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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Hydrothermal synthesis of chiral carbon dots

Abstract Nanocolloids that are cumulatively referred to as nanocarbons, attracted significant attention during the last decade because of facile synthesis methods, water solubility, tunable photoluminescence, easy surface modification, and high biocompatibility. Among the latest development in this reserach area are chiral nanocarbons exemplified by chiral carbon dots (CDots). They are expected to have applications in sensing, catalysis, imaging, and nanomedicine. However, the current methods of CDots synthesis show often contradictory chemical/optical properties and structural information that required a systematic study with careful structural evaluation. Here, we investigate and optimize chiroptical activity and photoluminescence of L‐ and D‐ CDots obtained by hydrothermal carbonization of L‐ and D‐ cysteine, respectively. Nuclear magnetic resonance spectroscopy demonstrates that they are formed via gradual dehydrogenation and condensation reactions of the starting amino acid leading to particles with a wide spectrum of functional groups including aromatic cycles. We found that the chiroptical activity of CDots has an inverse correlation with the synthesis duration and temperature, whereas the photoluminescence intensity has a direct one, which is associated with degree of carbonization. Also, our studies show that the hydrothermal synthesis of cysteine in the presence of boric acid leads to the formation of CDots rather than boron nitride nanoparticles as was previously proposed in several reports. These results can be used to design chiral carbon‐based nanoparticles with optimal chemical, chiroptical, and photoluminescent properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Autonomous Synthesis of Thin Film Materials with Pulsed Laser Deposition Enabled by In Situ Spectroscopy and Automation

Autonomous systems that combine synthesis, characterization, and artificial intelligence can greatly accelerate the discovery and optimization of materials, however platforms for growth of macroscale thin films by physical vapor deposition techniques have lagged far behind others. Here this study demonstrates autonomous synthesis by pulsed laser deposition (PLD), a highly versatile synthesis technique, in the growth of ultrathin WSe 2 films. Further, by combing the automation of PLD synthesis and in situ diagnostic feedback with a high-throughput methodology, this study demonstrates a workflow and platform which uses Gaussian process regression and Bayesian optimization to autonomously identify growth regimes for WSe 2 films based on Raman spectral criteria by efficiently sampling 0.25% of the chosen 4D parameter space. With throughputs at least 10x faster than traditional PLD workflows, this platform and workflow enables the accelerated discovery and autonomous optimization of the vast number of materials that can be synthesized by PLD.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Synthesis of Melanin Mediated Silver Nanoparticles from Aeromonas sp. SNS Using Response Surface Methodology: Characterization with the Biomedical Applications and Photocatalytic Degradation of Brilliant Green

Melanin is ubiquitous in nature and has wide applications in cosmetics, agriculture, and medicine. The synthesized melanin from bacterium Aeromonas sp. SNS was further used as capping and reducing agents for synthesis of silver nanoparticles (AgNPs). The influence of the experimental parameters (AgNO{sub 3}, melanin concentrations, and temperature) and their interactions on the nanoparticle synthesis was optimized using response surface methodology (RSM). The Central Composite Design (CCD) with three independent variables was optimized for the effective synthesis of AgNPs. The optimized synthesis of AgNPs was achieved at the shortest time of 14.12 h in the presence of 2.62 mM AgNO{sub 3}, and 32.30 µg ml{sup −1} melanin concentration at 54.86 °C temperature. The synthesized AgNPs were characterized by means of UV–visible spectroscopy, FTIR, SEM, TEM, and PSD respectively. The AgNPs exhibited excellent antimicrobial activity against human and food-related pathogens. These AgNPs also have strong antioxidant potential which was estimated by DPPH, DMPD and FRAP radical scavenging assays. The 92.62% photocatalytic degradation of 250 PPM brilliant green was observed in 120 min. The present finding accelerates the melanin associated AgNPs could be used in the cosmetic and pharmaceutical industries as well as in textile industries as they have superior antimicrobial, antioxidant, and photocatalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Synthesis Temperature on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Combustion Method

ZnO nanoparticles at different temperatures were synthesized by using the combustion method. The effect of synthesis temperature on the properties of the nanoparticles was studied by using XRD, FESEM, EDS, TEM, photoluminescence (PL), Raman, diffuse reflectance spectra (DRS), and VSM characterization techniques. The XRD results reveal that the grown nanoparticles have a hexagonal wurtzite structure without any impurities and agreed with EDS results. FESEM and TEM micrographs show that the ZnO nanoparticles possess a spherical shape with agglomeration free, and the size increases with increase of synthesis temperature. From DRS studies, it was noticed that the band gap decreases with increase of synthesis temperature. In PL studies, blue peak at 465 nm may be due to defect-related transitions. A sharp intense peak in Raman spectra at 485 cm{sup −1} represents E{sub 2}H mode is a characteristic of a hexagonal wurtzite structure. The magnetic studies show that the magnetization decreases from 0.0172 to 0.0042 emu/g as the synthesis temperature increases from 400 to 550 °C. ZnO synthesized at 500 °C has a large squareness ratio. These materials are potential candidates for memory devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Metformin inhibition of mTORC1 activation, DNA synthesis and proliferation in pancreatic cancer cells: Dependence on glucose concentration and role of AMPK

Highlights: Black-Right-Pointing-Pointer Metformin inhibits cancer cell growth but the mechanism(s) are not understood. Black-Right-Pointing-Pointer We show that the potency of metformin is sharply dependent on glucose in the medium. Black-Right-Pointing-Pointer AMPK activation was enhanced in cancer cells incubated in physiological glucose. Black-Right-Pointing-Pointer Reciprocally, metformin potently inhibited mTORC1, DNA synthesis and proliferation. Black-Right-Pointing-Pointer Metformin, at low concentrations, inhibited DNA synthesis through AMPK. -- Abstract: Metformin, a widely used anti-diabetic drug, is emerging as a potential anticancer agent but the mechanisms involved remain incompletely understood. Here, we demonstrate that the potency of metformin induced AMPK activation, as shown by the phosphorylation of its substrates acetyl-CoA carboxylase (ACC) at Ser{sup 79} and Raptor at Ser{sup 792}, was dramatically enhanced in human pancreatic ductal adenocarcinoma (PDAC) cells PANC-1 and MiaPaCa-2 cultured in medium containing physiological concentrations of glucose (5 mM), as compared with parallel cultures in medium with glucose at 25 mM. In physiological glucose, metformin inhibited mTORC1 activation, DNA synthesis and proliferation of PDAC cells stimulated by crosstalk between G protein-coupled receptors and insulin/IGF signaling systems, at concentrations (0.05-0.1 mM) that were 10-100-fold lower than those used in most previous reports. Using siRNA-mediated knockdown of the {alpha}{sub 1} and {alpha}{sub 2} catalytic subunits of AMPK, we demonstrated that metformin, at low concentrations, inhibited DNA synthesis through an AMPK-dependent mechanism. Our results emphasize the importance of using medium containing physiological concentrations of glucose to elucidate the anticancer mechanism of action of metformin in pancreatic cancer cells and other cancer cell types.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist inhibits collagen synthesis in human hypertrophic scar fibroblasts by targeting Smad3 via miR-145

The transcription factor peroxisome proliferator-activated receptor-γ (PPAR-γ) functions to regulate cell differentiation and lipid metabolism. Recently, its agonist has been documented to regulate extracellular matrix production in human dermal fibroblasts. This study explored the underlying molecular mechanisms and gene interactions in hypertrophic scar fibroblasts (HSFBs) in vitro. HSFBs were cultured and treated with or without PPAR-γ agonist or antagonist for gene expression. Bioinformatical analysis predicted that miR-145 could target Smad3 expression. Luciferase assay was used to confirm such an interaction. The data showed that PPAR-γ agonist troglitazone suppressed expression of Smad3 and Col1 in HSFBs. PPAR-γ agonist induced miR-145 at the gene transcriptional level, which in turn inhibited Smad3 expression and Col1 level in HSFBs. Furthermore, ELISA data showed that Col1 level in HSFBs was controlled by a feedback regulation mechanism involved in PPAR-γ agonist and antagonist-regulated expression of miR-145 and Smad3 in HSFBs. These findings indicate that PPAR-γ-miR-145-Smad3 axis plays a role in regulation of collagen synthesis in HSFBs. - Highlights: • PPAR-γ agonist inhibits collagen synthesis in HSFBs. • Smad3 and type I collagen expression are decreased by PPAR-γ agonist. • miR-145 expression is increased by PPAR-γ agonist in HSFBs. • Increased miR-145 inhibits collagen synthesis by targeting Smad3. • miR-145 regulates collagen synthesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Role of protein kinase A and class II phosphatidylinositol 3-kinase C2β in the downregulation of KCa3.1 channel synthesis and membrane surface expression by lyso-globotriaosylceramide

The intermediate conductance calcium-activated potassium channel (KCa3.1) mediates proliferation of many cell types including fibroblasts, and is a molecular target for intervention in various cell proliferative diseases. Our previous study showed that reduction of KCa3.1 channel expression by lyso-globotriaosylceramide (lyso-Gb3) inhibits differentiation into myofibroblasts and collagen synthesis, which might lead to development of ascending thoracic aortic aneurysm secondary to Fabry disease. However, how lyso-Gb3 downregulates KCa3.1 channel expression is unknown. Therefore, we aimed to investigate the underlying mechanisms of lyso-Gb3-mediated KCa3.1 channel downregulation, focusing on the cAMP signaling pathway. We found that lyso-Gb3 increased the intracellular cAMP concentration by upregulation of adenylyl cyclase 6 and inhibited ERK 1/2 phosphorylation through the protein kinase A (PKA) pathway, leading to the inhibition of KCa3.1 channel synthesis, not the exchange protein directly activated by cAMP (Epac) pathway. Moreover, lyso-Gb3 suppressed expression of class II phosphatidylinositol 3-kinase C2β (PI3KC2β) by PKA activation, which reduces the production of phosphatidylinositol 3-phosphate [PI(3)P], and the reduced membrane surface expression of KCa3.1 channel was recovered by increasing the intracellular levels of PI(3)P. Consequently, our findings that lyso-Gb3 inhibited both KCa3.1 channel synthesis and surface expression by increasing intracellular cAMP, and controlled surface expression through changes in PI3KC2β-mediated PI(3)P production, suggest that modulation of PKA and PI3KC2β activity to control of KCa3.1 channel expression can be an alternative important target to attenuate ascending thoracic aortic aneurysms in Fabry disease. - Highlights: • Lyso-Gb3 causes elevation of intracellular cAMP. • Lyso-Gb3 inhibits the ERK 1/2 phosphorylation through PKA, thereby reducing KCa3.1 channel synthesis. • Lyso-Gb3 reduces PI3KC2β-mediated intracellular PI(3)P production. • Lyso-Gb3 reduces both surface and total expression of the KCa3.1 channel. • Increasing intracellular levels of PI(3)P only recovers the reduced surface expression.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Green synthesis and characterization of silver nanoparticles using Enicostemma axillare (Lam.) leaf extract

Highlights: • Green synthesis of AgNPs is using Enicostemma axillare. • Characterization of AgNPs was done by TEM, SEM and XRD. • The synthesized AgNP solution was stable for more than two months. • The method was eco-friendly, benign and cost-effective. In the present article, the facile green synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Enicostemma axillare (Lam.) has reported. This is a simple, cost-effective, stable for a long time and reproducible aqueous synthesis method to obtain a self-assembly Ag nanoparticles. The size and shape of Ag nanoparticles were characterized by XRD, TEM, and SEM-EDS. The formation and stability of the reduced silver nanoparticles in the colloidal solution were monitored by UV–Vis spectrophotometer analysis. Zeta potential was confirmed by DLS study. The mean particle diameter of silver nanoparticles was calculated from the TEM, SEM and the size of the particles was measured between 15 and 20 nm. TEM analysis revealed the spherical shape of the particles. Crystalline nature of the nanoparticles in the face-centred cubic structure are confirmed by the peaks in the XRD pattern corresponding to (111), (200), (220) and (311) planes. This study showed the biogenic, environmentally friendly and cost-effective synthesis and characterization of the silver nanoparticles.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Combination of two β-galactosidases during the synthesis of galactooligosaccharides may enhance yield and structural diversity

Highlights: • Combination of two β-galactosidases can increase total GOS yield. • Effect on GOS yield is strongly dependent on the used enzyme sources. • Consecutive or simultaneous enzyme addition leads to different results. • Combination of two β-galactosidases can increase the percentage of GOS ≥ DP3. • Combination of two β-galactosidases can increase the structural diversity of GOS. In this study, the combination of two β-galactosidases to synthesize prebiotic galactooligosaccharides (GOS) was evaluated in terms of total GOS yield as well as GOS structures (chain length). Two different combinations of either Aspergillus oryzae and Cryptococcus laurentii or Aspergillus oryzae and Kluyveromyces lactis were tested to examine the influence of enzyme origin. Neither consecutive nor simultaneous synthesis with A. oryzae and C. laurentii led to an increased GOS yield. However, with the latter, synthesis of higher GOS (≥3 monomer units) was enhanced from 38.5% to 40% with special emphasis of tetra- and pentasaccharides, which increased from 6.7% to 12.8% and from 0.4% to 3.3%, respectively. Additionally, due to the different preferences of the two β-galactosidases in terms of types of glycosidic linkages, the structural diversity of the final GOS product could be increased. Using K. lactis following the synthesis with A. oryzae increased the yield of total GOS from 24.6% to 33.1%, which was mainly due to the formation of GOS disaccharides. On the other hand, applying A. oryzae as the second enzyme led to a degradation of di- and trisaccharides, and thus total GOS yield was diminished, although the yield of tetrasaccharides could be enhanced. In conclusion, with both studied enzyme combinations it was possible to increase the percentage of higher GOS and reduce the residual lactose content of the final mixture, which is beneficial for subsequent purification processes. Thus, using more than one β-galactosidase during the synthesis of GOS represents an interesting research area, which should be explored in more detail in the future.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Sustainable ammonia synthesis from nitrogen wet with sea water by single-step plasma catalysis

Ammonia synthesis at ambient conditions employing intermittent distributed green sources of energy and feedstocks is globally sought to replace the centralized Haber-Bosch (H-B) process operating at high temperature and pressure. We report herein for the first time an effective and sustainable ammonia synthesis pathway from N 2 wet with seawater vapor over spherical SiO 2 and M/SiO 2 (M: Ag, Cu, and Co) catalysts driven by non-thermal plasma (NTP). Experimental results indicate that the presence of a catalyst is required for ammonia production from seawater vapor and N 2 . The Co/SiO 2 catalyst delivered the highest ammonia synthesis rate (r NH 3 ) of 3.7 mmol g cat -1 h -1 and energy yield of 3.2 g NH 3 ∙kW -1 ∙h -1 at a relatively low input power of 2 W. The extraction of H atoms from H 2 O molecules plays an important role in the ammonia synthesis from seawater vapor. Finally, this work unfolds a novel platform for the subsequent optimization of sustainable ammonia production from endless resources such as seawater and N 2 through catalytic non-thermal plasma potentially powered by renewable sources.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Microwave-Mediated ammonia synthesis over Co 2 Mo 3 N catalysts at low pressures

The Haber-Bosch process for ammonia (NH 3 ) synthesis is a major contributor to greenhouse gas emissions and is responsible for > 2 % of the world’s energy consumption each year encouraging the need for alternative renewable-based options. Here, this study investigates an earth-abundant ternary metal nitride (i.e., Co 2 Mo 3 N) catalyst to develop a renewable-based NH 3 synthesis approach, utilizing an energy-efficient microwave-assisted route. Using a combination of spectroscopic and catalytic measurements coupled with surface analysis techniques, Co 2 Mo 3 N was evaluated as a stable and efficient NH 3 synthesis catalyst. Results presented here demonstrate NH 3 synthesis on Co 2 Mo 3 N at ~420 °C and ambient pressure yield ~0.7 mmolNH3.g cat -1 .h -1 and up to ~12 mmol NH3 .g cat -1 .h -1 at 28 bar under microwave irradiation. Co 2 Mo 3 N displayed an activation energy of ~72 kJ.mol -1 and yielded NH 3 following first-order kinetics with respect to both H 2 and N 2 . These studies illustrate the potential of using this catalyst for a sustainable, cost-effective, and environmentally friendly approach to producing NH 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Isotope effects at the origin of life: Fingerprints of the Strecker synthesis

We report strecker synthesis creates α-amino acids from prebiotically plausible substrates (cyanide, ammonia, and aldehydes) and is widely hypothesized to be a key mechanism in the chemistry that led to life on Earth and on other planets. To better constrain the synthetic environments and precursors of abiotic α-amino acids, and to determine unique signatures of abiogenic amino acids, we measured the molecular-averaged and site-specific carbon and nitrogen isotope effects for the Strecker synthesis of alanine. The reaction steps of the Strecker synthesis can be divided into two groups: an initial series of reversible amination and nitrile-addition reactions (‘equilibration’) and a second series of irreversible hydrolysis reactions (‘hydrolysis’). The equilibration of cyanide, acetaldehyde, and ammonia with the intermediate, α-aminopropionitrile (α-APN), has a measured 55.1‰ equilibrium nitrogen isotope effect between the 15 N-rich amine nitrogen in α-aminopropionitrile and the 15 N-poor ammonia and a 20.0‰ equilibrium carbon isotope effect between the 13 C-poor C-2 site in α-aminopropionitrile and the 13 C-rich carbonyl carbon in acetaldehyde. The first irreversible hydrolysis step is inferred to have an up to 10‰ normal carbon fractionation (i.e., faster for 12 C, slower for 13 C) for the whole molecule, but it also has one or more side reactions that deplete the reactive α-APN reservoir by up to 15‰. The second hydrolysis step has a 15.4‰ normal kinetic isotope effect on the amide (C-1) site of alaninamide, which becomes the carboxyl site of alanine. Other α-amino acids will likely experience similar nitrogen isotope fractionations between ammonia and their amine sites, and similar carbon isotope fractionations between the carbonyl carbon in reactant aldehydes or ketones and the intermediate α-aminonitrile, and between cyanide and the carboxyl site. Therefore, these isotope effects allow us to predict the carbon and nitrogen isotopic contents and intramolecular structures of α-amino acids formed by Strecker synthesis based on their substrates’ isotopic compositions, or to infer the isotopic compositions of substrates from which amino acids formed, for example in the case of the amino-acid-rich carbonaceous chondrites. The site-specific C and N isotopic compositions of amino acids formed by Strecker chemistry contrast with those typical of terrestrial biosynthetic amino acids, so these data also provide a means of discriminating between biogenic and abiogenic α-amino acids.

58 GEOSCIENCES↗
DOE OSTI2014

Fe{sub 3}O{sub 4}–CNTs nanocomposites: Inorganic dispersant assisted hydrothermal synthesis and application in lithium ion batteries

Fe{sub 3}O{sub 4}–CNTs nanocomposites with a particle size of ∼80 nm have been synthesized through an organic-free hydrothermal synthesis strategy by using Sn(OH){sub 6}{sup 2−} as an inorganic dispersant, and served as anode materials of lithium ion batteries. Nano-sized and micro-sized Fe{sub 3}O{sub 4} without CNTs have also been prepared for comparison. The cycle performances of the as-obtained Fe{sub 3}O{sub 4} are highly size-dependent. The Fe{sub 3}O{sub 4}–CNTs nanocomposites can deliver reversible discharge capacity of ∼700 mA h/g at a current density of 50 mA/g after 50 cycles. The discharge capacity of the micro-sized Fe{sub 3}O{sub 4} decreased to 171 mA h/g after 50 cycles. Our work not only provides new insights into the inorganic dispersant assisted hydrothermal synthesis of metal oxides nanocrystals but also gives guidance for finding new nanocomposites as anode materials of lithium ion batteries. - Graphical abstract: Fe{sub 3}O{sub 4}–CNTs nanocomposites have been prepared through an inorganic dispersant assisted hydrothermal synthesis strategy, and served as anode materials of lithium ion batteries with enhanced performance. - Highlights: • Sn(OH){sub 6}{sup 2−} is a good inorganic dispersant for the hydrothermal synthesis of nano Fe{sub 3}O{sub 4}. • The cycle performances of nano Fe{sub 3}O{sub 4} anode are much better than that of micro Fe{sub 3}O{sub 4} anode. • Compositing CNTs can enhance the cycle performances of nano Fe{sub 3}O{sub 4} anode.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Highly dispersive α″-Fe{sub 16}N{sub 2} particle synthesis using hydroxyapatite coating

Alpha″-Fe{sub 16}N{sub 2} nanoparticles (NPs) with high magnetic crystalline anisotropy are useful for practical applications such as recording media. However, due to their strongly aggregated and/or sintered form, which occurs during synthesis, the utilization of the NPs has been limited thus far. Here, we report a method for synthesizing highly dispersive α″-Fe{sub 16}N{sub 2} NPs using hydroxyapatite (HAp). The chemically and thermally stable structure of the HAp coating results in the isolation of individual NPs, such that sintering is prevented during synthesis. Additionally, the acicular shape of the HAp crystal did not hinder gas diffusion during the gas reaction. Finally, HAp can be removed by a chelating agent without deteriorating the magnetic properties, resulting in highly dispersive α″-Fe{sub 16}N{sub 2} NPs. - Graphical abstract: Synthesis process of highly dispersive α″-Fe{sub 16}N{sub 2} particles using hydroxyapatite coating and SEM images of nanoparticles. - Highlights: • Highly dispersed α″-Fe{sub 16}N{sub 2} NPs were synthesized using hydroxyapatite (HAp). • HAp coating was stable chemically and thermally during gas reaction of α″-Fe{sub 16}N{sub 2} synthesis. • The magnetic property of the resultant Fe{sub 16}N{sub 2} NPs are M{sub s} of 170 emu/g and H{sub C} of 2450 Oe.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Low temperature synthesis and characterization of Na–M–(O)–F phases with M=Ti, V

Na{sub 5}Ti{sub 3}O{sub 3}F{sub 11} was prepared by the microwave assisted method, and presents a chiolite related structure with cell parameters a=10.5016(5), b=10.4025(5), and c=10.2911(5) Å and Cmca (no. 64) space group. From solvothermal synthesis at 100 °C the cryolite Na{sub 3−δ}VO{sub 1−δ}F{sub 5+δ} was prepared, which crystallizes in the monoclinic system with a=5.5403(2), b=5.6804(2), c=7.9523(2) Å, β=90.032(7)° cell parameters and P2{sub 1}/n (no. 14) space group. Under similar synthesis conditions but with higher HF concentration the chiolite-type phase Na{sub 5−δ}V{sub 3}F{sub 14} was achieved, which exhibits a=10.5482(2), b=10.4887(1) and c=10.3243(1) Å cell parameters and Cmc2{sub 1} (no. 36) space group. A single crystal also having the chiolite structure was synthesized at 200 °C which exhibits tetragonal symmetry (a=7.380(3) and c=10.381(11) Å and space group P4{sub 2}2{sub 1}2 (no. 94)). Bond valence sum indicates that it contains V{sup 4+} and therefore can be formulated as Na{sub 5}V{sub 3}O{sub 3}F{sub 11}. - Graphical abstract: Na{sub 5}M{sub 3}(O,F){sub 14} with M=Ti and V having chiolite structure and Na{sub 3−δ}VO{sub 1−δ}F{sub 5+δ} cryolite were prepared by means of microwave-assisted and solvothermal synthesis. - Highlights: • Na{sub 5}Ti{sub 3}O{sub 3}F{sub 11} chiolite was prepared by a microwave assisted method and characterized. • Na{sub 3−δ}VO{sub 1−δ}F{sub 5+δ} and Na{sub 5−δ}V{sub 3}F{sub 14} were prepared by solvothermal synthesis. • The compounds were structurally characterized by diffraction techniques. • O/F distribution was estimated by applying Pauling’s second rule.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Synthesis of Zn–Fe layered double hydroxides via an oxidation process and structural analysis of products

The synthesis of Zn–Fe(III) layered double hydroxides was attempted, employing different pathways using either Fe(II) or Fe(III) species together with Zn as the initial reagents. The product derived from the synthesis employing Fe(II) was found to transition to a Zn–Fe(III) layered double hydroxides phase following oxidation process. In contrast, the product obtained with Fe(III) did not contain a layered double hydroxides phase, but rather consisted of simonkolleite and hydrous ferric oxide. It was determined that the valency of the Fe reagent used in the initial synthesis affected the generation of the layered double hydroxides phase. Fe(II) species have ionic radii and electronegativities similar to those of Zn, and therefore are more likely to form trioctahedral hydroxide layers with Zn species. - Graphical abstract: The synthesis of Zn–Fe(III) layered double hydroxides was attempted, employing different pathways using either Fe(II) or Fe(III) species together with Zn as the initial reagents. - Highlights: • Iron valency affected the generation of Zn–Fe layered double hydroxides. • Zn–Fe layered double hydroxides were successfully synthesized using Fe(II). • Fe(II) species were likely to form trioctahedral hydroxide layers with Zn species.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Peculiarities of formation of phase composition, porous structure, and catalytic properties of tungsten oxide-based macroporous materials fabricated by sol–gel synthesis

The method of template sol–gel synthesis of tungsten oxide-based macroporous materials using ‘core–shell’ latex particles as colloid templates is described. The chemical composition and structural characteristics of the synthesized macroporous oxide systems have been investigated. The peculiarities of formation of material phase composition and macroporous structure under different template thermal destruction conditions have been revealed. An optimal method of a targeted synthesis of the crystalline tungsten(VI) oxide having a defect-free macroporous structure (average pore size 160 nm) and efficient catalytic properties under organic liquid phase oxidation conditions has been suggested. The prospects of the fabricated material application as catalysts of hydrothermal oxidation of radionuclide organic complexes at radioactive waste decontamination have been demonstrated. - Highlights: • Macroporous tungsten oxides were fabricated via sol–gel process. • The correlation between synthesis conditions and composition was determined. • Influence of synthesis conditions on porous structure has been explained. • The effects of template thermodestruction have been set up. • High potential of such materials for catalysis applications has been shown.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Controlling the sol–gel process of nano-crystalline lithium-mica glass-ceramic by its chemical composition and synthesis parameters

This paper aims to explore the impact of the parameters such as pH of the system, refluxing temperature, water quantity and chemical composition on the sol–gel synthesis of lithium-mica glass-ceramic nano-powder. The synthesis process was accomplished using two chemical composition formula (Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} and LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2}). X-ray diffraction, Brunauer–Emmett–Teller surface area measurement and scanning electron microscopy techniques were applied to evaluate a variety of as-synthesized samples. Consequently, a transparent homogeneous sol was obtained under the conditions as pH ≤ 4, synthesis temperature ≤ 50 °C, and mol ratio of water to chemicals ≤ 2. The prepared nano-powders under such conditions were in the range of 60–100 nm. The results also revealed that the mica glass-ceramics prepared based on the composition Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} possessed finer powders due to their slow hydrolysis process. Moreover, any reduction in the stoichiometric deviation of lithium mica (x) leads to acquiring finer powders. - Highlights: • A transparent homogeneous sol leads to prepare nanopowders in the range of 60–100 nm. • The particles synthesized at lower temperatures possess finer sizes. • The acquired product which is prepared with excessive water offers larger sizes. • Any reduction in stoichiometric deviation leads to acquiring finer powders. • Taking synthesis composition as Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} offers finer powders.

36 MATERIALS SCIENCE↗