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Ferricyanide/ferrocyanide/guanidinium-based thermoelectrochemical cells have been investigated under different loading conditions in this work. Compared with ferricyanide/ferrocyanide-based devices, the device with guanidinium-added electrolytes shows higher power and energy densities. We observed that the enhanced performance is not due to the ionic Seebeck effect of guanidinium but because of the configuration entropy change resulting from the selective binding of Gdm

With the aid of large Seebeck coefficients, over 1 mV K−1, redox-free ionic conductors have the potential to be used as a component of thermally chargeable supercapacitors and/or thermopiles. To date, most ionic conductors reported exhibit p-type polarity; therefore, it is challenging to develop thermoelectric (TE) supercapacitor modules comprising both p- and n-type TE legs due to the lack of n-type ionic conductors. Herein, we found that the intrinsically p-type polarity of alkylmethylimidazolium chloride (Rmim:Cl)-based ionic hydrogels could be converted into n-type, using poly(3,3-ethylenedioxythiophene):poly(styrenesulfonyl) (PEDOT:PSS)-conducting polymer electrodes. Complementary characterization of the TE voltage response and absorption spectroscopy suggests that “negative” interfacial polarization is induced under asymmetric heating. This results from the ion exchange between PEDOT:PSS and Rmim:Cl upon creating the interfaces and the high affinity of Rmim:PSS compared with PEDOT:Cl, which results in the n-type TE response. Our findings offer a useful method for tuning the polarity of TE supercapacitors by tailoring the ion/electrode interactions despite the use of an identical electrolyte.

The development of stretchable elastomer composites with considerable mechanical strength and electrical conductivity is desired for future applications in communication tools, healthcare, and robotics. Herein, we have developed a novel stretchable elastomer composite by employing a slide-ring (SR) material as a matrix for restoration and graphene oxide (GO) as a precursor for a conductive filler. Highly dispersed GO in an organic solvent, prepared via a new method developed by the authors, allowed the uniform dispersion of GO into the matrix by simply mixing the solvent and SR. The resultant SR/GO composite exhibited considerably high mechanical toughness and cyclic durability. These properties were approximately maintained after pulse laser irradiation to add electrical conductivity on the composite by photoreducing of the dispersed GO, and its electrical conductivity was higher than that of the SR/graphene, carbon nanotubes, or graphite composites. The potential of the SR/GO composite as a stretchable base substrate for wearable devices was demonstrated by producing a prototype humidity sensor, a human motion monitoring sensor, and an electrical heater based on the composite with conductive circuits drawn using pulse laser patterning.

This paper shows how protonated 3,4-ethylene dioxythiophene moieties can be used as an end group to make organic conductors. An organic semiconductor 2,5-bis(5-(2,3-dihydrothieno[3,4

The feasibility of using organic thermoelectric devices to power sensors for different applications is a critical area of interest for researchers. Organic semiconductors possess lower thermoelectric performance than their inorganic counterparts, however, this can be compensated for by certain advantages, such as their light weight, low fabrication costs, and low fabrication temperatures. For practical applications, they face competition with Li-ion batteries, which are known for their high energy densities and long lifetimes. Thus, in addition to having a suitable corresponding power output, ideal organic thermoelectric devices require excellent stability. In this study, such a perspective was examined via primarily focusing on recent studies of organic thermoelectric devices and, particularly, their practical applications. The impact of contact resistance on device performance has been discussed, together with suggestions of certain promising device structures for organic thermoelectric devices. Experimentally, it was confirmed that light and compact organic thermoelectric devices with a size of ∼10 cm2 should be sufficiently suitable to power sensors. Moreover, these devices were confirmed to operate under natural cooling conditions without a heat sink, thus showing excellent stability for >70 days under continuous working conditions at 100 °C.

Maximizing the power outputs of devices using benchmark materials is critical for the application of organic thermoelectrics. We report the fabrication of thermoelectric devices using poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) with a Ni foil and polyimide film. The shape of the Ni foil was designed to match the thermal and electrical resistance of the poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) film. Due to the low thermal conductivity of the organic materials, a stable temperature difference of 50 K was achieved under natural cooling conditions without a heat sink at 100 °C. As a result, the device exhibited a power density of 40 μW/cm2, nearly double that of the unoptimized device.

Thermoelectric properties of organic semiconductors have recently attracted attention owing to their remarkable electrical conductivity, power factor, and figure of merit. Herein, the authors first simply introduce the history of the organic thermoelectric materials; then, they summarize the recent efforts toward improving the thermoelectric properties of p- and n-type organic semiconductors. The p-type semiconductors have been divided into two groups: poly(3,4-ethylenedioxythiophene)-based materials, doped during the polymerization, and the others, which are typically nonconductive and can be molecularly doped after film formation. A couple of examples of n-type organic thermoelectric materials are also presented. Finally, the anisotropic thermoelectric properties and their measurements are discussed.

Thermoelectric power generation from waste heat is an important component of future sustainable development. Ion-conducting materials are promising candidates because of their high Seebeck coefficients. This study demonstrates that ionic hydrogels based on imidazolium chloride salts exhibit outstanding Seebeck coefficients of up to 10 mV K

The contact resistance at conducting polymer-electrode junctions could substantially affect device performance because electrical currents or signals generated in the polymer devices must be transferred in their final form through the junctions to the connected load or devices. We report here the specific contact resistance between the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and a metal electrode as measured by a transmission line technique. Toward developing printed electronics that do not require vacuum processes, we focus on the specific contact-resistance, rc, between PEDOT:PSS films and metal pastes. Addition of a second solvent such as ethylene glycol (EG), poly-ethylene glycol (PEG), and dimethyl sulfoxide (DMSO) to PEDOT:PSS solution for film formation induced a significant reduction of rc together with an enhancement of electrical conductivity. A surface treatment using EG or DMSO on electrode areas of the film also decreased rc at the PEDOT:PSS-Ag paste junction to the value at the PEDOT:PSS-Ag junction formed by electron-beam evaporation. The mechanism of reduction of rc is discussed based on morphology of the PEDOT:PSS film.

This study reports a thermo-electrochemical cell based on ionic liquids 1-buty1-3-methylimidazolium chloride·FeCl3 and 1-buty1-3-methylimidazolium chloride·FeCl2. This system showed a high ion conductivity of ca.7 S m−1, a low charge transfer resistance of 0.9 Ω cm2 on a Pt electrode, and a thermopower of 0.26 mV K−1. Because the oxidized form of 1-buty1-3-methylimidazolium chloride·FeCl3 is paramagnetic, the diffusion was controllable under a magnetic field. When a magnet was touched to one of the electrodes of the thermo-electrochemical cell, a potential difference of several mV was generated. The unique properties of the magnetic ionic liquid redox couple suggest new possibilities for simultaneously harvesting thermal and mechanical energies.

We report the transport properties of nonwoven fabric-composite thermoelectric (TE) elements impregnated with the polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The porous structure formed in the fabric after the solvent evaporation of the PEDOT:PSS solution resulted in a high thermal resistance. In addition, the polymer films covering the surface of the fibers in the fabric connected the fibers to form electrical conduction paths, resulting in isotropic electrical conductivity at high PEDOT:PSS concentrations. These two factors provided the optimum PEDOT:PSS concentration for the TE power density per PEDOT:PSS content. Optimizing the TE power density per polymer content could contribute to the low-cost fabrication of TE modules from conducting polymers. We also demonstrated that the flexible TE module fabricated from the nonwoven fabric-composite achieved a power output sufficient to power a light-emitting diode. Contact electrical resistance at polymer-electrode junctions was greatly reduced by the increase in contact area arising from the wavy surface of the fabric composite.

We show that conducting polymer Poly (3,4-ethylene dioxythiophene)/poly (styrene sulfonate) film could be an ideal electrode in thermo-electrochemical cells, which shows a low charge transfer resistance. Using ferricyanide/ferrocyanide as an electrolyte, the Poly (3,4-ethylene dioxythiophene)/poly (styrene sulfonate) based thermo-electrochemical cell could be used to drive light-emitting diodes array. The conducting polymers also show the advantage of hybrid insoluble redox couples such as Prussian blue analog materials, making it easy to measure the temperature-dependent redox potential. By a combination of proper redox couples, the thermally regenerative electrochemical cells could realize. The power could generate during the environmental temperature change.

Measuring and understanding the interfacial resistance between the electrode and electrolyte are critically important for fabricating high-performance thermoelectrochemical cells. Although the charge transfer resistance and other resistance, such as the mass transfer resistance, may measure via electrochemical impedance spectroscopy, the resolution of the charge transfer semicircle in the Cole–Cole plot can decrease if these resistance values are smaller than the solution resistances. Moreover, a small dataset at a very low frequency can affect the analysis results. In this study, the transmission line measurement was applied, which is used in semiconductor physics to determine the contact resistance between a metal and a semiconductor, to thermoelectrochemical cells for simultaneously determining the interfacial and solution resistances. This method was used to quantify the direct-current interfacial and solution resistances, which are directly linked to the power output of cells under different temperatures. Because of a wide applicable concentration range, the interfacial reaction rate constant at high electrolyte concentration could be calculated from the transmission line measurement. Through a comparison with electrochemical impedance spectroscopy results, we concluded that the interfacial resistance is dominated not by the charge transfer resistance but by the mass transfer resistance, which could be dependent on the surface energy of the electrodes.

Single-walled carbon nanotubes (SWCNTs) have the potential for application in thermoelectric energy generators owing to their advantages, such as good charge-carrier transport properties, mechanical flexibility and robustness, and tunability of polarity. However, the fabrication of SWCNTs still remains a problem due to its complexity and high cost. In this paper, we propose an approach for the direct formation of free-standing SWCNT films from as-grown SWCNT mats without any dispersion or separation processes. We used this approach to develop high-performance SWCNT-based thermoelectric leg materials. The as-grown SWCNT mats were synthesized by an enhanced direct injection pyrolytic synthesis (eDIPS) method. The selectivity of the tube diameter for the eDIPS method clarified the dependence of the thermoelectric performance of the free-standing SWCNT films on the tube diameter. The Seebeck coefficients and thermal conductivities were found to correlate with the tube diameter and agreed with the theoretical predictions. Owing to the dispersion-free film formation, our SWCNT films afforded large thermoelectric power factors. In particular, a power factor of 350 μW/(m K2) was obtained for the mean tube diameter of 1.7 nm without any semiconductor extraction or doping treatments. Our approach allowed the fabrication of thermoelectric legs with an arbitrary size; thus, it offers a useful strategy for the simpler, cheaper, and low-waste manufacturing of high-performance organic thermoelectric devices.

The through-plane conductivity of a film sample is critically important because it largely affects the performance of batteries, capacitors, and thermoelectric devices. In this study, we developed a modified four-probe through-plane electrical conductivity measurement method using a coaxial structure. This method is general and works for free-standing film samples. We studied different samples including a steel sheet, highly oriented pyrolytic graphite, and conducting polymers. We confirmed metallic transportation in the steel sheet and hopping transportation in graphite in the through-plane direction by conducting low temperature measurements at 100 K. In the case of a conducting polymer poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate, the conductivity anisotropic ratio decreases with increasing in-plane conductivity. Temperature dependent measurements show two distinct activation energy regimes in the through-plane direction in PEDOT/PSS but almost no change in the in-plane electrical conductivity activation energy. This could be due to additional carrier paths that occur through the more disordered region (the PSS-rich region) in the through-plane direction. We also examined the Meyer–Neldel rule in PEDOT/PSS and concluded that PEDOT/PSS follows the anti-Meyer–Neldel rule, likely due to the high carrier density in the film.

Imidazolium chloride salt was demonstrated as a novel water-processable, strong base-free electron dopant for single-walled carbon nanotubes (SWCNTs). By thermoelectric evaluation and various photoelectron spectroscopy analyses associated with the comparison of the redox potentials, the valence change of the anion (Cl-/Cl3-) was presented as a possible mechanism for electron injection into the nanotube conduction band. The obtained n-type SWCNT films presented good thermoelectric power factor exceeding 100 μW m−1 K−2, nearly identical to that of the original p-type film.

Charge-carrier mobility is an important and crucial performance criterion for organic semiconductors and nanocarbon materials such as carbon nanotubes (CNTs). Although high conductivity has been achieved in highly doped organic semiconductors and CNT networks, reliable measurements of charge-carrier mobility in such disordered materials remain a challenge. Here, we developed and extended a new mobility measurement method, referred to as photoinduced charge transfer, from conducting polymers to nanocarbon materials. We apply this method to examine the carrier mobility of graphene, where the carrier mobility can be extracted using a Hall-effect measurement. By comparing the mobility values obtained using these two methods, we can understand the potential errors in the mobility values extracted using photoinduced dedoping reactions. We further extend this approach to disordered CNT networks and determine the relationship among CNT structure, defects, and carrier mobility.

A novel conducting polymer, Poly(3-methoxythiophene-2,5-diyl-co-3,4-ethylenedioxythiophene-2,5-diyl]/tosylate (P1/tos), was synthesized by oxidative in situ polymerization using Fe(tos) 3 as an oxidant. Compared with poly(3,4-ethylenedioxythiophene) (PEDOT), P1 has a deeper HOMO level and a wider energy gap as observed by ultraviolet–visible spectroscopy and photoelectron yield spectroscopy. P1/tos showed electrical conductivity of 10 S/cm and a carrier mobility of about 0.6 cm 2 /(V s), which was extracted by using ion-gel thin film transistors. The calculated carrier concentration was on the order of 10 20 cm −3 , which is lower than that of PEDOT/tos. The Seebeck coefficient of P1/tos was higher than that of PEDOT/tos.

We report organic thermoelectric modules screen-printed on paper by using conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and silver paste. Our large-area devices provided sufficient power to illuminate light-emitting diodes. This is the first example of thermoelectric modules containing conducting polymers being used to power practical devices. The stability of this proof-of-concept module was tested at 100 °C for over 100 h without any encapsulation. We showed that the decrease in device performance was caused not by the deterioration of the materials but by degradation of the interface between the conducting polymers and silver paste. These results suggest that organic thermoelectric modules could be used to harvest heat energy at low temperature, although the stability of the interface must be improved.

Exploring the various applications of conjugated polymers requires systematic studies of their physical properties as a function of the doping density, which, consequently, calls for precise control of their doping density. In this study, we report a novel solid-state photoinduced charge-transfer reaction that dedopes highly conductive polyelectrolyte complexes such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate). Varying the UV-irradiation time of this material allows the carrier density inside the film to be precisely controlled over more than 3 orders of magnitude. We extract the carrier density, carrier mobility, and Seebeck coefficient at different doping levels to obtain a clear image of carrier-transport mechanisms. This approach not only leads to a better understanding of the physical properties of the conducting polymer but also is useful for developing applications requiring patterned, large-area conducting polymers.

We measured electrical conductance of single crystalline boron nanobelts having α -tetragonal crystalline structure. The doping experiment of Mg was carried out by vapor diffusion method. The pure boron nanobelt is a p-type semiconductor and its electrical conductivity was estimated to be on the order of 10 –3 (Ω cm) −1 at room temperature. The carrier mobility of pure boron nanobelt was measured to be on the order of 10 −3 (cm 2 Vs −1 ) at room temperature and has an activation energy of ∼0.19 eV. The Mg-doped boron nanobelts have the same α -tetragonal crystalline structure as the pristine nanobelts. After Mg vapor diffusion, the nanobelts were still semiconductor, while the electrical conductance increased by a factor of 100–500. Transition to metal or superconductor by doping was not observed.

Polycrystalline β -rhombohedral boron films mixed with amorphous boron phase have been successfully fabricated on quartz substrates using pulsed laser ablation in a quartz glass tube chamber placed in an electric furnace. The crystallinity of the films strongly depended on the temperature of the furnace and the pressure of background argon gas. High temperature and high pressure in the chamber were suitable for crystallized boron film preparation. The best crystalline films (without B 2 O 3 phase formation) were obtained at 1000°C, 100 Pa. XPS measurements demonstrated that the major contaminants were carbon and oxygen, and the atomic ratio of oxygen to boron was 0.05 under the preparation conditions of well-crystallized films. The surface roughness of the films decreased by lowering laser energy to 150 mJ/pulse under the same pressure and temperature conditions.

Icosahedral AlPdRe quasicrystals show primarily semiconductor-like electronic properties and low thermal conductivity. We present the composition dependence of the electrical conductivity and Seebeck coefficient for icosahedral AlPdRe. The strong composition dependence is considered to be related to the pseudogap structure in the electron density of states at the Fermi energy, and to the variation in the bonding nature between Al and transition metals. The temperature dependence of the electrical properties has been analyzed using a two-band model. The results obtained suggest that the effective mass plays an important role in the improvement of thermoelectric properties. The dimensionless thermoelectric figure of merit, ZT, has a maximum value of approximately 0.1 in the temperature range from 600 to 700 K and reveals a strong composition dependence.

The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples. In a temperature range of 200-450 K, there is a crossover between electrical conduction by variable-range hopping and phonon-assisted hopping. The inhomogeneous carbon concentration and planar defects, such as twins and stacking faults, in the nanowires are thought to modify the bonding nature and electronic structure of the boron carbide crystal substantially, causing differences in the electrical conductivity and Seebeck coefficient. The effect of boundary scattering of phonon at nanostructured surface on the thermal conductivity reduction is discussed.

Boron- or Aluminum-rich icosahedral cluster solids (ICS) consist mainly of B12 or Al12 icosahedral clusters. In the ICS, a slight change of the structure or environment of icosahedral cluster can cause metallic-covalent bonding conversion, which can cause that the electrical conductivity σ and the Seebeck coefficient S can be as high as those of metals and semiconductors, respectively. Five-fold symmetry of the icosahedral cluster does not match with the translational symmetry of a crystal, consequently makes lower thermal conductivity with complex structure. For these reasons, ICS are promising candidates for thermoelectric materials.Using MEM/Rietvelt method, we successfully obtained the clear image of the electron density distribution for alpha-AlReSi approximant crystal. The bond strength distributes widely from weak metallic to strong covalent bond, and the intra-cluster bonds are stronger than the inter-cluster ones. This means that alpha-AlReSi is located at the intermediate state of molecular, metallic- and covalent-bonded solids. Composition dependences of atomic density and quasi-lattice constant for AlPdRe icosahedral quasicrystals show the above situation is the same in the quasicrystals. The thermoelectric figure of merit Z and the effective mass m* of AlPdRe quasicrystals can be increased by strengthening the intra- and weakening the inter-cluster bonds. According to this scenario, Z was improved by a factor of 1.5 by substitution of Ru for Re.In β-rhombohedral boron, several interstitial sites, which have space large enough to accommodate foreign atoms, are known. For the V doped sample, in which V atoms mainly occupy A1 site, the metallic-covalent bonding conversion may occur, σ is increased very much, S is decreased even to negative value and kappa is decreased. The maximum and n-type ZT value is obtained and is approaching to that of B4C, which is considered to have the largest and p-type ZT value in boron-rich ICS.

We obtained thin films of the AlPdRe icosahedral quasicrystals by molecular beam epitaxy and post-annealing. The thickness of the films was estimated to be smaller than 100 nm. Any preferred orientation in the X-ray diffraction peaks was not observed in the films.

We report an increase in the thermoelectric power factor of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) from 23 ± 5 to 225 ± 130 µW/(m·K2) in high-humidity conditions. This enhancement was caused mainly by an increase in the apparent Seebeck coefficient, which could be related to morphological change after water absorption or electrochemical reaction of PEDOT in air. Our results demonstrate a positive effect of water in the PEDOT:PSS system and indicate the need for well-controlled measurement conditions, particularly humidity, in evaluating the performance of conducting organic materials.

Metallic-covalent bonding conversion in icosahedral clusters of Al and B by small changes of the structure was demonstrated by molecular orbital calculations. According to the electron density distribution obtained using the maximum entropy method and the Rietveld method, the bonding conversion phenomenon occurs even in cluster solids such as some Al- and B-based icosahedral approximant phases (Al12Re, α-AlMnSi, α-rhombohedral boron). The multiple-shell atomic structure, the electrical and optical conductivity are compared for metal doped β-rhombohedral boron and AlLiCu or AlPdRe icosahedral quasicrystal. Photoemission and electron energy loss spectroscopy investigations for V doped β-rhombohedral have been discussed. Conclusions are the following two. It is difficult to distinguish a Hume-Rothery, i.e. structure-induced, pseudogap, and a covalent bonding, i.e. hybridization, pseudogap for materials with a highly symmetric Brillouin zone and a strong potential for valence electrons. Because hybridization is necessary not only for covalent bonds but also for metallic ones, it is better to use the covalent bonding pseudogap than the hybridization pseudogap.

We report the thermoelectric properties of single-crystalline boron nanobelts with α-tetragonal boron crystal. After the fabrication of a microheater and microelectrodes, the thermoelectric voltage was successfully measured by an AC measurement method (the 2ω technique). The boron nanobelts were found to possess the highest power factor among all of the boron crystals and amorphous solids. They are expected to be candidate thermoelectric materials for use at high temperatures. The Seebeck coefficient and electrical conductivity strongly depend on the distribution of localized states in the band gap.

We report the effects of a neutron-capture reaction of isotope B10 on the structure and electrical transport of B10-enriched single-crystalline boron nanobelts. Partial amorphization, particularly at the surface of the nanobelt, was observed after thermal neutron irradiation with a dose of 2×1019 cm−2. Carrier doping into the nanobelts by neutron transmutation is expected after postannealing. The change in conductance is discussed based on the distribution of localized states in the band gap of α-tetragonal boron.

Boron forms unusual structures and chemical bonds. Pure boron and many boron-rich borides have local icosahedra in their crystalline structures. The electron density distribution (EDD) in β-rhombohedral boron (β-B105) is visualized by the maximum entropy method (MEM)/Rietveld analysis of powder X-ray diffraction (XRD) data in order to discuss the peculiarity of the chemical bonds. In α-rhombohedral boron (α-B12) and its derivative crystals, peculiar covalent bonds, i.e., intracluster three-center bonds and intercluster bent bonds, have been observed. In β-B105, the intracluster three-center bonds are observed, but the intercluster bent bonds are not. The origin of the bent bond can be explained by the mismatch in the directions of the bond and the lattice vector.

The thermoelectric properties of quaternary icosahedral AlPdReFe quasicrystals obtained by replacing Re with Fe in icosahedral AlPdRe quasicrystals have been studied according to the guiding principle of weakly bonded rigid heavy clusters (WBRHCs). Anisotropy in the microstructures of arc-melted and annealed samples was found, and the electrical and thermal conductivities are larger in the direction perpendicular to the bottom of the arc-melted button than in the parallel case. The dimensionless figure of merit (ZT) in the perpendicular direction was increased 2.6 times from 0.08 to 0.21 by Fe substitution for Re in the icosahedral AlPdRe quasicrystals, which was caused by the increase of the Seebeck coefficient and the decrease of the phonon thermal conductivity, and the increase of the electrical conductivity, expected and not for the WBRHCs, respectively.

Au/SiO2 nanocomposite films consisting of an extremely high number density of Au nanoparticles dispersed in a SiO2 matrix a few nanometres thick were deposited by a co-sputtering method, and employed for molecular conductance measurement by immobilizing and bridging conjugated biphenyl molecules on dispersed Au nanoparticles. The number density of Au nanoparticles in the insulating SiO2 matrix was approximately 14 000 µm−2, and the average interparticle distance from their neighbours was about 8 nm. The current increased considerably up to the range of nanoamperes after the immobilization of the conjugated biphenyl molecules, 105 times larger than without molecules before immobilization. Although the Au nanoparticles can be connected to only 30% of all combinations of neighbouring Au nanoparticles by biphenyl molecules 2.4 nm long from the topological analysis, the biphenyl molecules can bridge most of the Au nanoparticles, and their bridging continuity is over 100 nm in length. Thus the measured current is suggested to come from the continuously bridged molecules between the Au nanoparticles. Furthermore the I–V data of the whole Au/SiO2 nanocomposite film immobilized with conjugated molecules are confirmed to be in a reasonable range in comparison with the scanning tunnelling spectroscopy data of similar conjugated molecules.

Boron carbide (B 12 C 3 ) and boron phosphide (B 12 P 2 ) have the similar structures to α-rhombohedral boron (α-B 12 ) and are considered to be derivative crystals of it. The peculiar bonds in these two derivative crystals are visualized by MEM/Rietveld analysis, which involves a combination of the maximum entropy method (MEM) and Rietveld refinement for powder X-ray diffraction (XRD) data. The distinctive bending of bonds observed in α-B 12 is reversed by an insertion of other atoms. This bending arises from the conflict between the crystal structure of the rhombohedral lattice and the icosahedral structure of the B 12 cluster. Bond strength and interatomic distances are also varied by the insertion. In order to estimate the bond strength, we obtained the electron density height at each bond critical point, and compared it with the force constant, which is derived from the Raman shift.

This letter describes the dependence of photocurrent of single-crystalline boron nanobelts on the atmosphere. In ambient air, slow photoresponse under blue light illumination was observed. Rise and decay times exceeded three days. The magnitude of photoresponse in ambient air and oxygen was greater than that in hydrogen and argon atmospheres. In vacuum, a photoresistivity effect consisting of the continuous decrease of conductance under blue light illumination was observed. Variation of band bending of the nanobelt surface by adsorption or desorption of oxygen and water molecules appeared to switch the photoconduction on and off by the respective trapping and recombination of photoexcited carriers at the nanobelt core and surface.

We developed a safe technique without using a toxic gas source to deposit tungsten oxide on a localized specific area using an atmospheric pressure microplasma jet. In this technique, a consumable tungsten wire, inserted into a quartz nozzle for microplasma generation, was etched with an O2/Ar microplasma, and the resultant tungsten oxide was deposited on the substrate placed downstream. The process mechanism was determined by the detailed observation of the deposit and consumed wire surface after processing, and optical emission spectroscopy. This technique is expected to be utilized for the localized deposition of a variety of metal oxides by varying the kind of consumable metal wire.

We measured electrical conductances in single crystalline boron nanobelts having α-tetragonal crystalline structure. The doping experiment of Mg was carried out by vapor diffusion method. We obtained ohmic contacts to both pure and Mg-doped nanobelt by metal electrodes of Ni∕Au bilayer. From the temperature dependence of electrical conductance, we found that the pure boron nanobelt is a semiconductor. The electrical conductivity of pure boron nanobelt was estimated to be on the order of 10−3(Ωcm)−1 at room temperature. After Mg vapor diffusion, the electrical conductance increased by a factor of 100 but a transition to metal was not observed.