bluuebunny/crossref_metadata_2025 huggingface dataset:
(Keynote) Detecting Small Molecule-Membrane Protein Binding Kinetics
Authors: Tao Nongjian
Published: February 2020

Detection of molecular interactions is critical for understanding many biological processes, for detecting disease biomarkers, and for screening drug candidates. To date the most widely used detection technique uses fluorescence dyes. While useful, the approach can be problematic when applied to the detection of small molecules, because the dye molecules may significantly alter the binding activities of the small molecules. Label-free detection techniques have been developed, but they largely rely on the detection of the mass of a molecule, which are difficult for small molecules. Small molecules are the most popular form of drugs, and play important roles in many biological processes, including post-translational modification of proteins, metabolic and cellular signaling processes. A capability to detect small molecules will have large impacts on the understanding of these processes, detecting of diseases, and discovery of drugs.

 We show that molecular interactions with membrane proteins induce mechanical deformation in cellular membrane, and real-time monitoring of the deformation allows quantitative analysis of membrane protein binding kinetics. This new strategy provides mechanical amplification to small binding signals, which, together with a differential optical detection algorithm to track cell deformation with 0.5 nm accuracy, make it possible to detect small molecule interactions with membrane proteins. This capability also allows study of heterogeneous nature of cells by analyzing the binding kinetics variability between different cells, and different regions of a single cell.
Monitoring of Nitric Oxide Levels Released from NOS-Loaded Liposomes in Proximity of Cystic Fibrosis Cell Line Models
Authors: Bayachou Mekki , Bose Tiyash , Henderson Tericka
Published: February 2020

Nitric oxide (NO) is a biological free radical, associated with many physiological and pathological processes that include neuronal signaling, immune response and inflammatory response. In mammalian organisms, NO is produced from L-arginine in an NADPH-dependent reaction catalyzed by a family of nitric oxide synthase (NOS) enzymes. Fluctuations in NO levels generally accompany a number of inflammatory diseases. Cystic Fibrosis (CF) is an autosomal recessive genetic disease that chronically affects the lungs. It has been found that exhaled NO levels remains unchanged or reduced in cystic fibrosis patients unlike other inflammatory lung diseases like asthma where it increases. However it is not clear whether the lower NO levels in cystic fibrosis correlate with lowered production of this metabolite in the bronchial epithelium. Also, it has been proposed recently that nitric oxide can be used as a potent antimicrobial molecule to treat bacterial infection of CF tissue. Nitric oxide’s role in CF is mutlifaceted. In this work, we want to establish a basic system to understand how nitric oxide interacts with CF cells versus normal cells by monitoring levels of nitric oxide released from NOS-loaded liposomes on normal cells and CF cells.

We will present work establishing the performance of combined reference/working electrodes modified with ruthenium oxide and poly(3,4-ethylenedioxythiophene) (PEDOT) for catalytic detection of nitric oxide. We will then show how we can use this nitric oxide sensitive probe to measure levels of nitric oxide from NOS-loaded liposomes. In this case, nitric oxide is triggered exogenously both in proximity of normal cells and near a CF cell line model. We will compare and contrast the observed amperometric levels of nitric oxide and discuss the results in light of potential biological implication of nitric oxide with the two cell models.
Ethanol Gas Sensing Behavior of ZnO Nanorods Decorated with Various Metal Catalysts
Authors: Park Hyejin , Lee Eunji , Chung Yoonsung , Kim Dong-Joo
Published: February 2020

Solid gas sensors are widely employed owing to their good stability and excellent gas responses [1]. However, the operating temperature to activate reaction sites of oxide semiconductor is relatively high to widen the applications [2]. As demands of gas sensors have increased in various fields, one of the research issues is to lower the operation temperature to enhance adaptability. To lower sensing temperature of semiconductor oxide sensors from several hundred Celsius to room temperature and to improve the gas selectivity, compositional gradient of catalysts was explored based on the catalyst effects on gas sensing mechanism and performance. Two metals having different catalytic activities were utilized: Platinum (Pt) and palladium (Pd). The thickness of the catalyst layer was kept constant, and only composition (ratio of the components) was changed to investigate the effect of the catalyst composites [3].

In this study, deposition of metal catalysts on ZnO NR gas sensing devices was successfully conducted by the sputter method. Pd and Pt were selected as catalysts to improve the gas sensing behaviors such as gas response, gas response rate, and selectivity. The amount of 1 or 2 % of catalysts was deposited on the gas sensing devices. When metal catalysts were applied, operation temperature of ZnO NR gas sensors was successfully reduced from 300 °C to 100 °C. Moreover, enhancement in gas sensing behaviors was observed with catalysts but degraded gas sensing behavior occurred with large amount of the catalysts. Improvement was resulting from the increase in activate sites and modification of the Fermi energy level. The degradation was primarily due to the blockage of activate sites caused by excessive amounts of catalysts. Catalysts decorated ZnO NR gas sensors can be a candidate for lowered operating temperature with great gas responses.

This research was partially supported by the Korea Institute of Energy Technology Evaluation and Planning (20158520000210) grant funded by the Korea Government Ministry of Trade, Industry and Energy, a grant from a Strategic Research Project (2013-0132) funded by the Korea Institute of Construction Technology, and Auburn University IGP.

[1]     Azad, A. M., et al. Journal of the Electrochemical Society 139.12 (1992): 3690-3704..

[2]     Morrison, S. Roy. Sensors and actuators 12.4 (1987): 425-440..

[3] Müller G, Friedberger A, Kreisl P, Ahlers S, Schulz O, Becker T. Thin Solid Films. 2003;436(1):34-45.

Figure 1
Development and Characterization of Fuel Cell Sensor for Potential Transdermal Ethanol Sensing
Authors: Jalal Ahmed Hasnain , Umasankar Yogeswaran , Bhansali Shekhar
Published: February 2020

The existing fuel cell alcohol sensors [1-3] suffer severely with humidity interference and signal instability. This interference and instability renders the existing sensors useless for transdermal ethanol detection in non-ideal environment. To address these issues of the fuel cell alcohol sensor, various electrode designs along with the catalysts were explored in this work. The design includes both two and three electrode setups with the Nafion as proton exchange membrane, where the three electrode setup provided stable signal compared to two electrode setup. Considering the development of a potential transdermal ethanol sensor, the ethanol exposed area of the working electrode was optimized to 1cm2and reference and counter electrode were placed on the other side of the Nafion membrane. For the ethanol measurements in the three electrode system, a fixed potential was applied between working and reference electrode and the change in current due to ethanol concentration was measured between working and counter electrode. To eliminate the interference due to humidity the applied potential for measurement was same as that of the open circuit potential (OCP) of the fuel cell in presence of humidity. Catalysts such as Ni, Cu, Fe and Au were studied, where Ni has better catalytic activity for ethanol oxidation and oxygen reduction [4] providing almost 600, 300 and 3 times greater current response than  Au, Fe and Cu respectively (Figure 1). The sensitivity for the sensor was found 0.062 nA/ppm in vapor phase for this Ni catalyst.

Figure 1: Amperometric responses of fuel cell sensor for ethanol (a) Fe, (b) Au, (c) Ni and (d) Cu catalysts.

Acknowledgements:

This work is funded by the ASSIST NSF ERC and NSF I-Corps Teams.

References:

1. Jeng, K.-T.; Huang, W. M.; Chien, C. C.  and Hsu, N.-Y. 2007. A versatile electrochemical fuel sensor for direct membrane fuel cell applications. Sens Act B: Chem 125:278-283.

2. Jiang, L.; Zhou, Z.; Wang, S.; Liu, J.; Zhao, X.; Sun, G.; Xin, Q. and Zhou, B. 2004. Development of air-breathing direct ethanol fuel cells with PtSn as anode. Prepr Pap-Am Chem Soc, Div Fuel Chem, 49:668-670.

3. Robertson, R.; Vanlaar W. and Simpson, H. 2007. Continuous transdermal alcohol monitoring: A primer for criminal justice professionals. The Traff Inj Resc,ISBN: 978-0-920071-60-1.

4.  Barbosa, A. F. B.; Oliveira, V. L.; Drunen V. and Tremiliosi-Filho, G. 2015. Ethanol electro-oxidation reaction using a polycrystalline nickel electrode in alkaline media: Temperature influence and reaction mechanism. J. of
Electroanal Soc, 746: 31-38.

Figure 1
A DFT Study of CO2-H2 Co-Adsorption on Ni/YSZ(111) for Solid Oxide Fuel Cell Applications
Authors: Essadek Abdelaziz , Roldan Martinez Alberto , de Leeuw Nora
Published: February 2020

Solid Oxide Fuel Cell (SOFC) devices convert chemical energy into electrical energy by oxidizing fuels such as hydrogen, natural gas, ethanol or hydrocarbon mixtures, which highlights the capability of SOFCs as candidates for applications in stationary power generation. The main species used as fuel in the SOFC are H2 and CO which are oxidized at the anode [1]. Instead of pure H2 or CO, H2/CO mixtures can be used leading to more complicated mechanisms since other processes such as the water-gas shift reaction (CO + H2O ↔ CO2 + H2) are involved.

Robust materials are needed for SOFC since the working temperature is approximately equal to 800˚C. For example, a suitable anode is Ni/YSZ (nickel – yttria stabilized zirconia) since it has a high catalytic activity, mechanical and chemical stability and compatibility with the electrolyte under working conditions [2]. It is well known that the performance of the Ni/YSZ cermet depends on the microstructure and the distribution of Ni and YSZ phases in the cermet [3]. Additionally, this performance depends on the key reactions occurring at the triple phase boundary where the gas phase, Ni particles and YSZ surface meet. Thus, it is relevant to understand, at the atomic scale, the structure of Ni/YSZ and its interaction with the gas phase, and in particular CO2 and H2.

To simulate the interaction of CO2 and H2 with Ni-YSZ, we have used electronic structure calculations based on the Density Functional Theory using the Vienna Ab-initio Simulation Package (VASP). We have studied the deposition of Nin (n=4-10) clusters on the YSZ(111) followed by the adsorption of molecules on the optimised Nin/YSZ(111) structures and calculated the geometric and electronic structure at the most stable adsorption site. We have also analysed the reaction path of the reverse water-gas shift reaction (CO2 + H2 ↔ CO + H2O) on three different Nin/YSZ(111) (n = 5, 6 and 10) interfaces, considering two possible pathways intermediates: hydrocarboxyl or formate.

Finally, we have observed that both CO2 and H2 prefer to adsorb on the Nin cluster rather than on the surface. On the metal cluster the CO2 molecule is activated and the H2 is dissociated upon adsorption, whereas charge is transferred from the cluster to the molecules. We have determined two intermediate states and three intermediate states for the carboxylic acid and formate intermediate pathway, respectively, on the three Nin/YSZ(111) (n = 5, 6 and 10) interfaces.

References

1. J. Hanna, W. Y. Lee, Y. Shi and A. F. Ghoniem, Prog. Energy Combust. Sci., 2014, 40, 74–111.

2. Kim, S. et al. Solid State Ionics, (2007),

178, 1304–1309.

3. Kim, S. et al. Solid State Ionics, (2006), 177, 931–938.
Molecular Dynamic Study of Gadolinium-Doped Ceria and Yttria Stabilized Zirconia Grain Boundaries
Authors: Aparicio Angles Xavier , de Leeuw Nora H.
Published: February 2020

Gadolinium-doped ceria (GDC) and yttria-stabilised zirconia (YSZ) are very well known materials, used as components for solid-oxide fuel cells (SOFC). They both are very good electrolytes, and they have been vastly used in this sense. The main difference between GDC and YSZ when used as electrolytes is that GDC shows higher oxygen conduction at lower temperatures, leading to the possibility of developing intermediate temperatures SOFC (IT-SOFC). But their versatility allow us to use them also as anode materials, like YSZ, which in combination of nickel particles, is used to catalyse oxygen reduction. In addition, YSZ combined with nickel (Ni-YSZ) is also used as anode in SOFC, in combination with GDC as electrolyte.

In any case, the main role of both is related to oxygen migration, i.e. ionic conductivity. In GDC and YSZ oxygen migration undergoes via a vacancy hopping mechanism. Vacancy mobility depends on several aspects, like the association energy with respect to the dopants, dopants concentration, or temperature, whose effects are very well studied. Grain boundaries (GBs) are also known to have an important impact in conductivity, despite that little is known about their influence. From an experimental point of view, results suggests that the presence of these GBs

offers faster migration channels. On the other hand, dopants tend to segregate to GBs, thus trapping oxygen vacancies and reducing the ionic conductivity of the materials. To clearly understand the role of GBs in the oxygen conductivity, it is necessary to study the system at the atomic level. One of the main issues, however, is that the model must include all the chemical and structural complexity inherent to GBs, which force us to generate very large models.

In this work, and based on interatomic potential and molecular dynamic techniques, we present a strategy based on the work of Sayle et al. (2007) referred as Amorphisation and Recrystallization (A&R). With this methodology, consisting on melting and recrystallizing the system at high pressures, we are able to obtain accurate models that allow us to describe realistic GBs including dislocations and translocations. After generating different models, we have performed a series of molecular dynamic simulations in order to see the effect of the temperature in the structure,

ionic mobility and also oxygen diffusion and therefore its conductivity. Results seem to indicate that indeed, the presence of the grain boundaries are beneficial for the enhancement of the oxygen diffusion in the system.
Mesoscale Modeling of Lithium-Ion Battery Electrodes: Computational Requirements and the Role of Polymeric Binders
Authors: Roberts Scott A. , Trembacki Bradley L. , Mendoza Hector , Long Kevin N. , Brunini Victor E. , Grillet Anne M.
Published: February 2020

In recent years, advances in the imaging and computational representation of lithium-ion battery electrodes have made it possible to perform electrochemical and mechanical simulations on reconstructed electrode microstructures.  These simulation capabilities hold great potential for informing electrode design and manufacturing processes by providing insight into the effects of material choices and manufacturing conditions on the microstructure.  Mesoscale simulations are also used to investigate the performance of the battery, including the elucidation of capacity fade mechanisms.

Realistic mesoscale simulations, however, are not without their challenges.  Significant domain sizes containing a large number of active particles are necessary to obtain a representative volume, and significant mesh resolution must be used to capture the details of the complex particle shapes.  Additionally, the complex particle shapes can lead to poorly formed mesh elements leading to difficult numerical solutions.  In this talk we address how these issues affect the ability to robustly perform simulations.

Many electrode images are also unable to resolve the polymeric binder.  The location and properties of this binder are suspected to have a strong effect on battery performance.  Coupled electrochemical-mechanical simulations are performed with both approximate and reconstructed binder representations.  We use these simulations to elucidate the effect of binder location on electrode performance.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Computer Modelling Studies of Lithium Transport in Nanoporous and Bulk Beta-MnO2
Authors: Ngoepe Phuti Esrom , Sayle Thi X T , Sayle Dean C
Published: February 2020

Nanostructured manganese dioxides (MnO2) are among the promising materials for high-capacity lithium-ion batteries [1], lithium air batteries [2] and supercapacitors [3], that can be used in electric vehicles and other consumer electronics. Simulated amorphisation recrystallisation method has been successfully used to nucleate and crystallise bulk [4] and nanoporous β-MnO2 [5]. In the current study we demonstrate that nanostructuring of MnO2 results in the exposure of a variety of surfaces to be exposed at the (internal) pores because of the high curvature of the material; the low energy MnO2(101) surface does not dominate the morphology. This nanostructuring facilitates a wide variation of entrance sites into the 1x1 tunnels in contrast to the parent bulk material. In particular, the activation energy associated with Li intercalation/deintercallation into the (101) surface of the bulk material is calculated to be 0.6eV. On the other hand, for the mesoporous material we calculate the activation energy for Li transport and deintercallation to be 0.4eV.

1] B.X. Li, G.X. Rong, Y. Xie, L.F. Huang and C.Q. Feng, Inorg. Chem. 2006, 45, 6404.

[2] A. Débart, A.J. Paterson, J. Bao and P.G. Bruce, Angew. Chem., Int. Ed. 2008, 47, 4521.

[3] W. Wei, X. Cui, W. Chen and D.G. Ivey, Chem. Soc. Rev. 2011, 40, 1697

[4] T.X.T. Sayle, C.R.A. Catlow, R.R. Maphanga, P.E. Ngoepe and D.C. Sayle, J. Crystal Growth, 294,118-129, 2006.

[5] T.X.T. Sayle, R.R. Maphanga, P.E. Ngoepe and D.C. Sayle, J. American Chem. Soc., 131, 6161-6173, 2009.
(Invited) Comparative First Principles Studies of Hybrid Li-Ion/Li-Oxygen Battery Materials
Authors: Li Liang , Kinaci Alper , Chan Maria K. Y.
Published: February 2020

In the Center for Electrochemical Energy Science (CEES) Energy Frontier Research Center, we are investigating a new class of energy storage materials – hybrid Li-ion/Li-oxygen materials – that combine transition metal and oxygen redox chemistries to deliver high energy storage capacity [1, 2, 3]. The electrochemical reactions, structural and electronic structure evolution of these materials are complex, requiring a combination of in-depth characterization and first principles modeling. In this talk, we will report on a comparison study of several examples of hybrid Li-ion/Li-oxygen materials using density functional theory calculations. We will discuss the structural and electronic structure reasons for differences in reaction pathways and competition between transition metal vs oxygen redox chemistries. Insight towards selecting and designing promising hybrid battery materials gleaned from the comparison will be discussed.

[1] L. Trahey, C. S. Johnson, J. T. Vaughey, S.-H. Kang, L. J. Hardwick, S. A. Freunberger, P. G. Bruce, M. M. Thackeray, “Activated Lithium-Metal-Oxides as Catalytic Electrodes for Li-O2 Cells,” Electrochemical and Solid-State Letters, 2011, 14, A64.

[2] M. M. Thackeray, M. K. Y. Chan, L. Trahey, S. Kirklin, and C. Wolverton, “Vision for Designing High-Energy, Hybrid Li Ion/Li–O2 Cells,” Journal of Physical Chemistry Letters, 2013, 4, 3607.

[3] Z. Yang, L. Trahey, Y. Ren, M. K. Y. Chan, C. Lin, J. Okasinski, and M. M. Thackeray, “In-Situ High-Energy Synchrotron X-ray Diffraction Studies and First Principles Modeling of α-MnO2 Electrodes in Li-O2 and Li-ion Coin Cells,” Journal of Materials Chemistry A, 2015, 3, 7389.
Modeling of Thermal Runaway-Induced Li-Ion Battery Failure Integrating Multiphysics and Multiscale Approaches As Well As Ageing Interaction
Authors: Abada Sara , Petit Martin , Lecocq Amandine , Huet François , Sauvant-Moynot Valérie , Marlair Guy
Published: February 2020

Li-ion batteries are currently the preferred solution to store electrical energy. However, their safety is still a challenging issue. Since we are more and more moving from rechargeable battery packs working with water-based electrolytes to more powerful or more energy containing ones utilizing non aqueous electrolytes, risk profiles have changed abruptly from uncontrolled release of hydrogen during charging (e.g. in lead acid or Nickel Metal hydride type of batteries) to the so called and much more safety challenging thermal runaway process. Indeed, thermal runaway has been identified as the major concern in terms of Li-ion battery safety issues on its full value chain inducing significant thermal and chemical threats [1]. The phenomenon entails a cascade of stages initiated at material level and may be induced by various abuse conditions (abnormal disorders of thermal, mechanical or electrical nature). Progress in understanding this complex phenomenon, so far essentially achieved by experimentations at material and cell levels have opened the door to safer battery design or better safety management through various modeling techniques [2].

This paper deals with an innovative approach in such a contribution which consists in the development and validation of a physical and accurate model of Li-ion batteries electro-thermal behavior nearby thermal runaway conditions which includes sub-models reflecting ageing effect interaction. Therefore, enlarged application is targeted for such a model, depending on validation domain, since it is capable of analyzing the risk of failure induced by thermal runaway for applications to safety management expanded to new and aged batteries, or for safe “second life” use of Li-ion batteries.

 The presentation will describe the overall methodology considered (see fig.1), provide the set of electrochemical-thermal sub-models used, describe the experimental plans based on three series of Li-ion cells (see fig. 2) developed for i) adjusting requested thermal parameters in the sub-models and ii) for validation purposes and eventually present results obtained so far.

References

[1] P. Ribière, S. Grugeon, M. Morcrette, S. Boyanov, S. Laruelle, G. Marlair, Energy Environ. Sci. 5 (2012) 5271.

[2] Sara Abada, Martin Petit, Amandine Lecocq2, Guy Marlair, François Huet, Valérie Sauvant-Moynot,
J. Power Sources, (2015),
in press, http://dx.doi.org/10.1016/j.powersour.2015.11.100

Figure 1
Sensitive Detection of Platelet-Derived Growth Factor Using a Multi-Parametric/Multimodal Spectroscopy Apparatus
Authors: Zhou Lang , Arugula Mary A , Simonian Aleksandr
Published: February 2020

Platelet-derived growth factor (PDGF) are proteins that play an important role in the regulation of tumour growth and division. PDGF has been associated with cancer and other proliferative disease states, such as atherosclerosis and glomerulonephritis. However, as a potential cancer marker, PDGF is difficult to detect due to its trace amount in real blood sample. Recently developed Electrochemical Proximity Assay (ECPA) is an extremely flexible and sensitive technique with high potential for quantitation of a variety of proteins in clinical laboratory settings or at the point-of-care systems. Here, a newly designed Multi-Parametric/Multimodal Spectroscopy Apparatus techniques was used for PDGF sensitive detection. With the combined advantages of three surface characterization techniques such as ECPA, surface enhanced fluorescence and surface plasmon resonance spectroscopy, the sensitivity of PDGF quantification was significantly improved with potential to reach as low as fmol level. Additionally, the mechanisms of action and dynamics of sensing and/or protein recognition in the process of ECPA was studied.
Etching Studies of BCN Thin Films
Authors: Prakash Adithya , Sundaram Kalpathy B
Published: February 2020

The ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated circuit (ULSI) devices. Recently it has been found that Boron Nitride (BN) films can achieve low-k values around and hardness comparable to diamond [1][2].  BN is hygroscopic in nature. In this respect carbon can be added to the BN structure to produce Boron Carbon Nitride (BCN) films as the possible substitute for BN. The minimum dielectric constant achieved by plasma assisted chemical vapor deposition for a BCN thin film was reported to be 1.9. [2] The BCN films are also instrumental in suppressing the Cu migration [3]. The Young’s modulus of BCN films are reported well above 20 GPa making it one of the suitable options for low-k materials [4].

In the present work, BCN films were deposited by dual target sputtering of boron carbide (BC) target (DC), boron nitride (BN) target (RF) in nitrogen ambient with argon. The films were deposited under various N­2/Ar gas flow ratios and temperature. BCN is etched using an etchant that consists of 16 parts of Phosphoric acid (H3PO4), 1 part of Nitric acid (HNO3), 1 part of Acetic acid (CH3COOH), 20 parts of DI water. Various plots of etch rates with respect to deposition parameters and Arrhenius plots are studied.

REFERENCES

[1] Jun Liu, Kian Ping Loh, Ming Lin, Yong Lim Foo, Wei De Wang, and Dong Zhi Ch, Journal of Applied Physics, 96 (2004) 6679.

[2] Riedel R., Advanced Materials, 4 (1992) 759.

 [3] M. K Mazumder, R. Moriyama, D. Watanabe, C. Kimura, H. Aoki, and T. Sugino: Jpn. J. Appl. Phys. 46 (2007) 2006.

[4] C. Morant, D. Caceres, J. M. Sanz, and E. Elizalde: Diamond Relat. Mater. 16 (2007) 1441.
Organic Thin-Film Transistors Based on Asymmetric Chrysene Derivatives
Authors: Murata Shuhei , Otsuki HIroyuki , Okamoto Kazuo , Kunugi Yoshihito
Published: February 2020

Organic field-effect transistors (OFETs) have received significant attention because of the potential use in flexible and/or disposable portable electronic devices. The charge carrier mobility is strongly influenced by the organic semiconductor layer. But, it has been still lower than the charge carrier mobility for inorganic MOS FETs. Therefore, great efforts have been made toward the development of various semiconducting small molecules and polymers. Among these, fused π-conjugated semiconductors such as acene, thienoacene, and thienothiophene based compounds are promising materials for high-performance OFETs.

In this study we investigated the characterization of thin-film OFETs based on newly developed compound,asymmetric chrysene derivatives which regard phenyl chrysene as the main structure (Fig. 1). It is expected that the large and planar chrysene core would provide intermolecular interactions to achieve high charge carrier mobilities, and asymmetric molecular structure are promising for improvement of solubility.

Thin-films are fabricated by spin-coat and vapor deposition method on a n-doped Si wafer with a 220 nm thermally grown SiO2. The spin-coated films (50 nm thick) were fabricated by 0.4 wt% toluene solution at 2000 rpm for 30 sec. The vapor deposited films were deposited on insulating SiO2 layer was treated with a thin-film (ca. 30 nm) of a polymer insulator such as polystyrene (PS) or CYTOP (Asahi Glass Co.). Molecular packing and orientation was characterized by atomic force microscope (AFM), and X-ray diffractions　(XRDs) analysis. The electrical properties of the OFET devices were measured by using an Agilent 4155C semiconductor parameter analyzer under vacuum at room temperature.

The solution processed asymmetric chrysene based transistors showed typical p-channel FET characteristics. The field-effect carrier mobility of the device was determined to be 5.9×10-4cm2V-1s-1 and on/off ratio of 105 for P-28CR-6. The vaper deposited P-28CR-n based OFET shows also typical p-channel FET characteristics and their mobilities  are strongly correlated with the applied polymer insulator, and the best field-effect mobility (3.1 cm2V-1s-1 and on/off ratio of 104) was obtained for the CYTOP-covered device. As shown in Fig. 2(b) carrier mobility is correlated by the length of alkyl chain for P-28CR-n. According to XRD analysis, orientation angle of chrysene core of P-28CR-n to the substrate is also correlated to the alkyl chain length of P-28CR-n. Interestingly, the field-effect mobility shows a similar trend to the orientation angle of the chrysene core for the alkyl chain length.

Figure 1
Rapid Determination of Diffusion Coefficients Utilizing Electrochemical Time of Diffusion (ETOD)
Authors: Moldenhauer Jonathan C , Paul David W
Published: February 2020

The electrochemical time of diffusion (ETOD) experiment (formerly called electrochemical time of flight (ETOF)) is a generate/detect experiment that is performed on electrode arrays(1-5) . This method has been utilized to determine diffusion coefficients of electrochemically generated analytes, by measuring the time over which an analyte travels a given distance.  Here we show an alternate analysis for ETOD data from what is typically found in the literature. We rearrange the equation from d=K√(D*tmc) where d is the distance, K is a geometric constant determined by the array, D is the diffusion coefficient of the analyte, and tmc is the time of maximum collection on the chronoamperometric curve(2) to √tmc=d/(K√D). This rearrangement allows for a “calibration curve” to be developed for an electrode array at a single distance with multiple analytes, each with a different and known diffusion coefficient, instead of using only a single analyte measuring tmc
at electrodes of multiple distances from a generator. This decreases the number of experiments that need to be performed to determine an unknown diffusion coefficient. This method also has all the advantages of more traditional ETOD/ETOF experiments in that it greatly simplifies the determination of diffusion coefficients as the concentration of the analyte, the area of the electrode, the viscosity of the solution, and the electron transfer kinetics can remain unknown. Here we show that diffusion coefficients determined by ETOD are comparable to those found in the literature, and that diffusion coefficients of probe molecules thickened by ethylene glycol are in reasonable agreement to those estimated using the Stokes-Einstein equation. Diffusion coefficients for ferricyanide, ferrocyanide, ruthenium(III) hexamine and dopamine were found within 5% of those from the literature, while the diffusion coefficients for the same probes through thickened solutions fell within 16% of the values predicted using the Stokes-Einstein Equation. With the consensus in the community being that the Stokes-Einstein equation can provide predicted diffusion coefficients within 35% of actual observed values (6), it can be considered that our method can provide diffusion coefficients that are reasonable for the previously unknown diffusion coefficients.

References

1.            S. Licht, V. Cammarata and M. S. Wrighton, J. Phys. Chem., 94, 6133 (1990).

2.            C. Amatore, C. Sella and L. Thouin, J. Electroanal. Chem., 593, 194 (2006).

3.            K. Slowinska, M. J. Johnson, M. Wittek, G. Moller and M. Majda, Proc. - Electrochem. Soc., 2001-18, 130 (2001).

4.            D. Ky, C. K. Liu, C. Marumoto, L. Castaneda and K. Slowinska, J. Controlled Release, 112, 214 (2006).

5.            F. Liu, G. Kolesov and B. A. Parkinson, J. Electrochem. Soc., 161, H3015 (2014).

6.            H. A. Kooijman, Ind. Eng. Chem. Res., 41, 3326 (2002).
Electrochemical Performance and Stability of Perovskite Structured Anode Materials for Intermediate Temperature-Solid Oxide Fuel Cells
Authors: Jo Su Yeon , Park Jun-Young
Published: February 2020

Solid oxide fuel cells (SOFCs) are highly promising energy conversion devices that can directly convert chemical energy in a fuel to electrical energy. Because they have numerous advantages, such as high conversion efficiency, low pollutant output, and great fuel flexibility, SOFCs have been considered as next-generation clean energy generators.

Currently the state of the art anode material for SOFCs is Ni-YSZ cermet. This materials show excellent catalytic activity and stability for the H2 oxidation of hydrogen fuel at SOFC operation conditions. However, Ni-YSZ based anode cermets have a number of drawbacks in system where hydrocarbon fuel is used, such as carbon deposition and sulfur poisoning. In addition, Ni-based anodes suffer from instability upon redox cycling due to the volume expansion of the anode by the Ni oxidation to NiO. This drawbacks of Ni-YSZ cermet significantly may reduces the SOFC lifetime.

To overcome these drawbacks of Ni-YSZ based anode, we investigate Ni-free ceramic oxide material as alternative anodes. Developments of Ni-free anode, such as ceria, titanate and lanthanum chromite-based oxides, are required to meet various properties such as high electrochemical performances, tolerance to formation of carbon coking, thermal and redox stability. Among these materials, perovskite-structured materials have been explored to replace Ni-based cermet for SOFCs because they have high tolerance against the carbon deposition and sulfur poisoning with good electrocatalytic performances. 

In this work, hence we investigate the performance and durability of Ni-free ceramic-based anode during redox cycles of IT-SOFCs. In addition, various transition metals are doped to cramic-based oxide materials to improve electrocatalytic activity, thus resulting in improving the SOFC performance. After the durability testing of SOFCs, electrochemical properties and physicochemical properties of Ni-free ceramic anode cells are investigate by using various analytic techniques such as EIS, SEM, TEM, and XRD.

References

[1] K.T. Lee, E.D. Wachsman, Science 334 (2011) 935.

[2] S. Park, J.M. Vohs, R.J. Gorte, Nature 404 (2000) 265.

[3] S. Tao, J.T.S. Irvine, Nat. Mater. 2 (2003) 320.

[4] K.B. Yoo, B.H. Park, G.M. Choi, Sol. St. Ionics, 225 (2012) 104.

[5] Ahmed D. Aljaberi and John T. S. Irvine. J. Mater. Chem. A. 1 (2013) 5868.

[6] Azra Yaqub, Cristian Savaniu, Naveed K. Janjuab and John T. S. Irvine, J. Mater. Chem. A, 1 (2013) 14189

 

Keywords: anode-supported solid oxide fuel cells, degradation mechanism, Ni-free anode material, redox cycling.
Modification of Carbon Electrodes with Electrochemically-Formed Dendrimer-Encapsulated Palladium Nanoparticles from Tributylmethylammonium Bis((trifluoromethyl)Sulfonyl)Imide Ionic Liquid
Authors: Lo Nai-Chang , Chen Po-Yu , Sun I-Wen
Published: February 2020

In this study, the polyamidoamine (PAMAM) dendrimer-encapsulated metal nanoparticles-modified electrodes were prepared in a two-step electrochemical approach. First, dendrimer molecules were grafted onto carbon surfaces by electrochemical oxidation of the terminal amine groups of PAMAM dendrimer in aqueous solution[1]. Then the dendrimer-grafted electrodes were moved inside a oxygen- and moisture-free glove box and immersed in tributylmethylammonium bis((trifluoromethyl)sulfonyl)imide ionic liquid (Bu3MeN-TFSI IL)[2] containing Pd(II) ions. In the second step, the adsorbed metal ions (Pd(II)) were electrochemically reduced in a neat IL to form nanoparticles which were encapsulated by the PAMAM dendrimers grafted on the electrodes.

The modified electrodes were characterized using atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy-dispersive spectrometer (EDS). The stability and activity of the modified electrodes were studied in aqueous solution.

[1] 1.    Kim, T. H.; Choi, H. S.; Go, B. R.; Kim, J. Electrochem. Commun.
2010,
12 (Copyright (C) 2015 American Chemical Society (ACS). All Rights Reserved.), 788-791.

[2] 2.    Chen, P.-Y.; Hussey, C. L. Electrochim. Acta
2004,
49 (Copyright (C) 2015 American Chemical Society (ACS). All Rights Reserved.), 5125-5138.
The Effect of Catalyst Layer Deposition Thickness on DMFC Performance Via the Drawdown Method
Authors: Glass Dean , Prakash G. K. Surya , Olah George A.
Published: February 2020

Catalyst deposition control is one of the overlooked areas of fuel cell fabrication and research that can affect the overall performance and cost of the fuel cell manufacturing.  One such method that is seldom utilized in research is the drawdown method, a form of spreading.  The effect of the different individual catalyst layer thicknesses and loadings on both the anode and cathode compartments of a direct methanol fuel cell (DMFC) was investigated separately.  The drawdown method was performed at thicknesses varying from 1 mil to 8 mils with Pt/Ru loadings on the anode ranging from 0.25 mg cm-2 to 2.0 mg cm-2 and platinum loadings in the same ranges on the cathode.  The membrane electrode assemblies (MEAs) with thicker individual layers (8 mil and 4 mil) performed better than the ones prepared with thinner individual layers (1 mil) in both the anode and cathode.  The power density maxima for the different loading levels followed an exponential decrease of platinum utilization at the higher loading levels.  The painted MEAs tended to display similar performance characteristics as the drawdown MEA layers closest to the thickness at the respective loadings, showing an effect on the overall fuel cell performance with respect to the individual layer thicknesses.
(Invited) All-Optical Measurement of Quantum Efficiency in Luminescent Materials and Its Application to Silicon Nanocrystals
Authors: Crowe Iain F , Halsall Matthew P , Gwilliam Russell M
Published: February 2020

We present an all-optical technique for measuring the quantum efficiency (QE) of luminescent materials; and, although generally applicable, we apply it as an example to silicon nanocrystals. The concept of internal quantum efficiency (IQE) for a light emission process; the fraction of electron-hole pairs that generate photons inside a material is quite a simple one, and yet in practice this is very difficult to measure. In fact, all existing methods rely on an estimation of IQE from the externalquantum efficiency (EQE); the ratio of photons emitted to those absorbed, typically with the assumption that IQE tends to unity at low temperature. This is an over-simplification and requires further assumptions about the dielectric materials that the photons traverse.

An alternative approach was proposed earlier [1], in which both the light and heat, generated by the excitation process, are measured simultaneouslyas functions of a third variable, e.g. excitation laser power. However, experimental limitations such as reabsorption of light in the sample and recovery of a non-local thermal signal mean that only the EQE is ever really determined, albeit accurately [2].

In this contribution, we describe an all-optical (pump-probe) technique in which we balance the light leaving a local (μm-scale) region of excitation (by measuring μ-PL) with the heat generated at the focussed laser spot (by measuring changes in intensity of a near-IR reflected probe). Critically, our optical arrangement (three confocal signals in one microscope objective) combined with an advanced DSP ‘lock-in’ technique, permits measurement of ΔR/R to within 1 part in 106, corresponding to temperature changes on the mK scale. We present initial data on silicon nanocrystals, formed in glass cover-slips after ion implantation and thermal annealing, and discuss how the technique relates to a true measure of IQE with limitations and how it can be applied more generally to alternative material systems.

 References

 [1]     D J Dunstan, ‘On the measurement of absolute radiative and non-radiative recombination efficiencies in semiconductor lasers’, J. Phys. D: Appl. Phys. 25 (1992) 1825 – 1828

 [2]        K R Catchpole et al, ‘High external quantum efficiency of planar semiconductor strucutres’, Semicond. Sci. Technol. 19 (2004) 1232 – 1235
(Invited) High Efficiency, Color-Tunable InGaN/GaN Nanowire Light Emitting Diode Arrays
Authors: Wang Renjie , Ra Yong-Ho , Mi Zetian
Published: February 2020

The monolithic integration of red, green and blue (RGB) light-emitting diodes (LEDs) directly on a single chip is critically important for smart lighting and full-color display applications. The resulting color-tunable LEDs can exhibit excellent color rendering capability, high efficiency, and low power consumption, compared to conventional phosphor-based white LEDs. In this context, we have investigated the molecular beam epitaxial growth, fabrication and characterization of InGaN nanowire RGB LEDs monolithically integrated on a single chip, including Si and sapphire substrate. We have achieved controllable and tunable full-color light generation from InGaN LEDs. The correlated color temperature can be continuously varied in the range of 1900 K to 6800 K, while maintaining excellent color rendering index capability (CRI > 90).

In this work, RGB InGaN/GaN dot-in-a-wire LED arrays were grown on Si using a three-step selective area growth (SAG) technique, wherein blue, green, and red-emitting LEDs were grown in sequence. In this process, a SiOx mask layer was used to protect the previously grown devices and also to precisely define the growth position of each nanowire LED pixel. Tunable PL emission across the entire visible spectral range (~450 nm to 700 nm) can be readily achieved on a single Si wafer by varying the sizes and/or compositions of the dots. By separately biasing such lateral-arranged multi-color LED subpixels, the CCT value can be varied from ~1900 K to 6800 K, while maintaining relatively high CRI values (up to ~ 90, or higher). 

We have further investigated the molecular epitaxial growth and fabrication of multi-color nanowire LED arrays on GaN template on sapphire substrate. In this process, a thin (~ 10 nm) Ti layer was utilized as the mask, and nanoscale growth patterns were defined by e-beam lithography. By controlling the nanowire diameters, multi-color emission can be achieved in a single epitaxial growth step. We have also demonstrated multi-color nanowire LEDs on sapphire substrate that can exhibit excellent current-voltage characteristics, high power operation, and reduced efficiency droop.     

In summary, we have developed tunable, full-color InGaN nanowire LED arrays on Si and sapphire substrate by using special selective area growth techniques. Through controlled light mixing at the wafer-level, we have demonstrated color-tunable light emission with an unprecedented tuning range for the CCT, from 1900 K to 6800K, while maintaining excellent CRI values. The realization of electrically injected RGB InGaN nanowire lasers is being studied and will also be reported.
(Invited) on-Chip and Silicon-Compatible Er-Doped Aluminum Oxide Lasers
Authors: Bradley Jonathan D. B. , Purnawirman Purnawirman , Shah Hosseini Ehsan , Su Zhan , Magden E. Salih , Li Nanxi , Singh Gurpreet , Sun Jie , Adam Thomas N. , Leake Gerald , Coolbaugh Douglas , Watts Michael R.
Published: February 2020

Erbium-doped lasers provide high power, narrow linewidth and thermally stable emission in the important 1.5-µm eye-safe and telecommunications band. By integrating such lasers on a chip we can realize cost-effective, compact and highly robust devices compared to fiber-based platforms. Furthermore, using a silicon-compatible fabrication approach allows for co-integration with silicon electronic/photonic devices and will open new applications for compact microsystems.

The presentation will cover our work on silicon-based erbium-doped aluminum oxide lasers (Al2O3:Er3+). Al2O3:Er3+  has recently received significant attention because of its broad emission, reduced clustering, and higher index, thus potential for more compact devices, compared to Er-doped silica. This has led to numerous demonstrations of amplification and lasing on chips using Al2O3:Er3+ as monolithic gain medium. As an important step towards silicon compatibility and exploiting wafer-scale lithography methods for high resolution cavity features, we have developed a silicon nitride-based Al2O3:Er3+ platform. Using such an approach, we have demonstrated a number of on-chip lasers, including distributed feedback, distributed Bragg reflector and microcavity devices. The talk will cover critical materials and design considerations towards realizing high performance lasers, including the influence of ion-ion clustering in the Al2O3 host, nanoscale film-thickness non-uniformities, and cavity Q factor optimization.
Development of Practical Sodium-Ion Batteries Using Amide Ionic Liquids: High Energy Efficiency, Excellent Cycleability and Wide Temperature Range Operation
Authors: Nohira Toshiyuki , Hagiwara Rika , Matsumoto Kazuhiko , Ding Changsheng , Fukunaga Atsushi , Sakai Shoichiro , Nitta Koji
Published: February 2020

Over five years, we have been conducting R&D of sodium secondary batteries using amide ionic liquids as electrolytes. The new batteries intrinsically have high safety due to the nonflammability and nonvolatility of ionic liquids. Moreover, they can be operated in a wide temperature range of 273-363 K. We found that several types of FSA-based (FSA: bis(fluorosulfonyl)amide) ionic liquids exhibit superior properties for the application to sodium secondary batteries.

In the present paper, we first investigated the fundamental electrolyte properties for the binary Na[FSA]-[C3C1pyrr][FSA] (C3C1pyrr: N-methyl-N-propylpyrrolidinium) ionic liquid system. Then, NaCrO2 and hard carbon (HC) were selected as positive electrode and negative electrode active materials, respectively, and their fundamental charge–discharge characteristics were examined with coin-type half-cells. A 1.5 mAh coin-type full cell composed of HC/NaCrO2 exhibited excellent cycle properties, maintaining 90% of its initial capacity after 1000 cycles at 333 and 363 K. On the basis of these results, the 1.5 mAh full cell was fabricated and its performance was tested. It showed a high charge–discharge energy efficiency of 97.5% at 363 K and C/5 rate. Finally, we constructed a large-sized prismatic HC/NaCrO2full cell with a capacity of 27 Ah by a mass production process. We confirmed that its performance is comparable with that of the 1.5 mAh coin-type cell.

Acknowledgements

This study was partly supported by Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST) and the Japanese Ministry of Education Culture, Sports, Science and Technology (MEXT) program “Elements Strategy Initiative to Form Core Research Center” (since 2012).
(Invited) The Power Flow Coloring: Concept and Implementation Methods
Authors: Matsuyama T. , Javaid S.
Published: February 2020

In order to develop sophisticated systems with diverse components and versatile functions, it is a crucial and fundamental requirement to give a unique ID to each basic entity such as IP addresses in the Internet, social security numbers in welfare and health care systems etc.

This paper first introduce the concept of the power flow coloring, which gives a unique ID to each power flow between a specific power source and a specific power load.

Since the concept of the power flow coloring is attractive, there have been proposed several implementation methods that can be classified into three categories:

1. Power Line Switching

2. Power Routing (Store and Forward)

3. Synchronized Terminal Control

This paper gives an overview of these implementation methods and then describes our Peer-to-Peer cooperative distributed control method with several real world experimental results.