Mechanochromism,Twisted/Folded Structure Determination,and Derivatization of (N‐Phenylfluorenylidene)acridane

(N‐Phenylfluorenylidene)acridane (Ph‐FA) compounds with electron‐withdrawing and ‐donating substituents (H, MeO, Ph, NO₂, Br, F) at the para position of the phenyl group were successfully synthesized by Barton–Kellogg reactions of N‐aryl thioacridones and diazofluorene. By using the substituent on the nitrogen atom to alter the electronic properties, both the folded and twisted conformers of p‐NO₂‐C₆H₄‐FA could be crystallographically characterized, which enabled the charge transfer from the electron‐donating acridane moiety to the electron‐accepting fluorenylidene moiety to be understood. Ground‐state mechanochromism, thermochromism, vapochromism, and proton‐induced chromism were demonstrated between the folded and twisted conformations of the conformers. Protonation and chemical oxidation of Ph‐FA gave two stable acridinium compounds, namely, the fluorenylacridinium and acridinium radical cations. The present study will contribute to the development of functional dyes and organic semiconductors.     

Direct Estimation of the Surface Location of Immobilized Functional Groups for Concerted Catalysis Using a Probe Molecule

The location of active sites during concerted catalysis by a metal complex and tertiary amine on a SiO₂ surface is discussed based on the interaction between the functionalized SiO₂ surface and a probe molecule, p‐formyl phenylboronic acid. The interactions of the probe molecule with the surface functionalities, diamine ligand, and tertiary amine, were analyzed by FT‐IR and solid‐state ¹³C and ¹¹B MAS NMR. For the catalyst exhibiting high 1,4‐addition activity, the diamine ligand and tertiary amine base exist in closer proximity than in the catalyst with low activity.     

Biohybrid Organic Heterostructure Based on Chlorophyll-Bacteriochlorophyll Aggregates for Ecofriendly Hydrogen Production

Hydrogen energy is an abundant, clean, sustainable and environmentally friendly renewable energy source. Therefore, the production of hydrogen by photocatalytically splitting water on semiconductors has been considered in recent years as a promising and sustainable strategy for converting solar energy into chemical energy to replace conventional energy sources and to solve the growing problem of environmental pollution and the global energy crisis. However, highly efficient solar-driven photocatalytic hydrogen production remains a huge challenge due to the poor visible light response of available photocatalytic materials and the low efficiency of separation and transfer of photogenerated electron-hole pairs. In the present work, organic heterojunction structures based on bacteriochlorophyll (BChl) and chlorophyll (Chl) molecules were introduced and used for solar-driven photocatalytic hydrogen production from water under visible light. Also, noble metal-free photocatalyst was successfully constructed on Ti₃C₂T_x nanosheets by simple successive deposition of Chl and BChl, which was used for the photocatalytic splitting water to hydrogen evolution reaction (HER). The results show that the optimal BChl@Chl@Ti₃C₂T_x composite has a high HER performance with 114 μmol/h/g_cat, which is much higher than the BChl@Ti₃C₂T_x and Chl@Ti₃C₂T_x composites.     

Time operators for quantum walks

Letters in Mathematical Physics - We study time operators for discrete-time quantum systems. Quantum walks are typical examples. We construct time operators for one-dimensional homogeneous quantum...     

Fabrication of Carbon Nanotube Thin Films for Flexible Transistors by Using a Cross-Linked Amine Polymer

Owing to their remarkable properties, single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) are expected to be used in various flexible electronics applications. To fabricate SWCNT channel layers for TFTs, solution-based film formation on a self-assembled monolayer (SAM) covered with amino groups is commonly used. However, this method uses highly oxidized surfaces, which is not suitable for flexible polymeric substrates. In this work, a solution-based SWCNT film fabrication using methoxycarbonyl polyallylamine (Moc-PAA) is reported. The NH₂-terminated surface of the cross-linked Moc-PAA layer enables the formation of highly dense and uniform SWCNT networks on both rigid and flexible substrates. TFTs that use the fabricated SWCNT thin film exhibited excellent performance with small variations. The presented simple method to access SWCNT thin film accelerates the realization of flexible nanoelectronics.     

Supramolecular Sensor for Astringent Procyanidin C1: Fluorescent Artificial Tongue for Wine Components

An artificial tongue that detects astringent components for a comprehensive evaluation of taste has not been established to date. Herein, we first propose fluorescent polythiophene (PT) derivatives ( S1 – S3 ) modified with 3-pyridinium boronic acid as supramolecular chemosensors for wine components including astringent procyanidin C1. After numerous attempts for the synthetic conditions, more than 95 mol % of the PT unit was modified with the pyridinium boronic acid moiety. To evaluate the PT derivatives as chemosensors of the artificial tongue, qualitative and quantitative analyses were performed with four types of wine components (i.e., sweet, sour, bitter, and astringent tastes) in combination with pattern recognition models. Notably, procyanidin C1 in the actual wine sample was successfully detected in a quantitative manner. In other words, we have established an authentic artificial tongue using PT based supramolecular chemosensors.     

Safety Evaluation of Far-UV-C Irradiation to Epithelial Basal Cells in the Corneal Limbus

Basal cells in the corneal limbus play an important role in the turnover cycle because they are the source of all cells that constitute the corneal epithelium. We examined the penetration depth of ultraviolet (UV) light in the corneal limbus and assessed the safety of Far-UV-C on stem cells in the basal area of the corneal limbus. Rats were irradiated with UV at peaks of 207, 222, 235, 254 and 311 nm while under anesthesia. The UV penetration depth in the rat corneal limbal epithelium was wavelength dependent: 311 nm UV-B and 254 nm UV-C reached the basal cells of the epithelium, and 235 nm radiation reached the middle area; however, 207 and 222 nm UV-C reached only the superficial layer of the epithelium. Porcine cornea, which is similar to the human eye in size and structure, were irradiated with 222 and 254 nm UV-C. As in rats, 222 nm UV-C reached only the superficial layer of the porcine corneal limbal epithelium. These results indicate that Far-UV-C, such as radiation of wavelengths of 207 and 222 nm, could not reach corneal epithelial stem cells, i.e. the cells remained intact. It is unlikely that the turnover of the corneal epithelium is obstructed or disrupted by exposure to Far-UV-C.