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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Spectroscopic Insight on Neodymium Solvation in Lithium Borohydride-Supported Electrolyte

Borohydride-based electrolytes have recently emerged as promising media for the electrodeposition of electropositive metals, including rare earth (RE) elements. While the presence of supporting alkali metal cations and RE counteranions provides essential electrochemical conductivity for achieving fast metal electrodeposition, interactions between the host ligand and solvated neodymium (Nd) complexes remain unclear. This study provides insights into the coordination structure of a concentrated and directly solvated Nd salt in a lithium borohydride-supported electrolyte. Our spectroscopic results indicate that the RE coordination environment is significantly influenced by the solvation mechanism, which can vary between metathesis and complexation pathways, primarily dictated by stoichiometric factors. Under dilute conditions, nearly complete metathesis of anions leads to a high coordination number for the host ligand (borohydride), consistent with the previously reported solvated Nd speciation in chlorine-free electrolytes. In contrast, concentrated dissolution of the Nd salt in the supported electrolyte is dominated by a complexation pathway featuring a Li-ion-paired complex with a low coordination number of the host ligand. Density functional theory (DFT) calculations indicated that the observed blue shift in the borohydride vibration was the result of an increase in electron density drawn into the terminal B–H interbond region from the hydride as the coordination changed from Li to Nd. In conjunction with DFT results, vibrational analyses allowed correlation of the experimental shifts associated with changes in Nd ligation and coordination spheres, further consolidating the prevalence of highly chloride-coordinated species under concentrated conditions. In conclusion, the outcomes of this work illuminate the distinctive and heterogeneous coordination structures that the electroactive RE species can adopt at high concentrations in lithium borohydride-supported electrolytes, as a key step to comprehend the reported metal electrodeposition performance in these media.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Novel Electrowinning Reactor for the Energy-Efficient, Low- Cost Production of Rare Earth Metals

This project developed a novel neodymium (Nd) electrowinning reactor for energy-efficient electrowinning of Nd metal. Throughout this project we have developed an alternative chloride based molten salt electrolysis process. Our process lowers the specific electrical energy consumption compared to the state of the art, while producing reusable chlorine gas and eliminating direct CO2 and PFC emissions. Facilities required for implementing the project were setup and designs were finalized, and a standard operating procedure for safe operation of high temperature electrolysis cells was written. The electrowinning reactor was designed and constructed. Electrolysis experiments confirmed the ability to reproducibly electrowin Nd metal on a Mo cathode. The current efficiency for Nd electrowinning was measured as a function of applied current density in the presence of the separator. Successful electrowinning of Nd sponge at high current densities (200 mA/cm2 and above) at a current efficiency >80% was demonstrated using multiple techniques. Stable Nd electrowinning up to 10h at 250 mA/cm2 was demonstrated. All of these design advancements were used to develop a techno-economic and life cycle assessment model that demonstrated that our process could be operated at cost of less than $0.20/kg-Nd (~30% lower compared to state of the art when comparing electrolysis energy cost) with a >20% total reduction in global warming potential compared to the state of the art while generating no direct CO2 or perfluorocarbon emissions.

42 ENGINEERING↗
DOE OSTI2024

Chelator‐Assisted Precipitation‐Based Separation of the Rare Earth Elements Neodymium and Dysprosium from Aqueous Solutions

The rare earth elements (REEs) are critical resources for many clean energy technologies, but are difficult to obtain in their elementally pure forms because of their nearly identical chemical properties. Here, an analogue of macropa, G-macropa, was synthesized and employed for an aqueous precipitation-based separation of Nd 3+ and Dy 3+ . G-macropa maintains the same thermodynamic preference for the large REEs as macropa, but shows smaller thermodynamic stability constants. Molecular dynamics studies demonstrate that the binding affinity differences of these chelators for Nd 3+ and Dy 3+ is a consequence of the presence or absence of an inner-sphere water molecule, which alters the donor strength of the macrocyclic ethers. Leveraging the small REE affinity of G-macropa, we demonstrate that within aqueous solutions of Nd 3+ , Dy 3+ , and G-macropa, the addition of HCO 3 − selectively precipitates Dy 2 (CO 3 ) 3 , leaving the Nd 3+ −G-macropa complex in solution. With this method, remarkably high separation factors of 841 and 741 are achieved for 50 : 50 and 75 : 25 mixtures. Further studies involving Nd 3+ :Dy 3+ ratios of 95 : 5 in authentic magnet waste also afford an efficient separation as well. Finally, G-macropa is recovered via crystallization with HCl and used for subsequent extractions, demonstrating its good recyclability.

Gao, Yangyang↗
DOE OSTI2024

Parametric optimization of the liquid sampling-atmospheric pressure glow discharge ionization source coupled to an Orbitrap mass spectrometer for neodymium isotope ratio determinations

Isotope ratio determinations are a valuable tool in several application areas. In nuclear forensics, the isotope ratios of uranium and plutonium are commonly used as a signature for the nuclear material's provenance and processing history. However, signatures from other coexisting elements, such as neodymium and samarium, can offer additional insights. Here, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) ionization source coupled to an Orbitrap mass spectrometer (MS) has demonstrated its utility for actinide measurements. This instrumental platform can leverage the high resolution offered by the Orbitrap MS to overcome potential isobaric interferences, such as 144 Nd- 144 Sm, 148 Nd- 148 Sm, and 150 Nd- 150 Sm pairs. The work presented herein demonstrates the rapid, accurate, and precise determination of the isotope ratios for neodymium using the LS-APGD/Orbitrap MS. Both the LS-APGD and Orbitrap MS parameters were optimized systematically, with NdO + found to be the most abundant, most reduced species after applying the optimal collision-induced dissociation modalities. A limit of detection of 3 pg of 142 Nd was achieved when data was acquired and processed using the FTMS Booster, an external data acquisition and processing system offered by Spectroswiss. Excellent accuracy of better than 99 % and precision of <1 % RSD were achieved when a solution of the well-characterized neodymium standard (JNdi-1 standard) was analyzed under the optimized condition, indicating the LS-APGD/Orbitrap's great potential for isotope ratio analysis of Nd and other REEs for diverse applications.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

f-Element complexes with benzyl and cyclohexyl substituted trihydroborates

Actinide complexes containing the simplest borohydrides (BH 4 ) 1- and (MeBH 3 ) 1- can exhibit remarkably highly volatility, which creates unique hazards and handling challenges, especially when making measurements on solid samples under vacuum. Here we describe efforts to prepare new actinide borohydride complexes with attenuated volatility by adding bulkier benzyl (Bn) and cyclohexyl (Cy) substituents to boron. Reactions of ThCl 4 , UI 3 (thf) 4 , and NdI 3 with the mixed alkali metal salt Li/K(BnBH 3 )(thf) n yielded Th(BnBH 3 ) 4 (thf) 2 , U(BnBH 3 ) 4 (thf) 2 , and K[Nd(BnBH 3 ) 4 ], respectively. Notable amongst these, the reaction with UI 3 (thf) 4 proceeds via oxidation of U(III) to U(IV) despite the presence of reducing borohydride ligands. Similarly, reactions of the same metal halides with four equivalents of Li(CyBH 3 )(Et 2 O) n yielded Th(CyBH 3 ) 4 , U(CyBH 3 ) 4 (thf) 2 , and [Li(Et 2 O) 3 ][Nd(CyBH 3 ) 4 ]. Single crystal X-ray diffraction studies of the M(BnBH 3 ) 4 (thf) 2 complexes with M = Th and U confirmed their formulations. Furthermore, the complexes have approximate D 2d point group symmetry and adopt bicapped hexagonal antiprismatic coordination geometries with axial thf ligands and κ 3 -BnBH 3 ligands bound in the equatorial plane. K[Nd(BnBH 3 ) 4 ] and [Li(Et 2 O) 3 ][Nd(CyBH 3 ) 4 ], which were prepared for comparison to U(III) complexes that were unsuccessfully targeted, were also structurally characterized to reveal complex anions with tetrahedral arrangements of trihydroborate ligands bound to Nd(III). Crystals obtained for Th(CyBH 3 ) 4 and U(CyBH 3 ) 4 (thf) 2 were not suitable for XRD studies, but 1 H and 11 B NMR spectra were consistent with their formulations. Collectively, these complexes represent rare examples of structurally characterized f-element trihydroborate complexes with carbon substituents other than methyl.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Spectroscopic Online Monitoring: Using a Multi-Track Visible Spectrometer to Facilitate a Mass Balance Study in a Simulated TALSPEAK Process

Nuclear energy is a promising low-carbon energy candidate to meet the increased demand for green energy, where the integration of fuel recycling can have significant benefits for material usage and waste reduction. Utilizing in situ monitoring tools can provide ample opportunities to better control and safeguard nuclear material recycle processes while also offering knowledge and insight into real-time solution properties. The simultaneous measurement of analytical targets in multiple process locations can enable real-time mass balance and material accountancy calculations. This is demonstrated here with a mass balance study of Nd 3+ on countercurrent aqueous/organic metal extraction within a single centrifugal contactor. The Nd 3+ concentration was simultaneously monitored at the inlets and outlets of both aqueous and organic phases using a visible absorbance detector that allowed for the simultaneous measurement of up to six locations. The Nd 3+ concentration was calculated by using chemical data science algorithms, where model training sets were collected on a single track of the detector. The discussion includes addressing the challenges of using a model collected on a single track and applying it as a model across the other tracks on the detector. Each track of the detector corresponds to one measurement location on the contactor. The difference in the integrated moles of Nd 3+ between the inlet and outlet at the end of the experiment was near zero, indicating that the mass balance of this experiment was maintained. Overall, the online spectroscopic monitoring was able to follow changing solution conditions and accurately measure the concentration of Nd 3+ in different locations within the contactor system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Ambient Rare Earth Metal Electrodeposition in Nitrogen-Coordinated Silylamide Electrolyte

The transition to a sustainable, low-carbon economy demands energy-efficient and environmentally benign methods for rare earth metal (REM) production. Furthermore, while high-temperature molten salt electrolysis remains energy-intensive, corrosive, and environmentally unfriendly, emerging room-temperature processes based on conventional ionic liquids are also hindered by high viscosity and chemical instability. In this study, a nitrogen-coordinated, water-, oxygen-, and fluorine-free silylamide-based electrolyte is presented as a promising system for room-temperature REM electrodeposition. Derived from commercially available lithium silylamide precursors, the system enables facile synthesis, broad electrochemical stability, and tunable metal–ligand interactions. Electrochemical analysis reveals high voltammetric stripping reversibility, stable cathodic and anodic potentials, and selective neodymium (Nd) deposition at appreciable current densities (>1 mA/cm 2 ), with minimal parasitic reactions. Bulk experiments produced high-purity Nd with reproducible performance across multiple batches. Scaled deposition yielded over 1 g of Nd with near-theoretical mass efficiency (0.40 mg/C) and >90% purity. Using sacrificial dysprosium (Dy) and Nd metal anodes, the system maintained constant Nd loading during extended deposition and enabled cathodic codeposition of stripped anode material, demonstrating the electrolyte’s dual functionality for REM electrorefining. Collectively, this silylamide platform offers a compelling combination of electrochemical robustness, chemical resilience, and process scalability for sustainable ambient REM recovery.

36 - MATERIALS SCIENCE↗
DOE OSTI2025

Structural incorporation into goethite fractionates rare earth elements

Up to 20% of rare earth elements (REEs) in ion adsorption deposits (IADs) are associated with iron oxide minerals, primarily goethite. Often termed “non-extractable”, goethite-hosted REEs are thought to be structurally incorporated into the mineral lattice. The large mismatch in size and charge density between REEs (ionic radius, r = 0.86–1.03 Å) and Fe 3+ (r = 0.65 Å), however, makes direct substitution energetically unfavorable. To determine REE compatibility with and incorporation into goethite on the atomic level, we used X-ray pair distribution function analysis (PDF) and LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The compatibility of REEs with goethite and the precursor ferrihydrite (FH) is Lu ≥ Yb ≫ Dy > Nd for both phases. Nd and Dy primarily form secondary amorphous phases, with <30% Nd and Dy incorporated into goethite. In the FH precursor at pH 6.8, Yb and Lu assumed a local REE-OOH like structure with next nearest neighbor Fe. The Yb, Lu, and Nd-FH samples were also matured at ambient conditions for 100 days; despite the presence of only ∼5% goethite, Lu and Yb were 42% and 100% in goethite-like structural environments, respectively, whereas the PDF and EXAFS of Nd showed little evidence of any incorporation. Using ab initio molecular dynamics (AIMD) to model the EXAFS, we determined the presence of protonated Fe vacancies, edge-sharing with structural Lu and Yb, likely helped accommodate these REEs in the goethite structure. Incorporation into Fe oxyhydroxides thus potentially fractionates the REEs during weathering associated with formation of lateritic and ion adsorption deposits.

Mergelsberg, Sebastian T. [Pacific Northwest Natio↗
DOE OSTI2025

Study of the Neutrino Magnetic Moment with the NOvA Near Detector

The NuMI Off-Axis νe Appearance (NOvA) Experiment is a long baseline neutrino experiment consisting of two detectors, a Near Detector (ND) at Fermilab in Batavia, IL, and a Far Detector (FD) in Ash River, MN. The ND observes the unoscillated neutrino beam while the FD is able to observe neutrinos which have oscillated. Because the ND does not observe oscillated neutrinos, it works in tandem with the FD to provide control measurements. However, the ND has independent physics goals, such as observing processes which lead to physics beyond the Standard Model (BSM). One such process is the existence of a neutrino magnetic moment. At leading order, neutrinos do not interact electromagnetically, but, by considering higher order perturbative effects, it becomes possible for neutrinos to have an effective coupling with a photon and a non-zero neutrino magnetic moment emerges. Measurement of the neutrino magnetic moment can aid in the process of determining if neutrinos are Dirac or Majorana fermions, as well as provide insights into BSM physics. In this talk, we discuss the NOvA ND’s capabilities for making a direct measurement of the neutrino magnetic moment.

Choate, Sarah [Iowa U.]↗
DOE OSTI2025

Study of the Neutrino Magnetic Moment with the NOvA Near Detector

The NuMI Off-Axis νe Appearance (NOvA) Experiment is a long baseline neutrino experiment consisting of two detectors, a Near Detector (ND) at Fermilab in Batavia, IL, and a Far Detector (FD) in Ash River, MN. The ND observes the unoscillated neutrino beam while the FD is able to observe neutrinos which have oscillated. Because the ND does not observe oscillated neutrinos, it works in tandem with the FD to provide control measurements. However, the ND has independent physics goals, such as observing processes which lead to physics beyond the Standard Model (BSM). One such process is the existence of a neutrino magnetic moment. At leading order, neutrinos do not interact electromagnetically, but, by considering higher order perturbative effects, it becomes possible for neutrinos to have an effective coupling with a photon and a non-zero neutrino magnetic moment emerges. Measurement of the neutrino magnetic moment can aid in the process of determining if neutrinos are Dirac or Majorana fermions, as well as provide insights into BSM physics. For this poster, we present the NOvA ND's capabilities for making a direct measurement of the neutrino magnetic moment as well as the work currently being done to accomplish this.

Choate, Sarah [Iowa U.]↗
DOE OSTI2025

Entrapment Behavior of Solid Surrogate Fission Products at Engineered UN Nano‐Hetero‐Interfaces Within Metallic Nuclear Fuels

Nanometric hetero-interfaces provide a wealth of scientific and engineering opportunities due to their complex and often misunderstood properties that can differ from their respective bulk constituents. In this work, the ability for engineered nanostructures within a bulk U─Mo alloy to arrest simulant fission products is investigated experimentally and computationally. Nanostructured 90 wt% U/ 10 wt% Mo (U-10Mo) with 7.1 at% Nd is consolidated using spark-plasma- sintering (SPS) techniques and is heat-treated at 500 °C under vacuum for 24, 100, 500, and 1000 h. Analysis on the sintered and heat-treated U-10Mo reveals rapid kinetics in Nd diffusion to nanocluster sites, with evidence of Nd diffusion occurring during sintering and during the following heat-treatment. The segregation behavior of Nd at two different U─Mo/UN interfaces is computationally verified using density functional theory (DFT) to reinforce experimental data.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

On the Topotactic Phase Transition Achieving Superconducting Infinite‐Layer Nickelates

Abstract Topotactic reduction is critical to a wealth of phase transitions of current interest, including synthesis of the superconducting nickelate Nd 0.8 Sr 0.2 NiO 2 , reduced from the initial Nd 0.8 Sr 0.2 NiO 3 /SrTiO 3 heterostructure. Due to the highly sensitive and often damaging nature of the topotactic reduction, however, only a handful of research groups have been able to reproduce the superconductivity results. A series of in situ synchrotron‐based investigations reveal that this is due to the necessary formation of an initial, ultrathin layer at the Nd 0.8 Sr 0.2 NiO 3 surface that helps to mediate the introduction of hydrogen into the film such that apical oxygens are first removed from the Nd 0.8 Sr 0.2 NiO 3 / SrTiO 3 (001) interface and delivered into the reducing environment. This allows the square‐planar / perovskite interface to stabilize and propagate from the bottom to the top of the film without the formation of interphase defects. Importantly, neither geometric rotations in the square planar structure nor significant incorporation of hydrogen within the films is detected, obviating its need for superconductivity. These findings unveil the structural basis underlying the transformation pathway and provide important guidance on achieving the superconducting phase in reduced nickelate systems.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Complete resolution across the neodymium/samarium isotopic envelope with a liquid sampling‐atmospheric pressure glow discharge — Orbitrap mass spectrometer

Rationale Nd and Sm isotope ratios play an important role in geological dating and as nuclear forensic signatures; however, the overlap of the respective 144, 148, 150 Nd/Sm isobars requires prior separations to be performed before analysis on typical MS platforms. The work presented here overcomes these isobaric interferences using ultrahigh‐mass resolution to alleviate interference without prior chemical separations. Methods A liquid sampling‐atmospheric pressure glow discharge ion source was coupled to a standard, QExactive Focus Orbitrap mass spectrometer, providing a mass resolution of ~80 k. A Spectroswiss FTMS booster X2 data acquisition package was used to collect extended transients, providing much higher mass resolution; ~230 k and ~600 k are employed here for Nd and Sm isotopes. Results While the standard Orbitrap resolution is far greater than typical “atomic” MS platforms, it was insufficient to alleviate all isobars. The use of a resolution of ~230 k resulted in baseline separation across the entire isotopic envelope for both Nd and Sm. Isotope ratios obtained from Nd:Sm mixtures using high‐resolution were equivalent to those found for individual‐element solutions, while isotope ratios obtained at a resolution of ~80 k (standard for the OEM data system) showed large deviations. Conclusions Use of ultrahigh‐resolution is an attractive alternative to extensive chemical separations to alleviate severe isobaric interferences. Sufficient mass resolution greatly reduces/eliminates the need for sample manipulations (separations) before analysis while reducing costs and total analysis times.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

First-principles investigation of cerium and neodymium diffusion in BCC chromium and vanadium via vacancy-mediated transport

Lanthanide transport plays a crucial role in the performance and longevity of metallic nuclear fuels. This study examines the diffusion behavior of Ce and Nd—two major fission products—in body-centered cubic (BCC) Cr and V, which are potential liner or coating materials for mitigating fuel-cladding chemical interactions (FCCI). Using density functional theory (DFT) calculations and self-consistent mean-field (SCMF) analysis, the vacancy-mediated diffusion coefficients are evaluated. Our findings reveal that Ce and Nd act as oversized solutes and are strongly bound to vacancies in BCC Cr and V, with diffusivities in Cr significantly lower than in V and in hexagonal closed-packed (HCP) Zr, as investigated in our previous work. The activation energies for Ce and Nd diffusion are 3.39 and 3.32 eV, respectively, in BCC Cr, and 2.56 and 2.33 eV, respectively, in BCC V. Analysis of vacancy drag and partial diffusion coefficient ratios indicates a strong tendency for lanthanide enrichment at vacancy sinks in BCC Cr, and to a lesser extent in BCC V, with this effect persisting up to the melting point in Cr and remaining substantial for Nd in V at high temperatures. Under irradiation, the increase in vacancy concentration is expected to enhance lanthanide transport, potentially accelerating interactions at liner-cladding interfaces. Although BCC Cr exhibits relatively low lanthanide diffusivities under equilibrium conditions, the expected segregation tendencies under irradiation suggest that Zr liners may be a more favorable option. Further investigations using rate theory, cluster dynamics, and phase-field modeling are required to quantitatively assess the performance of these materials in reactor environments.

36 - MATERIALS SCIENCE↗
DOE OSTI2026

Optimization of Annealing for WZ-Phase Removal and Densification in Sb-Doped CdSexTe1-x Solar Cells

The impact of high temperature annealing (HTA) treatments on the performance of Sb-doped CdSeTe solar cells containing a CdSe0.25Te0.75/CdTe front stack and a vapor transport (VT) deposited CdTe:Sb absorber was studied. The HTA treatment of the thermally evaporated CdSe0.25Te0.75/CdTe front stack converts the mixed-phase film into a single zinc blende structure through recrystallization of the photo-inactive wurtzite phase. Subsequently, HTA treatment of the full device stack after vapor transport deposition of CdTe:Sb absorber promotes Se-Te intermixing, reduces voids, densifies the full stack and enhances CdTe:Sb grain growth. Comprehensive characterizations revealed that the combined HTA treatments significantly improved film crystallinity, removed the WZ phase in the front stack, enhanced full-stack densification, reduced defect densities, and enhanced carrier dynamics. With HTA treatments, the open-circuit voltage (VOC) of CdSeTe:Sb devices increased from ~ 400 mV to >= 600 mV, and when combined with optimized CdCl2 treatment, VOC reached 849 mV. The net carrier concentrations (NA-ND) of representative devices were NA-ND = 1.5 x 10^15, 1.1 x 10^15, and 3.5 x 10^14 cm-3 for the no-HTA, moderate-HTA, and optimized high-VOC conditions, respectively. Since the highest VOC corresponds to the lowest apparent NA-ND, , which is similar to a Cu-doped-only CdSeTe solar cell (NA-ND ~= 2 x 10^14 cm-3), the data indicate that improved device performance does not result from increased electrically active Sb; instead, it points to structural improvement as the dominant effect of HTA. The findings demonstrate the potential of HTA treatments to improve the structural and electrical properties of CdSeXTe1-X solar cells.

14 SOLAR ENERGY↗
DOE OSTI2025

Near-IR Luminescence Tuning in a Series of Chalcogenophene Carboxylate-Decorated Neodymium Dimers

Here, the solvothermal synthesis of a series of Nd dimers decorated with various chalcogenophene carboxylates and 2,2':6',2"-terpyridine of the general formula, [Nd 2 (µ-XC 5 H 3 O 2 ) 2 (XC 5 H 3 O 2 ) 4 (N 3 C 15 H 11 ) 2 (H 2 O) 2 ] where X = O, S, Se, and Te, is reported. The solid-state structures were characterized using single-crystal X-ray diffraction (scXRD) and all the complexes are isomorphous, despite substitution of the heterocyclic chalcogen; phase purity was confirmed via powder X-ray diffraction (pXRD). Vibrational spectroscopy was collected and correlations between chalcogen identity and the binding strength of the carboxylate groups of the chalcogenophene ligands with each metal center were shown to be independent of chalcogen identity. All four complexes displayed Nd(III)-based near-IR luminescence and exhibited ligand-sensitized emission. Varying the chalcogenophene chromophore enabled tuning of the sensitizing triplet state energy level, as evidenced by an 8-fold increase in the sensitization of the TeCA-decorated dimer relative to the other chalcogenophene congeners. This behavior was rationalized by comparing the Nd(III) acceptor and ligand donor states across the series. The donor triplet state of each ligand was estimated via low-temperature (77 K) phosphorescence measurements from 1:1 mixtures with Gd(III); these were found to be 24,631 cm –1 for furan-2-carboxylic acid (FCA), 23,764 cm –1 for thiophene-2-carboxylic acid (TCA), 22,548 cm –1 for selenophene-2-carboxylic acid (SeCA), and 21,186 cm –1 for tellurophene-2-carboxylic acid (TeCA). The greater sensitization efficiency of TeCA is the result of well-matched ligand donor and metal acceptor levels and thus suppression of nonradiative back-energy transfer. More broadly, triplet energy level information for these ligands serves as a guide for future application to other target metals based on the electronic properties necessary to effect efficient sensitization.

Coordination Chemistry↗
DOE OSTI2026

Magic Diamond: Covalent Bond Formation of Melamine and Other Amines on Nanodiamond Surfaces

High-temperature, high-pressure (HPHT) nanodiamond (ND) hosts nitrogen-vacancy (NV) centers, solid-state qubits that enable room-temperature quantum sensing by all-optical magnetometry, electrometry, and thermometry. However, the covalent surface functionalization of nanoscale diamond remains largely limited to carboxylate-based chemistries. Amine termination is particularly attractive because theoretical studies predict suppression of midgap states and extended electron-spin coherence times. Recently, chemical activation of alcohol-terminated NDs to alkyl bromides (ND-Br) using SOBr2 has enabled nucleophilic substitution through a carbocation intermediate, allowing formation of simple amine terminations. Here, we evaluate whether sterically demanding amines can form covalent diamond−nitrogen bonds on ND-Br surfaces. ND-Br was reacted with branched, linear, and cyclic amines, including polyethylenimine, diethylenetriamine, and melamine. X-ray spectroscopies were used to confirm successful and to probe the resulting electronic structure at the diamond−amine interface. These results expand the chemical toolbox for tuning diamond surface dipoles and electron affinity, providing new pathways for engineering nanodiamond surfaces for quantum sensing and photocatalysis applications.

Amines↗
DOE OSTI2025

Online monitoring of lanthanide species with combined spectroscopy in flowing aqueous aerosol systems

Combined spectroscopic analysis through absorption and laser-induced breakdown spectroscopy (LIBS) was used to monitor Nd and Pr concentrations in a flowing aqueous system. A unique, online sampling approach was employed that allowed for an approximately closed analysis loop of liquids from a reservoir. Absorption spectroscopy was performed with an optical flow cell, and LIBS was performed on an aerosol stream. Multivariate calibrations based on combined absorption and LIBS signals were built for Nd and Pr and then used to monitor concentrations in mixed solutions in a series of spiking tests. In these tests, the concentrations of Nd and Pr in solution were intermittently changed while spectroscopic signals were monitored in real-time. The combined spectroscopic signals and multivariate models were successful in monitoring changing concentrations of lanthanide species with high accuracy and minimal latency. Root-mean squared error of predictions were 0.015 mol L −1 and 0.019 mol L −1 for Nd and Pr respectively, and these lanthanides were able to be monitored to an accuracy of < 0.2 wt%. This work demonstrates both the capabilities of a sampling system for online analysis of liquids and the capabilities of multimodal spectroscopic characterization for real-time, continuous tracking of species in potentially hazardous liquid systems.

absorbance spectroscopy↗