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1
Torres, Urquidy Oscar Hernando. "Copper Resistant Bacteria Better Tolerate Commercially Available Antimicrobial Treatments Based in Silver and Silver-Copper Ions." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202734.
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In the current study, the antibacterial efficacy of zeolites containing silver or copper ions or a combination of these metals was assessed against several diverse copper resistant (CuR) and copper sensitive (CuS) strains of clinically relevant bacterial species. CuR Pseudomonas putida was significantly reduced in comparison to the unamended zeolite control. Unexpectedly, a CuS P. putida strain with no reported metal resistance appeared to be more resistant to the zeolite containing either Ag or Ag/Cu than the CuR strain. Contrary to expectations, after three and six hours of exposure, the CuS Escherichia coli displayed significantly more resistance to the Ag/Cu and Cu treatments than the reportedly CuR E. coli. All three reportedly CuR strains of Salmonella enterica exhibited resistance to Cu and Ag, as well as to the combination of the two metals after three and six hours of exposure. The reductions observed after 24 hours for all three CuR strains with Cu alone were still statistically significant compared to that of the CuS S. enterica strain. In addition, two of the CuR strains were more resistant to silver after 24 hours of exposure, suggesting a shared resistance mechanism such a copper efflux pump that also removes silver ions from the cell. Both the CuR and CuS strains of E. faecium were highly resistant to all of the treatments. In general, after comparison of all the resistances with all the treatments, E. faecium was the most resistant species, P. putida was the least resistant species, and the Salmonella strains were more resistant than E. coli in most cases.
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Speed, David John. "Symmetry in copper and silver cryptates." Thesis, Open University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252338.
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The cryptand ligands imBT (l,4,7,10,13,16,21,24-0ctaaza-bicyclo[8.8.8]hexacosa- 4,6,13,15,21,23-hexaene) and amBT (1,4,7,10,13,16,21 ,24-0ctaazabicyc10[ 8.8.8]hexacosane) form interesting disilver(I) and trisilver(I) cryptates, as well as a dicopper(I) and a well studied average valence dicopper(1.5) cryptate. Detailed structural and spectroscopic studies of the silver cryptates show that complex equilibria exist in solution, and the trisilver form appears to be thermodynamically favoured, the additional stabilisation apparently being due to argentophilic interactions. An optically pure form of the dicopper(I) imBT cryptate was successfully obtained, and is undergoing X-ray diffraction studies aimed at determining whether a copper-copper interaction exists, by direct examination of the electron density. Synthetic studies aimed at introducing substitution to the imBT and amBT ligands were complicated by competing reactions. A strategy to modify cryptand cavity size by incorporating asymmetric tetraamine caps succeeded, yielding dicopper(I) and disilver(I) cryptates with properties intermediate between cryptates incorporating the related symmetric caps. Manganese(II) cryptates of imBT and amBT were investigated as potential MRl contrast agents, the iminocryptate showing surprisingly high relaxivity, despite the fact that no water molecules were located in the crystal structure. The observation of high mass peaks in the FAB mass spectra ofimBT and amBT cryptates suggests the presence of 6+4 Schiff base condensation products, as well as the more abundant 3+2 products. It has not proved possible to isolate these molecules as yet, however initial studies aimed at a rational synthesis of the 6+4 condensation products were made, as these ligands could be of great interest for modelling the recently reported CUz site.
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Westlake, Michael Angelo 1966. "The oxidation of copper and silver plated copper lead frames." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278279.
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The effects of thin silver films (15-210 angstroms) on the oxidation of copper alloy lead frames has been characterized. Silver films were deposited onto copper lead frames by immersion plating in a bath containing potassium silver cyanide, potassium cyanide, and a mercaptan inhibitor. The thickness of films was measured by microfocus x-ray fluorescence and cross-checked by Rutherford backscattering spectrometry. Lead frames coated with silver films were oxidized at 150 to 200°C in a controlled humidity oven. The amount of oxide formed was measured by an electrolytic reduction technique and cross-checked with weight gain measurements. Auger, ESCA, and SEM analysis were also performed on the films. A tape test was performed to obtain qualitative information on the adhesion of the films.
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Botez, Cristian E. "Synchrotron x-ray scattering studies of metallic surfaces /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3052151.
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Mardani, Shabnam. "Copper and Silver Metallization for High Temperature Applications." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-300796.
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High-temperature electrical- and morphological-stability of interconnect is critical for electronic systems based on wide band gap (WBG) semiconductors. In this context, the thermal stability of both Ag and Cu films with Ta and TaN films as diffusion barriers and/or surface-capping layers at high temperatures up to 800 oC is investigated in this thesis. The investigation of un-capped Ag films with either Ta or TaN diffusion barrier layers shows electrical stability upon annealing up to 600 °C. Degradation occurs above 600 °C mainly as a result of void formation and Ag agglomeration. Sandwiching Ag films between Ta and/or TaN layers is found to electrically and morphologically stabilize the Ag metallization up to 800 °C. The barrier layer plays a key role; the β-to-α phase transition in the underlying Ta barrier layer is identified as the major cause for the morphological instability of the film above 600 °C. This phase transition can be avoided using a stacked Ta/TaN barrier. Furthermore, no observable Ta diffusion in Ag films is found. Copper films with a Ta diffusion barrier show clearly different behaviors. In the Cu/Ta sample, Ta starts to diffuse up to the surface via fast-diffusing grain boundaries (GBs) after annealing at 500 °C. The activation energy for the GB diffusion is 1.0+0.3 eV. Un-capped Cu is electrically stable up to 800 °C. An appreciable increase in sheet resistance occurs above 600 °C for the asymmetric combinations Ta/Cu/TaN and TaN/Cu/Ta. This degradation is closely related to a substantial diffusion of Ta across the Cu film and on to the TaN layer, where Ta1+xN forms. The symmetrical combinations Ta/Cu/Ta and TaN/Cu/TaN show only small changes in sheet resistance even after annealing at 800 °C. No Ta diffusion can be found in the Ta/Cu/Ta and TaN/Cu/TaN stacks. Finally, the influence of barrier and cap, their interfaces to Cu and Ta diffusion and segregation in the Cu GBs on electromigration is studied. Our preliminary results with the TaN/Cu/Ta and TaN/Cu/TaN structures report a 2-fold higher activation energy and a 10-fold longer lifetime for the former, thus confirming an important role of the interface between Cu and the cap and/or barrier.
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馮潔媚 and Kit-mai Wendy Fung. "Luminescent polynuclear copper(I) and silver(I) complexes of bridging acetylides and related studies on copper(I) thiolates." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B3123687X.
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Fung, Kit-mai Wendy. "Luminescent polynuclear copper(I) and silver(I) complexes of bridging acetylides and related studies on copper(I) thiolates /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19102665.
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Lamontagne, Marc Philip. "The effect of impurities on the distribution of silver between copper and copper selenide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20567.pdf.
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Schwaiger, Ruth. "Fatigue behavior of sub-micron silver and copper films." Stuttgart : Max-Planck-Inst. für Metallforschung, 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964216345.
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Schwaiger, Ruth. "Fatigue behavior of sub-micron silver and copper films." [S.l. : s.n.], 2001. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9803839.
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Davis, Harrison Olivia. "Copper, Silver, and Gold Clusters: A Synthetic and Structural Investigation." Kent State University Honors College / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1557352298361181.
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Barritt, Elizabeth. "The silver, copper and silicon (110) surfaces in ambient environments." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/12795/.
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The results presented in this thesis were part of a research programme that utilised the surface sensitive technique reflection anisotropy spectroscopy (RAS) to study the silver, copper and silicon (110) surfaces under ambient conditions. It has been shown that although the preparation of these surfaces can be less precise in ambient conditions, than when prepared in an ultra high vacuum (UHV) environment, the main features observed are similar. The features observed in the RA spectrum for the Si(110) surface in ambient conditions show good agreement with previous data performed in a UHV environment. The experiments performed using the Ag(110) surface show that when the Ag(110) crystal is heated to higher temperatures, when the oxide present will have dissociated off the surface, the ambient RA spectrum shows good agreement with experiments performed in UHV. However, the transition between surface states observed in UHV was not seen in the RA spectrum in ambient conditions. These experiments were performed using the Re(∆r/r) part of the RA spectra. However, to examine the surfaces further the Im(∆r/r) part of the RA spectra was also presented along with the azimuthal dependence of the RA spectrum. The Cu(110) surface was investigated under ambient conditions and electrochemically. It was found the surface is not stable in ambient conditions but can be stabilised electrochemically using HCl. The adsorption and desorption of Cl- was studied and the research focused on when the Cl- was desorbed from the surface leaving clean Cu(110). Under these conditions the transition between surface states at 2.10 eV in UHV was observed at a slightly higher energy of 2.20 eV in an electrochemical environment.
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Mat-Zain, Norashikin. "Development of antimicrobial fabrics based on silver and copper nanoparticles." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/16611.
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With growing public unease surrounding the extent of microbial infections, there is a demand for antimicrobial materials including antimicrobial textiles. Nanotechnology has provided new solutions for the development of antimicrobial fabrics. In this study, nanoparticles of silver (Ag) and copper (Cu) and alloy nanoparticles of Ag and Cu (Ag/Cu) have been synthesized by reduction of their respective nitrates by ascorbic acid, using chitosan as a stabilising agent and microwave heating. UV-vis spectrophotometry indicated the presence of the alloy by a single peak (500 nm) for Ag/Cu nanoparticles, whereas mixtures of Ag and Cu nanoparticles (Ag+Cu) showed two peaks of 420 and 500 nm, corresponding to pure Ag and Cu nanoparticles respectively. Particle size is increased by increasing nitrate concentration and reducing the chitosan concentration. Surface zeta potentials were positive for all the nanoparticles and varied from +27.8 to +33.8 mV. Ag and Cu nanoparticles were shown to be spherical whilst the alloy nanoparticles had an irregular shape. Cu nanoparticles resulted in higher inactivation of bacteria such as Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) than did Ag nanoparticles at the same concentration. The effect was reversed when tested on nanoparticles of the same mean particle size with Ag nanoparticles emerging as more effective. Bacterial inactivation increased with concentration of chitosan and the metal concentration. The nanoparticles showed a more potent antibacterial effect than did ions of the same metal. B. subtilis was more susceptible than E. coli which may be due to the differences in their cell walls structure. MRSA proved harder to inactivate than both B. subtilis and E. coli under identical conditions. Antifungal activity was significantly affected by the types of nanoparticles employed. Ag nanoparticles displayed higher inactivation than Cu ones. Alloyed nanoparticles demonstrated the highest inactivation against both bacteria and fungi. This constitutes clear evidence of an antimicrobial synergy between the Ag and Cu. Bacteria and fungi in contact with nanoparticle-impregnated fabrics were revealed by FEGSEM to have taken on a shrunken appearance. Nanoparticle-impregnated fabrics reduced microbial viability by 80-90%, but this decreased in relation to the number of washes the fabric was subjected to and indicated a leached out of the nanoparticles. Pre-treatment of cotton fabrics with tannic acid and citric acid enhanced the durability of the antimicrobial effect when washed and this increased with concentration of the acid. Citric acid treated fabrics showed higher durability than tannic acid treated fabrics. Log reductions of Trichophyton interdigitale (T. interdigitale) were lower than those for B. subtilis, E. coli and MRSA at the same test conditions. The combination of nanoparticles with the antifungal drug fluconazole proved effective and reduced the time necessary to eliminate the T. interdigitale than either nanoparticles or fluconazole alone.
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李丹 and Dan Li. "Synthesis, structure and photophysical and photochemical properties ofpolynuclear copper (1), silver (1) and gold (1) complexes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31233120.
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Li, Dan. "Synthesis, structure and photophysical and photochemical properties of polynuclear copper (1), silver (1) and gold (1) complexes /." [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13385367.
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Choi, Tae-Seop. "Copper, silver, and gold etching with H₂ and CH₄ based plasmas." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53043.
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This thesis describes investigations on Cu, Ag, and Au subtractive etching by H₂ and CH₄ plasmas below room temperature. Both blanket film of Cu, Ag, and Au etching and patterning studies were performed for the applications of these metals as interconnects in electronic devices and photonic devices to replace current Damascene process. The nm scale Cu patterning in H₂ plasma was demonstrated by etching Ta/Cu/Ta stacks. Also, Ag and Au etching was feasible in H₂ plasma unlike other transition metals such as Ti, Ta, Ni, Cr, Al, and Pt indicating the etching chemistry based on the similar electronic structures of group 11 metals plays important role. In addition, employing CH₄ plasma allowed the use of photoresist mask and patterned Cu, Ag, and Au with high selectivity. The overall etch mechanism is the combination of chemical reactions and physical (photon and ion) bombardment in H₂ and CH₄ plasma. However, the Cu etching mechanism is more dependent on the chemistry while Ag and Au patterning were dominated by physical bombardment. Finally, the direction for future work including further mechanistic study and process optimization is suggested.
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Kim, Jeha. "Structural and elastic properties of silver-palladium and copper-palladium superlattices." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186275.
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I prepared Ag/Pd and Cu/Pd superlattices using both sputtering and molecular beam epitaxy. For the Ag/Pd (t(Ag):t(Pd) = 1:1) superlattices, I observed two distinctive behaviors in the structural coherence length ξ as a function of modulation wavelength Λ. Using Brillouin light scattering (BLS) I observed a 50% enhancement of the shear elastic constant c₅₅ and a 16% increase of c₁₁ with decreasing Λ. Annealing study showed that a high structural order of the films in the growth direction was strongly correlated to the increase of c₅₅. For the 3:1 and 1:3 Ag/Pd samples, I also observed a monotonic increase of the Rayleigh velocity υ(R) (or c₅₅) with decreasing Λ and similar behavior in the structural coherence length to the 1:1 samples. In conclusion, the recrystallization of the alloy and the formation of extended interfaces by intermixing at the Ag-Pd interfaces are responsible for a large enhancement of c₅₅. Using BLS for the Cu/Pd superlattices, I observed a 24% decrease of c₅₅ as Λ was decreased to ∼30-40 Å, followed by a rapid increase for smaller Λ. The observed homogeneous strain in the growth direction showed a strong relationship with c₅₅. The strain was localized at the interface and the Cu/Pd films were in compressive stress for Λ < 38 Å. In conclusion, a localized strain at the interfaces in Cu/Pd is related to the softening in c₅₅. The measurements of in-plane lattice spacing d[220] indicated a structural transformation of the films at Λ = 14 Å from an incoherent to a coherent structure. However, the in-plane strain did not show any relationship with the softening of c₅₅. For single crystalline Cu/Pd superlattices, well-defined RHEED streaks showed incommensurate growth of Cu(111) on Pd(111) layer. The measured shear elastic constant c₅₅ showed a 26% decrease with respect to the largest Λ film with a peak at Λ ≃ 40 Å. Unlike the sputtered films, while c₅₅ decreases by 26% with decreasing Λ, the Cu/Pd films show no change in d(avg)[111] for Λ > 40 Å. I observed no in-plane anisotropies in υ(R) as predicted from theory for single crystal films.
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Chiou, Ipeng 1957. "Inactivation of Listeria monocytogenes by copper, silver ions and free chlorine." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277992.
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The antibacterial effect of electrolytically generated copper and silver separately and combined with free chlorine on Listeria monocytogenes was evaluated in filtered well water (FWW) and autoclaved dairy process water (ADPW). The inactivation rate (k = log10 reduction/minute) was determined. Slow bactericidal effects were observed in both FWW and ADPW after exposure to 400:40 or 800:80 mug/L copper and silver compared to 0.15 mg/L chlorine. At least five hours of exposure was required for a 6 log10 reduction in the bacterial numbers with copper and silver; however, with chlorine, the exposure time was reduced to less than one minute for the FWW. Addition of 0.15 mg/L chlorine to water containing copper and silver resulted in a significantly enhanced inactivation rate as compared to chlorine alone in both FWW and ADPW. In ADPW, chlorine with copper (400, 800 mug/L) resulted in an increased k value compared to chlorine alone and copper alone.
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Brooks, Neil Richard. "Supramolecular synthesis of copper(I) and silver(I) co-ordination polymers." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342003.
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Black, Jane R. "Group 15 and 16 donor ligand complexes of copper and silver." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307087.
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Leke, Luter. "Methanol oxidation over copper and silver monometallic and bimetallic supported catalysts." Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=227099.
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The partial oxidation of methanol to formaldehyde with air as oxidant has been studied with supported monometallic and bimetallic catalysts of copper and silver over a range of temperature and contact times. This was done to investigate the influence the bimetallics could possibly have on either the reaction pathways and/or the product(s) selectivity of the oxidation of methanol. Characterisation of these catalysts was performed by nitrogen adsorption and porosity measurements, XRD, and IR spectroscopy of adsorbed methanol and of adsorbed CO. These results indicated no crystalline phases of the loaded metals to be present. CO adsorption showed the presence of small cluster metal atoms on the surface of the catalysts. The reduction peaks from TPR also revealed the presence of partially oxidised and dispersed metal atoms. Infra-red studies of methanol adsorbed on these sample catalysts revealed the presence of intermediate methoxy and formate species which are believed to be formed in the course of the reactions. Results showed the monometallic copper and silver catalyst to be more active than the bimetallics. Although formaldehyde selectivities and yields were generally low, they were highest for the bimetallics supported on the silica catalyst than the monometalics and alumina supported samples. Copper-silver interaction in the bimetallic was proposed to enhance the reduction of the silver that enhanced the selectivity to formaldehyde. In particular under conditions, low conversions of methanol saw highest selectivities to formaldehyde. There was also a pronounced effect of the supports on product distribution and activities with the alumina based samples being more active than the silica supported ones, with the product distributions on the alumina supported significantly showing high yields of DME while the silica showed high yield for methyl formate with COx and CH4 detected in small quantities on all the catalysts within the parameters investigated.
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Nate, Zondi. "Green synthesis of copper and silver nanoparticles and their antimicrobial activity." Thesis, Vaal University of Technology, 2018. http://hdl.handle.net/10352/424.
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M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of TechnologyThe present study includes the use of a green synthetic method to prepare copper and silver nanoparticles using chitosan, aqueous extracts of Camellia sinensis, Combretum molle and Melia azedarach linn leaves. This study aims to investigate the influence of capping and precursor concentration on the properties of silver nanoparticles with emphasis on the medicinal plants chosen. The effect of capping agent on the properties of copper nanoparticles is also investigated. The phytochemical properties of plant extracts and the antimicrobial activity of the synthesized particles were also studied; this was achieved by using microdilution bioassay. Decoction method was used to extract secondary metabolites from plant leaves. Preliminary phytochemical screening carried out on the aqueous extracts of the plant leaves showed the presence of tannins, proteins, flavonoids, phenols, and carbohydrates. The total phenolic and flavonoids content of the aqueous extract was determined using spectroscopic methods. The highest phenolic content was found in the aqueous extract of Combretum molle (135 mg/g), and the highest flavonoid content was found in the aqueous extract of Camellia sinensis (0.4 mg/g). Characterization was done by a combination of spectroscopic, microscopy and XRD techniques. Both the size and shape of the synthesized silver nanoparticles were dependent on the identity of the capping molecule, precursor and capping agent concentration as depicted from their TEM and XRD results. Silver nanoparticles were found to be predominantly spherical. The capping agent concentration was also found to influence the degree of agglomeration, with an increase in capping agent concentration giving lesser agglomeration. FTIR spectral analysis showed that silver nanoparticles interact with bioactive compounds found in the plants through the hydroxyl functional group. Other shapes including diamond were observed for the effect of precursor concentration. The XRD micrographs revealed a face-centered cubic geometry and the phase remained the same with an increase in precursor concentration. The synthesized silver nanoparticles were all blue shifted compared to the bulk material. The TEM results revealed that copper nanoparticles with different sizes and shapes were successfully synthesized. All the prepared copper and silver nanoparticles showed satisfactory antifungal and antibacterial activity against Candida albicans, Cryptococcus neoformans, Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumonia and Pseudomonas aeruginosa. The capping molecules used in this study also showed some antibacterial and antifungal activity against the selected strains. However nanoparticles performed better than these capping molecules. Both silver and copper nanoparticles were found to be more active against gram-negative bacteria compared to gram-positive bacteria. Amongst all the prepared silver nanoparticles Combretum molle capped nanoparticles were found to be the most active nanoparticles. Also with copper nanoparticles, it was found that Combretum molle capped nanoparticles were the most active nanoparticles. Between the two metal nanoparticles, silver nanoparticles showed high antibacterial and antifungal activity compared to copper nanoparticles. The antioxidant activity of silver nanoparticles was assessed using 2.2-diphenyl-1-picrylhydrazyl. Silver nanoparticles were found to have some antioxidant activity. However, the capping molecules were found to be more active than the synthesized nanoparticles. This observation is attributed to the presence of some bioactive compounds in the plant extracts.
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Brancho, Jennie. "Review of Regulatory Policies for Copper and Silver Water Quality Criteria." Kent State University Honors College / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1493904025463972.
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Landeen, Lee Kevin 1965. "Inactivation of Legionella pneumophila by copper-silver ions and free chlorine." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276997.
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Water disinfection systems utilizing electrolytically generated copper:silver ions (200:20 to 400:40 ug/L) and low levels of free chlorine (0.1 to 0.4 mg/L) were evaluated at room (21-23°C) and elevated (39-40°C) temperatures in filtered well water (pH 7.3) for their efficacy in inactivating Legionella pneumophila (ATCC 33155). A contact time of 24 hr was necessary for copper:silver (400:40 ug/L) to achieve a 3 log₁₀ reduction in bacterial numbers at room temperature. As the copper:silver concentration increased to 800:80 ug/L (K = 7.50 x 10⁻³ log₁₀ reduction/min), the inactivation rate significantly (p ≤ 0.05) increased. In water systems at room temperature with and without copper:silver (400:40 ug/L), the inactivation rates significantly increased as the free chlorine concentration increased from 0.1 mg/L (K = 0.397 log₁₀ reduction/min) to 0.4 mg/L (K = 1.047 log₁₀ reduction/min). All disinfection systems, regardless of temperature or free chlorine concentration, showed increased inactivation rates when 400:40 ug/L copper:silver was added; however, this trend was significant only at 0.4 mg/L free chlorine.
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Athavale, Saurabh. "Effect of Cu concentration and cooling rate on microstructure of Sn-3.9Ag-XCu." Diss., Online access via UMI:, 2006.
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Pardoe, Andrea. "Photochemical Synthesis of Mono and Bimetallic Nanoparticles and Their Use in Catalysis." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19951.
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Nanomaterials have become a popular topic of research over the years because of their many important applications. It can be a challenge to stabilize the particles at a nanometer size, while having control over their surface features.
Copper nanoparticles were synthesized photochemically using a photogenerated radical allowing spatial and temporal control over their formation. The synthesis was affected by the stabilizers used, which changed the size, dispersity, rate of formation, and oxidation rate. Copper nanoparticles suffer from their fast oxidation in air, so copper-silver bimetallic nanoparticles were synthesized in attempts to overcome the oxidation of copper nanoparticles. Bimetallic nanoparticles were synthesized, but preventing the oxidation of the copper nanoparticles proved difficult.
One important application of nanoparticles that was explored here is in catalyzing organic reactions. Because of the fast oxidation of copper nanoparticles, silver nanoparticles were synthesized photochemically on different supports including TiO2 and hydrotalcite (HTC). Their catalytic efficiency was tested using alcohol oxidations. Different silver nanoparticle shapes (decahedra and plates) were compared with the spheres to see the different catalytic efficiencies.
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Lam, Chi-ho Aaron. "Syntheses, characterization and photophysics of polynuclear copper (I) and silver (I) complexes containing monoynyl, diynyl and chalcogen-type ligands /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22055034.
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Bedford, Birgitta. "Legionella control in water systems using copper and silver ion generation systems." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7983.
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Legionella can cause human disease which can be fatal. Routine monitoring for Legionella in water systems is not recommended by UK authorities. Evidence of the efficacy of control modalities against Legionella in these water systems is, therefore, not available. Although studies have been conducted with copper and silver ionization on its efficacy against Legionella and on its value in reducing hospital-acquired legionellosis, little evidence of its efficacy is available from routine monitoring data. This study demonstrates the efficacy of copper and silver ionization against Legionella in water systems of 10 hospitals from data obtained from routine monitoring for Legionella, copper and silver. The inefficiencies of maintaining temperatures above 50ºC at hot outlets and below 20ºC at cold outlets, as recommended by UK authorities for controlling Legionella in water systems, is also demonstrated from the data obtained from routine monitoring for Legionella and temperatures. The futility of maintaining hot temperatures above 50ºC and then to reduce them to temperatures that do not present a risk of scalding is also demonstrated from the data obtained. This efficacy of copper and silver ionization and inefficiency of maintaining temperatures at 50ºC against Legionella was demonstrated as well in novel model rigs, built to simulate a typical water system of a small hospital, by data obtained from Legionella, copper, and silver analysis, and temperature recordings. The differences in biofilm formation and Legionella growth on the surfaces of copper, polyethylene, and synthetic rubber, which are commonly used plumbing materials, were also examined in the model rigs as well as with a Robbins device. These studies indicated that copper is not as biocidal as previously reported in other studies, and gave similar results to polyethylene, which previously been shown to promote biofilm development. Synthetic rubber, however, showed to promote biofilm production and should not be used as a plumbing material.
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Xu, Yi-Jun. "Selective oxidation of hydrocarbons using supported gold, silver, copper and bimetallic catalysts." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/54322/.
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Supported gold catalysts can provide tuneable activity for liquid phase selective oxidation of alkenes, in particular cyclohexene and cis-cyclooctene, using molecular oxygen from air under mild conditions. Selective oxidation can be readily kick-started using a nano-crystalline gold catalyst supported on carbon along with a small amount of TBHP as initiator. Extremely high selectivity, ca. 98%, for partial oxidation products with significant conversion has been obtained using a bismuth-modified gold catalyst for selective oxidation of cyclohexene. In the case of cis-cyclooctene oxidation, high selectivity to partial oxidation products has also been achieved at a high rate of reaction, without the use of solvent, which is a major tenet of green chemistry. Gold catalysts are also active for the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone. The gas-phase epoxidation of propene to propene epoxide (PO) has been studied using only molecular oxygen as oxidant over a series of supported Ag, Cu, Au and bimetallic (Au-Cu, Cu-Ag and Au-Ag) catalysts. It has been found that the support has an important effect on the catalyst performance. A Au-Cu catalyst exhibited very high selectivity to PO, ca. 96%, at a propene conversion, ca. 0.14%, at relatively low temperature, 200 C. The intrinsic instability of PO leads to the observation of high selectivity to PO only at low temperature.
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Sansom, H. C. "Copper and silver bismuth iodide semiconductors as potential solar cell absorber materials." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3028034/.
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Robinson, Donald A. III. "Synthesis and Characterization of Metal Nanoclusters Stabilized by Dithiolates." Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/chemistry_theses/44.
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Rapidly expanding research in nanotechnology has led to exciting progress in a versatile array of applications from medical diagnostics to photocatalytic fuel cells. Such success is due to the ability of researchers to manipulate the desired properties of nanomaterials by controlling their size, shape, and composition. Among the most thriving areas of nanoparticle research has been the synthesis and characterization of stable metallic nanoclusters capped by thiolate ligands. Our group has extended this research to study copper, silver, and gold clusters with remarkable stability and energetics, which was achieved by using dithiolates as the ligand stabilizers. In addition to the enhanced stability offered by the chelate effect, the use of dithiolate ligands instead of monothiolates is proposed to provide an alternate interfacial bond structure that is shown to strongly influence energetic properties of nanoclusters, with strong evidence of metal-ligand charge transfer. Energetic properties were characterized by spectroscopic and electrochemical methods.
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Sicairos, Ruelas Enue Erdemely. "The Development of Alternative Methods of Disinfection." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194751.
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Chlorine is the primary method for disinfection of drinking water in the United States; however, growing concerns about the potential hazards associated with carcinogenic chlorine disinfection by-products have resulted in increased efforts to develop alternative methods of water disinfection. In addition, it is sometimes difficult to maintain an adequate concentration of free chlorine throughout a drinking water distribution system due to intrusion events and the presence of biofilms.Silver and copper are widely used as environmental biocides and as clinical antimicrobial agents. Copper has been extensively used as an algaecide for many years, and is reported to be one of the most toxic metals to heterotrophic bacteria in aquatic environments. In this study, silver and copper, both individually and in combination, were able to significantly reduce the numbers of the bacterial pathogens Salmonella typhimurium, Escherichia coli, Listeria monocytogenes, and Mycobacterium fortuitum in aqueous solutions. Silver and copper together could potentially be used as a secondary disinfectant in water treatment because their residual effect is long lasting and no harmful byproducts are generated.Besides water, produce can also be a source of microbial pathogens. Fruits and vegetables are the third leading source in microbial foodborne outbreaks, accounting for more than 10,000 cases of foodborne illness in the U.S. between 1990 and 2001. Alternative produce sanitizers in addition to chlorine were evaluated against foodborne pathogens inoculated onto lettuce. Overall, Fit® (citric acid, grapefruit oil extract) and chlorine yielded the greatest reductions of the study organisms.A large number of compounds are available for use as disinfectants; however, some are highly toxic, corrosive and produce harmful by-products. Natural antimicrobial products are another possible alternative. The efficacy of a natural peptide-based antimicrobial, Absolute Fx, was assessed against bacteria and viruses. Absolute Fx effectively inactivated the study organisms.
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Wilson, Nicholas Thomas. "The structure and dynamics of noble metal clusters." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368419.
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Murrell-Mottram empirical atomistic many-body and Gupta n-body potentials have been used to study various aspects of the cluster chemistry of copper, silver, gold and nickel. Simulated annealing techniques have been used to search for the global minima of the four metals with up to 55 atoms. Icosahedral, decahedral, octahedral, hexagonal closed packed and hexagonal prismatic structures were found. The gold clusters show some rearrangements and distortions from ideal geometries. Polyhedral cluster calculations up to 1 500 atoms predict that icosahedra and truncated octahedra are particularly stable. Calculations on the structures of copper-gold alloy clusters show that gold atoms prefer to occupy the surface of the cluster. A simple approximation to model the passivation of gold clusters by thiol ligands predicts that for 55 atoms the passivated cuboctahedron is more stable than the icosahedron, the reverse of the order for the bare clusters. Molecular dynamics simulations of gold adatoms on the gold (111) surface and of the impact of a 55 atom gold cluster with the gold (111) surface have been performed.
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Milligan, Peter K. "The effects of substituents and coverage on the bonding of thiophene to Cu(111)." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326055.
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Chan, Chi-keung. "Structure, photophysical and theoretical studies of polynuclear CU(I), AG(I) and AU(I) metal complexes /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18037422.
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Atluri, Vasudeva Prasad 1959. "Recovery of gold and silver from ammoniacal thiosulfate solutions containing copper by resin ion exchange method." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276566.
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This research was undertaken to study the suitable physico-chemical conditions for the selective recovery of gold and silver from simulated thiosulfate leach liquors containing copper, gold or silver, ammonia and thiosulfate using three anion exchange resins. In particular, the effect of chemical variables such as thiosulfate, cupric ion and ammonia concentrations and the solution potential of the system on the batch loading of silver and gold onto the resins have been investigated in detail. Pourbaix diagrams have been constructed to understand the stability of this complex system under various Eh and pH conditions. The experimental results indicate that IRA-400 resin has the highest capacity for both silver and gold compared to IRA-68 and IRA-94. All the three resins investigated are not selective to silver and gold over copper. The elution studies using ammonium thiosulfate solutions have revealed that selective elution of silver from copper is not possible, while some selectivity can be achieved between gold and copper. (Abstract shortened with permission of author.)
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Ay, Hale. "Single And Multicomponent Ion Exchange Of Silver, Zinc And Copper On Zeolite 4a." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609882/index.pdf.
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Ion exchange of heavy metals with zeolites is important in terms of different application areas. Industrial wastewater treatment and antibacterial applications are two essential areas that have taken great attention. While silver, zinc and copper are well known for their toxicity, they are also used as antibacterial agents in zeolites.
The objective of this study is to investigate the single and multicomponent ion exchange behavior of zeolite 4A for silver, zinc, copper and sodium ions. For this purpose Ag+-Na+, Zn2+-Na+, Cu2+-Na+ binary systems and Ag+-Zn2+-Na+, Ag+-Cu2+-Na+, Cu2+-Zn2+-Na+ ternary systems were investigated in batch systems at 25°C and 0.1 N. Binary ion exchange isotherms indicate that zeolite 4A has high selectivity for silver, zinc and copper with respect to sodium. All exchange isotherms lie above the diagonal over the whole range. Using the equilibrium data, the thermodynamic analysis of the binary systems were carried out. The thermodynamic equilibrium constants and the standard free energies of exchange were calculated as 340.9 and -14.5 kJ/mol for silver-sodium system, 40.5 and -4.6 kJ/mol for zinc-sodium system, and 161.2 and -6.3 kJ/mol for copper-sodium system, respectively. From these values, selectivity sequence of zeolite 4A was determined as Ag+ >
Cu2+ >
Zn2+. This selectivity sequence was also verified by the results of ternary ion exchange experiments. The experimental data were compared with the Langmuir and Freundlich isotherms. While Freundlich model gives a better correlation for Ag+-Na+ and Zn2+-Na+ exchange, Langmuir model represents a better fit to the experimental data of Cu2+-Na+ exchange.
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Anson, Scott J. "Analysis of lead free tin-silver-copper and tin-lead solder wetting reactions." Diss., Online access via UMI:, 2007.
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Ingram, Jani Cheri. "Surface-enhanced Raman scattering and electron spectroscopic studies of copper and silver surfaces." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185153.
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The overall goal of this research is to investigate the enhancement mechanisms associated with the surface enhanced Raman scattering (SERS) phenomenon. The approach taken in these investigations is to directly compare the SERS abilities of Cu and Ag surfaces using both SERS and electron spectroscopy. One set of experiments has been directed toward studying the contribution of the charge transfer (CT) mechanism to the SERS of pyridine adsorbed on Cu and Ag electrodes. These studies involve modifying the electrodes by depositing submonolayer amounts of Pb which serves to quench the SERS. By using a variety of excitation energies, the resulting quenching profiles track the CT process. Additionally, other electrochemical/SERS experiments have been pursued in order to probe the contribution of the CT mechanism. The second set of experiments involved measuring the optical properties of the Pb-modified Cu and Ag surfaces using electron energy loss spectroscopy in the reflection mode (REELS). Based on electromagnetic (EM) theory, the enhancement is, to a rough approximation, indirectly proportional to ε₂, the imaginary part of the dielectric constant. Thus, the goal of these studies is to determine the changes in ε₂ as a function of Pb coverage in order to determine the contribution of the EM mechanism to the SERS quenching profile. It was necessary to develop a method to determine optical constants from REELS data. A number of pure metals (Al, Cu, Ag, Au, Ti, V, Fe, Co, and Ni) were chosen to test the method. In all cases, our results compare well to the literature values with a relative standard deviation of 20% or less. Having established the method, the next step was to apply it to the Pb-modified Cu and Ag surfaces. Due to instrumental limitations, only semi-quantitative optical constants could be determined. From these values, it was found that the relative changes in the ε₂ values were larger for submonolayer coverages of Pb on Ag compared to Cu. The EM enhancements determined from these results did not predict the SERS-quenching behavior suggesting that other mechanisms must be considered.
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Attard, G. A. "The structure and reactivity of copper, silver and gold overlayers on W(100)." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382046.
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Luo, Rong. "An electrochemical study of the oxidative dissolution of synthetic copper-silver-selenide minerals in aqueous media." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278424.
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Benedict, Michael Scott. "Heterogeneous nucleation of Sn in Sn-Ag-Cu solder joints." Diss., Online access via UMI:, 2007.
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Fee, Michele. "Electrochemical Investigation of Thin Nickel, Copper and Silver Films Interfaced with Yttria-Stabilized Zirconia." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24360.
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The electrochemical investigation of nickel, copper and silver thin films interfaced with yttria stabilized zirconia (YSZ) solid electrolyte was accomplished to determine their response to polarization in dilute oxygen environments at 350 °C and assess their viability for electrochemical promotion of catalysis (EPOC). Polycrystalline YSZ (8 mol % Y2O3-ZrO2) pellets were synthesized in the lab and films deposited onto them using evaporative physical vapor deposition (PVD). The critical thickness of copper, silver and nickel thin films were foundusing in-situ resistance measurements. Following this, 50 and 100 nm copper and nickel films were studied using solid electrolyte cyclic voltammetry (SECV) to determine their response to polarization. Given that silver thin films at such thicknesses are thermally unstable, a film of 800 nm was used in this study. The materials were found to respond to polarization in different ways, forming oxides according to Wagner and Mott-Cabrera oxidation models.
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Roman, John W. (John William). "An investigation of low temperature transient liquid phase bonding of silver, gold, and copper." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13483.
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Liu, Xingguang. "Investigation of magnetron sputtered nitrogen-containing chromium coatings with additions of copper and silver." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/16338/.
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In the past two decades, research in the field of plasma-assisted Physical Vapour Deposition (PVD) has been intensively concentrated on hard and superhard coatings, particularly ceramic-ceramic and ceramic-metal nanocomposite film, in order to achieve improved tribological properties, such as wear resistance and low friction. However, sufficient (rather than extreme) high hardness, combined with low elastic modulus (high H/E ratio), often proves to be more effective again wear than (extreme) high hardness by itself, especially so for coatings on soft or compliant substrates. In addition, self-lubricating PVD tribological thin films have been intensively investigated in recent years. Among these, PVD nanocomposite coatings containing soft metals (e.g. Ag or Cu), as a solid lubrication phase, embedded in a hard wear-resistant matrix, such as a transition metal nitride, carbide, oxide or supersaturated solid solution, and mixtures of them (in ternary/quaternary/nanocomposite coating systems), have all been extensively studied, with the promise of improved tribological performance during transient and/or cyclic temperature changes. Therefore, a PVD coating with similar elastic modulus as soft or compliant metallic substrates (e.g. around 200 GPa or less), and promising solid-lubricating properties over a (relatively) large range of temperatures, would be of great application interest. This work concentrates on nanocomposite metallic (or partially metallic) PVD CrCuAgN coatings. The main aims of the study are to preserve the metallic state of Cr and, instead of creating stoichiometric ceramic nitride phases (CrN or Cr2N), to supersaturate it with interstitial nitrogen atoms, in order to obtain coatings with high H/E ratios. Moreover, the transport behaviour of solid lubricants (i.e. Cu and Ag) to coating surfaces under medium high temperature would also be important for the tribological and antimicrobial properties of these coatings. Guidelines of coating design for specific applications can be obtained by comprehensive study of the abovementioned studies. Coatings were produced by asymmetric pulsed-DC unbalanced magnetron sputtering, on AISI 316 stainless steel coupons. Then they were divided into three groups for post-coat annealing at different temperatures, which were as-deposited (no annealing), 300 °C and 500 °C, respectively, with a fixed annealing duration of 2 hours. The as-deposited and annealed coatings were then analysed and/or evaluated using X-ray diffraction (XRD) analysis, scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), high-resolution TEM and scanning TEM (STEM) with EDX, nanoindentation, scratch test, high-temperature reciprocating sliding wear test, in order to investigate the phase composition, chemical composition, surface and fracture morphologies, phase- and elemental distribution, mechanical properties and tribological properties, etc. The result show that, in coatings with a nitrogen concentrations of up to 16 at.% (i.e. N/(Cr+N) atomic ratio up to 0.18), a metallic Cr solid solution with supersaturated interstitial nitrogen was preserved, even after post-coat annealing at 300 °C and 500 °C. At relative higher N/(Cr+N) atomic ratios, the coexistent state of α-Cr solid solution with embedded Cr2N nitride phase is relatively stable over a large range of nitrogen concentrations (i.e. N/(Cr+N) ratios from 0.18 to 0.55 in this investigation), which can also survive at relatively high temperature (e.g. 500 °C). Nitrogen-free CrCuAg coatings exhibited relatively low hardness, ranging from 5 GPa to less than 10 GPa. With the introduction of nitrogen, the hardness of CrCuAgN coatings increased significantly, to ~15 GPa with a preserved metallic Cr solid solution matrix. And the tribological test results showed that, a significant decrease in the coefficients of friction, over 50% compared to that of the substrate (from 0.31 to 0.14 with diamond indenter, and from 0.83 to 0.40 with alumina ball, respectively) was obtained for the CrCuAgN coatings, showing effective solid lubricating behaviour. The co-existence of Cu in a PVD coating containing Ag was found to be beneficial to Ag transport onto the coating surface, resulting not from the preconceived ‘intergranular network channels’ of Cu, but from the much higher detachment (from small precipitates to larger ones) rate of Cu than Ag, which would ‘leave a path’ for Ag to transport after Cu. Therefore by proper design and processing, CrCuAgN coatings with appropriate elemental compositions and solid-solution matrix can be obtained, in which the precipitation rate of Ag can be (partially) controlled by a moderate concentration of Cu (4.5 at. % appears to be sufficient), resulting in a controlled supply of solid lubricants, hence being highly promising in the application fields of solid lubricating coatings.
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Almotawa, Ruaa Mohammed. "Silver(I) and Copper(I) Complexes from Homoleptic to Heteroleptic: Synthesis, Structure and Characterization." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404512/.
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A plethora of novel scientific phenomena and practical applications, such as solid-state molecular solar cells and other optoelectronic devices for energy harvesting and lighting technologies, have catalyzed us to synthesize novel compounds with tunable properties. Synthetic routes, single crystal structures, and spectral and materials properties are described. Reactions of Ag(I) and Cu(I) precursors with various types of ligands -- including the azolates, diimines, and diiphosphines -- lead to the corresponding complexes in high yield. Varying the metal ions, ligands, synthetic methods, solvents, and/or stoichiometric ratio can change the properties including the molecular geometry or packing structure, reactivity, photophysical and photochemical properties, semiconducting behavior, and/or porosity of the functional coordination polymers obtained. For solar cells purposes, the absorption energy can be extended from the ultraviolet (UV) region, through the entire visible (Vis) region, onto a significant portion of the near-infrared (NIR) portion of the solar spectrum with high absorption coefficients due to the infinite conjugation of Cu(I) with diimine ligands. Twenty-eight crystal structures were obtained by conventional crystal growth methods from organic solvents, whereas their bulk product syntheses also included "green chemistry" approaches that precluded the use of hazardous organic solvents. The resulting products are characterized by powder x-ray diffraction (PXRD), Fouriertransform infrared (FTIR), nuclear magnetic resonance (NMR), UV/Vis/NIR absorption/diffuse reflectance/photoluminescence spectroscopies, and thermogravimetric analysis (TGA). Regarding the scientific phenomena investigated, the highlighting work in this dissertation is the discovery of novel bonding/photophysical/optoelectronic properties of the following materials: a black absorber with absorption from 200- 900 nm, a very stable compound with a bright green luminescence obtained by a solventless reaction, and a novel coordination polymer showing uncommon interaction of Ag(I) with three different types of diimine ligands simultaneously.
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Lin, Yongyue, and 林勇躍. "Luminescent platinum(II), copper(I), silver(I) and zinc(II) complexes with functional pyridyl and arylacetylide ligands: structures, spectroscopic properties and applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31243381.
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林智豪 and Chi-ho Aaron Lam. "Syntheses, characterization and photophysics of polynuclear copper (I)and silver (I) complexes containing monoynyl, diynyl and chalcogen-type ligands." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31240434.
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Lin, Yongyue. "Luminescent platinum(II), copper(I), silver(I) and zinc(II) complexes with functional pyridyl and arylacetylide ligands : structures, spectroscopic properties and applications /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25155325.
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Lazreg, Faïma. "Group 11 N-heterocyclic carbenes : synthesis, characterisation and catalytic applications." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/7059.
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As part of a worldwide effort to develop efficient catalysts for use in organic chemistry and in the synthesis of highly valuable molecules, work performed during the course of my stay in St Andrews has focused on the design and synthesis of new group 11 metal complexes for their applications in catalysis. The aim of this work was to develop new, active and stable, easy to synthesise group 11 complexes and investigate their catalytic activity as well as to try to understand their mode of action. Two different types of complexes were explored in order to develop more active catalysts: the neutral N-Heterocyclic carbene metal complexes and the cationic derivatives. More than 20 new catalysts were developed and their reactivity studied in different catalytic reactions. New hydroxide and tert-butoxide copper(I) or silver(I) complexes were developed and compared to the common NHC metal systems. Overall, the neutral NHC-metal catalysts showed to be highly active in a broad range of applications: in the methylation of amines using CO₂ as a C1 source, in a multicomponent reaction (A³ coupling) and in dual catalysis (hydrophenoxylation). Additionally, mechanistic studies were undertaken to obtain a greater understanding of these transformations and to possibly lead to the design of new generations of catalyst. Regarding the cationic NHC metal complexes, a straightforward methodology was developed leading to a library of highly stable catalysts. Bis-NHC, mixed NHC/ phosphine as well as NHC/pyridine species were efficiently synthesised using thermal or microwave heating, in high purity and yields. In addition, the effect of the presence of two different or identical ligands on catalytic reactivity was investigated in the 3+2 cycloaddition and in the alkynylation of ketones. Insight into the catalytic cycle was obtained via mechanistic studies. These showcased the release of one ligand during the catalytic cycle and the crucial role of this ligand displacement in generating the catalytically relevant active species. The results highlight the importance of understanding the reactivity of catalyst in order to develop new and improved ones.