Natural gold nanoparticles

Hough, R. M.; Noble, Ryan; Reich, Martín

doi:10.1016/j.oregeorev.2011.07.003

Cited by 171 publications

(79 citation statements)

References 40 publications

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“…This is evidenced by the observation of AuNPs and AgNPs in ore deposits 16,17 and environmental waters. 18 It is believed that these nanoparticles play important roles in geochemical reactions, weathering processes, metal migration, and supergene enrichments.…”

Section: à7mentioning

confidence: 91%

Sunlight-Induced Reduction of Ionic Ag and Au to Metallic Nanoparticles by Dissolved Organic Matter

2012

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Metal-engineered nanoparticles (MENPs) with unique optical, electronic, and chemical properties have potential applications in catalysis, optical devices, and electronic applications. Particularly, metallic silver nanoparticles (AgNPs) have been applied as a broadspectrum antimicrobial agent in recent years. Colloidal nanosilver has been used for more than 100 years and has been registered as a biocidal material in the U.S. since 1954.2 AgNPs are the most common materials in nanotechnology-based consumer products, and the worldwide production of AgNPs was estimated at 500 t/a in 2008. 3 Inevitably, these MENPs can be discharged into the environment through the manufacturing, usage, disposal, and recycling processes of commercial products. 4À7The potential toxicity 8 and bioaccumula-

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Section: à7mentioning

confidence: 91%

Sunlight-Induced Reduction of Ionic Ag and Au to Metallic Nanoparticles by Dissolved Organic Matter

2012

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“…This suggests that surface morphologies of gold grains from New Zealand and Finland are the result of supergene transformations occurring in current environments. As evaporation (as suggested by Hough et al [13,15] for semi-arid environments) in unlikely to be a major process for the formation of nano-particulate gold in these high-rainfall environments, the abundance of gold nano-particles in New Zealand and Finland strongly suggests that geobiological processes are drivers of secondary gold formation and gold dispersion in temperate and subarctic environments.…”

Section: Temperate and Subarctic Environmentsmentioning

confidence: 92%

“…At arid sites, water and nutrient availability are limited and episodic, hence abiogenic evaporative mechanisms were thought to control the formation of secondary and especially nano-particulate gold [14,15]. To assess if geobiological processes play a role for the transformations of gold grains, grains were collected from eight arid sites in three Australian gold provinces, i.e., Lawlers (Yilgarn Craton, Western Australia), Tanami (Northern Territory), and Flinders Ranges (South Australia; [35]).…”

Section: Arid Environmentsmentioning

confidence: 99%

Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions

et al. 2013

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Microbial communities mediating gold cycling occur on gold grains from (sub)-tropical, (semi)-arid, temperate and subarctic environments. The majority of identified species comprising these biofilms are β-Proteobacteria. Some bacteria, e.g., Cupriavidus metallidurans, Delftia acidovorans and Salmonella typhimurium, have developed biochemical responses to deal with highly toxic gold complexes. These include gold specific sensing and efflux, co-utilization of resistance mechanisms for other metals, and excretion of gold-complex-reducing siderophores that ultimately catalyze the biomineralization of nano-particulate, spheroidal and/or bacteriomorphic gold. In turn, the toxicity of gold complexes fosters the development of specialized biofilms on gold grains, and hence the cycling of gold in surface environments. This was not reported on isoferroplatinum grains under most near-surface environments, due to the lower toxicity of mobile platinum complexes. The discovery of gold-specific microbial responses can now drive the development of geobiological exploration tools, e.g., gold bioindicators and biosensors. Bioindicators employ genetic markers from soils and groundwaters to provide information about gold mineralization processes, while biosensors will allow in-field analyses of gold concentrations in complex sampling media.

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“…Further, Herrington and Wilkinson [15] proposed that gold and silica colloids could be important in the higher temperature, deeper, "mesothermal" gold systems based on textural interpretations. A number of review papers have been published recently [1,[16][17][18][19] on the occurrence of gold nanoparticles in nature, and they contain many additional references both from within and outside of the ore-deposits realm. Hough et al [1] emphasized that both native copper and silver form metallic nanoparticles similar to those that are composed of gold or electrum.…”

Section: Introductionmentioning

confidence: 99%

“…Although we describe the role of nanoparticles in epithermal ore formation here, perhaps such particles are important in other systems. For example, gold colloids, nanoparticles, and/or nanocrystals also have been documented in "supergene" ± bacterial processes related to weathering of gold ores and gold-nugget formation [19][20][21], in volcanic fumaroles [22,23], in Carlin-type gold deposits [24,25], and also in active geothermal systems [2,[26][27][28]. Finally, metallic sulfide nanoparticles are significant components in the "black smoke" discharging from submarine hydrothermal vents [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Formation and Aggregation of Gold (Electrum) Nanoparticles in Epithermal Ores

Saunders

Burke

2017

Minerals

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Here, we review the concept that nanoparticles and colloids may have played a significant role in forming some types of hydrothermal ores deposits, particularly epithermal. This concept was first proposed almost a century ago but the development of new analytical technologies, lab experiments, and the discovery of new epithermal deposits where nanoparticles are evident have added credence to the "gold colloid theory". Nanoparticles are defined to have at least one dimension <10 −7 m, and may have different chemical and physical properties than the bulk solids. Colloids are typically <10 −6 m in diameter and have the added characteristic that they are dispersed in another medium. In epithermal ore-forming solutions, gold or electrum nanoparticles nucleate from supersaturated hydrothermal solutions, and thus this is a "far-from-equilibrium" process. In some cases, gold nanoparticles may simply play a transitory role of aggregating to form much coarser-grained crystals, where all of the evidence of nanoparticles precursor phases is not preserved. However, in some epithermal ores, silica nanoparticles also formed, and their co-deposition with gold (electrum) nanoparticles preserved the gold aggregation features as self-organized "fractal" dendrites. Here, we review existing the data on gold and electrum nanoparticles in epithermal ores, present images of electrum nanoparticles and their aggregates, and discuss the significance of gold nanoparticles formation and aggregation in helping to produce some of the highest-grade gold ores in the world.

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Natural gold nanoparticles

Cited by 171 publications

References 40 publications

Sunlight-Induced Reduction of Ionic Ag and Au to Metallic Nanoparticles by Dissolved Organic Matter

Sunlight-Induced Reduction of Ionic Ag and Au to Metallic Nanoparticles by Dissolved Organic Matter

Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions

Formation and Aggregation of Gold (Electrum) Nanoparticles in Epithermal Ores

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