bluuebunny/crossref_metadata_2025_split huggingface dataset:
Manganese Dioxide Nanoflowers Decorated Reduced Graphene Oxide As High-Performance Air Cathode for Zinc-Air Batteries
Authors: Teabnamang Pemika , Lao-atiman Woranunt , Kheawhom Soorathep 
Published: February 2020

Recently, zinc-air batteries have attracted increasing attention. These batteries exhibit high potential for many future energy applications because they offer high energy density at low cost. Besides, the batteries use zinc anode which is abundant, safe and non-toxic. However, their practical and extensive application is hindered by the sluggish oxygen reduction reaction (ORR). Thus, ORR electrocatalysts are employed to enhance the battery performance.
Noble metals such as platinum have played a dominating role as ORR electrocatalysts. Though they offer the advantages of high catalytic activity, electronic conductivity, and stability, their high costs are a serious concern. Therefore, much effort has been paid to metal oxides that are environmentally friendly and low cost. Among these, manganese dioxide (MnO2) is recognized as a potential alternative because of its abundance, low cost, low toxicity, and efficient electrocatalytic performance. The catalytic activity of MnO2 depended on the crystallographic structure and surface area. However, MnO2 has low intrinsic electrical conductivity. Traditionally, MnO2 coating on carbon supports is used to improve the electrocatalytic performance. Graphene, with its intriguing properties such as large surface area and high electrical conductivity, has recently received enormous attention as a possible candidate.
In this work, a cost-effective approach to synthesis MnO2 nanoflowers decorated reduced graphene oxide is proposed. The ORR electrochemical performance of the synthesized catalysts was examined. The optimal loading ratio of MnO2 is then determined. A zinc-air battery installed with the synthesized catalyst air cathode outperforms and exhibited a larger current density compared with the battery using a commercial Pt/C air cathode. Also, the results indicated that MnO2 nanoflowers decorated reduced graphene oxide offers a promising and cost-effective air cathode for zinc-air batteries as well as other metal-air batteries.

Figure 1
Investigation of Waste Heat Accumulation and Internal Resistance of AA Nimh Cells
Authors: Donnelly Daniel J , Patrissi Charles J. , Arruda Thomas M 
Published: February 2020

Nickel metal-hydride (NiMH) cells have been of considerable interest for the powering of unmanned underwater vehicles (UUV), primarily for the outstanding safety of their water-based electrolyte compared to the flammable organic solvents used in Li-ion cells. High energy and power densities, rechargeability, commercial availability, and low cost in the AA form further strengthen the NiMH case for integration into UUVs. While these factors are motivating, secondary cells generate heat during charge, which in excessive amounts is damaging to both the cell and nearby electronics. Our objective is to model the temperature (T) rise of NiMH cells caused by waste heat (Q) accumulation during battery charging according to the equation following this text.
Heat generation is a function of charge current (I), time (t), and the internal resistance of the cell (R). The galvanostatic intermittent titration technique (GITT)1 is being used to investigate resistance as a function of the current , temperature, and state of charge. Calorimetric measurements are ongoing to investigate specific heat of the cells (c). The change in cell temperature (dT) can then be modeled for various discharge currents and masses (m) of cells2. A Thermal model of NiMH cells configured at the battery level may be used to determine the safety limits for charge rate with respect to heat production during charging in UUVs.
1.Weppner, W. & Huggins, R. A. determination of the Kinetic Parameters of Mixed-Conducting Electrodes and Application to the System Li3Sb. Journal of the Electrochemical Society: Solid State Science and Technology,
124
(1997),1569-1578
2.Maleki, Hossein et al. (1999)Thermal Properties of Lithium-Ion Battery and Components. Journal of the Electrochemical Society, 146(3), 947-954

Figure 1
Synthesis of WS2xSe2(1-x) Nanowalls through a Rapid Thermal Annealing Process for Hydrogen Evolution Reaction and Sensor Application
Authors: Tang Shin-Yi , Medina Henry , Yen Wen-Chun , Chen Yu-Ze , Wang Yi-Chung , Su Teng-Yu , Chen Chia-Wei , Chueh Yu-Lun 
Published: February 2020

Owing to the exceptional physical properties and potential in sensor application, transition metal dichalcogenides (TMDCs) have attracted much attention in recent years. When the thickness of TMDCs is reduced to only monolayer or few atomic layers, a bandgap enlargement and transition from indirect to direct happen. Recently, researchers focus on the creation of various interesting nanostructures by different synthesis processes. Here, we present a novel chemical vapor reaction (CVR) method for the one-step synthesis of TMDC nanowalls from the reduction of WOx into WSe2 and WS2 through the rapid diffusion and segregation of chalcogenides. By the rapid heating and rapid cooling procedure, we can achieve the formation of nanowalls standing perpendicularly on top of both SiO2/Si and cabin-fiber paper substrates. Compared to the conventional solid-vapor phase CVD process, our approach is able to provide TMDCs with vertical nanostructures and enhanced surface area. Furthermore, the stoichiometry of WS2xSe2(1-x) walls can be adjusted by controlling the concentration ratio of sulfur and selenium. We provide Raman spectrum and X-ray Photoelectron Spectroscopies results supported by SEM and TEM observations to confirm the successful synthesis of the nanowalls with atomic thickness and varied compositions. This approach can also be applied to the synthesis of other TMDC materials, giving a step forward on the 2D materials research development.
The atomically thin TMDC materials are known for their great potential in sensing, optoelectronic, energy harvesting and Li-ion battery applications. Here, we demonstrate the catalytic property enhancement by utilizing WS2xSe2(1-x) on carbon-fiber paper as the cathode of hydrogen evolution reaction. In addition, due to the exposed edge sites of the TMDC nanowall structure, the application of gas sensing and photodetector was also investigated.
(Invited) Quasi-Two-Dimensional Thermoelectricity in Snse
Authors: Szkopek Thomas , Gervais Guillaume , Grueneis Alexander 
Published: February 2020

Stannous selenide is a layered semiconductor with a puckered honeycomb lattice that constitutes a polar analogue of black phosphorus, and of great interest as a thermoelectric material [1-3]. Hole doped SnSe supports a large Seebeck coefficient at high conductivity. We combine experimental techniques in the form of angle resolved photo-emission spectroscopy, optical reflection spectroscopy and magnetotransport measurements to map out a multiple-valley valence band structure and a quasi two-dimensional dispersion. The quasi two-dimensional dispersion realizes the low-dimensional Hicks-Dresselhaus thermoelectric, which contributes to the high Seebeck coefficient reported at high carrier density [1-2]. We further demonstrate that the hole accumulation layer in exfoliated SnSe transistors exhibits a field effect mobility of up to 250 cm2/Vs at T=1.3 K. Unintentional hole doping and persistent photoconductivity has been observed, suggesting material quality can be further improved. SnSe is thus found to be a high quality, quasi two-dimensional semiconductor.
References:
[1] L.-D. Zhao et al., Nature 508, 373 (2014).
[2] L.-D. Zhao et al., Science 351, 141 (2016).
[3] C. W. Li et al., Nature Phys. 11, 1063 (2015).
Simulation and Analysis of Phosphorene Nanoribbon Field Effect Transistors Using Non-Equilibrium Green's Function Formalism
Authors: Sarvari Hojjatollah , Liu Chaoyuan , Chen Z. , Ghayour Rahim 
Published: February 2020

Few-layer black phosphorus is a semiconductor material which was discovered in 2014. Phosphorus has both high mobility (1100-1140 cm2/V.s in armchair direction) and finite bandgap (~0.35 eV for bulk) compared to the other two-dimensional materials such as MoS2 and graphene. A single layer of black phosphorus is named as phosphorene. Multilayer (ML) phosphorene has an adjustable direct bandgap that can be controlled either by changing the width of the ribbon or the number of layers.
In this work, first we calculate the band structure of ML phosphorene nanoribbons (PNRs) using the tight-binding method. Then, we analyzed the performance characteristics of SL- and ML-PNR field effect transistors (PNRFETs) with abrupt doping between the Source/Drain (S/D) region and the channel region by employing the non-equilibrium Green’s function (NEGF) formalism in real space. This type of FET with abrupt doping near S/D and channel regions is known as conventional FET. We found that the bandgap of armchair PNRs with 16 atoms across the width of PNR for single-layer (SL) and bilayer (BL) structures is 1.899 and 1.224 eV, respectively. We showed that increasing the number of layers reduces both the bandgap of the material and the turn on voltage of device, however, it increases the ON-current of device. Simultaneously, the off-current also increases due to a higher probability of tunneling in low bandgap devices. In addition, increasing the number of atoms across the width of PNR leads to an increase in the Ids due to the decrease of the bandgap. Moreover, both on- and off-currents increase by decreasing the channel length in multilayer PNRFETs.
Next, we compared the performance characteristics of conventional and junction-less (JL) PNRFETs. Recently, JL-FET with high doping concentration in S/D and channel regions was proposed to replace the conventional FET. The JL silicon-on insulator FETs fabricated by Tyndall group show outstanding output characteristics with low Drain Induced Barrier Lowering (DIBL), ideal subthreshold swing, etc. There is no p-n junction between S/D and channel regions in a JL transistor. Instead, all regions are highly doped with the same amount of dopant to increase the conductivity of the channel material. In this case, the barrier in front of the electrons coming from source, is formed by applying suitable gate voltage. From experimental point of view, it should be much easier to dope all S/D and channel materials with the same doping concentration compared to the conventional FETs which needs abrupt doping. Thus, it should be a point of interest to have a performance comparison between conventional and JL phosphorene FETs. We investigated the performance of phosphorene FETs in terms of Id-Vgs, Id-Vds characteristics, energy levels, subthreshold swing, DIBL, and ION/IOFF.
(Invited) Circularly Polarized Luminescence from Planar Chiral Molecules Based on [2.2]Paracyclophane
Authors: Morisaki Yasuhiro 
Published: February 2020

Planar chirality is one of the unique features of mono- and polysubstituted [2.2]paracyclophane compounds. The potential applications of the [2.2]paracyclophane derivatives in materials chemistry necessitate the further development of practical optical resolution methods for planar chiral [2.2]paracyclophanes. Recently, we achieved the optical resolutions of 4,12-disubstituted [2.2]paracyclophane [1] and 4,7,12,15-tetrasubstituted [2.2]paracyclophane compounds [2]. By using the optically pure 4,12-disubstituted and 4,7,12,15-tetrasubstituted [2.2]paracyclophanes, we have prepared various planar chiral [2.2]paracyclophane building blocks [3] for π-system figuration. Herein, their optical resolution methods as well as subsequent transformations to the enantiopure conjugated compounds will be shown. As a representative example of π-system figuration, cyclic compounds based on planar chiral [2.2]paracyclophane will be introduced. These compounds comprise optically active higher-ordered structures such as propeller-shaped structure [2], double helical structure [3], and so on. They exhibit excellent chiroptical properties, i.e., large molar ellipticity in the ground state and intense circularly polarized luminescence (CPL) with large dissymmetry factors (g
lum) in the exited state. The results suggest that planar chiral [2.2]paracyclophane-based optically active higher-ordered structures (propeller-shaped and double helical structures in this study) are promising scaffolds for efficient CPL, and appropriate modifications can enhance the CPL properties.
References
[1] (a) Morisaki, Y.; Hifumi, R.; Lin, L.; Inoshita, K.; Chujo Y. Chem. Lett.
2012, 41, 990. (b) Morisaki, Y.; Hifumi, R.; Lin, L.; Inoshita, K.; Chujo Y. Polym. Chem.
2012, 3, 2727. (c) Morisaki, Y.; Inoshita, K.; Chujo Y. Chem.–Eur. J.
2014, 20, 8386.
[2] (a) Morisaki, Y.; Gon, M.; Sasamori, T.; Tokitoh, N.; Chujo Y. J. Am. Chem. Soc.
2014, 136, 3350. (b) Gon, M.; Morisaki, Y.; Chujo Y. J. Mater. Chem. C
2015, 3, 521.
[3] For example, Morisaki, Y.; Sawada, R.; Gon, M.; Chujo Y. Chem.–Asian J.
2016, 11(18), 2524.
(Invited) Effect of Substrate-Metal Interaction on the Oxygen Reduction Reactivity at Pt-Ni Nanoframe Deposited on N-Doped Carbon Supports
Authors: Yagi Ichizo , Ogura Kazuya , Tokuda Shoichi , Kato Masaru 
Published: February 2020

Carbon-supported platinum group metals (PGMs) are used as oxygen reduction reaction (ORR) electrocatalysts at cathodes in polymer electrolyte fuel cells (PEFCs). Since platinum reserves are limited, Pt-Ni alloy electrocatalysts for the ORR have been intensively studied. One of the highly active Pt-Ni alloy electrocatalysts is a carbon-supported Pt-Ni alloy nanoframe[1]. This electrocatalyst exhibits much higher catalytic ORR activity than commercial Pt/C catalysts and almost no activity loss after 10,000 potential cycles. In the practical point of view, further improvement of the durability and reactivity is required. The use of nitrogen-doped carbon as the catalyst support might improve the catalytic activity as well as durability because it is expected that nitrogen doping in carbon supports may modulate the electronic structure of the catalyst and/or give strong chemical bonding between the support and the catalyst[2].
Herein, we report electrocatlytic activity and durability of Pt-Ni alloy nanoframes on nitrogen-doped carbon supports to understand effects of the nitrogen content on the catalytic activity and durability. We used carbon black (Vulcan), N-doped carbon and graphitic carbon nitride (g-C3N4) were used as catalyst supports. Pt-Ni alloy nanoframes [1] and N-doped carbon supports were prepared according to the literature[3]. For the preparation of g-C3N4, melamine was heated at 600 °C under air for 2 hours. Linear sweep voltammetry of Pt-Ni alloy nanoframes on supports was carried out in 0.1 M HClO4 using a three electrode setup under oxygen.
TEM observations of Pt-Ni alloy nanoframes on supports suggested that the density of Pt-Ni nanoframes in a unit volume clearly increased with increase in the nitrogen content in the supports. Although the ORR activity of Pt-Ni nanoframes on N-doped carbon supports also depended on the nitrogen content, the optimum value of nitrogen content was 9%. The electronic interaction between N-species and Pt-Ni nanoframes will be the key to understand the activation mechanism.
This work was supported by NEDO.
[1] C. Chen et al., Science
343, 1339-1343 (2014); N. Becknell et al., J. Am. Chem. Soc.
137, 15817-15824 (2015).
[2] Y. Zhou et al., Energy Environ. Sci.
3, 1437-1446 (2010).
[3] Y. Zhang et al.,
Sci. Rep.
3, 2771. (2013).
(Invited) Nanoscale Electrocrystallization: A Site-Selective Electrochemical π-Figuration of Nanocrystals for Electronic Devices
Authors: Hasegawa Hiroyuki 
Published: February 2020

Efficient nanofabrication is still the problem awaiting solution in the nanotechnology field. Such nanofabrication should involve both economy and ecology-friendly process which produces high performance materials or devices. As seen in semiconductor industry, these fabrication technologies generally consume a large amount of energy under high-vacuum and/or high-temperature conditions. There is a strong need to switch to processes which are both eco-friendly and low-cost. Therefore pinpoint nanofabrication via eco-friendly process seems to be most promising.
From the viewpoint, we have developed nanoscale electrocrystallization for nanodevice fabrication.1 This method allows everyone to grow nanocrystals, which consist of π-conjugated molecules, site-selectively within a gap between two electrodes fabricated on a substrate. In addition, this method also allows for the gap between the two electrodes to be bridged by the formed nanocrystals.

· Magnetic field effect devices

Magnetic field effect devices were designed by using dicyanoiron(III)phthalocyanine ([Fe(Pc)(CN)2]-) tetraphenylphosphonium (TPP+) salt as a starting material of nanoscale electrocrystallization. The electrolysis gave nanocrystals that exhibited a strong correlation between the localized spin and conduction electrons, TPP·[Fe(Pc)(CN)2]2 was obtained. A negative giant magnetoresistance was first observed as an organic nanocrystal.2 Moreover, an angular dependence of the negative giant magnetoresistance that originates from the highly oriented growth of the nanocrystals was also observed.

· Electronic field effect devices

Electronic field effect devices such as field-effect transistors (FETs) were designed by using materials for organic conductors. A bottom-gate type FET structure was simply obtained when a silicon substrate with oxide layer was used for an electrode substrate. The two electrochemical electrodes were reused as source and drain electrodes. FET characteristics showed current enhancement in some kinds of samples.3 The device fabrication was also demonstrated via an eco-friendly and non-vacuum process using a material printer.4

Further details of fabrication, materials, and physical properties will be reported.

References

1. H. Hasegawa, T. Kubota, S. Mashiko, Thin Solid Films, 2003, 438–439, 352–355; H. Hasegawa, T. Kubota, S. Mashiko, Electrochim. Acta, 2005, 50, 3029–3032; H. Hasegawa, R. Ueda, T. Kubota, S. Mashiko, Thin Solid Films, 2006, 499, 289–292.
2. H. Hasegawa, M. Matsuda, H. Tajima, J. Mater. Chem. C, 2013, 1, 6416–6421.
3. H. Hasegawa, J. Mater. Chem. C, 2013, 1, 7890–7895; H. Hasegawa, New J. Chem., 2013, 37, 2271–2274; H. Hasegawa, Sci. Adv. Mater., 2014, 6, 1548-1552.
4. H. Hasegawa, Appl. Mater. Today, 2017, 9, 487–492.

Figure 1
Anomalous Current/Voltage Behaviors of Polyoxometalate/Porphyrin Derivative Complexes
Authors: Ogawa Takuji , Nurhayati Nunik , Miyamoto Fumiya , Yamazaki Yoshito , Aoyama Tomoya , Yamashita Ken-ichi , Tani Yosuke 
Published: February 2020

Polyoxometalate (POM) derivatives have been reported to show various specific electronic properties. For example, (NH4)6V10O28 and H7SiW9V3O40 show negative differential resistance (NDR) when measured by scanning tunneling spectroscopic (STS) technique in air.1,2 We have reported that a composite of H3PMo12O40 with single-walled carbon nanotubes (SWNT) showed complex phenomena depending on the size of the POM nanoparticles. When the size of the POM was smaller than ~6 nm with a semiconducting SWNT, the composite showed rectification with positive bias suppression. By contrast, if the size of the POM was larger, the suppression was observed at negative bias. However, when the SWNT is metallic, the suppression occurred at the opposite bias.3

There are several POM/porphyrin derivatives or analogues reported, saddle-distorted Mo(V)-dodecaphenylporphyrin with Keggin-type H2SiW12O40,4 cyclo[8]pyrrole with H4SiW12O40,5 tetraphenylporphyrin (TPP) with SW10V2O40.6 The electronic properties of these complexes are interesting to measure in macro-scale and in single molecule-scale, because of the versatile electronic behaviors are expected from multi redox characters of POM cores tuned by the surrounding porphyrin derivatives.
The single crystal structure of [H4TPP][SV2W10O40] was successfully determined, in which one POM anion is surrounded by four H4TPP cations. Although this complex is dissociated in solution, the casted sample retains crystalline structures partially as observed by the powder X-ray diffraction study. Devices were made by casting the solution of the complex on Au electrodes with 5 μm gap. The current-voltage curve at ambient conditions showed broad negative differential resistance (NDR) with large hysteresis. The impedance measurements between 10-1 to 106 Hz at 0.0 to 3.0 V DC bias indicated that in low frequency range (<10 Hz) the impedance is lower at high DC bias voltage. However, in high frequency range (> 10Hz) the impedance is almost independent on voltage. The impedance results indicate that non-linear NDR behavior observed in DC measurement is because of a slow process of the carrier movement, probably by ionic conductance.
References
(1) Ogawa, T.; Handayani, M. In Molecular Architectonics; Ogawa, T., Ed.; Springer Nature: Switzerland, 2017, p 419.
(2) Watson, B. A.; Barteau, M. A.; Haggerty, L.; Lenhoff, A. M.; Weber, R. S. Langmuir
1992, 8, 1145.
(3) Hong, L.; Tanaka, H.; Ogawa, T. J. Mat. Chem., C
2013, 1, 1137.
(4) Yokoyama, A.; Kojima, T.; Ohkubo, K.; Fukuzumi, S. Chem. Commun.
2007, 3997.
(5) Okujima, T.; Matsumoto, H.; Mori, S.; Nakae, T.; Takase, M.; Uno, H. Tetrahedron Lett.
2016, 57, 3160.
(6) Shi, Z. H.; Zhou, Y. S.; Zhang, L. J.; Mu, C. C.; Ren, H. Z.; ul Hassan, D.; Yang, D.; Asif, H. M. RSC Adv.
2014, 4, 50277.

Figure 1
(Invited) Size Controlled Silicon Quantum Dots: A Model System for Understanding the Physics of Indirect Quantum Dots
Authors: Gutsch Sebastian , López-Vidrier Julian , Hiller Daniel , Zacharias Margit 
Published: February 2020

The fabrication of SiOx/SiO2 superlattices combined with thermal annealing enables the size and density control of Si quantum dots [1]. The layered-arranged Si nanocrystals represent a model system to systematically study the photonic and electronic properties of (indirect bandgap) quantum dots prepared in a CMOS compatible way. Hence, the size controlled nanocrystals are used to understand the interplay of absorption and recombination, the carrier kinetics and the electronic transport properties for matrix embedded Si quantum dots. Starting with the temperature dependence of the size depending band gap [2] we will discuss the interplay of radiative and non-radiative recombination for high quantum yield [3-5]. Doping of quantum dots and the respective experimental techniques for its quantification is at the very limit of the nowadays experimental possibilities. We will present systematic doping experiments with P and B which will be analyzed for doping efficiency, in-cooperation into the Si QDs and self-purification effects [6, 7].
[1] M. Zacharias et al. Appl. Phys. Lett. 80 (2002) 661.
[2] A. M. Hartel et al. Phys. Rev. B 85, 165306 (2012).
[3] A.M. Hartel et al. Rev. B 87, 035428 (2013).
[4] J. Valenta et al J. Appl. Phys. 122 144303 (2017)
[5] M. Greben et al. Beilstein J. Nanotechnol. 8, 2315 (2017).
[6] D. Hiller et al. Scientific Reports 7, 863 (2017).
[7] D. Hiller et al. Scientific Reports 7, 8337 (2017).