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Functionalized Nanogold: Its Fabrication and Needs
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials I, 2020
A seedless approach can be considered to synthesize gold nanotriangles (Kuttner et al., 2018). The process involves reacting an appropriate amount of gold chloride and benzyl dimethyl hexadecyl ammonium chloride (BDAC), followed by heating the mixture to a variable temperature of 70–95 °C. 3-barbituric acid (3BA) was added while maintaining the ratio [3BA] / [gold chloride] = 45.6. The final product comprises of nanotriangle and nanooctahedra, which are collected by centrifugation removing excess 3BA and BDAC. The gold nanotriangle and nanooctahedra are separated by a depletion-induced separation approach using CTAC. The mixture of particles is centrifuged, and the supernatant are discarded. The precipitate was re-dispersed in CTAC, and after 4 h the precipitate was discarded. The supernatant was centrifuged for 30 min. The precipitate was re-dispersed again in CTAC, and after 4 h the supernatant was discarded and the precipitate with gold nanotriangle was re-dispersed in BDAC. Overgrowth of gold is achieved taking gold nanotriangle as the seeds. For the overgrowth, a various ratio of [gold chloride] / [gold nanotriangle] and [3BA] / [gold chloride] was taken. Gold chloride and BDAC were mixed at 70 °C followed by the addition of 3-BA unless the solution became colorless. Gold nanotriangle seeds were added to the colorless solution while continuing stirring.
Synthesis of Organic Electroactive Materials in Ionic Liquids
Published in Di Wei, Electrochemical Nanofabrication, 2017
Michal Wagner, Carita Kvarnström, Ari Ivaska
Pringle et al. used [MEIM][Tf2N] (1-methyl-3-ethylimidazolium) in chemical synthesis of PPy and PTh. Different chemical oxidants (gold chloride, Fe tosylate, silver nitrate, and Fe(ClO4)3) were used as dopants [81]. It was found that gold chloride suits best for fabrication of conducting polymer nanoparticles. The size of PTh and PPy particles were from 100 to 500 nm with conductivity ranging from 1 to 3 mS cm−1. Recently Kim et al. made PPy nanostructures in the so-called magnetic IL [82]. They used [BMIM] [FeCl4], which is active under magnetic field and can be considered a paramagnetic compound [83]. PPy particles were made by self-assembled method where [BMIM][FeCl4] was mixed with monomer and a magnetic field was applied resulting in PPy precipitate. Magnetic IL acted threefold: as dopant, catalyst, and solvent. The self-assembled particles were spheres of the size ranging from 50 to 100 nm with high electrical conductivities. Also in a recent paper Pringle et al. utilized [EMIM][Tf2N] for synthesis of PPy-gold and -silver composites with the use of gold chloride and silver nitrate [84]. The use of these oxidants enabled a simple one-step fabrication of nanocomposites and IL assisted incorporation of metallic gold and silver into the polymer structure.
Metal Nanoparticles: Silver
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
Lively accounts of metal nanoparticles history can be found in many books (Johnson, 1949; Staudinger, 1950; Jirgensons et al., 1962; Voyutsky, 1978). Here we limit ourselves to only some selected milestone. In 1673 the German alchemist Andreas Cassium in Hamburg prepared the Purple of Cassius by reducing dilute solutions of HAuCl4 with SnCl2 obtaining a purple suspension of gold nanoparticles in water (Zsigmondy et al., 1925). In 1856, Michael Faraday was able to produce a colloidal gold hydrosol by reducing gold chloride with phosphorus (Johnson, 1949). The real breakthrough in the field of metal nanoparticles occurred with the development of colloidal chemistry worked out (among many others) by the famous chemists W. Ostwald (Nobel Laureate in 1909), R. Szigmondy (Nobel Laureate in 1925) who worked especially on colloidal gold and T. Svedberg (Nobel Laureate in 1926) for the discovery of the ultracentrifuge (Laylin, 1993). Another scientist to be remembered here is Gustav Mie who provided the theory for scattering and absorption by spherical particles explaining the change in color of the metal nanoparticles as a function of their dimensions (Voyutsky, 1978). The introduction of the concept of plasmon by Bohm and Pines (1953) and Shevchik (1974) as quantum plasma oscillations of the free electron gas density in metal nanoparticles led to a further insight in our understanding of the color of the nanoparticles and the mechanism of their electronic transitions. Henglein should be remembered here as the scientist who has paved the way to the developments in our ability to control the dimension, shape, and stability of the metal nanoparticles (Henglein, 1989).
A review of Preg-robbing and the impact of chloride ions in the pressure oxidation of double refractory ores
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Wei Sung ng, Qiankun wang, Miao chen
Gold is able to complex with chloride under acidic, high temperature, oxidizing conditions, forming soluble gold chloride complexes (Marsden and House 2006; Nicol 1980):