Laser-induced implantation of organic molecules into sub-micrometer regions of polymer surfaces

Organic molecules adhered to the point of a micropipette were transferred onto the surface of a polymer film by pulsed laser light guided through a quartz optical fiber which was inserted into the micropipette. Controlled by a high-resolution piezoelectric driver designed for scanning probe microscopy, the distance between the micropipette point and the polymer surface was kept to a few tens of nm. After laser irradiation, the deposited molecules on the polymer surface were examined with optical transmission, fluorescence, atomic force, and scanning near-field optical microscopy. It was demonstrated that various kinds of organic molecules can be implanted into sub-micrometer regions at the surfaces of polymer films without their decomposition. The hypothetical mechanism of the molecular transfer is discussed in relation to the morphology of crystalline molecules adhered at the micropipette apertures.     

Formation of iron fine particles in a crystal lattice by the computer simulation

The growing up of the fine particles in a sapphire crystal was simulated with a computer and the expected Mössbauer spectra were calculated by considering the influence of the nearest neighbors and next-nearest neighbors to the magnetic hyperfine field of the iron atoms. The simulated spectra were compared with the Mössbauer spectra observed with a Fe-implanted sapphire and the agreement between them was satisfactory on the whole. It is also revealed that an iron atom implanted into a sapphire crystal may interact, before coming to rest, with the iron fine particles situated within 2–3 nm in the crystal.     

Cems study of corrosion on iron foil at low temperatures

Conversion electron Mössbauer measurements with a proportional counter at 6.3, 78 and 300 K have been done to investigate the corrosion of the surface of iron foils, which consists of small particles of γ-Fe₂O₃. When the average particle sizes of the corroded layer are approximately 4 and 5 nm, magnetic hyperfine splitting was observed in the spectra at 6.3 and 78 K. However, for a corroded layer composed of smaller particles, the splitting was noticed only at 6.3 K. The anisotropy constantK of the small particles was estimated using the magnetic hyperfine fields obtained from the spectra at 6.3 and 78 K.     

Application of time- and space-resolved fluorescence spectroscopy to the distribution of guest species into micrometer-sized zeolite crystals

We measured the fluorescence decays and spectra of perylene adsorbed from solution into zeolite X crystals of 2-3 microm in diameter at the level of individual crystals by the application of a microscopy method coupled with a single photon counting apparatus and a multichannel spectrophotometer. We found that both decays and spectra are particle-dependent, i.e. a particle-to-particle difference was observed for the fluorescence decay curves at a fixed loading level along with a particle-dependent spectral change due to the various contribution of excimer emission band relative to those of three monomers. These findings are due to a non-homogeneous distribution which is confirmed by the various emission intensities of perylene-loaded zeolite crystals observed by fluorescence microscopy. Previously, a homogeneous distribution of the guest between zeolite crystals has been just taken for granted and not justified by experiment. The present result suggests that commonly employed collective measurements such as UV-VIS absorption and emission spectroscopies, IR and Raman spectroscopies, and NMR of bulk zeolite powders provide only averaged results and may sometimes suffer from acquiring precise molecular level pictures.     

Spin state of Co in Al (acac)3

The spin state of Co in Al(acac)₃ was studied and the result that Co atoms are in the low-spin state in the matrix was obtained. It suggests a metalic atom in a solid solution of two kinds of tris-acetylacetone complex is in the low-spin state when these two complexes have the same crystal structure.     

A picosecond diffuse reflectance laser photolysis study on phenanthrene—pyromellitic dianhydride charge-transfer crystal

Picosecond transient absorption spectra of phenanthrene—pyromellitic dianhydride (PMDA) charge-transfer (CT) crystal were measured for the first time, and the high CT nature of the S₁ state was directly confirmed. The formation process of the CT state was completed within a few ps and dependent upon the excitation wavelength. The electronic structure and dynamics were discussed by comparing the results with those of the CT complex in solution.     

Dynamics of excited and ionic states of N,N,N′,N′-tetramethyl-p-phenylenediamine in poly(methyl methacrylate) under ablation condition

The nanosecond transient dynamics of N,N,N′,N′-tetramethyl-p-phenylenediamine in poly(methyl methacrylate) has been investigated under ablation condition. Time-resolved spectroscopic data can be interpreted in terms of the dynamics of the lowest excited singlet and triplet states and the cation of TMPD. The decay processes of all the detected transients became rapid with an increase in the laser fluence. It is shown directly that TMPD absorbs about eight 248 nm photons during a nanosecond laser pulse at the ablation threshold of 220 mJ/cm². These results are well explained by cyclic multiphotonic absorption mechanism where dopant transients work as repetitive absorbers of laser photons.     

New fluorine-substituted analogue of eticlopride with high affinity toward dopamine D2 receptors.

Aiming at the development of positron-emitting ligands with specific and high affinity toward dopamine D2 receptors in the central nervous system, we synthesized a new fluorinated eticlopride derivative. A fluorine atom was introduced at the C-4 position of the pyrrolidine ring of eticlopride, a dopamine D2 antagonist of the benzamide series. The in vitro binding affinity of this ligand toward the D2 receptor was found to be as potent as eticlopride, suggesting that the corresponding 18F-labelled compound may be useful as an in vivo radioligand for positron emission tomography.     

High-throughput screening for combinatorial thin-film library of thermoelectric materials

A high-throughput method has been developed to evaluate the Seebeck coefficient and electrical resistivity of combinatorial thin-film libraries of thermoelectric materials from room temperature to 673 K. Thin-film samples several millimeters in size were deposited on an integrated Al2O3 substrate with embedded lead wires and local heaters for measurement of the thermopower under a controlled temperature gradient. An infrared camera was used for real-time observation of the temperature difference Delta T between two electrical contacts on the sample to obtain the Seebeck coefficient. The Seebeck coefficient and electrical resistivity of constantan thin films were shown to be almost identical to standard data for bulk constantan. High-throughput screening was demonstrated for a thermoelectric Mg-Si-Ge combinatorial library.