansu B using Silver Oxide as Oxidant

篢he oxidative coupling reaction of isorhapontigenin using sliver oxide as oxidant afforded a major product, named shegansu B（2）， which was isolated from the roots of Belamcanda chinensis (L．)DC. Both the natural and synthetic Shegansu B have the same potent antagonism activities of leukotriene B4，D4 receptor．

Evolution of the structural and optical properties of silver oxide films with different stoichiometries deposited by direct-current magnetron reactive sputtering

Nitrogen doping of silver oxide （AgxO） film is necessary for its application in transparent conductive film and diodes because intrinsic AgxO film is a p-type semiconductor with poor conductivity. In this work, a series of AgxO films is deposited on glass substrates by direct-current magnetron reactive sputtering at different flow ratios （FRs） of nitrogen to 02. Evolutions of the structure, the refiectivity, and the transmissivity of the film are studied by X-ray diffractometry and sphectrophotometry, respectively. The specular transmissivity and the specular refiectivity of the film decreasing with FR increasing can be attributed to the evolution of the phase structure of the film. The nitrogen does not play the role of an acceptor dopant in the film deposition.

Structural and Optical Properties of Zinc Borotellurite Glass Co-Doped with Lanthanum and Silver Oxide

A series of zinc borotellurite glass co-doped with lanthanum and silver oxide with the chemical formula of [{[(TeO2)0.7(B2O3)0.3]0.7(ZnO)0.3}0.96(La2O3)0.04]1-x(Ag2O)x where the molar frac-tion of silver oxide, x = 0.02, 0.04, 0.06, 0.08 and 0.10 had been successfully prepared via the conventional melt-quenching technique. The structural properties of the glasses were unveiled through X-ray Diffraction (XRD) and Fourier Transform Infra-Red (FTIR) spectroscopy while optical properties of the glasses were investigated with Ultra Violet Visible (UV-Vis) spectropho-toscopy. The short range periodic atomic arrangement in the glass matrix that implies the amorphous nature of the glass was confirmed with the presence of a broad hump in the XRD pattern. On the other hand, the three absorption bands observable in the FTIR spectra had proven the existence of BO4, BO3 as well as TeO4 units in the glass network. The absorbance values retrieved from UV-Vis spectroscopy were utilized to calculate the indirect energy band gap and Urbach energy values of the fabricated glass. By employing the equations proposed by Mott and Davis, the obtained indirect energy band gap have val-ues ranging from 2.16 to 4.16 eV.The decreasing trend in indirect energy band gap and increasing Urbach energy values were related to the increasing num-ber of nonbridging oxygen (NBO) in the glass that is created from the breaking of Te-O-Te or B-O-B bonds after lanthanum as well as silver oxide are incor-porated into the zinc borotellurite glass network.

Thermoelectric characteristics of flexible reduced graphene oxide/silver selenide nanowire composites prepared by a facile vacuum filtration process

The reduced graphene oxide/silver selenide nanowire(rGO/Ag;Se NW)composite powders were fabricated via a wet chemical approach,and then flexible rGO/Ag;Se NW composite film was prepared by a facile vacuum filtration method combined with cold-pressing treatment.A highest power factor of 228.88μW·m;·K;was obtained at 331 K for the cold-pressed rGO/Ag;Se NW composite film with 0.01 wt%r GO.The rGO/Ag;Se NW composite film revealed superior flexibility as the power factor retained 94.62%after bending for 500 times with a bending radius of 4 mm,which might be due to the interwoven network structures of Ag;Se NWs and pliability of r GO as well as nylon membrane.These results demonstrated that the GO/Ag;Se NW composite film has a potential for preparation of flexible thermoelectric devices.

Photoluminescence and X-Ray Diffraction Properties of Europium and Silver Co-Doped Tantalum-Oxide Thin Films Deposited by Co-Sputtering

We fabricated europium and silver co-doped tantalum-oxide (Ta2O5:Eu, Ag) thin films using a simple co-sputtering method for the first time, and we evaluated their photoluminescence (PL) and X-ray diffraction (XRD) properties. We found that the most remarkable PL peak at a wavelength of 615 nm due to Eu3+ can be enhanced by Ag doping, and the strongest PL peak can be obtained from a Ta2O5:Eu, Ag thin film after annealing at 1000℃. Based on XRD measurements, we found that Ag2Ta8O21 crystalline phases produced by Ag doping are very important and Eu3TaO7 phases should be avoided in order to enhance the objective PL peak from our Ta2O5:Eu, Ag thin films.

Malus domestica and Solanum lycopersicum Mixtures for the Synthesis of Graphene Silver and Zinc Oxide Nanocomposites

This study reports on the novel and simple green method involving the use of apple (Malus domestica) and tomato (Solanum lycopersicum) extracts in the synthesis of electroactive layers of silver nanoparticles|graphene oxide (AgNPs|GO) and zinc oxide nanoparticles|graphene oxide (ZnONPs|GO). The surface morphology of the green synthesized nanocomposites was studied using High-Resolution Transmission Electron Microscopy (HRTEM), High-Resolution Scanning Electron Microscopy (HRSEM) while the elemental analysis was studied using Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and X-Ray diffraction (XRD) and their optical properties were further characterised using Ultraviolet Spectroscopy (UV-vis). The electrochemical studies of these nanocomposites were achieved using cyclic voltammetry (CV) where an increase in electron conductivity of the AgNPs|GO and ZnONPs|GO nanocomposite was observed. Comparatively, the silver nanoparticulate-based platforms were observed to have superior electrochemical properties as opposed to the zinc oxide-based platform. The observed electrochemical activities of the synthesized nanocomposites are a good indication of their suitability as electroactive platforms towards the development of electrochemical sensors. Electrochemical sensors are popular in the Electrochemistry field because they may be developed using different methods in order to suit their intended analytes. As such, the synthesis of a variety of electrochemical platforms provides researchers with a vast range of options to select from for the detection of analytes.

Nitric oxide alleviates cadmium-impeded growth by limiting ROS accumulation in pea seedlings

Cadmium(Cd)causes oxidative stress,which leads to the oxidation of various biomolecules by the production of reactive oxygen species(ROS)to facilitate programmed cell death(PCD).The antioxidant defense system fails to detoxify ROS when it is produced in excess.Nitric oxide(NO),a gaseous free radical and a phytohormone,regulates various physiological processes of plants.Therefore,this work was undertaken to study the effects of the application of exogenous sodium nitroprusside(SNP,a NO donor)on growth parameters,oxidative stress,accumulation of secondary metabolites,and activities of antioxidant enzymes under Cd stress.Mild(50μM)and severe(200μM)Cd stress were applied to hydroponically grown pea(Pisum sativum L.)plants with or without 50μM SNP.Severe Cd stress had a substantial impact on the plants.The effectiveness of NO in reducing Cd-induced negative effects on plant height,fresh weight,dry weight,protein content,nitrite content,nitrate reductase(NR)activity,catalase activity,and peroxidase activity were investigated.Seedling development,protein content,nitrite content,nitrate reductase(NR)activity,antioxidant defense systems disruption,overproduction of reactive oxygen species,and oxidative damage were observed.The antioxidant defense system(catalase and peroxidase activities)was activated by NO,which resulted in lower lipid peroxidation and lower hydrogen peroxide(H2O2)levels in Cd-exposed plants.SNP treatment boosted endogenous NO levels and NR activity in Cd-stressed plants while also enhanced proline levels to preserve osmotic equilibrium.The presence of total phenols and flavonoids increased after SNP treatment,indicating that SNP enhanced stress recovery and boosted plant development in Cd-stressed plants.

Reclamation of Mercury from Used Silver Oxide Watch Batteries

This paper deals with the reclamation of mercury from the used silver oxide quartz wristwatch batteries employing leaching-cementation technique. The used batteries are first crushed to liberate the encapsulated active material from the case which is leached in nitric acid to bring all metal contents into solution. After the removal of silver in the solution as silver chloride by precipitation, the mercury which is present as Hg2+ in the solution has been reclaimed through cementation with zinc dust. Various effects like zinc sheet and dust, zinc quantity, pH of the solution, duration and temperature have been carried out to standardise the conditions for maximum mercury reclamation. At a temperature of 45℃ and at 3.9 pH, 92.3% of mercury was recovered using 74 μm size zinc dust with purity greater than 99.78% and the same is characterized by XRF and the results are discussed.

Oxidative Stress and Apoptotic Changes of Rat Cerebral Cortical Neurons Exposed to Cadmium in Vitro

Objective To investigate the cytotoxic mechanism of cadmium（Cd） on cerebral cortical neurons.Methods The primary cultures of rat cerebral cortical neurons were treated with different concentrations of cadmium acetate（0,5,10,and 20 μmol/L）,and then the cell viability,apoptosis,ultrastructure,intracellular [Ca2＋]i and reactive oxygen species（ROS） levels,mitochondrial membrane potential（ΔΨ）,activities of catalase（CAT） and superoxide dismutase（SOD） were measured.Results A progressive loss in cell viability and an increased number of apoptotic cells were observed.In addition,Cd-induced apoptotic morphological changes in cerebral cortical neurons were also demonstrated by Hoechst 33258 staining.Meanwhile,ultrastructural changes were distortion of mitochondrial cristae and an unusual arrangement.Simultaneously,elevation of intracellular [Ca2＋]i and ROS levels,depletion of ΔΨ were revealed in a dose-dependent manner during the exposure.Moreover,CAT and SOD activities in the living cells increased significantly.Conclusion Exposure of cortical neurons to different doses of Cd led to cellular death,mediated by an apoptotic mechanism,and the apoptotic death induced by oxidative stress may be a potential reason.And the disorder of intracellular homeostasis caused by oxidative stress and mitochondrial dysfunction may be a trigger for apoptosis in cortical neurons.

Photosynthesis, Growth and Antioxidant Metabolism in Mustard (Brassica juncea L.) Cultivars Differing in Cadmium Tolerance

Two mustard （Brassica juncea L. Czern and Coss.） cultivars, Pusa Jai Kisan and SS2 differing in cadmium （Cd） tolerance were treated with 0, 25 and 50 umol L-1 Cd to study the physiological basis of difference in Cd tolerance. Cultivar SS2 （Cd sensitive） accumulated greater Cd in leaves than Pusa Jai Kisan （Cd tolerant）. Further, SS2 also exhibited higher contents of thiobarbituric acid reactive substances （TBARS） and H2O2 and electrolyte leakage. However, the activities of antioxidant enzymes, catalase （CAT）, ascorbate peroxidase （APX）, dehydroascorbate reduetase （DHAR）, and glutathione reductase （GR） were higher in Pusa Jai Kisan than those in SS2. Contrarily, the activity of superoxide dismutase （SOD） was higher in SS2 than that in Pusa Jai Kisan and was the greatest at 25 umol L-1 Cd. Treatment of 25 umol L-1 Cd induced the maximum activity of enzymes. However, the activity of GR increased up to 50 umol L-1 Cd in both the cultivars. The non-enzymatic antioxidants ascorbate （AsA） and glutathione （GSH） were higher in Pusa Jai Kisan than that in SS2, whereas dehydroascorbate （DHA） and oxidized glutathione （GSSG） were higher in SS2. Photosynthesis and growth were adversely and maximally decreased by 50 umol L-1 Cd treatment in both the cultivars, but SS2 exhibited greater reductions. The protection of photosynthesis and growth and lesser reduction in Pusa Jai Kisan were associated with its capacity to restrict accumulation of Cd in leaves resulting in lower level of TBARS and H2O2 and electrolyte leakage. Moreover, Pusa Jai Kisan exhibited efficient antioxidant metabolism for removal of Cd-induced reactive oxygen species.

Scavenging of Cd through Fe/Mn oxides within natural surface coatings

The dynamics of Cd scavenging from solutions by Fe/Mn oxides in natural surface coatings （NSCs） was investigated under laboratory conditions. Selective extraction methods were employed to estimate the contributions of Fe/Mn oxides, where hydroxylamine hydrochloride （0.01 mol/L NH2OH-HCl ＋ 0.01 mol/L HNO3）, sodium dithionite （0.4 mol/L Na2S2O4） and nitric acid （10% HNO3） were used as extraction reagents. The Cd scavenging was accomplished with developing periods of the NSCs （totally 21 data sets）. The resulting process dynamics fitted well to the Elovich equation, demonstrating that the amount of Cd scavenged was proportional to the increments of Fe/Mn oxides that were accumulated in the NSCs. The amount of Cd bound to Fe oxides （MCdFe） and Mn oxides （MCdMn） could be quantified by solving two equations based on the properties of two extraction reagents. The amount of Cd scavenged by Fe/Mn oxides could also be estimated using MCdFe and MCdMn divided by the total amounts of Fe and Mn oxides in the NSCs, respectively. The results indicated that the Cd scavenging by Fe/Mn oxides was dominated by Fe oxides, with less roles attributed to Mn oxides. The estimated levels of Cd scavenging through Fe and Mn oxides agreed well with those predicted through additive-adsorption and linear-regression models.