Solid State Phenomena Vols. 121-123

Abstract: The solid lipid nanoparticles (SLNs) were prepared based on the phase behaviors of hot microemulsions which were quite different from normal microemulisons for the solid lipid as oil phase. The pseudoternary phase diagrams for the system Brij78/deoxycholic acid sodium (DAS)/ glycerol monostearate (GMS)/water with and without the addition of retinoic acid (RA) were obtained at 60
using home-made apparatus with temperature control. O/W and W/O region were all found in the phase diagram. The introduction of RA has increased the O/W microemulsion region greatly. GMS-SLN and RA-GMS-SLN were prepared by direct cooling of hot O/W microemulsion obtained according to the phase behaviors results. The mean particle size of GMS-SLN and RA-GMS-SLN investigated by PCS is about 10 nm. TEM images indicated that both SLNs were spherical particles with diameter about 10 nm. PCS results showed that the particle dimension was kept almost the same after three months, proving good stability of both SLNs. The study on the phase behaviors of drug-loading hot microemulsions has been proved to be very significative for the controllable preparation of SLNs which could be used as nanoscale drug delivery system (DDS) for water insoluble drugs.

Abstract: A new calibration method of frictional forces in atomic force microscopy (AFM) is suggested. An angle conversion factor is defined using the relationship between torsional angle and frictional signal. When the factor is measured, the slopes of the torsional angle and the frictional signal as a function of the normal force are used to eliminate the effect of the adhesive force. Moment balance equations on the flat surface and the top edge of a commercial step grating are used to obtain the angle conversion factor. After the factor is obtained from an AFM system, it can be applied to all cantilevers without additional experiments.

Abstract: Polyvinyl alcohol (PVA) is a unique synthetic biocompatible polymer and it has a large number of hydroxyl groups that can react with many kinds of functional groups. In the present work, nanostructured PVA/TEOS hybrids were characterized by Small-angle X-ray Scattering (SAXS) associated with Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. We have synthesized hybrids based on the reaction of PVA with tetraethoxysilane (TEOS). PVA/TEOS hybrids were also modified in the nanometer-scale by crosslinking with glutaraldehyde (GA) during the synthesis involving hydrolysis and condensation of PVA/TEOS network. FTIR spectra showed major vibration bands associated with organic-inorganic chemical groups present in the hybrid composite PVA/TEOS. XRD coupled to FTIR results have indicated the presence of semi-crystalline domains embedded in amorphous PVA matrix. SAXS results were presented as plots with experimental scattering intensity, I(q), as a function of the modulus of the scattering vector, q. SAXS curves showed quite different trend on vector q with the scattering intensity I(q) corresponding to samples PVA, PVA/GA and PVA/TEOS/GA. Pure PVA sample showed a “knee” type curve, with maximum value q=0.04 Å-1. These results have indicated different nano-ordered disperse phases for PVA, PVA/TEOS hybrid and PVA/TEOS/GA chemically crosslinked hybrid.

Abstract: The aim of this study was to characterize phospholipids bilayers deposited through Langmuir-Blodgett (LB) using Fourier Transform Infrared Spectroscopy (FTIR) and Quartz Crystal Microbalance (QCM) sensor. Phospholipids dimyristoylphosphatidylcholine (DMPC), dimyristoylphosphatidylethanolamine (DMPE), dipalmitoylphosphatidylethanolamine (DPPE) bilayers were deposited. Also, hybrid monolayer of DMPC/Cholesterol (DMPC/CHOL) was prepared. Phospholipid with concentration of 1 mg.ml-1 in chloroform solution was spread at the air-water interface of a Teflon-made LB trough containing a subphase of Milli-Q water using the single-shot method. Phospholipid monolayers were transferred onto the QCM crystal and ZnSe crystals as planar solid support for FTIR measurements using the vertical dipping method. Homogeneous molecular LB films of DMPC, DMPE, DPPE phospholipids and DMPC/CHOL hybrid were produced and characterized by isotherms (Π-area), transfer ratio (θ) and QCM frequency changes results. Also, FTIR spectra results have also indicated the surface molecular organization and packing with the presence of major vibration bands.

Abstract: Proposed advanced mechanosynthetic systems [1] require molecular tools able to bind and transfer reactive moieties with high reliability at 300 K (failure rates << 10–10 per transfer operation). Screening of a large number of candidate tools at the AM1 level enabled the identification of a structure, DC10c, that is calculated (at the B3LYP/6- 31G(d,p) level) to meet these stringent requirements when used to transfer carbon dimers to any of a target class of graphene-, nanotube-, and diamond-like structures [2]. The favorable energy of transfer (exoergic by a mean energy ≥ 0.261 aJ per dimer) results from avoidance of the generation of high-energy radical sites during dimer release by means of π-delocalization to form a strained aromatic ring on the binding face of the empty structure. These energies are compatible with transfer-failure rates ~ 10–24 per operation at 300 K, and overall failure rates << 10–10.

Abstract: MTJs of structure Si/SiO2/Ta/Ru/IrMn/CoFe/Ru/CoFe/Al-O/CoFe/NiFe/Ru with different surface roughness of bottom electrode were prepared by sputtering, and it was investigated that the dependence of TMR ratio and resistance-area product (RA) on plasma oxidation time, thickness and surface roughness of tunnel barrier, and the tunneling characteristics of junction devices through I-V curves. To get resistance of below RA 10 kΩμm2, oxidation time of 10 s for 8 Å thick Al layer was required. In this case, thickness of Al2O3 barrier layer was 12.5 ~ 14 Å. For the 13 Å thick Al2O3 tunnel barrier, TMR ratio of optimized MTJ with uniform tunnel barrier was about 45% at bias voltage of 100 mV. Also the barrier height and the barrier width fitted to Simmon's relation were 12.3 Å and 3.07 eV, respectively, and these values agreed with that of MTJ within error range. The I-V curve and TMR ratio versus bias voltage curve of MTJ with rough tunnel barrier were linear and asymmetric, respectively, but in case of MTJ with uniform tunnel barrier, these curves were non-linear and symmetric, respectively. It was confirmed that the smooth surface of bottom electrode was a basic requirement for MTJ.

Abstract: In the development of our Z-pinch plasma EUV source, xenon (Xe) is used for the background gas discharges, and a solid tin (Sn) rod is used as target material due to its potential of high convention efficiency (CE) from input electric energy to EUV radiation [1, 2]. The Z-pinch plasma was driven by pulsed current with amplitude of 30 kA and pulse duration of 110 ns. Pinhole imaging, EUV spectrograph and in-band EUV energy monitor were used to characterize the EUV emission from the Z-pinch discharge. The experimental analyses have demonstrated the CE was as high as 3% [3].