Improving the In Vivo Stability of [ 52 Mn]Mn(II) Complexes with 18-Membered Macrocyclic Chelators for PET Imaging
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60 APPLIED LIFE SCIENCES↗
SEARCH · Engineering Papers
Results for “mechanical stability”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Unraveling the Combined Photothermal Stability of Common Perovskite Solar Cell Compositions
In halide perovskite solar cells, certain compositions, especially those with a high mixture of anions, degrade rapidly. Here, in this study, a degradation study compares the photo (exposure to light), thermal (exposure to elevated temperatures), and photo-plus-thermal (combination) stability of three representative perovskite compositions chosen for their relatively high performance and to independently test anion versus cation effects. Based upon experience and reports, the compositions studied are triple cation with a high Br ratio (Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.5 Br 0.5 ) 3 ), all iodide with a moderately high Cs ratio (FA 0.8 Cs 0.2 PbI 3 ), and FA-dominated triple cation (Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.98 Br 0.02 ) 3 ). Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.98 Br 0.02 ) 3 displayed the best combined photo-plus-thermal stability. Degradation mechanisms were investigated by comparing the morphology, surface composition, and bulk and interface carrier dynamics. Under the harshest aging conditions (photo-plus-thermal), phase segregation and vaporization of organic cations occurred, along with the appearance of high-energy states indicating the interaction with C 60 . The findings were verified on perovskite films blade-coated in air used in devices (FTO/NiOx/SAM/Perovskite/C 60 /BCP/Cu), achieving an efficiency of 21.9% alongside correlated stability.
14 SOLAR ENERGY↗
In-situ synchrotron diffraction study of the localized phase transformation and deformation behavior in NiTi SMA
The accumulation of dislocation defect was generally recognized as the origin of residual strain and the pseudoelastic instability in NiTi shape memory alloys (SMAs). In the present work, the pseudoelastic instability was studied by comparing the characteristics of Luders-type and uniform transformation mechanism via in-situ synchrotron-based high-energy X-ray diffraction (XRD) characterization. The experimental results showed that the Liiders-type mechanism could result in an intense and sharp increase of stress-induced martensite at the expense of austenite. The residual austenite with high lattice strain within the Luders band might be fully martensitic beyond the stress plateau of the E-a curve. With the accumulation of dislocation defect, the uniform martensitic transformation took place by the progressively homogeneous nucleation and growth of martensite in a local region. While the residual martensite and dislocation density was stabilized during mechanical cycling, the deformation of NiTi SMA turned into a mixture of (i) a balanced forward and reverse phase transformation between austenite and martensite, as well as (ii) the elastic deformation of the aggregate. As a result, there was no apparent increase in dislocation density detected during further cycling.
36 MATERIALS SCIENCE↗
Design of robust and versatile hydrocarbon-based single-ion-conducting polymer electrolytes
Hydrocarbon-based polymers offer several advantages, including lower environmental impacts, cost effectiveness, and the ability to finely tune properties. Here, we have developed trifluoromethanesulfonimide (TFSI)-functionalized poly(norbornene) (PNB) polymers utilizing a specifically designed oxa-Michael addition of a vinyl TFSI anion to an alcohol. Our results reveal that PNB-TFSI derivatives exhibit superior thermal stability and mechanical robustness compared with Nafion. The optimized PNB-TFSI-H-48 polymer (IEC 1.86 mmol/g) exhibits equivalent performance to Nafion as an anode ionomer in a proton exchange membrane fuel cell. Exchanging the counter ion to Li + enables PNB-TFSI to be used for Li-ion battery applications. Propylene carbonate plasticized PNB-TFSI derivatives achieve an Li-ion conductivity of over 10 −5 S/cm at 30°C. This Li polymer electrolyte exhibits excellent electrochemical stability (5 V vs. Li + /Li) and good cycling in a Li symmetric cell. These results highlight the potential and rational design of PNB-TFSI polymers for next-generation energy storage and conversion technologies.
08 HYDROGEN↗
Mechanisms enabling reconfigurability and long-term retention in vanadium oxide electrochemical memory
Phase coexistence in nanoscale electrochemical random-access memory (ECRAM) has recently been demonstrated to enable both information storage and extraordinary reconfigurability. These proof-of-principle demonstrations have left the mechanistic details of such a process unresolved. Particularly, the mechanisms that stabilize the multiple phases, and the underlying processes behind sustained memory retention, remain unclear, and are necessary to design such devices. Here we report microscale ECRAM devices composed of VO𝑥, which enables us to directly probe the active region in an operando fashion using optical techniques. Using Raman mapping, we show the phase coexistence driven by the electrochemical injection of O vacancies to be spatially uniform (i.e., with no filaments). The stability was observed to be unusually long, with 1% loss over 14 years in ambient conditions. First-principles calculations of the oxygen vacancy formation energies in VO 𝑥 further support the thermodynamic coexistence of multiple VO 𝑥 phases and clarify the origin of the observed long-term retention in the ECRAM devices. Further, we demonstrate single devices that can be voltage programmed to exhibit synaptic, neuronal, and reconfigurable logic gate functionalities. Furthermore, we not only uncover the phase coexistence mechanism that may help device design, but also demonstrate the circuit-level applications of reconfigurability.
Electrical conductivity↗
Stabilizing Graphite Anode in Electrolytes with Nanoscale Anion Networking for High-Rate Lithium Storage
Graphite is the preferred anode material in commercial lithium-ion batteries (LIBs), but its limited compatibility with various organic molecules restricts the electrolyte solvent options. The primary challenge is solvent co-intercalation with Li ions, leading to graphite layer exfoliation. As a result, electrolyte selection often relies on ethylene carbonate (EC)-based solvents. Here, in this study, we introduce electrolytes featuring a nanoscale anion network ordering that hinders the liquid-phase exfoliation of graphite. This network, formed from concentrated long-chain lithium salts, traps free dioxolane (DOL) molecules, reducing the interactions between graphite particles and solvents during Li intercalation. Our findings reveal a mechanism that stabilizes graphite in otherwise unstable solvents with concentrated salts like LiTFSI, providing key insights for improving LIB performance by addressing electrolyte limitations on graphite anodes.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Importance of Superstructure in Stabilizing Oxygen Redox in P3‐Na 0.67 Li 0.2 Mn 0.8 O 2
Abstract Activation of oxygen redox represents a promising strategy to enhance the energy density of positive electrode materials in both lithium and sodium‐ion batteries. However, the large voltage hysteresis associated with oxidation of oxygen anions during the first charge represents a significant challenge. Here, P3‐type Na 0.67 Li 0.2 Mn 0.8 O 2 is reinvestigated and a ribbon superlattice is identified for the first time in P3‐type materials. The ribbon superstructure is maintained over cycling with very minor unit cell volume changes in the bulk while Li ions migrate reversibly between the transition metal and Na layers at the atomic scale. In addition, a range of spectroscopic techniques reveal that a strongly hybridized Mn 3d–O 2p favors ligand‐to‐metal charge transfer, also described as a reductive coupling mechanism, to stabilize reversible oxygen redox. By preparing materials under three different synthetic conditions, the degree of ordering between Li and Mn is varied. The sample with the maximum cation ordering delivers the largest capacity regardless of the voltage windows applied. These findings highlight the importance of cationic ordering in the transition metal layers, which can be tuned by synthetic control to enhance anionic redox and hence energy density in rechargeable batteries.
36 MATERIALS SCIENCE↗
Secondary Ion Mass Spectrometry (SIMS) for Chemical Characterization of Metal Halide Perovskites
Metal halide perovskite (MHP) solar cells have attracted much attention due to the rapidly growing power conversion efficiency that has reached 25.2% in a decade, comparable to established commercial photovoltaic modules. Compositional engineering is one of the most effective methods to boost the performance of MHP solar cells. Further improving the efficiency and the stability of MHP solar cells necessitates good understanding of the chemical–efficiency correlation and the chemical evolution during the degradation of MHP solar cells. In this regard, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a powerful tool to investigate the chemical aspect of MHPs and has played an important role in advancing the development of MHP optoelectronics. However, up to date, a review that can guide future utilization of ToF-SIMS in the MHP development is missing. In this paper, the capabilities of ToF-SIMS in MHP investigations are summarized and analyzed from simple material synthesis and chemical distribution to more complicated device operation mechanism and stability. The strength of ToF-SIMS in resolving important issues in this field, such as interface composition, ion migration, and degradation in MHP is highlighted. Finally, an outlook with an emphasis on making the utmost of ToF-SIMS in developing MHP devices is provided.
36 MATERIALS SCIENCE↗
Stabilizing lattice oxygen redox in layered sodium transition metal oxide through spin singlet state
Abstract Reversible lattice oxygen redox reactions offer the potential to enhance energy density and lower battery cathode costs. However, their widespread adoption faces obstacles like substantial voltage hysteresis and poor stability. The current research addresses these challenges by achieving a non-hysteresis, long-term stable oxygen redox reaction in the P3-type Na 2/3 Cu 1/3 Mn 2/3 O 2 . Here we show this is accomplished by forming spin singlet states during charge and discharge. Detailed analysis, including in-situ X-ray diffraction, shows highly reversible structural changes during cycling. In addition, local CuO 6 Jahn-Teller distortions persist throughout, with dynamic Cu-O bond length variations. In-situ hard X-ray absorption and ex-situ soft X-ray absorption study, along with density function theory calculations, reveal two distinct charge compensation mechanisms at approximately 3.66 V and 3.99 V plateaus. Notably, we observe a Zhang-Rice-like singlet state during 3.99 V charging, offering an alternative charge compensation mechanism to stabilize the active oxygen redox reaction.
25 ENERGY STORAGE↗
Mechanistic study of direct coupling of CO 2 and C 2 H 4 over atomically dispersed metal at graphene edges
Direct coupling of CO 2 and ethylene (hereinafter DCCE) to acrylic acid is valuable for valorizing CO 2 to manufacture acrylate-derived products. However, previous studies in DCCE have been limited on molecular catalysts with challenges in improving catalytic performance. In this work, we employed density functional theory calculations and ab initio molecular dynamics simulations to investigate the heterogeneous catalysis of DCCE over atomically dispersed metal centers at nitrogen-doped zigzag edge of graphene. Based on competitive adsorption and structural stability, Mo, Cr, V, Ru, and Ni active sites are chosen to explore the reaction kinetics. Here, we find that the activation barriers are determined by the charge redistribution at transition states, which explains the trend of activity for the C-C coupling and the hydrogen transfer, two key steps in DCCE. Furthermore, we show that the intramolecular hydrogen transfer (rate-limiting step) is hindered due to the lack of local coordinate at the active sites. We thus propose to use co-adsorbed water as a “proton-exchanger” following a water-assisted route, and show that the activation barriers are reduced over all metal centers. Particularly, water promotes the hydrogen transfer over metals with strong CO 2 -ethylene co-activation and facile C-C coupling kinetics, which could be considered promising for DCCE. In both mechanisms, the stability of metallactone intermediate can be used to predict the catalytic activity. It is anticipated that the insights from this work can provide guidelines for mimicking well-defined multifunctional active sites in molecular catalysts to design heterogeneous catalysts for such C-C coupling, which advances catalytic utilization of CO 2 .
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Facile healing of cracks in organic–inorganic halide perovskite thin films
Organic-inorganic halide perovskite (OIHP) thin films at the heart of the burgeoning thin-film perovskite solar cells (PSCs) technology possess poor mechanical properties, which is likely to limit the long-term reliability of PSCs as they are poised for commercialization. In an effort to address this issue, in this work we demonstrate that through-thickness cracks induced by bending-tension in thin films of the two prototypical OlHPs, methylammonium lead triiodide (MAPbl(3)) and formamidinium lead triiodide (FAPbl(3)), can be healed easily. This is through the application of either a moderate compressive stress (bending-compression) at room temperature or a simple heat-treatment at modest temperatures. The crack-healing process is found to be time-dependent, which indicates that facile mass-transport in OlHPs plays a key role in this phenomenon. An explanation for this phenomenon is provided, one based on the fundamentals of brittle fracture. This discovery has broad implications for the prevention and/or restoration of the overall performance, environmental stability, and mechanical reliability of PSCs, and other devices.
36 MATERIALS SCIENCE↗
High-Spin Superatom Stabilized by Dual Subshell Filling
Quantum confinement in small symmetric clusters leads to the bunching of electronic states into closely packed shells, enabling the classification of clusters with well-defined valences as superatoms. Like atoms, superatomic clusters with filled shells exhibit enhanced electronic stability. Here, we show that octahedral transition-metal chalcogenide clusters can achieve filled shell electronic configurations when they have 100 valence electrons in 50 orbitals or 114 valence electrons in 57 orbitals. While these stable clusters are intrinsically diamagnetic, we use our understanding of their electronic structures to theoretically predict that a cluster with 107 valence electrons would uniquely combine high stability and high-spin magnetic moment, attained by filling a majority subshell of 57 electrons and a minority subshell of 50 electrons. Further, we experimentally demonstrate this predicted stability, high-spin magnetic moment (S = 7/2), and fully delocalized electronic structure in a new cluster, [NEt 4 ] 5 [Fe 6 S 8 (CN) 6 ]. This work presents the first computational and experimental demonstration of the importance of dual subshell filling in transition-metal chalcogenide clusters.
36 MATERIALS SCIENCE↗
SCF Framework, HF Stability, and RPA Correlation for Jordan–Wigner-Transformed Spin Hamiltonians on Arbitrary Coupling Topologies
Mapping spins to fermions via the Jordan–Wigner (JW) transformation can render mean-field (Hartree–Fock, HF) descriptions effective for strongly correlated spin systems. As established in recent work, the application of such approaches is not limited by the nonlocal structure of JW strings or by site ordering because string operators can be absorbed into Thouless rotations of a Slater determinant, and the variational optimization of a unitary Lie-algebraic similarity transformation removes any ordering dependence. Leveraging these ideas, we develop a self-consistent field (SCF) scheme that expresses the mean-field energy as a functional of the single-particle density matrix, providing an alternative to gradient-based optimization of Thouless parameters. We derive the analytical orbital Hessian to diagnose HF stability and compute the ground-state correlation energy through the random-phase approximation (RPA). Benchmark results for the XXZ and J 1 –J 2 model on one- and two-dimensional lattices demonstrate that RPA significantly improves mean-field accuracy.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Regioisomeric Engineering for Multicharge and Spin Stabilization in Two-Electron Organic Catholytes
Developing multicharge and spin stabilization strategies is fundamental to enhancing the lifetime of functional organic materials, particularly for long-term energy storage in multiredox organic redox flow batteries. Current approaches are limited to the incorporation of electronic substituents to increase or decrease the overall electron density or bulky substituents to sterically shield reactive sites. With the aim to further expand the molecular toolbox for charge and spin stabilization, we introduce regioisomerism as a scaffold-diversifying design element that considers the collective and cumulative electronic and steric contributions from all of the substituents based on their relative regioisomeric arrangements. Through a systematic study of regioisomers of near-planar aromatic cyclic triindoles and nonplanar nonaromatic cyclic tetraindoles, we demonstrate that this regioisomeric engineering strategy significantly enhances the H-cell cycling stability in the above two new classes of 2e – catholytes, even when current strategies failed to stabilize the multicharged species. Density functional theory calculations reveal that the strategy operates by redistributing the charge and spin densities while highlighting the role of aromaticity in charge stabilization. The most stable 2e – catholyte candidate was paired with a viologen derivative anolyte to achieve a proof-of-concept all-organic flow battery with 1.26–1.49 V, 98% capacity retention, and only 0.0117% fade/h and 0.00563% fade/cycle over 400 cycles (192 h), which is the highest capacity retention ever reported over 400 cycles in a multielectron all-organic flow battery setup. We anticipate regioisomeric engineering to be a promising strategy complementary to conventional electronic and steric approaches for multicharge and spin stabilization in other functional organic materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Analysis of phase stability and chemical segregation in the Mo-V alloys using a generalized embedded atom method potential
A new interatomic potential for the Mo-V system is introduced to facilitate the study of phase stability and mechanical properties at lower temperatures. This potential is based on a generalization of the embedded atom method and includes contributions from embedding energy, explicit two- and three-body interactions and nonlocal many-body interaction terms. The parameters of the potential are optimized by using data from ab initio density functional theory (DFT) calculations. The potential is rigorously validated across a range of physical properties, such as elastic constants, equation of states, phonon dispersion curves, point defect properties and melting temperatures for different compositions. Even though our potential is trained on a small dataset, its accuracy is comparable to available machine learning potentials for Mo and V. Furthermore, our results show that an ordered B2 phase is stable at low temperatures in alloys containing 50% V, but the solid solution phase is stable above 800 K. However, such long-range ordering is not observed in V-rich or Mo-rich alloys. In addition, our results show that V segregates to dislocation cores and grain boundaries.
36 MATERIALS SCIENCE↗
A Comprehensive Machine Learning Model for Metal–Ligand Binding Prediction: Applications in Chemistry and Biology
A machine-learning (ML) model that predicts metal–ligand binding constants was developed using the open-source Chemprop software. The model was trained on over 30,000 experimental log K 1 values, which include both protonation and metal–ligand stability constants, comprising over 3500 ligands and 10 2 metal ions from 73 total elements, thus generalizing beyond existing limited approaches, which focus only on specific metals or ligand families. The best-performing model included a combination of SMILES-based molecular representations along with descriptors for the metal ion and experimental conditions. It had an external test R 2 value of 0.942, and MAE value of 0.834. A “SMILES-only” simpler version also produced accurate predictions and preserved the binding trends, serving as a quick and easily accessible alternative for users without computational expertise. The SMILES-only model performed comparably to density functional theory (DFT) calculations but utilized a fraction of the computational resources. The model was successfully applied across diverse domains, including bioinorganic chemistry, heavy metal remediation, and sensor development and demonstrated its effectiveness as a rapid and reliable screening tool for both academic and industrial uses.
Ligands↗
Role of thermo-mechanical gyrations on the α/β interface stability in a Ti6Al4V AM alloy
Fluctuating energy distributions experienced during Additive Manufacturing yield an evolution of spatial and temporal transients within a part. In general, the in-situ monitoring of these transients is near to impossible during manufacturing. In order to then gain perspective into the impact on these localized thermo-mechanical transients on the interface stability, rapid thermo-mechanical reversals with known boundary conditions are imposed on an AM Ti6Al4V alloy which resulted in a phase transformation leading to an increased β phase stability. Our goal with this study is to comprehend the kinetics of this phase transformation with concepts of stored energy due to plastic strain accumulation and diffusion kinetics. Atom Probe Tomography is employed to study the partitioning of the solute elements across the interface. As expected, the thermo-mechanically cycled samples showed a reduced Vanadium concentration across the β phase. Finally, this concentration profile across the interface, alongside a full-width-half-max analysis, provided insight on the potential phase transformation kinetics involved in the α → β transformation subject to thermo- mechanical gyrations.
36 MATERIALS SCIENCE↗
Effect of Phosphorus Modulation in Iron Single‐Atom Catalysts for Peroxidase Mimicking
Abstract Fe–N–C single‐atom catalysts (SACs) exhibit excellent peroxidase (POD)‐like catalytic activity, owing to their well‐defined isolated iron active sites on the carbon substrate, which effectively mimic the structure of natural peroxidase's active center. To further meet the requirements of diverse biosensing applications, SAC POD‐like activity still needs to be continuously enhanced. Herein, a phosphorus (P) heteroatom is introduced to boost the POD‐like activity of Fe–N–C SACs. A 1D carbon nanowire (FeNCP/NW) catalyst with enriched Fe–N 4 active sites is designed and synthesized, and P atoms are doped in the carbon matrix to affect the Fe center through long‐range interaction. The experimental results show that the P‐doping process can boost the POD‐like activity more than the non‐P‐doped one, with excellent selectivity and stability. The mechanism analysis results show that the introduction of P into SAC can greatly enhance POD‐like activity initially, but its effect becomes insignificant with increasing amount of P. As a proof of concept, FeNCP/NW is employed in an enzyme cascade platform for highly sensitive colorimetric detection of the neurotransmitter acetylcholine.
Ding, Shichao↗