bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of Octahedral-Shaped Pt-Ni Nanoparticles for Electrochemical Oxygen Reduction
Authors: Kühl Stefanie , Gocyla Martin , Heyen Henner , Beermann Vera , Heggen Marc , Dunin-Borkowski Rafal E. , Strasser Peter
Published: February 2020

In case of polymer electrolyte fuel cells (PEFCs) Platinum is still the most used catalyst for the oxygen reduction reaction (ORR) at the cathode – where PtNi alloys are the state of the art [1, 2]. Following a study by Stamenkovic et al. in 2007 [3] several groups dealt with octahedral shaped nanoparticles (NPs) during the last decade to enhance both specific and mass activity [4]. Well-defined octahedral shaped NPs can be obtained e.g. by solvothermal synthesis using DMF as solvent and reduction agent [5]. Unfortunately, such PtNi octahedra show a major disadvantage in lacking of morphological stability during electrochemical cycling [6]. In the present work, we combine the DMF-based synthesis with a thermal post-treatment as annealing step toward an improved PtNi alloy structure with higher stability. The study is primarily based on the morphological investigations by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray analysis (EDX), both ex situ as well as in situ mode, to gain insights into the structure-activity-stability relationship.

In detail, based on a previous work [7], we exposed octahedral PtNi particles (supported on carbon) to a post-treatment in hydrogen using a tubular furnace. First off all, an increased annealing temperature results in a better defined PtNi alloy – proven by XRD. Whereas after 300°C mainly octahedral NPs were present, a complete loss of shape was observed after annealing at 500°C, where nearly spherical particles resulted. Additionally, the morphological changes during heating were also observed in situ using a TEM heating nano-chip (i.e. heating in vacuum). Both annealing in hydrogen as well as in vacuum show indications for Pt diffusion to (111) facets before the octahedral shape collapsed. Indeed, a rather mild treatment in hydrogen can improve the alloy structure and, thus, lead to higher activity in ORR, whereas a complete PtNi alloying at higher temperatures is diminishing the ORR activity due to the loss of octahedral shape and, accordingly, (111) facets.

References

[1] Y. Bing et al., Chem. Soc. Rev
39 (2010) 2184-2202.

[2] H. A. Gasteiger, N. M. Marković, Science
324 (2009) 3791.

[3] V. R. Stamenkovic et al., Science
315 (2007) 493.

[4] P. Strasser, Science
349, 379-380 (2015).

[5] M. K. Carpenter et al., J. Am. Chem. Soc.
134 (2012) 8535-8542.

[6] L. Gan et al., Science
346 (6216) (2014) 1502-1506.

[7] M. Ahmadi et al., ACS Nano 7 (2013) 9195-9204.
Combined Modeling and Experimental Analysis of Direct Methanol Microscale Fuel Cells
Authors: Hollinger Adam S , Doleiden Daniel G , Argun Nazlihan O , Miller Kelly L
Published: February 2020

With the advancement of portable technology, suitable power sources must be developed. Alternatives to standard battery technology, such as fuel cells, have shown promise; however such fuel cells are in their infancy with regards to industrial and consumer adoption [1-3]. In order for fuel cells to become a feasible alternative to traditional dry-cell alkaline and lithium-ion batteries, their performance must be optimized for their intended application via manipulation of parameters such as fuel molarity, flow rate, temperature, and electrode geometry. Here, we present a mathematical model of a microscale direct methanol fuel cell (DMFC), validated with experimental data. In the past, an iterative fabrication approach was undertaken to optimize DMFC performance, involving the fabrication and testing of many individual components to assess the effects of individual parameters. This model provides a means to automate the design process and remove the fabrication requirement.

Prior parametric studies by Thorson et al. [4] show that shorter and wider electrodes yield higher current densities, however a recent review by Goulet et al. [5] highlights the need for a combined modeling and experimental approach to evaluating electrode design in a microscale fuel cell. Here we present a mathematical model to analyze the fuel flow pattern and performance of a direct methanol microscale fuel cell as a function of electrode geometry. Localized current densities are calculated over the electrode surface to elucidate the differences between electrode geometries. In the present work, the dimensions of the fuel channel are constant (0.5 cm (L) x 1.0 cm (W) x 0.125 cm (H)), while the length and width of the catalyst deposition region are varied. The model is validated with experimental data taken as a function of electrode geometry, fuel concentration, fuel temperature, and fuel flow rate. The performance of our experimental fuel cell is consistent with our modeling studies, achieving a maximum power density greater than 25 mW/cm2 at room temperature with 1 M methanol. The model presented here, in conjunction with the supporting experimental data, expands prior parametric studies [4] to predict optimal electrode design with regard to methanol concentration, temperature, and flow rate.

[1] C.K. Dyer, Fuel Cells Bulletin, 2002 (2002) 8-9.

[2] E. Kjeang, N. Djilali, D. Sinton, Journal of Power Sources, 186 (2009) 353-369.

[3] A.S. Hollinger, P.J.A. Kenis, Journal of Power Sources, 240 (2013) 486-493.

[4] M.R. Thorson, F.R. Brushett, C.J. Timberg, P.J.A. Kenis, Journal of Power Sources, 218 (2012) 28-33.

[5] M.A. Goulet, E. Kjeang, Journal of Power Sources, 260 (2014) 186-196.

Figure 1
Combined Neutron and x-Ray Imaging Techniques for Enhanced Water Management Diagnostics
Authors: LaManna Jacob M , Hussey Daniel S , Baltic Elias , Jacobson David L
Published: February 2020

Neutrons and X-rays provide rich complementary information for investigations of three-phase flows. A hydrogenous liquid phase is well resolved from the solid and gas phases using neutrons due to the large neutron attenuation of hydrogen while the solid phase can be separated from the liquid and gas phases using X-rays. By combining these two imaging techniques it is possible to achieve a full understanding of the three-phase flow with high sensitivity to all phases. A critical application for this combined technique is in proton exchange membrane fuel cells where understanding of the liquid water buildup in porous materials is paramount to achieving high performance and reliability. To achieve this goal, NIST has brought online a unique system for simultaneous neutron and X-ray imaging. A 90 keV microfocus X-ray source is oriented 90° to the neutron beam and the sample is positioned at the intersection of the two beams allowing for the simultaneous imaging with both modalities. The system will facilitate both serial radiography using the X-rays to enhance the current state-of-the-art neutron radiography and simultaneous tomography for 3D resolved water content and solid material structure. This presentation will describe the current work to develop this new capability for the fuel cell research community, fuel cell hardware development for simultaneous tomography, and initial results obtained from this system.
(Invited) Self-Humidifying Membrane Electrode Assembly Prepared by Adding Moisture Preserve Materials in Anode Catalyst Layer
Authors: LIao Shijun , Hou Sanying
Published: February 2020

By adding moisture preserve materials in the anode catalyst layer, we prepared a series of low humidity membrane electrode assembly (MEAs), and all the MEAs exhibited excellent performances at low humidity for both anode fuel and cathode air. The effects of the structure, used amount of the materials on the low humidity performances of the MEAs were investigated, and we also explored the mechanism for the excellent low-humidity performances of the MEAs with moisture preserve material added at anode catalyst layer.
(Invited) Tomographic Analysis of Fuel Cell Catalyst Layers - Methods, Challenges and Validity
Authors: Thiele Simon , Vierrath Severin , Zielke Lukas
Published: February 2020

The catalyst layer (CLs) are the central part of Polymer Electrolyte Fuel Cells. Consisting of catalyst particles, ionomer, carbon black plus numerous gases and liquid water during operation, the CL contains not less than five different phases with a plethora of mutual physical interactions. Further, all these phases have characteristic length scales in the nanometer range. Due to its nanoscale, multi-phase nature the CL bears complex physical phenomena that are very challenging to describe and understand.

The precise morphology of all phases within a CL plays a key role for reactant transport and thus  performance: Platinum catalyst particles with poor connection to ion conducting, electron conducting or gas transporting phases cannot contribute to the fuel cell reaction. Also, the precise shape of the pathways of the reaction species determines their effective transport properties. Wetting or non-wetting pore wall areas influence water precipitation and therefore the generation of liquid water networks. Such networks both improve ionic transport and adulterate gas transport. 

Facing the tremendous influence morphology has on PEMFC performance, cost and durability, tools to image morphology are an obvious necessity. While there is a variety of imaging methods that allow three-dimensional reconstructions, only few are able to resolve the nanostructure of CLs: x-ray tomography (Xt), focused ion beam / scanning electron microscopy tomography (FIB-SEMt) and transmission electron microscopy tomography (TEMt) [1].

Both Xt and FIB-SEMt have been proven to enable differentiating porous and solid phase within PEMFC CLs [2,3]. TEMt allows imaging with resolutions below 1 nm and can be directly used to image Platinum particles [4]. To image all important phases multiple tomographic techniques must be used. In this talk we give an overview on the latest tomographic analysis techniques for PEMFC CL reconstruction with a particular emphasis on FIB-SEMt, multi-scale imaging approaches and validity of the existing reconstruction methods.

References

[1]  G. Möbus, B.J. Inkson, Materials Today 10 (2007) 18–25.

[2]  C. Ziegler, S. Thiele, R. Zengerle, J. Power Sources 196 (2011) 2094–2097.

[3]  W.K. Epting, J. Gelb, S. Litster, Advanced Functional Materials (2012).

[4]  H. Uchida, J.M. Song, S. Suzuki, E. Nakazawa, N. Baba, M. Watanabe, The Journal of Physical Chemistry B 110 (2006) 13319–13321.

[5]          S. Thiele, T. Fürstenhaupt, D. Banham, T. Hutzenlaub, V. Birss, C. Ziegler, R. Zengerle, J. Power Sources 228 (2013) 185–192.
Development of Sulfonated Poly(Arylene Ether Sulfone) Multi-Block Membranes for Low RH PEMFC Operation
Authors: Bae Byungchan , Lee Sojeong , Lee Hyejin , Shin Dongwon
Published: February 2020

Perfluorosulfonic acid (PFSA) polymers are the most promising state-of-the-art materials as proton exchange membranes (PEM) for fuel cells, however, there are some drawbacks such as high production cost and hydrothermal stability. Aromatic membranes based on hydrocarbon polymers have been studied as alternatives. Among them, multi-block copolymers seem to be promising to compete with PFSA resulting high proton conductivity even under low RH conditions.[1, 2]

In this report, novel sulfonated poly(arylene ether sulfone)s multi-block copolymer membranes containing highly sulfonated hydrophilic blocks were synthesized.[3] Different local concentration of sulfonic acid in their hydrophilic blocks affected chemical and physical properties of the SPAES. To investigate the effects of chemical composition on their membrane properties, different hydrophilic oligomers sharing same hydrophobic blocks gave us exact comparison of effect of hydrophilic blocks. The higher concentration of sulfonic acid groups resulted in higher proton conductivity under certain relative humidity conditions than that of the state-of-the-art perfluorinated sulfonic acid membrane and showed that the well-developed phase separation of SPAES. Moreover, physical properties of theses SPAES including water behavior, humidity dependence of proton conductivity were investigated along with morphology characterizations by transmission electron microscopy (TEM) for PEMFC application. Two types of oligomers, F-terminated and OH-terminated telechelic oligomers, were synthesized by controlling the feed ratio of dihydroxyl- and difluoro-monomers. Their number of repeating unit (X and Y) was analyzed by GPC and 1H NMR. Copolymerization with F-terminated and OH-terminated telechelic oligomers via nucleophilic aromatic substitution, gave high-molecular-weight multi-block PESs. Each block length was controlled to have different values with X5Y10, X10Y10, X20Y10 and X20Y20.

The SPAES X10Y10 membrane showed highest proton conductivity than that of our previous random and block copolymers at wide range of humidity. The best balanced membrane was SPAES X10Y5 membrane with high proton conductivity and lower water uptake. Consequently, the SPAES X10Y5 membrane showed high cell performance under various conditions (510 mA/cm2, 290 mA/cm2 @ 0.6V under 80% and 50 % RH conditions at 80℃, respectively). Systematic approaches for developing alternative block SPES membrane for low RH condition will be discussed.

 References

[1] H.-S. Lee, A. Roy, O. Lane, J.E. McGrath, Polymer, 49 (2008) 5387-5396.

[2] B. Bae, T. Yoda, K. Miyatake, H. Uchida, M. Watanabe, Angew. Chem. Int. Ed., 49 (2010) 317-320.

[3] S. Lee, J. Ann, H. Lee, J.-H. Kim, C.-S. Kim, T.-H. Yang, B. Bae, J. Mater. Chem. A, 3 (2015) 1833-1836.
Mesostructured Pt-Based Bimetallic Nanospheres As Ultrastable Self-Supported Oxygen Reduction Electrocatalysts
Authors: Kim Ho Young , Cho Seonghun , Sa Young Jin , PARK Gu-Gon , Yim Sung-Dae , Joo Sang Hoon
Published: February 2020

Enhancing the activity and stability of cathode catalysts in proton exchange membrane fuel cells (PEMFCs) is of great importance for their widespread commercialization. While nanostructured Pt-based nanoparticles supported on carbon have been the most active cathode catalysts, their long-term durability and their implementation n single cells represent challenges. In this work, we report the self-supported, mesostructured Pt-based bimetallic (Meso-PtM; M=Ni, Fe, Co, Cu) nanospheres containing intermetallic phase, which can combine the beneficial effects from transition metal (M), intermetallic phase, interconnected framework, and porous structure. All Meso-PtM nanospheres showed enhanced ORR activity, compared to Pt black and Pt/C catalysts. Particularly, Meso-PtNi with intermetallic phase exhibited ultrahigh stability, showing enhanced ORR activity even after 50,000 potential cycling, whereas Pt/C underwent a dramatic degradation. Importantly, the superior performance of Meso-PtNi with intermetallic phase was also demonstrated in a PEMFC single cell. The initial mass activity of Meso-PtNi far exceeded that of Pt/C and the US DOE target value, and represents one of the best activities among Pt nanocatalyst-based PEMFCs.
Tensiometric, IR- and 19f-NMR Analysis of Nafion Solutions for PEMFCs and PEMELs
Authors: Schulz Anne , Luehmann Nicole , Stähler Markus , Lüke Wiebke , Lehnert Werner
Published: February 2020

In the construction of polymer electrolyte membrane fuel cells (PEMFCs) and polymer electrolyte membrane electrolyzers (PEMELs), Nafion® (sulfonated tetrafluorethylene) is used as a membrane material and as proton conductor in the porous catalysts layers of membrane electrode assemblies (MEAs). Efficiency can be increased and costs reduced by optimizing and controlling the porous catalyst layer in MEAs. It is important to understand the polymer properties, which can be achieved by using different solutions and varying concentrations of one mixture for manufacturing the dispersion. Furthermore, the findings are of particular importance for the coating process. The efficiency of the PEMFCs and PEMELs depends on the number of active centers in the porous catalyst layer. The formation of the triple phase boundary is of great importance. This can be ensured by controlling the structural properties of the dispersion. Thereby, the static and dynamic surface tensions are analyzed. Surface tension and interfacial tension are necessary for understanding the coating process and adhesion to a transfer layer. The complex system was simplified and research on the surface properties performed with an aqueous Nafion® solution in an alcohol concentration series. Hence, the only aspect that changed was the alcohol, while the dynamic surface tension was measured with a bubble pressuretensiometer (BP100, KRÜSS GmbH). The static surface tension and interfacial surface tension were carried out with a force tensiometer (K100, KRÜSS GmbH) after Wilhelmy plate respectively the duNouy Ring method. In addition the solution was analyzed by means of IR- and 19F-NMR- spectroscopy.

It will be demonstrated in this contribution that the static and dynamic surface tensions differ significantly at lower alcohol concentrations in solution series with and without Nafion®. While at higher alcohol concentrations the static surface tension between both series is similar, the dynamic surface tension shows a different trend with varied bubble age. This can be explained by the interaction between alcohol and Nafion®. In accordance with the previous interface outcomes, the 19F-NMR- and IR- spectra are analyzed. According to the first results, it is also apparent that there are interactions between Nafion® and alcohol. The application of these methods provides an understanding of the interaction between the molecules in the catalyst dispersions. This information is essential for understanding the interactions between the components of catalyst dispersion during electrode manufacturing.
Conductive Si-B-C Ceramics As Durable Catalyst Supports
Authors: Smith Graham , Jackson Colleen , Kramer Denis , Levecque Pieter
Published: February 2020

Long recognised as key to the reduction of precious metal loading in PEMFC is the use of small catalyst nanoparticles (c.a. 3nm) stabilised by supporting them on high surface area carbon. However, PEMFCs using this technology achieve only 50% of the lifetime required by the US DOE’s target [1] with the oxidation of carbon supports a major lifetime limitation [2]. We have previously reported that catalysts on composite boron carbide, graphite supports show an increased durability to potential cycling below 1V and remarkably high ORR specific activities, 85% higher than commercial Pt/C [3]. Despite their excellent performance at low potentials, the presence of carbon in these catalysts still limits their durability during cycling to high potentials.

We will present our latest work on catalyst supports in the Si-B-C system with the focus on eliminating carbon. Hybrid DFT/HF calculations were used to highlight boron doped boron carbide and boron doped silicon carbide as ceramics with intrinsic conductivity [Figure 1a]. To synthesise these doped ceramics with high purity, low temperature synthetic routes based on the carbo-thermal reduction of polymers were developed. These routes gave carbides with low levels of carbon impurities and provided control over the morphology of the support. This allowed the creation of high surface area supports on which platinum nanoparticles have been deposited [Figure 1b]. Electrochemical characterisation (ORR activity, accelerated degradation, etc) of the produced catalysts will also be presented.

[1] Fuel Cell Technical Team Roadmap, 2013, US DOE

[2] E. Antolini, and E. R. Gonzalez. Solid State Ionics, 2009, 180.9, 746

[3] C. Jackson et al. 18th Topical ISE Meeting 2016. [Manuscript in preparation]

Figure 1
Development of Novel Electrolyte Additives for Designed Surface Modification
Authors: Lucht Brett L
Published: February 2020

An investigation of the effect of electrolyte on performance of in lithium ion batteries will be presented The electrochemical performance of common electrolyte formulations will be discussed along with detailed ex-situ surface analysis of the cycled electrodes. The ex-situ analysis allows the development of an understanding of the role of the electrolyte and common additives in the structure of interfacial electrode films on both the anode (solid electrolyte interphase, SEI) and on the cathode. Correlation of the structure of the surface films with the performance limiting reactions in lithium ion batteries affords insight into the mechanism of interfacial film formation and function. The mechanistic insight is used to systematically develop novel additives designed for specific electrode surface modification to afford optimized electrochemical performance. The electrochemical performance and ex-situ surface analysis of electrodes cycled with novel Additives for Designed Surface Modification (ADSM) will be presented.
Evaluation of La3Ta0.5Ga5.3Al0.2O14 and Sr3NbGa3Si2O14 Piezoelectric Crystals on Scintillation Properties
Authors: Yanagida Takayuki , Fujimoto Yutaka , Futami Yoshisuke , Okada Go , Kawaguchi Noriaki
Published: February 2020

Piezoelectric materials are one of the functional materials which convert the energy of stress to electric energy and widely used for sensors. Up to now, many materials were investigated for this application. Among them, LTGA (La3Ta0.5Ga5.3Al0.2O14) and SNGS (Sr3NbGa3Si2O14) single crystals have langasite type structures and they are famous for their piezoelectric characteristics even in high temperature more than 1,000 degrees [1]. Recently, we studied optical properties such as photoluminescence (PL) and radioluminescence (RL, scintillation in other words) of other langasite crystals including Ca3NbGa3Si2O14 (CNGS), La3Ga5SiO14 (LGS), La3Nb0.5Ga5.3Al0.2O14 (LNGA), and LTGA [2, 3]. In previous studies, we found that these langasite crystals exhibited quite interesting feature of very fast sub-ns decay time in visible wavelength and detectable scintillation signal [2, 3]. Therefore it was proved that langasite crystals can be potentially applicable for scintillator applications.

In this work, optical and scintillation properties of Sr3NbGa3Si2O14 (SNGS) single crystal were evaluated for the first time, and compared with those properties of La3Ta0.5Ga5.3Al0.2O14 (LTGA) which was previously reported. Although these materials are a type of piezoelectric materials, significant optical and scintillation properties were observed. SNGS showed ~80% optical transmittance in wavelength longer than 250 nm. Under 250 nm excitation, strong photoluminescence appeared at 400 nm with a primary decay time of 1.4 ns. In X-ray induced radioluminescence spectrum, intense emission peak at 400 nm was observed and primary scintillation decay time resulted ~ 1.37 ms. Finally, the absolute scintillation light yield of SNGS turned out to be 850 photons/MeV under 137Cs 662 keV gamma-ray excitation and it was largely brighter than LTGA.

[1] I.H. Jung, K.H.Auh, Mater. Lett., 51 (2001) 129.

[2] Y. Futami, T. Yanagida, Y. Fujimoto, V. Jary, J. Pejchal, Y. Yokota, M. Kikuchi, M. Nikl, A. Yoshikawa: Opt. Mater., 34 (2012) 1513.

[3] Y. Futami, Y.Yokota, M. Sato, T. Yanagida, N. Kawaguchi, Y. Fujimoto, K. Tota, K. Onodera, A.Yoshikawa, J. Cryst. Growth, 352 (2012) 129.
(Invited) Efficient Phosphor Materials: The Fundamental Physics
Authors: Happek Uwe
Published: February 2020

The advent of solid state lighting has resulted in great achievements in the development and refinement of phosphor materials during the last two decades. While novel phosphors are developed at a rapid pace even today (often driven by patent constraints or production cost demands), we have come to a point where we can, with the advantage of hindsight, have a close look at the requirements for an efficient phosphor.

An overview of the underlying solid state physics will be given, and this physics will be applied to explain, in a number of examples, the advantages of efficient phosphors and the shortcomings of inferior ones.
(Invited) X-Ray-Induced Changes in Spectroscopic Properties of LuPO4:Eu and LuPO4:Sm Ceramic Phosphors
Authors: Zych Eugeniusz , Zeler Justyna , Meijerink Andries
Published: February 2020

Rare earth (RE)-activated orthophosphates were thoroughly investigated for their luminescent properties years ago. However, it is only recently as the singly-activated LuPO4:Eu was reported to show efficient thermoluminescence when exposed to ionizing radiation. In this presentation we shall compare and discuss X-ray induced profound changes in spectroscopic properties of the two high-temperature sintered ceramics: LuPO4:Eu and LuPO4:Sm.

After exposure to ionizing radiation, both Eu- and Sm-activated LuPO4 ceramics show an efficient orange-red thermoluminescence (TL) with a maximum signal around 200°C and covering ~130-280 °C range of temperatures (see Fig. 1). The mechanism of the energy storage involves the Eu3+→Eu2+ or Sm3+→Sm2+ transformation due to trapping an electron from the conduction band. Spectroscopic effects related to the generation of Eu2+ or Sm2+will be presented and compared for both compositions.

Fig. 1. Temerature- and wavelength-resolved thermoluminescence of LuPO4:Eu and LuPO4:Sm sintered ceramics.

Figure 1
New Red-Emitting Boronitrides: Ca3(BN2)2:Eu2+ and Sr3(BN2)2:Eu2+
Authors: Dierkes Tobias , Juestel Thomas
Published: February 2020

The first boronitrides of this relatively new class of materials have been reported as early as the 1960ties by Gobeau and Anselment [1]. In the meantime, due to their versatile chemistry a wide variety of very different materials has been reported, including boronitrides of alkali metals, alkaline earth metals, and lanthanides [2-4]. These materials have been investigated thoroughly with respect to their magnetic and electronic properties. For instance, La2Ni2(BN2)2N exhibits supra conductivity.

The potential of boronitrides for luminescent applications, i.e phosphors in phosphor-converted light emitting diodes (pc-LEDs) on the other hand has almost not been researched at all, up to now [5-8]. The title compounds Ca3(BN2)2 and Sr3(BN2) doped by divalent europium exhibit luminescence in the red spectral range, when excited by near-uv radiation. In the present study we provide the first comprehensive investigation of the luminescence of the aforementioned materials. This includes excitation, emission and reflection spectra as well as measurements of the decay constants.

References

[1] J. Gobeau and W. Anselment, Z. Anorg. Allg. Chem. 310 (1961) 248-260

[2] C. Koz, S. Acar, Y. Prots, P. Höhn and M. Somer, Z. Anorg. Allg. Chem. 640 (2) (2014) 279-285

[3] S. A. Kulinich, L. G. Sevast’yanova, G. N. Bondarenko and K. P. Burdina, Russ. J. Gen. Chem. 69 (4) (1999) 530-533

[4] B. Blaschkowski, H. Jing and H.-J. Meyer, Angew. Chem. Int. Ed. 41 (2002) 3322-3336

[5] Y. Q. Li, C. M. Fang, Y. Fang, A. C. A. Delsing, G. de With and H. T. Hintzen, J. Solid State Chem. 182 (2009) 3299-3304

[6] J. Schölch, T. Dierkes, D. Enseling, M. Ströbele, T. Jüstel and H.-J. Meyer, Z. Anorg. Allg. Chem. 641 (5) (2015) 803-808

[7] M. Ströbele, K. Dolabdjian, D. Enseling, D. Dutczak, B. Mihailova, T. Jüstel and H.-J. Meyer, Eur. J. Inorg. Chem. 10 (2015) 1716-1725

[8] Q. Long, C. Wang, J. Ding, Y. Li, Q. Wua and Y. Wang, Dalton Trans. 44 (32) (2015) 14507-14513

Figure 1
(Invited) Phosphors-By-Design: Developing the Next Generation of Luminescent Materials for Solid State Lighting
Authors: Brgoch Jakoah
Published: February 2020

The development of rare-earth substituted phosphors generally relies on the chemical substitution of known compounds or searching phase-space to identify new materials. Yet, this approach often leads to the formation of known structure-types and incremental improvements of current luminescent materials. Transitioning beyond methods of classical materials discovery by turning to high-throughput computation and combinatorial algorithms has shown great promise in the development of new phosphors. A third method uses the combination of DFT-based computation and experiment to predict optical response. For example, calculating the Debye temperature and electronic band-gap of potential host compounds allows the selection of compounds from crystal structure databases ensuring only the best materials are experimentally explored. Our research has followed this approach to target a number of new luminescent materials ranging from borates to nitrides and showed an acceleration in materials discovery. Moreover, the complementary use of computation and synthesis provides an avenue for the fundamental understanding of the composition, structure, and property relationship necessary to advance the development of optical materials.
Rapid Screening of Novel LED Phosphors Using Melt Quenching Method
Authors: Toda Kenji , Kim Sun-Woog , Uematsu Kazuyoshi , Sato Mineo
Published: February 2020

In order to develop novel LED phosphor materials, we applied novel synthesis technique, “Melt quenching synthesis” rather than the conventional solid state reaction technique. This synthesis technique is a general and powerful tool for rapid screening and improvements of new phosphor materials. As shown on fifure, a combinatorial melt synthesis reactor is designed to heat 24 small-size samples up to very high temperature like above 2200 K melt in clean conditions. Strong light emitted from a 6 kW xenon lamp is collected by an ellipsoidal mirror (collector) and directed to the sample. In the melt synthesis, the mixture of raw materials is melted in a short period of time (from 1 to 60 s) by a strong light radiation in arc imaging furnace. A spherical molten sample with multiple cations were mixed homogeneously at around 2200 K and directly solidified on a Cu hearth after closing the shutter. The cooling rate was estimated to be more than 100 K/s.

For example, Y3Al5O12:Ce3+ (YAG:Ce) is a most well-known yellow phosphor for white LEDs. Conventional synthesis technique of LED phosphor is a solid state reaction using the mixture of oxide or carbonate starting materials. The YAG: Ce phosphor synthesized by the high temperature solid state reaction shows agglomerate and irregular shape particles with inhomogeneous distribution of Ce3+ ions because of poor reactivity of high melting point raw materials, Al2O3 (melting point 2327 K) and Y2O3 (2706 K). The synthesis and morphology control of such complex oxide phosphor is not easy by the conventional solid-state reaction with several grinding and firing steps. A spherical phosphor ball samples were directly solidified on a Cu hearth and show bright emission by excitation of visible light. The melt process produces a well-grown YAG:Ce phosphor with useful lens-like morphology. YAG:Ce phosphors synthesized by the "melt synthesis technique” show superior luminescence property (10 – 20 % higher emission intensity) because of high crystallinity.

Well-crystallized and grown LED phosphors were synthesized by the new synthesis technique, “Melt quenching synthesis”. Polycrystal, glass and single-crystal LED phosphors were obtained in a quite short reaction time for melt quenchin reaction, which is a new useful and powerful method for synthesis of LED phosphors.

Figure 1
(Invited) New Phosphor Exploration By the Single Particle Diagnosis Approach
Authors: Takeda Takashi , Funahashi Shiro , Xie Rong-Jun , Hirosaki Naoto
Published: February 2020

The luminescence property of Eu2+ or Ce3+doped phosphor is so affected by the coordination environment of luminescent center. The usage of different host material leads to new phosphor. The search for new phosphor is roughly classified to two methods. One is to employ a known crystal structure that is suitable for luminescent center doping and is not studied for host crystal. However, the promising candidates are already studied in most cases. The other is to find new host material by analyzing single crystals or powder product. In the single crystal analysis, a large size crystal is necessary to determine the crystal structure. In the powder process, at least it is necessary to synthesize the new material as single phase to solve the crystal structure from powder XRD data. Both normally require much time and effort. We have developed a new efficient method to find new phosphors from a powder mixture synthesized by a standard process. We have named the new method “Single Particle Diagnosis Approach”. Even if the powder product is not a single phase, by considering each (isolated) particle, it can be treated as a single phase and a single crystal. The crystal structure and luminescence properties of candidate single particles are analyzed and new phosphors are efficiently discovered.

Here we show some examples. 1) In Ba3N2-Si3N4-AlN quasi-ternary system, seven luminescent particles with different colors and morphologies were selected from the twenty powder samples. Among them, two particles were found to be new phosphors (yellow Ba5Si11Al7N25:Eu2+ and blue BaSi4Al3N9:Eu2+)1. 2) In addition to above example, Li3N was employed as the fourth component. As the number of components increases, the number of experiments dramatically increases in the combinatorial synthesis. In the single particle diagnosis approach, the increment of experiments number is suppressed. From Ba3N2-Si3N4-AlN-Li3N quasi-quaternary system, we found new green phosphor Ba2LiSi7AlN12:Eu2+. It shows a narrow-band emission and a small decrease of luminescence intensity even at 300 °C 2. 3) An interesting example is a new orange phosphor using Sr3N2-Si3N4-AlN quasi-ternary system. XRD and EDS analyses showed the composition of new phosphor particle to be Sr2Si2+3xAl2-xB2-2xN8+x:Eu2+. Boron component is not included in the staring materials. It is contamination from BN crucible. By using BN powder and Mo crucible instead, Sr2Si2+3xAl2-xB2-2xN8+x Eu2+ was obtained as a main phase3. One of the merits of this approach is that the small amount of a new phosphor (including unintended new phosphors) in a powder sample is not overlooked.

1. N. Hirosaki, T. Takeda, S. Funahashi, R.-J. Xie. Chem. Mat. 26 (2014) 4280.

2. T. Takeda, N. Hirosaki, S. Funahashi, R.-J. Xie. Chem. Mat. 27 (2015) 5892.

3. S. Funahashi, Y. Michiue, T. Takeda, R.-J. Xie, N. Hirosaki, Acta Cryst. C70 (2014) 452.
(Invited) Biohybrid Photoelectrodes Exploiting Effective Photosystem I - Electrode Contacts
Authors: Lisdat Fred , Feifel Sven Christian , Stieger Kai
Published: February 2020

Hybrid systems using the unique features of natural photosynthesis are increasingly in the focus of current research. Particularly the two protein complexes photosystem I and II  (PS) of the oxygenic photosynthesis have attracted the attention of researchers to build up new solar energy-converting systems. In such biohybrid systems an efficient coupling of PS with the electrode is essential. Besides the light-to-current conversion, the PS may also be used for light-driven enzymatic reactions resulting in photobioelectrocatalysis.

Different basic principles can be used by establishing communication between the PS and electrode surfaces. Here we want to avoid shuttle molecules and generate a surface allowing direct electron transfer (DET) between the excited protein and the electrode. This has been studied with photosystem 1 (PSI) from   Thermosynechococcus elongates.For efficient photocurrent generation a arther oriented immobilisation would be desirable which is complicated by the rather high molecular weight and the complex surface properties of PSI.

In this context we have been focusing on the directional assembly of PSI on highly conductive graphene electrodes. In order to adjust the surface properties different aromatic molecules have been applied onto the graphene [1]. The different Π-systems serve as an artificial scaffold harbouring functional groups which interplay with the PSI. Particularly important is the hydrophilic-hydrophobic balance on the surface. In conclusion, an effective and rather directed assembly of PSI and a large photocurrent density has been obtained. It has to be mentioned here that photocurrent generation occurs already at open circuit potential with now additional driving force applied. Depending on the modifier used an unidirectional photocurrent generation can be achieved by this approach. Via the artificially modified graphene surface we have been able to create biohybrid systems with an improved photocurrent output. Here not only adsorption can be used for the functional assembly but also covalent linkage of PSI to the surface. A systematic investigation on the protein assembly and the resulting photoelectrochemical properties will be presented. For this quartz crystal microbalance experiments, chopped light voltammetry, constant potential measurements, photoaction spectra and experiments with methyl viologen have been performed.

Moreover it can be demonstrated that the performance of such PSI electrodes can be further improved. Here nanoparticles are additionally coupled to the graphene-PSI system in order to enhance current generation under illumination.

[1] S. C. Feifel, K. R. Stieger, H. Lokstein, H. Lux, F. Lisdat, Journal of Materials Chemistry A 3 (23) (2015) 12188-12196

[2] S. C. Feifel, H. Lokstein, M. Hejazi, A. Zouni, F. Lisdat, Langmuir 31 (38) (2015) 10590-10598
Effects of Temperature and Calciums on the Treatment of Organics and Nutrient in Swine Wastewater Using an Integrated Bioelectrochemical Ion-Exchange System
Authors: Lim Seung Joo , Kim Tak-Hyun
Published: February 2020

Introduction

Since husbandry industry has intensively developed, a great amount of high-strength swine wastewater has been generated. Even though several investigators have developed various processes for the treatment of swine wastewater, it was continuously required to develop more stable process high-strength wastewater. The objective of this paper was to investigate simultaneous removal of organic matter and nutrient in swine wastewater using an ion-exchange membrane system.

Materials and Methods

The ion-exchange membrane system consisted of three chamber (A, B and C) was separated by a cationic exchange membrane and an anionic exchange membrane(Figure 1). Ammonium ion in swine wastewater was ion-exchanged between a chamber A and a chamber B via a CEM. The ammonium ion was biologically oxidized to nitrate in a chamber B and nitrate was transported via an AEM and denitrified in a chamber C. Organic matter in the influent was acidified in a chamber A and used as electron donor for denitrification in a chamber C. COD, ammonia and phosphate used in this study were 9080.4 mg/L, 1910.6 mg/L and 43.2 mg/L.

Results and Discussion

Maximum COD and ammonia removal efficiencies were 86.4% and 78.4%. Average COD and ammonia removal were 77.1% and 63.6% in Figure 2. When temperature sharply decreased to 13oC, the ammonia removal efficiency maintained about 42.0% due to the high ammonium flux (1.54 mg N/m2/sec) and MLVSS ratio (0.83) in Figure 2. As shown in Figure 3, the maximum phosphate removal efficiency was 91.0% (Ave.: 59.7%), and the phosphate removal was highly correlated with calcium consumption. This shows that phosphorus can be removed as a Ca3(PO4)2 or the coprecipitation of phosphate with calcite.

Figure 1
High Efficiency Insertion of Antibody-Immobilized Nanoneedle into Living Cells for in Situ detection of Cytoskeletal Proteins
Authors: Nakamura Chikashi , Shimizu Keita , Kawamura Ryuzo , Iijima Masumi , Kuroda Shun’ichi , Fukazawa Kyoko , Ishihara Kazuhiko
Published: February 2020

We have been developed a technology to detect cytoskeletal proteins, such as actin microfilament (1), tubulin (2) and intermediate filaments (3) in living cells using antibody immobilized nanoneedle and AFM. The nanoneedle can be inserted into cells by penetrating membranes with minimal damage to cells due to the ultra-thin shape of 200 nm in diameter and aspect ratio over 50. In this in situprotein detection, force to rupture the interactions between antibodies and cytoskeletal proteins is evaluated. Even by using such thin material, there is a problem of low efficiency of penetration through plasma membrane owing to lipid bilayer’s high fluidity under the condition of normal cultivation temperature of 37°C. In this study, we investigated the effect of impact speed of nanoneedle and insertion under low temperature condition to improve the membrane-penetration efficiency.

We chose vimentin, a member of intermediate filaments, as a target protein, which is expressed in variety of cell species, e.g. mesenchymal cell. We immobilized anti-vimentin antibodies onto nanoneedle surface via bionanocapsules displaying Fc-binding ZZ domains derived from protein A. HeLa cells and MCF-7 cells were utilized as vimentin-positive and vimentin-negative cells, respectively. Magnitude of peak forces to rupture antibody-vimentin complexes which appear during the evacuation process of the nanoneedle from the cell was analyzed to evaluate effect of impact speed and temperature on the nanoneedle penetration efficiency. Although the impact speed of nanoneedle higher than 10 µm/s (conventional speed) did not show increment of fishing force detection efficiency, medium temperature of 4°C lower temperature obviously contributed to increment of the average fishing force, from 23 nN to 57 nN. The rupture force of singe interaction between the antibody and vimentin at 4°C was almost same that at 37°C. The results indicated that the temperature of 4°C was presumably under phase transition of the plasma membrane and the condition could enhance penetration of the nanoneedle.

(1) Silberberg, et al., Biosens. Bioelectron., 40, 3-9 (2013)

(2) Silberberg, et al., J. Biosci. Bioeng., 117, 107-112 (2014)

(3) Mieda, et al., Biosens. Bioelectron., 31, 323-329 (2012)
Anodic Chlorination of Chalcogenophenes in Conjugated Polymers
Authors: Inagi Shinsuke , Okazaki Daichi , Shida Naoki , Nishiyama Hiroki , Tomita Ikuyoshi
Published: February 2020

We have developed the electrochemical post-functionalization method of π-conjugated polymers in the film state on an electrode. Among them, poly(3-hexylthiophene) was successfully chlorinated at the 4-position of the thiophene rings by anodic oxidation and following introduction of chloride ions used as a supporting salt.

  In this study, we investigated the anodic chlorination of poly(3-alkylchalcogenophene)s including poly(3-alkylselenophene)s, copolymers of 3-alkylthiophenes and 3-alkylselenophenes. Constant potential electrolysis of these π-conjugated polymers proceeded to give the corresponding chlorinated polymers. Poly(3-hexylselenophene) exhibited higher reactivity than poly(3-hexylthiophene) owing to its lower oxidation potential. Chalcogenophene units having 2-ethylhexyl group at the 3-position did not undergo anodic chlorination probably due to the steric hindrance of the side chains. Accordingly, a block copolymer consisting of 3-hexylselenophene and 3-(2-ethylhexyl)thiophene was selectively chlorinated only in the poly(3-hexylselenophene) segments.

Figure 1
Electrochemical Approach to Evaluate the Wettability of Rough Surfaces
Authors: Zahiri Beniamin , Sow Pradeep Kumar , Haow Kung Chun , Mérida Walter
Published: February 2020

The wettability is usually determined based on the optical measurement of the contact angle from a droplet placed on the surface. Theoretical models show that this contact angle depends on the solid-liquid interaction under the droplet, which is optically inaccessible. Here, we present an electrochemical method for evaluating the wetted area under the droplet for a rough surface. The method takes advantage of the electrochemical double layer capacitance, which can be quantified using electrochemical approaches such as cyclic voltammetry. This double layer capacitance is proportional to the ion-accessible solid-liquid interfacial area and therefore can be used as a characterization metric. The experimental approach includes simultaneous measurement of the contact angle along with the capacitance. We have shown the capability of this method for a series of carbonaceous surfaces with varying roughness. The experimental results have been correlated to the Wenzel and Cassie-Baxter wettability theories. This approach is applicable for irregular roughness features and therefore can be used to study the wetting behaviour of different surface structures. We believe this work has significant implications as a tool to characterize and understand the wettability on rough surfaces and also facilitates the development of mechanistic and predictable mathematical models for surface wettability.
Double Salt Ionic Liquids Containing the Trihexyl(tetradecyl)phosphonium Cation: The Ability to Tune the Solubility of Aromatics, Ethers, and Lipophilic Compounds
Authors: Wang Hui , Berton Paula , Myerson Allan S. , Rogers Robin Don
Published: February 2020

Ionic liquids (ILs) certainly have some interesting properties and this has led to tremendous growth in interest, knowledge, and applications of these materials in a diverse array of science and technology. However, the field is still dominated by study of the simplest binary salts and an over reliance on ‘magic’ solvent properties which currently limits their creative use for new technologies. Lately, the scientific community has been attracted towards “IL/IL mixtures” prepared by mixing two or more ILs, and (as was the case with the early studies of the binary salts), a focus on specific physicochemical properties. Interestingly, crystalline salts dissolved in ILs are seen as a different class of liquids (e.g., high ionicity ILs). We have found that the physical, chemical, and biological (i.e., the materials) properties of IL/IL mixtures (or Double Salt Ionic Liquids, DSILs, as we like to call them) seem to be mainly controlled by the intrinsic ion interactions which are influenced by the exact ion composition. Perhaps, a new way of thinking about these multi-ion fluids is needed in order to direct research toward an understanding of the complex and varied types of interionic forces possible in a liquid. We have proposed the DSIL concept to help guide our work towards obtaining this deeper understanding. In this nomenclature, any homogeneous liquid containing three or more ions (no matter how they are prepared) are described as DSILs and are defined by the specific ion combinations present.

In this presentation, these concepts will be illustrated by discussion of the chemical, physical, and biological properties of several DSIL systems chosen to explore different interactions between the ions (i.e., Coulombic, hydrogen bonding, dispersion, etc.). While we will present physical properties as a function of composition, we will focus more on chemical properties illustrated by the solubilities of pharmaceuticals and on biological properties illustrated by changes in membrane transport, both as a function of ion composition. Spectroscopic studies will be presented to provide insight into specific ion-ion interactions. For example, the solubility of active pharmaceutical ingredients with different acidity and lipophilicity are finely tunable by varying the ratio of the ions (Figure 1). Such studies support the concept that each DSIL is a unique ionic fluid that is able to provide tunable property sets derived from the ions present and that these properties can be controlled by choosing the nature and the abundance of the ions.

Figure 1