Silver nanoparticles (Ag-NPs) readily transform in the environment, which modifies their properties and alters their transport, fate, and toxicity. It is essential to consider such transformations when assessing the potential environmental impact of Ag-NPs. This review discusses the major transformation processes of Ag-NPs in various aqueous environments, particularly transformations of the metallic Ag cores caused by reactions with (in)organic ligands, and the effects of such transformations on physical and chemical stability and toxicity. Thermodynamic arguments are used to predict what forms of oxidized silver will predominate in various environmental scenarios. Silver binds strongly to sulfur (both organic and inorganic) in natural systems (fresh and sea waters) as well as in wastewater treatment plants, where most Ag-NPs are expected to be concentrated and then released. Sulfidation of Ag-NPs results in a significant decrease in their toxicity due to the lower solubility of silver sulfide, potentiall...

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Environmental transformations of silver nanoparticles: impact on stability and toxicity.

Morphology and mechanisms of formation of natural patinas on archaeological Cu–Sn alloys

Metal nanostructures, such as nanoparticles and nanowires, have been proposed as building blocks for several applications in nanofabrication and nanoelectronics However, even when atmospheric corrosion is common in metals, there is a lack of information about the stability of those nanostructures against such phenomenon Therefore, we decided to study the atmospheric corrosion of silver nanowires and nanoparticles synthesized by the polyol method using poly(vinylpyrrolidone) (PVP) as the capping agent by different techniques, including transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) After synthesis and purification, the silver nanostructures were deposited on different substrates and exposed to laboratory air at ambient conditions The structural changes in the samples were monitored by TEM as a function of time for a period of time of 24 weeks Our results demonstrated that these silver nanostructures are susceptible to atmospheric corrosion and that, in most cases, a 

Corrosion at the Nanoscale: The Case of Silver Nanowires and Nanoparticles

The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid−solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagome network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG). Under similar experimental conditions, DBA 2a shows the formation of a honeycomb network. The core symmetry and location of alkyl substituents determine the network structure. The most remarkable feature of the DBA networks is the interdigitation of the nonpolar alkyl chains:  they connect the π-conjugated cores and direct their orientation. As a result, 2D open networks with voids are formed. Second, the effect of alkyl chain length on the structure of DBA patterns was investigated. Upon increasing the length of the alkyl c...

Two-dimensional porous molecular networks of dehydrobenzo[12]annulene derivatives via alkyl chain interdigitation.

Situated adjacent to the largest Northern Hemispher ice sheets of the ice ages, the mid-latitude North Atlantic Ocean has an important role in the earth's climate history. It provides a significant local source of moisture for the atmosphere and adjacent continents, forms a corridor that guides moisture-bearing storms northward from low latitudes, and at times makes direct contact along its shorelines with continental ice masses. Evidence of major ice-ocean-air interactions involving the North Atlantic during the last 250,000 years is summarized. Outflow of icebergs and meltwater initially driven by summer insolation over the ice sheets affects midlatitude ocean temperatures, summer heat storage, winter sea-ice extent, and global sea level. These oceanic responses in turn influence the winter moisture flux back to the ice sheets, as well as ablation of land ice by calving. Spectral data indicate that the oceanic moisture and sea-level feedbacks, in part controlled by glacial melt products, amplify Milankovitch (insolation) forcing of the volumetrically dominant mid-latitude ice sheets at the 23,000-year precessional cycle.

http://science.sciencemag.org/content/sci/212/4495/617.full.pdf

Oceanic Mechanisms for Amplification of the 23,000-Year Ice-Volume Cycle

The corrosion of silver by atmospheric sulfurous gases

Bulk YBa2Cu3O7-δ superconductors, under certain processing conditions such as melt texturing, exhibit a very high dislocation density of 109 to 1010 per square centimeter. In addition, the density of low-angle grain boundaries in such samples can be significantly increased (to less than 700-nanometer spacing) through a dispersion of submicrometer-sized Y2BaCuO5 inclusions. These defect densities are comparable to those in high critical current thin films as revealed through scanning tunneling microscopy, and yet the critical current densities in the bulk materials (at 77 kelvin and a field of 1 tesla for example) remain at a 104 amperes per square centimeter level, about two orders of magnitude lower than in thin films. The results imply that these defect density levels are not significant enough to explain the difference in flux pinning strength between the thin film and bulk materials. The observation of spiral-like growth of the superconductor phase in bulk Y-Ba-Cu-O is also reported.

https://science.sciencemag.org/content/sci/253/5018/427.full.pdf

Dislocations and Flux Pinning inYBa2Cu3O7-δ

The corrosion of copper by atmospheric sulphurous gases

Superconducting properties of the YBa 2 Cu 3 O 7−δ compound with partial rare earth substitution (20 atomic pct substitution for yttrium) have been studied. Among the 14 rare earth elements investigated, La, Ce and Pr caused suppression in T c , while other elements had no effect. Some of the rare earths (Sm, Gd, Eu), when partially substituted for Y, resulted in a slight improvement in intragrain J c (flux pinning) as measured magnetically. Although the rare earth elements have widely different ionic radii, all the (RE) Ba 2 Cu 3 O 7−δ phases have been found to be soluble in YBa 2 Cu 3 O 7−δ with no detectable segregation observed by SEM and energy dispersive X-ray analysis.

G. W. Kammlott

Papers

The corrosion of silver by atmospheric sulfurous gases

Dislocations and Flux Pinning inYBa2Cu3O7-δ

The corrosion of copper by atmospheric sulphurous gases

Superconducting properties of YBa2Cu3O7−δ with partial rare earth substitution

Thermal conductivity and the microstructure of state-of-the-art chemical-vapor-deposited (CVD) diamond