Large Absorption Peak Research Articles

Optical Study of Tb2(MoO4)3 Crystal

Some optical properties for a novel ferroelectric and ferroelastic multiferroic material Tb2(MoO4)3 crystal have been studied. The transmission spectrum of Tb2(MoO4)3 reflects the band gap is about 3.76 eV and a large absorption peak at 486 nm is observed. The photoluminescence of the Tb2(MoO4)3 is measured and the peaks at 490 nm, 540 nm, 580 nm, 615 nm respectively are now observed. These peaks are attributed to the electronic transitions of Tb3+ ions. The strongest photoluminescence intensity is excitated by the light of 486 nm which is mainly caused by the energy absorption at 486 nm indicated in transmission spectrum. The Raman spectrum of the Tb2(MoO4)3 is observed and the vibration modes corresponding to the phonon peaks are analyzed.

Thermo- and Solvent-Responsive Polymer Complex Created from Supramolecular Complexation between a Helix-Forming Polysaccharide and a Cationic Polythiophene

The helical structure is one of key structural components for both biological systems and artificial chiral systems. So far, we have succeeded in fabricating "tight" insulated molecular wires consisting of a triple-stranded cohelical structure formed through supramolecular wrapping of synthetic polymers by a helix-forming polysaccharide (schizophyllan). Herein, we have designed a new modified polysaccharide (Cur-oeg) to form a "loose" macromolecular complex with a conjugated polymer (CP) that allows structural changes in response to external stimuli. Cur-oeg forms a helical complex with an achiral cationic polythiophene (PT1), and the effective conjugation length is changed by temperature, showing a large absorption peak shift from 403 to 482 nm between 85 and 5 °C. According to the change in the conjugation system, the fluorescence and the induced circular dichroism show the continuous spectral shifts under temperature control. The color changes in the absorption and the fluorescence are detectable with observation by the naked eye and are reversibly controlled under thermal cycles, indicating that this system has the function of a "molecular thermometer". It is shown that the induced thermoresponsiveness is associated with structural rearrangement of the helical conformation of PT1 in the complex. Moreover, another unique responsiveness is discovered for the film state: that is, the film color is varied when it is exposed to the vapor of water or methanol (vaporchromism), resulting from the structural change of PT1 occurring even in the film state. These flexible molecular motions in both the solution state and the film state can be applicable to the design of CP-based smart sensors, polarized materials, switching devices, etc.

Strong plasmon absorption in InN thin films

We have fabricated InN thin films using rf magnetron sputtering from an indium (In) metal target. Optical and electrical measurements show that these as-grown films are n-type with carrier concentrations ranging from 1020 to 1021 cm−3. This variation in carrier density is produced by controlling the conditions during the deposition. We used Rutherford backscattering spectrometry to identify possible sources for n-type carriers. We found that in addition to strong direct bandgap optical absorption ranging from 1.4 to 2.0 eV, a large plasmon absorption peak in the infrared region (0.45–0.8 eV) is also observed. This tunable IR absorption suggests that these highly degenerate InN films could be used for a number of applications, including optical filters and infrared devices.

Microstructures and Optical Properties of LiNbO3 Sequentially Implanted with Ag and Cu Ions

Microstructures of LiNbO3 sequentially implanted with Ag and Cu ions were investigated in connection with changes in optical properties induced by heat treatment. Ag and Cu ions were implanted into LiNbO3 single crystals at energies of 4.2 and 3.0 MeV, respectively, to ensure an overlap of the depth distribution for both metals. Samples were heated in air for 1 h at temperatures up to 800 °C, and the optical absorption spectra of the samples were measured in the visible region. For the as-implanted samples, two large absorption peaks appeared at 473 and 574 nm, which correspond to absorptions due to the surface plasmon resonance of Ag and Cu nanoparticles, respectively. When the sample was heated at high temperatures, the intensities of the absorption peaks gradually decreased. After being heated at 500 °C, the spectra showed only one peak at 550 nm. For the sample heated at 800 °C, the absorption peak almost disappeared, and the samples became colorless. Changes in the microstructure induced during the annealing processes were examined by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX).

Optical Properties of Quartz Implanted with V Ions

V ions were implanted into quartz (single crystals of SiO2) at doses of 3 ×1016–1 ×1017 ions/cm2 at 20 keV. The changes in the optical properties and microstructures were measured while annealing the sample in air at temperatures up to 800 °C. For the as-implanted sample, nanoparticles including V in the metallic state were confirmed to be formed in the implanted layer. The absorption spectrum showed a tendency of monotonic increase toward short wavelengths. When the samples were heated at the temperature range of 450–650 °C in air, a large and narrow absorption peak was observed at approximately 402–418 nm with the tendency to shift toward longer wavelengths as the temperature increased. After heating at 500 °C, the surface of the sample was yellow-green. The micromorphology of the surface was slightly roughened after heating with randomly dispersed microcrystals and concavities. Bleaching of this color occurred when the sample was heated at 550 °C for 30 h or at 700 to 800 °C for 1 h. The surface of the sample heated at 800 °C was found to be flat, and some nanoparticles were still observed in the surface layer. The chemical state of V in the implanted layer of the as-implanted sample was metallic, and after heating at 500 or 800 °C the core line of V 2p3/2 was shifted by about 2.7 eV from that of the metallic state. The binding energy of V 2p3/2 was 515 eV, which corresponds to that of vanadium oxides.

Coloration Related to Nanostructure of Yttria-Stabilized Cubic Zirconia Single Crystal Implanted with Ag Ions

Ag ions were implanted into single crystals of yttria-stabilized cubic zirconia (YSZ) at 1.5 MeV to a fluence of 2×1016 ions/cm2. After implantation, heat treatments were performed at 500, 900, and 1000 °C in air. The surface color tone markedly changed from brown to a beautiful violet after heat treatments. Scanning transmission electron microscope (STEM) observations revealed that Ag nanoparticles were formed when samples were heated at temperatures higher than about 900 °C. The absorption spectrum in the visible region was measured. A large absorption peak appeared at 510 nm after heating at 900 °C. The peak could be attributed to the surface plasmon resonance of Ag nanoparticles.

Femto Second Laser Pulse에 의한 유리의 결정화 및 기계적 특성

Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness, as compared with the original glass. This improvement is due to the microstructure consisting of very small crystals. In this study, Ag-doped 45SiO₂-24CaO-24Na₂O-4P₂O 5 glasses were irradiated to strengthen by the crystallization using Femto second laser pulses. Through the UV/VIS spectroscope, XRD, Nano-indenter and SEM etc., heat-treated and irradiation of laser pulses without heat-treated samples were analyzed. Two kinds of samples, heat-treated and laser irradiated without heat-treated samples, showed the peaks in the same wavelength near 360 nm. Especially, samples irradiated by 140 mW laser with XYZ stage having at the rate of 100~1000 μm/s had the largest absorption peak among them, and heat-treated samples was shown lower absorption range than over 90 mW laser irradiated samples. Moreover, samples irradiated by laser had higher values (4.4~4.56×10 -3 (Pa)) of elastic modulus which related with strength of glass than values of heat-treated samples and these are 1.2~1.5 times higher values than them of mother glass.

Optical properties of YSZ implanted with Ag ions

Ag ions were implanted into YSZ (yttria stabilized cubic zirconia) single crystals in both keV and MeV energy regions. For samples with 6 × 10 16 ions/cm 2 at 20 keV, a large absorption peak appears at 536 nm. This absorption peak gradually decreases with increasing temperature. For samples implanted at 3 MeV, a broad absorption peak at around 430 nm was observed. The absorption gradually decreases with increasing temperature, and the sample turns colorless at 700 °C. As the sample is further heated at higher temperatures of 800–1000 °C, a new absorption peak appears at 520 nm and grows with the heating time. This peak appears after several minutes heating at 1000 °C. This absorption peak at 520 nm dose not appear after heating in an Ar atmosphere.

Absorption in the visible region of YSZ implanted with Ag ions

Ag ions were implanted into YSZ (yttrium-stabilized (cubic) zirconia) single crystals in two different energy regimes: kiloelectron volt and megaelectron volt. Optical absorption spectra were measured in the visible region at each stage in the annealing process of the sample. Depth profiles of Ag for the samples implanted at the energy of 20 keV were measured by X-ray photoelectron spectroscopy (XPS). For the samples implanted with Ag at the low energy of 20 keV, one large absorption peak appeared in the wavelength ranging from 470 to 536 nm, depending on the dose of Ag ions. As the sample was heated to 1000°C, the intensity of the absorption peak decreased gradually, but a small, broad peak remains even at the temperature of 1000°C. For the samples implanted with 2.8×10 16 Ag ion cm −2 at the high energy of 3 MeV, one broad absorption peak was observed at around 470 nm. As the sample was heated sequentially to high temperatures, the peak gradually decreased and almost disappeared at 400°C. When the sample was further heated to even higher temperatures, the absorption peak at 514 nm reappeared at 1000°C and grew with heating time.

Absorption in the visible region of LiNbO3 sequentially implanted with Ag and Cu ions

Ag and Cu ions were implanted sequentially into LiNbO3 at different ratios of Cu and Ag ions, and in two different energy regimes: kiloelectron volt and megaelectron volt. Optical absorption spectra were measured in the visible region at each stage in the process of annealing the sample. For the samples implanted sequentially with Ag and Cu ions at the low energy of 20 keV, only one peak appeared between 430 and 630 nm, the position of which depended on the ratios of Ag and Cu ions. For the samples implanted at high energies of 3 or 4.2 MeV, two large and distinct absorption peaks were observed at 480 and 590 nm. When the samples were heated to high temperatures, the peak at 480 nm ascribed to colloids of Ag shifted gradually to longer wavelengths and reached 530 nm, whereas the red shift of the peak ascribed to colloids of Cu was approximately 15 nm. Cu atoms diffuse out of the doubly implanted layer faster and at lower temperatures compared with Ag, even when Cu ions were implanted deeper than the Ag.

Splitting of the soft mode in a double well potential of SbSI

Our latest results for ferroelectric phase transition in SbSI are presented. The electronic potential of the soft B 1u mode above Tc at Sb site is of the form of a double well. Under the influence of the anharmonicity, the threefold splitting of the frequency of the local normal vibration of the Sb atom is obtained. The vibration of the lowest frequency, ω3, (and the highest oscillator strength) is the true soft mode which lies at millimeter waves. The higher frequency, ω2, is also temperature dependent. They all three overlap and show large absorption peak accompanied by the deep dielectric dispersion in millimeter and far IR region.

Origin of ferroelectricity in SbSI

There are three phases in the phase diagram of SbSI: ferroelectric (T < 298 K), antiferroelectric (298 < T < 410 K) and paraelectric (T > 410 K). In the antiferroelectric phase the arrangement of the polar chains becomes antiparallel (up and down). It causes a disorder of the Sb atoms. Ferroelectricity and phase transitions in SbSI are closely related to its electronic structure and phonon interaction. The disorder results in an asymmetric double-well soft-mode potential. It leads to threefold splitting of the soft mode frequency. They all show large absorption peak and deep dielectric dispersion in millimeter and far IR region.

Quantum confined Stark effect in GaInAsSb/AlGaAsSb quantum wells grown by molecular beam epitaxy

The quantum confined Stark effect in GaInAsSb/AlGaAsSb strain compensated multiquantum well structures grown by molecular beam epitaxy on GaSb substrates has been successfully demonstrated for the first time. A large absorption peak shift up to 80 nm was observed. The excitonic absorption peak shifts agree well with the calculated results.

Optical properties of LiNbO3 implanted with Ag ions

Ag ions were implanted in LiNbO3 at energies of 25 keV and 3 MeV. Optical absorption spectra were measured in the visible range. A large absorption peak due to small colloidal Ag metal was observed at 460 and 510 nm for the as-implanted sample at 3 MeV and 25 keV, respectively. Subsequently, the samples were heated in air up to 600 °C. The absorption peak moved toward longer wavelengths up to 560 nm when the sample was heated at high temperature. Small droplets of metallic Ag expelled from the implanted layer formed on the surface of the sample even when the samples were held at room temperature. The number and size of the droplets grew with time and their growth was accelerated when the samples were heated at high temperature.

Optical characteristics of LiNbO3 implanted with Au+ ions

Optical characteristics of LiNbO3 implanted with Au+ ions at energy of 23 keV were studied. The color of the surface of the LiNbO3 was changed to blue-green and a large absorption peak around 620 nm was observed. The surface morphology was also found to change with time. Metallic Au dots were observed on the surface after implantation and grew from day to day when the samples were held at room temperature. The absorption peak produced by Au+ implantation was relatively stable toward thermal treatment compared to that of Cu+ implantation into LiNbO3. But as the sample was heated at temperatures higher than about 500 °C, this peak gradually decreased and finally disappeared. These characteristics were explained fairly well by the behavior of Au colloids formed in the surface layer of LiNbO3.

Estimate of Hubbard U for C60 by use of optical absorption.

We consider the optical absorption of ${\mathrm{C}}_{60}$ within a simple tight-binding model. To obtain a reasonable agreement with experiment a sizable Hubbard U must be included. We estimate U to be in the range from one-half to the full ``bandwidth'' where the bandwidth is roughly 13 eV. In our picture the two lowest-energy large-absorption peaks are due to single-particle transitions: ${\mathit{H}}_{\mathit{u}}$ goes to ${\mathit{T}}_{1\mathit{g}}$ and ${\mathit{H}}_{\mathit{g}}$ goes to ${\mathit{T}}_{1\mathit{u}}$, respectively. The weak absorption from 3.0 to 1.9 eV is attributed to the dipole-forbidden transition: ${\mathit{H}}_{\mathit{u}}$ goes to ${\mathit{T}}_{1\mathit{u}}$ ``split'' by electron-electron repulsion.

Tumoricidal capacities of macrophages photodynamically activated with hematoporphyrin derivative.

Four days after administration to mice of small amounts (30-600 ng/mouse) of hematoporphyrin derivative (HPD), peritoneal macrophages exhibited a greatly enhanced Fc-receptor mediated phagocytic capacity as assayed by ingestion activity of IgG-coated sheep erythrocytes. Much higher doses (greater than 3000 ng/mouse) did not have this effect. The peritoneal macrophages activated by administration of HPD have tumoricidal capacity for IgG-coated retinoblastoma cells. We then studied in vitro photodynamic activation of macrophages by white and red fluorescent light irradiation of mouse peritoneal cells (mixture of macrophages and B and T lymphocytes) in media containing very low concentrations of HPD. A short (5 s) white fluorescent light exposure (1Wm-2) of peritoneal cells in a medium containing 0.03 ng HPD/mL produced the maximal level of ingestion activity of macrophages. A 15 s red fluorescent light exposure (1Wm-2) of peritoneal cells in a medium containing 0.1 ng HPD/mL produced the maximal level of ingestion activity of macrophages. Thus, photodynamic activation of macrophages with white fluorescent light is more efficient than that with red fluorescent light. This can be explained by the fact that HPD has a large absorption peak at about 364 nm which extends into the visible range, and decreasingly smaller absorption bands at 500, 535, 570 and 630 nm. In vitro photodynamically activated macrophages showed efficient tumoricidal activity regardless of the type (white or red) of light used. These results suggest that a low level of HPD promotes therapeutic immunopotentiation.

Radio frequency penetration depth in HTSC ceramic samples

We present measurements of the temperature dependence of the RF penetration depth δ(T) in YBa 2Cu 3O 6.9 and BiSrCaCu 2O x ceramics. We found that δ(T) closely follows the Gorter - Casimir two-fluid model at T< T c , but with an unusually high value of δ(0)=(1.5 − 10)·10 5 A ̊ , which is at least two orders of magnitude higher than reported for the London penetration depth in the HTSC. A large absorption peak in RF losses was observed at T c and for ω<10 MHz which disappears at higher frequencies. These effects are most likely caused by weakly coupled superconducting loops within ceramic HTSC.

Quantum-size effects in the electromagnetic response of small spheres

The response of small metallic spheres to an electromagnetic field has been calculated to all multipole orders in the electronic excitations. Quantum-size effects have been analysed and found important for spheres with radii less than 10 AA, where large absorption peaks are associated with electron-hole-pair excitation energies.

THE pH DEPENDENCE OF UV SPECTRUM FOR THE P‒P BONDING LINEAR OXOANION HEXAMER

Abstract The absorption spectra of the linear P[sbnd]P bonding hexamer have been measured at various pH and the presence of a new ring species with a hydroxyl ion bridge have been proposed in order to elucidate the spectral change with pH. This new compound has a large absorption peak at 298 nm and its formation constant has been determined to be log K=2.45 ± 0.05 (I=0.1–0.2, 20 ± 1°C).