Open Access Publications
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Open access publications by faculty, postdocs, and graduate students in the Department of Chemistry and Biochemistry.
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- ItemSynthesis and Crystal Structure of the Zintl Phases NaSrSb, NaBaSb and NaEuSb(Materials, 2023-02-08) Wang, Yi; Bobev, SvilenThis work details the synthesis and the crystal structures of the ternary compounds NaSrSb, NaBaSb and NaEuSb. They are isostructural and adopt the hexagonal ZrNiAl-type structure (space group P6¯2m; Pearson code hP9). The structure determination in all three cases was performed using single-crystal X-ray diffraction methods. The structure features isolated Sb3– anions arranged in layers stacked along the crystallographic c-axis. In the interstices, alkali and alkaline-earth metal cations are found in tetrahedral and square pyramidal coordination environments, respectively. The formal partitioning of the valence electrons adheres to the valence rules, i.e., Na+Sr2+Sb3–, Na+Ba2+Sb3– and Na+Eu2+Sb3– can be considered as Zintl phases with intrinsic semiconductor behavior. Electronic band structure calculations conducted for NaBaSb are consistent with this notion and show a direct gap of approx. 0.9 eV. Additionally, the calculations hint at possible inverted Dirac cones, a feature that is reminiscent of topological quantum materials.
- ItemDynamic bioinspired coculture model for probing ER+ breast cancer dormancy in the bone marrow niche(Science Advances, 2023-03-08) Pradhan, Lina; Moore, DeVonte; Ovadia, Elisa M.; Swedzinski, Samantha L.; Cossette, Travis; Sikes, Robert A.; van Golen, Kenneth; Kloxin, April M.Late recurrences of breast cancer are hypothesized to arise from disseminated tumor cells (DTCs) that reactivate after dormancy and occur most frequently with estrogen receptor–positive (ER+) breast cancer cells (BCCs) in bone marrow (BM). Interactions between the BM niche and BCCs are thought to play a pivotal role in recurrence, and relevant model systems are needed for mechanistic insights and improved treatments. We examined dormant DTCs in vivo and observed DTCs near bone lining cells and exhibiting autophagy. To study underlying cell-cell interactions, we established a well-defined, bioinspired dynamic indirect coculture model of ER+ BCCs with BM niche cells, human mesenchymal stem cells (hMSCs) and fetal osteoblasts (hFOBs). hMSCs promoted BCC growth, whereas hFOBs promoted dormancy and autophagy, regulated in part by tumor necrosis factor–α and monocyte chemoattractant protein 1 receptor signaling. This dormancy was reversible by dynamically changing the microenvironment or inhibiting autophagy, presenting further opportunities for mechanistic and targeting studies to prevent late recurrence.
- ItemComparing spin injection in Fe75Co25/Bi2Te3 at GHz and optical excitations(Applied Physics Letters, 2023-02-13) Sharma, Vinay; Nepal, Rajeev; Wu, Weipeng; Pogue, E. A.; Kumar, Ravinder; Kolagani, Rajeswari; Gundlach, Lars; Jungfleisch, M. Benjamin; Budhani, Ramesh C.Spin-to-charge conversion (S2CC) processes in thin-film heterostructures have attracted much attention in recent years. Here, we describe the S2CC in a 3D topological insulator Bi2Te3 interfaced with an epitaxial film of Fe75Co25. The quantification of spin-to-charge conversion is made with two complementary techniques: ferromagnetic resonance based inverse spin Hall effect (ISHE) at GHz frequencies and femtosecond light-pulse induced emission of terahertz (THz) radiation. The role of spin rectification due to extrinsic effects like anisotropic magnetoresistance (AMR) and planar Hall effects (PHE) is pronounced at the GHz timescale, whereas the THz measurements do not show any detectible signal, which could be attributed to AMR or PHE. This result may be due to (i) homodyne rectification at GHz, which is absent in THz measurements and (ii) laser-induced thermal spin current generation and magnetic dipole radiation in THz measurements, which is completely absent in GHz range. The converted charge current has been analyzed using the spin diffusion model for the ISHE. We note that regardless of the differences in timescales, the spin diffusion length in the two cases is comparable. Our results aid in understanding the role of spin pumping timescales in the generation of ISHE signals.
- ItemThe use of transmission electron microscopy with scanning mobility particle size spectrometry for an enhanced understanding of the physical characteristics of aerosol particles generated with a flow tube reactor(Aerosol Science and Technology, 2023-02-21) Tackman, Emma C.; Higgins, Devon N.; Kerecman, Devan E.; Ott, Emily-Jean; Johnston, Murray V.; Freedman, Miriam ArakAerosol particles are found throughout the atmosphere with considerable variety in morphological characteristics and chemical composition. Identifying and characterizing these particle attributes is a significant step toward improving our understanding of atmospheric chemistry. Many methods exist for measuring the size and spreading of Aitken mode particles, but there are few studies rigorously comparing the results generated between approaches in this field. Here, we compare two methods for assessing aerosol particles – scanning mobility particle size spectrometry (SMPS) and transmission electron microscopy (TEM). Aitken mode particles consisting of salt seed particles and seed particles coated with α-pinene secondary organic material were produced in a flow tube reactor. The same populations of particles were analyzed using both techniques to facilitate direct comparison. For ammonium sulfate particles impacted onto carbon and Si TEM substrates, diameters increased by +0% to +30% when compared to the suspended electrical mobility diameters, an unexpectedly wide range for a single component system. Coated particles had unpredictable diameter differences, sometimes evaluated at larger and sometimes smaller sizes after impaction when compared to the corresponding SMPS electrical mobility diameter, from −34% to +60%. While all particles were generally round in shape, variation in particle morphology was also observed in coated samples. Between 0% and 98% of particles displayed obvious phase separation suggesting more population-level diversity than expected from these particle generation processes. Characterizing the differences between TEM and SMPS results better elucidates the role of a substrate where present and shows nonequivalence in particle size distributions obtained from different instruments.
- ItemAuthentication of edible oils using an infrared spectral library and digital sample sets: A feasibility study(Journal of Chemometrics, 2023-03-19) Sota-Uba, Isio; White, Collin G.; Booksh, Karl; Lavine, Barry K.A potential method to determine whether two varieties of edible oils can be differentiated by Fourier transform infrared (FTIR) spectroscopy is proposed using digitally generated data of adulterated edible oils from an infrared (IR) spectral library. The first step is the evaluation of digitally blended data sets. Specifically, IR spectra of adulterated edible oils are computed from digitally blending experimental data of the IR spectra of an edible oil and the corresponding adulterant using the appropriate mixing coefficients to achieve the desired level of adulteration. To determine whether two edible oils can be differentiated by FTIR spectroscopy, pure IR spectra of the two edible oils are compared with IR spectra of two edible oils digitally mixed using a genetic algorithm for pattern recognition to solve a ternary classification problem. If the IR spectra of the two edible oils and their binary mixtures are differentiable from principal component plots of the spectral data, then differences between the IR spectra of these two edible oils are of sufficient magnitude to ensure that a reliable classification by FTIR spectroscopy can be obtained. Using this approach, the feasibility of authenticating edible oils such as extra virgin olive oil (EVOO) directly from library spectra is demonstrated. For this study, both digital and experimental data are combined to generate training and validation data sets to assess detection limits in FTIR spectroscopy for the adulterants.