Abstract: A novel strategy to sense target molecules in human blood serum is achieved by immobilizing aptamers (APTs) on multiwalled carbon nanotubes (MWCNT) modified electrodes. In this work, the aminated aptamer selected for hydroxylated polychlorinated biphenyl (OHPCB) was covalently immobilized on the surface of the MWCNTCOOH modified glassy carbon electrode through amide linkage. The aptamers function as recognition probes for OHPCB by the binding induced folding of the aptamer. The developed aptasensing device was characterized by Electrochemical Impedance Spectroscopy (EIS), Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR). The aptasensor displayed excellent performance for OHPCB detection with a linear range from 0.16 to 7.5 μM. The sensitivity of the developed aptasensing platform is improved (1×10−8 M) compared to the published report (1×10−6 M) for the determination of OH-PCB (Turner et al., 2007). The better performance of the sensor is due to the unique platform, i.e. the presence of APTs onto electrodes and the combination with nanomaterials. The aptamer density on the electrode surface was estimated by chronocoulometry and was found to be 1.4×1013 molecules cm−2. The validity of the method and applicability of the aptasensor was successfully evaluated by the detection of OHPCB in a blood serum sample. The described approach for aptasensing opens up new perspectives in the field of biomonitoring providing a device with acceptable stability, high sensitivity, good accuracy and precision.

Abstract: In-situ bright field transmission electron microscopy (TEM) nanomechanical tensile testing and in-situ automated crystallographic orientation mapping in TEM were combined to unravel the elementary mechanisms controlling the plasticity of ultrafine grained Aluminum freestanding thin films. The characterizations demonstrate that deformation proceeds with a transition from grain rotation to intragranular dislocation glide and starvation plasticity mechanism at about 1% deformation. The grain rotation is not affected by the character of the grain boundaries. No grain growth or twinning is detected. (C) 2014 AIP Publishing LLC.

Abstract: We studied the Fe K-edge X-ray absorption near edge (XANES) spectra of several Roman black glass fragments in order to determine the Fe3+/ΣFe ratio of these materials. The selected archaeological glass samples cover the period 1st5th century AD in nine different sites of the North Western provinces of the Roman Empire. The fragments belong to two different compositional groups demonstrating a diachronic evolution: early Roman HMG (High Magnesia Glass) and Roman Imperial LMG (Low Magnesia Glass). The first group contains natural Fe levels (below 2 wt% as Fe2O3), while the LMG has concentrations above 5 wt%. This difference is also reflected by Fe3+/ΣFe values. Low iron glass was produced under strongly reducing conditions in order to obtain the black colour, with average Fe3+/ΣFe values ≈ 0.17. LMG glass is somewhat more oxidised (Fe3+/ΣFe ≈ 0.40.5). While HMG glass required active control of the furnace environment, LMG was made under ambient atmosphere and its higher oxidation degree is mainly determined by the chemistry of the raw glass.

Abstract: Freestanding graphene membranes were successfully functionalized with platinum nanoparticles (Pt NPs). High-resolution transmission electron microscopy revealed a homogeneous distribution of single-crystal Pt NPs that tend to exhibit a preferred orientation. Unexpectedly, the NPs were also found to be partially exposed to the vacuum with the top Pt surface raised above the graphene substrate, as deduced from atomic-scale scanning tunneling microscopy images and detailed molecular dynamics simulations. Local strain accumulation during the growth process is thought to be the origin of the NP self-organization. These findings are expected to shape future approaches in developing Pt NP catalysts for fuel cells as well as NP-functionalized graphene-based high-performance electronics.

Abstract: Strong granularity-correlated and intragrain modulations of the superconducting order parameter are demonstrated in heavily boron-doped diamond situated not yet in the vicinity of the metal-insulator transition. These modulations at the superconducting state (SC) and at the global normal state (NS) above the resistive superconducting transition, reveal that local Cooper pairing sets in prior to the global phase coherence.

Abstract: Diffusive properties of interacting magnetic dipoles confined in a parabolic narrow channel and in the presence of a periodic modulated (corrugated) potential along the unconfined direction are studied using Brownian dynamics simulations. We compare our simulation results with the analytical result for the effective diffusion coefficient of a single particle by Festa and d'Agliano [Physica A 90, 229 (1978)] and show the importance of interparticle interaction on the diffusion process. We present results for the diffusion of magnetic dipoles as a function of linear density, strength of the periodic modulation and commensurability factor.

Abstract: Carbon nanotubes (CNTs) are one of the most promising nanomaterials to be used in biomedicine for drug/gene delivery as well as biomedical imaging. This study develops radio-labeled, iron oxide-decorated multiwalled CNTs (MWNTs) as dual magnetic resonance (MR) and single photon emission computed tomography (SPECT) contrast agents. Hybrids containing different amounts of iron oxide are synthesized by in situ generation. Physicochemical characterisations reveal the presence of superparamagnetic iron oxide nanoparticles (SPION) granted the magnetic properties of the hybrids. Further comprehensive examinations including high resolution transmission electron microscopy (HRTEM), fast Fourier transform simulations, X-ray diffraction, and X-ray photoelectron spectroscopy assure the conformation of prepared SPION as γ-Fe2O3. High r2 relaxivities are obtained in both phantom and in vivo MRI compared to the clinically approved SPION Endorem. The hybrids are successfully radio labeled with technetium-99m through a functionalized bisphosphonate and enable SPECT/CT imaging and γ-scintigraphy to quantitatively analyze the biodistribution in mice. No abnormality is found by histological examination and the presence of SPION and MWNT are identified by Perls stain and Neutral Red stain, respectively. TEM images of liver and spleen tissues show the co-localization of SPION and MWNTs within the same intracellular vesicles, indicating the in vivo stability of the hybrids after intravenous injection. The results demonstrate the capability of the present SPIONMWNT hybrids as dual MRI and SPECT contrast agents for in vivo use.

Abstract: The ground state of colloidal magnetic particles in a modulated channel are investigated as a function of the tilt angle of an applied magnetic field. The particles are confined by a parabolic potential in the transversal direction while in the axial direction a periodic substrate potential is present. By using Monte Carlo simulations, we construct a phase diagram for the different crystal structures as a function of the magnetic field orientation, strength of the modulated potential, and the commensurability factor of the system. Interestingly, we found first-and second-order phase transitions between different crystal structures, which can be manipulated by the orientation of the external magnetic field. A reentrant behavior is found between two-and four-chain configurations, with continuous second-order transitions. Novel configurations are found consisting of frozen solitons of defects. By changing the orientation and/or strength of the magnetic field and/or the strength and periodicity of the substrate potential, the system transits through different phases.

Abstract: Soot deposition has the negative ability to devalue the aesthetic appearance of buildings. Titanium dioxide applied on the building material is one way to counteract this problem as it provides air-purifying and self-cleaning properties due to its photocatalytic activity. In literature, photocatalytic soot oxidation was described, but until now, little information was available about the influence of process parameters on the photocatalytic degradation efficiency. The influence of three process parameters was tested in this study, namely TiO2 concentration, soot concentration and water-to-cement ratio (WIC-ratio) of the mortar substrates. The results revealed 50 mu gTiO(2) cm(-2) is better to use on the cementitious materials than 250 mu gTiO(2) cm(-2). The soot concentrations occurring in real-world situations will not inhibit the photocatalyst to be activated by light. Furthermore, the photonic efficiency increases slightly for lower WIC-ratios. This can be of interest for structural building applications, since a lower WIC-ratio results in a lower porosity of the samples and consequently in an increase in mortar strength. (C) 2013 Elsevier B.V. All rights reserved.

Abstract: In TEM, a typical goal consists of making a small electron probe in the sample plane in order to obtain high spatial resolution in scanning transmission electron microscopy. In order to do so, the phase of the electron wave is corrected to resemble a spherical wave compensating for aberrations in the magnetic lenses. In this contribution, we discuss the advantage of changing the phase of an electron wave in a specific way in order to obtain fundamentally different electron probes opening up new applications in the (S)TEM. We focus on electron vortex states as a specific family of waves with an azimuthal phase signature and discuss their properties, production and applications. The concepts presented here are rather general and also different classes of probes can be obtained in a similar fashion, showing that electron probes can be tuned to optimize a specific measurement or interaction.

Abstract: The pyrochlore compounds Ho2Ti2O7 and Dy2Ti2O7 show an exotic form of magnetism called the spin ice state, resulting from the interplay between geometrical frustration and ferromagnetic coupling. A fascinating feature of this state is the appearance of magnetic monopoles as emergent excitations above the degenerate ground state. Over the past years, strong effort has been devoted to the investigation of these monopoles and other properties of the spin ice state in bulk crystals. Here, we report the fabrication of Ho2Ti2O7 thin films using pulsed laser deposition on yttria-stabilized ZrO2 substrates. We investigated the structural properties of these films by X-ray diffraction, scanning transmission electron microscopy, and atomic force microscopy, and the magnetic properties by vibrating sample magnetometry at 2 K. The films not only show a high crystalline quality, but also exhibit the hallmarks of a spin ice: a pronounced magnetic anisotropy and an intermediate plateau in the magnetization along the [111] crystal direction.

Abstract: Current-voltage analysis using different optical band pass filters has been performed on Cu2ZnSnSe4 and Cu2ZnSn(S, Se)(4) thin-film solar cells. When using red or orange light (i.e. wavelengths above 600 nm), a distortion appears in the I-V curve of the Cu2ZnSnSe4 solar cell, indicating an additional potential barrier to the current flow in the device for these conditions of illumination. This barrier is reduced when using a Cu2ZnSn(S, Se)(4) absorber. Numerical simulations demonstrate that the barrier visible under red light could be explained by a positive conduction band offset at the front interface coupled with compensating defects in the buffer layer.

Abstract: ZnOCo nanocomposite thin films are synthesized by combination of pulsed laser deposition of ZnO and Co ion implantation. Both superparamagnetism and relaxor ferroelectricity as well as magnetoelectric coupling in the nanocomposites have been demonstrated. The unexpected relaxor ferroelectricity is believed to be the result of the local lattice distortion induced by the incorporation of the Co nanoparticles. Magnetoelectric coupling can be attributed to the interaction between the electric dipole moments and the magnetic moments, which are both induced by the incorporation of Co. The introduced ZnOCo nanocomposite thin films are different from conventional strain-mediated multiferroic composites.

Abstract: In this paper we demonstrate that by means of scanning reflection FTIR spectroscopy, it is possible to record highly specific distribution maps of organic and inorganic compounds from flat, macroscopic objects with cultural heritage value in a non-invasive manner. Our previous work involved the recording of macroscopic distributions of chemical elements or crystal phases from painted works of art based on respectively macroscopic X-ray fluorescence or X-ray powder diffraction analysis. The use of infrared radiation instead of X-rays has the advantage that more specific information about the nature and distribution of the chemical compounds present can be gathered. This higher imaging specificity represents a clear advantage for the characterization of painting and artist materials. It allows the distribution of metallo-organic compounds to be visualized and permits distinguishing between pigmented materials containing the same key metal. The prototype instrument allows the recording of hyperspectral datacubes by scanning the surface of the artefact in a contactless and sequential single-point measuring mode, while recording the spectrum of reflected infrared radiation. After the acquisition, spectral line intensities of individual bands and chemical distribution maps can be extracted from the datacube to identify the compounds present and/or to highlight their spatial distribution. Not only is information gained on the surface of the investigated artefacts, but also images of overpainted paint layers and, if present, the underdrawing may be revealed in this manner. A current major limitation is the long scanning times required to record these maps.

Abstract: Methane reforming by plasma catalysis is a complex process that is far from understood. It requires a multidisciplinary approach which ideally takes into account all effects from the plasma on the catalyst, and vice versa. In this contribution, we focus on the interactions of CHx (x = {1,2,3}) radicals that are created in the plasma with several nickel catalyst surfaces. To this end, we perform reactive molecular dynamics simulations, based on the ReaxFF potential, in a wide temperature range of 4001600 K. First, we focus on the H2 formation as a function of temperature and surface structure. We observe that substantial H2 formation is obtained at 1400 K and above, while the role of the surface structure seems limited. Indeed, in the initial stage, the type of nickel surface influences the CH bond breaking efficiency of adsorbed radicals; however, the continuous carbon diffusion into the surface gradually diminishes the surface crystallinity and therefore reduces the effect of surface structure on the H2 formation probability. Furthermore, we have also investigated to what extent the species adsorbed on the catalyst surface can participate in surface reactions more in general, for the various surface structures and as a function of temperature. These results are part of the ongoing research on the methane reforming by plasma catalysis, a highly interesting yet complex alternative to conventional reforming processes.