Dynamics of SCN- ions in molten thiocyanates and aqueous solutions by Raman spectroscopy

The Raman spectra of the v ₁(CN) stretching mode of SCN^- ions have been measured in molten thiocyanates, KSCN and NaSCN, at temperatures 450-600K. The vibrational and the rotational correlation functions are calculated, and the dynamics of SCN^- ions in the molten state are compared with those in aqueous solutions of KSCN, NaSCN, and LiSCN at concentrations 1–10 mol dm^-3 and at temperatures 303–353 K. The observed vibrational correlation functions are analysed by the stochastic line shape theory of Kubo, in which homogeneous and inhomogeneous broadening are treated simultaneously. Both broadening contributions to the isotropic spectra are extracted. The homogeneous broadening is found to increase with increasing temperature in both melts and aqueous solutions; the inhomogeneous broadening remains constant in molten KSCN while it decreases in aqueous solutions. As the result, the isotropic Raman bandwidth is considered to increase with temperature in the molten state and to decrease in aqueous solutions. Rotational correlation functions of SCN^- ions in these molten salts show the behaviour of the short time inertial rotation (t ? 0·15 ps, jump angle 20°), which is a little slower than the free rotation of a single ion. The long time exponential decay of the rotational correlation functions reflects the ultimate diffusional behaviour of the ionic reorientation. The rotational relaxation rate increases with increasing temperature in both melts and aqueous solutions. The vibrational dephasing rate decreases and the rotational relaxation rate increases as the cation size increases in melts. In aqueous solutions, the vibrational dephasing rate follows the same cation dependence as that in melts, while the rotational relaxation rate decreases as the cation size increases. This seems to be a consequence of the specific local structures in aqueous electrolyte solutions.     

Gold-bead scanning near-field optical microscope with laser-force position control

We have developed a scanning near-field optical microscope with an optically trapped metallic particle that has a small diameter compared to the wavelength of visible light. In this microscope we employed spot illumination to enhance the intensity of light scattered from a probe particle so we could reduce the diameter of the probe particle to 40nm. We detected slight irregularities of the surface of the cover glass near 10-nm depth. Also, we observed gold colloidal particles on the surface of the cover glass.     

A new dual-type DMA for measuring nanoparticles emitted from combustion engines

A new dual-type differential mobility analyzer (dual-type DMA) was developed in order to detect transient number concentrations of airborne nanoparticles with diameters centralized at around 10 nm (for nuclei mode particles) and 100 nm (for accumulation mode particles) in automobile exhaust gas. The apparatus divides the gas sample into two parts, and each part is sent through one of two coaxially nested sections for analysis. For the scanning mode measurement, the nanoparticles are charged by ²⁴¹Am and their size distributions are determined by varying the applied voltage over 2 min. The transient mode measurement, on the other hand, fixes the voltages for the two sections at peaks near 10 and 100 nm in order to monitor the transient behavior of the exhaust nanoparticles. The measurement principles and design of the dual-type DMA are detailed and the results for time response experiments are presented using model nanoparticles charged by a corona charger. The transient concentrations of the nuclei mode and the accumulation mode particles from a diesel engine were shown to be detected by this method, when ²⁴¹Am was used for charging the particles.     

Sliding acceleration of water droplets on a surface coated with fluoroalkylsilane and octadecyltrimethoxysilane

Both fluoroalkylsilane (FAS) and octadecyltrimethoxysilane (ODS) were coated on oxidized silicon wafers using soaking and CVD method. Smooth coatings with Ra values of less than 1 nm were attained. The slope of the sliding acceleration against the inverse of the droplet mass showed an inflection point. That point shifted to the direction of smaller droplets with decreasing FAS ratio to ODS. The water droplets’ length was increased when the sliding velocity was increased. Fluoroalkylsilane addition to ODS increases the interaction between water and the hydrophobic surface. Results showed that the sliding acceleration of a water droplet depends strongly on the surface ratio of these silanes.     

99Ru,61Ni,57Fe,and119Sn Mössbauer studies of Heusler alloys containing ruthenium

⁹⁹Ru,⁶¹Ni,⁵⁷Fe and¹¹⁹Sn Mössbauer spectroscopic studies were made on ternary intermetallic compounds containing ruthenium, Ru_xY_3?xZ (Y=Fe, Ni; Z=Si, Sn). In the system of Ru_xFe_3?xSi, two different hyperfine magnetic fields were observed at the⁹⁹Ru nuclei (H _hf[Ru]) in the range ofx≤1.0 and the magnitude of eachH _hf[Ru] was found to decrease with an increase in the ruthenium concentrationx. Both the⁹⁹Ru and¹¹⁹Sn Mössbauer spectra of Ru₂FeSn could be analyzed with two sets of magnetically split lines. The⁶¹Ni Mössbauer spectra of Ru₂NiSn were obtained at 5 and 77 K.     

ZnO nano-rods synthesized by nano-particle-assisted pulsed-laser deposition

We succeeded in synthesizing ZnO nanorods by nanoparticle assisted pulsed-laser deposition (PLD) without using any catalyst where nanoparticles formed by condensation of ablated particles play an important role. The nanorods have an average size of about 120 nm. Stimulated emission was observed from ZnO nanorods at 388 nm by optical pumping. The size-controlling of nanorods can be achieved by controlling the size and the density of these nanoparticles. PACS 61.46.+w; 81.07.Bc; 78.66.Hf; 78.67.Bf; 81.16.Mk.     

Fabrication of LiNbO3 thin films by pulsed laser deposition and investigation of nonlinear properties

Thin films of LiNbO₃ were deposited by pulsed-laser deposition (PLD). Crystalline and transparent films were deposited on a sapphire substrate at 400 °C, in 100 mTorr of oxygen, with a fluence lower than 1.2 J/cm². Droplet free films were deposited with low ablation laser fluence by the eclipse method, and waveguide losses were 15.9 dB/cm and 3.1 dB/cm. Subsequently, second-harmonic generation (SHG) was achieved by waveguide mode phase matching. The center wavelength of the matching spectrum was 853 nm, and the full width at half maximum (FWHM) was 19 nm. PACS 42.70.Mp; 52.38.Mf; 68.55.Jk; 77.84.Dy; 81.15.-z     

Micromachining of a thin film by laser ablation using femtosecond laser with masks

A gold thin film was machined by laser ablation using a femtosecond laser with mask patterns in the shape of lines and numbers. The patterns were successfully transferred with proper focusing and laser fluence. The optimal femtosecond laser fluence to keep the line width was about 5.2 mJ/cm² on the mask, and 99 mJ/cm² on the film. The processing resolution was 13 μm, and the narrowest line width was about 4 μm.     

Evaluation of immobilized-lysozyme by means of TOF-SIMS

Evaluation of immobilized-proteins on bio-devices is important for the development of sophisticated devices. Lysozyme molecules immobilized on substrates were evaluated by means of time-of-flight secondary ion mass spectrometry (TOF-SIMS). Two types of the lysozyme-immobilized samples were prepared by controlling the binding parts, i.e., the amino groups or carboxyl groups, of the protein. The TOF-SIMS spectra of each sample were analyzed with mutual information to select fragment ions specific to each sample. According to the results, differences between the samples being immobilized in the different ways are suggested, and the surface structure of the lysozyme molecule immobilized at amino groups is determined based on three-dimensional structure of lysozyme in the Protein Data Bank.