نتایج جستجو برای: gold and silver
تعداد نتایج: 16853666 فیلتر نتایج به سال:
Throughout history, investors have attempted to determine the future states and prices of instruments that they consider to invest in. Thus, various econometric models have been developed in order to determine the variables influencing the prices of investment instruments, as well as the relationships between such variables. The main aim of the present study was to examine the variables that ma...
The Sebandoon Barite (gold-silver) deposit is located about 20 km NW of the Kashmar in the Central Iran. The rock units exposed in the area consist of Eocene volcano-sedimentary sequences of lithic tuff, rhyolitic tuff, tuffaceouce shale, lapilli tuff and agglomerate associated with pyroxene andesite and trachyandesite. The barite is composed of lenticular, banded and stockwork mineralization a...
Biogenic gold nanotriangles and spherical silver nanoparticles were synthesized by a simple procedure using Aloe vera leaf extract as the reducing agent. This procedure offers control over the size of the gold nanotriangle and thereby a handle to tune their optical properties, particularly the position of the longitudinal surface plasmon resonance. The kinetics of gold nanotriangle formation wa...
Gold, silver, platinum and palladium typically crystallize with the face-centred cubic structure. Here we report the high-yield solution synthesis of gold nanoribbons in the 4H hexagonal polytype, a previously unreported metastable phase of gold. These gold nanoribbons undergo a phase transition from the original 4H hexagonal to face-centred cubic structure on ligand exchange under ambient cond...
Abstraction of chloride anion from Au(I) complexes such as JohnPhosAuCl in noncoordinating solvents with 1 equiv of a silver salt, or even larger amounts, leads to the formation of chloride-bridged dinuclear gold(I) complexes, irrespective of the counteranion, which are substantially less reactive as catalysts. This incomplete removal of chloride ligand could lead to false negative results when...
Plasmid DNA can be used as a template to yield gold, palladium, silver, and chromium nanoparticles of different sizes based on variations in incubation time at 70 °C with gold phosphine complexes, with the acetates of silver or palladium, or chromium acetylacetonate. The employment of mild synthetic conditions, minimal procedural steps, and aqueous solvents makes this method environmentally gre...
The majority of gold(I) catalysts employed in organic transformations in homogeneous systems are presently generated in situ by reactions of gold halides AuX or their 1 : 1 complexes [(L)AuX] with silver salts AgY (X = Cl, Br; L = R3P, NHC, tht etc.; Y = BF4, PF6, SbF6, OSO2CF3, OC(O)CF3 etc.). This usage of silver salts is not only economically unfavorable, but also has several practical disad...
It is now well-known that the size, shape, and composition of nanomaterials can dramatically affect their physical and chemical properties, and that technologies based on nanoscale materials have the potential to revolutionize fields ranging from catalysis to medicine. Among these materials, anisotropic particles are particularly interesting because the decreased symmetry of such particles ofte...
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