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A high anionic conductivity of ∼3.5 × 10–3 S cm–1 at room temperature is achieved for PbxSn2–xF4 (x = 1.21) obtained by annealing a mechanically milled PbF2/SnF2 mixture at 400 °C. The observed syn...

We fabricated inorganic–organic hybrid quantum-dot light-emitting-diodes (QD-LEDs) consisting of several types of solution-processed n-type oxide electron injection layers (EILs)/quantum-dot (QD) and poly (9-vinylcarbazole) (PVK) blend light emitting layer (EMLs)/4,4-bis(carbazole-9yl)bihpheyl (CBP)/a-NPD/1,4,5,8,9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) hole injection layer/Al structures. We compared the electrical properties of hybrid QD-LEDs with solution-processed n-type oxide electron injection layers consisting of Al-doped ZnO nano-particles (AZO-NP), polyethyleneimine (PEI), titanium oxide nanosheet (TiO-NS) on PEI (PEI/TiO-NS), and AZO-NP/TiO-NS multilayers. The combination of the PEI dipole layer and ultra-thin TiO-NS nanosheet (∼1 nm) layers reduced the potential barrier at ITO/TiO-NS interface. However, a considerable barrier height of >0.3 eV exists at the TiO-NS/QD interface. The use of small-work function AZO-NP (3.9 eV) effectively improves external quantum efficiency (EQE) compared with relatively large work-function AZO-NP (4.3 eV) and TiO-NS (4.1 eV). The capacitance–voltage curves and the current density–voltage–luminance curves strongly depend on the thickness of the QD:PVK blend (2:1 in weight) layer, and we obtained the optimized thickness for EML as ca. 30 nm. With the improved charge balance and morphology, an EQE of above 3.0% is obtained for green light-emitting QD-LED and an EQE of 0.86% for blue light-emitting QD-LED.

We investigated the electronic structures of mono- and few-layered Ru nanosheets (N layers (L) with N = 1, ~6, and ~9) on Si substrate by ultra-violet and x-ray photoemission spectroscopies. The spectral density of states (DOS) near EF of ~6 L and 1 L is suppressed as it approaches EF in contrast to that of ~9 L, which is consistent with the Ru 3 d core-level shift indicating the reduction of the metallic conductivity. A power law g(ε) ∝ |ε − εF|α well reproduces the observed spectral DOS of ~6 L and 1 L. The evolution of the power factor α suggests that the transition from the metallic state of ~9 L to the 2-dimensional insulating state with the soft Coulomb gap of 1 L through the disordered 3-dimensional metallic state of ~6 L.

High rate capability is one of the most important properties in Li-ion batteries for electric vehicle and/or energy grid use. Herein, a high-power electrode material consisting of dual-substituted LiFePO4 by zirconium and silicon, Li(Fe0.95Zr0.05)(P0.9Si0.1)O4, was developed as it exhibits small lattice volume change between Li-rich and Li-poor phases. The dual-substituted cathode exhibited 1.1–4.4 times larger charge/discharge capacities for upper 10 C rates than that of the undoped material. Time-resolved XRD measurements at the high rate of 10 C revealed the formation of a metastable intermediate phase during the Li intercalation/deintercalation processes which triggers the continuous phase transition in Li(Fe0.95Zr0.05)(P0.9Si0.1)O4 with moderation of the lattice mismatch. Controlling the lattice volume change between the initial and end phase of the intercalation materials is key to achieving high rate capabilities.

The charge-discharge capacity of lithium secondary batteries is dependent on how many lithium ions can be reversibly extracted from (charge) and inserted into (discharge) the electrode active materials. In contrast, large structural changes during charging/discharging are unavoidable for electrode materials with large capacities, and thus there is great demand for developing materials with reversible structures. Herein, we demonstrate a reversible rocksalt to amorphous phase transition involving anion redox in a Li2TiS3 electrode active material with NaCl-type structure. We revealed that the lithium extraction during charging involves a change in site of the sulfur atom and the formation of S−S disulfide bonds, leading to a decrease in the crystallinity. Our results show great promise for the development of long-life lithium insertion/extraction materials, because the structural change clarified here is somewhat similar to that of optical phase-change materials used in DVD-RW discs, which exhibit excellent reversibility of the transition between crystalline and amorphous phase.

Li-rich type manganese oxides are one of the most promising cathodes for lithium-ion batteries in recent years; thanks to their high energy density. In these cathodes, partial substitution of manga...

Li-rich layered oxide (LLO) is a promising cathode material for lithium-ion batteries because of its large capacity in comparison with conventional layered rock-salt structure materials. In contrast to the conventional materials, it is known that LLO of 3d transition metal has a nanodomain microstructure; however, roles of each domain and effects of strain, induced by the microstructure, on electrode properties are still unclear. In this study, the influence of the strain on an electronic structure is studied to elucidate the stabilization mechanism of LLO material Li[Li0.2Ni0.2Mn0.6]O2 in the charged state by using resonant X-ray diffraction spectroscopy (RXDS), X-ray diffraction, and X-ray absorption spectroscopy (XAS) in combination with ab initio calculation. RXDS of a superlattice peak and XAS at Mn and Ni K-edges unveil that this material has a microstructure consisting of Mn-rich and Ni-rich domains, whose structures are similar to Li2MnO3 and LiNiO2, respectively. In the Ni-rich domain, trigonal d...

The structure of Fe-substituted Li 2 S-based positive electrode material Li 8 FeS 5 was analyzed using high-energy X-ray total scattering measurements. Pair distribution function (PDF) analyses indicated that the mechanically milled Li 8 FeS 5 sample could best be described as having an anti-fluorite structure in which Fe ions partially occupy Li sites in the Fm 3 ¯ m unit cell. The electrochemical properties of a cell utilizing Li 8 FeS 5 as the positive electrode were also consistent with this structural model.

We report the synthesis and electrochemical properties of Co-substituted manganese oxide nanosheets (Mn1–xCoxO2). Polycrystalline samples of layered Na0.6Mn1–xCoxO2 (x = 0.2–0.5) were synthesized as starting materials. A linear decrease in the lattice constant a with increasing Co content supported the successful substitution of Co3+ ions for Mn3+ ions in the host layers. Acid-exchange treatment of the Na0.6Mn1–xCoxO2 powders resulted in the formation of H–Mn1–xCoxO2 while preserving the Mn/Co ratio and layered structure. Exfoliation of H–Mn1–xCoxO2 was achieved by reaction with tetra–n–butylammonium ions, yielding unilamellar Mn1–xCoxO2 (x = 0.2–0.5) nanosheets with a thickness of 0.8 nm. The optical absorption peak of the obtained Mn1–xCoxO2 nanosheets was continuously blueshifted as the Co content increased. The Mn1–xCoxO2 nanosheets exhibited well-defined redox peaks, which were shifted to a negative potential with increasing Co content. These results suggest that the 3d orbitals of Mn and Co are mixe...

The origin of the capacity decrease of lithium- ion batteries during continuous charge/discharge cycling, as typified by battery operation in electric vehicles, is elucidated using LiNi1/3Co1/3Mn1/3O2 (NCM)-based composite electro- des. Electrochemical cycling tests without any rest process show the capacity decrease only during discharging. Reaction distribution analysis by operando energy-scanning confocal X- ray diffraction indicates that considerable reaction inhomoge- neity occurs on the lithiation of NCM during discharging, whereas the delithiation during charging proceeds homoge- neously. It is shown that the reaction inhomogeneity caused by limited Li+ transportation in the composite electrode is relaxed during charging owing to the potential profile of the NCM- based electrode, whereas no such relaxation occurs during discharging. This result demonstrates that the optimization of the electrode potential profile is important for good cyclability of the batteries in continuous charge/discharge cycling, in addition to improving Li+ transportation within the battery.

Rutile-type iridium dioxide (IrO2) is a well-known electrocatalyst, and its nanoparticle form has recently attracted attention as catalysts and co-catalysts in electrolyzers and fuel cells. In this study, we have successfully synthesized single crystalline iridium dioxide (IrO2) nanosheets with thickness of less than 0.7 nm via exfoliation of layered iridic acid H x Ir y O z ·nH2O, which was prepared via proton exchange of layered potassium iridate, K x Ir y O z ·nH2O. The electrochemically active surface area of the IrO2 nanosheet electrode was similar to or slightly lower than that of 3-nm IrO2 nanoparticles. Despite the lower active surface area, the mass activity for oxygen evolution reaction of IrO2 nanosheets was six times higher compared to that of IrO2 nanoparticles in 0.1 M HClO4 at 1.55 V vs. the reversible hydrogen electrode (17.4 vs. 2.9 A g−1). When IrO2 nanosheets were added to commercial Pt/C as a co-catalyst, increased stability against high potential cycling was obtained. After potential cycling between 1.0 and 1.5 V, the composite catalyst exhibited two times higher oxygen reduction activity compared to non-modified Pt/C. This durability enhancement is attributed to the suppression of the particle growth during the potential cycling test by the modification with IrO2 nanosheets.

We report the solid-state reaction of MoO2 nanosheets, obtained from the soft-chemical delamination of Na0.9Mo2O4, into metallic Mo2C single layers that constitute a new family of versatile carbide nanosheets. This so-called pseudotopotactic reaction, i.e., conversion from nanosheet to nanosheet, is aided by the use of cationic polymers as binders for the film growth based on electrostatic self-assembly. Compared to Mo2C in the bulk form, 2D anisotropic Mo2C sheets having a larger surface-area-to-volume ratio are of significant use in potential electrochemical applications, and it is also worth noting that the thickness of Mo2C sheets can be controlled in the nanometer range by altering the stacking number of the precursor nanosheets.

The homopolar network and conjugation in d-block single elements can materialize a highly anisotropic and robust structure of a noble-metal system. Here, we have prepared ruthenium (Ru) atomic monolayers of a nonmetallic hexagonal lattice, and determined their layering scheme and metallization. The two-dimensional (2D) network is retained at the first stacking of the monolayer, while maintaining the nonmetallic features. We find out that the atop (AA) related stacking structure of bilayered Ru nanosheets occurs due to the ligancy-driven covalency, and the inception of the metallic electronic states is from trilayered stacking. These results indicate that the metallic states can be separated from covalent-bonding linkage and unpaired electrons in spd hybrid orbital systems. Our approach enables the molecular structure of noble-metal atoms to be induced via controlling the ligancy of d-block atomic bonds.

LiFePO 4 is a practically used cathode material for lithium-ion batteries due to a high theoretical capacity, high cycle capability and the high-rate performance. The metastable Li x FePO 4 (L x FP) phase with an intermediate composition appears in the non-equilibrium state at high-rate condition. However, the formation process of the metastable L x FP phase and its impact to the electrochemical property are still unclear. In order to elucidate these points, we directly observed the phase transition behavior by applying operando XRD during 10C charge-discharge. L x FP phase does not form in charge reaction but preferentially forms in discharge reaction. The phase transition from L x FP to Li-rich phase is less likely to proceed in the end of discharge reaction. The asymmetric phase transition between LiFePO 4 and FePO 4 results in decreasing the discharge capacity and increasing the irreversible capacity at high-rate conditions.

Zinc is a promising negative electrode material for aqueous battery systems whereas it shows insufficient rechargeability for use in secondary batteries. It has been reported that leaf-like dendrite deposits are often the origin of cell-failure, however, their nature and behavior on discharge (oxidation) - charge (reduction) cycling have been only poorly understood. Here we investigate the transformation of the leaf-like zinc dendrites using ex-situ scanning electron microscopy, X-ray computational tomography and in-situ X-ray diffraction. It is shown that the leaf-like zinc dendrites obtained under diffusion-limited conditions are nearly completely dissolved at a low oxidation current density of 1 mA cm−2 and cause re-evolution of the zinc dendrites. Oxidation at a high current density of 10 mA cm−2 leads to the formation of leaf-like zinc oxide residual products that result in particulate zinc deposits in the following reduction process, enabling good rechargeability. The reaction behavior of this oxide residue is detailed and discussed for the development of long-life zinc electrodes.

A unique charge/discharge mechanism of amorphous TiS4 is reported. Amorphous transition metal polysulfide electrodes exhibit anomalous charge/discharge performance and should have a unique charge/discharge mechanism: neither the typical intercalation/deintercalation mechanism nor the conversion-type one, but a mixture of the two. Analyzing the mechanism of such electrodes has been a challenge because fewer tools are available to examine the “amorphous” structure. It is revealed that the electrode undergoes two distinct structural changes: (i) the deformation and formation of S–S disulfide bonds and (ii) changes in the coordination number of titanium. These structural changes proceed continuously and concertedly for Li insertion/extraction. The results of this study provide a novel and unique model of amorphous electrode materials with significantly larger capacities.

We developed spectroscopic X-ray diffraction (XRD) analysis to visualize electrochemical reactions occurring at various locations in Li-ion batteries (LIBs). Continuous irradiation with monochromatic X-rays in an energy region using a confocal setup provided a fixed observation position on the order of several tens of microns. Unlike three-dimensionally position sensitive XRD analyses, e.g., angle-scanning XRD and energy-dispersive XRD, this energy-scanning XRD analysis with angle-scanning of the monochromator instead of the detector-scanning has the advantage of profile resolution, position sensitivity, and time-resolution for mapping concentration gradients and diffusion of Li+ associated with the electrochemical properties of LIBs. The microscopic structural inhomogeneity in a sheet-like composite electrode of LiNi1/3Co1/3Mn1/3O2 with a thickness of 150 μm was successfully determined with a depth resolution of 50 μm during cell operation. This work demonstrates the potential of spectroscopic XRD as a n...

Capacity decrease at low temperatures is one of the issues to be solved for secondary batteries especially for automobile applications and it is thus important to clarify the reaction kinetics in operating batteries and identify the rate determining step that governs the performance at low temperatures. Phase transitions in electrode active materials are important factors that affect the reaction kinetics particularly for thin electrodes used in high power applications. In this study, the phase transition dynamics of thin LiNi0.5Mn1.5O4 electrodes at various temperatures is examined using electrochemical methods combined with temperature-controlled in situ X-ray diffraction analysis to directly capture the reacting species and elucidate the reaction mechanism. The analysis shows that there occur consecutive phase transitions of LiNi0.5Mn1.5O4 (Li1 phase) ↔ Li0.5Ni0.5Mn1.5O4 (Li0.5 phase) and the Li0.5 phase ↔ Ni0.5Mn1.5O4 (Li0 phase) at room temperature and above. At lower temperatures the transition of Li1 → Li0.5 proceeds during the charging process but further delithiation to form the Li0 phase is restricted, leading to the capacity decrease. On the other hand, on discharging at low temperatures the amount of the Li0 phase to be lithiated is limited and this causes the capacity decrease. There is no Li0.5 phase formation on discharging at low temperatures, revealing remarkable kinetic asymmetry of the reaction processes for charging and discharging. It is suggested that the Li0.5 phase formed on discharging is instantly lithiated to form the Li1 phase, due to the small potential gap between the two transitions. These results indicate that the phase transition kinetics of Li0.5 ↔ Li0 is slower than that of Li1 ↔ Li0.5 and the former transition is the rate determining step at low temperatures.

The electrochemical properties of a composite electrode for the lithium-ion battery consisting of exfoliated MoO2 nanosheets were investigated. The cell exhibited a high capacity of ca. 400 mA h g−...

The BL28XU beamline, dedicated to rechargeable battery analysis, is described., The newly installed BL28XU beamline at SPring-8 is dedicated to in situ structural and electronic analysis of rechargeable batteries. It supports the time range (1 ms to 100 s) and spatial range (1 µm to 1 mm) needed for battery analysis. Electrochemical apparatus for battery charging and discharging are available in experimental hutches and in a preparation room. Battery analysis can be carried out efficiently and effectively using X-ray diffraction, X-ray absorption fine-structure analysis and hard X-ray photoelectron spectroscopy. Here, the design and performance of the beamline are described, and preliminary results are presented.

The phase transition between LiFePO4 and FePO4 during nonequilibrium battery operation was tracked in real time using time-resolved X-ray diffraction. In conjunction with increasing current density, a metastable crystal phase appears in addition to the thermodynamically stable LiFePO4 and FePO4 phases. The metastable phase gradually diminishes under open-circuit conditions following electrochemical cycling. We propose a phase transition path that passes through the metastable phase and posit the new phase's role in decreasing the nucleation energy, accounting for the excellent rate capability of LiFePO4. This study is the first to report the measurement of a metastable crystal phase during the electrochemical phase transition of LixFePO4.

An electrode/electrolyte interface is obviously one of the most dominant factors controlling a battery performance. In the present work, a formation of a tin negative electrode/electrolyte interface (SEI) was investigated by an in situ X-ray reflectivity measurement. SEI was formed even at a high voltage of about 2.5 V vs Li/Li+. This voltage is much higher than the value of about 1.5 V in the previous works. Thus, SEI in the present work is clearly different from that formed by reductive decomposition of an electrolyte and/or reduction of Sn oxide. Its structure was seemingly an amorphous solid containing a quite amount of fluoride, which grows up to 150-200 nm thick by keeping for 1 h at about 2.5-2.6 V.

In-situ time-resolved X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) are applied to investigate the phase transition mechanism between LiFePO4 and FePO4. Phase formation kinetics is discussed by using the phase fractions of LiFePO4 and FePO4 directly obtained from the XRD measurement and the amount of the passed current synchronized by the XRD measurement with Kolmogorov-Johnson-Mehl-Avrami (KJMA) analysis. For both of the lithium extraction and insertion process, the KJMA analysis from the XRD and amount of the passed current data indicate that the phase formation of LiFePO4 and FePO4 proceeds via one-dimensional phase boundary movement. For the lithium extraction process, the two phase coexistence of LiFePO4 and FePO4 is observed under the potential step conditions, and the KJMA plot based on the passed current data is relatively in good agreement with the one based on the XRD data. On the other hand, for the lithium insertion process, considerable peak boarding which implies intermediate state formation during the phase transition occurs, and the LiFePO4 phase formation is delayed compared with the amount of the passed current, especially in the case of small particle size. These results indicate that the phase transition behavior during lithium insertion is different from that of the typical two phase reaction.

We have investigated the photovoltaic properties of an inverted bulk heterojunction (BHJ) cell in a device with an indium-tin-oxide (ITO)/electron selective layer (ESL)/P3HT:PCBM active layer/MoOx/Ag multilayered structure. The insertion of only single layer of poly(diallyl-dimethylammonium chloride) (PDDA) cationic polymer film (or poly(ethyleneimine) (PEI) polymeric interfacial dipole layer) and titanium oxide nanosheet (TN) films as an ESL effectively improved cell performance. Abnormal S-shaped curves were observed in the inverted BHJ cells owing to the contact resistance across the ITO/active layer interface and the ITO/PDDA/TN/active layer interface. The series resistance across the ITO/ESL interface in the inverted BHJ cell was successfully reduced using an interfacial layer with a positively charged surface potential with respect to ITO base electrode. The positive dipole in PEI and the electronic charge phenomena at the electrophoretic deposited TN (ED-TN) films on ITO contributed to the reduction of the contact resistance at the electrode interface. The surface potential measurement revealed that the energy alignment by the transfer of electronic charges from the ED-TN to the base electrodes. The insertion of the ESL with a large positive surface potential reduced the potential barrier for the electron injection at ITO/TN interface and it improved the photovoltaic properties of the inverted cell with an ITO/TN/active layer/MoOx/Ag structure.

A series of two-dimensional (2D) niobate nanosheets with a thickness controllable in increments of 0.4–0.5 nm were synthesized by chemically delaminating precursory layered perovskites into their unilamellar layers. The homologous layered compounds of KCa2Nan–3NbnO3n+1 for n = 4–6 were prepared as starting materials by repeated solid-state calcination of KCa2Nb3O10 (n = 3 analog) and NaNbO3 at 1573 K. These compounds were then converted into protonic forms and were further reacted with a tetrabutylammonium hydroxide solution to yield a translucent colloidal suspension. Nearly perfect delamination was confirmed by in situ X-ray diffraction (XRD) measurements on glue-like colloids centrifuged from the suspension, which showed total loss of basal diffraction series and an evolution of a broad, wavy pattern instead. The characteristic oscillating profile was dependent on n, or the layer thickness, and could be consistently reproduced by simulation in terms of X-ray scattering from the individual 2D fundamenta...

In ordered to prepare high capacitance pseudo-capacitive oxides, it is important to design nanostructures with appreciable mesopores. Supramolecular templating has become a popular method to synthesize ordered mesoporous metals; however, the application of the same technique to synthesis of high surface area oxides is more demanding. We present here, the synthesis of ordered mesoporous ruthenium metal by lyotropic liquid crystal templating and its electrochemical conversion to ordered mesoporous ruthenium oxide by a simple, room temperature procedure. The bulk, unsupported metallic ordered mesoporous ruthenium exhibits high surface area of 110 m(2) g(-1), which is comparable to typical supported Ru nanoparticles. The oxide analogue gives a high specific capacitance of 376 Fg(-1), owing to the porous structure. These results demonstrate a possible facile and generic process to synthesize oxides with ordered nanostructures by utilization of the various phases that can be obtained with lyotropic liquid crystalline templates such as cubic, hexagonal, lamellar, etc., Article, JOURNAL OF POWER SOURCES. 204:244-248 (2012)

A facile and scalable preparation of dispersion of isolated graphene in various organic solvents has been developed by combining between covalent and noncovalent functionalizations of the graphene surface. Covalently functionalized graphene (FRG) was prepared by the reaction of partially reduced graphene oxide with aryl diazonium salts, followed by the graphene oxide being completely reduced with hydrazine. The resulting FRG disperse readily in organic solvents such as N,N′-dimethylformamide (DMF) and N-methyl-2-pyrrolidinone and the functionalization of graphene was characterized by Fourier transform infrared spectroscopy, thermogravimetric thermogram, X-ray photoelectron spectroscopy, and Raman spectroscopy. The hydrophobic surface of FRG was noncovalently wrapped with aromatic hexakis-dodecylhexa-peri-benzocorone (HBC) by simply mixing of dispersion of FRG in DMF with toluene solution of HBC. The complexation of FRG and HBC was monitored by viewing the absorption and fluorescence spectral changes. Atomic force microscopic images confirmed that graphene was covalently and noncovalently functionalized, while keeping a two-dimensional sheet shape.

For the use of the zinc anode in secondary batteries, it is necessary to solve the “shape change” deterioration issue in that zinc species agglomerate in the center of the electrode to fade the available capacity. The local chemical compositions of the zinc electrodes during “shape change” were precisely analyzed using the synchrotron X-ray diffraction mapping analysis of practical zinc-nickel cells in a non-destructive manner. The in situ Zn/ZnO mapping shows that metallic Zn deposition chiefly occurs in the periphery of ZnO while ZnO are left in the center of electrode like a hill on charging. On discharging, the ZnO hill grows to the perpendicular direction on the electrode while metallic zinc is oxidized and dissolved. These findings allow us to propose a mechanism for the shape change; thus dissolved zincate species are decomposed on the ZnO hill during discharging to be accumulated in the center of the electrode. It is suggested that suppressing zincate dissolution and non-uniform zinc deposition slow the growth rate of the ZnO hill to enhance the cyclability of zinc-based secondary batteries.

Multilayer composite films comprising of TaO3 nanosheet crystallites and poly(diallyldimethylammonium chloride) (PDDA) were assembled via layer-by-layer sequential adsorption. Exposure of the resulting films to UV light promoted photocatalytic decomposition of PDDA in the nanosheet gallery to yield inorganic films. Novel hollow microspheres of Ta2O5 were fabricated by the deposition of a PDDA/TaO3 multilayer nanoshell on polystyrene (PS) beads and the subsequent removal of the PS core and PDDA layers via calcination. The hollow microspheres showed photocatalytic properties effective for hydrogen evolution from an aqueous methanol solution. The shape control into hollow microsphere greatly enhanced the photocatalytic activity. The results highlight the role of the surface area and crystallinity of the catalyst in photocatalytic activity.

We studied the effects of a hole buffer layer [molybdenum oxide (MoO3) and natural copper oxide layer] and a low-temperature-processed electron buffer layer on the performance of inverted bulk-heterojunction organic solar cells in a device consisting of indium–tin oxide (ITO)/poly(ethylene imine) (PEI)/titanium oxide nanosheet (TiO-NS)/poly(3-hexylthiopnehe) (P3HT):phenyl-C61-butyric acid methylester (PCBM)/oxide/anode (Ag or Cu). The insertion of ultrathin TiO-NS (~1 nm) and oxide hole buffer layers improved the open circuit voltage VOC, fill factor, and rectification properties owing to the effective hole blocking and electron transport properties of ultrathin TiO-NS, and to the enhanced work function difference between TiO-NS and the oxide hole buffer layer. The insertion of the TiO-NS contributed to the reduction in the potential barrier at the ITO/PEI/TiO-NS/active layer interface for electrons, and the insertion of the oxide hole buffer layer contributed to the reduction in the potential barrier for holes. The marked increase in the capacitance under positive biasing in the capacitance–voltage characteristics revealed that the combination of TiO-NS and MoO3 buffer layers contributes to the selective transport of electrons and holes, and blocks counter carriers at the active layer/oxide interface. The natural oxide layer of the copper electrode also acts as a hole buffer layer owing to the increase in the work function of the Cu surface in the inverted cells. The performance of the cell with evaporated MoO3 and Cu layers that were transfer-printed to the active layer was almost comparable to that of the cell with MoO3 and Ag layers directly evaporated onto the active layer. We also demonstrated comparable device performance in the cell with all-printed MoO3 and low-temperature-processed silver nanoparticles as an anode.

The intercalation chemistry of a layered protonic ruthenate, H{sub 0.2}RuO{sub 2.1}.nH{sub 2}O, derived from a layered potassium ruthenate was studied in detail. Three phases with different hydration states were isolated, H{sub 0.2}RuO{sub 2.1}.nH{sub 2}O (n={approx}0, 0.5, 0.9), and its reactivity with tetrabutylammonium ions (TBA{sup +}) was considered. The layered protonic ruthenate mono-hydrate readily reacted with TBA{sup +}, affording direct intercalation of bulky tetrabutylammonium ions into the interlayer gallery. Fine-tuning the reaction conditions allowed exfoliation of the layered ruthenate into elementary nanosheets and thereby a simplified one-step exfoliation was achieved. Microscopic observation by atomic force microscopy and transmission electron microscopy clearly showed the formation of unilamellar sheets with very high two-dimensional anisotropy, a thickness of only 1.3+-0.1 nm. The nanosheets were characterized by two-dimensional crystallites with the oblique cell of a=0.5610(8) nm, b=0.5121(6) nm and gamma=109.4(2){sup o} on the basis of in-plane diffraction analysis. - Graphical abstract: Layered protonic ruthenate derived from a potassium form was directly reacted with bulky tetrabutylammonium ions to trigger exfoliation into nanosheets as long as it is highly hydrated.

The bulk layered compound KLa0.90Sm0.05Nb2O7 and its exfoliated form of La0.90Sm0.05Nb2O7 nanosheet have been prepared, and their photoluminescence properties have been characterized. The photoluminescence emission of KLa0.90Sm0.05Nb2O7 via host excitation is negligibly low in intensity, whereas the emission via direct Sm3+ excitation has apparently been observed. On the contrary, the emission via direct Sm3+ excitation is preferentially quenched, and the emission via host excitation becomes far more predominant than that via direct Sm3+ excitation for the exfoliated La0.90Sm0.05Nb2O7 nanosheet. From the comparison of photoluminescence properties between the bulk layered compound KLa0.90Sm0.05Nb2O7 and its exfoliated form of La0.90Sm0.05Nb2O7 nanosheet, the relative enhancement of the host excitation-mediated photoluminescence by exfoliation of bulk Ln-photoactivated layered phosphors into nanosheets as a general trend has become more apparent.

Synchrotron radiation in-plane X-ray diffraction was applied to titania nanosheet monolayer film to monitor surface structural change during conversion from hydrophobic to hydrophilic state induced by UV irradiation. Slight but significant expansion/contraction of two-dimensional lattice parameters occurred in synchrony with surface wettability switching, suggesting structural modification is associated with photoinduced hydrophilic conversion.

Eu3+-activated double perovskite-type nanosheet phosphor (K1.5Eu0.5)Ta3O10 has been prepared by the soft chemical exfoliation reaction of K(K1.5Eu0.5)Ta3O10 bulk precursor. The lateral size of the nanosheet product ranges from 0.1 to a few micrometers, and the thickness is uniformly 2.4(2) nm. The lattice parameter along the sheet direction obtained by the in-plane X-ray diffraction is 0.3933(3) nm, corresponding to the typical O−Ta−O distances. The photoluminescence emission can be obtained either by host or by direct photoactivator excitation, but the host excitation yields much higher emission intensity than does the direct photoactivator excitation. The emission spectra show relatively sharp peaks from the 5D0 → 7FJ manifold transitions of Eu3+. The highest emission intensity is observed around 704 nm (far-red) from the 5D0 → 7F4 transition of Eu3+.

Interfaces between LiCoO 2 and sulfide solid electrolytes were modified in order to enhance the high-rate capability of solid-state lithium batteries. Thin films of oxide solid electrolytes, Li 4 Ti 5 O 12 , LiNbO 3 , and LiTaO 3 , were interposed at the interfaces as buffer layers. Changes in the high-rate performance upon heat treatment revealed that the buffer layer should be formed at low temperature to avoid thermal diffusion of the elements. Buffer layers of LiNbO 3 and LiTaO 3 can be formed at low temperature for the interfacial modification, because they show high ionic conduction in their amorphous states, and so are more effective than Li 4 Ti 5 O 12 for high-power densities.

A prototype transition-edge sensor (TES) microcalorimeter is successfully integrated into a commercial field-emission scanning electron microscope (FE-SEM). The microcalorimeter is composed of a gold (Au) absorber, a Au/Ti bilayer thermometer and a thermal isolation structure with a SiNx membrane. Operating temperatures of 100–150 mK are obtained with a dilution refrigerator. The measured energy resolution was between 19–22 eV for Al Kα at an acceleration voltage of 5 keV. The newly developed system was applied to the analysis of nanosheets for the first time at a low acceleration voltage (≤ 5 kV). The energy dispersive spectrometer (EDS) spectra of Nb3O8 nanosheets of different thicknesses (less than 20 nm) were successfully detected. Moreover, Au particles on carbon nanotubes with a thickness less than 1 nm are detected clearly. With further improvement of both energy resolution and count rate, this system holds the promise for practical X-ray compositional characterization of nanomaterials with high image spatial resolution in the low-acceleration-voltage regime.

Multilayer heterostructured films of two different nanosheets, semiconducting Ti0.91O2 nanosheets and redoxable MnO2 nanosheets, were fabricated by the layer-by-layer sequential adsorption method using a polyelectrolyte as a linker. Successful deposition of these two nanosheets in various sequences was confirmed by monitoring UV−visible absorption spectra and X-ray diffraction data on the films. We examined how nanostructures of the heteroassembled films affect the behaviors of photoinduced electron transfer between the two types of nanosheets and electrochemical properties of composite film electrodes. The excitation of Ti0.91O2 nanosheets under light irradiation at 280 nm was found to cause a gradual decrease in intensity of the optical absorption peak at 372 nm, which can be ascribed to the reduction of Mn4+ to Mn3+ of MnO2 nanosheets as confirmed by XANES spectra. This behavior can be understood by a scheme that the excited electrons produced in Ti0.91O2 nanosheets are injected into MnO2 nanosheets. T...

High photoactivator concentration nanosheets Eu0.56Ta2O7 have been prepared by the soft chemical exfoliation reaction of the layered perovskite Li2-xHxEu0.56Ta2O7 with a tetrabutylammonium hydroxide aqueous solution. In-plane X-ray diffraction and TEM and AFM observation results indicate that the Eu0.56Ta2O7 nanosheet is crystalline and retains the layered perovskite structural feature of the bulk precursors. The most intense emission is observed from the 5D0 → 7F2 transition of Eu3+. The intensity of this emission by the host excitation exceeds 18 times that by the direct Eu3+ excitation.