Remote controlled optical manipulation of bimetallic nanoparticle catalysts using peptides
Explore the source record for details and available documents.
99 GENERAL AND MISCELLANEOUS↗
SEARCH · Search NASA
Results for “functionalized ligand”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Functionalized nona-silicide [Si 9 R 3 ] Zintl clusters: a new class of superhalogens
Superatoms, due to their various applications in redox and materials chemistry, have been a major topic of study in cluster science. Superhalogens constitute a special class of superatoms that mimic the chemistry of halogens and serve as building blocks of novel materials such as super and hyper salts, perovskite-based solar cells, solid-state electrolytes, and ferroelectric materials. These applications have led to a constant search for new class of superhalogens. Here, in this study, using density functional theory, we show that recently synthesized [Si 9 {Si ( t Bu) 2 H} 3 ] and [Si 9 {Si (TMS) 3 } 3 ] Zintl clusters not only behave like halogens but also when functionalized with suitable ligands exhibit superhalogen characteristics. Frontier molecular orbital (FMO) analyses give insights into the electron-accepting nature of the Zintl clusters. Additional bonding techniques such as energy density at the bond critical point (BCP) and adaptive natural density partitioning (AdNDP) gives complementary information about the nature of bonding in Si 9 -based Zintl clusters. The potential of these Zintl clusters in the synthesis of new electrolytes in Li-ion batteries is also investigated.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A comprehensive approach for elucidating the interplay between 4f n +1 and 4f n 5d 1 configurations in Ln 2+ complexes
Lanthanides (Ln) are typically found in the +3 oxidation state. However, in recent decades, their chemistry has been expanded to include the less stable +2 oxidation state across the entire series except promethium (Pm), facilitated by the coordination of ligands such as trimethylsilylcyclopentadienyl, C 5 H 4 SiMe 3 (Cp'). The [LnCp' 3 ] complexes have been the workhorse for the synthesis and theoretical study of the fundamental aspects of divalent lanthanide chemistry, where experimental and computational evidence have suggested the existence of different ground state (GS) configurations, 4f n+1 or 4f n 5d 1 , depending on the specific metal. Standard reduction potentials and 4f n+1 to 4f n 5d 1 promotion energies have been two factors usually considered to rationalize the occurrence of these variable GS configurations, however the driving force behind this phenomenon is still not clear. In this work we present a comprehensive theoretical approach to shed light on this matter using the [LnCp 3 ] - model systems. We begin by calculating 4f n+1 to 4f n 5d 1 promotion energies and successfully correlate them with existing experimental data. Furthermore, we analyze how changes in the GS charge distribution between the Ln ions, LnCp 3 and the reduced [LnCp 3 ] - complexes (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) correlate with experimental trends in redox potentials and the calculated promotion energies. For this purpose, a comprehensive theoretical work that includes relativistic ligand field density functional theory (LFDFT) and relativistic ab initio wavefunction methods was performed. This study will help the rational design of suitable environments to tune the different GS configurations as well as modulating the spectroscopic properties of new Ln 2+ complexes.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Unoccupied electronic structure of actinide dioxides
Ligand field density functional theory calculations of the dioxides of thorium, uranium, and plutonium have been combined with high-energy-resolution fluorescence detection (HERFD) in x-ray absorption spectroscopy and inverse photoelectron spectroscopy (IPES) measurements to provide powerful insight into the underlying composition of the unoccupied 5f electronic structure in these 5f localized systems. Fine structure in the 5f 5/2 transitions in HERFD can be directly correlated with the fine structure in the leading edge of the IPES. The shapes, intensities, and systematics in HERFD and IPES are explained in a consistent and rigorous fashion in terms of the j-specific 5f electronic structure.
36 MATERIALS SCIENCE↗
Ligand-exchangeable nanoparticles and methods of making the same
An aspect of the present disclosure is a nanocrystal that includes a nanocrystal core and a ligand coordinated to a surface of the nanocrystal core, where the ligand includes a functionalized aromatic molecule. In some embodiments of the present disclosure, the functionalized aromatic molecule may include at least one of cinnamic acid (CAH) and/or a functionalized CAH molecule.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Molecular tracers and modified proppants for monitoring underground fluid flows
The present invention relates to modified proppants and methods of using the modified proppants that use metal ligand tracers to characterize subterranean fluid flow. The metal and ligands are best chosen to be a strongly-coordinating, chelating ligand with a functional group for the chosen flow environment.
Kemp, Richard A.↗
Molecular tracers and modified proppants for monitoring underground fluid flows
The present invention relates to modified proppants and methods of using the modified proppants that use metal ligand tracers to characterize subterranean fluid flow. The metal and ligands are best chosen to be a strongly-coordinating, chelating ligand with a functional group for the chosen flow environment.
Kemp, Richard A.↗
Controlling Extraction of Rare Earth Elements Using Functionalized Aryl-vinyl Phosphonic Acid Esters
Ligands that can discriminate between individual rare earth elements are important for production of these critical elements. A set of aryl-vinyl phosphonic acid ligands for extracting rare earth elements were designed and synthesized under the hypothesis that the strength of the rare earth-ligand interactions could be tuned by changing the dipole moment of the ligand. The ligands were synthesized via a two-step reaction procedure using a Heck coupling reaction to functionalize vinyl phosphonic acid, followed by Steglich esterification to obtain high-purity styryl phosphonic acid monoesters with varying dipole moments along the P-C bond. The metal binding strength and composition of the rare earth complexes formed with these styryl phosphonic acid monoesters were experimentally studied by liquid-liquid extraction techniques, while DFT calculations were performed to determine the dipole moments of the free and complexed ligands and the electronic structure of the complexes formed. All three prepared ligands were much stronger extracting agents for europium(III) than the dialkylphosphonic acids usually used for this separation. However, the order of increasing extraction strength was found to match the order of the decreasing calculated dipole moment along the P-C bond of the three styryl-based ligands, rather than correlating with increasing ligand basicity, as reflected by the pK a of the ligands. Finally, these findings suggest that this approach can be used to systematically alter the extraction strength of aromatic phosphonic monoesters for rare earth element purification.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Boric acid removal with polyol-functionalized polyether membranes
Poor selectivity of conventional desalination membranes for boron often necessitates multi-stage treatment trains to achieve desired boron removal for end uses such as irrigation. One approach to membrane design for improved single-pass boric acid removal is via incorporation of chelating ligands that selectively sorb boron. In this study, membranes based on epoxy-amine cross-linked poly(glycidyl glycidyl ether) (PGGE) were synthesized and functionalized with N-methyl-d-glucamine (NMDG), a polyol known to interact selectively with boron. PGGE and PGGE-NMDG membranes exhibited boron sorption isotherms that were well-described by dual mode isotherms. PGGE-NMDG sorbed 2.5 mmol B/g dry polymer from a neutral aqueous solution containing 100 mmol B/L, which was almost three times the adsorption density of a commercial boron selective resin, Amberlite IRA743. Further, the membranes were regenerated in acid without a significant loss of boron sorption capacity over four cycles. Interactions between boron and NMDG and PGGE sites (e.g., epoxides) impacted boron diffusion in both membranes. The use of ligand functionalized membranes to capture target solutes such as boron requires high loading of interacting sites to maximize uptake capacity. Establishing fundamental structure/property rules for boron selectivity could lead to new material designs with improved boron separation properties for water purification.
36 MATERIALS SCIENCE↗
Well-defined Pt(0) heterogeneous hydrosilylation catalysts supported by a surface bound phosphenium
Single atom, low valent transition metals are important for heterogeneous catalysis but are challenging to generate and stabilize in a well-defined manner. Herein, we explored the functionalization of silica with well-defined N-heterocyclic phosphenium (NHP) ions to heterogenize low-valent metals. The surface electro-statically bound [NHP] + coordinate to Pt(0) precursors resulting in well-defined, chemisorbed [(NHP)Pt(0)L n ] + sites. The resulting materials catalyze the hydrosilylation of alkynes and exhibit activities and selectivities that rival the current industry standard homogeneous catalysts. The catalysts leach Pt limiting their recyclability; however, recycling studies support that the high regioselectivities arise from heterogeneous sites and Pt particles do not form on the surface. Here we suspect that this phosphenium-based immobilization strategy will result in stable, tunable, low valent heterogeneous transition metal catalysts in a wider array of catalytic reactions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Isoform- and ligand-specific modulation of the adhesion GPCR ADGRL3/Latrophilin3 by a synthetic binder
Adhesion G protein-coupled receptors (aGPCRs) are cell-surface proteins with large extracellular regions that bind to multiple ligands to regulate key biological functions including neurodevelopment and organogenesis. Modulating a single function of a specific aGPCR isoform while affecting no other function and no other receptor is not trivial. Here, we engineered an antibody, termed LK30, that binds to the extracellular region of the aGPCR ADGRL3, and specifically acts as an agonist for ADGRL3 but not for its isoform, ADGRL1. The LK30/ADGRL3 complex structure revealed that the LK30 binding site on ADGRL3 overlaps with the binding site for an ADGRL3 ligand – teneurin. In cellular-adhesion assays, LK30 specifically broke the trans-cellular interaction of ADGRL3 with teneurin, but not with another ADGRL3 ligand – FLRT3. Our work provides proof of concept for the modulation of isoform- and ligand-specific aGPCR functions using unique tools, and thus establishes a foundation for the development of fine-tuned aGPCR-targeted therapeutics.
59 BASIC BIOLOGICAL SCIENCES↗
Systematic Bandgap Engineering of a 2D Organic–Inorganic Chalcogenide Semiconductor via Ligand Modification
Hybrid organic–inorganic semiconductors present new opportunities for optoelectronic materials design not available in all-organic or all-inorganic materials. One example is silver phenylselenide (AgSePh) – or “mithrene” – a blue-emitting 2D organic–inorganic semiconductor exhibiting strong optical and electronic anisotropy. Here, we show that the bandgap of mithrene can be systematically tuned by introducing electron-donating and electron-withdrawing groups to the phenyl ligands. We synthesized nine mithrene variants, eight of which formed 2D van der Waals crystals analogous to those of AgSePh. Density functional theory calculations reveal that these 2D mithrene variants are direct-gap or nearly direct gap semiconductors. Furthermore, we identify correlations between the optical gap and three experimental observables – the Hammett constant, 77 Se chemical shift, and selenium partial charge – offering predictive power for bandgap tuning. These findings highlight new opportunities for applying the tools of chemical synthesis to semiconductor materials design.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Active learning of polarizable nanoparticle phase diagrams for the guided design of triggerable self-assembling superlattices
Polarizable nanoparticles are of interest in materials science because of their rich and complex phase behavior that can be used to engineer nanostructured materials with long-range crystalline order. To understand and rationally navigate the design space of polarizable nanoparticles for self-assembling highly ordered superlattices, we developed a coarse-grained computational model to describe the nanoparticle-nanoparticle interactions in implicit solvent and employ the computationally efficient image method to model many-body polarization interactions. We conducted high-throughput virtual screening over a five-dimensional particle design space spanned by temperature, particle size, particle charge, particle dielectric, and solvent dielectric using enhanced sampling molecular dynamics calculations within an active learning framework to efficiently map out the regions of thermodynamic stability of the self-assembled aggregates. We validate our predictions in comparisons against small angle x-ray scattering measurements of gold nanoparticles surface functionalized with metal chalcogenide ligands. Lastly, we use our validated phase maps to computationally design switchable nanostructured materials capable of triggered assembly and disassembly as a function of temperature and solvent dielectric with potential applications as sensors, smart windows, optoelectronic devices, and in medical diagnostics.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Extending Magnetic Core Shell Nanoparticle Extraction Technology to Cesium and Antimony Removal from Geothermal Brines in New Zealand
Our industrial client (Geo40) has developed and deployed a process to remove silica from geothermal fluids and produce a high-margin specialty colloidal silica product comparable to those of market leaders. Geo40 now wishes to explore opportunities to extend their mineral extraction operations to other elements that are present in these brines. Geo40 has identified cesium (Cs) that is present in Ohaaki brines (pH ~8–8.5) at parts per million levels and could be sold to customers if it could be produced at an attractive price. With support from the Department of Energy’s (DOE’s) Geothermal Technologies Office, a simple and highly cost-effective magnetic nanofluid method for extraction of rare earth elements (REEs) from geothermal brine solutions has been developed and demonstrated at the laboratory bench scale at Pacific Northwest National Laboratory (PNNL). Core shell sorbent particles are produced using an iron oxide core particle, which is used to anchor and grow a surrounding adsorbent shell functionalized with a chelating ligand that selectively binds REEs. We extended PNNL’s work by exploring new sorbent shells that are highly selective for Cs. Uptake of Cs was measured as a function of exposure time by analyzing solution samples extracted from batch sorption tests.
15 GEOTHERMAL ENERGY↗
Evaluation of an Image-Derived Input Function for Kinetic Modeling of Nicotinic Acetylcholine Receptor-Binding PET Ligands in Mice
Positron emission tomography (PET) radioligands that bind with high-affinity to α4β2-type nicotinic receptors (α4β2Rs) allow for in vivo investigations of the mechanisms underlying nicotine addiction and smoking cessation. Here, we investigate the use of an image-derived arterial input function and the cerebellum for kinetic analysis of radioligand binding in mice. Two radioligands were explored: 2-[ 18 F]FA85380 (2-FA), displaying similar pKa and binding affinity to the smoking cessation drug varenicline (Chantix), and [ 18 F]Nifene, displaying similar pKa and binding affinity to nicotine. Time–activity curves of the left ventricle of the heart displayed similar distribution across wild type mice, mice lacking the β2-subunit for ligand binding, and acute nicotine-treated mice, whereas reference tissue binding displayed high variation between groups. Binding potential estimated from a two-tissue compartment model fit of the data with the image-derived input function were higher than estimates from reference tissue-based estimations. Rate constants of radioligand dissociation were very slow for 2-FA and very fast for Nifene. We conclude that using an image-derived input function for kinetic modeling of nicotinic PET ligands provides suitable results compared to reference tissue-based methods and that the chemical properties of 2-FA and Nifene are suitable to study receptor response to nicotine addiction and smoking cessation therapies.
2-FA85380↗
Chemical bonding in actinyl( V / VI ) dipyriamethyrin complexes for the actinide series from americium to californium: a computational investigation
The separation of minor actinides in their dioxocation (i.e., actinyl) form in high-valence oxidation states requires efficient ligands for their complexation. Here, in this work, we evaluate the complexation properties of actinyls including americyl, curyl, berkelyl, and californyl in their pentavalent and hexavalent oxidation states with the dipyriamethyrin ligand (L) using density functional theory calculations. The calculated bond parameters show shorter An═O yl bonds with covalent character and longer An–N bonds with ionic character. The bonding between the actinyl cation and the ligand anion shows a flow of charges from the ligand to actinyl in all [An V/VI O 2 –L] 1–/0 complexes. However, across the series, backdonation of charges from the metal to the ligand becomes prominent and stabilizes the complexes. The thermodynamic parameters in the gas phase and solution suggest that the complex formation reaction is spontaneous for [Cf V/VI O 2 –L] 1–/0 complexes and spontaneous at elevated temperatures (>298.15 K) for all other complexes. Spin–orbit corrections have a quantitative impact while the overall trend remains the same. Energy decomposition analysis (EDA) reveals that the interaction between actinyl and the ligand is mainly due to electrostatic contributions that decrease from Am to Cf along with an increase in orbital contributions due to the backdonation of charges from the actinyl metal center to the ligand that greatly stabilizes the Cf complex. The repulsive Pauli energy contribution is observed to increase in the case of [An V O 2 –L] 1– complexes from Am to Cf while a decrease is observed among [An VI O 2 –L] 0 complexes, showing minimum repulsion in [Cf VI O 2 –L] 0 complex formation. Overall, the hexavalent actinyl complexes show greater stability (increasing from Am to Cf) than their pentavalent counterparts.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A glycan receptor kinase facilitates intracellular accommodation of arbuscular mycorrhiza and symbiotic rhizobia in the legume Lotus japonicus
Receptors that distinguish the multitude of microbes surrounding plants in the environment enable dynamic responses to the biotic and abiotic conditions encountered. In this study, we identify and characterise a glycan receptor kinase, EPR3a, closely related to the exopolysaccharide receptor EPR3. Epr3a is up-regulated in roots colonised by arbuscular mycorrhizal (AM) fungi and is able to bind glucans with a branching pattern characteristic of surface-exposed fungal glucans. Expression studies with cellular resolution show localised activation of the Epr3a promoter in cortical root cells containing arbuscules. Fungal infection and intracellular arbuscule formation are reduced in epr3a mutants. In vitro , the EPR3a ectodomain binds cell wall glucans in affinity gel electrophoresis assays. In microscale thermophoresis (MST) assays, rhizobial exopolysaccharide binding is detected with affinities comparable to those observed for EPR3, and both EPR3a and EPR3 bind a well-defined β-1,3/β-1,6 decasaccharide derived from exopolysaccharides of endophytic and pathogenic fungi. Both EPR3a and EPR3 function in the intracellular accommodation of microbes. However, contrasting expression patterns and divergent ligand affinities result in distinct functions in AM colonisation and rhizobial infection in Lotus japonicus . The presence of Epr3a and Epr3 genes in both eudicot and monocot plant genomes suggest a conserved function of these receptor kinases in glycan perception.
59 BASIC BIOLOGICAL SCIENCES↗
Redox-Induced Structural Reorganization Dictates Kinetics of Cobalt(III) Hydride Formation via Proton-Coupled Electron Transfer
Two-electron, one-proton reactions of a family of [CoCp(dxpe)(NCCH 3 )] 2+ complexes (Cp = cyclopentadienyl, dxpe = 1,2-bis(di(aryl/alkyl)phosphino)ethane) form the corresponding hydride species [HCoCp(dxpe)] + through a stepwise proton-coupled electron transfer process. For three [CoCp(dxpe)(NCCH 3 )] 2+ complexes (dxpe = dppe (1,2-bis(diphenylphosphino)ethane), depe (1,2-bis(diethylphosphino)ethane), and dcpe (1,2-bis(dicyclohexylphosphino)ethane)), peak shift analysis was employed to quantify apparent proton transfer rate constants from cyclic voltammograms recorded with acids ranging 22 pK a units. The apparent proton transfer rate constants correlate with the strength of the proton source for weak acids, but these apparent proton transfer rate constants curiously plateau (k pl ) as the reaction becomes increasingly exergonic. The absolute apparent proton transfer rate constants across both these regions correlate with the steric bulk of the chelating diphosphine ligand, with bulkier ligands leading to slower kinetics (k plateau,depe = 3.5 x 10 7 M -1 s -1 , k plateau,dppe = 1.7 x 10 7 M -1 s -1 , k plateau,dcpe = 7.1 x 10 4 M -1 s -1 ). Mechanistic studies were conducted to identify the cause of the aberrant $k_PT^{app}$–ΔpK a trends. When the deuterated acids are employed, deuterium incorporation in the Cp ring is observed, indicating protonation of the CoCp(dxpe) species to form the corresponding hydride proceeds via initial ligand protonation. Digital simulations of cyclic voltammograms show ligand loss accompanying initial reduction gates subsequent PCET activity at higher driving forces. Together, these experiments reveal the details of the reaction mechanism: reduction of the Co(III) species is followed by dissociation of the bound acetonitrile ligand, subsequent reduction of the unligated Co(II) species to form a Co(I) species is followed by protonation, which occurs at the Cp ring, followed by tautomerization to generate the stable Co(III)-hydride product [HCoCp(dxpe)] + . Analysis as a function of chelating disphosphine ligand, solvent, and acid strength reveals that the ligand dissociation equilibrium is directly influenced by the steric bulk of the phosphine ligands and gates protonation, giving rise to the plateau of apparent proton transfer rate constant with strong acids. The complexity of the reaction mechanism underpinning hydride formation, encompassing dynamic behavior of the entire ligand set, highlights the critical need to understand elementary reaction steps in proton-coupled electron transfer reactions.
14 SOLAR ENERGY↗