Pure Amorphous Research Articles

Pure Amorphous and Ultrathin Phosphate Layer with Superior Ionic Conduction for Zinc Anode Protection.

Fast and uniform ion transport within the solid electrolyte interphase (SEI) is considered a crucial factor for ensuring the long-term stability of metal electrodes. In this study, we present the fabrication of ultrathin artificial interphases consisting of a zinc phosphate nanofilm with pure amorphous characteristics and a surfactant overlayer. The thickness of the interphases can be precisely controlled within the range of a few tens of nanometers. We explore the impact of artificial SEI structure, including thickness and crystallinity, on its protective capabilities. The pure amorphous phosphate layer with optimized nanoscale thickness is found to provide an abundance of short and isotropic ion migration pathways and a low diffusion energy barrier. These features facilitate rapid and homogeneous Zn2+ transportation, resulting in compact and planar zinc deposition. Meanwhile, the hydrophobic alkyl moieties of the overlayer prevent disassociation of water at the interface. As a result, this nanofilm endures ultralong cycling stability with a low overpotential and enables high Zn plating/stripping reversibility. The Zn||MnO2 full cell shows a stable cycle life for 700 cycles under practical conditions of lean electrolyte, high areal capacity cathode, and limited Zn excess. These findings provide insights into the design and optimization of SEI layers for protection of metal anodes.

A Comparative Study of the Pharmaceutical Properties between Amorphous Drugs Loaded-Mesoporous Silica and Pure Amorphous Drugs Prepared by Solvent Evaporation.

The formulation of poorly water-soluble drugs is one of the main challenges in the pharmaceutical industry, especially in the development of oral dosage forms. Meanwhile, there is an increase in the number of poorly soluble drugs that have been discovered as new chemical entities. It was also reported that the physical transformation of a drug from a crystalline form into an amorphous state could be used to increase its solubility. Therefore, this study aims to evaluate the pharmaceutical properties of amorphous drug loaded-mesoporous silica (MPS) and pure amorphous drugs. Ritonavir (RTV) was used as a model of a poorly water-soluble drug due to its low recrystallization tendency. RTV loaded-MPS (RTV/MPS) and RTV amorphous were prepared using the solvent evaporation method. Based on observation, a halo pattern in the powder X-ray diffraction pattern and a single glass transition (Tg) in the modulated differential scanning calorimetry (MDSC) curve was discovered in RTV amorphous, indicating its amorphization. The Tg was not detected in RTV/MPS, which showed that the loading RTV was completed. The solid-state NMR and FT-IR spectroscopy also showed the interaction between RTV and the surface of MPS in the mesopores. The high supersaturation of RTV was not achieved for both RTV/MPS and the amorphous state due to its strong interaction with the surface of MPS and was not properly dispersed in the medium, respectively. In the dissolution test, the molecular dispersion of RTV within MPS caused rapid dissolution at the beginning, while the amorphous showed a low rate due to its agglomeration. The stability examination showed that the loading process significantly improved the physical and chemical stability of RTV amorphous. These results indicated that the pharmaceutical properties of amorphous drugs could be improved by loaded-MPS.

Injection-Molded Coamorphous Tablets: Analysis of Intermolecular Interaction and Crystallization Propensity.

The processing steps involved in converting from a powder to a tablet entail numerous operations in a which the coamorphous system is recrystallized and dissociated easily. This research focused on (i) a single-step preparation of a coamorphous tablet during injection molding (IM) from the bulk powder, and (ii) a mechanistic characterization of the coamorphous formulation. We selected several organic acids [citric acid, succinic acid, tartaric acid, and malic acid] in an effort to compound with basic loratadine (a poorly water-soluble drug). Loratadine-acids coamorphous tablets were produced via an IM process, and the dissolution was more enhanced than in the pure loratadine amorphous. The interaction was analyzed by FT-IR and terahertz spectroscopies. Each tablet was stored at 40°C/75%RH, and then XRD patterns were acquired at the desired timepoints. In summary, loratadine exhibited ionic interaction with each acid, and the physical stability of the coamorphous tablet was in proportion to the loratadine-acids interaction strength. Terahertz spectra detected the molecular mobility, which plays an important role in the crystallization propensity of a coamorphous system. This understanding offers a framework for robust coamorphous tablet formulation using the IM methodology.

Preparation of Pure Amorphous As2S3 Films of a Stoichiometric Composition

The results of studying the composition of arsenic trisulphide (As2S3) films obtained by adding finely dispersed copper or silver powders to the starting materials for sputtering or by using triple compositions As–S–As and As–S–Cu are presented. The issues of preserving the composition of the films obtained and the degree of their purity are discussed.

Ultrafast, Scale-Up Synthesis of Pure and Stable Amorphous Carbonate Mineral Nanoparticles

As important precursors of crystalline phases, amorphous phases of minerals, especially carbonate-based minerals, have been attracting more and more interest in fundamental research and materials chemistry, as well as industrial applications. However, it is still challenging to largely and rapidly synthesize stable amorphous carbonate minerals without the assistance of stabilizers. In this paper, we report an ultrafast method for the high-yield, scale-up synthesis of amorphous carbonate mineral nanoparticles (CaCO3, MgCO3, SrCO3, and their hybrids) within 1 min through the fast diffusion of high-pressure carbon dioxide into ethanol. The present strategy not only allows for the massive production of pure and stable amorphous carbonates but also shows great potential in industrial uses like water treatment.

New Polymorphic Forms of Pemetrexed Diacid and Their Use for the Preparation of Pharmaceutically Pure Amorphous and Hemipentahydrate Forms of Pemetrexed Disodium.

The preparation of stable amorphous pemetrexed disodium of pharmaceutical purity as well as the process optimization for the preparation of the hemipentahydrate form of pemetrexed disodium are described. Analytical methods for the polymorphic and chemical purity studies of pemetrexed disodium and pemetrexed diacid forms were developed. The physicochemical properties of the amorphous and hydrate forms of pemetrexed disodium, as well as new forms of pemetrexed diacid (a key synthetic intermediate) were studied by thermal analysis and powder X-ray diffraction. High-performance liquid chromatography and gas chromatography methods were used for the chemical purity and residual solvents determination. In order to study the polymorphic and chemical stability of the amorphous and hemipentahydrate forms, a hygroscopicity test (25 °C, 80% RH) was performed. Powder diffraction and high-performance liquid chromatography analyses revealed that the amorphous character and high chemical purity were preserved after the hygroscopicity test. The hemipentahydrate form transformed completely to the heptahydrate form of pemetrexed disodium. Both pemetrexed disodium forms were produced with high efficiency and pharmaceutical purity in a small commercial scale. Amorphous pemetrexed disodium was selected for further pharmaceutical development. Two new polymorphs (forms 1 and 2) of pemetrexed diacid were used for the preparation of high purity amorphous pemetrexed disodium.

Influence of Deposition Time on Amorphous Carbon Thin Films Performance with Aerosol-Assisted Chemical Vapor Deposition

Pure amorphous Carbon (a-C) thin films had been deposited by Aerosol-Assisted CVD (AACVD) onto glass substrate in Argon atmosphere. The camphor oil was chosen as the carbon precursor to prepare the a-C thin films with the deposition time of 15 minutes, 30 minutes, 45 minutes, 60 minutes and 75 minutes. The electrical, optical and structural properties of the deposited a-C were discussed by using the current-voltage solar simulator system, UV-Vis-Nir spectrophotometer and Raman spectroscope respectively. For the electrical characterization, the samples showed the photoresponse performance when being illuminated under AM 1.5 illuminations: 100 mW/cm2, 25°C. Transmittance value for the a-C thin films was also considered high ~80% and the structural analysis by using Raman spectroscope exhibit two main peaks known as the D-peak and G-peak which is typical for the a-C.

All-Atom Molecular Dynamics Simulation of Temperature Effects on the Structural, Thermodynamic, and Packing Properties of the Pure Amorphous and Pure Crystalline Phases of Regioregular P3HT

Molecular dynamics simulations have been carried out to probe chain self-organization and structure in regioregular poly-3-hexylthiophene (Rr-P3HT). Taking into account recent experimental findings that provide evidence for a semicrystalline ordering in P3HT where crystalline lamellae are periodically separated by interlamellar amorphous zones, we have separately simulated the pure crystalline and the pure amorphous phases of Rr-P3HT, and studied the dependence of their conformational and configurational properties on temperature (from 225 to 600 K). All simulations have been carried out with the very accurate, all-atom Dreiding force-field. In the pure crystalline phase, the system is found to adopt a noninterdigitated and tilted structure irrespective of temperature and chain molecular weight (Mw) consistent with the results of XRD measurements and other theoretical works. Increasing the temperature did not seem to dramatically affect the interchain distance inside the crystal. Temperature therefore sho...

Off-Stoichiometry Spectroscopic Investigations of Pure Amorphous Silica and N-Doped Silica Thin Films

Cathodoluminescence spectroscopy and X-ray photoelectron spectroscopy were concurrently used to investigate the local physicochemical nature of the amorphous lattice in pure SiO2 and N-doped SiO2 thin films prepared by radiofrequency magnetron sputtering (the latter samples deposited under a set of different conditions of N2 partial pressure). The main aim of this investigation was twofold: (i) to extend our knowledge of the physical and chemical structure of SiO2 films and (ii) to explore our capacity of manipulating, fine tuning, and measuring their stoichiometry characteristics. The presence of nitrogen atoms in the amorphous host structure was confirmed to significantly affect the formation of oxygen-deficient centers, nonbridging oxygen hole centers, and other kinds of defect complexes. The main challenge here was to relate the variations in type and concentration of these peculiar defects to the processing conditions and to the amount of nitrogen incorporated in the SiO2 amorphous matrix. The evolut...

Oxidative Stress Induced by Pure and Iron-Doped Amorphous Silica Nanoparticles in Subtoxic Conditions

Amorphous silica nanoparticles (SiO₂-NPs) have found broad applications in industry and are currently intensively studied for potential uses in medical and biomedical fields. Several studies have reported cytotoxic and inflammatory responses induced by SiO₂-NPs in different cell types. The present study was designed to examine the association of oxidative stress markers with SiO₂-NP induced cytotoxicity in human endothelial cells. We used pure monodisperse amorphous silica nanoparticles of two sizes (16 and 60 nm; S16 and S60) and a positive control, iron-doped nanosilica (16 nm; SFe), to study the generation of hydroxyl radicals (HO·) in cellular-free conditions and oxidative stress in cellular systems. We investigated whether SiO₂-NPs could influence intracellular reduced glutathione (GSH) and oxidized glutathione (GSSG) levels, increase lipid peroxidation (malondialdehyde (MDA) and 4-hydroxyalkenal (HAE) concentrations), and up-regulate heme oxygenase-1 (HO-1) mRNA expression in the studied cells. None of the particles, except SFe, produced ROS in cell-free systems. We found significant modifications for all parameters in cells treated with SFe nanoparticles. At cytotoxic doses of S16 (40-50 μg/mL), we detected weak alterations of intracellular glutathione (4 h) and a marked induction of HO-1 mRNA (6 h). Cytotoxic doses of S60 elicited similar responses. Preincubation of cells being exposed to SiO₂-NPs with an antioxidant (5 mM N-acetylcysteine, NAC) significantly reduced the cytotoxic activity of S16 and SFe (when exposed up to 25 and 50 μg/mL, respectively) but did not protect cells treated with S60. Preincubation with NAC significantly reduced HO-1 mRNA expression in cells treated with SFe but did not have any effect on HO-1 mRNA level in cell exposed to S16 and S60. Our study demonstrates that the chemical composition of the silica nanoparticles is a dominant factor in inducing oxidative stress.

Amorphous Drug-PVP Dispersions: Application of Theoretical, Thermal and Spectroscopic Analytical Techniques to the Study of a Molecule With Intermolecular Bonds in Both the Crystalline and Pure Amorphous State

We report the case of BMS-488043-PVP solid dispersions which when analysed using modulated DSC showed compliance with the Gordon-Taylor model, confirming ideal mixing behaviour of the two components. The nature or presence of stabilising interactions between drug and PVP could not be confirmed using this technique. Use of FT-IR, Raman and solid-state NMR spectroscopy confirmed the presence of stabilising hydrogen bond interactions between the drug and PVP. Similar interactions are present as intermolecular bonds in the crystalline and pure amorphous drug system. The Gordon-Taylor equation, as it is not predictive of the presence of intermolecular bonds such as hydrogen bonding in an amorphous dispersion, may underestimate the likely physical stability of solid dispersions which are produced and stabilised by these interactions.

In Silico Prediction of Drug Solubility. 3. Free Energy of Solvation in Pure Amorphous Matter

The solubility of drugs in water is investigated in a series of papers. In this work, we address the process of bringing a drug molecule from the vapor into a pure drug amorphous phase. This step enables us to actually calculate the solubility of amorphous drugs in water. In our general approach, we, on one hand, perform rigorous free energy simulations using a combination of the free energy perturbation and thermodynamic integration methods. On the other hand, we develop an approximate theory containing parameters that are easily accessible from conventional Monte Carlo simulations, thereby reducing the computation time significantly. In the theory for solvation, we assume that DeltaG* = DeltaGcav + ELJ + EC/2, where the free energy of cavity formation, DeltaGcav, in pure drug systems is obtained using a theory for hard-oblate spheroids, and ELJ and EC are the Lennard-Jones and Coulomb interaction energies between the chosen molecule and the others in the fluid. The theoretical predictions for the free energy of solvation in pure amorphous matter are in good agreement with free energy simulation data for 46 different drug molecules. These results together with our previous studies support our theoretical approach. By using our previous data for the free energy of hydration, we compute the total free energy change of bringing a molecule from the amorphous phase into water. We obtain good agreement between the theory and simulations. It should be noted that to obtain accurate results for the total process, high precision data are needed for the individual subprocesses. Finally, for eight different substances, we compare the experimental amorphous and crystalline solubility in water with the results obtained by the proposed theory with reasonable success.

Test of the adiabatic nucleation model in SeTe and GeSnSe glasses

Se1−YTeY and Ge1−YSnYSe2.5 glasses, with compositions Y⩽0.5 and Y⩽0.6 respectively, are investigated. These glasses show a glass transition temperature (Tg) above the stability limit, indicated by the Adiabatic Nucleation Model (ANM). This effect has to be so because, otherwise, when cooled, these undercooled liquids would crystallize by generalized nucleation near the stability limit and no Tg could be observed. This shows that Se1−YTeY glasses for Y<0.5 are structurally stable. Limiting cases are pure Te and Se50Te50, which have Tg′’s on the stability limit. Pure amorphous Te has to be obtained by fast quenching techniques, where the effective (fast quenching) Tg* is higher and Se50Te50 tends to crystallize easily.

Correlation between microstructure, particle size, dielectric constant, and electrical resistivity of nano-size amorphous SiO 2 powder

Pure amorphous SiO 2 powder with nanometer size particles was exposed to various heat treatments up to 1200°C. The microstructure, particle size, dielectric constant and electrical resistivity of the powder were characterized after each heat treatment. It was found that the dielectric constant of the powder is higher compared to that of amorphous SiO 2 thin films. This enhancement is correlated with higher density of Si dangling bonds, which contribute to the polarization of the material. A major decrease in the dielectric constant takes place during heating up to 600°C where neither growth nor crystallization of the particles occur but only pronounced reduction in the density of the Si dangling bonds is observed. Pronounced growth and initial crystallization to a cristobalite phase of the powder particles occur at about 1100°C and have a minor effect on the dielectric constant. The Si dangling bonds also serve as electrical conducting centers in the powder and their annihilation due to the heat treatments is well observed as an increase in the electrical resistivity of the powder.

High Resolution Radial Distribution Function of Pure Amorphous Silicon

The structure factor $S(Q)$ of high purity amorphous Si membranes prepared by ion implantation was measured over an extended $Q$ range ( $0.03\char21{}55{\AA{}}^{\ensuremath{-}1}$). Calculation of the first neighbor shell coordination ( ${C}_{1}$) as a function of maximum $Q$ indicates that measurement of $S(Q)$ out to at least $40{\AA{}}^{\ensuremath{-}1}$ is required to reliably determine the radial distribution function (RDF). A $2%$ change in ${C}_{1}$ and subtle changes in the rest of the RDF were observed upon annealing, consistent with point defect removal. After annealing at 600 \ifmmode^\circ\else\textdegree\fi{}C, ${C}_{1}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.88$, which would explain why amorphous Si is less dense than crystalline Si.

On the Wohlfarth's Conjecture on the Magnetism of Pure Amorphous Iron

On the Wohlfarth's Conjecture on the Magnetism of Pure Amorphous Iron

Electrical and Magnetic Properties of Pure Amorphous Cobalt Films

Pure amorphous cobalt films (∼100 Å) have been prepared by condensation onto liquid helium cooled glass substrates at 10-10 Torr. The films underwent an abrupt and irreversible four fold drop in resistivity at about 55 K, characteristic of metallic films during the amorphous to crystalline transition. Analysis of the 6-line Mössbauer spectra indicates the hyperfine field is 1.5% lower and each line is 30% broader compared with the same quantity in the crystalline phase. No statistically significant changes were found for the other Mössbauer parameters. A microscopic interpretation is proposed.

Preparation and Catalytic Oxidation of Pure Amorphous Carbon

Preparation and Catalytic Oxidation of Pure Amorphous Carbon