Spin driven emergent antiferromagnetism and metal insulator transition in nanoscale p-Si

The entanglement of the charge, spin and orbital degrees of freedom can give rise to emergent behavior especially in thin films, surfaces and interfaces. Often, materials that exhibit those properties require large spin orbit coupling. We hypothesize that the emergent behavior can also occur due to spin, electron and phonon interactions in widely studied simple materials such as Si. That is, large intrinsic spin-orbit coupling is not an essential requirement for emergent behavior. The central hypothesis is that when one of the specimen dimensions is of the same order (or smaller) as the spin diffusion length, then non-equilibrium spin accumulation due to spin injection or spin-Hall effect (SHE) will lead to emergent phase transformations in the non-ferromagnetic semiconductors. In this experimental work, we report spin mediated emergent antiferromagnetism and metal insulator transition in a Pd (1 nm)/Ni81Fe19 (25 nm)/MgO (1 nm)/p-Si (~400 nm) thin film specimen. The spin-Hall effect in p-Si, observed through Rashba spin-orbit coupling mediated spin-Hall magnetoresistance behavior, is proposed to cause the spin accumulation and resulting emergent behavior. The phase transition is discovered from the diverging behavior in longitudinal third harmonic voltage, which is related to the thermal conductivity and heat capacity.Comment: 34 pages, Physica Status Solidi B- Physics, 201

Ionic Liquids: New Forms of Active Pharmaceutical Ingredients with Unique, Tunable Properties

This Review aims to summarize advances over the last 15 years in the development of active pharmaceutical ingredient ionic liquids (API-ILs), which make up a prospective game-changing strategy to overcome multiple problems with conventional solid-state drugs, for example, polymorphism. A critical part of the present Review is the collection of API-ILs and deep eutectic solvents (DESs) prepared to date. The Review covers rules for rational design of API-ILs and tools for API-IL formation, syntheses, and characterization. Nomenclature and ionic speciation, and the confusion that these may cause, are highlighted, particularly for speciation in both ILs and DESs of intermediate ionicity. We also highlight in vivo and in vitro pharmaceutical activity studies, with differences in pharmacokinetic/pharmacodynamic depending on ionicity of API-ILs. A brief overview is provided for the ILs used to deliver drugs, and the Review concludes with key prospects and roadblocks in translating API-ILs into pharmaceutical manufacturing

Isolation of Uranyl Dicyanamide Complexes from N‑Donor Ionic Liquids

An ionic liquid (IL) approach for soft-donor f-element chemistry has been demonstrated by the isolation of several new uranyl dicyanamide complexes through reactions of UO₂(NO₃)₂·6H₂O with dicyanamide ([N­(CN)₂]⁻)-containing ILs. The [N­(CN)₂]⁻ ions are able to rapidly substitute uranium’s O-donor ligands, as evidenced by single-crystal X-ray diffraction studies on two anhydrous adducts of UO₂(NO₃)₂ with [N­(CN)₂]⁻ ILs as well as by IR and NMR spectroscopic studies on solutions of UO₂(NO₃)₂ in these ILs. By contrast, the slow reaction of UO₂(OAc)₂·2H₂O with a nitrile-functionalized imidazolium dicyanamide IL in solvent and the reaction of UO₂(NO₃)₂·6H₂O with NaN­(CN)₂ at elevated temperature resulted in irreversible hydrolysis. The reaction of UO₂SO₄ with [N­(CN)₂]⁻ ions in an acidified aqueous solution resulted in the crystallization of a [UO₂]²⁺ complex with biuret, a N­(CN)₂]⁻ hydrolysis product. [N­(CN)₂]⁻ ions in the form of ILs react rapidly with [UO₂]²⁺ at room temperature, allowing ligand substitution with [N­(CN)₂]⁻ to out-compete the slower hydrolysis reaction, enabling the isolation of uranyl dicyanamide complexes and challenging assumptions regarding the affinity of uranium for O-donors

Lanthanide complexes with zwitterionic amidoximes stabilized by noncoordinating water molecules^*

<p>We present the first structural report of lanthanides complexed with free amidoxime ligands as part of our ongoing research effort to understand the interactions of amidoximes with metal ions in seawater. Three isomorphous lanthanide complexes with acetamidoxime (AcAO) having the formula Ln₂(NO₃)₆(AcAO)₃(OH₂)₃·3H₂O (Ln = Pr³⁺, Nd³⁺, Gd³⁺) have been crystallized and structurally characterised. Notably, the AcAO ligands coordinate in a bridging mode as zwitterions, which creates pre-organised hydrogen bonding cavities into which water molecules are incorporated. Charge-assisted hydrogen bonds to these water molecules appear to stabilize the zwitterionic form and thus the overall complex, underscoring the importance of supramolecular phenomena and overall complex geometry on the relative stability of amidoxime complexes. This has implications for controlling their selectivity towards metal ions.</p

Oxygen Enhances Polyoxometalate-based Catalytic Dissolution and Delignification of Woody Biomass in Ionic Liquids

Complete dissolution and over 90% delignification of Southern yellow pine (<0.125 mm) can be achieved in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C₂mim]­[OAc]) at 110 °C for 6 h by the catalytic action of polyoxometalate in the presence of an appropriate O₂ feed. Cellulose-rich materials (CRMs), or pulps, and hemicellulose with a limited lignin content and free lignin were subsequently recovered by adding antisolvents to the IL solution, followed by filtration. Comparison of wood processing in [C₂mim]­[OAc]/POM with or without O₂ revealed that the presence of oxygen can greatly facilitate the dissolution, delignification, separation of hemicellulose, and oxidation of lignin. The main products from lignin oxidation were extracted from the IL using benzene and then tetrahydrofuran, and were shown by gas chromatography−mass spectrometry (GC–MS) to be methyl vanillate, acetovanillone, vanillic acid, methyl 3-(3-methoxy-4-hydroxyphenyl) propionate, and methyl 4-hydroxybenzoate. This study suggests that treating wood with a [C₂mim]­[OAc]/POM/O₂ system could be a viable strategy to separate wood components with high efficiency and obtain cellulose with high purity for materials or biorefinery applications, particularly those that desire smaller lignin oxidation fragments for further processing

Stripping Uranium from Seawater-Loaded Sorbents with the Ionic Liquid Hydroxylammonium Acetate in Acetic Acid for Efficient Reuse

A new stripping and recovery process was developed to harvest the uranium recovered from seawater with amidoxime-functionalized polyethylene fiber sorbents and allow reuse of the sorbent without loss of capacity and without the need to recondition the sorbent before reuse. Hydroxylammonium acetate ([NH₃OH]­[OAc])/aqueous acetic acid (AcOH) solutions were used as weakly acidic stripping agents and the stripped uranium as a soluble acetate was further immobilized on shrimp shells. These solutions also stripped the vanadium and other metal ions coadsorbed, which reduce capacity through competition with uranium for sorbent binding and can resist stripping even by strong acids. [NH₃OH]­[OAc]/AcOH was found to allow recovery of more than 85% of the uranium although at a substantially longer time than the current 0.5 M HCl-stripping solutions, (less than 12 h vs 48–72 h, respectively); however, the use of HCl severely compromises the capacity of the sorbent in subsequent reuse (a 50% lost was observed on the third reuse of the fiber). Both [NH₃OH]­[OAc] and the acetic acid were necessary to achieve high uranium recovery without sacrificing the sorbent’s capacity on reuse. The ability to reuse the sorbent without pretreatment and with minimal capacity loss could be an important step toward making the extraction of uranium from seawater energy-efficient and economically viable

Measuring the Purity of Chitin with a Clean, Quantitative Solid-State NMR Method

Chitin is a versatile biopolymer which can be extracted directly from biomass and used for the preparation of high value materials, but such materials often require high-purity chitin. However, complete removal of proteinaceous material from chitin, which is obtained from biomass sources, can be difficult to determine. Here we report a quick, nondestructive method to measure chitin content using solid-state multiCP ¹³C NMR, which requires only 105 min and allows for recovery of the sample. A calibration curve was constructed from spectra of mass-based mixtures of commercial chitin and bovine serum albumin protein. This allowed for the quantification of chitin content (and therefore purity) in both chitinous biomass and extracted chitin samples in a quick, clean, nondestructive manner that agreed with measurements made by the method of Black and Schwartz, within the error of each of the methods

Singlet Oxygen Production and Tunable Optical Properties of Deacetylated Chitin-Porphyrin Crosslinked Films

The increasing need for biocompatible materials as supports to immobilize photosensitizer molecules for photodynamic therapy (PDT), led us to investigate the use of chitin as a support for 4,4′,4″,4‴-(porphine-5,10,15,20-tetrayl)­tetrakis­(benzoic acid) (mTCPP) for singlet oxygen production. Chitin was first extracted from shrimp shells using the ionic liquid 1-ethyl-3-methyl-imidazolium acetate ([C₂mim]­[OAc]), coagulated as a floc into water, and then deacetylated to varying degrees of deacetylation using 4 M NaOH. The deacetylated chitin (DA-chitin) was dissolved in [C₂mim]­[OAc] and mTCPP was covalently attached by reaction between the amino groups of DA-chitin and the carboxyl groups of mTCPP using <i>N</i>-(3-(dimethylamino)­propyl)-<i>N</i>′-ethylcarbodiimide hydrochloride (EDC) and <i>N</i>-hydroxysuccinimide (NHS) as activators. The resulting composite polymers were cast as a film and coagulated with water to remove IL and excess reagents, resulting in homogeneous DA-chitin/mTCPP films. Attempts to prepare films by coagulation from a solution containing chitin and mTCPP to physically entrap the porphyrin, resulted in aggregation of mTCPP in the film. The DA-chitin/mTCPP films had strong optical absorbance and their absorbance intensity could be tuned by changing the mTCPP content and degrees of deacetylation of DA-chitin in a predictive manner. In addition, metal ions (Cu²⁺, Zn²⁺, Gd³⁺, and Fe³⁺) could be easily chelated into the DA-chitin/mTCPP films through mixing metal salt solutions with the films and heating. After chelating metal ions, optical properties, such as absorption region and intensities, of the films changed, suggesting chelating metal ions could tune their optical properties. Moreover, the DA-chitin/mTCPP films could generate singlet oxygen under light irradiation and, hence, might serve as a photosensitizer in PDT. The methodology used in this study is also applicable for developing other functional biomaterial devices

Nonaborane and Decaborane Cluster Anions Can Enhance the Ignition Delay in Hypergolic Ionic Liquids and Induce Hypergolicity in Molecular Solvents

The dissolution of <i>nido</i>-decaborane, B₁₀H₁₄, in ionic liquids that are hypergolic (fuels that spontaneously ignite upon contact with an appropriate oxidizer), 1-butyl-3-methylimidazolium dicyanamide, 1-methyl-4-amino-1,2,4-triazolium dicyanamide, and 1-allyl-3-methylimidazolium dicyanamide, led to the <i>in situ</i> generation of a nonaborane cluster anion, [B₉H₁₄]⁻, and reductions in ignition delays for the ionic liquids suggesting salts of borane anions could enhance hypergolic properties of ionic liquids. To explore these results, four salts based on [B₁₀H₁₃]⁻ and [B₉H₁₄]⁻, triethylammonium <i>nido</i>-decaborane, tetraethylammonium <i>nido</i>-decaborane, 1-ethyl-3-methylimidazolium <i>arachno</i>-nonaborane, and <i>N</i>-butyl-<i>N</i>-methyl-pyrrolidinium <i>arachano</i>-nonaborane were synthesized from <i>nido</i>-decaborane by reaction of triethylamine or tetraethylammonium hydroxide with nido-decaborane in the case of salts containing the decaborane anion or via metathesis reactions between sodium nonaborane (Na­[B₉H₁₄]) and the corresponding organic chloride in the case of the salts containing the nonaborane anion. These borane cluster anion salts form stable solutions in some combustible polar aprotic solvents such as tetrahydrofuran and ethyl acetate and trigger hypergolic reactivity of these solutions. Solutions of these salts in polar protic solvents are not hypergolic