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Here, we determined the quantum yields of photoluminescence (ΦLumi) of five commercially available TiO2photocatalysts (two rutile and three anatase; particle diameter: 7–400 nm) by comparison with ΦLumivalues obtained for three luminescent inorganic standard materials. The shapes of the luminescence spectra of the photocatalysts were similar to those reported previously. Very small ΦLumivalues were obtained for all five photocatalysts [e.g., 5.2 × 10–6for nano-sized anatase TiO2(particle diameter: 7 nm)], indicating that photoluminescence is a minor channel in the photophysical processes of these materials. In addition, ΦLumiwas much larger for the photocatalysts with a larger particle size than for those with a smaller particle size for both anatase and rutile TiO2, which implies that luminescence arises predominantly from the bulk of the particles and that the surface plays a role as a quenching center in both polymorphs. The origin of the luminescence is discussed in relation to the previous studies.

This study reports on the multiresponsive behavior of Co(II) bis(tolylterpyridine) nitrate crystals. Each crystal contains a single Co(II) complex and can accommodate up to 4 H2O molecules per asymmetric unit. In its fully hydrated form, the crystal contains planar hexameric hydrogen-bonded H2O clusters. The adsorption and desorption of H2O occur reversibly with changes in humidity, despite the absence of extended H2O channels. Furthermore, the crystals exhibit a crystal-to-crystal thermal phase transition. The structural studies reveal the dynamic nature of these crystals, which contribute to their multiresponsive behavior.Graphical Abstract

The performance improvement of solid-state triplet–triplet annihilation-based photon upconversion (TTA-UC) systems is required for the application to various solar devices. The performance can be improved by making use of the local strong electric field generated through the excitation of localized surface plasmon (LSP) resonance of metal nanostructures. However, since the improvement is effective only within the limited nanospace around nanoparticles (i.e., the near-field effect), a methodology for improving the performance over a wider spatial region is desirable. In this study, a significant improvement in the threshold light excitation intensity (Ith) (77% decrease) as the figure of merit and the upconverted emission intensity (6.3 times enhancement) in a solid-state TTA-UC film with a thickness of 3 μm was achieved by stacking the film with periodic Ag half-shell arrays. The highest-enhanced upconverted emission was obtained by tuning the diffuse reflectance peak, which results from the excitation of LSP resonance of the Ag half-shell arrays, to overlap well with the photoexcitation peak of the sensitizer in the TTA-UC film. The intensity of the enhanced upconverted emission was independent of the distance between the lower edge of the TTA-UC film and the surface of half-shell arrays in the nanometer order. These results suggest that the performance improvement was attributed to the photoexcitation enhancement of the sensitizer by elongating the excitation light path length inside the TTA-UC film, which was achieved through a strong backward scattering of the incident light based on the LSP resonance excitation (i.e., the far-field effect). In addition, the upconverted emission was improved using half-shell arrays comprising low-cost Al, although the enhancement factor was 3.5, which was lower than that of Ag half-shell arrays. The lower enhancement may be attributed to a decrease in the backward scattering of the excitation light owing to the intrinsic strong interband transition of Al at long visible wavelengths.

•A novel anthradithiophene based hole-transport material is designed.•BTPA-7 exhibits higher hole mobility and tgthan spiro-OMeTAD.•BTPA-7 based PSC shows comparable device performance to that of spiro-OMeTAD.•More hydrophobic BTPA-7 than spiro-OMeTAD is beneficial for its PSC stability.

Synthesis of anisotropic Ag nanoprisms (AgPRs) contributes to the development of high performance plasmonic devices. The localized surface plasmon resonance wavelength of AgPRs was successfully tuned within 500–600 nm by sequential irradiation of 470-nm and 525-nm light to the Ag nanospheres for predetermined periods of time. We have clarified the mechanism in which the AgPRs are synthesized by the first irradiation, which act as the seeds for the growth in the second irradiation with remaining Ag nanospheres being consumed.The localized surface plasmon resonance wavelength of Ag nanoprisms was successfully tuned within 500–600 nm by sequential irradiation of 470-nm and 525-nm light to Ag nanospheres for predetermined time. We have clarified the mechanism in which the nanoprisms are synthesized by the first irradiation, which act as seeds for the growth in the second irradiation with Ag nanospheres being consumed.

We obtained two types of crystals of a complex under different crystallization conditions, each exhibiting distinct molecular arrangements and magnetic interactions: one type consists of isolated complexes, while the other forms one-dimensional chains without extra bridging ligands. This approach provides a new avenue for tuning the magnetic properties of metal-complex-based materials.The same trinuclear copper complex crystalizes in two different arrangements: one with isolated complexes and the other forming one-dimensional chains. This approach provides a new avenue for tuning the magnetic properties of metal-complex-based materials.

Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved viaself-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices.

We have succeeded in significantly enhancing fluorescence from intrinsically phosphorescent palladium octaethylporphyrin (Pd-porphyrin) that has an intersystem crossing efficiency of ∼1 by using silver nanoprisms (AgPRs). This was achieved by controlling the wavelength of the localized surface plasmon (LSP) resonance of AgPRs and the distance between the Pd-porphyrin molecules and the AgPR surfaces. In addition to enhancing phosphorescence by spectrally overlapping the phosphorescence band with the LSP resonance band, tuning the LSP wavelength to approximately 520 nm led to the appearance of a new emission band around the wavelength corresponding to the fluorescent radiation. The appearance of fluorescence suggests that the nonradiative energy transfer from the singlet excited state of Pd-porphyrin to the LSP of AgPRs overcame the ultrafast intramolecular intersystem crossing to the triplet excited state, manifesting the spectral properties of the singlet excited state of Pd-porphyrin. The fluorescence nature of this radiation was strongly supported by lifetime measurements of the hybrids of Pd-porphyrin and AgPRs. Furthermore, the dependence of the emissive intensities on the distance between the Pd-porphyrin molecules and the AgPR surfaces showed interesting opposite trends. The fluorescence intensity was increased as the distance between the molecules and the AgPRs was decreased from 10.5 to 1 nm, while the phosphorescence intensity was decreased, which indicates that the LSP-induced fluorescence radiation process from Pd-porphyrin near the AgPRs outweighed the quenching by the AgPRs, even though the phosphorescence significantly suffered quenching.

Concerning a series of naphthalimide-based fluorescence dyes in which the p-system is extended with oligothiophene units, it has been revealed that the absorption and fluorescence maxima can be tuned over ca. 100 nm and ca. 180 nm range by extending p-conjugation, respectively. The effects of the solvent on the fluorescence quantum yield depend on the conjugation length. For the same series but with an electron-donating moiety (push-pull type dyes), the absorption and fluorescence maxima are less dependent on the conjugation length. The fluorescence quantum yields of the push-pull type dyes are large in toluene (>0.3) but extremely low in DMSO. These results will be a guide for the design of naphthalimide-based sensors and probes.A series of naphthalimide-based fluorescent dyes with the p-system extended by thiophene units with and without an electron-donating moiety have been prepared. How the extension of p-system and introduction of an electron-donating moiety affect the photophysical properties for these dyes has been revealed.

As a basis for the design of electroactive materials, mono‐ and bis‐tetrathiafulvalene (TTF) derivatives with one and two amide units were prepared to investigate how hydrogen bonding induces electronic communication. The bis‐TTF compound exhibited a mixed‐valence state as a result of electronic interactions among the TTF units. Comparison with non‐hydrogen‐bonding N‐methylated analogues indicated that the electronic interaction observed occurs between intermolecular TTF units owing to the formation of supramolecular assemblies induced by hydrogen bonds. They talk to one another: Four kinds of tetrathiafulvalene (TTF) derivatives were synthesized and classified as hydrogen‐/nonhydrogen‐bonding derivatives. Hydrogen‐bonding TTF derivatives with two amide units showed intervalence charge transfer absorption bands derived from intermolecular hydrogen bonds in organic solvents.

We have fabricated hybrids of two-dimensional silica colloidal crystals and gold nanospheres for the development of platforms showing effective SERS phenomenon with a high spatial reproducibility. The SERS signal of 4-mercaptobenzoic acid immobilized on the hybrids was enhanced up to 10.4 times by optimizing the silica diameter, as compared with that on the gold nanospheres immobilized on a planar glass plate. We propose that the effective enhancement is induced by hot spots generated at the junction regions between the silica nanospheres.We have fabricated hybrids of two-dimensional silica colloidal crystals and gold nanospheres for the development of effective SERS platforms with a high spatial reproducibility. The SERS signal on the hybrids was enhanced up to 10.4 times by optimizing the silica diameter, as compared with that on the gold nanospheres-immobilized planar glass plate.

Prostaglandin E2 (PGE2) exerts various biological effects by binding to E-prostanoid receptors (EP1-4). Although recent studies have shown that PGE2 induces cell differentiation in some neuronal cells such as mouse DRG neurons and sensory neuron-like ND7/23 cells, it is unclear whether PGE2 plays a role in differentiation of motor neurons. In the present study, we investigated the mechanism of PGE2-induced differentiation of motor neurons using NSC-34, a mouse motor neuron-like cell line. Exposure of undifferentiated NSC-34 cells to PGE2 and butaprost, an EP2-selective agonist, resulted in a reduction of MTT reduction activity without increase the number of propidium iodide-positive cells and in an increase in the number of neurite-bearing cells. Sulprostone, an EP1/3 agonist, also significantly lowered MTT reduction activity by 20%; however, no increase in the number of neurite-bearing cells was observed within the concentration range tested. PGE2-induced neurite outgrowth was attenuated significantly in the presence of PF-0441848, an EP2-selective antagonist. Treatment of these cells with dibutyryl-cAMP increased the number of neurite-bearing cells with no effect on cell proliferation. These results suggest that PGE2 promotes neurite outgrowth and suppresses cell proliferation by activating the EP2 subtype, and that the cAMP-signaling pathway is involved in PGE2-induced differentiation of NSC-34 cells.

A donor–acceptor–donor molecule with a 2,1,3-benzooxadiazole moiety, named BTPA-3, was successfully synthesized and employed as a hole-transporting material (HTM) for Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3- and CH3NH3PbBr3-based perovskite solar cells (PSCs). The best CH3NH3PbBr3-based PSC with BTPA-3 exhibited a superior efficiency (5.91%) compared to the cell with spiro-OMeTAD (5.61%), even an 80 mV higher open-circuit voltage (Voc) being recorded in the reverse scan (average Voc: 1.41 V for BTPA-3 and 1.33 V for spiro-OMeTAD). The higher Vocis attributed to larger recombination resistance and the resulting longer photovoltage lifetimes in the cells with BTPA-3. In the meantime, for the Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3-based PSC, BTPA-3 exhibited a much lower conversion efficiency (9.81%) compared with the cell with spiro-OMeTAD (13.2%) due to a small driving force for the hole injection. The morphologies and conductivities of the hole-transport layers were also investigated, and the results are discussed in relation to the performances of the PSCs. Finally, PSCs with BTPA-3 as an HTM based on both perovskite lead halide materials exhibited good long-term stabilities.

We demonstrated the usefulness of Cu light-harvesting plasmonic nanoantennae for the development of inexpensive and efficient artificial organic photoelectric conversion systems. The systems consisted of the stacked structures of layers of porphyrin as a dye molecule, oxidation-suppressing layers, and plasmonic Cu arrayed electrodes. To accurately evaluate the effect of Cu nanoantenna on the porphyrin photocurrent, the production of Cu2O by the spontaneous oxidation of the electrode surfaces, which can act as a photoexcited species under visible light irradiation, was effectively suppressed by inserting the ultrathin linking layers consisting of 16-mercaptohexadecanoic acid, titanium oxide, and poly(vinyl alcohol) between the electrode surface and porphyrin molecules. The reflection spectra in an aqueous environment of the arrayed electrodes, which were prepared by thermally depositing Cu on two-dimensional colloidal crystals of silica with diameters of 160, 260, and 330 nm, showed clear reflection dips at 596, 703, and 762 nm, respectively, which are attributed to the excitation of localized surface plasmon resonance (LSPR). While the first dip lies within the wavelengths where the imaginary part of the Cu dielectric function is moderately large, the latter two dips lie within a region of a quite small imaginary part. Consequently, the LSPR excited at the red region provided a particularly large enhancement of porphyrin photocurrent at the Q-band (ca. 59-fold), compared to that on a Cu planar electrode. These results strongly suggest that the plasmonic Cu nanoantennae contribute to the substantial improvement of photoelectric conversion efficiency at the wavelengths, where the imaginary part of the dielectric function is small.

While the distance dependence of metal-enhanced fluorescence has been extensively studied for composite systems comprising fluorophores and metal nanoparticles, the corresponding distance dependence of triplet–triplet annihilation upconversion (TTA-UC) systems remains unexplored. Herein, we investigated the influence of the spatial distance between Ag nanoprisms (AgPRs) and TTA-UC thin films consisting of a palladium octaethylporphyrin (PdOEP) sensitizer and a 9,10-diphenylanthracene (DPA) emitter, aiming at enhancing the upconverted (UC) emission as efficiently as possible. Results indicated that the optimal distance for the examined system was significantly longer (12.6 nm) than those of typical metal-enhanced fluorescence systems (about 2 nm). We demonstrated that the UC emission enhancement factor can be expressed as a product including factors of the PdOEP photoexcitation rate, triplet–triplet energy transfer (TTET) efficiency from PdOEP to DPA, triplet excited DPA lifetime, and fluorescence efficiency of singlet excited DPA. We discovered that the AgPRs play a beneficial role in enhancing the PdOEP photoexcitation, whereas they exert detrimental effects on the other three factors. Among these three factors, quenching contributions by the decrease of the triplet excited DPA lifetime and DPA fluorescence efficiency were significant, making these the primary and secondary factors, respectively, for the UC emission quenching, particularly at short distances. These results demonstrate that the characteristic distance dependence of the UC emission enhancement is determined by the competing effects of beneficial PdOEP photoexcitation enhancement and the detrimental localized surface plasmon (and/or AgPR)-induced nonradiative decay of the triplet- and singlet excited DPA molecules. The findings offer valuable guidelines for the design of high-performance plasmonic TTA-UC systems.

We demonstrate that Pd nanospheres exhibit much higher susceptibility of the localized surface plasmon resonance (LSPR) peak to medium refractive index changes than commonly used plasmonic sensing materials such as Au and Ag. The susceptibility of spherical Au nanoparticle–core/Pd-shell nanospheres (Au/PdNSs, ca. 73 nm in diameter) was found to be 4.9 and 2.5 times higher, respectively, than those of Au (AuNSs) and Ag nanospheres (AgNSs) having similar diameters. The experimental finding was theoretically substantiated using the Mie exact solution. We also showed from a quasi-static (QS) approximation framework that the high susceptibility of Pd LSPR originates from the smaller dispersion of the real part of its dielectric function than those of Au and Ag LSPR around the resonant wavelength. We conclude that the Pd nanoparticle is a promising candidate of “the third plasmonic sensing material” following Au and Ag to be used in ultrahigh-sensitive LSPR sensors.

A methodology for fabricating two-dimensional assemblies consisting of octadecylamine-stabilized gold, silver, and mixed gold and silver nanoparticles at an air/toluene droplet interface is reported. After evaporation of the toluene solvent, the structure and optical properties of the resulting high-density nanoparticle assemblies were evaluated by transmission absorption spectroscopy and scanning electron microscopy (SEM). In addition, an investigation of the surface-enhanced Raman scattering (SERS) activity of para-mercaptoaniline molecules adsorbed on these assemblies revealed that by increasing the mixing ratio of silver nanoparticles to gold nanoparticles, SERS signals were significantly enhanced due to an adjustment in the excitation wavelength of surface plasmon resonance and an enhancement of the local electromagnetic field.

We prepared novel cerium meso-tetrathienylporphyrin double-decker complexes with 2-thienyl and 3-thienyl substituents. The X-ray structures show that the porphyrin rings are distorted in a half-pipe fashion, which seems to be a common type of distortion for double-decker complexes of tetraarylporphyrins. The side-arm thienyl groups rotate more than two orders of magnitude faster than the phenyl groups of the corresponding double-decker complex of meso-tetraphenylporphyrin in solution at room temperature because of the lower rotational barriers.The X-ray structures of cerium meso-tetrathienylporphyrin double-decker complexes with 2-thienyl and 3-thienyl sustituents show that the porphyrin rings are distorted in a half-pipe fashion. The side-arm thienyl groups rotates more than two orders of magnitude faster than the phenyl groups of the corresponding double-decker complex of meso-tetraphenylporphyrin in solution at room temperature.

The effect of localized surface plasmon resonance (SPR) appearing at the surfaces of gold nanoparticles (AuPs) was successfully applied for the enhancement of photocurrents from porphyrin (Po) immobilized on AuPs. The electrode consisting of AuPs with different sizes (∼15 or ∼35 nm) was prepared using the AuP film formed at the liquid/liquid interface, and then Powas self‐assembled on the gold surface. The SPR effect for the AuP film was verified from the attenuated total reflection SPR and absorption measurements. Photocurrents from the modified electrodes were compared with the corresponding planar electrode. Appreciable enhancement of photocurrents was observed.

We investigated the enhancement properties of the photocurrent generation from self-assembled monolayers of porphyrin fabricated on periodic structures of gold half-shells. Tuning the surface plasmon frequency of the nanostructures led to correlated wavelength dependences of the external quantum efficiencies of the photocurrents, as well as fluorescence intensities resulting from effective electronic excitation of porphyrin molecules.

We have found that Cu(NO3)2and 1,3-dione dioxime afford a variety of multicopper complexes under ambient conditions. Specifically, Cu(NO3)2and cyclohexane-1,3-dione dioxime gave a trinuclear complex in which the central α-carbons of the three dioxime ligands are oxidized into carbonyl groups, two of which were further reacted with solvent MeOH to give a hemiacetal structure. On the other hand, Cu(NO3)2and cyclopentane-1,3-dione dioxime gave a dinuclear complex in which Cu(II) was reduced to Cu(I) and two of the three ligands couple to give the fulvalene structure. Together with the previously reported reaction of Cu(NO3)2and pentane-2,4-dione dioxime into a pentanuclear complex in which the four ligands were changed into trioximes, surprisingly rich chemistry has been discovered for combinations of Cu(NO3)2and 1,3-dione dioximes.

The effects of substituents at the bay positions for push–pull-type perylenedicarboxylic anhydride dyes on the performance of dye-sensitized solar cells were investigated. The substituents fine-tune the optical and redox properties of the dyes. It turned out that the simplest dye without any substituent results in highest-efficiency cells because of its broadened IPCE spectrum due to intermolecular interactions, which implies that aggregation may not always be detrimental to the performance of the solar cell.

We fabricated two-dimensional assemblies of gold and silver nanoparticles on polycation coated substrates by a liquid-liquid interfacial precipitation method. The assembling of the metal nanoparticles on the substrate was evaluated by absorption spectroscopy and scanning electron microscopy. Raman scattering signals of Rhodamine 6G were detected on the metal nanoparticle-modified substrates. In particular, the intensities of the Raman scattering signals of the mixed gold and silver nanoparticle-modified substrates were larger than the intensities expected from a simple proportional sum of the Raman scattering signals of the individual assembly films composed of only gold or silver nanoparticles.

Resistive change random access memory (ReRAM), which is expected to be the next-generation nonvolatile memory, often has wide switching voltage distributions due to many kinds of conductive filaments. In this study, we have tried to suppress the distribution through the structural restriction of the filament-forming area using NiO nanowires. The capacitor with Ni metal nanowires whose surface is oxidized showed good switching behaviors with narrow distributions. The knowledge gained from our study will be very helpful in producing practical ReRAM devices.

Electrocommunication: Bis‐tetrathiafulvalene (TTF) derivatives with amide units have been synthesized. The electronic communication between the TTF units was observed to occur in an intermolecular fashion owing to the formation of hydrogen‐bonded supramolecular assemblies. This work demonstrates that incorporation of hydrogen bonding sites is an effective methodology to induce intermolecular electronic interactions in solution. More information can be found in the Communication by Joe Otsuki et al. on page 897 in Issue 5, 2018(DOI: 10.1002/ajoc.201800100).

Core/shell type nanoparticles, in which the shell consists of a thin layer of metal and the core consists of monodispersed dielectric nanoparticles, are of great interest owing to their characteristic plasmonic properties. In this study, we have fabricated highly regular two-dimensional arrays of silica-core/gold (or silver)-shell nanoparticles protected with polyvinylpyrrolidone (PVP) by drop-casting their colloidal ethanol solutions onto tilted glass plates. The structure and plasmonic properties of the arrays were evaluated by visible/near-infrared transmission absorption spectroscopy and scanning electron microscopy (SEM). The characteristic broad plasmon band in the near-infrared wavelength region, derived from a hybridized mode of dipolar plasmon modes of the individual core/shell nanoparticle, appeared by changing the concentration of PVP added.

Surface plasmons induced at metal surfaces generate remarkable enhancements of localized electric fields as a result of interactions with incident light fields. This is called localized surface plasmon resonance (LSPR). In this study, we report a simple technique for transferring LSPR-active gold and Au\text{core--Ag\text{shellnanoparticles from an aqueous to a toluene phase using octadecylamine molecules for organic-solution processing. The changes in optical properties and size dependence of transfer behavior of the nanoparticles were evaluated by absorption spectroscopy and transmission electron microscopy (TEM). The upper limit of the size of particles that can be transferred into an organic phase is about 25 nm. We also fabricated an LSPR-active colloidal monolayer film on a solid support by solvent evaporation of a colloidal organic solution.

Nanowires embedded in nanopores are potentially tough against surface scraping and agglomeration. In this study, we have fabricated Au and Ni nanowires embedded into anodic porous alumina (APA) and investigated their reflectance to study the effects of surface plasmon absorption properties and conversion from solar energy to thermal energy. Au nanowires embedded into APA show typical gold surface plasmon absorption at approximately 530 nm. On the other hand, Ni nanowires show quite a low reflectance under 600 nm. In the temperature elevation test, both Au and Ni nanowire samples present the same capability to warm up water. It means that Ni nanowires embedded into APA have almost the same photothermal activity as Au nanowires.

Localized surface plasmon resonance leads to an increase in the degree of photon absorption and concomitant emission in copper phthalocyanine–gold nanoparticle systems.

In this study, we have developed localized surface plasmon resonance (LSPR) refractive index sensor systems consisting of triangular silver nanoplates (nanoprisms) immobilized on glass plates by electrostatic interactions. The nanoprisms are synthesized by exploiting light-induced morphological changes in silver nanoparticles in aqueous solution. We have demonstrated that silver nanoprisms protected with alkylthiol molecules and supported by glass plates can function as spectrally stable LSPR refractive index sensors even in ethanol solvents. The sensitivity of the nanoprisms was found to increase with decreasing carbon chain length of alkylthiol. Furthermore, we have demonstrated that nanoprisms with higher aspect ratios had higher sensitivities than those with lower aspect ratios.