A novel anthracene-based fluorescent colorimetric sensor for the simple naked-eye diagnosis of methylmalonic aciduria

A novel molecular sensor using anthracene bearing two amidopyridines emits blue fluorescence in the presence of succinic acid and green fluorescence in the presence of malonic acid, and its fluorescence intensity increased upon binding. Using this molecular sensor, we succeeded in detecting the difference of one carbon atom between succinic acid and malonic acid with the naked-eye. Furthermore, when methylmalonic acid was dissolved in urine to provide a model system for methylmalonic aciduria, the fluorescence changed from blue to green, and methylmalonic acid was successfully detected with the naked-eye.     

Catalytic activity and regeneration property of a Pd nanoparticle encapsulated in a hollow porous carbon sphere for aerobic alcohol oxidation

A core-shell composite consisting of a palladium (Pd) nanoparticle and a hollow carbon shell (Pd@hmC) was employed as a catalyst for aerobic oxidation of various alcohols. The core-shell structure was synthesized by consecutive coatings of Pd nanoparticles with siliceous and carbon layers followed by removal of the intermediate siliceous layer. Structural characterizations using TEM and N(2) adsorption-desorption measurements revealed that Pd@hmC thus-obtained was composed of a Pd nanoparticle core of 3-6 nm in diameter and a hollow carbon shell with well-developed mesopore (ca. 2.5 nm in diameter) and micropore (ca. 0.4-0.8 nm in diameter) systems. When compared to some Pd-supported carbons, Pd@hmC showed a high level of catalytic activity for oxidation of benzyl alcohol into benzaldehyde using atmospheric pressure of O(2) as an oxidant. The Pd@hmC composite also exhibited a high level of catalytic activity for aerobic oxidations of other primary benzylic and allylic alcohols into corresponding aldehydes. The presence of a well-developed pore system in the lateral carbon shell enabled efficient diffusion of both substrates and products to reach the central Pd nanoparticles, leading to such high catalytic activities. This core-shell structure also provided high thermal stability of Pd nanoparticles toward coalescence and/or aggregation due to the physical isolation of each Pd nanoparticle from neighboring particles by the carbon shell: this specific property of Pd@hmC resulted in possible regeneration of catalytic activity for these aerobic oxidations by a high-temperature heat treatment of the sample recovered after catalytic reactions.     

Optical conductivity spectral anomalies in the off-center rattling system β-Ba8Ga16Sn30

We present optical conductivity studies of the type-I clathrate Ba8Ga16Sn30, using a terahertz time-domain spectrometer (0.3-3.0?THz). The lowest-lying spectral peak at 0.72?THz due to the Ba(2) ion's off-center vibration in the oversized cage shows a drastic and anomalous temperature dependence. Below about 100?K, the single broad peak splits into two subpeaks, and with further lowering of the temperature, the spectral shape of this so-called rattling phonon shows non-Boltzmann broadening to the point that the linewidth becomes comparable to the peak frequency. Whereas the initial splitting can be understood by assuming a multiwell anharmonic potential, the strong linewidth broadening toward low temperature cannot, since the Boltzmann factor generally sharpens the low-temperature spectra. The observed behavior suggests strong interaction between the local anharmonic phonons and other excitations.     

Physics in plasmonic and Mie scattered near-field for efficient surface-enhanced Raman scattering template

We describe the physics of the SERS based on the optical near-field intensity enhancement on the metallic (plasmonic) and the nonmetallic (Mie scattering) nanostructured substrates with two-dimensional (2D) periodic nanohole arrays. The calculation by the Finite-Difference Time-Domain (FDTD) method revealed that the optical intensity enhancement increases with the increase of the thickness of a gold film coating on the nonmetallic (dielectric) nanostructured Si, GaAs, and SiC substrates. The resonance spectrum shifts with the changes in the geometrical structure of the void diameter and inter-void distance. It was clarified that the optical intensity enhancement obtained with the gold-coated substrate is equivalent to that with a gold substrate at 70-nm thick gold coating on the dielectric substrates in this structure. The resonance spectral bandwidth for Mie scattering and plasmonic near-fields is different. Therefore, if the Stokes line of the Raman scattering is located within the resonance bandwidth, the SERS signal is enhanced proportionally to the fourth power of the electric near-field. However, if the Stokes shift is located out of the resonance bandwidth, the SERS signal enhancement is only proportional to the square of the scattered near-field.     

Ab initio molecular orbital study of Fe(CO) n (n = 1–3)

Geometry optimization was performed for the ground states of FeCO, Fe(CO)₂, and Fe(CO)₃ at various levels of ab initio calculations, and the bond lengths and dissociation energies obtained were in reasonable agreement with experimental results. The nature of bonding was studied for these molecules using a complete-active-space self-consistent-field method. From the Mulliken population analysis, it was found that the traditional donation and back donation mechanism is valid for these molecules, including Fe(CO)₃, which has a pyramidal structure. Received: 27 September 1999 / Accepted: 13 January 2000 / Published online: 19 April 2000     

N-D-labeled ionic probes for mass spectrometry

An effective ¹⁵N- and deuterium (D)-labeled 2,6-bis(oxazolin-2-yl)pyridine (pybox)-La complex based probe ionization method that produces a distinct isotopic shift was developed. The distinct isotopic shift was detected by using the newly synthesized ¹⁵N-D-labeled pybox complexes. Moreover, O-[3-(tetramethylpybox)-propyl]-hydroxylamine (oxime-TMpybox) was prepared for attachment to the carbonyl group of the target molecule. Distinct isotopic shifts and multiple charged ions were detected for various compounds having amino, thiol, carboxyl, and carbonyl groups and fullerenes, using the TMpybox ionic probe series in cold-spray ionization mass spectrometry.     

Optical and Thermal Simulator for Laser-assisted Magnetic Recording

“Laser-assisted magnetic recording”, in which a recording media is heated by a laser beam while writing data, is attracting attention as a technology that enables a recording density of 1 Tb/in.². There exists another technology for media in which the recording layer is constructed with many small projections that enable high magnetic coercivity. This is called “patterned media”. For developing hard disk drives using these methods, we developed a simulator that analyzes the optical intensity distribution from the optical head for laser-assisted recording and the temperature profile on the patterned media. The simulator calculates the optical model using the finite-difference time-domain (FDTD) method. The thermal analysis of the three-dimensional model allows fast calculations using the alternating direction implicit (ADI) method. The heat source distribution data for thermal analysis is calculated in order to use the results of optical analysis. The optical and thermal analyses of the laser-assisted recording model were investigated with the simulator.