Structural Evolution and Photoluminescence of SiO2 Layers with Sn Nanoclusters Formed by Ion Implantation

Samples of SiO2 (600 nm)/Si have been implanted with Sn ions (200 keV, 5×1016 cm−2 and 1×1017 cm−2) at room temperature and afterwards annealed at 800 and 900°C for 60 minutes in ambient air. The structural and light emission properties of “SiO2+Sn-based nanocluster” composites have been studied using Rutherford backscattering spectroscopy, transmission electron microscopy in cross section and plan-view geometry, electron microdiffraction, and photoluminescence (PL). A strict correspondence of Sn concentration profiles and depth particle distributions has been found. In the case of 1×1017 cm−2 fluence, the impurity accumulation in the subsurface zone during the thermal treatment leads to swelling and to the formation of dendrites composed of large and coalesced nanoparticles of grey contrast. The appearance of dendrites is most probably due to the SnO2 phase formation. The as-implanted samples are characterized by a weak emission with maximum at the blue range (2.9 eV). The PL intensity increases by an order of magnitude after annealing in an oxidizing atmosphere. The narrowest and most intense PL band has maximum at 3.1 eV. Its intensity increases with increasing fluence and annealing temperature. This emission can be attributed to the formation of the SnO2 phase (in the form of separate clusters or shells of Sn clusters) in the subsurface region of the SiO2 matrix.

Electron microdiffraction reveals the nanoscale twist geometry of cellulose nanocrystals

Electron microdiffraction revealed the nanoscale twist geometries of cellulose nanocrystals under both cryogenic and dry conditions.

Synthesis and Characterization of Hybrid Core-Shell Fe3O4/SiO2 Nanoparticles for Biomedical Applications

The creation of markers that provide both visual and quantitative information is of considerable importance for the mapping of tissue macrophages and other cells. We synthesized magnetic and magneto-fluorescent nanomarkers for the labeling of cells which can be detected with high sensitivity by the magnetic particle quantification (MPQ) technique. For stabilization under physiological conditions, the markers were coated with a dense silica shell. In this case, the size and zeta-potential of nanoparticles were controlled by a modified Stober reaction. Also, we developed a novel facile two-step synthesis of carboxylic acid-functionalized magnetic SiO2 nanoparticles, with a carboxyl polymer shell forming on the nanoparticles before the initiation of the Stober reaction. We extensively characterized the nanomarkers by transmission electron microscopy, electron microdiffraction, and dynamic and electrophoretic light scattering. We also studied the nanoparticle cellular uptake by various eukaryotic cell lines.

Morphology of γ′-Phase in Ni-Al Superalloy at High-Temperature Annealing

Phase composition and γ′-phase morphology of a superalloy on based N I-Al doped by high-melting elements in it after ordering annealing hawe been studied by TEM, SEM and electron microdiffraction methods. It is revealed that after annealing superalloy comprises mainly γ′-phase (∼90%). The structure, distribution and morphology of γ′-phase is determined.