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Tuning the surface states of Fe3O4 nanoparticles for enhanced magnetic anisotropy and induction efficacy
(American Chemical Society, 2025-09-10) Portwin, KA; Galaviz, P; Li, XN; Hao, CY; Smillie, LA; You, MY; Stamper, CJ; Mole, RA; Yu, DH; Rule, KC; Cortie, DL; Cheng, ZX
Magnetite (Fe3O4) nanoparticles are crucial for biomedical applications, including magnetic hyperthermia, targeted drug delivery, and MRI contrast enhancement due to their biocompatibility and unique physicochemical properties. Here, we investigate how surface states influence their induction performance. Heat treatment removes surface water and FeOOH, forming a γ-Fe2O3 shell, as confirmed by synchrotron powder diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and time-of-flight inelastic neutron spectroscopy. AC magnetic susceptibility measurements reveal that this surface modification enhances magnetic anisotropy and reduces the spin relaxation time, leading to a 140% increase in the specific absorption rate. Additionally, the increased anisotropy suppresses the low-temperature clustered spin-glass transition and raises the blocking temperature. These findings highlight surface-state engineering as a powerful approach to optimizing Fe3O4 nanoparticles for biomedical applications. © 2025 American Chemical Society.
Role of finite-temperature dynamics and dispersion interactions on the phonon bandgap in thermoelectric SnSe
(American Physical Society, 2024-09-18) Portwin, KA; Galaviz, P; Stamper, CJ; Kutteh, R; Yu, DH; Cheng, ZX; Cortie, DL; Rule, KC
The low lattice thermal conductivity in tin selenide is key to its excellent thermoelectric properties. The dominant mechanism for this phononic property, however, is debated. Past lattice-dynamic calculations for SnSe consistently predicted the existence of a phonon bandgap, which is puzzling as it has not been observed in spectroscopic experiments and is typically associated with low phonon-scattering rates in contrast to the observed physical properties. In this work, we accurately investigate the size of the phonon bandgap in SnSe using a direct comparison between experimental neutron spectroscopy, lattice-dynamic calculations, and 𝑎⁢𝑏𝑖⁢𝑛⁢𝑖⁢𝑡⁢𝑖⁢𝑜 molecular dynamics. We theoretically investigate the effects of van der Waals interactions in density functional theory calculations using the popular Grimme D2/D3 and semilocal methods and we also assess the effect of finite-temperature driven anharmonicity using Born-Oppenheimer 𝑎⁢𝑏𝑖⁢𝑛⁢𝑖⁢𝑡⁢𝑖⁢𝑜 molecular dynamics. The D2/D3 lattice dynamics calculations, which assume 0 K, predict a phonon bandgap, although the size and structure depends on the details of the van der Waals correction. In contrast, both the experiment and 𝑎⁢𝑏𝑖⁢𝑛⁢𝑖⁢𝑡⁢𝑖⁢𝑜 dynamics identify there is a valley in the density of states at finite temperature, ascribed to strong anharmonicity that shifts specific phonon modes. This finding highlights the need for great care when applying 0 K lattice dynamics and dispersion corrections to SnSe, with general implications for designing thermoelectric materials via computational methods. ©2025 American Physical Society.
Colloidal gold in sulphur and citrate-bearing hydrothermal fluids: an experimental study
(Elsevier, 2019-11) Liu, WH; Chen, M; Yang, Y; Mei, Y; Etschmann, B; Brugger, J; Johannessen, B
The stability of colloidal gold (gold nanoparticles) in sulphur-bearing and citrate-bearing solutions was investigated at temperatures up to 225 °C using Synchrotron X-ray Near-edge Spectroscopy (XANES), and up to 350 °C with a visual check of colour changes. The citrate-based colloidal gold solutions, with or without colloidal silica in the solution, are only stable up to 225 °C. In contrast, the gold colloids in Na2S solutions are not stable upon heating to 150 °C, but stable up to 300 °C when 0.5–1.5 wt% of colloidal silica is present in the solution. The colloidal gold particles started to aggregate and deposit from the solution with the aggregation and growth of silica particles at 350 °C. The concentrations of gold as colloids in the solutions are up to 0.5 mmol (∼95 ppm), more than three orders of magnitude higher than gold solubility as aqueous complexes under the same condition calculated based on available thermodynamic data. These results provide the first evidence that high concentrations of colloidal gold are stable in sulphur-bearing fluids at elevated temperatures (∼300 °C). This implies that the formation of gold colloids is an effective way to concentrate gold in hydrothermal sulphur-bearing fluids to form high-grade gold ores. © 2019 Elsevier B.V.
Klastomycter conodentatus, gen et sp. nov., a small early Permian parareptile with conical teeth from Richards Spur, Oklahoma
(PeerJ, 2024-11-19) Reisz, RR; Rowe, DCT; Bevitt, JJ
A small, pristinely preserved specimen recently collected from the Dolese Brothers limestone quarry near Richards Spur, Oklahoma provides evidence for the presence of a new early Permian parareptile at this locality. The specimen includes an articulated, nearly complete skull roof, and with the right premaxilla, right quadratojugal, most of the right palate, as well as the right epipterygoid and the sphenethmoid preserved inside. Although similar in many respects to the other contemporary parareptiles Acleistorhinus, Delorhynchus and Colobomycter, it can be distinguished from other acleistorhinids by the presence of a number of autapomorphies related to its dentition. Phylogenetic analysis places it closer to Delorhynchus and Colobomycter within Acleistorhinidae than to Acleistorhinus pteroticus. Unique aspects of the present specimen include the pronounced anterior extension of the lacrimal bone, largely homodont dentition composed of simple conical crowns with slight recurvature in the premaxillary and anterior maxillary teeth, and simple conical crowns in posterior maxillary dentition. The discovery of this new parareptile along with the surprisingly large number of acleistorhinids at Richards Spur highlights the importance of the unique fissure and vertical cave system at this site. No other early Permian site has provided such a wide diversity of parareptilian taxa, part of a complex community of terrestrial vertebrates. The present specimen highlights the fine niche partitioning that appears to have been present among reptiles of this region. © 2024 Reisz et al. Distributed under Creative Commons CC-BY-NC 4.0
New material of the ‘microsaur’ Llistrofus from the cave deposits of Richards Spur, Oklahoma and the paleoecology of the Hapsidopareiidae
(PeerJ, 2019-01-25) Gee, BM; Bevitt, JJ; Garbe, U; Reisz, RR
The Hapsidopareiidae is a group of “microsaurs” characterized by a substantial reduction of several elements in the cheek region that results in a prominent, enlarged temporal emargination. The clade comprises two markedly similar taxa from the early Permian of Oklahoma,Hapsidopareion leptonandLlistrofus pricei, which have been suggested to be synonymous by past workers.Llistrofuswas previously known solely from the holotype found near Richards Spur, which consists of a dorsoventrally compressed skull in which the internal structures are difficult to characterize. Here, we present data from two new specimens ofLlistrofus. This includes data collected through the use of neutron tomography, which revealed important new details of the palate and the neurocranium. Important questions within “Microsauria” related to the evolutionary transformations that likely occurred as part of the acquisition of the highly modified recumbirostran morphology for a fossorial ecology justify detailed reexamination of less well-studied taxa, such asLlistrofus. Although this study eliminates all but one of the previous features that differentiatedLlistrofusandHapsidopareion, the new data and redescription identify new features that justify the maintained separation of the two hapsidopareiids.Llistrofuspossesses some of the adaptations for a fossorial lifestyle that have been identified in recumbirostrans but with a lesser degree of modification (e.g., reduced neurocranial ossification and mandibular modification). Incorporating the new data forLlistrofusinto an existing phylogenetic matrix maintains the Hapsidopareiidae’s (Llistrofus+Hapsidopareion) position as the sister group to Recumbirostra. Given its phylogenetic position, we contextualizeLlistrofuswithin the broader “microsaur” framework. Specifically, we propose thatLlistrofusmay have been fossorial but was probably incapable of active burrowing in the fashion of recumbirostrans, which had more consolidated and reinforced skulls.Llistrofusmay represent an earlier stage in the step-wise acquisition of the derived recumbirostran morphology and paleoecology, furthering our understanding of the evolutionary history of “microsaurs.” © Gee et al. Open access - CC BY 4.0.

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