中村 一希

Circularly polarized luminescence (CPL) has significantly increased the interest in biological fields. In this research, a water-soluble Eu(iii) complex with a helical complex structure, EuLCOOH, was incorporated in chiral DNA in aqueous solutions. The photoluminescence performance of this DNA/EuLCOOH hybrid system was investigated. Compared to EuLCOOH alone, emission intensity and emission lifetime were effectively improved in the presence of DNA. The major binding between EuLCOOH and DNA was proven to be the electrostatic interaction. Owing to this interaction, the chiral environment provided by DNA successfully induced CPL from EuLCOOH

This study investigates the electrochemical modulation of luminescence color, i.e., electrofluorochromism, of an Eu complex in a polyether solvent. The electrofluorochromic (EFC) reaction of the Eu complex occurred via a reversible redox reaction between Eu3+ and Eu2+. Initially, the intrinsically stable Eu3+ complex showed intense red photoluminescence (PL) induced by f-f transitions. After the electrochemical reduction of Eu3+ to Eu2+, broad blue PL was observed attributed to the d-f transitions in the Eu2+ complex. This distinct blue luminescence from the Eu2+ complex was attributed to the effective stabilization of the Eu2+ state by the polyether solvent. The dynamic EFC reaction that changes the valence state of the Eu ion can be potentially applied to novel chemical sensors, security devices, and display devices.

We report the circularly polarized luminescence (CPL) for [Ru(bpy)3]I2 (1) and [Ru(bpy)3][M2(ox)3] (M = Zn (2), Mn (3)). Whereas compound 1 is a simple salt of [Ru(bpy)3]2+, 2 and 3 are MOFs in which the chiral [Ru(bpy)3]2+ ions are encapsulated in a homochiral gyroidal skeleton of [M2(ox)3]2-. Whereas the solution of 1 exhibited weak CPL with a luminescence dissymmetry factor of |glum| ∼ 10-4, the CPL was significantly enhanced in solid-state 1-3 with |glum| = 2 × 10-2 for 1, 4 × 10-2 for 2, and 1 × 10-1 for 3. The enhanced CPL in 3 was attributable to an energy transfer between the homochiral guest and host in 3.

We studied a silver (Ag) deposition-based multicolor electrochromic (EC) device that can represent mirror, black, cyan, magenta, yellow, green, and transparent states reversibly. The coloration in this system is based on localized surface plasmon resonance (LSPR) of Ag electrodeposits. The size and shape of deposited Ag nanoparticles (AgNPs) are important for device coloration. Therefore, it is necessary to elucidate the LSPR band change corresponding to the morphology of AgNPs during the EC device operation to improve the colorability. In this study, dark-field microscopy (DFM) was applied to in situ observation of the changes in LSPR of AgNPs at the coloration process in the reversible Ag deposition multicolor EC device for the first time. The light scattering observation of AgNPs using DFM enabled analysis of the LSPR band over time. The obtained light scattering spectra provide detailed information on the LSPR induced by AgNPs in Ag deposition-based EC devices in comparison with conventional absorption spectrum measurements.

We have demonstrated a multicolor electrochromic device (ECD) with a novel architecture. Different typical ECDs featuring commonly two flat transparent electrodes, a double electrical layer electrode is applied to the device as the counter electrode. By this architecture, even two EC molecules with different polarities mixed in the same ECD can display their unique color, respectively. This paper reports the effect of several commonly-used quaternary ammonium salts as electrolytes on color properties of the ECD featuring a hybrid capacitor architecture. The aim is to select the suitable electrolyte to fabricate multicolor ECD with excellent color performance. Among them, the electrolyte tetraethylammonium tetrafluoroborate performs most satisfactorily attributed to its small ion size and high conductivity. This novel, easily-fabricated, and high EC performance multicolor device provides an opportunity that will develop color ECDs and expand the potential of EC technology.

A solvent-free mechanochemical treatment is used to synthesize an Eu(III) hybrid material containing Eu(D-facam)3 and tetramethylammonium acetate (TMAOAc), mechEu(D-facam)3TMAOAc. The synthesis method is efficient and the reaction occurs within 10 s. Mechanochemically prepared mechEu(Dfacam)3-TMAOAc is proven to be a bimetallic compound, in which TMAOAc functions as a bridging molecule between multiple Eu(III) complexes. Compared with Eu(D-facam)3mechEu(D-facam)3-TMAOAc exhibits ultra-high luminescence, excellent circular polarization activity and thermal stability.

A novel europium-based hybrid material, Eu(d-facam)3-TMAOAc (tetramethylammonium acetate), with ultra-high luminescence, excellent circular polarization and remarkable thermostability was prepared. Its photophysical performance was studied based on the luminescence properties and energy transfer process. Compared to Eu(d-facam)3, Eu(d-facam)3-TMAOAc exhibited much brighter luminescence and stronger circular polarization. Additionally, Eu(d-facam)3-TMAOAc well retained its structure and luminescence properties even after heat treatment at 200 °C for 24 hours, whereas Eu(d-facam)3 rapidly decomposed. Eu(d-facam)3-TMAOAc was characterized by TG analysis, elemental analysis, ESI-mass spectrometry, PXRD, and FT-IR spectroscopy. It was found that TMAOAc acted as a bidentate bridge linker with Eu(d-facam)3 at a 1 : 1 ratio. This coordination structure contributed to the excellent photophysical properties and thermal stability of Eu(d-facam)3-TMAOAc. Furthermore, Eu(d-facam)3-TMAOAc showed a high solubility in common organic solvents, and it could maintain its outstanding luminescence properties in solid as well as solution states.

Electrochemical switching of luminescence color between magenta and blue using two types of luminescent materials and electrochromic molecules was demonstrated based on the control of excited energy transfer through an electrochromic reaction. The magenta photoluminescence, due to the integration of red luminescence from the Eu(III) complex and blue fluorescence from the anthracene derivative, was reversibly modulated to a pure-blue luminescence color by an electrochemical redox reaction. Electrofluorochromism is induced by effective excited energy transfer from the Eu(III) complex to the electrochromic molecule under a redox reaction.

This paper describes overview of electrofluorochromism, which is a phenomenon that controls photoluminescence through a change in the redox states of functional molecules, metal complexes, polymeric films, etc. Electrofluorochromic materials are considered prospective innovative materials because they can convert electrical input into intuitive visual signals. This field opens novel systems by combining absorption, reflection, and luminescence properties, leading to high contrast, night and day visibility, low-cost displays, and various sensing applications. The former sections provided a short overview of the electrofluorochromic phenomena and observation setups. The electrofluorochromic reactions and devices synchronized with the absorption change based on the electrochemical reaction we reported were also reviewed.

We have already reported a novel multicolor electrochromic (EC) device by introducing a porous counter electrode having high capacitance. In this paper, we investigated the effect of electrolyte species on electric double layer capacitance and coloration properties of the EC device.

The novel Electrochromic(EC) system that utilizing electrodeposition of silver can express various optical properties such as mirror, black, and transparent in a single device. It is expected to be used as an advanced reflective electrochromic display. In this research, the citric acid was added to the electrolyte of the device as an capping agent to simply enhance the reflectance of the EC device.

We have studied Ag deposition-based electrochromic (EC) device that can represent various optical states. In this study, dark-field microscopy (DFM) was applied to in situ observation of localized surface plasmon resonance (LSPR) of Ag electrodeposits. Light scattering spectra obtained DFM provided detailed information on the LSPR.

Silver deposition-based electrochromic (EC) device enabled various optical states by using either the electrodeposition of silver thin films or silver nanoparticles on an indium tin oxide electrode. These optical states, including chromatic colors such as cyan, magenta, yellow, and green, are based on absorption by the localized surface plasmon resonance of silver nanoparticles. However, an ideal counter-reaction material that does not affect the color representation by silver nanoparticles and does not dissolve the deposited silver has not been reported. To achieve both color retention and chromatic color representation, MnO2 was utilized as the counter electrode material. The EC properties of the novel device with the MnO2 counter electrode were investigated in terms of charge density and its ability to change color. The novel EC device achieved both representations of chromatic color and retained its color without power supply

Electrochemical switching of luminescence color, that is, electrofluorochromism, has received increasing attention because of its extensive applications. In this study, we investigate the combination of a luminescent EC molecule and a blue luminescent molecule to achieve electrochemical control of luminescence color by controlling the energy transfer through an electrochromic reaction. We employed a functional leuco dye (Yellow-1), which shows yellow coloration and green emission by electrochemical oxidation, and 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBT), which shows strong blue luminescence upon photoexcitation. Using this combination, the blue photoluminescence of the BBT molecule can be electrochemically modulated by the EC reaction of the Yellow-1 molecule, allowing the control of the luminescence color between blue and green emissions through electrochemical reactions.

The front cover artwork is provided by the group of Norihisa Kobayashi and Kazuki Nakamura at Chiba University. The image shows the drastic luminescence enhancement and induced circular polarization of Eu(D-facam)3 in the presence of tetramethylammonium acetate. Read the full text of the Article at 10.1002/cphc.202100609.

The effect of a series of tetramethylammonium salts with different counter anions on the photophysical properties of a chiral Eu(III) complex (Eu(D-facam)3) was investigated. Anion-dependent luminescence of the Eu(III) complex was observed, and particularly in the presence of acetate ions, an outstanding luminescence enhancement (>300 times) and induced circularly polarized luminescence (glum=−0.63) were obtained. The energy transfer process was then evaluated using key photophysical parameters, and it was found that the sensitisation efficiency of the Eu(III) complex significantly increased in the presence of tetramethylammonium acetate (TMAOAc). The interactions between Eu(D-facam)3 and TMAOAc were confirmed by luminescence analysis, circular dichroism spectroscopy, Fourier transform infrared spectroscopy and mass spectral measurements.

We have reported photo-and electrochemical-functional materials enabling the dual reflective and emissive function by combining electrochromic materials and luminescent materials. In this study, for achieving electrochemical control of luminescence color, we combined various functional molecules such as electrochromic molecules, luminescent molecules. As a result, luminescence colors were successfully controlled through inter-molecular energy transfer between luminescent molecules and electrochromic molecules.

Electrochemiluminescence (ECL), a light-emitting phenomenon induced by electrochemical redox reactions, has the potential for applications in lightweight and flexible light-emitting devices. Previously, an ultrafast ECL response below 100 mu s was successfully obtained under an applied AC voltage by introducing Ru(bpy)(3)(2+), an orange ECL material, onto a DNA-modified electrode. This study introduced blue-luminescent 9,10-diphenylanthracene (DPA) into an ECL device consisting of the DNA/Ru(bpy)(3)(2+) hybrid electrodes. Consequently, blue ECL from DPA was obtained from the DNA/Ru(bpy)(3)(2+) hybrid electrode at a lower applied voltage than that required to induce the redox reactions of DPA itself. This lower-voltage-drivable blue ECL was attributed to triplet-triplet energy transfer from Ru(bpy)(3)(2+) in the DNA/Ru(bpy)(3)(2+) hybrid electrode followed by a triplet-triplet annihilation upconversion reaction of DPA in the electrolyte solution. Moreover, ultrafast-response, electrochemically triggered blue luminescence from DPA was successfully observed.

© 2020 Wiley-VCH GmbH This paper demonstrates a novel display device with four optical states: transparent, mirror, black coloration, and orange light emission. The device is constructed by sandwiching a gel electrolyte containing silver ions and a ruthenium (II) complex between a pair of indium tin oxide electrodes. The electrochemiluminescent orange emission from the ruthenium (II) complex is obtained by applying alternative current (AC) voltage. In contrast, the application of direct current (DC) voltage results in the mirror state due to silver electrodeposition. Moreover, the DC application of a higher voltage results in the device exhibiting the black state owing to the distribution of size and roughness of the silver nanoparticles (NPs) on the indium tin oxide electrode. Both the reflective states reverted to their initial transparent state, owing to the dissolution of silver deposits during the DC application of oxidative voltage of silver NPs.

© 2020, The Author(s). DNA-based materials have attracted much attention due to their unique photo-functional properties and potential applications in various fields such as luminescent and biological systems, nanodevices, etc. In this study, the photophysical properties of a chiral Eu(III) complex, namely (Eu(D-facam)3), within DNA films were extensively investigated. The enhancement of photoluminescence (more than 25-folds increase of luminescence quantum yield) and degree of circularly polarization in luminescence (glum = − 0.6) was observed upon interaction with DNA. Various photophysical analyses suggested that the emission enhancement was mainly due to an increase of the sensitization efficiency (high ηsens) from the ligands to Eu(III) and suppression of the vibrational deactivation upon immobilization onto the DNA molecule. From CD and VCD measurements, it was suggested that the coordination structure of Eu(D-facam)3 was affected by the interaction with DNA, suggesting that the structural change of Eu(D-facam)3 contributed to the improvement of its luminescent properties.

© 2020 The Royal Society of Chemistry. Drastic enhancements in both emission intensity and circular polarization of a Eu(iii) complex were achieved in 1-butanol solution in the presence of alkylammonium ions.

We describe here the preparation of soft crystals using disilanyl macrocycle C4 possessing four p-phenylenes circularly connected by four flexible disilane bonds. Single crystals of C4 exhibited a reversible thermal single-crystal-to-single-crystal (SCSC) phase transition behavior between two crystal phases accompanied by remarkable mechanical motion (thermosalient effect), as revealed by thermal analyses and X-ray diffraction measurements. Detailed structural analyses implied that flexibility of the parallelogram disilanyl architecture and molecular packing mode via weak intermolecular interactions facilitated a concerted structural transformation (parallel crank motion) of macrocycles in the crystal, thus resulting in the SCSC phase transition accompanied by anisotropic shrinking/elongation of the cells to induce the thermosalient effect. This work explores a new area of organosilicon chemistry and presents the potential utility of disilanyl macrocycles as soft crystals.

生体高分子であるDNAは，様々な機能分子をその構造中に取り込むことで 「DNAソフトクリスタル」ともいうべき構造体の形成が期待される．本総説では，DNAとルテニウム (Ru(II)) 錯体との相互作用による組織体の形成とその特徴的な光学特性，および電気化学素子への展開について解説する．透明電極上に成膜したサケの精巣由来のDNA膜に，電気化学発光体として知られるRu(bpy)₃^2＋を電気泳動によって導入し，DNA/Ru(bpy)₃^2＋ハイブリッド膜を作成した．このハイブリッド膜にはDNAとRu(bpy)₃^2＋から構成される特徴的なメゾスコピック構造体の形成が認められた．このDNA/Ru(bpy)₃^2＋ハイブリッド膜を修飾した電極を用いて交流駆動型電気化学発光素子を作成したところ，驚くべきことにサブミリ秒以下 (駆動周波数：10kHz) という，従来系では到底達成できなかった大幅な高速応答化を実現した．さらに，DNAとキラルRu(II)錯体の複合によってエナンチオ選択的発光増強が認められたことから，DNA/Ru(bpy)₃^2＋ハイブリッド材料を組み込んだ電気化学発光素子によって円偏光発光のような特徴的なキラル光学特性の実現可能性が示唆された．

© 2019 This article describes the design of a silver electrodeposition-based electrochromic (EC) device with excellent image retention properties by using the counter electrode reaction of Prussian blue (PB). We demonstrated silver electrodeposition-based EC device enabled various optical states without dyes and pigments. These optical states were explained by localized surface plasmon resonance (LSPR) absorption of silver nanoparticles electrodeposited on an indium tin oxide (ITO) electrode. However, the color retention property of the device was inadequate because of the presence of Cu2+ ions, which function as redox reaction materials at the counter electrode. That is, Cu2+ in the electrolyte oxidizes the silver deposits on the electrode, resulting in a lack of image retention property. To improve both the redox reactivity of the counter electrode and color retention property, here we utilized PB as the counter electrode material. We discuss the device properties of the silver electrodeposition-based EC device with the PB counter electrode in terms of charge density or its ability to change color. The device achieved both longer retention time in the colored state and reversibility. It has an advantage of maintaining the coloring state without electric power for practical applications.

© 2020 by the authors. Organic nonvolatile transistor memory with synthetic polypeptide derivatives as dielectric was fabricated by a solution process. When only poly (γ-benzyl-l-glutamate) (PBLG) was used as dielectric, the device did not show obvious hysteresis in transfer curves. However, PBLG blended with PMMA led to a remarkable increase in memory window up to 20 V. The device performance was observed to remarkably depend on the blend ratio. This study suggests the crystal structure and the molecular alignment significantly affect the electrical performance in transistor-type memory devices, thereby provides an alternative to prepare nonvolatile memory with polymer dielectrics.

<p>Ag deposition-based EC device represents various colors by localized surface plasmon resonance. Four vivid chromatic colors of magenta, cyan, yellow, and green color was represented by precise control of electrodeposition proces of Ag nanoparticles.</p>

© 2019 Elsevier B.V. With the progress and development of electrochromic (EC)technologies in various applications, the demand for multicolor EC devices (ECDs)has been increasing, and it has a huge connection with the expansion of the market. This paper reports on a novel multicolor ECD with a simple hybrid capacitor architecture (glass/ITO/multi-EC gel/carbon/glass), containing both anodic and cathodic EC materials. By employing the carbon capacitor electrode having porous morphology and large surface area as a counter electrode, even large charge amount consumed by multiple redox pairs’ cathodic materials was adequately compensated. The successful fabrication of the device, consequently, it provides four well-defined colors (white, green, yellow, and red)in one single device.

We have already reported a novel multicolor electrochromism in a single device by introducing a porous counter electrode having high capacitance. In this paper, we investigated effect of capacitance properties of counter electrode into coloration properties of 10-methylphenothiazine molecule.

Prussian blue modified electrode was introduced into Ag deposition-based electrochromic (EC) device as the counter-reaction material for charge compensation of Ag redox. We discuss the bi-stability of the optical states and desirable features of Prussian blue film for metal deposition based EC device.

This journal is © The Royal Society of Chemistry. Electrochemically triggered upconverted luminescence through triplet-triplet energy transfer (TTET) and subsequent triplet-triplet annihilation upconversion (TTA-UC) is observed for the first time in the electrochemiluminescence properties of a Ru(bpy)32+/DPA-containing electrochemical device.

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A europium(III) [Eu(III)] complex and a viologen derivative were covalently immobilized on a porous titanium(IV) dioxide (TiO2) electrode by the interaction of carboxyl and phosphate groups with the surface, demonstrating electrochemically induced photoluminescence and coloration switching. The modulation of emission and coloration using the functional Eu(III)-viologen modified TiO2 electrode was achieved by an electrochemical reaction between TiO2 and the viologen derivative. Luminescence control was induced via electron and energy transfer from the Eu(III) complex to TiO2 and the linked viologen derivative. The dual functional electrode showed a high on-off emission contrast (81:1), short response time (off: 2.5 s at −0.8 V, on: 5 s at 0 V), and high stability (over 150 cycles) for both emission and coloration control.

© 2018 Norihisa Kobayashi et al., published by De Gruyter, Berlin/Boston. In this review, we describe the investigation of a ruthenium [Ru(II)] complex-based, AC voltage-driven, electrochemiluminescent (ECL) device first. The ECL turn-on response time and intensity were dramatically improved by introducing the AC method. The turn-on response time was speeded up by increasing the applied frequency: 4 ms response time was achieved at 200 Hz, which was much faster than when using the DC method (1.5 s). We also introduced rutile-type titanium dioxide nanoparticles (TiO2 NPs) in a Ru(II) complex-based AC-ECL device. The ECL intensity and the lifetimes of the ECL device with TiO2 NPs were greatly improved compared to those of the device without nanoparticles. Then we tried to improve photoelectrochemical properties of the Ru(II) complex by combining it with DNA molecules. We fabricated a novel DNA/Ru(bpy)32+ hybrid film that could immobilize the ECL-active Ru(bpy)32+ onto the electrode surface through electrophoretic migration. The hybrid film contained unique micrometer-scale aggregates of Ru(bpy)32+ in the DNA matrix. Surprisingly, by using the DNA/Ru(bpy)32+ hybrid film for the ECL device, luminescence could be obtained at frequencies as high as 10kHz, which corresponds to a response time shorter than 100μs.

© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). Deoxyribonucleic acid (DNA)-based functional materials containing luminescent molecules have attracted widespread attention as opto-electronic materials. In this study, luminescence properties of DNA/chiral Ru(phen)32+ complexes were investigated. The DNA/chiral Ru(phen)32+ complexes showed an enantioselective enhancement of luminescence. The DNA/δ-Ru(phen)32+ complex showed a higher luminescence intensity and longer luminescence lifetime than the DNA/δ-Ru(phen)32+ complex. Binding modes between DNA and δ-/δ-Ru(phen)32+ are discussed in terms of optical properties. The study shows that δ-Ru(phen)32+ preferentially intercalates to form a more stable DNA complex than δ-Ru(phen)32+, leading to enantioselective luminescence enhancement.

© Copyright Materials Research Society 2018. Ag deposition-based multicolor electrochromic (EC) device we reported can switch various optical states among transparent, black, silver, cyan, magenta, and yellow by only using electrochemical deposition of Ag. However, the EC device had poor color retention property under open-circuit state because of dissolution of deposited Ag metal by Cu2+ ions, which is essential because it acts as redox material at counter electrode. Here, we introduced an anion exchange membrane to separate Cu2+ from the Ag deposit. The improved device achieved longer retention time of colored state. It is effective to maintain the coloring state without electric power for practical application.

© 2017 Elsevier B.V. Electrochromic-based optical modulation devices have attracted much interest because of potential application for electric papers and smart windows. We have reported Ag deposition-based optical modulation device which showed reversible changes of optical states between clear transparent and silver-mirror. In the device, formation of silver halide complexes greatly affected the optical states of silver electrodeposit. In this research, the effects of silver halide complexes were investigated by changing halide anion species in terms of the optical properties of the EC devices. The stability of the silver halide complex induced change in reduction voltage to form silver nanoparticles. Diffusion coefficients and electrode reaction rates also have effects on morphology of deposited Ag nanoparticles and resulting optical properties.

© 2018 The Royal Society of Chemistry. DNA-based functional materials are of great interest in electrical and optical device applications. In this paper, novel DNA-based photo-functional materials were fabricated by associating a DNA-lipid complex with a luminescent Eu(iii) complex. Interactions between DNA-lipid and Eu(iii) complexes were investigated by photophysical measurements in both solution and film states. The emission properties of the Eu(iii) complex were improved by association with the DNA-lipid complex in the film state. The emission intensity, quantum yield, and thermal stability of the Eu(iii) complex hosted by the DNA-lipid matrix were superior to those of the complex in a conventional poly(methyl methacrylate) matrix. Furthermore, the Eu(iii) complex in the DNA-lipid film showed circularly polarized luminescence through excitation of the ligand moiety. The chiral environment of the DNA matrix provides optical chirality to the interacting Eu(iii) complex.

© the Owner Societies 2018. Despite the application of electrochromic (EC) technologies in various optical modulating devices, the challenge to achieve multicolour EC behavior in a single device still remains. However, because almost all EC materials exhibit a single colour change, only a few organic materials are able to undergo multiple colour switching within a single device. The development of multicolour EC applications is therefore highly limited. In this research, we fabricated an EC device (ECD) with the simple hybrid capacitor architecture, i.e. with a flat ITO electrode as the working side and an ITO particle-modified electrode as the counter side. We also employed an electrolyte containing both anodic and cathodic EC materials consisting of small organic molecules. In this novel ECD, each EC material successfully undergoes individual colour switching from light yellow to light green and magenta. The mechanism of a multicolour system represents a significant breakthrough towards a full-colour ECD, thereby expanding the potential of EC technology.

© 2018SPST. An electroswitching device that enables modulation of both photoluminescence and coloration was obtained. The device consisted of luminescent lanthanide(III) complex Eu(hfa)3(TPPO)2 (photoluminescence material) and an diheptyl viologen HV2+ (electrochromic material). Coloration and emission control were achieved by only electrochemical reactions of HV2+. The coloration of the device was controlled by HV2+ electrochromism. Photoluminescence control was also achieved by the HV2+ electrochromism via intermolecular energy transfer from the excited states of Eu(III) ions to colored HV+∙. However, there were some problems that the response time of switching between emission and coloration was quite slow (approximately 15 minutes), and the representation stability of switching between emission and coloration was low. These problems would be caused by absence of counter electrode reaction material against HV2+ redox. In order to improve the response time of the cell and decrease the driving voltage for dual-mode representation, we introduced prussian blue (PB) modified electrode as an electrochromical counter redox material.