Journal articles on the topic 'Noble metal analyses'
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Stucchi, Marta, Daniela Meroni, György Safran, Alberto Villa, Claudia L. Bianchi, and Laura Prati. "Noble Metal Promoted TiO2 from Silver-Waste Valorisation: Synergism between Ag and Au." Catalysts 12, no. 2 (February 19, 2022): 235. http://dx.doi.org/10.3390/catal12020235.
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Wastewaters from precious metal industries contain high amounts of noble metals, but their efficient recycling is hindered by the wastewater complex composition. Here, we propose an innovative approach for the efficient recovery of noble metals contained in these metal-enriched wastewaters as precursors for the synthesis of noble metal nanoparticles (NPs) and supported metal catalysts. Silver NPs were synthesized from Ag-enriched wastewater and then deposited on TiO2 to prepare photocatalysts. Then, further promotion of the photocatalytic activity of Ag-modified TiO2 was achieved by the addition of as little as 0.5 wt.% of Au. STEM-EDS analyses proved that Au NPs were located on Ag or AgOx nanoparticles. The contact between the two metal-containing NPs results in charge transfer effects, appreciable both in terms of oxidation states determined by XPS and of optical properties. In particular, the plasmon band of Au NPs shows photochromic effects: under UV light irradiation, bimetallic samples exhibit a blue-shift of the plasmon band, which is reversible under dark storage. The activity of the materials was tested towards ethanol photodegradation under UV light. Adding 0.5 wt.% Au NPs resulted in a promoted activity compared to Ag-TiO2, thus showing synergistic effects between Au and Ag. Ethanol was completely converted already after 1 h of UV irradiation, acetaldehyde was formed as the main oxidation product and fully degraded in less than 180 min. Notably, bimetallic samples showed ethylene formation by a parallel dehydration mechanism.
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Yonezawa, Tetsu, Toshihiro Tominaga, and Naoki Toshima. "Protecting Structure Analyses of Organic Molecule-protected Nanoscopic Noble Metal Clusters." Polymers for Advanced Technologies 7, no. 8 (August 1996): 645–51. http://dx.doi.org/10.1002/(sici)1099-1581(199608)7:8<645::aid-pat578>3.0.co;2-w.
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Awad, Hind Dhari, Mohammed Khamas Khalaf, and Alaa Nazar Abd Algaffar. "Noble Metal Thin Film Thickness Optimization for Sharp Surface Plasmon Resonance Reflectance Curve." Materials Science Forum 1039 (July 20, 2021): 442–50. http://dx.doi.org/10.4028/www.scientific.net/msf.1039.442.
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The production of a high-sensitivity surface Plasmon resonance (SPR) sensor depends on a few main factors, such as metal thin film types and thicknesses, light coupling techniques and acceptable EM wave polarization modes. This work is carried out to investigate the impact on the SPR characteristics of noble metal thicknesses, namely gold and silver, for optical sensor applications. To excite surface Plasmon polaritons (SPP), a Kretschmann prism coupling was used. The thicknesses of noble metal thin films were varied between t=30nm and 60nm. The characteristics of SPR peaks such as Q-factor and FWHM were studied in SPR signal analyses. In comparison with silver, Q-factor results showed an outstanding optical property of gold at t= 40 nm due to its high Q-factor values, which confirms its ability to produce excellent SPP quantities. In conclusion, gold noble metal at t= 40nm is capable of producing optimum SPR. In the development of the highly sensitive SPR sensor, this excellent criterion put gold as a spectacular candidate for optical sensor applications.
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Sun, Zhenyu, Lei Fu, Zhimin Liu, Buxing Han, Yunqi Liu, and Jimin Du. "Synthesis of Noble Metal/Carbon Nanotube Composites in Supercritical Methanol." Journal of Nanoscience and Nanotechnology 6, no. 3 (March 1, 2006): 691–97. http://dx.doi.org/10.1166/jnn.2006.128.
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A simple and efficient route has been employed to deposit noble metal nanoparticles (Pt, Ru, Pt–Ru, Rh, Ru–Sn) onto carbon nanotubes (CNTs) in supercritical methanol solution. In this method, the inorganic metallic salts acted as metal precursors, and methanol as solvent as well as reductant for the precursors. The as-prepared nanocomposites were structurally and morphologically characterized by X-ray diffraction spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy, and X-ray photoelectron spectroscopy analyses. It was demonstrated that the CNTs were decorated by crystalline metal nanoparticles with uniform sizes and a narrow particle size distribution. The size and loading content of the nanoparticles on CNTs could be tuned by manipulating reaction parameters. Furthermore, the formation mechanism of the composites was also discussed.
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Yu, Lu, and Na Li. "Noble Metal Nanoparticles-Based Colorimetric Biosensor for Visual Quantification: A Mini Review." Chemosensors 7, no. 4 (October 31, 2019): 53. http://dx.doi.org/10.3390/chemosensors7040053.
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Nobel metal can be used to form a category of nanoparticles, termed noble metal nanoparticles (NMNPs), which are inert (resistant to oxidation/corrosion) and have unique physical and optical properties. NMNPs, particularly gold and silver nanoparticles (AuNPs and AgNPs), are highly accurate and sensitive visual biosensors for the analytical detection of a wide range of inorganic and organic compounds. The interaction between noble metal nanoparticles (NMNPs) and inorganic/organic molecules produces colorimetric shifts that enable the accurate and sensitive detection of toxins, heavy metal ions, nucleic acids, lipids, proteins, antibodies, and other molecules. Hydrogen bonding, electrostatic interactions, and steric effects of inorganic/organic molecules with NMNPs surface can react or displacing capping agents, inducing crosslinking and non-crosslinking, broadening, or shifting local surface plasmon resonance absorption. NMNPs-based biosensors have been widely applied to a series of simple, rapid, and low-cost diagnostic products using colorimetric readout or simple visual assessment. In this mini review, we introduce the concepts and properties of NMNPs with chemical reduction synthesis, tunable optical property, and surface modification technique that benefit the development of NMNPs-based colorimetric biosensors, especially for the visual quantification. The “aggregation strategy” based detection principle of NMNPs colorimetric biosensors with the mechanism of crosslinking and non-crosslinking have been discussed, particularly, the critical coagulation concentration-based salt titration methodology have been exhibited by derived equations to explain non-crosslinking strategy be applied to NMNPs based visual quantification. Among the broad categories of NMNPs based biosensor detection analyses, we typically focused on four types of molecules (melamine, single/double strand DNA, mercury ions, and proteins) with discussion from the standpoint of the interaction between NMNPs surface with molecules, and DNA engineered NMNPs-based biosensor applications. Taken together, NMNPs-based colorimetric biosensors have the potential to serve as a simple yet reliable technique to enable visual quantification.
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Lewandowski, Z., R. Avci, M. Geiser, X. Shi, K. Braughton, and N. Yurt. "Biofouling and corrosion of stainless steels in natural waters." Water Supply 2, no. 4 (September 1, 2002): 65–72. http://dx.doi.org/10.2166/ws.2002.0122.
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The noble shift in corrosion potential to values between +300 and +400 mVSCE and the accompanying increase in cathodic current density and polarization slope at mild cathodic potentials that develop during microbial colonization of passive metals, are collectively known as ennoblement. This phenomenon is of concern as the noble shift in the corrosion potential may lead to pitting corrosion. We have demonstrated, by growing pure cultures of manganese oxidizing bacteria (MOB) Leptothrix discophora SP-6 under well defined conditions, that microbial deposition of manganese oxides causes ennoblement of 316L stainless steel (SS). Exposing 316L corrosion coupons in lakes and streams supported this conclusion; the rate and extent of ennoblement were positively correlated with the rates of deposition and the amounts of biomineralized manganese oxides deposited on the surfaces of the SS corrosion coupons. X-ray photoelectron spectroscopy (XPS) analyses of the deposits from the ennobled coupons revealed a mixture of manganese oxides, as expected. Many natural waters can support growth of MOB. When manganese-oxidizing biofilms accumulate on surfaces of passive metals there is a potential for manganese redox cycling on the metal surface. This process is initiated by depositing minute amounts of manganese oxides on the metal surface. These microbially deposited manganese oxides are then reduced by the electrons derived from anodic dissolution of the metal; the metal is corroding and the manganese oxides are reduced to divalent manganese ions. However, since the manganese ions are liberated within the manganese-oxidizing biofilm, the manganese ions are immediately reoxidized, and the cycle continues.
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Li, Zhenhao, Kunlei Wang, Jinyue Zhang, Ying Chang, Ewa Kowalska, and Zhishun Wei. "Enhanced Photocatalytic Activity of Hierarchical Bi2WO6 Microballs by Modification with Noble Metals." Catalysts 12, no. 2 (January 21, 2022): 130. http://dx.doi.org/10.3390/catal12020130.
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Visible-responsive photocatalysts for environmental purification and fuel generation are, currently, highly sought after. Among the possible candidates, Bi2WO6 (BWO) has been considered due to its efficient light harvesting, stability, and promising activities. Here, hierarchical BWO microballs have been prepared using a hydrothermal method, and additionally modified with deposits of noble metals (gold, silver, copper, palladium and platinum) by the photodeposition method. The structure, morphology, photoabsorption properties, and surface composition of bare and metal-modified BWO samples were investigated by XRD, SEM, DRS and XPS analyses. The photocatalytic activity was evaluated by the oxidative degradation of model dye (methyl orange (MO)) under UV/vis, and hydrogen generation under vis and/or UV irradiation. It was found that hierarchical morphology is detrimental for high photocatalytic activity in both tested systems, resulting in the improved degradation of MO (ca. 65% during 90 min of UV/vis irradiation), and hydrogen evolution (0.1 and 0.4 μmol h−1 under vis and UV/vis irradiation, respectively). Moreover, the type of noble metal and its properties influence the overall photocatalytic performance. It was found that, under UV/vis irradiation, only platinum accelerates hydrogen evolution, whereas under vis irradiation the activity follows the order: BWO < BWO/Cu < BWO/Ag < BWO/Pt < BWO/Pd < BWO/Au. It was concluded that zero-valent metal is recommended for high vis response, probably due to plasmonic photocatalysis, efficient light harvesting ability, and co-catalytic role.
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Majerič, Peter, and Rebeka Rudolf. "Advances in Ultrasonic Spray Pyrolysis Processing of Noble Metal Nanoparticles—Review." Materials 13, no. 16 (August 7, 2020): 3485. http://dx.doi.org/10.3390/ma13163485.
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In the field of synthesis and processing of noble metal nanoparticles, the study of the bottom-up method, called Ultrasonic Spray Pyrolysis (USP), is becoming increasingly important. This review analyses briefly the features of USP, to underline the physical, chemical and technological characteristics for producing nanoparticles and nanoparticle composites with Au and Ag. The main aim is to understand USP parameters, which are responsible for nanoparticle formation. There are two nanoparticle formation mechanisms in USP: Droplet-To-Particle (DTP) and Gas-To-Particle (GTP). This review shows how the USP process is able to produce Au, Ag/TiO2, Au/TiO2, Au/Fe2O3 and Ag/(Y0.95 Eu0.05)2O3 nanoparticles, and presents the mechanisms of formation for a particular type of nanoparticle. Namely, the presented Au and Ag nanoparticles are intended for use in nanomedicine, sensing applications, electrochemical devices and catalysis, in order to benefit from their properties, which cannot be achieved with identical bulk materials. The development of new noble metal nanoparticles with USP is a constant goal in Nanotechnology, with the objective to obtain increasingly predictable final properties of nanoparticles.
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Biswal, Dillip Kumar, Dibakar Bandopadhya, and Santosha Kumar Dwivedy. "Fabrication and Thermo-Mechanical Analysis of Pure Silver-Electrode Ionic Polymer-Metal Composite (IPMC) Actuator." Applied Mechanics and Materials 110-116 (October 2011): 1199–206. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.1199.
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Till to date, fabrication of Ionic Polymer-Metal Composites (IPMC) are carried out successfully using noble metal such as platinum/gold as the surface electrode. In this work we have proposed cost effective fabrication method for IPMC actuator using non-precious metal electrode of silver (Ag). Chemical decomposition method is followed using Nafion as the ion exchange membrane to fabricate pure Ag-electrode IPMC. Microscopic and morphological analyses reveal that, silver particles penetrate well through the surface of Nafion membrane. The bending deformation measurement and analysis of the thermo-mechanical properties of the fabricated IPMC is carried out. The experiment results and performance of the IPMC actuator confirm that the fabrication of pure Ag-IPMC is feasible and can be used as artificial muscle material.
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Liu, Qian, and Toshio Fukaya. "Optical Features of Noble-Metal-Oxide Thin Films Under Irradiation of Blue Laser." Journal of Nanoscience and Nanotechnology 7, no. 1 (January 1, 2007): 362–67. http://dx.doi.org/10.1166/jnn.2007.18036.
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The optical reflectance and transmittance of Platinum oxide (PtOx) and palladium oxide (PdOx) thin films for ultrahigh-density optical storage are investigated using Z-scan technique under irradiation of blue laser (442 nm). The power thresholds of the PtOx and PdOx decomposition, 3.1 mW and 2.6 mW, are obtained respectively; the PtOx (PdOx) thin film is reversible and irreversible when input power is less than and more than 3.1 mW (2.6 mW). Deformation analyses by using an atom force microscope (AFM), which is formed in the micro irradiation region of surface on the thin film samples due to decomposition of the PtOx or PdOx driving the Z-scan, agree well with the Z-scan results. The optical features obtained at 442-nm wavelength are compared with those at 532-nm wavelength, and the threshold difference between the two wavelengths is also analysed in detail based on wavelength-dependent average power density and wavelength-selected absorption of the thin films.
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Smith, G. B., G. A. Niklasson, J. S. E. M. Svensson, and C. G. Granqvist. "Noble‐metal‐based transparent infrared reflectors: Experiments and theoretical analyses for very thin gold films." Journal of Applied Physics 59, no. 2 (January 15, 1986): 571–81. http://dx.doi.org/10.1063/1.336615.
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Brinza, Loredana, Imad Ahmed, Carmen Madalina Cismasiu, Ioan Ardelean, Iuliana Gabriela Breaban, Florica Doroftei, Konstantin Ignatyev, Cristina Moisescu, and Mariana Neamtu. "Geochemical investigations of noble metal-bearing ores: Synchrotron-based micro-analyses and microcosm bioleaching studies." Chemosphere 270 (May 2021): 129388. http://dx.doi.org/10.1016/j.chemosphere.2020.129388.
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Paluch, Emil, Paulina Sobierajska, Piotr Okińczyc, Jarosław Widelski, Anna Duda-Madej, Barbara Krzyżanowska, Paweł Krzyżek, et al. "Nanoapatites Doped and Co-Doped with Noble Metal Ions as Modern Antibiofilm Materials for Biomedical Applications against Drug-Resistant Clinical Strains of Enterococcus faecalis VRE and Staphylococcus aureus MRSA." International Journal of Molecular Sciences 23, no. 3 (January 28, 2022): 1533. http://dx.doi.org/10.3390/ijms23031533.
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The main aim of our research was to investigate antiadhesive and antibiofilm properties of nanocrystalline apatites doped and co-doped with noble metal ions (Ag+, Au+, and Pd2+) against selected drug-resistant strains of Enterococcus faecalis and Staphylococcus aureus. The materials with the structure of apatite (hydroxyapatite, nHAp; hydroxy-chlor-apatites, OH-Cl-Ap) containing 1 mol% and 2 mol% of dopants and co-dopants were successfully obtained by the wet chemistry method. The majority of them contained an additional phase of metallic nanoparticles, in particular, AuNPs and PdNPs, which was confirmed by the XRPD, FTIR, UV–Vis, and SEM–EDS techniques. Extensive microbiological tests of the nanoapatites were carried out determining their MIC, MBC value, and FICI. The antiadhesive and antibiofilm properties of the tested nanoapatites were determined in detail with the use of fluorescence microscopy and computer image analysis. The results showed that almost all tested nanoapatites strongly inhibit adhesion and biofilm production of the tested bacterial strains. Biomaterials have not shown any significant cytotoxic effect on fibroblasts and even increased their survival when co-incubated with bacterial biofilms. Performed analyses confirmed that the nanoapatites doped and co-doped with noble metal ions are safe and excellent antiadhesive and antibiofilm biomaterials with potential use in the future in medical sectors.
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Abo-Elsoud, M. "Microstructures and Synthesis of Noble Metal-Based Bulk Metallic Glasses (Zr-Be-Ni-Ti)." Advanced Engineering Forum 17 (June 2016): 1–6. http://dx.doi.org/10.4028/www.scientific.net/aef.17.1.
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High-energy ball-milling in hexane medium was employed to prepare Nobel Zr-based bulk metallic glasses (BMGs) alloy of three different nominal compositions Zr47Be23Ni15Ti15, Zr50Be20Ni15Ti15 and Zr52Be18Ni15Ti15, numbers indicate at.%). The glass forming ability was found to increase with decreasing Zr and increasing Be content, which can be ascribed to the enhanced atomic size mismatch of the constituents on Be addition. Amorphous Zr47Be23Ni15Ti15 powder undergoes two-stage crystallization with onset temperatures at 640 and 700 K and glass transition temperature Tg at 566 K. In contrast, the Zr50Be20Ni15Ti15 and Zr52Be18Ni15Ti15 samples remained crystalline to a certain extent even after prolonged milling and contained FCC Zr crystallites. Structural characterization was done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, thermal analyses were performed by means of differential scanning calorimetry (DSC) thermogram to justify the experimental findings.
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Wang, Yinghui, Honglan Huang, Honglei Lin, Lei Jiang, Yu Pan, Xiurong Li, and Hui Cheng. "The Influence of Recycling on the Properties of Interface between Ceramic and Dental Alloys." BioMed Research International 2020 (April 8, 2020): 1–9. http://dx.doi.org/10.1155/2020/3529781.
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Statement of Problem. Results are discrepant regarding the metal-ceramic interface of dental alloys affected by recycling. Purpose. The purpose of this study was to evaluate the effect of recycling on the properties of interface between 2 dental alloys and their corresponding porcelains. Materials and Methods. Noble alloy (Pd-Cu-Ga) and high-noble alloy (Au-Pt) were used in this study. Metal matrices (cylinders Φ4 mm×4 mm with pedestal Φ5 mm×1 mm) were prepared by arc melting in argon after recasting 1-3 times. Corresponding porcelain with overall dimensions of Φ4 mm×2 mm was veneered on each metal cylinder. There were 22 specimens in each alloy group. Specifically, two specimens of each group were chosen randomly for interfacial morphology and diffusion analyses by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The remaining 20 specimens were divided into 2 groups with or without thermal cycling. The bond strength was evaluated by shear test, and the data were analyzed by two-way analysis of variance (ANOVA). The failure mode of shear test specimen was observed with a stereoscopic microscopy and subjected to the exact probability test (α=0.05). Results. According to the results from SEM, no obvious difference was observed in the interfacial morphology of both Pd-Cu-Ga and Au-Pt alloys among different recasting specimens. EDS analysis revealed that no significant difference was found in the width of elemental diffusion among 2 test alloys after recycling 1-3 times. Notably, in Pd-Cu-Ga alloy groups, the peak of Ga in thrice recasting was lower than those in first and second recastings. And there was no significant difference (P>0.05) in the metal-ceramic shear bond strength of Pd-Cu-Ga and Au-Pt alloys after recycling 1-3 times, with or without thermal cycling. The results of failure modes observed on specimens were not affected by the recycling and thermal cycling in the 2 tested alloys. Conclusions. Within the limitations of this study, the Pd-Cu-Ga and Au-Pt alloys can be recycled 2 times without significant changes on the properties of metal-ceramic interface, with or without thermal cycling.
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Kuleshevich, L. V. "Noble-metal associations related to Paleoproterozoic basic-hyperbasic magmatism in the Lapland-Onega province of Karelia." Vestnik of Geosciences 9 (2020): 14–18. http://dx.doi.org/10.19110/geov.2020.9.3.
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Topomineralogical studies are part of mineralogenic research conducted in the Paleoproterozoic Lapland-Onega rift-related structure in Karelia. These studies are important because of the location of promising areas and the study of deposits associated with basic-hyperbasic magmatism in Paleoproterozoic rift-related structures (chromite, titanomagnetite and nickel ores with PGE and gold). The aim of mineralogenic studies is to better understand major ore and noble-metal mineral associations by microprobe and ICP-MS-analyses. It was found that chromite ores are accompanied by high-temperature associations of platinoids — arsenides, sulfo-arsenides Pt, Rh, Ir and bismutotellurides Pt (with Pd), and sulfide Cu-Ni ores — mainly Pt-Pd bismutotellurides and tellurides. Titanomagnetite ores with low-sulfide copper mineralization contain stibio-sulfoarsenides, antimonides, stannides, and more rarely sulfides of Pd, Pd-Pt, and silver-containing gold.
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Suber, Lorenza, Luciano Pilloni, Kshitij Khanna, Giuliana Righi, Ludovica Primitivo, Martina De Angelis, and Daniela Caschera. "Fine-Tuning Synthesis of Fluorescent Silver Thiolate Nanoclusters." Journal of Nanoscience and Nanotechnology 21, no. 5 (May 1, 2021): 2816–23. http://dx.doi.org/10.1166/jnn.2021.19048.
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Noble metal thiolate nanoclusters are a new class of nanomaterials with molecular-like properties such as high dispersibility and fluorescence in the visible and infrared spectral region, properties highly requested in biomedicine for imaging, sensing and drug delivery applications. We report on three new silver phenylethane thiolate nanoclusters, differing for slight modifications of the preparation, i.e., the reaction solvent and the thiolate quantity, producing changes in the nanocluster composition as well as in the fluorescence behavior. All samples, excited in the range 250–500 nm, emit around 400 and 700 nm differing in the emission maxima and behavior. The silver thiolate nanoclusters have been characterized by way of C, H, S elemental analyses and Thermal Gravimetric Analysis (TGA) to determine the nanocluster composition, Scanning Transmission Electron Microscopy (STEM) to investigate the nanocluster morphology and UV-Vis and fluorescence spectroscopy to study their optical properties.
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Stucchi, Marta, Maela Manzoli, Filippo Bossola, Alberto Villa, and Laura Prati. "Ruling Factors in Cinnamaldehyde Hydrogenation: Activity and Selectivity of Pt-Mo Catalysts." Nanomaterials 11, no. 2 (February 1, 2021): 362. http://dx.doi.org/10.3390/nano11020362.
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To obtain selective hydrogenation catalysts with low noble metal content, two carbon-supported Mo-Pt bimetallic catalysts have been synthesized from two different molybdenum precursors, i.e., Na2MoO4 and (NH4)6Mo7O24. The results obtained by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) combined with the presence and strength of acid sites clarified the different catalytic behavior toward cinnamaldehyde hydrogenation. After impregnating the carbon support with Mo precursors, each sample was used either as is or treated at 400 °C in N2 flow, as support for Pt nanoparticles (NPs). The heating treatment before Pt deposition had a positive effect on the catalytic performance. Indeed, TEM analyses showed very homogeneously dispersed Pt NPs only when they were deposited on the heat-treated Mo/C supports, and XPS analyses revealed an increase in both the exposure and reduction of Pt, which was probably tuned by different MoO3/MoO2 ratios. Moreover, the different acid properties of the catalysts resulted in different selectivity.
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Kiss, Gabriella B., Kata Molnár, Zsolt Benkó, Péter Skoda, Zsuzsanna Kapui, Giorgio Garuti, Federica Zaccarini, László Palcsu, and György Czuppon. "Tracing the Source of Hydrothermal Fluid in Ophiolite-Related Volcanogenic Massive Sulfide Deposits: A Case Study from the Italian Northern Apennines." Minerals 13, no. 1 (December 21, 2022): 8. http://dx.doi.org/10.3390/min13010008.
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The Italian Northern Apennines contain several Fe-Cu-Zn-bearing, Cyprus-type volcanogenic massive sulfide (VMS) deposits, which significantly contribute to the Cu resources of Italy. The massive sulfide lenses and related stockwork mineralizations are hosted by several levels (from basalt to serpentinite) of the unmetamorphosed ophiolitic series; therefore, this region offers perfect locations to study the ore-forming hydrothermal system in detail. A combination of fluid inclusion microthermometry, Raman spectroscopy, electron probe analyses (chlorite thermometry) and stable and noble gas isotope geochemistry was used to determine the fluid source of the VMS system at Bargone, Boccassuolo, Campegli, Casali–Monte Loreto, Corchia, Reppia and Vigonzano. This question of the fluid source is the focus of modern VMS research worldwide, as it has a direct influence on the metal content of the deposit. The obtained temperature and compositional data are both in the typical range of VMS systems and basically suggest evolved seawater origin for the mineralizing fluid. Modification of seawater was most commonly due to fluid–rock interaction processes, which happened during long-lasting circulation in the crust. The role of a small amount of magmatic fluid input was traced only at the lower block of Boccassuolo, which may be responsible for its higher ore grade. This fluid origin model is evidenced by O, H and C stable isotopic as well as He, Ne and Ar noble gas isotopic values.
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Slavkova, Z., J. Genova, H. Chamati, V. Boev, and D. Yancheva. "Silver nanoparticles synthesis and their effect on the SOPC lipid structure." Journal of Physics: Conference Series 2240, no. 1 (March 1, 2022): 012019. http://dx.doi.org/10.1088/1742-6596/2240/1/012019.
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Abstract We focus our attention on the influence of hydrophobic silver nanoparticles (Ag NPs) on the 1-Stearoyl-2-oleoylsn-glycero-3-phosphocholine (SOPC) model system. Results obtained by differential scanning calorimetry (DSC) and infrared (IR) spectroscopy were compared to their counterpart for lipid systems with incorporated hydrophobic gold nanoparticles (AuNPs) and pure SOPC lipid in a water environment. The results show a strong effect of hindering the gel-to-liquid crystalline phase transition for both types of noble metal hydrophobic NPs. The effect of the phase transitions shift to the lower temperatures is more pronounced for the silver particles for the concentrations studied. According to the IR spectral analyses, no negative effect is observed of the NPs on the lipid hydration for the concentration studied, and the plasmon effect of the Ag NPs appears to be more pronounced.
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Li, Qiao-ling, Xiao-yong He, Yue-qing Zhang, and Xiao-feng Yang. "Preparation and Microwave Absorbing Properties of an Electroless Ni-Co Coating on Multiwall Carbon Nanotubes Using [Ag(NH3)2]+as Activator." Journal of Nanomaterials 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/404698.
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Ni-Co-coated carbon nanotubes (CNTs) composites with different molar ratios of Ni/Co were synthesized using [Ag(NH3)2]+as activator andH2PO2-as reductant, thereby replacing the conventional noble metal Pd salt activator and Sn2+reductant. Scanning electron microscopy, X-ray diffraction, and X-ray energy dispersive spectrometry analyses demonstrated that the CNTs were deposited with a dense, uniform Ni-Co coating. The possible mechanism of the electroless method was studied, which indicates that pure Ag0acted as a nucleation site for subsequent Ni-Co-P deposition. Network vector analyzer measurements indicated that the composite with only Ni coated had an absorbing value of −12.6 dB and the composite with a Ni/Co ratio of four had the maximum wave absorption (−15.6 dB) and the widest absorption bandwidth (800 MHz, RL < −10 dB), while the saturation magnetization (Ms) was 4.28 emu·g−1and the coercive force (Hc) was 31.33 Oe.
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Rozmysłowska-Wojciechowska, A., E. Karwowska, S. Poźniak, T. Wojciechowski, L. Chlubny, A. Olszyna, W. Ziemkowska, and A. M. Jastrzębska. "Influence of modification of Ti3C2 MXene with ceramic oxide and noble metal nanoparticles on its antimicrobial properties and ecotoxicity towards selected algae and higher plants." RSC Advances 9, no. 8 (2019): 4092–105. http://dx.doi.org/10.1039/c8ra07633b.
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Schematic representation of the concept of present study. The flowchart shows the process of surface-modification of Ti3C2 MXene and the subsequent ecotoxicological analyses employed.
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Ali, A., M. A. Ashraf, Q. A. Minhas, Q. A. Naqvi, M. A. Baqir, and P. K. Choudhury. "On the Core-Shell Nanoparticle in Fractional Dimensional Space." Materials 13, no. 10 (May 22, 2020): 2400. http://dx.doi.org/10.3390/ma13102400.
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The investigation of core-shell nanoparticles has been greatly exciting in biomedical applications, as this remains of prime importance in targeted drug delivery, sensing, etc. In the present work, the polarizability and scattering features of nanoparticles comprised of nano-sized dielectric/metallic core-shell structures were investigated in the fractional dimensional (FD) space, which essentially relates to the confinement of charged particles. For this purpose, three different kinds of metals—namely aluminum, gold and silver—were considered to form the shell, having a common silicon dioxide (SiO2) nanoparticle as the core. It is noteworthy that the use of noble metal-SiO2 mediums interface remains ideal to realize surface plasmon resonance. The core-shell nanoparticles were considered to have dimensions smaller than the operating wavelength. Under such conditions, the analyses of polarizability and the scattering and absorption cross-sections, and also, the extinction coefficients were taken up under Rayleigh scattering mechanism, emphasizing the effects of a varying FD parameter. Apart from these, the tuning of resonance peaks and the magnitude of surface plasmons due to FD space parameter were also analyzed. It was found that the increase of FD space parameter generally results in blue-shifts in the resonance peaks. Apart from this, the usage of gold and silver shells brings in fairly large shifts in the peak positions of wavelengths, which allows them to be more suitable for a biosensing purpose.
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Colin, Jonathan, Andreas Jamnig, Clarisse Furgeaud, Anny Michel, Nikolaos Pliatsikas, Kostas Sarakinos, and Gregory Abadias. "In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools." Nanomaterials 10, no. 11 (November 9, 2020): 2225. http://dx.doi.org/10.3390/nano10112225.
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Continued downscaling of functional layers for key enabling devices has prompted the development of characterization tools to probe and dynamically control thin film formation stages and ensure the desired film morphology and functionalities in terms of, e.g., layer surface smoothness or electrical properties. In this work, we review the combined use of in situ and real-time optical (wafer curvature, spectroscopic ellipsometry) and electrical probes for gaining insights into the early growth stages of magnetron-sputter-deposited films. Data are reported for a large variety of metals characterized by different atomic mobilities and interface reactivities. For fcc noble-metal films (Ag, Cu, Pd) exhibiting a pronounced three-dimensional growth on weakly-interacting substrates (SiO2, amorphous carbon (a-C)), wafer curvature, spectroscopic ellipsometry, and resistivity techniques are shown to be complementary in studying the morphological evolution of discontinuous layers, and determining the percolation threshold and the onset of continuous film formation. The influence of growth kinetics (in terms of intrinsic atomic mobility, substrate temperature, deposition rate, deposition flux temporal profile) and the effect of deposited energy (through changes in working pressure or bias voltage) on the various morphological transition thicknesses is critically examined. For bcc transition metals, like Fe and Mo deposited on a-Si, in situ and real-time growth monitoring data exhibit transient features at a critical layer thickness of ~2 nm, which is a fingerprint of an interface-mediated crystalline-to-amorphous phase transition, while such behavior is not observed for Ta films that crystallize into their metastable tetragonal β-Ta allotropic phase. The potential of optical and electrical diagnostic tools is also explored to reveal complex interfacial reactions and their effect on growth of Pd films on a-Si or a-Ge interlayers. For all case studies presented in the article, in situ data are complemented with and benchmarked against ex situ structural and morphological analyses.
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Adhyapak, Parag, Rohini Aiyer, Sreekantha Reddy Dugasani, Hyeong-U. Kim, Chung Kil Song, Ajayan Vinu, Venkatesan Renugopalakrishnan, et al. "Thickness-dependent humidity sensing by poly(vinyl alcohol) stabilized Au–Ag and Ag–Au core–shell bimetallic nanomorph resistors." Royal Society Open Science 5, no. 6 (June 2018): 171986. http://dx.doi.org/10.1098/rsos.171986.
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We herein report a simple chemical route to prepare Au–Ag and Ag–Au core–shell bimetallic nanostructures by reduction of two kinds of noble metal ions in the presence of a water-soluble polymer such as poly(vinyl alcohol) (PVA). PVA was intentionally chosen as it can play a dual role of a supporting matrix as well as stabilizer. The simultaneous reduction of metal ions leads to an alloy type of structure. Ag(c)–Au(s) core–shell structures display tendency to form prismatic nanostructures in conjunction with nanocubes while Au(c)–Ag(s) core–shell structures show formation of merely nanocubes. Although UV–visible spectroscopy and X-ray photoelectron spectroscopy analyses of the samples typically suggest the formation of both Ag(c)–Au(s) and Au(c)–Ag(s) bimetallic nanostructures, the definitive evidence comes from high-resolution transmission electron microscopy–high-angle annular dark field elemental mapping in the case of Au(c)–Ag(s) nanomorphs only. The resultant nanocomposite materials are used to fabricate resistors on ceramic rods having two electrodes by drop casting technique. These resistors are examined for their relative humidity (RH) response in the range (2–93% RH) and both the bimetallic nanocomposite materials offer optimized sensitivity of about 20 Kohm/% RH and 300 ohm/% RH at low and higher humidity conditions, respectively, which is better than that of individual nanoparticles.
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Liu, Tianlong, Shiliang Wang, Lizhen Hou, and Han Huang. "Synthesis of Five-fold-twinned silver microwhiskers by physical vapor deposition." International Journal of Modern Physics B 33, no. 31 (December 20, 2019): 1950371. http://dx.doi.org/10.1142/s0217979219503715.
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Pentagonal noble metal crystals, with a five-fold-twinned (FFT) structure that exhibits prominent noncrystallographic symmetry, have been the focus of research in the past several decades due to their promising applications in various fields such as chemical and biological sensors, electronics and optoelectronics. A great deal of previous experimental studies and theoretical analyses suggested that such an FFT structure could only exist in the nanoscale crystals, because of the lateral restriction in growth, or in microscale crystals with re-entrant grooves that can effectively release the internal strain. In this study, we synthesized the microscale single-crystalline and multi-twinned Ag crystals with various morphologies, using physical vapor deposition (PVD). FFT Ag microwhiskers with diameters up to 10 [Formula: see text]m were produced, but without re-entrant grooves on their side surfaces. Our findings suggest that FFT whiskers can be formed without the use of any surface-capping agents or without necessitating restriction in lateral growth. This further suggests that the current understanding of the surface passivation or the strain-restriction formation of five-fold-twined micro- and nanowhiskers needs improvement.
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Liang, Yunxia, Qiaojuan Gong, Xiaoling Sun, Nengneng Xu, Pengni Gong, and Jinli Qiao. "Fabrication of CoMN2O4 loaded nitrogen-doped graphene as bifunctional electrocatalyst for rechargeable zinc-air batteries." Functional Materials Letters 13, no. 08 (November 2020): 2051046. http://dx.doi.org/10.1142/s1793604720510467.
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Designing durable and low-cost electrocatalysts for zinc-air batteries is critical, which plays an essential role in oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this paper, the CoMn2O4/N-RGO bifunctional electrocatalyst was synthesized by a facile hydrothermal method. The electrocatalytic performance was tested toward ORR and OER under alkaline condition (0.1[Formula: see text]M KOH). The XRD, SEM and other characterization analyses were used to investigate the physicochemical properties of materials. The results showed that the electrochemical activity of CoMn2O4/N-RGO showed high power density (354[Formula: see text]mW[Formula: see text]cm[Formula: see text], small charge/discharge voltage drop (0.70[Formula: see text]V) and excellent stability cycle (200[Formula: see text]h), which are superior to the noble metal Pt/C+IrO2 electrocatalyst (the voltage drop: 0.60[Formula: see text]V at initial and 0.85[Formula: see text]V after 13[Formula: see text]h). This work provided a new method for developing the bifunctional material in zinc-air batteries.
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Cotty, Stephen Richard, and Xiao Su. "Electrochemical Recovery and Concentration of Noble Metals." ECS Meeting Abstracts MA2022-02, no. 27 (October 9, 2022): 1042. http://dx.doi.org/10.1149/ma2022-02271042mtgabs.
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Noble metals are integral materials to chemical and electronics industries for their unmatched chemical inertness, electrical conductivity, and catalytic activity. However, the growing demand for noble metals such as Pt, Pd, and Au is outpacing the dwindling supply, and without new recycle strategies these critical noble metal resources will run out. Therefore, energy and resource efficient noble metal recycling technologies are critical to develop sustainable use of these scarce and valuable resources. Recently, electrification of chemical process units has been receiving justifiable attention as an easily scalable means of increasing energy and material sustainability in industry, particularly for chemical separations. In particular, the incorporation of redox-active materials has been met with great success for chemical energy storage and chemical separations due to enhanced charge transfer and easily tunable target ion interactions. Here, we introduce an electrochemically mediated platform for capture, release, and up-concentration of noble metal complexes from mining ore, electronic waste, and valuable elements in industrial manufacturing, where favorable charge transfer binding of noble metals to electrode bound redox sites enables selective capture of target noble metals over other common competitors – all with the flick of a switch. Highlights of our system are its high uptake (>200 mg/g), selectivity (>5 vs competing ions), energy efficiency (<5 kJ/g-PGM), cyclability (>5000 reuse cycles), and scalability to flow system. Technoeconomic analysis of our system compared to current industrial separation technologies indicates economically significant improvements in capital and operating costs with our electrochemical noble metal recycling platform. By lowering the economic barrier of noble metal recycling, these critical materials can be sustainably used and reused for years to come.
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Khan, Muhammad Arif, Hongbin Zhao, Wenwen Zou, Zhe Chen, Wenjuan Cao, Jianhui Fang, Jiaqiang Xu, Lei Zhang, and Jiujun Zhang. "Recent Progresses in Electrocatalysts for Water Electrolysis." Electrochemical Energy Reviews 1, no. 4 (July 28, 2018): 483–530. http://dx.doi.org/10.1007/s41918-018-0014-z.
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Abstract The study of hydrogen evolution reaction and oxygen evolution reaction electrocatalysts for water electrolysis is a developing field in which noble metal-based materials are commonly used. However, the associated high cost and low abundance of noble metals limit their practical application. Non-noble metal catalysts, aside from being inexpensive, highly abundant and environmental friendly, can possess high electrical conductivity, good structural tunability and comparable electrocatalytic performances to state-of-the-art noble metals, particularly in alkaline media, making them desirable candidates to reduce or replace noble metals as promising electrocatalysts for water electrolysis. This article will review and provide an overview of the fundamental knowledge related to water electrolysis with a focus on the development and progress of non-noble metal-based electrocatalysts in alkaline, polymer exchange membrane and solid oxide electrolysis. A critical analysis of the various catalysts currently available is also provided with discussions on current challenges and future perspectives. In addition, to facilitate future research and development, several possible research directions to overcome these challenges are provided in this article. Graphical Abstract
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Li, Yan, Chi-Wing Tsang, Eve Man Hin Chan, Eugene Yin Cheung Wong, Danny Chi Kuen Ho, Xiao-Ying Lu, and Changhai Liang. "Sustainable Option for Hydrogen Production: Mechanistic Study of the Interaction between Cobalt Pincer Complexes and Ammonia Borane." Catalysts 10, no. 7 (June 28, 2020): 723. http://dx.doi.org/10.3390/catal10070723.
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The mechanism of the solvolysis/hydrolysis of ammonia borane by iridium (Ir), cobalt (Co), iron (Fe) and ruthenium (Ru) complexes with various PNP ligands has been revisited using density functional theory (DFT). The approach of ammonia borane (NH3BH3) to the metal center has been tested on three different possible mechanisms, namely, the stepwise, concerted and proton transfer mechanism. It was found that the theoretical analyses correlate with the experimental results very well, with the activities of the iridium complexes with different PNP ligands following the order: (tBu)2P > (iPr)2P > (Ph)2P through the concerted mechanism. The reaction barriers of the rate-determining steps for the dehydrogenation of ammonia borane catalyzed by the active species [(tBu)2PNP-IrH] (Complex I-8), are found to be 19.3 kcal/mol (stepwise), 15.2 kcal/mol (concerted) and 26.8 kcal/mol (proton transfer), respectively. Thus, the concerted mechanism is the more kinetically favorable pathway. It is interesting to find that stable (tBu)2PNP Co-H2O and (tBu)2PNP Co-NH3 chelation products exist, which could stabilize the active I-8 species during the hydrolysis reaction cycle. The use of more sterically hindered and electron-donating PNP ligands such as (adamantyl)2P- provides similar activity as the t-butyl analogue. This research provides insights into the design of efficient cobalt catalysts instead of using precious and noble metal, which could benefit the development of a more sustainable hydrogen economy.
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Tzamos, Evangelos, Platon N. Gamaletsos, Giovanni Grieco, Micol Bussolesi, Anthimos Xenidis, Anastasios Zouboulis, Dimitrios Dimitriadis, Yiannis Pontikes, and Athanasios Godelitsas. "New Insights into the Mineralogy and Geochemistry of Sb Ores from Greece." Minerals 10, no. 3 (March 6, 2020): 236. http://dx.doi.org/10.3390/min10030236.
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Antimony is a common metalloid occurring in the form of Sb-sulfides and sulfosalts, in various base and noble metal deposits. It is also present in corresponding metallurgical products (concentrates) and, although antimony has been considered a penalty element in the past, recently it has gained interest due to its classification as a critical raw material (CRM) by the European Union (EU). In the frame of the present paper, representative ore samples from the main Sb-bearing deposits of Greece (Kilkis prefecture, Chalkidiki prefecture (Kassandra Mines), and Chios Isl.) have been investigated. According to optical microscopy and electron probe microanalysis (EPMA) data, the Greek ores contain stibnite (Sb2S3), boulangerite (Pb5Sb4S11), bournonite (PbCuSbS3), bertherite (FeSbS4), and valentinite (Sb2O3). Bulk analyses by inductively coupled plasma mass spectrometry (ICP-MS) confirmed, for the first time published, the presence of a significant Hg content in the Kilkis Sb-ore. Furthermore, Kassandra Mines ores are found to contain remarkable amounts of Bi, As, Sn, Tl, and Se (excluding Ag, which is a bonus element). The above findings could contribute to potential future exploration and exploitation of Sb ores in Greece.
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Güler, Ali Can, Jan Antoš, Milan Masař, Michal Urbánek, Michal Machovský, and Ivo Kuřitka. "Boosting the Photoelectrochemical Performance of Au/ZnO Nanorods by Co-Occurring Gradient Doping and Surface Plasmon Modification." International Journal of Molecular Sciences 24, no. 1 (December 27, 2022): 443. http://dx.doi.org/10.3390/ijms24010443.
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Band bending modification of metal/semiconductor hybrid nanostructures requires low-cost and effective designs in photoelectrochemical (PEC) water splitting. To this end, it is evinced that gradient doping of Au nanoparticles (NPs) inwards the ZnO nanorods (NRs) through thermal treatment facilitated faster transport of the photo-induced charge carriers. Systematic PEC measurements show that the resulting gradient Au-doped ZnO NRs yielded a photocurrent density of 0.009 mA/cm2 at 1.1 V (vs. NHE), which is 2.5-fold and 8-fold improved compared to those of Au-sensitized ZnO and the as-prepared ZnO NRs, respectively. The IPCE and ABPE efficiency tests confirmed the boosted photoresponse of gradient Au-incorporated ZnO NRs, particularly in the visible spectrum due to the synergistic surface plasmonic effect of Au NPs. A gradient Au dopant profile promoted the separation and transfer of the photo-induced charge carriers at the electrolyte interface via more upward band bending according to the elaborated electrochemical impedance spectroscopy and Kelvin probe force microscopy analyses. Therefore, this research presents an economical and facile strategy for preparing gradient plasmonic noble NP-incorporated semiconductor NRs, which have excellent potential in energy conversion and storage technologies.
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Santos, Jakeline Raiane D., Rafael A. Raimundo, Thayse R. Silva, Vinícius D. Silva, Daniel A. Macedo, Francisco J. A. Loureiro, Marco A. M. Torres, Domenica Tonelli, and Uílame U. Gomes. "Nanoparticles of Mixed-Valence Oxides MnXCO3-XO4 (0 ≤ X ≤ 1) Obtained with Agar-Agar from Red Algae (Rhodophyta) for Oxygen Evolution Reaction." Nanomaterials 12, no. 18 (September 13, 2022): 3170. http://dx.doi.org/10.3390/nano12183170.
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The development of efficient electrocatalysts for the oxygen evolution reaction (OER) is of paramount importance in sustainable water-splitting technology for hydrogen production. In this context, this work reports mixed-valence oxide samples of the MnXCo3-XO4 type (0 ≤ X ≤ 1) synthesized for the first time by the proteic sol-gel method using Agar-Agar as a polymerizing agent. The powders were calcined at 1173 K, characterized by FESEM, XRD, RAMAN, UV–Vis, FT-IR, VSM, and XPS analyses, and were investigated as electrocatalysts for the oxygen evolution reaction (OER). Through XRD analysis, it was observed that the pure cubic phase was obtained for all samples. The presence of Co3+, Co2+, Mn2+, Mn3+, and Mn4+ was confirmed by X-ray spectroscopy (XPS). Regarding the magnetic measurements, a paramagnetic behavior at 300 K was observed for all samples. As far as OER is concerned, it was investigated in an alkaline medium, where the best overpotential of 299 mV vs. RHE was observed for the sample (MnCo2O4), which is a lower value than those of noble metal electrocatalysts in the literature, together with a Tafel slope of 52 mV dec−1, and excellent electrochemical stability for 15 h. Therefore, the green synthesis method presented in this work showed great potential for obtaining electrocatalysts used in the oxygen evolution reaction for water splitting.
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Jamnig, Andreas, Nikolaos Pliatsikas, Gregory Abadias, and Kostas Sarakinos. "Manipulation of thin metal film morphology on weakly interacting substrates via selective deployment of alloying species." Journal of Vacuum Science & Technology A 40, no. 3 (May 2022): 033407. http://dx.doi.org/10.1116/6.0001700.
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We demonstrate a versatile concept for manipulating morphology of thin (≤25 nm) noble-metal films on weakly interacting substrates using growth of Ag on SiO2 as a model system. The concept entails deployment of minority metallic (Cu, Au, Al, Ti, Cr, and Mo) alloying species at the Ag-layer growth front. Data from in situ and real-time monitoring of the deposition process show that all alloying agents—when deployed together with Ag vapor throughout the entire film deposition—favor two-dimensional (2D) growth morphology as compared to pure Ag film growth. This is manifested by an increase in the substrate area coverage for a given amount of deposited material in discontinuous layers and a decrease of the thickness at which a continuous layer is formed, though at the expense of a larger electrical resistivity. Based on ex situ microstructural analyses, we conclude that 2D morphological evolution under the presence of alloying species is predominantly caused by a decrease of the rate of island coalescence completion during the initial film-formation stages. Guided by this realization, alloying species are released with high temporal precision to selectively target growth stages before and after coalescence completion. Pre-coalescence deployment of all alloying agents yields a more pronounced 2D growth morphology, which for the case of Cu, Al, and Au is achieved without compromising the Ag-layer electrical conductivity. A more complex behavior is observed when alloying atoms are deposited during the post-coalescence growth stages: Cu, Au, Al, and Cr favor 2D morphology, while Ti and Mo yield a more pronounced three-dimensional morphological evolution. The overall results presented herein show that targeted deployment of alloying agents constitutes a generic platform for designing bespoken heterostructures between metal layers and technologically relevant weakly interacting substrates.
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Marty, Bernard. "Origins and Early Evolution of the Atmosphere and the Oceans." Geochemical Perspectives 9, no. 2 (October 2020): 135–313. http://dx.doi.org/10.7185/geochempersp.9.2.
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My journey in science began with the study of volcanic gases, sparking an interest in the origin, and ultimate fate, of the volatile elements in the interior of our planet. How did these elements, so crucial to life and our surface environment, come to be sequestered within the deepest regions of the Earth, and what can they tell us about the processes occurring there? My approach has been to establish geochemical links between the noble gases, physical tracers par excellence, with major volatile elements of environmental importance, such as water, carbon and nitrogen, in mantle-derived rocks and gases. From these analyses we have learned that the Earth is relatively depleted in volatile elements when compared to its potential cosmochemical ancestors (e.g., ~2 ppm nitrogen compared to several hundreds of ppm in primitive meteorites) and that natural fluxes of carbon are two orders of magnitude lower than those emitted by current anthropogenic activity. Further insights into the origin of terrestrial volatiles have come from space missions that documented the composition of the proto-solar nebula and the outer solar system. The consensus behind the origin of the atmosphere and the oceans is evolving constantly, although recently a general picture has started to emerge. At the dawn of the solar system, the volatile-forming elements (H, C, N, noble gases) that form the majority of our atmosphere and oceans were trapped in solid dusty phases (mostly in ice beyond the snowline and organics everywhere). These phases condensed from the proto-solar nebula gas, and/or were inherited from the interstellar medium. These accreted together within the next few million years to form the first planetesimals, some of which underwent differentiation very early on. The isotopic signatures of volatiles were also fixed very early and may even have preceded the first episodes of condensation and accretion. Throughout the accretion of the Earth, volatile elements were delivered by material from both the inner (dry, volatile-poor) and outer (volatile-rich) solar system. This delivery was concomitant with the metals and silicates that form the bulk of the planet. The contribution of bodies that formed in the far outer solar system, a region now populated by comets, is likely to have been very limited. In that sense, volatile elements were contributed continuously throughout Earth’s accretion from inner solar system reservoirs, which also provided the silicates and metal building blocks of the inner planets. Following accretion, it likely took a few hundred million years for the Earth’s atmosphere and oceans to stabilise. Luckily, we have been able to access a compositional record of the early atmosphere and oceans through the analysis of palaeo-atmospheric fluids trapped in Archean hydrothermal quartz. From these analyses, it appears that the surface reservoirs of the Earth evolved due to interactions between the early Sun and the top of the atmosphere, as well as the development of an early biosphere that progressively altered its chemistry.
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Giurlani, Walter, Patrick Marcantelli, Francesco Benelli, Daniele Bottacci, Filippo Gambinossi, Maurizio Passaponti, Antonio De Luca, Emanuele Salvietti, and Massimo Innocenti. "Corrosion Resistance Test of Electroplated Gold and Palladium Using Fast Electrochemical Analysis." Coatings 9, no. 6 (June 21, 2019): 405. http://dx.doi.org/10.3390/coatings9060405.
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Noble metal coatings are commonly employed to improve corrosion resistance of metals in the electronic and jewellery industry. The corrosion resistance of electroplated goods is currently determinate with long, destructive and almost subjective interpretation corrosion tests in artificial atmosphere. In this study we present the application of electrochemical analysis to obtain fast and numerical information of the antiaging coating. We performed open circuit potential (OCP) and corrosion current measurement; we employed also the electrochemical impedance spectroscopy (EIS), commonly applied to organic or passivated metal with high-impedance, to find the best option for noble low-impedance coating analysis. For comparison, traditional standardized tests (damp heat ISO 17228, salt spray ISO 9227 and sulphur dioxide ISO 4524) were also performed.
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Wei, Endo-Kimura, Wang, Colbeau-Justin, and Kowalska. "Influence of Semiconductor Morphology on Photocatalytic Activity of Plasmonic Photocatalysts: Titanate Nanowires and Octahedral Anatase Nanoparticles." Nanomaterials 9, no. 10 (October 11, 2019): 1447. http://dx.doi.org/10.3390/nano9101447.
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Octahedral anatase particles (OAP) with eight exposed and thermodynamically most stable (101) facets were prepared by an ultrasonication-hydrothermal (US-HT) reaction from potassium titanate nanowires (TNW). The precursor (TNW) and the product (OAP) of US-HT reaction were modified with nanoparticles of noble metals (Au, Ag or Pt) by photodeposition. Samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), scanning transmission electron microscopy (STEM) and time-resolved microwave conductivity (TRMC). The photocatalytic activity was investigated in three reaction systems, i.e., anaerobic dehydrogenation of methanol and oxidative decomposition of acetic acid under UV/vis irradiation, and oxidation of 2-propanol under vis irradiation. It was found that hydrogen liberation correlated with work function of metals, and thus the most active were platinum-modified samples. Photocatalytic activities of bare and modified OAP samples were much higher than those of TNW samples, probably due to anatase presence, higher crystallinity and electron mobility in faceted NPs. Interestingly, noble metals showed different influence on the activity depending on the semiconductor support, i.e., gold-modified TNW and platinum-modified OAP exhibited the highest activity for acetic acid decomposition, whereas silver- and gold-modified samples were the most active under vis irradiation, respectively. It is proposed that the form of noble metal (metallic vs. oxidized) as well as the morphology (well-organized vs. uncontrolled) have a critical effect on the overall photocatalytic performance. TRMC analysis confirmed that fast electron transfer to noble metal is a key factor for UV activity. It is proposed that the efficiency of plasmonic photocatalysis (under vis irradiation) depends on the oxidation form of metal (zero-valent preferable), photoabsorption properties (broad localized surface plasmon resonance (LSPR)), kind of metal (silver) and counteraction of “hot” electrons back transfer to noble metal NPs (by controlled morphology and high crystallinity).
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de Beer, Martin, Michael Claeys, and Eric van Steen. "Preparation of Pt-Promoted Co/SiO2 Catalysts for CO Hydrogenation by Strong Electrostatic Adsorption (SEA)." Advanced Materials Research 1019 (October 2014): 357–64. http://dx.doi.org/10.4028/www.scientific.net/amr.1019.357.
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Cobalt-based Fischer-Tropsch catalysts typically contain noble metals as reduction promoters to enhance the amount of the catalytically active metal in these catalysts after activation. The noble metal is typically co-impregnated with cobalt, which does not necessarily ensure the optimum contact between the noble metal and cobalt. The noble metal can be selectively deposited on the precursor of the catalytically active metal for the Fischer-Tropsch synthesis, if strong electrostatic adsorption (SEA) is the dominant mechanism. The point of zero charge of silica (Davisil 646) (PZC = 2-3) and that of Co3O4(PZC = 9-10) differs significantly. This results in a pH region where it is theoretically possible to selectively deposit the noble metal onto Co3O4using anionic exchange (e.g. using PtCl62-). The effect of pH on the uptake of these metal anions was investigated and found that adsorption is favored at low pHs. The reduction characteristics of Co3O4/SiO2,promoted by SEA, were investigated by temperature programmed reduction (TPR) and thermal gravimetric analysis (TGA). The peak maxima for reduction temperature for both steps of the reduction of Co3O4to CoO and of CoO to Co3O4decrease in the promoted catalyst, the activation energy for the first step decreased from 84±11kJ/mol to 50kJ/mol upon promotion. The degree of reduction was also noted to increase from 48% in unpromoted Co/SiO2to 56% and 84% in two different Pt-Co/SiO2systems.
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Jo, Seung Geun, Chung-Soo Kim, Sang Jun Kim, and Jung Woo Lee. "Phase-Controlled NiO Nanoparticles on Reduced Graphene Oxide as Electrocatalysts for Overall Water Splitting." Nanomaterials 11, no. 12 (December 13, 2021): 3379. http://dx.doi.org/10.3390/nano11123379.
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Efficient water electrolysis is one of the key issues in realizing a clean and renewable energy society based on hydrogen fuel. However, several obstacles remain to be solved for electrochemical water splitting catalysts, which are the high cost of noble metals and the high overpotential of alternative catalysts. Herein, we suggest Ni-based alternative catalysts that have comparable performances with precious metal-based catalysts and could be applied to both cathode and anode by precise phase control of the pristine catalyst. A facile microwave-assisted procedure was used for NiO nanoparticles anchored on reduced graphene oxide (NiO NPs/rGO) with uniform size distribution in ~1.8 nm. Subsequently, the Ni-NiO dual phase of the NPs (A-NiO NPs/rGO) could be obtained via tailored partial reduction of the NiO NPs/rGO. Moreover, we demonstrate from systematic HADDF-EDS and XPS analyses that metallic Ni could be formed in a local area of the NiO NP after the reductive annealing procedure. Indeed, the synergistic catalytic performance of the Ni-NiO phase of the A-NiO NPs/rGO promoted hydrogen evolution reaction activity with an overpotential as 201 mV at 10 mA cm−2, whereas the NiO NPs/rGO showed 353 mV. Meanwhile, the NiO NPs/rGO exhibited the most excellent oxygen evolution reaction performance among all of the Ni-based catalysts, with an overpotential of 369 mV at 10 mA cm−2, indicating that they could be selectively utilized in the overall water splitting. Furthermore, both catalysts retained their activities over 12 h with constant voltage and 1000 cycles under cyclic redox reaction, proving their high durability. Finally, the full cell capability for the overall water electrolysis system was confirmed by observing the generation of hydrogen and oxygen on the surface of the cathode and anode.
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Jagerová, Adéla, Josef Flaks, Zdeněk Sofer, Marek Vronka, Alena Michalcová, and Anna Macková. "The synthesis of Au-NPs by ion implantation in the crystalline GaN and characterisation of their optical properties." EPJ Web of Conferences 261 (2022): 01003. http://dx.doi.org/10.1051/epjconf/202226101003.
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Nanostructured surfaces with embedded noble metal nanoparticles is an attractive way for manipulation with the optical properties of wide bandgap semiconductors applied in optoelectronics, photocatalytic processes or for Surface-Enhanced Raman spectroscopy. Ion implantation offers an effective way for nanoparticle preparation without the use of additional chemicals that offers precise control of nanoparticle depth distribution. The aim of this study is a synthesis of the gold nanoparticles in GaN by implantation of 1.85 MeV Au ions with high fluences up to 7×1016 cm-2 and study of optical properties of Au implanted GaN. Implanted crystals were annealed at 800 °C in an ammonia atmosphere for 20 min to support Au nanoparticle creation and GaN recovery. The structure characterisation has been realized by Rutherford backscattering spectroscopy in channelling mode and it showed the formation of two separated disordered regions – the surface region and buried layer. The lower implantation fluences induce damage mainly in a buried layer; however, the increase of the Au-ion fluence leads to the increase of surface disorder as well. Further, the increase of the Au-ion fluence induces the Au dopant shift to the surface and multimodal Audepth profiles. TEM analyses confirmed the formation of Au nanoparticles in the implanted samples after annealing with sizes up to 14 nm. The increase of light absorption and modification of GaN bandgap of the Au modified GaN was deduced from the change in optical transmission spectra between 370 – 1400 nm.
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Joshi, Hira, Siddharth Choudhary, and S. Annapoorni. "Composite Nanostructures for Enhanced Plasmonics." Materials Science Forum 950 (April 2019): 165–69. http://dx.doi.org/10.4028/www.scientific.net/msf.950.165.
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Enhancement in plasmonic response of metal nanoparticles in the form of metal/metal oxide nanocomposites is very interesting from both the theoretical understanding and application. Metal based oxide/Ag nanocomposites were synthesized by polyol process. Metal oxide nanoparticles present in nanocomposites as core and noble metal as a shell are of interest in investigation of plasmonic behavior of noble metals and sensing application. Cobalt ferrite (CoFe2O4) and ZnO were used as oxide core in the form of spherical and rod nanostructures respectively. Presence of Ag was confirmed by XRD and SEM analysis. In this paper we summarize the synthesis and characterization of plasmonic properties of composite nanostructures. Optical absorption studies performed on CoFe2O4@Ag and ZnO@Ag exhibit sharp plasmonic resonance but shifted towards lower wavelength (blue shift). An attempt has been made to explain this shift using the Mie scattering calculations based on size variation and change in the dielectric of the surrounding medium.
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Krylova, L. N. "Efficiency of using ozone for extraction of metals from mineral raw materials." Izvestiya Vuzov. Tsvetnaya Metallurgiya (Universities' Proceedings Non-Ferrous Metallurgy) 28, no. 2 (April 14, 2022): 4–15. http://dx.doi.org/10.17073/0021-3438-2022-2-4-15.
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The paper summarizes the results of studies on the use of ozone for the extraction of non-ferrous, rare and noble metals from ores, beneficiation concentrates and technogenic raw materials identified from world scientific publications and in patent literature since the early 20th century. Ozone is a strong oxidizing agent with an oxidizing potential 1.5 times higher than the potential of chlorine in an acidic environment. Even refractory metals and minerals dissolve with ozone. Metal extraction from mineral raw materials using ozone does not contaminate processed products or generate any hazardous waste. The paper presents a significant number of studies on the use of ozone to dissolve gold and other noble metals in mineral acids showing an increase in the extraction of metals into the solution. The cyanide and thiourea leaching of gold from mineral raw materials with the replacement of oxygen with ozone was investigated. The paper provides the results of the vat and heap leaching of non-ferrous and noble metals using ozone obtained by air or oxygen irradiation with ultraviolet light, in particular with the use of photoelectrochemical treatment. These results were used as a basis for patenting new technologies. The effectiveness of ozone used in the flotation concentration of mineral raw materials, purification and detoxification of solutions and solid products of metallurgical processing, regeneration of other oxidants, metal extraction from process solutions was evaluated. The results of studies on using ozone for the vat leaching of metals from refractory sulfide ores and sulfide beneficiation concentrates in an acid solution, and the study of the ozone-assisted oxidation kinetics of copper, iron, zinc, and molybdenum sulfide minerals are summarized. The paper provides and analyzes the results of using ozone in a combination with other oxidants – hydrogen peroxide and iron (III) ions – for metal extraction from sulfide mineral raw materials in a sulfuric acid. According to the results of most of the studies carried out, it can be concluded that the use of ozone is effective for metal extraction from mineral raw materials as it improves process performance (metal extraction into the solution, selectivity of metal extraction from complex raw materials), and reduces processing time.
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KOMINAMI, Haruyuki, and Yoshinari SUZUKI. "Comprehensive Analyses of 67 Elements Including Noble Metal Elements (Ru, Rh, Pd, Os, Ir, Pt, and Au) in River Samples by Inductively Coupled Plasma Tandem Quadrupole Mass Spectrometry and Its Application to Geochemical and Environmental Chemical Analysis." Bunseki kagaku 66, no. 11 (2017): 825–37. http://dx.doi.org/10.2116/bunsekikagaku.66.825.
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Zhang, Jing, Li Wang, Wenwen Liu, Mengsha Cao, Jing Zhang, Ningyi Yuan, Shuai Zhang, and Zhongze Gu. "Synthesis of Au or Pt@Perovskite Nanocrystals via Interfacial Photoreduction." Catalysts 11, no. 2 (January 27, 2021): 174. http://dx.doi.org/10.3390/catal11020174.
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The surface modification of perovskite nanocrystals (NCs) (i.e., their decoration with noble metals) holds great promise with respect to the tailoring of their properties but has remained a challenge because perovskite NCs are extremely sensitive to water and alcohols. In this study, Au or Pt@CsPbBr3 NCs were successfully synthesized by photoreduction at the water/hexane interface. First, Cs4PbBr6 NCs were synthesized through the hot-injection method. Then, Cs4PbBr6 was transformed into CsPbBr3 and subjected to noble metal modification, both at the interface. The synthesized CsPbBr3 NCs exhibited a cubic perovskite phase and had an average size of approximately 13.5 nm. The deposited Au and Pt nanoparticles were crystalline, with a face-centered cubic lattice and average diameters of approximately 3.9 and 4.4 nm, respectively. The noble metal modification process had almost no effect on the steady-state photoluminescence (PL) emission wavelength but affected the charge-recombination kinetics of the CsPbBr3 NCs. Time-resolved PL decay spectral analysis indicated that the fluorescence lifetimes of the Au and Pt@CsPbBr3 NCs were shorter than those of the pure CsPbBr3 NCs, probably owing to the quenching of the free charges because of electron transfer from the perovskite to the noble metal nanoparticles.
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Zhao, Rui, Jia Xiang, Bo Wang, Lin Chen, and Songwen Tan. "Recent Advances in the Development of Noble Metal NPs for Cancer Therapy." Bioinorganic Chemistry and Applications 2022 (January 28, 2022): 1–14. http://dx.doi.org/10.1155/2022/2444516.
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With the development of nanotechnology, noble metal nanoparticles are widely used in the treatment of cancer due to their unique optical properties, excellent biocompatibility, surface effects, and small size effects. In recent years, researchers have designed and synthesized a large number of nanomedicines that can be used for cancer treatment based on the morphology, physical and chemical properties, mechanism of action, and toxicological studies of noble metal nanoparticles. Furthermore, the integration of diagnosis and treatment, hyperthermia, cytotoxicity research, and drug delivery system based on the study of noble metal nanoparticles can be used as effective means for cancer treatment. This article focuses on the analysis of noble metal nanoparticles that are widely used in the treatment of cancer, such as gold nanoparticles, silver nanoparticles, platinum nanoparticles, and palladium nanoparticles. The various methods and mechanisms of action of noble metal nanoparticles in the treatment of cancer are objectively summarized in detail. Based on the research on the therapeutic safety and toxicity of noble metal nanoparticles, the development prospect of noble metal nanoparticles in the future clinical application is prospected.
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Tang, Liang, Jian Zhao, Xiao Wang, Jiajun Wang, and Peng Zhang. "Engineering Noble Metal-like Bi onto Hierarchical SrWO4 for the Enhancement of Photocatalytic Activity." Catalysts 12, no. 7 (July 18, 2022): 787. http://dx.doi.org/10.3390/catal12070787.
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Solar-driven hydrogen production from water has attracted increasing attention due to sustainable H2 fuel generation with zero-emissions. However, the design of a photocatalyst without noble metals to enable efficient water splitting is still critical for practical applications. In this study, the hierarchical microspheres of SrWO4 assembled with well-defined metallic Bi nanoparticles were synthesized through mild hydrothermal aging. The resultant photocatalyst with optimum proportion exhibited the competitive performance of a high hydrogen-generation rate at 4.5 mmol·h−1·g−1, outperforming SrWO4 and Bi by factors of 2.0 and 2.4, respectively. Both the experimental characterization and active analysis revealed that the synergistic effect of noble metal-like behavior of Bi and their electron-sink capacity mainly contribute to boosting the overall photocatalytic efficiency. This work may provide advanced insights into the application of economical bismuth elements as co-catalysts, instead of noble metals, to improve photocatalytic efficiency in solar-fuel conversion and environmental remediation.
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Marshall, R. S., R. G. Kelly, A. Goff, and C. Sprinkle. "Galvanic Corrosion Between Coated Al Alloy Plate and Stainless Steel Fasteners, Part 1: FEM Model Development and Validation." Corrosion 75, no. 12 (October 2, 2019): 1461–73. http://dx.doi.org/10.5006/3308.
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Aerospace structures often involve dissimilar materials to optimize structural performance and cost. These materials can then lead to the formation of galvanic couples when moisture is present. Specifically, noble metal fasteners (such as SS316) are often used in aluminum alloy load-bearing structures, which can lead to accelerated, localized corrosion attack of the aluminum alloy due to the cathodic current supplied by the SS316 fastener. This localized attack is difficult to predict, and tests are often expensive, so modeling of these galvanic couples could be of great utility. The work reported here focuses on the galvanic coupling between fasteners installed in a panel test assembly, and the resultant corrosion damage down the fastener holes. This arrangement is a common assembly geometry in aerospace applications. A specific sol-gel coating was applied to the fasteners, to determine its effectiveness on mitigating galvanic corrosion; bare fasteners were also tested, to investigate a worst-case scenario. Geometric constraints in the model were made to match those of an experimental test panel, which was exposed to ASTM B117 salt fog for 504 h. The electrochemical boundary conditions were generated in solutions appropriate to the material and environment to which it would be exposed. Anodic charge passed during exposure was calculated from image analyses of the corrosion damage in the experimental test, and the results were compared with the model. The Laplacian-based model provides a very good first approximation for predicting the damage within the fastener hole. Validation was provided by both experimental results generated in this study as well as comparison to results in the literature that used similar, but not identical, conditions.
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Marikutsa, Artem, Marina Rumyantseva, Elizaveta A. Konstantinova, and Alexander Gaskov. "The Key Role of Active Sites in the Development of Selective Metal Oxide Sensor Materials." Sensors 21, no. 7 (April 6, 2021): 2554. http://dx.doi.org/10.3390/s21072554.
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Development of sensor materials based on metal oxide semiconductors (MOS) for selective gas sensors is challenging for the tasks of air quality monitoring, early fire detection, gas leaks search, breath analysis, etc. An extensive range of sensor materials has been elaborated, but no consistent guidelines can be found for choosing a material composition targeting the selective detection of specific gases. Fundamental relations between material composition and sensing behavior have not been unambiguously established. In the present review, we summarize our recent works on the research of active sites and gas sensing behavior of n-type semiconductor metal oxides with different composition (simple oxides ZnO, In2O3, SnO2, WO3; mixed-metal oxides BaSnO3, Bi2WO6), and functionalized by catalytic noble metals (Ru, Pd, Au). The materials were variously characterized. The composition, metal-oxygen bonding, microstructure, active sites, sensing behavior, and interaction routes with gases (CO, NH3, SO2, VOC, NO2) were examined. The key role of active sites in determining the selectivity of sensor materials is substantiated. It was shown that the metal-oxygen bond energy of the MOS correlates with the surface acidity and the concentration of surface oxygen species and oxygen vacancies, which control the adsorption and redox conversion of analyte gas molecules. The effects of cations in mixed-metal oxides on the sensitivity and selectivity of BaSnO3 and Bi2WO6 to SO2 and VOCs, respectively, are rationalized. The determining role of catalytic noble metals in oxidation of reducing analyte gases and the impact of acid sites of MOS to gas adsorption are demonstrated.
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Liu, Man Man, Dong Yan, Ping Feng, Jian Pu, Bo Chi, and Jian Li. "Diffusion Phenomenon of Precious Metal Electrode Elements into Ceramic Electrolytes after Working Process at SOFC and Sensors." Key Engineering Materials 768 (April 2018): 167–71. http://dx.doi.org/10.4028/www.scientific.net/kem.768.167.
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SOFC single cell use the preparation process of precision casting-screen printing-co-sintering and developed a new electrode such as precious metal ceramic electrode. Although SOFC single battery comprehensive performance indicators in our country are currently synchronized with the international advanced technology level, the new precious metal ceramic electrode has not been tested for long-term operation of the full battery. In order to analyze the practicality of the new noble metal ceramic electrode, especially whether the noble metal electrode is one of the factors that cause performance degradation, this paper studies whether the noble metal Pd electrode would diffuse into the YSZ electrolyte during the energization process. The composition and morphology of the electrolytes of 350h half-cell was analyzed by the battery polarization test, SEM, EDX and Electron etching depth analysis of XPS. The result shows that the noble metal Pd element has diffused more than 100 nm into the YSZ electrolyte after 350h constant current.
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Falsig, Hanne, Thomas Bligaard, Claus H. Christensen, and Jens K. Nørskov. "Direct NO decomposition over stepped transition-metal surfaces." Pure and Applied Chemistry 79, no. 11 (January 1, 2007): 1895–903. http://dx.doi.org/10.1351/pac200779111895.
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We establish the full potential energy diagram for the direct NO decomposition reaction over stepped transition-metal surfaces by combining a database of adsorption energies on stepped metal surfaces with known Brønsted-Evans-Polanyi (BEP) relations for the activation barriers of dissociation of diatomic molecules over stepped transition- and noble-metal surfaces. The potential energy diagram directly points to why Pd and Pt are the best direct NO decomposition catalysts among the 3d, 4d, and 5d metals. We analyze the NO decomposition reaction in terms of a Sabatier-Gibbs-type analysis, and we demonstrate that this type of analysis yields results that to within a surprisingly small margin of error are directly proportional to the measured direct NO decomposition over Ru, Rh, Pt, Pd, Ag, and Au. We suggest that Pd, which is a better catalyst than Pt under the employed reaction conditions, is a better catalyst only because it binds O slightly weaker compared to N than the other metals in the study.