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.

Ordered anion adlayers on metal electrode surfaces.

The recent availability of shale gas has led to a renewed interest in C-H bond activation as the first step towards the synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and Pt can perform this chemistry, but deactivate easily due to coke formation. Cu-based catalysts are not practical due to high C-H activation barriers, but their weaker binding to adsorbates offers resilience to coking. Using Pt/Cu single-atom alloys (SAAs), we examine C-H activation in a number of systems including methyl groups, methane and butane using a combination of simulations, surface science and catalysis studies. We find that Pt/Cu SAAs activate C-H bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke-resistant C-H activation chemistry, with the added economic benefit that the precious metal is diluted at the atomic limit.

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Pt/Cu single-atom alloys as coke-resistant catalysts for efficient C-H activation.

Silver nanoparticles (AgNPs) are well known for their excellent antibacterial ability and superior physical properties, and are widely used in a growing number of applications ranging from home disinfectants and medical devices to water purificants. However, with the accelerating production and introduction of AgNPs into commercial products, there is likelihood of release into the environment, which raises health and environmental concerns. This article provides a critical review of the state-of-knowledge about AgNPs, involving the history, analysis, source, fate and transport, and potential risks of AgNPs. Although great efforts have been made in each of these aspects, there are still many questions to be answered to reach a comprehensive understanding of the positive and negative effects of AgNPs. In order to fully investigate the fate and transport of AgNPs in the environment, appropriate methods for the preconcentration, separation and speciation of AgNPs should be developed, and analytical tools for the characterization and detection of AgNPs in complicated environmental samples are also urgently needed. To elucidate the environmental transformation of AgNPs, the behavior of AgNPs should be thoroughly monitored in complex environmental relevant conditions. Furthermore, additional in vivo toxicity studies should be carried out to understand the exact toxicity mechanism of AgNPs, and to predict the health effects to humans.

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Silver nanoparticles in the environment

The surface-mediated synthesis of epitaxially aligned and separated polyphenylene lines on Cu(110) by exploiting the Ullmann dehalogenation reaction is reported. Scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) show that the C-I bonds of 1,4-diiodobenzene and 1,3-diiodobenzene (C6H4I2) are catalytically cleaved when dosed onto the surface. Subsequent annealing transforms the copper-bound phenylene intermediates into covalent conjugated structures: linear chains of poly(p-phenylene) for 1,4-diiodobenzene and zigzag chains of poly(m-phenylene) as well as macrocyclic oligomers in the case of 1,3-diiodobenzene. The chains are strongly bound to the surface (likely through C[BOND]Cu bonds at the chain-ends) while the macrocycles are very mobile and can only be imaged by STM at low temperature. The detached halogens adsorb on the surface and separate the polymer chains from each other.

Synthesis of polyphenylene molecular wires by surface-confined polymerization.

Atomic scale observation of iodine layer compression on Cu(1 1 1)

Atomic structure of saturated chlorine monolayer on Ag(111) surface

A clean Si(001) surface thermally purified in an ultrahigh vacuum molecular-beam epitaxy chamber has been investigated by means of scanning tunneling microscopy. The morphological peculiarities of the Si(001) surface have been explored in detail. The classification of the surface structure elements has been carried out, the dimensions of the elements have been measured, and the relative heights of the surface relief have been determined. A reconstruction of the Si(001) surface prepared in the molecular-beam epitaxy chamber has been found to be (8 × n). A model of the Si(001)-(8 × n) surface structure is proposed.

Structure and peculiarities of the (8 × n )-type Si(001) surface prepared in a molecular-beam epitaxy chamber: A scanning tunneling microscopy study

The atomic structure of the disordered phase formed by oxygen on Ag(111) at low coverage is determined by a combination of low-temperature scanning tunneling microscopy and density functional theory. We demonstrate that the previous assignment of the dark objects in STM to chemisorbed oxygen atoms is incorrect and incompatible with trefoil-like structures observed in atomic-resolution images in current work. In our model, each object is an oxidelike ring formed by six oxygen atoms around the vacancy in Ag(111).

V. M. Shevlyuga

Papers

Atomic scale observation of iodine layer compression on Cu(1 1 1)

Atomic structure of saturated chlorine monolayer on Ag(111) surface

Structure and peculiarities of the (8 × n )-type Si(001) surface prepared in a molecular-beam epitaxy chamber: A scanning tunneling microscopy study

Adsorption of O 2 on Ag(111): Evidence of Local Oxide Formation

Atomic structure of chemisorbed iodine layer on Cu(1 1 0)