[en] The γ′ strengthening phase in an advanced nickel-based superalloy, ATI 718Plus, was characterized using a blind source separation applied to a four dimensional X-ray microanalysis dataset obtained by scanning transmission electron microscopy. Selected patterns in the X-ray spectra identified by independent component analysis were found to be spatially and chemically representative of the matrix (γ) and precipitate phases (γ′) present in the superalloy, enabling their size, shape and distribution to be determined. The three dimensional chemical reconstruction of the microstructure may provide insight into the role of the various alloying elements in the evolution of the microstructure at the nano-scale.

[en] Organic-inorganic hybrid perovskite solar cells have exhibited power conversion efficiencies comparable to more established PV technologies thanks to their favourable optoelectronic properties, but low operational stability inhibits their commercialisation and widespread use. Many degradation pathways are possible and most of them are not currently well understood at the nanoscale due to the difficulty of characterising a perovskite solar cell's complex nanostructure. This work reviews the application of in-situ and operando electron microscopy to visualise the dynamic processes that occur in perovskite solar cells as various stimuli are applied inside a microscope column. Additionally, potential challenges and an outlook on future uses of this technique are briefly discussed.

[en] The growth of nanostructured nickel : carbon (Ni : C) nanocomposite thin films by the supersonic cluster beam deposition of nickel and carbon clusters co-deposited from two separate beam sources has been demonstrated. Ni : C films retain the typical highly disordered structure with predominant sp² hybridization, low density, high surface roughness and granular nanoscale morphology of cluster assembled nanostructured carbon, but display enhanced electric conductivity. The electric double layer (EDL) capacitance of Ni : C films featuring the same thickness (200 nm) and different nickel volumetric concentrations (0–35%) has been investigated by electrochemical impedance spectroscopy employing an aqueous solution of potassium hydroxide (KOH 1 M) as electrolyte solution. Evidence of increased electric conductivity, facilitated EDL formation and negligible porous structure modification was found as consequence of Ni embedding. This results in the ability to synthesize electrodes with tailored specific power and energy density by the accurate control of the amount of deposited Ni and C clusters. Moreover, nickel nanoparticles were shown to catalyze the formation of tubular onion-like carbon structures upon mild thermal treatment in inert atmosphere. Electrochemical characterization of the heated nanocomposite electrodes revealed that the presence of long range ordered sp² structures further improves the power density and energy storage properties. (paper)

[en] The role of ruthenium and its oxides in catalysis, electrochemistry, and electronics is becoming increasingly important because of the high thermal and chemical stability, low resistivity, and unique redox properties of this metallic system. We report an observation of RuO₂ nanorods decorated with nanometer size Ru metal clusters. We identify precise crystallographic relationships between metal and oxide, and provide a simple model for the synthesis of these structures, based on the theory of columnar growth. The high aspect ratio, high surface area, and quantum size crystalline decorations of these nanostructures make them particularly attractive candidates for further fundamental research and for advanced catalytic and electronic applications

[en] We study graphene growth on hafnia (HfO₂) nanoparticles by chemical vapour deposition using optical microscopy, high resolution transmission electron microscopy and Raman spectroscopy. We find that monoclinic HfO₂ nanoparticles neither reduce to a metal nor form a carbide while nucleating nanometer domain-sized few layer graphene. Hence we regard this as an interesting non-metallic catalyst model system with the potential to explore graphene growth directly on a (high-k) dielectric. HfO₂ nanoparticles coated with few layer graphene by atmospheric pressure CVD with methane and hydrogen at 950 C. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] The use of magnetic fields in magnetic resonance imaging (MRI) for the tracking and delivery of chemotherapeutics bound to superparamagnetic nanoparticles offers a promising method for the non-invasive treatment of inoperable tumours. Here we demonstrate that superparamagnetic magnetite nanoparticles fabricated by an easily scalable method can be driven and tracked in real time at high velocities in vitro using MRI hardware. Force balance calculations are consistent with the magnetic properties of individual 10 nm diameter particles that move collectively as micron sized agglomerates with hydrodynamic diameter similar to that inferred from zero-magnetic-field dynamic light scattering measurements

[en] Highlights: • Large area devices (1 cm²) were realized with high reproducibility showing a maximum efficiency of 15.4%. • Several sealing procedures were performed to minimize the effect of the sealing on the initial performance of the PSCs. • The optimized SP helps to study the intrinsic stability of PSCs during damp-heat, dry-heat and light soaking tests. • For the first time, we show the role of the HTL dopants in the light-soaking test at MPP to stabilize the PV performance. • Cross-sectional STEM characterization was performed to compare the perovskite morphology of fresh and aged cells. Perovskite Solar Cells (PSCs) have achieved power conversion efficiencies (PCEs) comparable to established technologies, but their stability in real-life working conditions – including exposure to moisture, heat and light - has still not been decisively demonstrated. Encapsulation of the cells is vital for increasing device lifetime, as well as shedding light on the intrinsic degradation process of the active layers. Here we compare different sealing protocols applied to large area cells (1 cm², average PCE 13.6%) to separate the extrinsic degradation, due to the external environment, from the intrinsic one, due to the materials themselves. Sealing methods were tested against accelerated life-time tests – damp-heating, prolonged heating and light-soaking. We thus developed and tested a novel sealing procedure that makes PSCs able to maintain a stabilized 10% PCE after heat, light and moisture stress.

[en] Quasi-1D-hyperbranched TiO₂ nanostructures are grown via pulsed laser deposition and sensitized with thin layers of CdS to act as a highly efficient photoelectrochemical photoanode. The device properties are systematically investigated by optimizing the height of TiO₂ scaffold structure and thickness of the CdS sensitizing layer, achieving photocurrent values up to 6.6 mA cm⁻² and reaching saturation with applied biases as low as 0.35 V_RHE. The high internal conversion efficiency of these devices is to be found in the efficient charge generation and injection of the thin CdS photoactive film and in the enhanced charge transport properties of the hyperbranched TiO₂ scaffold. Hence, the proposed device represents a promising architecture for heterostructures capable of achieving high solar-to-hydrogen efficiency. (paper)

[en] Electron tomography is an invaluable method for 3D cellular imaging. The technique is, however, limited by the specimen geometry, with a loss of resolution due to a restricted tilt range, an increase in specimen thickness with tilt, and a resultant need for subjective and time-consuming manual segmentation. Here we show that 3D reconstructions of needle-shaped biological samples exhibit isotropic resolution, facilitating improved automated segmentation and feature detection. By using scanning transmission electron tomography, with small probe convergence angles, high spatial resolution is maintained over large depths of field and across the tilt range. Moreover, the application of compressed sensing methods to the needle data demonstrates how high fidelity reconstructions may be achieved with far fewer images (and thus greatly reduced dose) than needed by conventional methods. These findings open the door to high fidelity electron tomography over critically relevant length-scales, filling an important gap between existing 3D cellular imaging techniques. - Highlights: • On-axis electron tomography of a needle-shaped biological sample is presented. • A reconstruction with isotropic resolution is achieved. • Compressed sensing methods are compared to conventional reconstruction algorithms. • High fidelity reconstructions are achieved with greatly undersampled datasets.

[en] Highlights: • Plasmonic Au nanoparticles (NPs) have been integrated in nanostructured TiO₂ films by single step pulsed laser co-deposition. • The plasmonic properties of Au-TiO₂ films are affected by the deposition conditions, the Au at.% and annealing treatments. • Au NPs are homogenously distributed within TiO₂. Annealing treatments favor NPs growth, inducing TiO₂ crystallization. • Au NPs increase light absorption of the TiO₂ film in the visible region showing a localized surface plasmon resonance peak. • Photodegradation tests show that the presence of Au NPs in TiO₂ films significantly increases the catalytic action. The plasmonic resonance of noble metal nanoparticles (NPs) can be exploited to enhance the photoresponse of wide band gap oxides in view of several solar energy applications. Here, we demonstrate single-step synthesis of plasmonic Au nanoparticles integrated in TiO₂ hierarchical nanoporous layers through a vapor phase pulsed laser co-deposition approach. Specifically, we report the fabrication and characterization of Au NPs-decorated TiO₂ forest-like systems with tunable porosity and density as well as the morphological/structural evolution as a function of Au content and we discuss the corresponding optical properties. The effect of post-deposition thermal treatment has been investigated as well in order to control TiO₂ crystallization and Au NPs nucleation and growth. Optical analyses show the onset of characteristic plasmonic resonance of Au NPs with the increase of film absorption in the visible range. Preliminary tests of photodegradation of methyl orange dye indicate that the integration of Au NPs leads to a significant increase of the catalytic activity of nanoporous TiO₂. Our results suggest the potentiality of this approach for the synthesis and the integration of metallic NPs within wide band gap semiconductors, while paving the way toward novel plasmonic-based devices.