Studies of the fluorescent products of lipid oxidation in aqueous emulsion with glycine and on the surface of silica gel

The formation of fluorescent products in the reaction of methyl linoleate hydroperoxide with glycine in aqueous emulsions correlated directly with the decrease in diene conjugation and the increase in thiobarbituric acid (TBA) reactive substances. These correlations also were reflected in the course of the oxidation of methyl linoleate in aqueous emulsions with glycine and indicated that glycine reacted with products of peroxide decomposition as opposed to intermediates of autoxidation in hydroperoxide formation. Thin layer chromatography (TLC) and selective solvent extraction demonstrated that the products of the reaction contained many substances with a fluorescent spectrum similar to those of lipofuscin pigments. When methyl esters of polyunsaturated fatty acids or other polyunsaturated lipids underwent oxidation adsorbed on silica gel particles, products with similar fluorescent spectral properties were formed illustrating that fluorescent substances were formed in a variety of reactions associated with the oxidation of unsaturated lipids.     

Preparation of Silicon Carbide and Aluminum Silicon Carbide from a Montmorillonite–Polyacrylonitrile Intercalation Compound by Carbothermal Reduction

Both silicon carbide and aluminum silicon carbide have simultaneously been obtained directly from naturally occurring aluminosilicate by carbothermal reduction for the first time. A precursor of a montmorillonite–polyacrylonitrile (PAN) intercalation compound was heated at 1700°C in Ar. For comparison, montmorillonite–carbon mixtures were similarly heated. α-SiC, β-SiC, and Al₄Si₂C₅ formed from the montmorillonite–PAN intercalation compound. Mainly α-Al₄SiC₄ was obtained with ternary carbides from the montmorillonite–carbon mixtures in addition to a large amount of β-SiC. Hence, aluminum silicon carbide formation was affected by the mixing condition of the starting materials.     

Effect of Silicon Dioxide on the Thermal Diffusivity of Aluminum Nitride Ceramics

The thermal diffusivity of AlN ceramics was significantly decreased by the addition of SiO₂. The AlN ceramics with 4 wt% SiO₂ could not be densified by pressureless sintering in the temperature range 1400° to 1800°C. The thermal diffusivity of these samples was very low because of their porous structure. The AlN ceramics containing 2, 4, and 8 wt% SiO₂ were densified by hot-pressing and also had low thermal diffusivity. In these samples, the grains of the 27R polytype that resulted from the reaction between AlN and SiO₂ were dispersed, obstructing the conduction of heat. The relation between the amount of 27R polytype and the thermal diffusivity of the AlN ceramics was determined.     

Grating-coupled surface plasmon enhanced short-circuit current in organic thin-film photovoltaic cells

In this study, we demonstrate the fabrication of grating-coupled surface plasmon resonance (SPR) enhanced organic thin-film photovoltaic cells and their improved photocurrent properties. The cell consists of a grating substrate/silver/P3HT:PCBM/PEDOT:PSS structure. Blu-ray disk recordable substrates are used as the diffraction grating substrates on which silver films are deposited by vacuum evaporation. P3HT:PCBM films are spin-coated on silver/grating substrates. Low conductivity PEDOT:PSS/PDADMAC layer-by-layer ultrathin films deposited on P3HT:PCBM films act as the hole transport layer, whereas high conductivity PEDOT:PSS films deposited by spin-coating act as the anode. SPR excitations are observed in the fabricated cells upon irradiation with white light. Up to a 2-fold increase in the short-circuit photocurrent is observed when the surface plasmon (SP) is excited on the silver gratings as compared to that without SP excitation. The finite-difference time-domain simulation indicates that the electric field in the P3HT:PCBM layer can be increased using the grating-coupled SP technique.     

Characterization of silicon dioxide films on a 4H-SiC Si(0001) face by fourier transform infrared (FT-IR) spectroscopy and cathodoluminescence spectroscopy

We used Fourier transform infrared (FT-IR) spectroscopy to characterize silicon dioxide (SiO(2)) films on a 4H-SiC(0001) Si face. We found that the peak frequency of the transverse optical (TO) phonon in SiO(2) films grown on a 4H-SiC substrate agrees well with that in SiO(2) films grown on a Si substrate, whereas the peak frequency of the longitudinal optical (LO) phonon in SiO(2) films on a 4H-SiC substrate is red-shifted by approximately 50 cm(-1) relative to that in SiO(2) films on a Si substrate. We concluded that this red-shift of the LO phonon is mainly caused by a change in inhomogeneity due to a decrease in density in the SiO(2) films. Furthermore, cathodoluminescence (CL) spectroscopy results indicated that the channel mobility of the SiC metal-oxide-semiconductor field-effect transistor (MOSFET) decreases roughly in proportion to the increase in the intensity of the CL peak at 460 and 490 nm, which is attributed to the increase in the number of oxygen vacancy centers (OVCs). FT-IR and CL spectroscopies provide us with a large amount of data on OVCs in the SiO(2) films on a 4H-SiC substrate.     

Fabrication of fluorescence tunable electrospun conjugated polycarbazole fibers containing gold nanoparticles

In this report, we demonstrate a novel way to tune the fluorescence property of electrospun conjugated polymer fibers. The basic strategy is to use a soluble precursor polymer with gold nanoparticles for electrospinning, which is then cross-linked by applying potential cycles in an electrochemical cell. Electroactive carbazole units in electrospun precursor polymer fibers were converted to conjugated polymer fibers. Since the conjugated polymer fibers can be formed, the fluorescence from the conjugated polymer fibers can be tuned by the rate of the conversion and doping of the fibers. Furthermore, the quenching of the fluorescence, which overlaps with the plasmon band of the gold nanoparticles, was observed. The quenching of the fluorescence properties of the fibers was dependent on the amount of gold nanoparticles inside the fibers.     

Aging behavior of the matrix of aluminum-magnesium-silicon alloy including carbon nanotubes

The mechanical behavior of the non-aged and the aged Al-Mg-Si alloy composites reinforced with CNTs was evaluated with tensile test and Vickers hardness test. The composites showed higher mechanical strength than the pristine Al alloy before the aging, although exhibiting lower mechanical strength after the aging. The aging treatment was ineffective to strengthen the Al-Mg-Si alloy composites reinforced with CNTs. EDS elemental mapping clarified the Mg and O concentration around CNTs. The reduction of Al oxide species formed around CNTs facilitated the Mg concentration. Due to the Mg consumption around CNTs, Mg elements in Al matrix decreased, and resulted in the incomplete matrix strengthening after the aging.     

Study of polarization phenomena in Schottky CdTe diodes using infrared light illumination

Schottky CdTe diode detectors suffer from a polarization phenomenon, which is characterized by degradation of the spectral properties over time following exposure to high bias voltage. This is considered attributable to charge accumulation at deep acceptor levels. A Schottky CdTe diode was illuminated with an infrared light for a certain period during a bias operation, and two opposite behaviors emerged. The detector showed a recovery when illuminated after the bias-induced polarization had completely progressed. Conversely, when the detector was illuminated before the emergence of bias-induced polarization, the degradation of the spectral properties was accelerated. Interpretation of these effects and discussion on the energy level of deep acceptors are presented.     

Electrochemical DNA methylation detection for enzymatically digested CpG oligonucleotides

We describe the electrochemical detection of DNA methylation through the direct oxidation of both 5-methylcytosine (mC) and cytosine (C) in 5'-CG-3' sequence (CpG) oligonucleotides using a sputtered nanocarbon film electrode after digesting a longer CpG oligonucleotide with endonuclease P1. Direct electrochemistry of the longer CpG oligonucleotides was insufficient for obtaining the oxidation currents of these bases because the CG rich sequence inhibited the direct oxidation of each base in the longer CpG oligonucleotides, owing to the conformational structure and its very low diffusion coefficient. To detect C methylation with better quantitativity and sensitivity in the relatively long CpG oligonucleotides, we successfully used an endonuclease P1 to digest the target CpG oligonucleotide and yield an identical mononucleotide 2'-deoxyribonucleoside 5'-monophosphate (5'-dNMP). Compared with results obtained without P1 treatment, we achieved 4.4 times higher sensitivity and a wider concentration range for mC detection with a resolution capable of detecting a subtle methylated cytosine difference in the CpG oligonucleotides (60mer).