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A cyanido-bridged Co–W assembly showing a charge transfer–induced phase transition realized room temperature bistability and red-blue drastic color change.

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.

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 μs was successfully obtained under an applied AC voltage by introducing Ru(bpy)32+, 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)32+ hybrid electrodes. Consequently, blue ECL from DPA was obtained from the DNA/Ru(bpy)32+ 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)32+ in the DNA/Ru(bpy)32+ 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.

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.

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.

Enamel-like fluorapatite (FA) films were produced on a conventional polyvinyl alcohol (PVA) sheet in an aqueous solution system based on simulated body fluid containing fluoride ions. We obtained FA films thicker than 100 μm by multistep crystal growth on the polymer sheet. High-density nucleation of the FA crystals was achieved on the polymer surface having OH groups at a relatively high degree of supersaturation. Crystal growth of the FA nanorods along the c direction was then promoted through geometric selection at a relatively low degree of supersaturation. Multistep epitaxial growth produced enamel-like architectures consisting of c-axis-oriented nanorods with a controlled diameter below 300 nm.

Multifunctional materials such as those with thermo-switchable absorption or emission are widely applied to thermal recording media. We combined red-green-blue (RGB) thermochromic materials and luminescent materials in order to construct novel dual-mode display media that can control both coloration and emission. The composite films showed thermo-responsive control of RGB coloration with high reversibility through structural changes of nanoscale aggregates of the leuco dye and its developer. Moreover, RGB photoluminescence was also controlled by specific thermal treatment via intermolecular energy transfer from luminescent materials in the excited state to the colored leuco dyes.

Electrochemical modulation of red luminescence from a europium(III) complex has been demonstrated. In order to elucidate the mechanism of luminescence modulation, its cyclic voltammogram, absorption spectra, emission spectra, emission lifetime, and emission quantum yield were measured. From these measurements, the modulation of emission was found to be achieved through an electrochemical reaction of TiO2, which is facilitated by electron transfer between the europium(III) complex and TiO2. Subsequent immobilization of the europium(III) complex on a TiO2 electrode resulted in an on–off emission contrast of 74 : 1, with the response time and repetition stability of the emission switching being considerably improved.

A thin-film transistor (TFT) non-volatile memory (NVM) device was fabricated using α-helix poly(γ-methyl-L-glutamate) (PMLG) as a ferroelectric layer. In order to study the mechanism of memory driving, the temperature dependence of transfer characteristics and memory performance was investigated. It was revealed that the cooperative movement of the large dipole moment along the rod-like main chain and that of the small dipole moment in the side chain played an important role in the memory function.

A multifunctional composite film that exhibited thermoresponsive absorption and emission was fabricated using a thermochromic fluoran dye, its developer, and a luminescent europium(III) complex. The emissions from and coloration of this composite film could be reversibly changed and maintained via the thermochromic reaction taking place within the fluoran dye–developer system. The coloration and decoloration of the composite film were caused by thermoresponsive control of the nanoscale aggregation of structures of the fluoran dye and its developer, whose molecular structure consisted of a long alkyl chain. The control of the phenomenon of photoluminescence could also be achieved via thermochromism, which was induced by intermolecular energy transfer from the Eu(III) ions in the excited state to the fluoran dye.

We investigated the properties of 4,4'-biphenyl dicarboxylic acid diethyl ester (PCE). The PCE underwent a 2-step reduction at -1.5 V and -2.2 V. The color of the PCE changed from colorless to yellow in the first step and consequently to red in the second reduction step. A PCE based EC cell using an NiO-modified electrode was also fabricated. The NiO electrode worked as a counter reaction material for PCE reduction. The PCE-NiO cell achieved multi-coloration ranging from colorless to yellow and red, and also achieved high coloration efficiency and long term switching stability.

An organic thin-film transistor (OTFT) memory was fabricated using deoxyribonucleic acid (DNA) as a gate dielectric layer. Since natural DNA contains intrinsic ions and water molecules, the OTFT exhibited low resistivity and a low on/off ratio because of the mobile ions. In order to remove these mobile ions from DNA, it was complexed with a bulky surfactant through an electrostatic interaction. The OTFT fabricated using a DNA–surfactant complex exhibited a relatively high on/off ratio because of the decrease in the off-current. Residual ions that remained in the complex caused a decrease in the cell performance with respect to parameters such as the on/off ratio and long-term memory stability. When poly(methyl methacrylate) (PMMA) was layered on the DNA–surfactant layer, the OTFT exhibited better on-current and long-term memory stability than a typical OTFT. The pentacene layer deposited on the PMMA surface as a semiconductor had a relatively large grain size and relatively high crystallinity. This contributed to an increase in the hole mobility in the pentacene layer and the prevention of the abovementioned adverse effects of the residual ions. Consequently, the performance of the OTFT memory having the DNA complex was considerably improved.