Silicate glasses are durable solids, and yet they are chemically unstable in contact with aqueous fluids-this has important implications for numerous industrial applications related to the corrosion resistance of glasses, or the biogeochemical weathering of volcanic glasses in seawater. The aqueous dissolution of synthetic and natural glasses results in the formation of a hydrated, cation-depleted near-surface alteration zone and, depending on alteration conditions, secondary crystalline phases on the surface. The long-standing accepted model of glass corrosion is based on diffusion-coupled hydration and selective cation release, producing a surface-altered zone. However, using a combination of advanced atomic-resolution analytical techniques, our data for the first time reveal that the structural and chemical interface between the pristine glass and altered zone is always extremely sharp, with gradients in the nanometre to sub-nanometre range. These findings support a new corrosion mechanism, interfacial dissolution-reprecipitation. Moreover, they also highlight the importance of using analytical methods with very high spatial and mass resolution for deciphering the nanometre-scale processes controlling corrosion. Our findings provide evidence that interfacial dissolution-reprecipitation may be a universal reaction mechanism that controls both silicate glass corrosion and mineral weathering.

Functionalization of nanomaterials for precise biomedical function is an emerging trend in nanotechnology. Carbon nanotubes are attractive as multifunctional carrier systems because payload can be encapsulated in internal space whilst outer surfaces can be chemically modified. Yet, despite potential as drug delivery systems and radiotracers, such filled-and-functionalized carbon nanotubes have not been previously investigated in vivo. Here we report covalent functionalization of radionuclide-filled single-walled carbon nanotubes and their use as radioprobes. Metal halides, including Na(125)I, were sealed inside single-walled carbon nanotubes to create high-density radioemitting crystals and then surfaces of these filled-sealed nanotubes were covalently modified with biantennary carbohydrates, improving dispersibility and biocompatibility. Intravenous administration of Na(125)I-filled glyco-single-walled carbon nanotubes in mice was tracked in vivo using single-photon emission computed tomography. Specific tissue accumulation (here lung) coupled with high in vivo stability prevented leakage of radionuclide to high-affinity organs (thyroid/stomach) or excretion, and resulted in ultrasensitive imaging and delivery of unprecedented radiodose density. Nanoencapsulation of iodide within single-walled carbon nanotubes enabled its biodistribution to be completely redirected from tissue with innate affinity (thyroid) to lung. Surface functionalization of (125)I-filled single-walled carbon nanotubes offers versatility towards modulation of biodistribution of these radioemitting crystals in a manner determined by the capsule that delivers them. We envisage that organ-specific therapeutics and diagnostics can be developed on the basis of the nanocapsule model described here.

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Articles you may be interested inPreparation of transmission electron microscopy cross-section specimens using focused ion beam milling Proposals for exact-point transmission-electron microscopy using focused ion beam specimen-preparation technique J.Transmission electron microscopy observation of thin foil specimens prepared by means of a focused ion beam A plasma-polymerized protective film for transmission electron microscopy specimen preparation by focused ion beam etching Precision transmission electron microscopy sample preparation using a focused ion beam by extraction method A new technique for the preparation of site specific plan-view specimens using a focused ion beam system is presented. The technique consists of milling a wedge shaped piece of material which is free from the substrate, lifting this out using a micromanipulator and needle, and orientating it on the substrate with the original surface vertical. The plan-view specimen is then milled from this piece of material using an approach based on the ''lift-out'' technique for the preparation of a cross-section specimen. Advantages of this technique over current methods based on the ''lift-out'' and the ''trench'' techniques are that the plan-view specimens are site specific, the surrounding substrate is left intact, and numerous plan-view specimens can be prepared in close proximity to one another.

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Cobalt nanoparticles were synthesised via the thermal decomposition of Co2(CO)8 and were coated in iron oxide using Fe(CO)5. While previous work focused on the subsequent thermal alloying of these nanoparticles, this study fully elucidates their composition and core@shell structure. State-of-the-art electron microscopy and statistical data processing enabled chemical mapping of individual particles through the acquisition of energy-filtered transmission electron microscopy (EFTEM) images and detailed electron energy loss spectroscopy (EELS) analysis. Multivariate statistical analysis (MSA) has been used to greatly improve the quality of elemental mapping data from core@shell nanoparticles. Results from a combination of spatially resolved microanalysis reveal the shell as Fe3O4 and show that the core is composed of oxidatively stable metallic Co. For the first time, a region of lower atom density between the particle core and shell has been observed and identified as a trapped carbon residue attributable to the organic capping agents present in the initial Co nanoparticle synthesis.

Macroscopic behaviour of materials is often controlled by microscopic events; this has driven interest in testing and analysing increasingly smaller features. The ability to perform mechanical tests on the micron-scale, with modelling and high resolution chemical and structural analysis on the same scale, now makes it possible to investigate in detail the mechanisms controlling one of the most complex modes of fracture: stress corrosion cracking (SCC). In this paper, through such a multifaceted approach, we show that individual grain boundaries, preferentially oxidized after exposure to simulated pressurized nuclear reactor cooling water, can be mechanically tested and their resistance to fracture quantified. These results have direct consequences in understanding the mechanisms controlling SCC propagation and initiation.