On the possibility of using polycrystalline material in the development of structure-based generic assays

The correlation coefficients calculated between raw powder diffraction profiles can be used to identify ligand-bound/unbound states of lysozyme

Sorption kinetic study of selenite and selenate onto a high and low pressure aged iron oxide nanomaterial

The sorption of selenite (SeO32−) and selenate (SeO42−) onto Fe3O4 nanomaterials produced by non microwave-assisted or microwave-assisted synthetic techniques was investigated through use of the batch technique. The phase of both synthetic nanomaterials was determined to be magnetite by X-ray diffraction. The average grain sizes of non microwave-assisted and microwave-assisted synthetic Fe3O4 were determined to be 27 and 25 nm, respectively through use of the Scherrer\u27s equation. Sorption of selenite was pH independent in the pH range of 2-6, while sorption of selenate decreased at pH 5 and 6. The addition of Cl− had no significant effect on selenite or selenate binding, while the addition of NO3− only affected selenate binding to the microwave assisted Fe3O4. A decrease of selenate binding to both synthetic particles was observed after the addition of SO42− while selenite binding was not affected. The addition of PO43− beginning at concentrations of 0.1 ppm had the most prominent effect on the binding of both selenite and selenate. The capacities of binding, determined through the use of Langmuir isotherm, were found to be 1923 and 1428 mg Se/kg of non microwave-assisted Fe3O4 and 2380 and 2369 mg Se/kg of microwave-assisted Fe3O4 for selenite and selenate, respectively

Ac-Susceptibility Studies of the Energy Barrier to Magnetization Reversal in Frozen Magnetic Nanofluids of Different Concentrations

We used ac-susceptibility to measure the blocking temperature, TB, and energy barrier to the magnetization reversal, EB, of nanomagnetic fluids of different concentrations, c. We collected data on five samples synthesized by dispersing Fe3O4 nanoparticles of average diameter ⟨D⟩ = 8 nm in different volumes of carrier fluid (hexane). We found that TB increases with the increase in c, a behavior predicted by the Dormann–Bessais–Fiorani (DBF) theory. In addition, our observed TB vs. c dependence is excellently described by a power law TB = A∙cγ, with A = 64 K and γ = 0.056. Our data also show that a Néel–Brown activation law τT=τ0exp⁡EBkBT describes the superspin dynamics in the most diluted sample, whereas an additional energy barrier term, Ead, is needed at higher concentrations, according to the DBF model: τT=τrexp⁡EB+EadkBT.  We found EB/kB = 366 K and additional energy barriers Ead/kB that increase linearly with the common logarithm of the volume concentration, from 138 K at c = 8.3 × 10−4% to 745 K at c = 4 × 10−2%. These results add to our understanding of the contributions by different factors to the superspin dynamics. In addition, the quantitative relations that we established between the TB, Ead, and c support the current efforts towards the rational design of functional nanomaterials

Stability of Superprotonic CsH2PO4 Hermetically Sealed in Different Environments

Using powder X-ray diffraction and AC impedance spectroscopy, we have found that the superprotonic CsH2PO4 (CDP) phase is stable at T = 250 °C when sealed in different volumes (15 mL and 50 mL) of dry air or inert gasses. Under these conditions, CDP’s proton conductivity stays constant at 2.5 × 10−2 S·cm−1 for at least 10 h. On the other hand, removing the gas from the chamber leads to a sharp, two-order-of-magnitude drop in the proton conductivity. Our data show no evidence of a self-generated water vapor atmosphere in the chamber, and the gas pressure at T = 250 °C is several orders of magnitude below the pressures previously used to stabilize CDP’s superprotonic phase. These results demonstrate that hermetically sealing CDP in small gas-filled volumes represents a new method to stabilize the superprotonic phase, which opens new paths for large-scale applications of phosphate-based solid acids as fuel cell electrolytes

Evidence of Superspin-Glass Behavior in Zn0.5Ni0.5Fe2O4 Nanoparticles

We have used dc-magnetization and ac-susceptibility to investigate the superspin dynamics in 9 nm average size Zn0.5Ni0.5Fe2O4 magnetic particles at temperatures (T) between 3 and 300 K. Dc-magnetization M versus T data collected in a H = 50 Oe magnetic field using a field-cooled–zero-field-cooled protocol indicate that the onset of irreversibility occurs in the vicinity of 190 K. This is confirmed by M versus H|T hysteresis loops, as well as by frequency- and temperature-resolved ac-susceptibility data. We demonstrate that this magnetic event is not due to the blocking of individual superspins, but can be unequivocally ascribed to their collective freezing in a spin-glass-like fashion. Indeed, the relative variation (per frequency decade) of the in-phase susceptibility peak temperature is ~0.032, critical dynamics analysis of this peak shift yields an exponent zν = 10.0 and a zero-field freezing temperature Tg = 190 K, and, in a magnetic field, Tg(H) is excellently described by the de Almeida–Thouless line δTg = 1 − Tg(H)/Tg ∝ H2/3. In addition, out-of-phase susceptibility versus temperature datasets collected at different frequencies collapse on a universal dynamic scaling curve. Finally, memory imprinting during a stop-and-wait magnetization protocol confirms the collective freezing nature of the state below 190 K

Superspin Relaxation Times in Fe3O4 / Hexane Magnetic Fluids Measured by Frequency-Resolved AC Susceptibility

A properly formatted abstract has been uploaded below. The pasted version is here Superspin relaxation times in Fe3O4 / hexane magnetic fluids measured by frequency-resolved ac susceptibility Joshua Morris^ and Cristian E. Botez* Department of Physics, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968, U.S.A Michael P. Eastman Department of Chemistry, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968, U.S.A We have used frequency-resolved (100 Hz \u3c f \u3c 10,000 Hz) ac magnetic susceptibility measurements to directly determine the Néel and Brown relaxation times in 30-nm-size Fe3O4 / hexane magnetic fluids at temperatures between 200 and 300 K. Our data collected on both powder and magnetic fluid samples allow the separation of the contributions from the Néel and Brown relaxation mechanisms that act concomitantly within the above-mentioned temperature range. At all temperatures we find that the Brown relaxation times (tB) are shorter than their Néel counterparts (tN), evidence that the Brown mechanism yields the major contribution towards the system’s overall superspin dynamics. tB exhibits a steep two-order-of-magnitude decrease upon heating, from tB=1´10-3s at T=237K to tB=1.5´10-5s at T=270K, a behavior mostly driven by the heating-induced reduction of the liquid carrier’s viscosity

Effects Of Zno Nanoparticles In Alfalfa, Tomato, And Cucumber At The Germination Stage: Root Development And X-Ray Absorption Spectroscopy Studies

Past reports indicate that some nanoparticles (NPs) affect seed germination; however, the biotransformation of metal NPs is still not well understood. This study investigated the toxicity on seed germination/root elongation and the uptake of ZnO NPs and Zn2+ in alfalfa (Medicago sativa), cucumber (Cucumis sativus), and tomato (Solanum lycopersicum) seedlings. Seeds were treated with ZnO NPs at 0–1600 mg L–1 as well as 0–250 mg L–1 Zn2+ for comparison purposes. Results showed that at 1600 mg L–1 ZnO NPs, germination in cucumber increased by 10 %, and alfalfa and tomato germination were reduced by 40 and 20 %, respectively. At 250 mg Zn2+ L–1, only tomato germination was reduced with respect to controls. The highest Zn content was of 4700 and 3500 mg kg–1 dry weight (DW), for alfalfa seedlings germinated in 1600 mg L–1 ZnO NPs and 250 mg L–1 Zn2+, respectively. Bulk X-ray absorption spectroscopy (XAS) results indicated that ZnO NPs were probably biotransformed by plants. The edge energy positions of NP-treated samples were at the same position as Zn(NO3)2, which indicated that Zn in all plant species was as Zn(II)

Crystal and magnetic structure of the Ca 3 Mn 2 O 7 Ruddlesden-Popper phase: neutron and synchrotron x-ray diffraction study

Abstract The crystallographic and magnetic structures of Ca 3 Mn 2 O 7 RuddlesdenPopper phase have been determined by a combination of neutron and synchrotron x-ray diffraction. Two-phase behaviour observed at room temperature is attributed to an incomplete structural phase transition. The magnetic structure was solved in the Cm c2 1 Shubnikov group with dominant G-type antiferromagnetic order in the perovskite bilayers. The temperature evolution of the structural and magnetic parameters is presented

An <i>N</i>‑Tethered Uranium(III) Arene Complex and the Synthesis of an Unsupported U–Fe Bond

Amination of 2,2″-dibromo-<i>p</i>-terphenyl with 2,6-diisopropylaniline, through Pd mediated cross coupling, yields the <i>p</i>-terphenyl bis­(aniline) ligand H₂L^Ar. Deprotonation of H₂L^Ar with excess KH generates the dianion [K­(DME)₂]₂L^Ar as a dark red solid. Treatment of [K­(DME)₂]₂L^Ar with UI₃(dioxane)_1.5 produces the mononuclear U­(III) complex L^ArU­(I)­(DME) (<b>1</b>). Subsequent addition of the nucleophilic metal anion [CpFe­(CO)₂]⁻ (Fp^–) gives the bimetallic U­(III) compound L^ArU­(Fp) (<b>2</b>) in modest yield which features a rare instance of an unsupported U–M bond. Inspection of the metrical parameters of the solid-state structures of <b>1</b>·DME and <b>2</b>·0.5DME from X-ray crystallographic analyses show a seemingly η⁶-interaction between the uranium and the terphenyl ligand (<b>1</b>: U1–C_centroid = 2.56 Å; <b>2</b>: U1–C_centroid = 2.45 Å), spatially imposed as a consequence of the anilide <i>N</i>-donor atom coordination. Furthermore, the U–Fe bond length in <b>2</b> (U1–Fe1 = 2.9462(3) Å) is consistent with a metal–metal single bond. Notably, electronic structure analyses by CASPT2 calculations instead suggest that electrostatic, and not covalent, interactions dominate between the U–arene systems in <b>1</b> and <b>2</b> and between the U–Fe bond in the latter