Yoshinobu Nakamura

Background: Ion-sensitive field-effect transistors (ISFETs) can measure the concentration of specific ions in solutions, by attaching ion-sensing membranes proposed for ion-selective electrodes (ISEs) to their gate surfaces. Numerous organic ion-sensing membranes for ISEs have been developed. However, the adhesion between the ion-sensing membranes and the gate surfaces is poor, therefore, adversely affecting the potential responses of ISFETs. Methods: New adhesive solutions to attach the ion-sensing polyvinyl chloride (PVC) membranes to the gate surfaces of ISFETs have been developed. The proposed adhesive solutions were made in tetrahydrofuran (THF) from polymer blends containing PVC and paraloid B-72 in different ratios. Results: It was found that the adhesive solution with a composition ratio of PVC: Paraloid B-72 = 10:90 provided particularly good adhesion and the best slope of the potential response to Na+-activity change. The best ion selectivity for the Na+ ion was exhibited by ISFET with the adhesive solution having a composition ratio of PVC: Paraloid B-72 = 20:80. Discussion:: The results of the tensile test indicated that the PVC components in the adhesive solutions may not be directly involved in adhesion to the gate surface of the ISEFTs. The adhesive solution consisting of only PVC content provided the worst slope of the potential response to Na+-activity change. Conclusion: The ion-sensing PVC membranes were stably attached using the proposed adhesive solutions on the gate surfaces of the ISFETs. By using the proposed adhesive solution, the ISFETs with the ion-sensing PVC membranes showed good potential responses.

Circularly polarized luminescence (CPL) has emerged as a key optical property with chiral‐photonic and optoelectronic applications. However, conventional CPL systems rely on synthetically demanding chiral luminophores that emit at fixed wavelengths, which limits tunability and efficiency. In this study, we demonstrate that achiral or racemic luminophores co‐encapsulated with photosensitizers in the helical nanocavities of chiral silica exhibit upconversion CPL (UC‐CPL). The chiral silica, which is derived from polymethylvinylsiloxane comprising polyhedral oligomeric silsesquioxane decorated with enantiomeric N ‐( tert ‐butoxycarbonyl)cysteine methyl ester moieties (PMVS‐POSS‐Cys), has a helical structure with a preferred‐handedness that facilitates efficient triplet–triplet energy transfer (TTET) and triplet–triplet annihilation (TTA). The resulting materials exhibit distinct CPL and UC‐CPL signals when excited at 365 and 532 nm, respectively, despite the achiral nature of the luminophore. This study unprecedentedly demonstrates UC‐CPL from achiral emitters within chiral silica matrices, which is achieved through chiral induction in the solid‐state helical silica frameworks. The strategy described herein provides a general and versatile platform for developing energy‐efficient, wavelength‐tunable chiral‐photonic materials without the need for elaborate chiral syntheses.

Circularly polarized luminescence (CPL) has emerged as a key optical property with chiral‐photonic and optoelectronic applications. However, conventional CPL systems rely on synthetically demanding chiral luminophores that emit at fixed wavelengths, which limits tunability and efficiency. In this study, we demonstrate that achiral or racemic luminophores co‐encapsulated with photosensitizers in the helical nanocavities of chiral silica exhibit upconversion CPL (UC‐CPL). The chiral silica, which is derived from polymethylvinylsiloxane comprising polyhedral oligomeric silsesquioxane decorated with enantiomeric N ‐( tert ‐butoxycarbonyl)cysteine methyl ester moieties (PMVS‐POSS‐Cys), has a helical structure with a preferred‐handedness that facilitates efficient triplet–triplet energy transfer (TTET) and triplet–triplet annihilation (TTA). The resulting materials exhibit distinct CPL and UC‐CPL signals when excited at 365 and 532 nm, respectively, despite the achiral nature of the luminophore. This study unprecedentedly demonstrates UC‐CPL from achiral emitters within chiral silica matrices, which is achieved through chiral induction in the solid‐state helical silica frameworks. The strategy described herein provides a general and versatile platform for developing energy‐efficient, wavelength‐tunable chiral‐photonic materials without the need for elaborate chiral syntheses.

The network structure and reactivity of suitable restoration agent consisting of silane coupling agents (SCAs) of the brittle walls of a cultural heritage site located underground in a desert area in Egypt were investigated using ¹H pulsed nuclear magnetic resonance (pulse NMR). It should possess both high coagulation strength and ductility to ensure that it can withstand an earthquake; it should also contain ethoxy rather than methoxy groups, which generate toxic methanol. The solidification rate for the SCA or oligomer with ethoxy groups was lower than those with methoxy groups; however, the final polycondensates showed the same relaxation time (hardness). The difference spectrum was developed newly to analyze the network structure combined higher strength and ductility. The distribution of crosslinking degree of such polycondensates was narrow, and the amount of lower crosslinking degree was small. On the other hand, the distribution was wide in the polycondensates with ductility but lower strength. From the compression tests of model sand solidified with the restoration agent for both methoxy and ethoxy types showed the superior properties combined higher strength and ductility. The pulse NMR experiment was useful for estimating the solidification rate and the network structure.

To clarify the formation mechanism of front frame‐type morphology, the stringiness of crosslinked random copolymers of poly(n‐butyl acrylate‐acrylic acid) during a 180° peel test with a constant tensile rate was examined for various crosslinker contents and rates using a quartz adherend. Cohesive failure occurred for lower crosslinker content and rate, whereas interfacial failure with sawtooth‐type stringiness without a frame was observed for higher crosslinker content and rate. Front frame‐type stringiness was formed at the boundary of cohesive and interfacial failures. To clarify the formation mechanism, observation was conducted from the start of peel test until the equilibrium state. The sawtooth‐type stringiness with branches first formed at the tip. The adjoining branches were connected and the 2D frame was formed only on the adherend surface. The formed 2D frame developed toward the 3D walls and the front frame‐type was then completed. This is caused by the surface tension that acts to restrain the increase in the surface area. However, the surface area of the front frame‐type morphology was larger than the no frame‐type. The larger absorption of peeling stress by the formation of this morphology is expected to contribute to peel strength improvement.

For a probe tack test for a pressure‐sensitive adhesive (PSA) under the conditions of light contact pressure and short contact time, probes with shapes and surface roughnesses suitable to achieve better wettability were investigated. A smooth, polished probe that became slightly convex at its center was found to be superior to flat‐ended. High surface roughness decreased tack. Debonding observations showed that fibrillation started from the probe edge and extended to the center. The fibril grew, without peeling, until the peak of the force–displacement curve was reached. After the peak, the fibril growth and peeling advanced simultaneously. The fibrillation was important to tack development. The test conditions necessary to observe the deformation behavior of PSA tape with sufficient interfacial adhesion were investigated. The system was preheated at 60°C for 1 h after the probe and PSA tape contacted each other, and was then cooled. The PSA performance of crosslinked random copolymers poly(n‐butyl acrylate‐acrylic acid) (A) and poly(2‐ethylhexyl acrylate‐acrylic acid) (B) were compared. A shoulder formed by fibrillation after the peak in the force–displacement curve was observed only for B. Copolymer B exhibited better interfacial adhesion and deformability. The preheating method was found to be useful for characterizing PSAs.

The optimal restoration agent for the brittle walls of Idout's tomb built 4400 years ago in Saqqara, Egypt, which is located underground in a desert area, was investigated. From x‐ray diffraction analysis of the sand collected near the tomb, the main ingredient is silica. Alkoxysilane and its oligomer are used because its alkoxy groups can react readily with silica. The compressive test of solidified model sand its main component is silica was done. The increase of both molecular weight of oligomer and the content of oligomer with higher molecular weight effectively developed the compressive force. When an earthquake occurs, it is desirable that the reinforced wall will be crushed in ductility. The addition of di‐alkoxy type alkoxysilane to oligomers changed the failure mode from brittle to ductile, because the network becomes looser. When a moderate quantity of di‐alkoxy type is added to oligomers, the solidified model sand deforms with greater displacement, while maintaining a high compressive force. From scanning electron microscopic observation of fractured solidified specimen, alkoxysilane was making the sand particles connect as a binder. Many cracks were clearly observed in the binder layer. Whereas, the formed crack was far smaller for di‐alkoxy added system.

In a blend of acrylic block copolymer consisting of poly(methyl methacrylate) and poly(n‐butyl acrylate) blocks and a special rosin ester resin (RE) tackifier as a model pressure‐sensitive adhesive (PSA), RE exists in two states: as nm‐sized agglomerated particles (A) and as dissolved molecules (B). The effect of A and B ratio on the PSA properties were investigated using REs with four different weight‐average molecular weights (M_ws) in the range from 680 to 1700. The formation of A increased with increasing of M_w because of lowering of miscibility. The glass transition temperature increased with increasing of M_w. The tack at lower temperatures and the fracture energy were improved by B, whereas the tack at higher temperatures was improved by A. A and B enhanced the cohesive strength and the wettability of PSA, respectively. However, the improvement of cohesive strength by the RE with highest M_w was remarkably low. This seems to be caused by the larger size of agglomerated particles. ¹H pulse nuclear magnetic resonance analysis was useful for estimating the degree of A formation. The model PSA investigated in this study was nanocomposite‐like.