Toshihiko Matsuura

Structures of Self-Assembled Monolayers versus Vacuum Deposited Films of Terthiophene

Using X-ray diffraction and Fourier-transform infrared (FT-IR) spectroscopy, we elucidated the molecular orientation in self-assembled monolayers (SAM) and vacuum deposited films of terthiophene. Terthiophene in the SAM aligns parallel to the gold substrate. On the other hand, in the vacuum deposited films, the long axis of terthiophene aligns along the normal to the surface. Although our results contradict the quantum calculations, which predict that thiophene would not interact with gold significantly, we experimentally demonstrated the interaction between terthiophene and gold. A theoretical fitting of FT-IR signals, the out-of-plane –CH and –CH=CH– vibration at 680 cm-1, revealed the SAM formation of terthiophene to be a Langmuir type of adsorption.

Enhanced Orientation in Langmuir-Blodgett Films of Tetra-tert-butyl Phthalocyanines

We report the results of structural investigations on Langmuir (L) and Langmuir–Blodgett (LB) films of tetra-tert-butyl phthalocyanine (MTBPC) containing various transition metal ions. Techniques were developed for fabricating well-ordered L-monolayers using a flow-orientation method that dramatically enhances the molecular orientation of MTBPC in L-monolayers as compared to other techniques. The dilution procedure for developing solutions enables the formation of a well-defined single L-monolayer at the air–water interface. The tilt angles of MTBPCs in the L-monolayers are estimated by the limiting area technique. The tilting structure of LB films of MTBPCs on glass substrates as measured by X-ray diffraction (XRD) method is in good agreement with the estimate obtained by the limiting area technique on the corresponding L-monolayers. An annealing procedure significantly improves the ordering of the LB films as measured by XRD.

Scanning Force Microscopic Studies of Escherichia coli Ribosomes on Solid Substrate Surface

Scanning force microscopy (SFM) was used to image ribosomes and ribosomal subunits isolated from Escherichia coli. Topographic images of ribosomal particles adsorbed on a mica surface were obtained directly. At 80 nM, the ribosomes aggregated. At ≤8 nM, a sparser coverage was achieved, with single ribosomes isolated from one another. Although the obtained height was significantly lower than the diameter measured by X-ray diffraction, the height histogram revealed that the observed ribosomal particles belong to three height distributions: approximately 4, 9 and 11 nm. These three distributions correspond to the 70S ribosome, and the 50S and 30S ribosomal subunits, respectively. This work demonstrates that SFM is useful in the discrimination of very small amounts of ribosomal particles on a solid substrate surface.

Atomic Force Microscopic Observation of Escherichia coli Ribosomes in Solution

Ribosomes of Escherichia coli were visualized in buffer solution by atomic force microscopy (AFM). A series of time-dependent AFM images showed that ribosomes spontaneously adsorb on mica. Although ribosomes observed in air are forced to flatten on the surface, the height of ribosomal particles obtained under a physiological buffer solution is 21.8±0.5 nm, which is consistent with the ideal diameter. We succeeded in observing single ribosomes in a near-native condition.

Optical and Paramagnetic Properties of Size-Controlled Ink Particles Isolated from Sepia officinalis

The optical and paramagnetic properties of size-controlled ink particles isolated from ink sacs of Sepia officinalis were investigated. Topographic images of atomic force microscopy (AFM) revealed that the average heights of the large and small ink particles were 156 nm and 5.3 nm respectively. The ultraviolet-visible (UV-VIS) spectral features of aqueous solutions of ink particles were dependent on particle size. Electron spin resonance (ESR) spectra suggested that the ink particles are highly pure for paramagnetic species and are of reliable quality. These size-controlled ink particles are suitable for a basic study of melanin-related materials.

Temporal effect of inertial cavitation with and without microbubbles on surface deformation of agarose S gel in the presence of 1-MHz focused ultrasound

Sonoporation has the potential to deliver extraneous molecules into a target tissue non-invasively. There have been numerous investigations of cell membrane permeabilization induced by microbubbles, but very few studies have been carried out to investigate sonoporation by inertial cavitation, especially from a temporal perspective. In the present paper, we show the temporal variations in nano/micro-pit formations following the collapse of inertial cavitation bubbles, with and without Sonazoid® microbubbles. Using agarose S gel as a target material, erosion experiments were conducted in the presence of 1-MHz focused ultrasound applied for various exposure times, Tex (0.002-60 s). Conventional microscopy was used to measure temporal variations in micrometer-scale pit numbers, and atomic force microscopy utilized to detect surface roughness on a nanometer scale. The results demonstrated that nanometer-scale erosion was predominantly caused by Sonazoid® microbubbles and C4F10 gas bubbles for 0.002 s<Tex<1 s, while the number of micrometer-scale pits, caused mainly by inertial cavitation bubbles such as C4F10 gas bubbles and vapor bubbles, increased exponentially with increasing Tex in the range 0.1 s<Tex<10 s. The results of the present study suggest that cavitation-induced sonoporation can produce various pore sizes in membranes, enabling the delivery of external molecules of differing sizes into cells or tissues.

Fabrication of Langmuir–Blodgett Films of β-carotene by Flow-orientation

Using the Langmuir–Blodgett (LB) method together with the flow-orientation technique which controls the flow of a film material on the subphase, we successfully fabricated a well-ordered film of β-carotene. The surface pressure–area isotherm suggested that β-carotene in a Langmuir monolayer oriented perpendicular to the water surface. The flow-orientation method enhanced the molecular orientation in the monolayer. X-ray diffraction patterns indicated that the orientation of β-carotene in the LB films correlates with the number of layers. The films with five and nine layers yielded tilt angles of 55° and 40°, respectively. Fourier-transform infrared spectroscopy revealed that ionone rings of β-carotene in the LB film orient perpendicular to the gold substrate.

Improvement in performance of dye-sensitized solar cells with porous TiO2 electrodes using squid ink particles

A potentially appealing alternative to the traditional fabrication process of TiO2 film electrodes for dye-sensitized solar cells (DSSCs) was presented by utilizing water-soluble TiO2 composite pastes containing size-controlled ink particles (SIPs) isolated from the squid. The mixture ratios of SIPs in the paste formulations affected the photoelectric conversion efficiency (PCE). The highest PCE was achieved when the mixture ratio of SIPs was 20%. The process is highly reproducible and leads to a 35% increase in PCE compared with that in the DSSC without SIP addition. The utilization of SIPs in the fabrication of TiO2 film electrodes enhanced the performance of DSSCs.

Utilization of Size-Controlled Squid Ink Particles as Enhancer for the Porosity of Titania Electrode in Dye-Sensitized Solar Cell

TiO2 films were prepared using a paste mixture of titania and size-controlled squid ink particles that was used to manufacture macroporous electrodes in a dye-sensitized solar cell (DSSC). The sintering procedure at 450 °C decomposed the ink particles, thereby increasing the porosity of the structure in the films. An increase in the proportion of ink particles in the paste formulation increased the surface roughness of the films. The ink particles in the paste consequently enhanced the film porosity. The TiO2 films prepared using a paste mixture consisting of 30% ink particles had the roughest surface, but its DSSC had the lowest photoelectric conversion efficiency. Thus, this study revealed the effects of the paste composition on the TiO2 film morphology and DSSC performance.

Electron Spin Resonance Spectroscopic Study of Size-Controlled Ink Particles Isolated from Sepia officinalis

The paramagnetic properties of size-controlled ink particles isolated from the ink sacs of Sepia officinalis were studied by electron spin resonance (ESR) spectroscopy. Both the size-controlled ink particles and synthetic melanins seemingly yielded similar ESR spectra consisting of a singlet with a slightly asymmetrical signal. However, the progressive microwave power saturation revealed a clear difference between their paramagnetic behaviors. In comparison with synthetic melanins, the ESR spectra of the ink particles readily reached saturation, indicating a long spin–lattice relaxation time. On the other hand, the ESR linewidth depended on particle size. This implies that the particle size is related to the distance between paramagnetic species in the particles. Hence, it is reasonable that the large ink particle has the weakest spin–spin interaction among these samples. The employment of the size-controlled ink particles enabled us to determine precisely the paramagnetic parameters of Sepia inks.