bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Conducting Ni-Co Spinel Oxide Thin Film for Solar or Photoelectrochemical Cell Applications
Authors: Tsai Shu-Yi , Fung Kuan-Zong , Ni Chung-Ta
Published: February 2020

Nickel oxide and cobalt oxide may crystallize in a rock salt structure or a spinel structure depending upon the heating temperatures. A rock-salt solid solution is usually observed at temperature higher than 500°C. On the other hand, the spinel structure is preferred at lower temperature. The Ni/Co oxide spinel tends to adopt the inverse-spinel arrangement with the tetrahedral sites completely occupied by Co+3 since the ionic radius of Ni+2 is much larger than that of Co+3. In this study, Ni/Co oxide spinel nanopowder was obtained by wet-chemical method. The crystal structure and morphology of Ni/Co oxide powders were examined using XRD and TEM.

NiCo2O4 spinel may be used as a bifunctional catalyst for oxygen evolution and reduction reaction as electrode in both inorganic and organic electrosyntheses. Recently, NiCo2O4 spinel was found to be an infrared transparent conducting material with potential forsolar or photoelectrochemical cell applications. For these applications, NiCo2O4obtained in thin film form is preferred.

By using rf magnetron sputtering technique, a NiCo2O4 solid film was deposited on a glass substrate from a sintered oxide target with the same composition. With annealing at adequate temperature, a thin film of nickel-cobalt oxides showing spinel structure was obtained. The electrical property of spinel film was measured using 4-probe technique. A resistivity as low as 10-2~10-1ohm/cm was obtained. The optical property of this spinel was also measured as a function of thickness/deposition time in the wavelength range of infrared radiation. The morphology and nano/microstructure of deposited and annealed films were examined using high resolution SEM.
Creation of High-Density Nanostructures for Use in Energy Conversion Applications
Authors: Wong Justin C. , Xu Cheng , Ziegler Kirk J
Published: February 2020

Nanostructures have garnered much interest in recent years for their potential in increasing performance of alternative energy devices, such as solar cells, thermoelectrics, batteries, and piezoelectrics.  Many methods exist for the fabrication of nanostructures, but one of the most promising methods is the use of nanoporous aluminum oxide templates due to its extremely high density and self-ordering through a hexagonal, close-packed structure.  However, the initial aluminum growth substrate is generally not suitable for use in energy conversion devices so a major challenge becomes the practical use of aluminum oxide templates.  In this presentation, we demonstrate how to effectively utilize the unique advantages of aluminum oxide templates for a variety of applications.  We introduce a method to transfer aluminum oxide templates to a substrate of interest.  Using this process, we are able to pattern highly-ordered nanostructured materials with dimensions below 10 nm that may be suitable for use in thermoelectric devices.  We also use this pattern transfer process to fabricate porous templates on complex multilayered substrates. These multilayered nanostructures can be used in many applications. Here, we present the growth of highly-ordered, catalyzed carbon nanotubes.  These methods highlight an effective approach for creating the highly-dense, highly-ordered nanostructures required for many energy conversion applications.
(Invited) Adventures in Si Nanocrystal Surface Chemistry....Controlling Optical Properties and so Much More
Authors: Veinot Jonathan
Published: February 2020

Silicon nanocrystals (SiNCs) have been attracting attention as active materials in a variety of proto-type devices including, solar cells, light-emitting diodes, and photodetectors.  These, and other device structures require well-defined materials with predictable properties.  Traditionally SiNC surfaces are rendered processable and stable toward oxidation by employing a variations of the general hydrosilylation reaction; they all involve the addition of a silicon-hydride bond in the SiNC surface across a carbon-carbon double (or triple) bond and affords a “monolayer” attached through a robust silicon-carbon linkage. Recently, it has come to light that typical hydrosilylation conditions can afford insulating multilayers that can render SiNCs electrically inactive.  This finding led us to explore alternative functionalization protocols.  In doing so, we discovered that surface chemistry provides another degree of freedom with which SiNC properties may be tailored.  For example, it can be used to tailor the photoluminescent response throughout the visible spectrum, used to prepare SiNC/polymer hybrids, and even induce reactivity that provides polymerization of workhorse electronic polymers without the use of expensive transition metal catalysts.  This presentation will include a discussion of our recent exploration into SiNC surface chemistry, new reactive platforms that have opened the door to new functional materials, and what our discoveries mean for the future of these fascinating materials.
(Invited) Silicon-Based Nano-Composites Made from All-Inorganic Colloidal Silicon Nanocrystals
Authors: Fujii Minoru
Published: February 2020

Silicon (Si) nanocrystals have been a subject of intensive research for many years as nanoscale luminescence materials. In particular, the research on colloidal form Si nanocrystals are growing rapidly in recent years, because of the versatility in many kinds of applications. Recently, we have developed a new type of all-inorganic Si nanocrystals that can be dispersed in alcohol and water almost perfectly without any surface functionalization processes. The unique property arises from the core-shell structure. The shell is very heavily boron (B) and phosphorus (P) doped crystalline Si, which induces negative potential on the surface and prevents the agglomeration in polar solvents. The B and P codoped Si nanocrystals have several characteristic properties not being observed in usual Si nanocrystals. Among them, an important feature is the insensitiveness of the luminescence property to environment and to chemical treatment of the surface. Because of the insensitiveness, the codoped Si nanocrystals are a very suitable material for the production of a variety of Si nanocrystal-based nanocomposites. In this work, we first discuss structural and optical properties of B and P codoped colloidal Si nanocrystals, and then show the luminescence properties of dense solids made from the colloidal Si nanocrystals. We discuss the effects of the dielectric environment and the energy transfer between nanocrystals on the luminescence properties of Si nanocrystal solids. We also produce composite nanopartciles consisting of codoped Si nanocrystals and gold (Au) nanoparticles or nanorods. We demonstrate the enhancement of the radiative decay rate and quantum yield of Si nanocrystals by tuning the surface plasmon (SP) resonance energy to the luminescence energy. We also show the excitation cross-section enhancement, when the SP resonance energy coincides with the excitation energy.
Renewable Hydrogen: Near Term Solutions and Long Term Potential
Authors: Ayers Katherine E
Published: February 2020

Renewable hydrogen is becoming an increasingly important component of the transition away from fossil fuel use and towads reduction in carbon dioxide production.  Hydrogen is the intermediary between primary energy sources and end products in many chemical processes such as ammonia generation, refining, and biogas processing, and is currently mainly produced by reforming of natural gas.  Hydrogen from electrolysis can both make a strong environmental impact on these industries and also improve utilization of intermittent renewable energy sources such as wind and solar by leveraging otherwise stranded resources.  Because of hydrogen's end use flexibility, electrolysis is a key component of Europe's strategy for energy storage and management of these renewable energy sources on the electrical grid.  Proton exchange membrane (PEM) electrolysis is especially well suited to energy capture because of the dynamic range and ability to quickly ramp up and down from near zero output to full capacity.

PEM electrolysis technology development has lagged behind PEM fuel cells, providing significant opportunities for continued improvements.  Thinner membranes, reduced PGM usage, and improved manufacturing techniques have all demonstrated viability for electrolysis, and have the potential to make higher cost and performance impact.  At the same time, the basic technology is mature and has been scaled to multi-megawatt capacity.  This talk will discuss the challenges in continued scale up, as well as some of recent advancements and impact on cost.  A potential roadmap for next generation technology evolution will also be presented.

There has also been significant interest in alkaline exchange membranes and ionomers (AEMs) for electrolysis applications.  The AEMs are growing in stability, and electrolysis offers an alternative outlet for these materials which has operational advantages vs. the fuel cell.  While electrolysis occurs at higher voltages and higher pressure, there are other operational characteristics which are less challenging than the AEM fuel cell application, such as water management within the membrane and through the cell.  A comparison of traditional liquid alkaline, PEM electrolysis, and the potential for AEM electrolysis will be discussed.
Grand Challenge: Attaining the Limits of Intercalation Reactions
Authors: Whittingham M. Stanley
Published: February 2020

Since the introduction of intercalation cathodes in the 1970s the energy stored has not significantly increased above 600 Wh per kg of active material [1]. Although conversion reactions can lead to higher initial capacities, there is still no convincing experimental evidence that batteries based on such reactions have energy efficiencies close to approaching the 90% of intercalation systems for hundreds of cycles. Thus there is a need to improve the energy stored in cells in intercalation based reactions above the around 20% of the theoretical value. Two possible approaches will be described: attaining 2 e per redox center by intercalating 2 Li (as opposed to 1 Mg), and attaining closer to 1 Li cycling in the layered oxides. The latter is a challenge because the thermal instability of the oxides is directly proportional to the charging voltage, i.e. to the oxidation level of the oxygen in the lattice. One of the challenges in inserting 2 Li is the stability of the lattice over hundreds of insertions and removals; the reactions of Li with VOPO4 will be used as an example. It should be possible to attain energy densities in full cells of 350 Wh/kg and 1 kWh/liter.  This work is supported by DOE BES EFRC NECCES under award #  DE-SC0012583.

[1] Chem. Rev. 114, 11414, 2014
New Bimetal Catalysts Supported on Silica Nanospheres for the Production of Synthetic Diesel
Authors: Neira Carlos , Ortiz Dayna M. , Arango Juan C. , Márquez Francisco , de Jesús Abniel M.
Published: February 2020

Nowadays we are facing the necessity to find new ways to reduce the use of fossil fuels. This need comes from the excessive use of these sources as energy and the well-known adverse environmental effects than these fuels represents. Currently the fossil fuels represents about the 70% of the world energy sources. This dependency has brought some important problems of contamination such as global warming and climate change, acid rain, alterations of the carbon cycle, among many others.  The transportation sector is the largest consumer of petroleum-based fuels in the world, liberating to the atmosphere vast amounts of CO2, NOx, SOx, lead (Pb), mercury (Hg), and many others. These pollutants are not only harmful to the environment but also to the human health, causing lung and heart diseases along with cancer. The increase of price and demand of these fuels and the contamination generated by them makes imperative the search of viable clean technologies looking for the production of clean fuels with high commercial value. Contaminants produced by the combustion of fossil fuels represent a challenging future for the development of new clean fuels. In this regard, an interesting alternative consists in the synthesis of clean diesel fuel thorough the Fischer-Tropsch (FT) reaction. This method produces clean diesel starting from a mixture of H2 and CO obtained from renewable or not renewable energy sources. This synthesis produces high weighted hydrocarbons with high purity. The fuel produced by this process is clean since it does not have aromatic compounds or sulphur or nitrogen-based compounds, preventing the production and release of NOx and SOx during combustion. The FT processes require the use of heterogeneous catalysts. These catalysts are based on active metals (i.e. Co, Ru or Fe) highly dispersed on the surface of appropriate supports. In this research SiO2 nanospheres, synthesized by using the Stӧber procedure, have been used as supports for the deposition of different metals on the surface.  The synthesized catalysts were characterized by FE-SEM, HRTEM, XRD and BET, and used for the FT reaction. Preliminary catalytic results are very promising and show that mixtures of low loadings of bimetal nanoparticles dispersed on the surface of SiO2 nanospheres could be efficiently used for the synthesis of paraffin products with different distribution.
(Invited) Beyond Vapor Compression Technologies
Authors: Bouza Antonio M
Published: February 2020

The Building Technologies Office (BTO) of the U.S. Department of Energy (DOE) seeks to accelerate the development of the next generation of heating, ventilation, and air-conditioning (HVAC) technologies, including both electric- and natural-gas-driven solutions. HVAC is the largest energy end-use for U.S. buildings, consuming approximately 37.3% (~15 Quads) of total energy.[1] Vapor compression based systems have effectively and efficiently served the HVAC needs for residential and commercial buildings for close to 100 years. Vapor compression technologies are currently the dominant HVAC technology due to their scalability, relatively compact size, high reliability, and other attributes. However, the refrigerants used in these systems have detrimental global effects on the environment when released into the atmosphere. The scientific community has responded to such environmental threats by several proposals to phase down refrigerants with large global warming potential (GWP).

What is needed is a paradigm shift in HVAC technologies, moving beyond today’s refrigerants and toward a future based (at least in part) on non-vapor-compression HVAC technologies with the ultimate goal to eliminate high GWP refrigerants all together. This new paradigm is the ultimate environmental solution (zero GWP cooling fluids), provides energy savings for consumers, and will enable manufactures to avoid the challenge of future refrigerant change out cycles.  A primary objective is to focus on an end-state with no refrigerants required, while enabling U.S. manufacturers to innovate in ways that will enhance their competitiveness over the longer term.

What comes after vapor compression technology? U.S. Department of Energy has recently completed a report on the Energy Savings Potential and RD&D Opportunities for Non-Vapor-Compression HVAC Technologies to help frame the state of these next generation technologies. Possible candidate technologies include, but are not limited to: sorption technologies, alternative thermodynamic cycles, solid state technologies, membrane technologies,
electrochemical cycles
, and mechanical technologies. BTO currently has several projects that use electrochemical cycles in its HVAC, Water Heating and Appliance R&D portfolio.

[1] http://buildingsdatabook.eren.doe.gov/
(Invited) The Electrochemical Interface at the Atomic Scale
Authors: Rossmeisl Jan
Published: February 2020

There are presently no atomic scale simulations or analysis that capture all the essential parts of the nature electrochemical interface. Thus the electrochemical solid/liquid interface represents one of the frontiers of atomic scale simulations. The electrolyte is as important for the fundamental properties of the interface as the surface. The challenge is to model the effect of and interplay between potential, pH and ion strength. Thus far these effects have not correctly been accounted for. However, based on a thermochemical analysis it is now possible to account for the effect of pH and ions in the electrolyte on the atomic structure of the interface.
(Invited) Predicting Electrocatalytic Properties: Modeling Structure-Activity Relationships of Nitroxyl Radicals
Authors: Hickey David P , Schiedler David , Matanovic Ivana , Doan Phuong Vy , Atanassov Plamen , Minteer Shelley D. , Sigman Matthew S
Published: February 2020

Recently there has been an increased interest in the development of small molecule electrooxidation catalysts such as (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), for use in the anodic compartment of a biofuel cell. Some TEMPO derivatives are capable of electrochemically oxidizing short chain alcohols and various sugars to the corresponding aldehydes and carboxylic acids under physiological aqueous conditions. However, building libraries of such a catalyst is difficult due to the limited number of commercially available TEMPO derivatives and the lack of modular synthetic pathways to more complicated TEMPO structures. A promising alternative to the physical preparation of such libraries is the use of computational modeling to allow for in silico catalytic screening of a much wider range of TEMPO compounds.

Based on experimental results, we have developed a computational model to probe the structure-function relationships that determine the catalytic activity of a diverse range of water-soluble nitroxyl radical compounds. A strong correlation was found between the difference in the electrochemical oxidation potentials of a compound and its electrocatalytic activity. The newly developed computational model is able to accurately predict the electrochemical potential and catalytic activity of a wide range of nitroxyl radical derivatives.
Identifying the Electrochemical Conditions of Underpotential Deposition and Its Role in Shape-Controlled Synthesis from First Principles
Authors: Weitzner Stephen , Dabo Ismaila
Published: February 2020

Recently, much attention has been devoted to the development of synthetic approaches that can exert facile control over the size, shape, architecture and composition of transition metal nanoparticles (TMNPs).  The advent of such approaches could enable the rational design of nanoelectrocatalysts, as the catalytic properties of TMNPs are highly sensitive to their morphologies and elemental compositions.  One strategy that is actively being investigated involves the underpotential deposition (UPD) of transition metals onto the surfaces of seed TMNPs.  UPD-based approaches for shape control are attractive since the deposition process is surface-sensitive and is easily controlled by varying the synthesis conditions, such as the transition metal salt concentration and the pH of the electrolyte.  Nevertheless, the ability to predict the equilibrium shape of UPD-modified TMNPs is challenging because of difficulties in modeling the UPD process in electrolytic media.  Therefore, in order to develop a strong connection between the synthesis conditions and the equilibrium shapes of UPD-modified TMNPs, better theoretical descriptions of UPD phenomena are required. In this work, we report progress on the first-principles modeling of UPD phenomena under realistic electrochemical conditions.  Key to this model is the ability to include the influence of solvent dipoles and the electrical double layer along the solid–liquid interface. We capture these effects through a recently released solid–solution interface model.  Employing this approach, we are able to accurately calculate the measurable shift in redox potential associated with the UPD process on planar surfaces, as well as the adsorption isotherms including entropic effects.  The development of this predictive first-principles UPD model and extensions to modeling equilibrium TMNP shapes are discussed.
The Influence of Coupled Faradaic and Charging Currents on Impedance Spectroscopy
Authors: Wu Shao-Ling , Orazem Mark E. , Tribollet Bernard , Vivier Vincent
Published: February 2020

Passage of current in electrochemical systems can be attributed to faradaic reactions and to double-layer charging. Faradaic and charging currents are usually considered separately when developing models for the impedance response [1]. Delahay [2] criticized the assumption that charging and faradaic currents are uncoupled on the grounds that part of the flux of reacting species must contribute to the charging of the interface as well as to the faradaic reaction. Nevertheless, the accepted procedure for model development has been to assume that the faradaic and charging currents are independent.

When charging and faradaic currents are considered uncoupled, the flux of reacting species contributes only to the faradaic reaction. Under the assumption that charging and faradaic currents are coupled, the reacting species are seen to contribute to both the faradaic reaction and, along with the inert species, to the charging current.

Relaxation of the assumption that faradaic and charging currents are independent requires coupling an explicit model of the double layer to the convective diffusion equations for each ionic species. Nisancioglu and Newman [3] provided an appropriate mathematical formalism, used by Wu et al.[4] to model the impedance response of a rotating disk electrode.

Through numerical simulation, the coupling of faradaic and charging currents is shown to result in impedance responses yielding frequency dispersion that resembles Constant-Phase-Element (CPE) behavior. The results show that coupling of faradaic and charging currents should be considered when modeling the impedance response for systems influenced by mass transfer, even for large concentrations of supporting electrolyte. Features of the simulations are compared to the results of experiment.

References

J. H. Sluyters, Recl. Trav.
Chim. Pays-Bas,
79 (1960), 1092-1100.

P. Delahay, J. Phys. Chem.,
70 (1966), 2373-2379.

K. Nisancioglu and J. S. Newman, J. Electrochem. Soc., 159 (2012), E59-E61.

S.-L. Wu, M. E. Orazem, B. Tribollet, and V. Vivier, Electrochim. Acta,
131 (2014), 3-12.
Phase-Field Modeling of Metal Plating on Battery Electrodes
Authors: Fang Alta , Haataja Mikko
Published: February 2020

The growth of ramified metal deposits on battery electrodes during charging can lead to capacity loss as pieces of metal become electrically disconnected upon cycling or result in battery failure as metal dendrites penetrate the separator and short-circuit the cell. This undesirable metal plating can occur in Li-ion batteries under conditions of fast charging, overcharging, low temperature, or in the presence of battery separator defects. Nonuniform electrodeposition is also a challenge faced by next-generation battery technologies with pure metal anodes. Developing a better understanding of how different electrodeposit morphologies form inside batteries could lead to more effective strategies for preventing dendrite growth, making Li-ion batteries safer and metal anodes more practical.

Phase-field modeling is a promising approach for modeling electrodeposition morphologies and has been used extensively to simulate a variety of complex microstructural evolution processes. We have developed a phase-field model of electrodeposition from a binary electrolyte that accounts for Butler-Volmer reaction kinetics, the metal-electrolyte surface energy, and ion transport via diffusion and migration. We validate our model with linear stability analyses and numerically simulate the formation of various morphologies under different conditions. In addition, we simulate dendrite growth through a porous battery separator and explore the effects of separator properties on the growth of the metal electrodeposits.
High Capacity and High Power Ncm/Graphite Lithium Ion Battery Using Microgrid® Expanded Metal Current Collectors
Authors: Zhang Zhifeng , Chen Zhenlian , Zhang Xianhui , Li Yantu , Zhang Qinggang , Hart John , Li Jun
Published: February 2020

To achieve better sustainable power application of LiNi1/3Co1/3Mn1/3O2/graphite lithium ion battery, new cell structures using Microgrid® expanded metal current collectors were studied. By adopting the Microgrid® foil for cathode electrodes, the performance of LiNi1/3Co1/3Mn1/3O2 electrodes was significantly improved at high rate discharge at both room and low temperature. Scanning electron microscopy was carried out to reveal coating features of Microgrid® cathode electrodes. The loading density of active materials can be increased by the pore structure, and the 10C capacity retention of Microgrid® electrode is 25.8% higher than that of a conventional electrode after 100 cycles, and nearly doubled for the initial discharge at 10°C. There is the potential for enhancement of cell performance using Microgrid® foils in place of conventional foils with LiNi1/3Co1/3Mn1/3O2 cathode and graphite anode. The Microgrid® full cell shows 209.0% increase of capacity with respect to conventional cells of Al and Cu foils for 10C after 100 cycles and keeps the retention rate 12% higher than the latter.  Microgrid® foils can potentially be applied to other electrode materials which are suffering from capacity fade at high C-rates and at higher loading densities.

Figure 1
Desulfation and Cycle-Life Improvement of Lead-Antimony Alloyed Lead-Acid Batteries through Periodic Inverse-Charging
Authors: Spanos Constantine , Jayan Aditya , Berlinger Sarah , West Alan C
Published: February 2020

Flooded lead-acid batteries of lead-antimony (Pb-Sb) positive grid alloy construction were continuously cycled and periodically subjected to overcharging and inverse charging as desulfation strategies. Traditional prolonged overcharging techniques were demonstrated to be inadequate at appreciably regenerating battery capacities, providing only marginal increases. On the other hand, inverse charging was shown to be highly successful on all batteries independent of state-of-health. Batteries with poor states-of-health (discharge capacities <15% of initial values) experienced almost perfect discharge capacity restoration post- inverse charging. XRD and BET investigations indicate that large sulfate crystals are selectively converted back to sponge lead metal at the completion of the process, coupled with increases in electrode surface area. Battery direct-current impedance measurements likewise indicate that inverse charging reduced internal resistance. Active material shedding was determined to be the failure mechanism during post-mortem examinations. Positive electrode shedding occurred during regular cycling and overcharging. Inverse charging was seen to promote active material shedding of the negative electrode due to electrode expansion when laterally unrestrained. Negative electrode shedding rates were negligible when restrained. Inverse charging was seen to have only a minor influence on the shedding rate of the positive.
Organic Vs. Inorganic Cations of Alkali-Metal Halides Containing Ionic Liquids for Sodium-Ion Battery Applications
Authors: Tucker Telpriore Gregory , Angell Charles Austen
Published: February 2020

The power generation from either fossil fuels or preferably renewable energy sources is on the rise throughout the world.  The pursuit of electrochemical devices for energy storage during peak power grid utilization is viable.  There is great interest in further developing sodium batteries, particularly ZEBRA-type cells with chloroaluminate electrolytes.  This lab has worked on understanding of weak-field, low-melting metal-halide based ionic liquids for use in the sodium-ion conducting batteries at a low-temperature of operation.  This undertaking employed both organic and inorganic cations of low charge density, including the much-studied dialkylimidazolium cation.  The vital issue of decreased ionic conductivity caused by alkali ion-trapping in these electrolytes long known as a qualitative effect was recently quantified, discussed, and reported by us.  We have since compared the conductivities of binary bromoaluminates in which large inorganic cations PBr4
+ formed by a bromide transfer process were used to replace the former dialkylimidazolium cation and here show the differences in the figure below. Currently, the electrochemical (along with other physical) properties are being characterized in preparations for testing in ZEBRA-type cells.  This study leads to improved understanding of the factors determining electrolyte and electrochemical performance of sodium-containing binary electrolytes over a range of temperatures.  

Figure: The top set of three conductivity isotherms are for [EMIM]AlCl4 - NaAlCl4 solutions, and the bottom set of three are for PBr4Al2Br7 - NaAl2Br7 solutions of  varying molar fractions. The completely inorganic electrolyte requires 100oC (top blue line isotherm) to attain the ionic conductivity of the electrolyte containing the organic cation at 60oC (mid black line isotherm). We attribute the difference to incomplete bromide transfer in the formation of the large inorganic cation of the second system. The “alkali cation-trapping” effect probably remains in effect.

Figure 1
(Invited) A Highly Durable Polymer Electrolyte Fuel Cell Catalyst Based on Double-Polymer-Coated Carbon Nanotubes
Authors: Nakashima Naotoshi , Fujigaya Tsuyohiko
Published: February 2020

We report the design and fabrication of a highly durable fuel cell electrocatalyst based on double-polymer-coated carbon nanotubes for use in polymer electrolyte membrane fuel cells. The prepared FC catalyst is composed of Pt-deposited polybenzimidazole-coated carbon nanotubes, which are further coated with Nafion. We fabricated MEA using the catalyst and examined the FC performance. By using this electrocatalyst, a high FC performance with a power density of 375 mW/cm2 (at 70˚C, 50% relative humidity using air (cathode)/H2(anode)) was obtained, and a remarkable durability of 500,000 accelerated potential cycles was recorded with only a 5%-loss of the initial FC potential and 20%-loss of the maximum power density, which were far superior properties compared to those of the MEAs prepared using carbon black in place of the carbon nanotubes. The present study indicates that the prepared highly durable fuel cell electrocatalyst is a promising material for the next generation of PEMFCs.
Activated Fullerene Nanostructures As High-Performance Supercapacitors
Authors: Lu Xing
Published: February 2020

Assembly of the 0-dimensional fullerene molecules into well-organized micro/nanostructures is an effective strategy for realizing their applications. In this presentation, the synthesis of various nanomaterials and their applications in electrophotonics, energy storage, and energy coversion have been reported, with a representative example as supercapacitors.
Graphdiyne for High Capacity and Long-Life Lithium Storage
Authors: Huang Changshui
Published: February 2020

Although the Li capacity can be improved greatly with these different dimensionalities and morphologies, the nature of the Li-intercalated layer does not change significantly when compared to graphite. Graphdiyne (GDY) is a new carbon allotrope that was only synthesized recently. GDY is composed of sp2- and sp-hybridized carbon atoms and is predicted to be the most stable of the various diacetylenic non-natural carbon allotropes. Here, we will report the application of GDY as high efficiency lithium storage materials and elucidate the method of lithium storage in multilayer GDY. Lithium-ion batteries featuring GDY-based electrode exhibit excellent electrochemical performance, including high specific capacities, outstanding rate performances, and a long cycle lives. We obtained reversible capacities of up to 520 mAh/g after 400 cycles at a current density of 500 mA/g. At an even higher current density of 2 A/g, cells incorporating GDY-based electrodes retained a high specific capacity of 420mAh/g after 1000 cycles. We hope that designing and preparing novel carbon-based materials with large pores will open up new approaches for the development of Li storage materials exhibiting high capacities and excellent cycling stabilities, thereby satisfying the future requirements of next-generation Li storage batteries.
Optimum Alloying of Bimetallic Platinum-Gold Nanoparticles Used As an Efficient and Robust Counter Electrode Material of Dye-Sensitized Solar Cells
Authors: Kim Ji-Soo , Dao Van-Duong , Larina Liudmila L. , Choi Ho-Suk
Published: February 2020

This study reports on the synthesis of bimetallic PtAu nanoparticles (NPs) on the transparent conducting oxide electrode by using dry plasma reduction under atmospheric pressure without using any toxic chemicals and at a low temperature, which are first employed as counter electrodes (CEs) for efficient dye-sensitized solar cells (DSCs). High resolution scanning electron microscopy (HRSEM) and x-ray photoelectron spectroscopy (XPS) are utilized for analyzing the morphology and the chemical composition of bimetallic PtAu NPs. The highest catalytic activity of the bimetallic PtAu NP CE is found through an optimization of the volume ratio of Au and Pt precursors used for synthesis of NPs. As a result, the highest electrocatalytic performance, which corresponds to the lowest charge transfer resistance of 0.88 Ω, is obtained at the Au and Pt precursor molar ratio of 1. The DSC employing Pt0.5Au0.5 alloy CE achieved a maximum efficiency of 8.0% among all cells under study. The efficiency is higher than those of 7.4%, and 0.1% for Pt NPs and Au NPs – based DSCs, respectively. The obtained results establish a base for the potential use of PtAu alloy CEs in efficient and robust DSCs.
Raman Imaging of Cells Using Antibody-Derived Carbon Nanotubes Nanoprobes
Authors: Nascimento Rafaella Oliveira , Tang Nathalie , Allard Charlotte , Nguyen Minh , Birlea Mirela , Gaboury Louis , Martel Richard
Published: February 2020

Microscopy of biological samples with fluorescent dyes exhibits strong signals, but also limitations such as photobleaching, poor long-term stability and low multicolour capabilities. In contrast, Raman imaging of molecules is better adapted for multiplexing, but its intrinsic signal is too weak to be useful for high resolution imaging. To compensate for the low sensitivity of Raman, contrast agents (probes) have been developed over the years to boost the Raman signal to levels near that of fluorescence. By encapsulating dyes inside single-walled carbon nanotubes (dyes@SWCNTs), our group has highlighted interesting optical properties that make them suitable as Raman nanoprobes  [1]. Not only these probes show giant Raman signal from the dyes, but they are resistant also to photobleaching and offer multiplexing capabilities as well as versatile chemistry at their surfaces. Recently we show that PEGylated dyes@SWCNTs can indeed be used as nanoprobes having good Raman multiplexing properties for biological imaging [2]. Here, we will present recent results on their covalent functionalization with bifunctional polyethylene-glycols (NH2-PEG-R). A full physicochemical characterization of the probes carried out using TGA, Raman spectroscopy, AFM and 1H NMR will be presented. The covalent functionalization of these Dyes@PEGylated-SWCNTs nanoprobes with antibodies was developed to produce active targeting agents for cells. Using Raman hyperspectral imaging, we have demonstrated that these antibody-functionalized nanoprobes can effectively target living or fixed human and mouse cancer cells and that they can selectively attach, depending on the antibody, to specific targets immobilized on surfaces.      

[1]      E. Gaufrès, N.Y.-W. Tang, F. Lapointe, J. Cabana, M.-A. Nadon, N. Cottenye, et al., Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging, Nat. Photonics. 8 (2013) 72–78. doi:10.1038/nphoton.2013.309.

[2]      N. Cottenye, N.Y.-W. Tang, E. Gaufrès, A. Leduc, J. Barbeau, R. Martel, Raman tags derived from dyes encapsulated inside carbon nanotubes for Raman imaging of biological samples, Phys. Status Solidi. 211 (2014) 2790–2794. doi:10.1002/pssa.201431401.

[3]      This work was made possible because of financial support from NSERC (Canada) and Photon Etc.
Biomarker Detection By Single-Walled Carbon Nanotube Optical Bandgap Modulation
Authors: Williams Ryan M. , Lee Christopher , Galassi Thomas Vito , Harvey Jackson , Sirenko Maria , Shah Janki , Heller Daniel A
Published: February 2020

The unique optical properties of single-walled carbon nanotubes (SWCNT) confer ideal sensing properties for biological applications. SWCNT near-infrared photoluminescence exhibits photostability, penetration through biological media, and environmental sensitivity. Nanotube emission can undergo modulation of the optical bandgap, causing a shift in emission wavelength. These characteristics allow for consistent rapid and long-term analyte detection and quantification in complex ex vivo and in vivo environments. We have employed these unique properties to develop biomarker-specific SWCNT-based sensors for translational biomedical applications.
(Invited) Carbon Nanotubes and Cellular Perturbation: Augmentation of Differentiation Dynamics in Neural Stem Cells
Authors: Jedlicka Sabrina , Pirbhai Massooma , Rotkin Slava V.
Published: February 2020

Delivery of materials, such as drug compounds or imaging agents for treatment or diagnosis of disease still presents a biomedical challenge. Nanotechnological advances have presented biomedicine with a number of agents that possess the appropriate size and chemistry to pass through the blood brain barrier. Functionalized carbon nanotubes are one such agent, which can potentially aid in drug and gene delivery to the central nervous system. In addition, carbon nanotubes have already been applied in several areas of nerve tissue engineering to probe and augment cell behavior, to label and track subcellular components, and to study the growth and organization of neural networks. Although the production of functionalized carbon nanotubes has escalated in recent years, knowledge of cellular changes associated with exposure to these materials remains unclear. Thus, it is crucial to develop an understanding of the effects and interactions that carbon nanotubes can induce in a living system.  In this study, carbon nanotubes, wrapped with either GT20 DNA or yeast tRNA were introduced to neural stem cells during proliferation and differentiation, at doses determined to be non-lethal.  At non-lethal doses, cell fate can be dramatically impacted by the carbon nanotube materials.  Depending upon the mode of exposure, the differentiation dynamics are significantly altered, leading to at least a one-fold increase in the final percent of neurons in the total population.  This increase in neuronal population is mathematically correlated to a change in the division symmetry of the dividing cells early in the differentiation process.  In addition, the results demonstrate that the irregular patterns of cell fate are due to a variety of biophysical inputs stimulated by the carbon nanotubes, including, but not limited to, cytoskeletal perturbation, focal adhesion augmentation, and subcellular localization of the nanomaterials.  Acknowledgment: NSF ECCS-1509786.
Examining the Sub-Cellular Localization of Single-Walled Carbon Nanotubes
Authors: Langenbacher Rachel E , Budhathoki-Uprety Januka , Roxbury Daniel , Jena Prakrit Vaibhav , Heller Daniel A
Published: February 2020

Single-walled carbon nanotubes have a number of properties of interest for their development as sensors and molecular probes for use in biological media. They are inherently fluorescent in the near-infrared “tissue transparent window” and do not photobleach. Multiple, optically distinct nanotube species can be used for extensive multiplexing in a single sample.  To preserve these desirable qualities while solubilizing and functionalizing the hydrophobic nanotube, we have developed non-covalent wrappings consisting of helical polycarbodiimide polymers. The polymers can be modulated to control internalization and sub-cellular localization. Assessing the localization of carbon nanotubes is of the utmost importance for their further development in biological applications.
Superconducting Properties in Tantalum Decorated Three-Dimensional Graphene and Carbon Structures
Authors: Pan Wei
Published: February 2020

Unlike a two-dimensional (2D) electron system at the interface in a heterostructure, the 2D electrons in graphene are open to environment. As a result, many studies have been carried out in examining how adsorption of metal adatoms on graphene sheet can modify its electronic properties. For example, a tunable superconducting phase transition was recently observed in a tin decorated graphene sheet. There, the non-percolating tin clusters dope the graphene sheet and induce long-range superconducting correlations. More excitingly, it was predicted that lithium decorated graphene can display a much higher superconducting transition temperature than in the superconductivity in bulk graphite intercalated by lithium atoms. Three-dimensional (3D) graphene structures, a flexible and conductive interconnected graphene network, have generated a great deal of interests in recent years. Compared to a 2D graphene sheet, surface area in a 3D graphene structure is greatly enhanced. Furthermore, 3D graphene maintains the outstanding electrical, thermal, and mechanical properties as in 2D graphene. Therefore, 3D graphene structures are expected to play an important role in flexible electronics, sensors and energy storage applications (e.g., supercapacitors, battery electrodes, and hydrogen storage).

In this talk, I will present our recent electronic transport results on superconducting properties in tantalum decorated 3D graphene and carbon structures, following pioneering work of decorating 2D graphene sheets with superconducting materials. A superconducting transition is observed in both composite thin films. The magnetoresistance at various temperatures and differential resistance dV/dI at different magnetic fields were also carried out. Moreover, an anomalously large cooling effect was observed in the differential resistance measurements in our 3D graphene - tantalum composite when the device turned superconducting.  This surprisingly large cooling effect plus the nature of flexible 3DG thin film may find promising applications in solid-state cooling.
(Invited) Nanotubes for DNA Conformation Sensing
Authors: Rotkin Slava V.
Published: February 2020

The talk is focused on applying single-wall nanotubes (SWNT) as optical reporters of DNA structure. SWNT photoluminescence (PL) was used to explore photo-physics of pi-pi* transitions in the photoexcited DNA.  The ssDNA wrapped CoMoCat SWNTs, water suspended, commonly produce a strong and stable PL under visible excitation[1]. Recently we demonstrated that under two-color excitation (visible plus UV) such a system shows rich behavior: normal double-band excitonic photogeneration resulting in UV-enhanced PL emission could be one type of response. The other behavior was found in a certain band of excitation wavelength: reversible PL quenching followed the cw-UV illumination, different from photobleaching or photochemical modification of pristine material. The explanation of this intriguing behavior was found and presented in Ref.[2].

By combination of optical spectroscopy, rate equation analysis for excited states, and semi-empirical quantum mechanical calculation the source of the PL quenching was identified to be free charge carriers introduced by the photoexcited DNA. It is known that the DNA in the course of biological evolution developed mechanisms of recovery after UV irradiation, as well as relaxation mechanisms for photoexcited states. One of those mechanisms, namely, the DNA autoionization (AI) mechanism has been detected experimentally using SWNT as a nanoscale reporter. Theoretical analysis of the effect showed existence of the AI rates shorter than 20 fs and dominated by a hole charge transfer from the ssDNA to the SWNT. The capability to detect a fundamental relaxation mechanism of UV-excited DNA by using two-color spectroscopy proves potential of a DNA-SWNT complex, as a model optical system, for detecting charge transfer from DNA. Furthermore, the model demonstrated that the AI rate is a function of the conformation of the DNA thus opening further avenues for biosensing of DNA architecture in these complexes.

Significant contributions to this work by Dr. T. Ignatova (UC Irvine), Dr. A. Balaeff (University of Central Florida), Dr. M. Zheng (NIST), Mr. M. Blades (LU), and Mr. P. Stoeckl (University of Rochester) are kindly acknowledged; special thinks to Dr. J. Fagan (NIST) for help with instrumentation. Research was partially supported by National Science Foundation (ECCS-1509786).

References:

[1] Carbon Nanotubes and Related Structures, ed. DM Guldi, N Martin.Weinheim:Wiley-VCH. (2010)

[2] T. Ignatova, A. Balaeff, M. Zheng, M. Blades, P. Stoeckl and SV. Rotkin, “Two-color spectroscopy of UV excited ssDNA complex with a single-wall nanotube probe: Fast nucleobase autoionization mechanism”, Nano Research, (2015).
(Invited) Evidence for Strong Electronic Correlations and Band-Gap Renormalization in Doped Single-Wall Carbon Nanotubes
Authors: Hertel Tobias , Hartleb Holger , Spaeth Florian , Eckstein Klaus , Achsnich Melanie , Schoeppler Friedrich
Published: February 2020

We have investigated the photophysical properties of chemically and gate-doped semiconducting single-wall carbon nanotubes (s-SWNTs). The first subband exciton oscillator strengths as obtained from a global analysis of absorption spectra are used for assessment of carrier densities and provide evidence for band-gap renormalisation (BGR) in (6,5) SWNTs. We predict that BGR of one-dimensional gate doped semiconductors is accompanied by a stepwise increase of the carrier density by Δn=32meff
b/(πℏ)
2once the electrochemical potential reaches the valence or conduction band offset with b = (0.15 ± 0.05) eV nm (meff - effective carrier mass). Moreover, we show that the width of the spectroelectrochemical window of the first subband exciton of (1.55±0.05) eV corresponds to the fundamental band gap of the undoped (6,5) SWNTs in our samples and not to the renormalized band gap of the doped system. We also compare spectral changes in gate doped with those of chemically doped SWNTs. Femtosecond time-resolved pump-probe spectroscopy of chemically doped SWNTs provides evidence of exciton-trion coupling. These observations as well as a previously unidentified absorption band emerging at high doping levels in the Pauli-blocked region of the single-particle Hartree band structure, provide clear evidence for strong electronic correlations in the optical spectra of SWNTs.