Durable Ultraflexible Organic Photovoltaics with Novel Metal‐Oxide‐Free Cathode

Flexible and stretchable organic photovoltaics (OPVs) are promising as a power source for wearable devices with multifunctions ranging from sensing to locomotion. Achieving mechanical robustness and high power conversion efficiency for ultraflexible OPVs is essential for their successful application. However, it is challenging to simultaneously achieve these features by the difficulty to maintain stable performance under a microscale bending radius. Ultraflexible OPVs are proposed by employing a novel metal‐oxide‐free cathode that consists of a printed ultrathin metallic transparent electrode and an organic electron transport layer to achieve high electron‐collecting capabilities and mechanical robustness. In fact, the proposed ultraflexible OPV achieves a power conversion efficiency of 9.7% and durability with 74% efficiency retention after 500 cycles of deformation at 37% compression through buckling. The proposed approach can be applied to active layers with different morphologies, thus suggesting its universality and potential for high‐performance ultraflexible OPV devices.     

Exfoliation of non-swelling muscovite on dodecylammonium chloride intercalation between layers using wet-jet milling

The exfoliation of layered muscovite with non-swelling property has been performed by combining various processes, such as heating, intercalation, and wet-jet milling. The c axis of muscovite was expanded from 2004.0 to 2022.8 pm at 800 °C without the destruction of crystallinity of muscovite. The heating at 800 °C led to the weak attraction force between potassium ions and silicate layers by hydroxylation of muscovite. The muscovite heated at 800 °C progressed the intercalation of dodecylammonium chloride (DDAC) into the layers effectively. Furthermore, the DDAC molecules were inserted to the interlayer of muscovite effectively by suppressing the formation of micelle of DDAC. The sedimentation test of wet-jet milled muscovite slurry showed that the relative packing density of muscovite was decreasing with increasing the amount of the intercalated DDAC. As results, the aspect ratio of muscovite prepared with combining the heating, the intercalation and the wet-jet milling was increased by 253% as compared to the raw muscovite. The aspect ratio was calculated from laser particle size distribution and thickness size distribution which was estimated from field emission-scanning electron microscopic images. The expansion of the interlayer led to the effective exfoliation of muscovite with high aspect ratio.     

The study of the effect of external additives on the synthesis of fumed TiO2 with a high content of rutile structure by the novel natural dropping thermal treatment

The effect of external additives on the synthesis of fumed TiO₂ with a high rutile structure content was studied. The focus of this investigation was on the external additive species, agglomerates of the fumed TiO₂ before and after the thermal treatment. The transformation ratio from the anatase to rutile structure of the thermally-treated fumed TiO₂ was investigated as a function of the fumed TiO₂ agglomerate before the thermal treatment. Small agglomerated powders resulted in a decrease of transformation temperature. Two novel results were obtained in this investigation. One was a new fumed TiO₂ with a 100% rutile structure having an excellent dispersibility being successfully synthesized by the thermal treatment of AEROXIDE® TiO₂ P 25 with a small portion of AEROSIL® R 972. The other was the remarkable acceleration of the transformation from the anatase to rutile structure and grain growth/sintering of the thermally-treated fumed TiO₂ observed at a relatively low thermal treatment temperature by the oxidation reaction of calcium stearate as an external additive.     

Chemically Tuned p‐ and n‐Type WSe2 Monolayers with High Carrier Mobility for Advanced Electronics

Monolayers of transition metal dichalcogenides (TMDCs) have attracted a great interest for post‐silicon electronics and photonics due to their high carrier mobility, tunable bandgap, and atom‐thick 2D structure. With the analogy to conventional silicon electronics, establishing a method to convert TMDC to p‐ and n‐type semiconductors is essential for various device applications, such as complementary metal‐oxide‐semiconductor (CMOS) circuits and photovoltaics. Here, a successful control of the electrical polarity of monolayer WSe₂ is demonstrated by chemical doping. Two different molecules, 4‐nitrobenzenediazonium tetrafluoroborate and diethylenetriamine, are utilized to convert ambipolar WSe₂ field‐effect transistors (FETs) to p‐ and n‐type, respectively. Moreover, the chemically doped WSe₂ show increased effective carrier mobilities of 82 and 25 cm² V^?1s^?1 for holes and electrons, respectively, which are much higher than those of the pristine WSe₂. The doping effects are studied by photoluminescence, Raman, X‐ray photoelectron spectroscopy, and density functional theory. Chemically tuned WSe₂ FETs are integrated into CMOS inverters, exhibiting extremely low power consumption ( ≈ 0.17 nW). Furthermore, a p‐n junction within single WSe₂ grain is realized via spatially controlled chemical doping. The chemical doping method for controlling the transport properties of WSe₂ will contribute to the development of TMDC‐based advanced electronics.     

Estimating the imageability of words by mining visual characteristics from crawled image data

Multimedia Tools and Applications - Natural Language Processing and multi-modal analyses are key elements in many applications. However, the semantic gap is an everlasting problem, leading to...     

Colossal Barocaloric Effect by Large Latent Heat Produced by First-Order Intersite-Charge-Transfer Transition

Materials which show novel thermal properties can be used to make highly efficient and environmentally friendly energy systems for thermal energy storage and refrigeration through caloric effects. An A-site-ordered quadruple perovskite-structure oxide, NdCu₃Fe₄O₁₂, is found to release significant latent heat, 25.5 kJ kg⁻¹ (157 J cc⁻¹), at the intersite-charge-transfer transition temperature near room temperature. The transition is first-order and accompanied by an unusual magnetic ordering and a large negative-thermal-expansion-like volume change, and thus, it causes a large entropy change (84.2 J K⁻¹ kg⁻¹). The observed entropy change is comparable to the largest changes reported in inorganic solid materials, and more importantly, it is utilized through a colossal barocaloric effect. The adiabatic temperature change by applying 5.1 kbar pressure is estimated to reach 13.7 K, which means efficient refrigeration can be realized through this effect.     

Skeleton clustering by multi-robot monitoring for fall risk discovery

This paper tackles the problem of discovering subtle fall risks using skeleton clustering by multi-robot monitoring. We aim to identify whether a gait has fall risks and obtain useful information in inspecting fall risks. We employ clustering of walking postures and propose a similarity of two datasets with respect to the clusters. When a gait has fall risks, the similarity between the gait which is being observed and a normal gait which was monitored in advance exhibits a low value. In subtle fall risk discovery, unsafe skeletons, postures in which fall risks appear slightly as instabilities, are similar to safe skeletons and this fact causes the difficulty in clustering. To circumvent this difficulty, we propose two instability features, the horizontal deviation of the upper and lower bodies and the curvature of the back, which are sensitive to instabilities and a data preprocessing method which increases the ability to discriminate safe and unsafe skeletons. To evaluate our method, we prepare seven kinds of gait datasets of four persons. To identify whether a gait has fall risks, the first and second experiments use normal gait datasets of the same person and another person, respectively. The third experiments consider that how many skeletons are necessary to identify whether a gait has fall risks and then we inspect the obtained clusters. In clustering more than 500 skeletons, the combination of the proposed features and our preprocessing method discriminates gaits with fall risks and without fall risks and gathers unsafe skeletons into a few clusters.     

Superstructure and mechanical properties of poly(L-lactic acid) microfibers prepared by CO2 laser-thinning

Poly(L-lactic acid) (PLLA) microfibers were obtained by a carbon dioxide (CO₂) laser-thinning method. A laser-thinning apparatus used to continuously prepare microfibers was developed in our laboratory; it consisted of spools supplying and winding the fibers, a continuous-wave CO₂-laser emitter, a system supplying the fibers, and a traverse. The laser-thinning apparatus produced PLLA microfibers in the range of 100-800 m min⁻¹. The diameter of the microfibers decreased as the winding speed increased, and the birefringence increased as the winding speed increased. When microfibers, obtained through the laser irradiation (at a laser power of 8.0 W cm⁻²) of the original fiber supplied at 0.4 m min⁻¹, were wound at 800 m min⁻¹, they had a diameter of 1.37 μm and a birefringence of 24.1×10⁻³. The draw ratio calculated from the supplying and winding speeds was 2000×. The degree of crystal orientation increased with increasing the winding speed. Scanning electron microscopy showed that the microfibers obtained with the laser-thinning apparatus had smooth surfaces not roughened by laser ablation that were uniform in diameter. The PLLA microfiber, which was obtained under an optimum condition, had a Young's modulus of 5.8 GPa and tensile strength of 0.75 GPa.     

Monitoring behaviour of catabolic genes and change of microbial community structures in seawater microcosms during aromatic compound degradation

The behaviour of microbial populations responsible for degradation of the aromatic compounds, phenol, benzoate, and salicylate, and changes of microbial community structures in seawater microcosms were analysed quantitatively and qualitatively using MPN–PCR and PCR–DGGE. The purpose of the study was to investigate the ecology of the entire microbial community during bioremediation. Bacterial populations possessing catechol 1,2-dioxygenase (C12O) DNA were evidently the primary degraders of phenol and benzoate, but others possessing catechol 2,3-dioxygenase (C23O) DNA increased to enhance substrate degradation under high-load conditions when the substrates were present for long periods. However, salicylate degradation was evidently facilitated by specific bacterial populations possessing C23O DNA. PCR–DGGE analyses suggested that bacterial populations already relatively dominant in the original microcosm contributed to phenol degradation. Bacteria composing a minor fraction of the original population apparently increased and contributed to benzoate degradation. Bacterial populations possessing C23O DNA were responsible for salicylate degradation, however, and different degrading bacteria were evidently selected for, depending on the initial salicylate concentration. Microbial community structure tended to be simplified by aromatic compound degradation. Thus, microbial monitoring can elucidate the behaviour of bacterial populations responsible for aromatic compound degradation and be used to assess the effects of bioremediation on intact microbial ecosystems.     

Covered conduction of individual C(60) nanowhiskers

We investigate the electronic properties of individual C(60) nanowhiskers by exploiting conductive atomic force microscopy at room temperature in ambient atmosphere. The pristine individual C(60) nanowhiskers exhibit conducting behavior. The outer C(60) oxide covering, confirmed by Auger electron spectroscopy, shelters the conductive properties of the C(60) nanowhiskers. It is proposed that the insulating outer C(60) oxide covering might be used as the dielectric layer in potential single C(60) nanowhisker-based field-effect transistors for nanoelectronics.