The Effect of Iron Oxide Magnetic Nanoparticles on Smooth Muscle Cells

Recently, magnetic nanoparticles of iron oxide (Fe3O4, γ-Fe2O3) have shown an increasing number of applications in the field of biomedicine, but some questions have been raised about the potential impact of these nanoparticles on the environment and human health. In this work, the three types of magnetic nanoparticles (DMSA-Fe2O3, APTS-Fe2O3, and GLU-Fe2O3) with the same crystal structure, magnetic properties, and size distribution was designed, prepared, and characterized by transmission electronic microscopy, powder X-ray diffraction, zeta potential analyzer, vibrating sample magnetometer, and Fourier transform Infrared spectroscopy. Then, we have investigated the effect of the three types of magnetic nanoparticles (DMSA-Fe2O3, APTS-Fe2O3, and GLU-Fe2O3) on smooth muscle cells (SMCs). Cellular uptake of nanoparticles by SMC displays the dose, the incubation time and surface property dependent patterns. Through the thin section TEM images, we observe that DMSA-Fe2O3is incorporated into the lysosome of SMCs. The magnetic nanoparticles have no inflammation impact, but decrease the viability of SMCs. The other questions about metabolism and other impacts will be the next subject of further studies

MBE-grown Au-island-catalyzed ZnSe nanowires

ZnSe nano-wires (NWs) were fabricated on GaAs(1 1 1) and GaAs(1 1 0) substrates by the molecular beam epitaxy (MBE) technique via the vapor-liquid-solid (VLS) reaction. The size dependence of NW growth orientation was studied by varying the Au catalyst size. It was revealed that &LANGBRAC; 111 &RANGBRAC; orientation is the preferred growth direction for NWs with size ≥ 30 nm while NWs with size around 10 nm prefer to grow along the &LANGBRAC; 110 &RANGBRAC; direction, with a small portion along the &LANGBRAC; 1 12&RANGBRAC; direction. A phenomenological model based on the principle that crystalline nucleation favors the minimum of the total system energy was proposed to explain these observations. An approach to achieve vertical NWs with size around 10 nm was demonstrated on a GaAs(110) substrate. © 2005 Published by Elsevier B.V

SMD packaged ZnSSe ultra-violet schottky photodetectors with high detectivity

We report the 1/f noise and shot noise studies on molecular beam epitaxy (MBE)-grown ZnSSe UV detectors packaged in SMD leadframes for three detectors with different thicknesses of the active layer and the top electrode pad. The highest onset of reverse bias for the appearance of 1/f noise is -27.5V and the highest dark resistances at zero bias is R 0 = 3.7 × 10 13Ω. The observed difference in their noise performance implies that the increase of the thicknesses of both the active layer and the top electrode pad can significantly lower the noise levels and in turn lead to higher detectivity. The best detectivity achieved is 8.75×10 13 cmHz 1/2W -1 in a detector with an active layer of 5000 Å and a top electrode pad of Cr (50Å) / Au (8000Å).link_to_subscribed_fulltex

Control of growth orientation for epitaxially grown ZnSe nanowires

ZnSe nanowires (NWs) were grown on (111), (100), and (110)-oriented GaAs substrates by molecular-beam epitaxy via the vapor-liquid-solid reaction. The size dependence of NW growth orientation was studied by varying the Au catalyst size. Through detailed transmission electron microscopy studies, it was found that < 111 > orientation is the growth direction for NWs with size >= 30 nm, while NWs with size around 10 nm prefer to grow along the < 110 > direction, with a small portion along the < 112 > direction. These observations have led to the realization of vertical ZnSe NWs with size around 10 nm grown on a GaAs(110) substrate. (c) 2006 American Institute of Physics

Thermal diffusion studies of MBE-grown ZnSe/Fe/ZnSe and ZnS/Fe/ZnS structures

This study focused on the investigation of the thermal stability of Fe on ZnSe and ZnS matrix using secondary ion mass spectroscopy (SIMS). Sandwiched three layer source structures of ZnSe/Fe/ZnSe and ZnS/Fe/ZnS were grown on GaAs and GaP substrates, respectively, by the molecular beam epitaxy technique. The bottom II-VI layers and the Fe- sandwiched layers in these structures are single crystalline while the top II-VI layers are polycrystalline. Thermal annealing was conducted in a range covering from 320 to 550 °C. The SIMS depth profiles of the as-grown and annealed structures reveal that (1 0 0) oriented single crystalline Fe/ZnSe interface is thermally stable at temperature as high as 450 °C while its polycrystalline counterpart suffers from fast diffusion even at the growth temperature. In contrast, (1 0 0) oriented polycrystalline Fe/ZnS interface is quite stable at least up to 200 °C. For both ZnSe/Fe/ZnSe and ZnS/Fe/ZnS systems, (1 1 1) oriented structures were found to have lower thermal stability than (1 0 0) oriented ones. These results provide important findings towards the optimization of Fe-based tunneling magneto-resistance structures using a II-VI semiconductor barrier. © Published by Elsevier B.V.link_to_subscribed_fulltex

Molecular-beam-epitaxy-grown CrSeFe bilayer on GaAs(100) substrate

A novel CrSeFe bilayer structure has been fabricated on a GaAs (100) substrate by the molecular beam epitaxy technique. Microstructural characterizations have revealed that the Fe layer is a single-crystalline bcc structure with the orientation relationship of (100)Fe ∥ (100)GaAs, while the top CrSe layer shows four preferred hexagonal domains with their c axis each along one of the four upward-pointing 〈111〉 directions of the underlying Fe lattice. The magnetic hysteresis loops of this bilayer structure measured by a superconducting quantum interference device magnetometer demonstrate a strong exchange bias effect with a negative exchange bias field as high as -48.4 Oe at 5 K. The magnetization reversal process shows an abrupt transition nature at temperature from 5 to 300 K. An enhancement of the coercivity not accompanied by the exchange bias field was observed at temperature higher than and well above the blocking temperature. We have interpreted these observations based on the well-established exchange spring model for antiferromagnetic/ferromagnetic bilayer structures. © 2007 American Institute of Physics.link_to_subscribed_fulltex

Te antisite incorporation in Zn S1-x Tex thin films

We investigate Te-related intrinsic defects in Zn S1-x Tex thin films. First-principles calculations were performed for ZnS with Te as impurity atoms. The results show that the substitutional incorporation of Te in group VI sites cannot form defect states deep in the energy band gap of ZnS. On the other hand, our calculations on both Te antisite and interstitial defects result in deep-level states. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to study the chemical structures of three molecular-beam-epitaxy-grown Zn S1-x Tex samples, x {0.005,0.019,0.026}. An asymmetry was detected in the XPS spectra of both Te 3 d3 2 and Te 3 d5 2 core levels, which indicates that a small portion of the incorporated Te atoms is bonded to a more electronegative element. A peak at m z of 158 was detected in the SIMS depth profiles of these samples and its characteristics match that of TeS components of the lattice matrix. This experimental evidence strongly supports the existence of Te antisite defects in the thin films. We believe that the origin of the highly luminescent centers in Zn S1-x Tex thin films is possibly attributed to the deep-level states generated from Te anti-site incorporation. © 2005 The American Physical Society.link_to_subscribed_fulltex