Symposium S.CT03 : Expanding the Frontiers of Actinide Materials Science Through Experiment and Theory

Rachel Eloirdi, JRC Karlsruhe

The JRC Surface Science Labstation. A Unique Set-Up to Investigate Actinides in Support of Nuclear Safety and Non-Power Application of Nuclear Materials

Written by Emma Perry 

The Labstation has been specifically designed to produce and characterize actinide thin films. Here you can prepare high purity thin films used in a controlled atmosphere. The labstation then connects to characterization modules for x-ray photoelectron spectroscopy, grazing incidence x-ray diffraction, atomic force microscopy, high-resolution electron energy loss spectroscopy, and temperature programmed desorption. Unsurprisingly this highly versatile machine has been put to use in a number of cutting-edge case studies.

In the development of sodium cooled nuclear reactor technologies it is important to predict what will happen if sodium comes into contact with uranium. So, in the preparation module, UO3 and Na were deposited onto a thin film. Using the x-ray absorption spectroscopy module, it was found that at room temperature sodium does not reduce uranium. Then, during heating, a mixed state of U(IV) and U(V) was observed until 973 K when the sodium stabilized uranium in the pentavalent state.

To observe the effect of water radiolysis products on UO2, U(IV) thin film were produced and exposed to O2 plasma. Amorphous U(VI) formed. When exposed to H2O plasma, a new unknown crystalline surface was observed.

The labstation has also been used to observe the bandgap of ThF4 deposited on Au substrate in order to ascertain its viability as an optical nuclear clock.

Symposium S.SM08: Emerging Strategies and Applications in Drug Delivery

Duo Xu, University of California, Los Angeles

Efficient Delivery of Nerve Growth Factors to the Central Nervous System for Neural Regeneration

Written by Jessalyn Low Hui Ying

Nerve growth factors (NGF) are promising therapeutic agents for the treatment of central nervous system (CNS) injuries as they stimulate the proliferation and differentiation of neurons. However, the delivery of NGF to CNS is a great challenge, primarily due to the blood-brain barrier (BBB) which is a highly restrictive barrier. To address this challenge, Duo Xu and his research team took inspiration from brain biology and identified a molecular analogue, 2-methacryloyloxyethyl phosphorylcholine (MPC), which is structurally similar to the neurotransmitter acetylcholine and its precursor, choline. More importantly, MPC could also similarly interact with nicotinic acetylcholine receptors (nAChRs) and choline transporters (ChTs), therefore, may be exploited to deliver NGF across the BBB to the CNS by hijacking of the receptor/transporter pathway.

With this knowledge, the researchers designed a nanocapsule consisting of MPC monomers and polylactic acid-based crosslinkers for the encapsulation of NGF. Upon intravenous injection of these NGF nanocapsules to mice, transmission electron microscopy imaging of the cerebrospinal fluid (CSF) indicated the presence of nanocapsules. Using enzyme-linked immunosorbent assay, NGF was also observed in the brain and spinal cord tissues, indicating that the NGF nanocapsules have successfully penetrated the BBB and entered the CNS to infiltrate the brain and spinal cords. Furthermore, NGF nanocapsules were demonstrated to exhibit therapeutic effect in CNS injuries. Mouse models with compression-induced spinal cord injury showed significant functional recovery after two weeks of treatment. Neurofilaments were observed to have infiltrated the injury site, demonstrating the successful delivery of NGFs.

“Given the prevalence of CNS diseases and injuries such as Alzheimer's, Parkinson's, and stroke, our delivery platform offers an entry point for therapeutic molecules to access their molecular targets in the CNS,” says Xu.

Symposium F.EN06: Advancement of Lithium-Based High-Energy Density Batteries at Multiple Scales, Factoring in Safety

Amy Marschilok, Stony Brook University

Progress Toward Safe Electrochemical Energy Storage Systems - The Benefits of Deliberate Materials-Focused Electrode Design and Operando Characterization

Written by Vignesh Murugadoss

Dr. Amy Marschilok initially quoted that  “Anode, Cathode, and electrolyte play a crucial role in the overall safety of the electrochemical system.” She described this through a number of case studies and results from her research group that includes quantifying parasitic reactions; improving safety and power at the cathode through materials selection and electrode design; and fabricating solid-state batteries and improving safety and power at the anode through interface design. Starting from the quantification of parasitic reactions, their goal is to understand the conditions under which the system does useful work, and under which conditions the waste heat is generated from the system. Isothermal microcalorimetry coupled with fundamental electrochemistry measurement system is used to quantify the parasitic heat for Fe3O4 (insertion/conversion type) and nanocrystalline silicon (alloying type), thereby understanding the onset of side reactions which is detrimental to the capacity as well as safety of the system.

Secondly, one of the highest energy density cathode materials, carbon monofluoride, CFx (theoretical capacity = 865 mAh/g) is used in conjunction with carbon nanotubes to test the hypothesis to achieve higher rate capability power output and electrode level energy density along with a reduced inclination toward heat generation. Carbon nanotube-based electrode was effectively pulsed during pulsed intermittent discharge, whereas the aluminum foil substrate electrode was not functional. The quantitative difference measured from isothermal microcalorimetry revealed that aluminum foil generated more heat during the pulse and has a greater drop in voltage. This demonstrated that carbon nanotube-based electrodes improved rate capability higher output and reduced heat relative to the foil-based electrodes.

Thirdly, the team fabricated an all-solid-state battery using lithium iodide as the electrolyte with a lithium metal anode and iodine cathode to understand the factors governing the coulombic efficiency of the system. Impedance measured as a function of charge-discharge confirms that the impedance after charge/discharge is lower than the impedance before testing, implying an improved electrode/electrolyte interface. Furthermore, the lithium interfacial electrode system significantly increases the coulombic efficiency of the system when compared to the stainless steel and gold electrodes, which underlines the importance of the interface between the electrode and electrolyte.

Fourthly, improvement through safety and power at the anode through interface design is demonstrated by sputtering the Ni and Cu metal on graphite anode. Metal coatings reduced the Li-coating capacities by 30-40% compared to that of graphite without modifying the solid electrolyte interface chemistry. Also, the Ni-coated graphite system retained over 300 extreme fast charge cycles, which confirms the effectiveness of this approach to generate a high functioning Li-ion battery.

These examples demonstrated that materials-oriented electrode design and operando characterization contribute significantly to improve the kinetics of ion transport and safety, and bring us closer to the holy grail of concurrent high power and high energy in a safe electrochemical energy storage system.

Symposium S.CT05: Defects, Order and Disorder in Structural and Functional Fluorite- Related Compounds

Peter Crozier, Arizona State University

Locating facile oxygen vacancy creation and annihilation sites on CeO2 nanoparticle surfaces

Written by Emma Perry

Imagine you have oxygen vacancies at the surface of your cerium dioxide nanoparticle. It is reasonable that oxygen from the air may absorb and annihilate these vacancies. If you are creating a solid-oxide device then you certainly hope that this does happen, but how would you know? Peter Crozier and his collaborators find that you can infer the creation and annihilation of oxygen vacancies by observing the displacements they cause to local cerium cations. For this reason, they have used in situ in operando TEM at 40 frames per second to track the displacements of cerium cations. It has been observed that the displacements are much larger at step edge sites and that the (110) surface presents a lower activation energy than the (111) surface.

Symposium S.SM09: Advances in 3D Printing for Medical Applications

Daryl Yee, California Institute of Technology 

Genomic-DNA Coated 3D Printed Materials for Drug Capture

Written by Jessalyn Low Hui Ying

The delivery of chemotherapeutic agents for cancer treatment very often results in off-target effects. By combining the ideas of local drug delivery and local drug capture, chemotherapy treatment can potentially be confined to the tumor and intended organ. In this talk, Daryl Yee and his research team reports the scalable, versatile, and accessible fabrication and coating of a genomic DNA-functionalized 3D-printed device, capable of achieving drug capture. Additive manufacturing was used for device fabrication to allow the design of optimal fluid flow behavior and ensure hemodynamic performance.

To achieve drug capture, the researchers coated the device with genomic DNA by exploiting the fact that chemotherapeutic drugs typically attack DNA. Coating was done by soaking the 3D-printed structure in DNA, drying, and then crosslinking via UV irradiation. A second approach was proposed which involved prior surface functionalization of amine, to improve DNA binding via electrostatic interactions. Energy-dispersive x-ray spectroscopy mapping showed that electrostatic assist resulted in higher and more homogenous DNA coverage. With UV irradiation, less than 1 ng/mm2 of DNA was leached out when soaked in phosphate-buffered saline, highlighting the stability of the coating. More importantly, Yee shows how this genomic DNA-coated 3D lattices were able to capture over 60 ng/mm2 of doxorubicin from human serum, demonstrating its great potential for drug capture.

Symposium S.SM07: Bioinspired Synthesis and Manufacturing of Materials

Markus Buehler, Massachusetts Institute of Technology

Biomateriomics at the Nexus of Sound and Matter—Design, Synthesis and Manufacturing of Biomaterials

Written by Jessalyn Low Hui Ying

“The universality of vibrations and waves is very powerful and provides a striking example of how we can cross different paradigms of material modelling,” says Markus Buehler. Vibrations are a phenomenon observed in molecules, sound, and even insects, as a form of communication. In this talk, Buehler introduces the idea of modelling materials based on their vibrations, which is particularly valuable for proteins.

Amino acids, the building blocks of proteins, each have their own vibrational signature and unique sound. As proteins fold, the amino acids assemble in different configurations, resulting in an overlay of melodies and tones. Modification of protein structure will be reflected as changes in melodies, rhythms, and tonal points. By translating proteins into musical representations in the audible space, training sets can be developed for machine learning and developing neural network models for materials modelling. For example, protein structure and protein function can be correlated. More excitingly, these audible models are also reversible. By manipulating the sound, new proteins can be developed – both pre-existing and de novo. The protein sequence can also be modified to add certain functionalities as desired.

Buehler also highlighted recent work of producing a honeybee silk protein for antimicrobial food coating, achieved by using artificial intelligence to predict the protein’s shape from the primary amino acid sequence. This was later validated successfully in the lab, highlighting the great potential of materials modelling with sonification for de novo protein design.    

Symposium S.CT03: Expanding the Frontiers of Actinide Materials Science Through Experiment and Theory

Nicola Lanata, Aarhus University

Bypassing the Computational Bottleneck of Quantum-Embedding Theories for Strong Electron Correlations with Machine Learning

Written by Emma Perry 

If you are struggling to simulate the quantum mechanics of strongly correlated materials then you are not alone and Nicola Lanatas’ group could have a solution for you.

In his talk Lanata describes how n-mode expansion and the Kernel ridge regression can “break the exponential curse” of quantum embedding algorithms and reduce computation times by a factor of 1000. In a benchmark calculation the method allowed rapid convergence on a function that successfully predicted the volume of single actinide, including the elusive actinide transition jump. The same function was later applied to plutonium americium alloy systems to accurately predict the entanglement entropy.

Symposium S.SM08: Emerging Strategies and Applications in Drug Delivery

Mark Tibbitt, ETH Zürich 

Design of Dynamic Biomaterials for Thermal Stabilization of Biologics

Written by Jessalyn Low Hui Ying

The majority of therapeutic biologics are temperature-sensitive and must thus be stored in cold chain, that is, a temperature-controlled supply chain. This, however, is costly and poses health risks. To mitigate such reliance on cold chain, Mark Tibbitt and his research team developed a novel hydrogel platform – using dynamic covalent networks, based on boronic ester, for the direct encapsulation and thermal stabilization of biologics. A major advantage of this over other direct encapsulation methods is that, here, the process is reversible. This is because boronic ester, which holds the network together, exists in dynamic equilibrium. While cross-linking results in encapsulation, by shifting the equilibrium through the addition of a competitive diol, dissolution of the hydrogel network will occur, thereby releasing the biologic. The research team has demonstrated the effectiveness of this approach for thermal stabilization in enzymes and adenoviruses.

In such dynamic covalent hydrogels, two different release mechanisms exist – erosion, as driven by competitive displacement, and diffusion. To characterize the ratio of erosion to diffusion kinetics, the research team defined a dimensionless parameter α, which showed that release is erosion-dominated when a strong binder like fructose is used in competitive displacement. The team also developed a statistical model to describe erosion-based release kinetics and how external environment and network architecture influence biomolecule release, which will guide future developments of the hydrogel.

Symposium S.CT05: Defects, Order and Disorder in Structural and Functional Fluorite- Related Compounds

William Cureton, University of Tennessee, Knoxville

Effects of grain size on the radiation response of CeO2, ThO2, and UO2

Written by Emma Perry

Spent nuclear fuel has a complex microstructure caused by a number of factors. The focus of this study was to understand the effect of dense electronic energy deposition of fission fragments and use this as a measure of the radiation tolerance of CeO2, ThO2, and UO2.

Swift heavy ion-beam irradiation experiments with fluence up to 50 × 1012 cm-1 were performed on CeO2, ThO2, and UO2 samples with micrometer grains and compared to samples with nanometer grains. X-ray diffraction was used to find the change in lattice parameter and micro-strain with increasing fluence. Raman spectroscopy was used to see the relative intensity of disorder peaks and excess oxygen peaks.

ThO2 is the most radiation tolerant. The energy deposition of heavy ions caused Ce(IV) to reduce to Ce(III) such that under a high fluence, a secondary trigonal Ce11O20 phase formed in samples with micrometer grains. It was hypothesized that reducing the grain size would increase the number of defect sinks and therefore improve the radiation tolerance of a material. In fact, in nanosized grain samples, the radius of oxygen expulsion is on the same order as the grain size so the formation of the secondary Ce11O20  phase is enhanced. In UO2-micrometer grained samples, U(V) oxidized to U(VI). UO2-nanometer grained samples were initially oxidized but they reduced under the fluence and the grains coarsened.