bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Separation and Purification of Astatine for Radiopharmaceutical Application
Authors: Ganesan Selvarani , O'Hara Matthew J 
Published: February 2020

The second longest lived isotope Astatine (211At: T1/2=7.5 h), is one the most promising α-emitters for targeted cancer radiotherapy. The liquid/liquid extraction method has been shown to provide good separation of 211At from bismuth metal. However, of the liquid/liquid (L/L) extraction (separation) steps [1] used in the current manual isolation procedure presents a significant challenge due to the nature of the diisopropyl ether / hydrochloric acid (DIPE/HCl) and diisopropyl ether / sodium hydroxide (DIPE/NaOH) mixtures. The present work is focused on to evaluate the feasibility of electrochemical methods in the purification of 211At. This approach will be an alternative to hydrogen astatide (H211At) wet distillation.
At the present time, Bi (III) is considered the primary contaminant from which 211At must be electrochemically purified. The initial electrochemical studies were conducted with iodine as an astatine segregate in bismuth solution. As the concentration of astatine in the original solution is much lower than micro molar levels, there are two different approaches have been adopted; (i) separation of bismuth from the original solution [Ref 1; step 4] through electrodeposition and (ii) direct extraction of iodine from the original solution [Ref 1; step 3 or 4]. Figure 1(a) shows the cyclic voltammograms (CV) for bismuth on various substrate electrodes; namely Pt, Au and glassy carbon (GC). In these, the GC substrate found to be the suitable martial than others, which could be due to surface nature of carbon. In the case second approach, initially, iodide separation was carried out without bismuth in an acidic electrolyte with various concentrations of iodide to identify the suitable substrate material and minimum separation levels. Figure 1(b) shows the model CV for iodide on Pt electrode, surprisingly iodine deposit was also observed at the working electrode. Conversely, there are no characteristic electrochemical peaks and deposits were observed for GC and Au. This study indicates iodide can be extracted with Pt electrodes and Pt catalyzes the reactions.

Acknowledgements

Financial support from the Department of Energy (DOE) is greatly acknowledged. Selvarani Ganesan is thankful for subcontract from the Pacific Northwest National Laboratory (Contract No. 244236; PI: Matthew J O'Hara).

Reference

E.R. Balkin, D.K. Hamlin, K. Gagnon, M.-K Chyan, S. Pal, S. Watanabe, and D.S. Wilbur, Appl. Sci., 3 (2013) 636-655.

Figure 1
Electrophoretic Mobility and Deposition in High Pressure High Temperature Boiler Environments
Authors: Raman Balaji , Hall Derek M. , Shulder Stephen J , Lvov Serguei N. 
Published: February 2020

Suspended magnetite [Iron (II,III) Oxide] particles in boiler water deposit on the walls and orifice plates in boilers, impeding flow and causing inefficiencies. Operating data suggests that reducing conditions and boiler water chemistries in the boiler enhances development of magnetite deposits. The inter particle interaction due to the zeta potential developed on the colloidal magnetite particles could also be a factor in deposition. In order to study the mechanism behind the deposition of suspended magnetite on stainless steel a high temperature high pressure electrophoretic deposition cell has been developed. An autoclave pressure vessel with graphite O-ring gaskets is serve as the electrophoretic deposition cell simulating the boiler conditions (300 °C and 9 MPa). Carefully prepared test solution imitating boiler water chemistries containing suspended magnetite particles are pumped in to the autoclave. The test solution is prepared in an anaerobic environment to prevent oxygen contamination. The tests simulate the boiler conditions in terms of temperature, pressure and boiler water chemistry. The experimental setup has been designed to allow the sampling of test solution to monitor the pH, dissolved oxygen level and solution potential. 304 Stainless Steel samples were placed in the autoclave to serve as the substrate for deposition. A three-electrode assembly, consisting of 304 SS substrate (working electrode), a counter electrode and a quasi-reference electrode, has been used to characterize the deposition process using in-situ Electrochemical Impedance Spectroscopy measurements. The goal is to understand the influence of boiler water chemistries on the surface charge properties of the suspension. The surface properties can be related to the stability of suspended matter, which in turn relates to the deposition of particles on the substrate. The growth of the deposits is characterized using in-situ Electrochemical Impedance Spectroscopy measurements. Post-test analysis of the steel sample was carried out using Scanning Electron Microscopy (SEM) techniques. Preliminary tests have been carried out with a test solution pH of about 9.4, controlled by adding NH4OH (All Volatile Treatment). Deposition was observed on all samples from all the tests. In-situ EIS measurements have been recorded at test conditions of 300 °C and 9 MPa over the duration of the test. The results will be significant in understanding the inter-particle interactions and electrophoretic deposition at high temperature-high pressure conditions.
(Invited) Structure Measurements for Organic Photovoltaics Manufacturing
Authors: DeLongchamp Dean M 
Published: February 2020

Organic photovoltaics (OPV) is a promising candidate technology for the low-cost fabrication of modules to harvest solar energy. Although OPV technology has significantly matured over the past few years, there remain significant challenges in addressing the gap between lab-scale devices and real manufacturing. Structure-property-performance relationships for OPV devices are still underdeveloped, and relationships based on one system are not necessarily transferrable to new, higher-performance systems. This talk will describe our efforts to develop measurements that support OPV manufacturing. Using a blade coating process as a prototype for slot-die coating, we have developed several techniques to observe the structure of OPV films in-situ as they dry. Our measurements include synchrotron-based X-ray scattering and a variety of optical methods. We use these techniques to identify the mechanisms by which formulation and processing choices influence the nanoscale structure of the films. Several OPV systems will be described including polymer/fullerene, small-molecule/fullerene, and polymer/polymer. Throughout solidification, we can follow the number of phases, their composition, and the extent of order within them. In-situ techniques provide far more information about the solidification process than can be obtained by measuring already-dried films, providing a valuable tool to guide the selection of formulation and processing parameters.
(Invited) Ultrafast Infrared Spectroscopy of Charge Generation in Organic Photovoltaic Materials
Authors: Asbury John B. 
Published: February 2020

Ultrafast infrared spectroscopy is used to examine the mechanism of charge generation in organic photovoltaic materials. We examine archetypal classes of electron acceptors in organic photovoltaic (OPV) materials and reveal how their molecular structures determine whether hot CT state dissociation can influence the dynamics and yield of photo-generated electrons and holes. Furthermore, we tune the degree of aggregation and therefore charge carrier delocalization in OPV materials and elucidate the corresponding influence on the yield of photogenerated charge carriers. The data suggest that a distribution of local molecular environments exist at donor/acceptor interfaces. Some of these are able to support greater degrees of charge delocalization and therefore more efficient dissociation CT states into independent charge carriers. Molecular structure and domain composition influence the density of interfacial sites capable of separating charge, which determines the overall quantum yield for charge generation of a given OPV material.
(Invited) Development of Printed Flexible Organic Solar Panels, Field Effect Transistors, and Logic Circuits on PET Substrates
Authors: Alem Salima , Chu Ta-Ya , Lu Jianping , Kololuoma Terho , Tao Ye 
Published: February 2020

In this talk, I will introduce the research activities on the development of printed flexible organic solar panels, field effect transistors, and pMOS based logic circuits under NRC’s Printable Electronics Flagship Program.
I will report the development of polycarbazole-based, printed organic solar panels and the application of a printable, air-stable, and annealing-free zinc oxide nanoparticle (ZnO NP) solution in the fabrication of inverted bulk heterojunction solar cells. The as-coated ZnO thin films are insoluble in organic solvents and can be directly used as an electron extraction layer in solar cells. The process is R2R compatible. Our non-encapsulated inverted solar cells are highly stable with their PCEs remaining unchanged after being stored in air for more than 50 days.
The development of inkjet-printed pMOS inverters and logic gates on flexible substrates will be also presented. The fabrication of inkjet-printed OTFTs has achieved a yield of 97%. Different types of logic gates, inverters, and ring oscillators have been successfully fabricated by using these basic pMOS devices.
(Invited) Chemical Stability and Electronic Behavior of Atomic Layer Deposited Metal Oxide Thin Films
Authors: Strandwitz Nicholas C , Bao Bo , Correa Gabriela Calinao 
Published: February 2020

Modification of semiconductor surfaces via the growth of metal oxide overlayers, particularly by atomic layer deposition (ALD), has become a topic of recent interest for surface passivation and chemical protection in semiconductor/liquid junctions. For example, in photoelectrochemical water splitting, semiconductor surfaces typically must be protected with insulating or conducting layers that are stable in the electrochemical environment. Further, ALD thin films have been used as overlayers in a variety of other environments including those relevant to batteries, corrosion protection of metals, and for water diffusion barriers. Although thermodynamic stability of a solid phase in various environments can be readily assessed, more complex phenomena such as film hydration and dynamic dissolution/precipitation can occur, dramatically impacting the efficacy of thin protective ALD films.
Motivated by this widespread interest in ALD protective layers, we have examined the chemical stability of the two of the most common ALD materials, alumina and titania, in a variety of environments. Films were deposited using thermal ALD using trimethylaluminum and tetrakis dimethylamido titanium for alumina and titania, respectively. Film thickness was then monitored after immersion in various liquid media, which included acidic, neutral and basic aqueous solutions and mercury. Surface morphology was investigated using atomic force microscopy. Our results indicate a drastic increase in stability of the ALD films after post-deposition thermal treatment. Further, for alumina films in pure water, a dramatic restructuring occurs changing film density, thickness, and morphology. Mercury contacts induce a slow increase in film thickness that is attributed to mercury oxide deposition. Finally, we report how the effective surface recombination velocities at these interfaces evolve over the course of thermal annealing and various solution treatments. These results provide important guidelines for the applicability of ALD oxides as protective/passivating films on semiconductor electrodes for applications in sensing and photoelectrochemical water splitting.
(Invited) Stabilizing Semiconductor-Solution Interfaces Via Chemically Stable but Electronically Defective Coatings
Authors: Hu Shu , Shaner Matthew , Lichterman Michael Frankston , Richter Matthias Hermann , Verlage Erik , Mayer Thomas , Brunschwig Bruce , Dapkus Paul Daniel , Lewis Nathan S. 
Published: February 2020

Recently, a photoelectrode protection strategy, which uses an amorphous “leaky” TiO2 coating to form a complex semiconductor/TiO2/Ni structure, has shown to stabilize semiconductor-solution interfaces against photoanodic corrosion. Particularly, stabilizing semiconductor-aqueous solution interfaces for water oxidation is important because water oxidation is required for all solar fuel strategies, e.g. H2 production and CO2 reduction. We show that this TiO2protection strategy has stabilized a number of 1.1 – 1.9 eV band gap light absorbers including Si, group III-V, group II-VI semiconductors, their tandem structures and wire structures for up to 2000 hours continuous water oxidation in 1 M KOH(aq). Because of this, various otherwise unstable materials can be brought back to the table again for building photoelectrochemical devices. A water splitting reactor prototype of ~10% solar-to-hydrogen efficiency was also built.
The n-doped Si/TiO2/Ni structure also operates as a high barrier height junction for solar energy conversion. To further understand the mechanism of “leaky” TiO2 protection and the role of Ni electrocatalyst overlayers, we used Si/TiO2/Ni structures as a model system to study solid-solution interfaces. TiO2 coatings of 3 – 143 nm in thickness introduce two interfaces: a TiO2/liquid interface and a TiO2/n-Si heterojunction. We have employed operando ambient-pressure X-Ray photoelectron spectroscopy (AP-XPS) to study TiO2/Ni/liquid and TiO2/liquid interfaces, and directly observed their ohmic and rectifying junction behavior, respectively. We also extensively investigated n-Si/TiO2 heterojunction interfaces by employing photoelectrochemical, solid-state electrical, and photoelectron spectroscopic techniques. The distinctive electrical behavior of n-Si/TiO2 heterojunctions will be compared with conventional semiconductor/metal and semiconductor/liquid junctions. Because electronic defect states exist in band gaps of “leaky” TiO2, their effects on the formation of n-Si/“leaky”TiO2 heterojunctions will be discussed. This interfacial study reveal several strategies for improving the performance of thin-layer protected photoelectrodes as well as for further expanding selection of “leaky” protective coatings.
Synthesis of Metal Oxides/Graphene Nanocomposites for Applications in Lithium-Ion Battery
Authors: Nan Jiaqi , Dong Hongzhou , Li Guicun , Yu Liyan , Qin Yong , Dong Lifeng 
Published: February 2020

Over the past few years, lithium-ion battery has become a research spot due to its high voltage, high energy density and long cycle life. Traditional lithium-ion batteries employed graphite as anode material. However, graphite suffers from several shortcomings, such as low specific capacity, sluggish discharge current density, and relatively low cycle life. The discovery of graphene makes it possible to improve the performance of lithium-ion batteries significantly. Graphene with excellent electrochemical performance has attracted more and more attention. Graphene is a single layer of honeycomb sp2-hybridized carbon atoms with large surface area, high electrical conductivity and high thermal conductivity.
In this report, we employed graphene and graphene-based composite material as anode materials for lithium-ion battery to improve their performance. Stannic oxide (SnO2), cobalt oxide (Co3O4), and vanadium pentoxide (V2O5) were synthesized respectively on graphene surfaces. The incorporation of metal oxides can further improve electron mobility of graphene and lithium-ion battery charge/ discharge stability. The performance of lithium-ion batteries was tested by charge-discharge experiments, and their charge-discharge current density, charge-discharge voltages, charging rate, and cycle stability were measured and discussed.
(Invited) Direct Electrodeposition of Crystalline III-V Semiconductor Films
Authors: Maldonado Stephen 
Published: February 2020

This presentation will describe our latest results on the concept of using liquid metal electrodes as platforms for direct electrodeposition of crystalline inorganic semiconductor materials at comparatively low temperatures.
Large scale production of crystalline thin films of III-V semiconductors is challenging in two ways. First, the majority of synthetic methods are energy- and resource-intensive. For example, vapor phase crystal growth techniques such as metal-organic vapor phase epitaxy and molecular beam epitaxy involve ultra-high vacuum (UHV) equipment and temperatures above 400 °C. Similarly, liquid phase epitaxy requires sustained temperatures in excess of 750 °C and pressurized furnaces. Second, these same fabrication methods can be difficult to incorporate directly into device fabrication processes. For example, high temperatures and corrosive reagents can damage delicate electronic device architectures (e.g. complementary metal-oxide-semiconductor (CMOS)) and sensitive platforms (e.g. plastics). As a result, cumbersome and costly transfer and integration steps are necessary. Electrodeposition of III-V semiconductors has been extensively investigated since electrochemistry offers precise control of (heterogeneous) reaction rates and simple process electronics and equipment (i.e. a current or potential source and a beaker). However, stoichiometry, purity, and crystallinity have proven difficult to control.
Here, experimental data will be shown for a new tactic that offers the purity and quality of aforementioned high temperature, vapor-phase syntheses with the simplicity and affordability of conventional electrodeposition. Specifically, data will be presented that illustrates the preparation of polycrystalline films of GaAs, GaSb, InAs, InSb, and alloys thereof through an electrochemical liquid-liquid-solid (ec-LLS) process. Chronoamperometic and voltammetric responses recorded during ec-LLS will be shown. Materials characterization data in the form of electron & X-ray diffraction, X-ray photoelectron & Raman spectroscopies, and optical & electron microscopies will be also be discussed. Comparisons and distinctions with other, previously demonstrated electrochemical, chemical vapor deposition, and chemical metallurgical processes will be presented. The prospects for making high quality (epitaxial) III-V films and for seemless incorporation of III-V films on sensitive device platforms through ec-LLS will be discussed.
Solid-Electrolyte Interphase (SEI) Fracture: The Coupled Mechanical-Chemical Degradation of Lithium Ion Battery
Authors: Deshpande Rutooj , Bernardi Dawn 
Published: February 2020

The coupled mechanical-chemical degradation of electrodes upon electrochemical cycling is recognized as a major challenge in lithium ion batteries. Instability of commonly employed electrolytes at the operating potentials results in solid electrolyte interphase (SEI) formation. Although, a stable SEI layer is necessary, as it passivates the electrode-electrolyte interface from further solvent decomposition, SEI formation also contributes to irreversible capacity loss. During electrochemical cycling, due to the volume changes of the electrode particles and the associated stresses within the SEI layer, the SEI layer may fracture, exposing new electrode surfaces to the electrolyte. A new SEI is formed at these newly exposed surfaces resulting in loss of active lithium inventory. We develop a mathematical model to calculate stresses and strain energy for a particleencapsulated with SEI during lithiation and delithiation. We show that, loss of capacity of a battery due to SEI fracture actually occurs during lithiation since SEI experiences high tensile stress suring electrode lithiation. We demonstrate that for slow lithiation, excess strain energy in the particle is proportional to square of State of Lithiation (SOL) swing. A corelation is developed to calculate the cell capacity loss due to SEI fracture as a function of SOL swing, and is compared with the experimental data. We found that the model fits the capacity loss data very well. This is the first physics based model which correlates SEI cracking with the cell capacity loss.
Comparison of Spatiotemporal Changes of Solid Electrolyte Interphase (SEI) Properties on Different Anodes By Scanning Electrochemical Microscopy (SECM)
Authors: Bülter Heinz , Wittstock Gunther , Peters Fabian , Schwenzel Julian , Sternad Michael , Wilkening Martin 
Published: February 2020

In our society Li ion batteries are widely used. Mainly during the first charging process the solid electrolyte interphase (SEI) between the electrode and electrolyte is formed by the decomposition of electrolyte components at the lithiated graphite. This layer is critical for the performance and safety of the Li ion batteries.[1] The aim of this study is to characterize the electron transport across the SEI, which determines the ongoing reduction of electrolyte components. Thus, understanding the electron transport across the SEI helps to improve Lithium ion batteries.
Characterization of the SEI is a challenge, because of the variety of chemically similar components and enclosed electrolyte species. Furthermore, ex situ analysis of the SEI requires separation and isolation of the SEI, which may change the content and the structure of the SEI.[2] Recently we used the feedback mode of scanning electrochemical microscopy (SECM) to investigate in situthe electron transport at the lithiated graphite (Figure).[3]
2,5-di-tert-butyl-1,4-dimethoxy benzene was identified as an useful SECM mediator providing sufficient stability and sensitivity to study passivation properties of the SEI. Our results by SECM show gradual and significant short-term spatiotemporal changes of the SEI properties and demonstrate the dynamic and spontaneous behavior of SEI formation, damage and reformation under open circuit conditions above lithiated graphite anodes. The results emphasize that spatiotemporalchanges of the passivating SEI properties are highly localized and occur preferentially in between the gaps of graphite particles. A HOPG model electrode shows significant differences to a graphite composite electrode, indicating the impact of stressed graphite particles on the SEI stability. In addition, imaging experiments show the formation, detachment and reformation of gas bubbles.
The outcome of significant short-term spatiotemporalchanges of the SEI properties clarifies that electrolyte reduction still occurs after SEI formation at localized spots. All measurements were conducted under open circuit conditions and thus the charging state remained constant. Further research using this methodology focuses on Li and Si electrodes.
H.B. thanks the Lower Saxony Ministry of Science and Art for funding within the Graduate Program GEENI - Graduate school of electromobility and energy Storage in Lower Saxony. M.S. and M. W. gratefully acknowledge the provision of anode substrates by Infineon Technologies Austria AG.
References
[1] S. Krueger, R. Kloepsch, J. Li, S. Nowak, S. Passerini, M. Winter, J. Electrochem.
Soc.
160, 2013, A542.
[2] P. Verma, P. Maire, P. Novák, Electrochim. Acta
55, 2010, 6332.
[3] H. Bülter, F. Peters, J. Schwenzel, G. Wittstock, Angew. Chem. Int. Ed.
53, 2014, 10531.

Figure 1