Microstructure and defects of preferentially oriented platinum nanoparticles

n/

Multiferroic phase transition near room temperature in BiFeO3 films

In multiferroic BiFeO3 thin films grown on highly mismatched LaAlO3 substrates, we reveal the coexistence of two differently distorted polymorphs that leads to striking features in the temperature dependence of the structural and multiferroic properties. Notably, the highly distorted phase quasi-concomitantly presents an abrupt structural change, transforms from a hard to a soft ferroelectric and transitions from antiferromagnetic to paramagnetic at 360+/-20 K. These coupled ferroic transitions just above room temperature hold promises of giant piezoelectric, magnetoelectric and piezomagnetic responses, with potential in many applications fields

Evaluation of a 3-hydroxypyridin-2-one (2,3-HOPO) Based Macrocyclic Chelator for 89 Zr 4+ and Its Use for ImmunoPET Imaging of HER2 Positive Model of Ovarian Carcinoma in Mice

Abstract A novel octadentate 3-hydroxypyridin-2-one (2,3-HOPO) based di-macrocyclic ligand was evaluated for chelation of 89 Zr; subsequently, it was used as a bi-functional chelator for preparation of 89 Zr-labeled antibodies. Quantitative chelation of 89 Zr 4+ with the octadentate ligand forming 89 ZrL complex was achieved under mild conditions within 15 minutes. The 89 Zr-complex was stable in vitro in presence of DTPA, but a slow degradation was observed in serum. In vivo, the hydrophilic 89 Zr-complex showed prevalently renal excretion; and an elevated bone uptake of radioactivity suggested a partial release of 89 Zr 4+ from the complex. The 2,3-HOPO based ligand was conjugated to the monoclonal antibodies, HER2-specific trastuzumab and an isotypic anti-gD antibody, using a p-phenylene bis-isothiocyanate linker to yield products with an average loading of less than 2 chelates per antibody. Conjugated antibodies were labeled with 89 Zr under mild conditions providing the PET tracers in 60-69% yield. Despite the limited stability in mouse serum; the PET tracers performed very well in vivo. The PET imaging in mouse model of HER2 positive ovarian carcinoma showed tumor uptake of 89 Zr-trastuzumab (29.2 ± 12.9 %ID/g) indistinguishable (p = 0.488) from the uptake of positive control 89 Zr-DFO-trastuzumab (26.1 ± 3.3 %ID/g). In conclusion, the newly developed 3-hydroxypyridin-2-one based di-macrocyclic chelator provides a viable alternative to DFO-based heterobifunctional ligands for preparation of 89 Zr-labeled monoclonal antibodies for immunoPET studies

Tritiated water detection in the 2.17 µm spectral region by cavity ring down spectroscopy

International audienceNuclear waste containers are intended to be stored in dedicated disposals sites. For the inside and environmental safety of the disposals site, the tiny outgassing rates leaking out the containers are measured. The radioactive HT gas is actually measured by liquid scintillation, however an alternative method, cavity ring down spectroscopy, is currently developed for tritium measurement in its oxidized form HTO and evaluated. The HTO molecule concentration is determined by the measurement of spectroscopic parameters from transitions on its harmonic 21 (R) transitions between 4590 and 4600 cm-1. Two tritiated water standards are measured with a dedicated CRDS set-up. Compared to the theoretical database, the line positions are correct (-0.067 to -0.128 cm-1), their relative intensities is in agreement with the database, but their absolute intensities are 30% weaker. Among the seven intense lines, the 4596.485 cm-1 line (intensity 8.22 10-22 cm/molecule) and the 4592.407 cm-1 line (intensity 9.83 10-22 cm/molecule) are isolated and intense for a sensitive detection. The HTO detection limit with the present set-up is 3 kBq (10 min), equivalent to 1.8 1012 molecules in the 111 cm3 CRDS cell. This detection limit could improve by a factor 3 (at least) by reducing the detection noise

Tunable plasmonic dichroism of Au nanoparticles self-aligned on rippled Al

The self-alignment and optical dichroism of Au nanoparticle chains grown by glancing incidence deposition on rippled Al2O3 thin films is investigated. Although the nucleation of the nanoparticles is almost isotropic, their growth is strongly anisotropic resulting in a sharp dependence of their optical transmittance on the orientation of the polarization of the incident light. We show that both the frequency and the spectral width of the transverse and longitudinal surface plasmon resonances can be easily tuned by varying the amount of deposited metal. Such nanostructured materials open perspectives for the development of plasmonic devices endowed with tunable optical dichroism both in the visible and the near infrared regimes

Gold and silver nanoparticles embedded in dielectric-capping layers studied by HAADF-STEM

The morphology and optical response of Au and Ag nanoparticles capped with dielectric amorphous Si3N4, BN, and Al2O3 layers are studied. Quantitative analysis of high-angle annular dark-field images obtained in a scanning transmission electron microscope and simulations of optical transmittance spectra are used to investigate the dependence of the morphology of the nanoparticles on the particle size and on the capping material. It is demonstrated that capping-layer effects induce a size-dependent and cap-dependent reshaping of the nanoparticles