Formation Of Impurities Research Articles

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

CO2 laser post-treatment of sol-gel-derived Y3Al5O12:Ce phosphor ceramic powders

Cerium-doped yttrium aluminum garnet (Y3Al5O12:Ce, YAG:Ce) was prepared using a sol-gel method and then fired for CO2 laser post-treatments. Phase transformations and formation of impurities were not observed in YAG:Ce after CO2 laser sintering. The shift of the diffraction peak and the appearance of another Raman peak indicate a more homogeneous distribution of Ce activators and enhanced crystallinity in laser-sintered YAG hosts. Larger spheres (100–200 μm) with tiny crystallites (<10 μm) were observed on the smoother surface in the laser-sintered YAG:Ce, unlike the irregular, porous, and layered powders in the sol-gel-derived YAG:Ce (1–100 μm). Photoluminescence (PL) measurements revealed an emission increase of 180% and a red shift of the emission peak for the laser-sintered YAG:Ce powders compared with the sol-gel-derived powders. Both have comparable thermal PL quenching behavior; however, the YAG:Ce powders with CO2 laser treatment exhibited a PL efficiency improvement of approximately 4%.

Innovative 2'-O-Imino-2-propanoate-Protecting Group for Effective Solid-Phase Synthesis and 2'-O-Deprotection of RNA Sequences.

The implementation of protecting groups for the 2'-hydroxyl function of ribonucleosides is still challenging, particularly when RNA sequences must be of the highest purity for therapeutic applications as nucleic acid-based drugs. A 2'-hydroxyl-protecting group should optimally (i) be easy to install; (ii) allow rapid and efficient incorporation of the 2'-O-protected ribonucleosides into RNA sequences to minimize, to the greatest extent possible, the formation of process-related impurities (e.g., shorter than full-length sequences) during solid-phase synthesis; and (iii) be completely cleaved from RNA sequences without the production of alkylating side products and/or formation of mutagenic nucleobase adducts. The reaction of 2'-O-aminoribonucleosides with ethyl pyruvate results in the formation of stable 2'-O-imino-2-methyl propanoic acid ethyl esters and, subsequently, of the fully protected ribonucleoside phosphoramidite monomers, which are required for the solid-phase synthesis of two chimeric RNA sequences (20-mers) containing the four canonical ribonucleosides. Upon treatment of the RNA sequences with a solution of sodium hydroxide, the 2'-O-imino-2-methyl propanoic acid ethyl ester-protecting groups are saponified to their sodium salts, which after ion exchange underwent quantitative intramolecular decarboxylation under neutral conditions at 65 °C to provide fully deprotected RNA sequences in marginally better yields than those obtained from commercial 2'-O-tert-butyldimethylsilyl ribonucleoside phosphoramidites under highly similar conditions.

Effect of the diffusion temperature on interaction of clusters with impurity atoms in silicon

In this paper, the results of studies of the effect of the diffusion temperature on interaction of clusters of manganese atoms with the sulfur ones have been presented. It has been shown that the electrical parameters of the samples simultaneously doped with sulfur and manganese completely coincide with the parameters of the initial material, i.e. as if they do not contain not only sulfur and manganese, but also thermodonors are not formed. The obtained results make it possible to exclude the possibility of gettering of impurity atoms or formation of some kind of solid solutions, if taking into account the impurity atoms of manganese and sulfur, which complicates their diffusion in the crystal bulk. It has been established that for the initial p-type silicon with the resistivity close to p ~ 10 Ω·cm, the diffusion temperature of 1100 °C is the most optimal one to form clusters with the maximum participation of the introduced sulfur and manganese atoms.

One-pot synthesis of 2-aminobenzoxazole derivatives using acetic acid as an electrolyte under electrochemical conditions

In this work, we have developed an electrochemical method to prepare 2-aminobenzoxazole by using acetic acid as an electrolyte. The key benefits of this method are being cleaner reaction pattern with minimum impurity formation, no metal catalyst used, high atom economy, robust, scalable and having a broad substrate scope. Previously, electrochemical conversions were reported with the addition of a supporting electrolyte such as tetrabutyl ammoniumbromide, sodium iodide and lithium perchlorate, but in this conversion we have removed the use of all supporting electrolytes and we have used acetic acid, which plays a dual role of opening the benzoxazole moiety and works as an electrolyte. All these electrochemical conversions were done on a electrochemical reactor prepared through a 5v mobile charger having a output current density of 0.35A.cm−2. Various pharmaceutically relevant secondary amines are coupled with benzoxazole in high yield by using this set-up. All the conversions were done at room temperature and total conversion observed in 6 h. The scale of the conversion ranges from milligram to gram. Active intermediate of Suvorexant, a medicine for insomnia, was prepared by using this method.

Intriguing role of novel ionic liquids in stochastic degradation of chitosan

Green technique for hydrolysis of chitosan was developed using novel Brønsted Acidic Ionic Liquids (BAILs) as homogenous reusable catalysts. Efficiency of BAILs in controlling stochastic and irregular breakdown of chitosan was compared with that of mineral acids. Structural elucidation of the novel BAILs was performed using H1-NMR evaluation and supplemented using mass spectroscopy. Additionally, thermal characterization was conducted using TGA-DTA analysis, while acidity was estimated by deriving the Hammet acidity function. BAILs investigated in this work enabled consistent production of LMWCS variants, with minimum formation of residual impurities. Around 80 % reduction in molecular weight was noted as compared to original under extreme conditions employed. Further, Box-Behnken Design (BBD) was implemented to optimize effect of processing parameters for conversion of chitosan to low molecular weight congeners.

Dimethyl Fumarate: Heterogeneous Catalysis for the Development of an Innovative Flow Synthesis

The present work describes the development of an improved synthesis of the active pharmaceutical ingredient (API) dimethyl fumarate. The use of continuous flow technology and the newly developed methylation conditions solve some of the issues of previous commercial production strategies, e.g., reaching complete conversion and avoiding the formation of toxic impurities. The optimization was carried out using the design of experiment approach and afforded a very efficient, sustainable process, suitable for the industrial application.

Elucidation of the Mechanism of Endo-XaaC-terminal Peptide Impurity Formation in SPPS through DoE Investigation, Their Control, and Suppression

Standard peptide acid syntheses on the CTC resin frequently experience the formation of impurities with redundant incorporation of the C-terminal residues, annotated as endo-XaaC-terminal in this p...

Mitigate self-compensation with high crystal symmetry: A first-principles study of formation and activation of impurities in GaN

Formation and activation energies of common impurities: silicon (Si), germanium (Ge), carbon (C), beryllium (Be), and magnesium (Mg) in wurtzite (wz-) and zincblende (zb-) GaN are investigated by first–principles calculations. Si and Ge are excellent donors with low activation energies (<30 meV). The acceptor activation energies of C and Be in wz-GaN (and zb-GaN) are found to be 590 and 205 meV (and 490 and 134 meV), respectively. Neither C nor Be is a qualified acceptor in general as the former has a large activation energy (>300 meV) and the latter has a strong self-compensation effect (the formation energy of Bei compensating donor is negative). Bei is energetically abundant in zb-GaN because it has a 0.66 eV lower formation energy than wz-GaN. This is attributed to the coherence of the symmetricity between the s-orbitals and the interstitial site. The acceptor activation energy of Mg in zb-GaN is found to be 153 meV, which is smaller than its value in wz-GaN, 226 meV. Vibrational analysis suggests that Mgi compensating donor is less favorable to form in zb- than wz-GaN, since the higher symmetricity of the interstitial site in zb-GaN renders a much smaller vibrational entropy. Contrarily, the differences are insignificant for the impurities residing on Ga sites due to the same tetrahedral symmetricity. The results evidence the importance of self-compensation effects, which can be mitigated by the higher crystal symmetry of zb-GaN.

Identification and structural characterization of potential degraded impurities of ribociclib by time of flight -tandem mass spectrometry, and their toxicity prediction

The US FDA and EMA approved Ribociclib (RIBO) to treat metastatic breast cancers in 2017. Formation of impurities during storage of any drug can significantly contribute to its overall toxicity and therapeutic efficacy, which ultimately leads to a safety concern. Over the period, it has been observed that impurities sometimes cause serious unwanted toxicity, which can even lead to withdrawal of a drug from market. Therefore, complete characterization of potential impurities is extremely important to identify molecular hot spots regarding structural changes. To the best of our knowledge, till date, the potential degraded impurities of RIBO are unknown. No study reported in literature on the structural characterization of the degradation impurities of RIBO. In this study, an ICH recommended comprehensive stress study under hydrolytic, oxidative, photolytic and thermolytic conditions was performed on RIBO. The degradation products were characterized by tandem mass spectrometry utilising time of flight mass analyzer majorly after electrospray ionisation. The atmospheric pressure chemical ionisation mode was employed in characterization of the N-oxide degradation products where Meisenheimer rearrangement occurred. A degradation product was synthesized in house and fully characterized with the help of NMR (1H NMR, 13C NMR, DEPT, 2D NMR and D2O exchange experiments). The source of formylation for the generation of degradation products was investigated employing different solvent systems. The degradation pathways were delineated by explaining the putative mechanism of degradation in various conditions. The in silico toxicity of the degradation impurities was evaluated with the help of ProTox-II toxicity prediction platform.

Growth Evolution of AZO thin Films Deposited by Magnetron Sputtering at Room Temperature

Thin AZO films were grown by RF magnetron sputtering for different deposition times in argon plasmas. Optical, structural, and morphological properties, together with elemental composition, were studied and correlated with the observed effects on the electrical properties and compared with two models of mobility scattering (ionized impurities and grain boundaries). The results suggest that the carrier density in the studied case is limited to below 15% owing to the low ionization efficiency caused by the formation of neutral impurities as homologous phases. While the spread in the mobility during the initial stages of film growth is strongly influenced by grain boundaries, in thicker films the limitation on ion efficiency becomes more significant.

Investigation dissolution behaviours and kinetics parameters of ulexite in boric acid solution

Nowadays, boron and its derivatives are widely used in industrial and technological areas. Boron minerals are the main sources for obtaining pure boron chemicals in the usage of different applications such as the defense industry, health, industry, kitchen equipments, etc. In this paper, for the first time, it has been reported the dissolution behaviors and kinetics parameters of ulexite in the boric acid solution. To solve ulexite by boric acid is important, because boric acid as a solvent prevents the formation of impurities, and therfeore our study is a first in the literature. In this context, the dissolution of the ulexite has been investigated under various experimental parameters such as temperatures, acid concentration, solid/liquid ratio, particle size, dissolution rate, and stirring speed. The experimental findings shown that the dissolution kinetics of ulexite increase with an increase in temperature and acid concentration and a decrease in particle size, but decrease with mixing speed in the acid. Moreover, the dissolution of ulexite in boric acid and activation energy were evaluated. As a result, it was found that the dissolution kinetics were compatible with the chemical control model and the activation energy was 22.024 kJ mol-1.

Challenges in the crystal growth of Li2FeSiO4

The high-pressure optical floating-zone method enables single crystal growth of the Pmnb high-temperature phase of Li2FeSiO4. The influence of growth conditions on crystal quality, phase homogeneity, and impurity formation in Li2FeSiO4 is studied. The use of different starting materials, i.e., either the P121/n1 or the Pmn21 polymorph, as well as optimization of various growth conditions is investigated. Several mm3-sized high-quality single crystals are obtained by the choice of the Pmn21 polymorph as the starting material. A general challenge of Li2FeSiO4 crystal growth is polymorph control during crystallization. While the temperature gradient at the solid-liquid interface seems to have significant impact on stabilizing the Pmnb high-temperature phase, growth velocity has no evident effect.

Effect of PVP Coating on LiMnBO3 Cathodes for Li-Ion Batteries.

LiMnBO3 is a potential cathode for Li-ion batteries, but it suffers from a low electrochemical activity. To improve the electrochemical performance of LiMnBO3, the effect of polyvinyl pyrrolidone (PVP) as carbon additive was studied. Monoclinic LiMnBO3/C and LiMnBO3-MnO/C materials were obtained by a solid-state method at 500 °C. The structure, morphology and electrochemical behavior of these materials are characterized and compared. The results show that carbon additives and ball-milling dispersants affect the formation of impurities in the final products, but MnO is beneficial for the performance of LiMnBO3. The sample of LiMnBO3-MnO/C delivered a high capacity of 162.1 mAh g−1 because the synergistic effect of the MnO/C composite and the suppression of the PVP coating on particle growth facilitates charge transfer and lithium–ion diffusion.

Synthesis and Characterization of 5-MeO-DMT Succinate for Clinical Use.

To support clinical use, a multigram-scale process has been developed to provide 5-MeO-DMT, a psychedelic natural product found in the parotid gland secretions of the toad, Incilius alvarius. Several synthetic routes were initially explored, and the selected process featured an optimized Fischer indole reaction to 5-MeO-DMT freebase in high-yield, from which the 1:1 succinate salt was produced to provide 136 g of crystalline active pharmaceutical ingredient (API) with 99.86% peak area by high-performance liquid chromatography (HPLC) and a net yield of 49%. The report provides in-process monitoring, validated analytical methods, impurity formation and removal, and solid-state characterization of the API essential for subsequent clinical development.

Graphene transfer from a copper surface to a silicon substrate

The article presents a comparison of two methods of transferring single-layer graphene onto silicon substrates using poly (methyl methacrylate) (PMMA) and thermo-adhesive tape. The continuity of the transferred coating and the quality of the graphene film after the transfer stage were investigated. An analysis of the contaminants formed during the transfer of the graphene surface is carried out. It is shown that when using PMMA for transfer, heating of the samples leads to their damage due to thermal expansion and the formation of indelible impurities on the surface.

Adverse urbogeomorphological processes in the formation of harmful impurities in the air

The environmental problems of cities arose simultaneously with the cities themselves. Urban settlements in themselves (without special systems) do not correspond to the closed ecological type. The city is a large consumer of various resources, but it has virtually no conditions for waste disposal, recovery of resources. The negative side of urban life is the low quality of the natural environment and its main components - water, air, vegetation, etc .; saturation of its physical, chemical and biological contaminants. In general, the urban way of life generates abiological tendencies and "diseases of civilization". There is a direct relationship between the size of the city and the frequency of the disease. In large industrial cities, the incidence of allergic diseases is 10-20%, and in rural areas only 2-4%. The increase in allergic diseases among children is especially noticeable. The state of the urbanized natural-technogenic geomorphosystem can be assessed using a system of expert assessments, which ultimately allows to identify geomorphosystems with different degrees of resistance to man-made loads. In order to consistently study the state of the urban geomorphosystem and assess the stability of the terrain to man-made loads, it is proposed to carry out research at the following stages: Retrospective step-by-step analysis of the evolution of natural relief and historical-geomorphological territory based on the study of the history of settlement and development of geomorphological objects in the city. Assessment of the current state of the urbanized natural and man-made geomorphosystem. Zoning of the city territory according to the degree of potential geomorphological danger. Development of environmental recommendations and general forecasting of UPTG development taking into account geoecological risk. The retrospective step-by-step analysis of the evolution of natural relief includes two main stages: the study of the formation of the natural subsystem of UPTG in the future city and the stage of formation of natural-technogenic geomorphosystem in connection with urbanization. Based on historical and geomorphological analysis, a general picture of the use of geomorphological objects in the historical stage, three main stages of urbanization, which corresponded to a certain level of man-made loads on the terrain, namely: development without significant landforms (suburban); significant transformation of the relief without significant negative consequences (medieval and new); intensive urbanization with the emergence of zones of geoecological risk (modern). Estimation of the current state of the urbanized natural-technogenic geomorpho-system of logical conditions of the territory from the point of view of their resistance to man-caused influences and determination of the volumes of man-caused loads on the relief. To assess the man-made impact on the topography of the city, an inventory and classification of all sources of man-made impacts was conducted, the nature and intensity of this impact on the topography was studied. The structure of the modern city and the basis of functional zoning of the territory is subject to the same research. Assessment of the degree of man-made impact is carried out on a set of indicators that take into account the level of static and dynamic loads, the degree of relief, the presence and nature of man-made deposits. Static loads were determined by indicators of building density, density of water supply and sewerage mains, capacity of man-made sediments (alluvium, embankments, landfills). The intensity of static loads is estimated according to their types - engineering, construction, operation.

Comparison between Washing and Ambient Storage of Ni-Rich Active Materials By TGA-MS and XPS

To achieve the energy density needed for automotive applications, Ni-rich cathode active materials (CAMs), like NCM851005 (Li1+ d(Ni0.85Co0.10Mn0.05)1- dO2), are promising candidates.[1] However, these materials are susceptible to the formation of surface impurities upon ambient air exposure during storage.[2–4] These surface groups were subject of various studies, but detailed information on their formation rate and on their decomposition temperatures are lacking. In this study, we investigated the changes in surface chemistry during ambient storage and during subsequent heating for the Ni-rich material NCM851005 in comparison to that of NCM111. We thus identify the surface groups after storage and also provide evidence for a Li+/H+-exchange, a phenomenon which had been observed during the washing of these materials with water.[5] In order to gain knowledge about the formation rate of surface impurities on NCM111 and NCM851005, the pristine powders were subjected to an accelerated storage test. The samples were stored at 25°C in ambient air with a constant relative humidity of ~85% (further on referred to as wet-storage) for increasing time intervals starting from 5 min up to 1 week. After each storage interval, a TGA-MS measurement (thermogravimetric analysis coupled with mass spectrometry) was performed under Ar (at 40 mL/min). The TGA-MS protocol contains a temperature hold phase at 25 °C, then a heat ramp (10 K/min) to 120 °C with a hold at this temperature for 30 minutes, followed by a second temperature ramp to 450 °C (10 K/min), and a final hold at this temperature (see red line in Fig. 1a). The plateau at 120 °C is designed to deconvolute the physisorbed from the chemisorbed water. A washed material (at a water to CAM mass ratio of 5:1) was also analyzed by the same TGA-MS procedure.In addition to the TGA measurements, a special XPS sample holder was used to heat the samples inside the main XPS chamber to evaluate the NCM surface at different temperatures, monitoring the decomposition and desorption of surface contaminants.It was found that the amount of surface contaminants indeed increased with storage time. Predictably, the extent of surface contaminants increased more rapidly for the Ni-rich NCM851005 material than compared to a Ni-poor NCM111 sample. Furthermore, oxygen release at already 280 °C was seen for NCM851005 kept under wet-storage for 7 days (Fig. 1c, blue line). Oxygen release for the as-received material is only observed at higher temperatures (T>650°C). This early onset of oxygen evolution is reminiscent of that of either partially delithiated NCMs or of washed NCMs (see also green line in Fig. 1c).[5,6] We will discuss the likely mechanism for this behavior, supporting our arguments with XPS measurements, where we have found a defective oxygen-deficient phase after heating the materials above the O2 release temperature when the materials was washed, but not in case of the as-received material. This is further evidence for a Li+/H+-exchange during storage of Ni-rich materials under ambient conditions.We will discuss future mitigation strategies such as surface coatings or gas treatment to minimize the effects of ambient storage.Figure 1: TGA-MS analysis of as-received (black lines), wet-stored (in blue) and washed (in green) NCM851005 under Ar. The upper panel shows the TGA profile and relative mass change of the different samples. The other panels show the MS traces of (b) H2O (m/z = 18), (c) O2 (m/z=32) and (d) of CO2 (m/z=44). Figure 1

Engineered Electrode-Electrolyte Interface for Moisture-Stable, Dendrite-Free Garnet-Type Solid-State Electrolytes

Lithium-ion batteries (LIBs) are becoming increasingly universal energy storage systems to power most portable electronic devices and electric vehicles due to their high energy densities and long cycle life1-3. However, with increasing applications of LIBs into grid storage, an increase in the efficiency of LIBs is essential to meet today’s requirements2, 4. Solid-state batteries using garnet-type solid-state electrolytes (SSEs) are promising contenders for safe, high energy density devices due to their high lithium-ion conductivity at room temperature, wide electrochemical stability window, and the use of lithium metal anode5. However, garnet-type SSEs exhibit formidable challenges including the formation of lithium dendrites, instability in moisture containing atmosphere, and their high interfacial resistance. Although several strategies have been employed to improve the issues related to garnet-type SSE, most approaches focus on one challenge and fail to solve all other challenges. Herein, we demonstrate an engineered electrode-electrolyte interface with surface modification of Li6.5La3Zr1.5Ta0.5O12 (LLZT) garnet-type SSEs by two-dimensional hexagonal boron nitride (h-BN) nanosheets to solve the interfacial issues. Detailed spectroscopic evidence reveals that the surface modification effectively protects the LLZT from moisture-induced chemical degradation and suppresses the formation of adverse surface impurities for over 5 days in an open atmosphere. The interfacial resistance value has reduced nearly 10-fold when compared to the uncoated LLZT and exhibits stable lithium plating/stripping behavior for over 1400 hours at 0.2 mA cm-2. Advanced in-situ Raman analysis elucidates that h-BN layers remain stable during cycling and prevents the structural transformation of the garnet-type SSE at the interface.

Investigation into the Formation of Impurities during the Optimization of Brigatinib.

During the process development of brigatinib, we have made an unusual observation about some impurities. Detailed investigation has led to the conclusion that impurity A is formed via the raw material 2 oxidation, impurity B is formed via the pyrolysis of DMF, impurity C is formed via raw material 4, and impurity D is formed via HCl-catalyzed decomposition of intermediate 3. The present work details a report of the journey toward the development of an efficient process for the commercial production of brigatinib substantially free from all the impurities.