The unique properties of NV centers in diamond nanoparticles enable selective identification within organisms and other complex environmental matrices.

Fluorescence of the negatively charged nitrogen-vacancy (NV − ) center of diamond is sensitive to external electromagnetic fields, lattice strain, and temperature due to the unique triplet configuration of its spin states. Their use in particulate diamond allows for the possibility of localized sensing and magnetic-contrast-based differential imaging in complex environments with high fluorescent background. However, current methods of NV − production in diamond particles are accompanied by the formation of a large number of parasitic defects and lattice distortions resulting in deterioration of the NV − performance. Therefore, there are significant efforts to improve the quantum properties of diamond particles to advance the field. Recently it was shown that rapid thermal annealing (RTA) at temperatures much exceeding the standard temperatures used for NV − production can efficiently eliminate parasitic paramagnetic impurities and, as a result, by an order of magnitude improve the degree of hyperpolarization of 13 C via polarization transfer from optically polarized NV − centers in micron-sized particles. Here, we demonstrate that RTA also improves the maximum achievable magnetic modulation of NV − fluorescence in micron-sized diamond by about 4x over conventionally produced diamond particles endowed with NV − . This advancement can continue to bridge the pathway toward developing nano-sized diamond with improved qualities for quantum sensing and imaging.

Surface patterns over multiple length scales are known to influence various biological processes. Here we report the synthesis and characterization of new, two-component xerogel thin films derived from carboxyethylsilanetriol (COE) and tetraethoxysilane (TEOS). Atomic force microscopy (AFM) reveals films surface with branched and hyper branched architectures that are ∼2 to 30 μm in diameter, that extend ∼3 to 1300 nm above the film base plane with surface densities that range from 2 to 77% surface area coverage. Colocalized AFM and Raman spectroscopy show that these branched structures are COE-rich domains, which are slightly stiffer (as shown from phase AFM imaging) and exhibit lower capacitive force in comparison with film base plane. Raman mapping reveals there are also discrete domains (≤300 nm in diameter) that are rich in COE dimers and densified TEOS, which do not appear to correspond with any surface structure seen by AFM.

Functionalization of diamond surfaces with TEMPO and other surface paramagnetic species represents one approach to the implementation of novel chemical detection schemes that make use of shallow quantum color defects such as silicon-vacancy (SiV) and nitrogen-vacancy (NV) centers. Yet, prior approaches to quantum-based chemical sensing have been hampered by the absence of high-quality surface functionalization schemes for linking radicals to diamond surfaces. Here, we demonstrate a highly controlled approach to the functionalization of diamond surfaces with carboxylic acid groups via all-carbon tethers of different lengths, followed by covalent chemistry to yield high-quality, TEMPO-modified surfaces. Our studies yield estimated surface densities of 4-amino-TEMPO of approximately 1.4 molecules nm −2 on nanodiamond (varying with molecular linker length) and 3.3 molecules nm −2 on planar diamond. These values are higher than those reported previously using other functionalization methods. The ζ-potential of nanodiamonds was used to track reaction progress and elucidate the regioselectivity of the reaction between ethenyl and carboxylate groups and surface radicals.

When exposed to environmental conditions, LCO can release Co cations, a known toxicant. In this study, we build on previous work (Bennett et al., Environ. Sci. Technol., 52, 5792-5802, 2018, Bennett et al., Inorg. Chem., 57, 13300-13311, 2018) using theory and modeling to understand the thermodynamic driving forces of ion release in water. We assess how the calculated predictions for ion release depend on aspects of the structural surface model. For example, we vary the number of atomic layers used to form the slab, we explore different surface terminations and hydroxyl group coverages, and we vary the periodic in-plane supercell to assess how ion release depends on the density of formed vacancies. We also benchmark the DFT + Thermodynamics modeling across a range of computational factors such as the choice of exchange correlation functional and pseudopotential type. Such assessment is critical, as there is no direct experimental information for comparison. We devise a generalizable scheme for predicting a threshold pH at which Co release from LCO becomes favorable. We put forward that this scheme could provide information about how much Co is released from LCO under variable pH conditions, and could therefore be used to inform macroscopic contaminant fate models.

The Kake War of 1869 was a US Army altercation with the Tlingit Indians of southeast Alaska. In this conflict, the Army's gunship attacked three Kéex' Kwáan Tlingit civilian villages in midwinter, although no active Tlingit resistance was mounted. The Army's intention was to allow starvation and nature's elements to kill the Tlingit survivors of the attack. The conflict transpired fifteen months after Russia sold Alaska to the United States and as the US Army was dispatched to Alaska to oversee its resources, lands, and indigenous population—an undertaking resisted by the Tlingit Indians. In part, the conflict transpired because the two nations, the United States and the Tlingit people, refused to acknowledge each other's claims to Alaskan land and legal systems. A study of the Kake War documents the role of indigenous legal systems in dealing with governing officials, issues of transnational contacts between indigenous people and colonial governments, the dynamic decisions that native leaders made in difficult situations, and the importance of indigenous oral histories in documenting the past.

Molten salts have found use as solvents in numerous applications including nuclear reactors, batteries, and the extraction and purification of various metals. Unfortunately, understanding of the chemistry of molten salt solutions is limited. In this presentation we explore the use of molten salts as a testbed for understanding both outer and inner coordination sphere effects on dissolved metal ions. The electron transfer reactions available to lanthanides (Eu3+, Sm3+, and Yb3+) and actinides (U3+, U4+, and Th4+) were explored in a series of alkali and alkaline earth halide salts. We present electrochemical data that demonstrate significant shifts in the reduction potentials of these metal ions as a function of the anion and cation identities of the molten salt solvent. We hypothesize that effects on the reduction potential of these metals come from two sources: (1) the primary coordination sphere and (2) the secondary coordination sphere. The influence from the primary coordination sphere is dominated by the degree of covalency in the coordination bonds between the Lnn+ and Ann+ cations and the molten salt anions. The influence of the secondary coordination sphere is dominated by the electron-withdrawing character of the salt cations. EXAFS data and computational results that support these hypotheses are presented. Further, we provide insight into electrodeposition of the An0 metals under these conditions and highlight temperature and molten salt effects that influence these electrodepositions. Specifically, we propose that increased mobility of solid-state atoms at high temperature (> 800°C) influence the properties of electrodeposited metals.

When exposed to environmental conditions, LCO can release Co cations, a known toxicant. In this study, we build on previous work (Bennett et al., Environ. Sci. Technol., 52, 5792-5802, 2018, Bennett et al., Inorg. Chem., 57, 13300-13311, 2018) using theory and modeling to understand the thermodynamic driving forces of ion release in water. We assess how the calculated predictions for ion release depend on aspects of the structural surface model. For example, we vary the number of atomic layers used to form the slab, we explore different surface terminations and hydroxyl group coverages, and we vary the periodic in-plane supercell to assess how ion release depends on the density of formed vacancies. We also benchmark the DFT + Thermodynamics modeling across a range of computational factors such as the choice of exchange correlation functional and pseudopotential type. Such assessment is critical, as there is no direct experimental information for comparison. We devise a generalizable scheme for predicting a threshold pH at which Co release from LCO becomes favorable. We put forward that this scheme could provide information about how much Co is released from LCO under variable pH conditions, and could therefore be used to inform macroscopic contaminant fate models.