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Iodine pentoxide (I2O5) based nanothermites are one of the most promising candidates for biocidal energetic materials due to superior reactivity and high iodine content. However, the tunability of nanothermites, which is important for biocidal performance, has not been fully exploited for I2O5 based nanothermites. In this work, I2O5 with various fuels (Al, Ti, Si) and their mixtures (i.e., a ternary system) have been investigated. The reactivity and flame temperature were evaluated by a pressure cell coupled with a spectrometer. Temperature-Jump time-of-flight mass spectrometry (T-Jump TOFMS) was used to probe the reaction mechanism and iodine release behavior, along with a high-speed camera to capture the ignition event. I2O5 showed distinct reactivity with different fuels. As a result, by varying the fuel composition of ternary systems, the combustion properties can be tuned. Rapid heating experiments revealed that the reaction initiation was shifted from gas phase dominated to condensed phase dominated mechanism after introducing Ti or Si into Al/I2O5 system. Further analysis of the ternary systems found that the energy release rate correlates with burn time instead of flame temperature. This study shows an approach to tune the reactivity and energy release rate of I2O5 based nanothermites without compromising the energy density.

The quantitative determination of the carbon hybridization is critical for establishing processing-structure-properties relationships for carbon-based materials, including amorphous carbon coatings. While several techniques have been employed to characterize the amount of sp2 and sp3 carbon in these materials, direct comparisons between analytical results are limited. Here, we compare near edge X-ray absorption fine structure (NEXAFS) spectra of a silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) coating acquired in synchrotron-based scanning transmission X-ray microscopy (STXM) mode with electron energy loss spectra (EELS) obtained from the same a-C:H:Si:O lamella. While the fractions of sp2 carbon computed from STXM and EELS spectra are in close agreement, the comparison of NEXAFS spectra acquired in STXM mode with NEXAFS spectra collected in partial electron yield mode on a flat a-C:H:Si:O surface indicated that the destructive preparation of thin lamellae for STXM analyses induces variations in the structure of a-C:H:Si:O, namely the breakage of carbon-silicon and carbon-hydrogen bonds, a change in ordering of sp2-bonded carbon, and an increase in the sp2 carbon fraction. These findings can help scientists in the careful interpretation of spectroscopic results obtained from the analysis of samples made of metastable materials after the destructive preparation of specimens for analytical purposes.

Freezing techniques are an essential part of biologics manufacturing processes, yet the formation of ice/water interfaces can impart detrimental effects on proteins. However, the absence of chemical and structural differences between ice and liquid water poses the question as to why ice can destabilize proteins. We hypothesize that the destabilizing stress of the ice-liquid water interface does not originate from the ice-water system itself but rather from the air microbubbles present during the freezing process. As the temperature decreases, the dissolved air is expelled from the ice crystal lattices in the form of microbubbles and is subsequently trapped by the advancing ice front. This newly formed air-water interface represents an additional interfacial area for the proteins to be adsorbed onto and denatured. The result showed that freezing at ∼ 1 K/s led to the formation of small circular microbubbles with diameters ranging from 100 µm to 500 µm. In contrast, slower freezing resulted in the formation of larger, elongated millimeter-size bubbles. The reduction of the number of microbubbles was carried out by the deaeration process using agitation under reduced pressure at 20 kPa. The resulting deaerated (i.e., low dissolved air) protein samples were frozen and monitored for the formation of subvisible aggregates using micro-flow imaging (MFI). The results demonstrated that deaerating the samples prior to intermediate freezing (i.e., TFF) reduced the number of aggregates for both highly surface-active and low surface-active proteins (lactoferrin and bovine IgG, respectively). This reduction was more pronounced in spray freeze drying (SFD) than thin-film freezing (TFF), and less apparent in conventional lyophilization.

In this work, we investigate the production of copper-zinc-tin-sulfide (CZTS) thin films via the sintering of nanoparticle coatings. CZTS nanoparticles are produced via spray pyrolysis starting from a solution of metal salts and thiourea. This approach yields small particles that are easy to disperse and apply onto the desired substrate. Sintering these coatings into large-grained films, however, is not trivial. We have used a sodium disulfide-dipping technique that facilitates large-scale grain growth and high-phase purity after annealing in a sulfur atmosphere. We have also utilized a custom-built apparatus to perform in situ Raman spectroscopy on closed systems in volatile and corrosive environments at high temperatures. With this apparatus, we have observed the growth of long-range-ordered crystal domains at high temperature. We have found that precise control of the cooling rate is highly beneficial for cation ordering in large grain CZTS, and that cation re-ordering and phase re-homogenization in large grain CZTS are possible via low-temperature post-processing. This study highlights the fact that much is still not understood about the kinetics of phase evolution for this complex quaternary system during thermal processing, and that well-designed in-situ characterization techniques are necessary to overcome this fundamental lack of knowledge.

In this work, we utilize a low-temperature non-equilibrium plasma to nucleate and grow sub-10 nm Si particles with varying degrees of crystallinity by tuning the level of power coupled into plasma discharge. Temperature-programmed desorption spectroscopy shows that as-prepared amorphous Si nanoparticles (a-nSi) incorporate more hydrogen than crystalline Si nanoparticles (c-nSi). Further, hydrogen is incorporated in the material in the form of higher silicon hydrides with a lower desorption temperature. Combustion cell measurements show that when formulated with KClO4, a-nSi outperforms its crystalline counterpart with respect to pressure output. The pressurization rate of a-nSi/KClO4 composite increases by a factor of six compared with nAl to 0.66 MPa·μs−1. Evidence of hydrogen release (∼730 K) from Temperature-jump time-of-flight mass spectrometry (T-Jump TOFMS) of a-nSi/KClO4 suggests the creation of Si dangling bonds prior to ignition (∼820 K), which then react exothermically with oxygen liberated from KClO4, leading to ignition. Explosive reaction of H2/O2 mixture likely contributes to the rapid pressure rise. The enhanced energetic performance of hydrogenated a-nSi compared to its crystalline counterpart suggests that incorporation of hydrogen is a promising strategy for improving the performance of nanoenergetic materials.

Low thermal stability is a major limitation of diamond-like carbon (DLC) films, especially amorphous hydrogenated carbon (a-C:H) films, inhibiting their use in several applications. Adding silicon and oxygen to a-C:H increases thermal stability, but mechanisms for this increase are unknown. Reactive molecular dynamics (MD) simulations using the ReaxFF potential were performed on undoped a-C:H and a-C:H containing Si and O (a-C:H:Si:O). As in experiments, the simulated a-C:H:Si:O demonstrated increased thermal stability compared to a-C:H. Atomistic thermal degradation pathways were examined to understand the origins of the enhanced thermal stability of a-C:H:Si:O compared to a-C:H. The primary thermal degradation pathway in undoped a-C:H was the breaking of tensile strained C-C bonds resulting in a transformation of sp3 to sp2-hybridized carbon. The presence of Si suppresses this mechanism by decreasing the frequency of occurrence of highly strained C-C bonds in the unannealed structure. This is due to the longer C-Si equilibrium bond length compared to C-C bonds, which allows the Si-doped films to accommodate higher structural disorder.

Harsh environments pose materials durability challenges across the automotive, aerospace, and manufacturing sectors, and beyond. While amorphous carbon materials have been used as coatings in many environmentally-demanding applications owing to their unique mechanical, electrical, and optical properties, their limited thermal stability and high reactivity in oxidizing environments have impeded their use in many technologies. Silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) films are promising for several applications because of their higher thermal stability and lower residual stress compared to hydrogenated amorphous carbon (a-C:H). However, an understanding of their superior thermo-oxidative stability compared to a-C:H is lacking, as it has been inhibited by the intrinsic challenge of characterizing an amorphous, multi-component material. Here, we show that introducing silicon and oxygen in a-C:H slightly enhances the thermal stability in vacuum, but tremendously increases the thermo-oxidative stability and the resistance to degradation upon exposure to the harsh conditions of low Earth orbit (LEO). The latter is demonstrated by having mounted samples of a-C:H:Si:O on the exterior of the International Space Station via the Materials International Space Station (MISSE) mission 7b. Exposing lightly-doped a-C:H:Si:O to elevated temperatures under aerobic conditions or to LEO causes carbon volatilization in the near-surface region, producing a silica surface layer that protects the underlying carbon from further removal. These findings provide a novel physically-based understanding of the superior stability of a-C:H:Si:O in harsh environments compared to a-C:H.

Phosphonium phosphate ionic liquids (ILs) are promising lubricant additives for engine oils owing to a combination of good tribological performance and attractive properties, such as high thermal stability and good miscibility with mineral and synthetic oils. Here, we evaluate the dependence of the lubricating performance of trihexyltetradecylphosphonium ([P6,6,6,14])-based ILs when used in steel/steel contacts on the relative concentration of bis(2-ethylhexyl)phosphate ([DEHP]) and bromide (Br-) anions. The results indicate no changes in friction and wear upon increasing the [P6,6,6,14]Br-to-[P6,6,6,14][DEHP] volume ratio up to 0.2:1, while a further increase in this ratio leads to a reduction of friction and wear. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry measurements highlight that the dependence of the lubricating properties of the ILs on the [P6,6,6,14]Br-to-[P6,6,6,14][DEHP] ratio originates from the balance between corrosivity and surface reactivity of this IL: while [DEHP] acts as corrosion inhibitor in the non-contact region, the formation of species containing phosphorus-oxygen moieties in the wear track as a result of the hydrolysis of phosphonium ions increases the surface coverage of phosphorus. This is proposed to decrease friction by decreasing adhesion at steel/steel contacts and lowering the interfacial shear strength.

Made available in DSpace on 2018-12-11T17:23:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-11-05 A strain isolated from Kombucha tea was isolated and used as an alternative bacterium for the biosynthesis of bacterial cellulose (BC). In this study, BC generated by this novel bacterium was compared to Gluconacetobacter xylinus biosynthesized BC. Kinetic studies reveal that Komagataeibacter rhaeticus was a viable bacterium to produce BC according to yield, thickness and water holding capacity data. Physicochemical properties of BC membranes were investigated by UV–vis and Fourier transform infrared spectroscopies (FTIR), thermogravimetrical analysis (TGA) and X-ray diffraction (XRD). Additionally, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were also used for morphological characterization. Mechanical properties at nano and macroscale were studied employing PeakForce quantitative nanomechanical property mapping (QNM) and dynamic mechanical analyzer (DMA), respectively. Results confirmed that BC membrane biosynthesized by Komagataeibacter rhaeticus had similar physicochemical, morphological and mechanical properties than BC membrane produced by Gluconacetobacter xylinus and can be widely used for the same applications. Laboratório de Biopolimeros e Biomateriais (BIOPOLMAT) Centro Universitário de Araraquara, Araraquara Group ‘Materials + Technologieś (GMT) Department of Chemical and Environmental Engineering Engineering College of Gipuzkoa University of the Basque Country (UPV/EHU), Plaza Europa 1 Laboratório de Pesquisa Desenvolvimento & Inovação Apis Flora Ind. Coml. Ltda, Ribeirão Preto Institute of Chemistry-São Paulo StateUniversity-UNESP Institute of Chemistry-São Paulo StateUniversity-UNESP

Due to their increased stability in extreme environments, relative to amorphous hydrogenated carbons (a-C:H), amorphous thin film silicon oxide-doped hydrogenated amorphous carbons (a-C:H:Si:O) are being commercially developed as solid lubricants and protective coatings. Although various properties of a-C:H:Si:O have been investigated, no definitive structure of a-C:H:Si:O has ever been proposed, nor has its thermally-induced structural evolution been thoroughly studied. The aim of this work is to better understand the structure of a-C:H:Si:O through solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies. Deeper insights into the thermally-driven structural evolution are obtained by annealing a-C:H:Si:O between 50 °C and 300 °C under anaerobic conditions and taking NMR/EPR measurements after each step. EPR results show that the number of paramagnetic defects decreases by 70% with annealing at 300 °C. 1H NMR shows the hydrogen concentration decreases with annealing temperature from 2 × 1022 g−1, and then levels off at approximately 0.7 × 1022 g−1 for anneals between 200 °C and 300 °C. The carbon–silicon–oxygen network exhibits some structural reorganization, seen directly as a slight increase in the sp2/sp3 ratio in the 13C NMR with annealing. These results combined with relaxation data are interpreted according to a two-component structure largely defined by differences in hydrogen and defect contents.

CZTS thin films were synthesized by annealing of Zn, Cu, and Sn stacked layers under sulfur atmosphere. Pressure was controlled by varying the mass of the sulfur charges introduced into the closed annealing chamber. Films sulfurized at higher pressure show clear segregation of hexagonal SnS 2 , suggesting that Sn reacts with gaseous sulfur to form a solid-state phase, leading to an inhomogeneous 3D film morphology. Lower pressure synthesis yields uniform layers mainly composed of CZTS. Variations in film morphology suggest that different reaction pathways take place as the pressure is raised. Formation of gaseous SnS is favored at lower pressure, while nucleation of solid SnS 2 preferentially occurs at higher pressure. Influence of the cooling rate after annealing was also studied. We have found that this strongly affects the film stoichiometry, while the film morphology did not show relevant dependence on this parameter.

We demonstrate the synthesis of yolk–shell particles using spray-pyrolysis, a technique with proven scalability to industrial production level. Nickel oxide (shell)–silicon (yolk) particles are produced using a single-step aerosol reaction from a mixture of commercial, off-the-shelf precursors. After coating and annealing in the presence of polyvinylpyrrolidone, the nickel oxide shell is converted into a porous nickel cage enclosing the silicon particles. The polymer decomposition leads to the formation of an amorphous carbon layer surrounding the nickel cage. This structure maintains a high specific discharge capacity after more than 100 cycles (~1400 mAh/g at the 110th cycle with a 0.5 C discharge rate, on a silicon basis) when used as anode for lithium-ion batteries. Keywords: Lithium ion batteries, Yolk–shell nanoparticles, Nickel, Silicon nanoparticles

We propose a novel approach to the fabrication of silicon-containing anodes for lithium-ion batteries. Our approach is based on a liquid dispersion comprising of silicon quantum dots, carbon nanotubes and polyvinylpirrolidone (PVP) as a polymer additive. Coating of this dispersion onto copper foil followed by annealing in inert atmosphere allows the realization of a structure with good electrical conductivity, high specific surface area and with a carbon-based coating preventing the direct contact between the silicon particles and the electrolyte. This structure maintains a specific charge capacity of approximately 1000 mAh g −1 for 200 cycles and reaches a coulombic efficiency of 99.8%. The addition of PVP is a simple and scalable way of realizing, after annealing, a carbon-based matrix which surrounds the silicon particles and which greatly enhances the stability of the battery. The proposed process is based on commercially available carbon nanotubes, on silicon quantum dots which are produced using a scalable plasma-enhanced chemical vapour deposition technique, and is compatible with large area coating and processing techniques. The fabrication protocol described in this contribution represents a step towards the successful commercial utilization of silicon-based nanomaterials for energy storage applications.

In this paper we demonstrate the synthesis of high quality crystalline silicon–germanium alloy nanoparticles using the combination of a non-thermal plasma reactor and chlorinated precursors. The produced particles have potential applications in several fields including for the production of advanced thermoelectric materials. The use of silicon and germanium tetrachloride has clear advantages with respect of hydrogenated precursors (silane and germane) from both the cost and safety points of view. Nanocrystals smaller than 10 nm have been produced with excellent control over the alloy composition. Characterization by Raman, XRD and TEM confirm that the produced material is not composed of a mixture of silicon and germanium nanoparticles, but rather by an ensemble of crystals in which each particle is composed of an alloy of silicon and germanium.

The influence of metallic and oxidized iron/steel on the reactivity of triphenyl phosphorothionate (TPPT) in oil solution at 473 K was investigated by means of FT-IR, NMR and XPS. The FT-IR and NMR results show that the degradation of TPPT was catalyzed by metallic and oxidized iron powder and started with the breakage of the PS bond to form triphenyl phosphate (TPP). The results of the XPS sputter depth profile show the multilayer structure of the thermal film formed on 100Cr6 steel filings immersed for 72 h in TPPT solution heated at 473 K.

Cyst growth and expansion in autosomal dominant polycystic kidney disease (ADPKD) has been attributed to numerous factors, including ATP, cAMP and adenosine signalling. Although the role of ATP and cAMP has been widely investigated in PKD1-deficient cells, no information is currently available on adenosine-mediated signalling. Here we investigate for the first time the impact of abnormalities of polycystin-1 (PC1) on the expression and functional activity of adenosine receptors, members of the G-protein-coupled receptor superfamily. Pharmacological, molecular and biochemical findings show that a siRNA-dependent PC1-depletion in HEK293 cells and a PKD1-nonsense mutation in cyst-derived cell lines result in increased expression of the A3 adenosine receptor via an NFkB-dependent mechanism. Interestingly, A3 adenosine receptor levels result higher in ADPKD than in normal renal tissues. Furthermore, the stimulation of this receptor subtype with the selective agonist Cl-IB-MECA causes a reduction in both cytosolic cAMP and cell proliferation in both PC1-deficient HEK293 cells and cystic cells. This reduction is associated with increased expression of p21waf and reduced activation not only of ERK1/2, but also of S6 kinase, the main target of mTOR signalling. In the light of these findings, the ability of Cl-IB-MECA to reduce disease progression in ADPKD should be further investigated. Moreover, our results suggest that NFkB, which is markedly activated in PC1-deficient and cystic cells, plays an important role in modulating A3AR expression in cystic cells.

While silicon's optical properties are improved at the nanoscale, they also become highly sensitive to the properties of the surfaces and interfaces of silicon nanostructures. For instance, while reported quantum yields for photoluminescence of silicon quantum dots covered by a native oxide are often in the few percent range, quantum yields as high as 30% have been found in quantum dots whose surfaces were passivated by covalently bonded organic molecules. In this paper, we describe an approach that is based on the gas phase synthesis of silicon quantum dots in a nonthermal plasma, and the subsequent organic surface passivation in the liquid phase. Nanocrystals are formed within a few milliseconds with a high mass yield in a nonthermal plasma. Various organic ligands such as octadecene, dodecence, and styrene are grafted onto the nanocrystal surfaces in a reaction known as hydrosilylation. Materials are characterized through transmission electron microscopy, atomic force microscopy, and fluorescence measurements. The particle size distributions are found to be relatively monodisperse and are well controllable through the plasma process parameters. Photoluminescence quantum yields as high as 60–70% have been achieved for particles luminescing in the red range of the visible spectrum.

G93A Cu/Zn superoxide dismutase (SOD1), a human mutant SOD1 associated with familial amyotrophic lateral sclerosis, increased the toxicity of the mitochondrial toxin rotenone in the NSC-34 motoneuronal cell line. G93ASOD1 cells died more than untransfected and wild-type SOD1 cells after 6 and 24h exposure to 12.5 microM rotenone. Biparametric flow cytometry showed that rotenone induced rapid hyperpolarization of mitochondrial membrane potential (deltapsi(m)) in all the cell lines, followed by depolarization, and then by cell death. However, G93ASOD1 mitochondria were significantly more likely to shift from a hyperpolarized to a depolarized condition, and within the still viable cell population there was a higher proportion with depolarized mitochondria, a condition that can be envisaged as a commitment to cell death. ATP, which is needed to prevent loss of deltapsi(m), decreased more rapidly and to a greater extent in rotenone-treated G93ASOD1 cells than in the untransfected and wtSOD1cells. In all the cell lines, 1h after rotenone exposure, mitochondrial hyperpolarization was accompanied by the formation of a comparable amount of reactive oxygen species. However, G93ASOD1 cells reached the highest reactive oxygen species level since their basal level was higher than in untransfected and wild-type SOD1 cells. Our findings indicate that the mutant protein G93ASOD1 enhances the vulnerability of motor neurons to rotenone by mechanism(s) involving oxidative stress and perturbed mitochondrial homeostasis. This suggests that motor neurons from individuals carrying the mutant G93ASOD1 are at greater risk of death after inhibition of the electron transport chain.

The motor neuron-like cell line NSC-34 has become a widely used in vitro model for motor neuron biology and pathology. We established a tetracycline-regulated gene expression system in this cell line by stably transfecting pTet-Off, which codifies for the tetracycline transactivator, the regulatory protein tTA. The monoclonal cell lines (NSC-34-tTA) were evaluated for the presence of functional tTA after transient transfection with pBI-EGFP, analyzing the expression of the reporter gene enhanced green fluorescent protein. We evaluated the regulation of tTA function with doxycycline using fluorescence microscopy and quantitative cytofluorimetric analysis on viable transfected cells. The best-regulated cell line (NSC-34-tTA40) had a 66.4-fold induction for the reporter gene fluorescence in comparison to NSC-34. Alpha-tubulin, GAP-43 and phosphorylated medium and heavy neurofilaments, proteins of importance for the motor neuronal phenotype, were evident in NSC-34-tTA40 by Western blot and immunocytochemistry; they were expressed similarly in NSC-34-tTA40 and in NSC-34. The cDNA of human Cu/Zn superoxide dismutase, a gene of interest for amyotrophic lateral sclerosis, was cloned into pBI-EGFP, downstream of the tetracycline-responsive bidirectional promoter. This plasmid was transiently transfected into NSC-34-tTA40, and the functionality of bidirectional transcription was verified by determining the expression of enhanced green fluorescent protein and of human Cu/Zn superoxide dismutase. Both proteins were regulated by doxycycline. This novel cell line, NSC-34 tTA40, that permits tetracycline-regulated gene expression may prove useful to unravel the mechanisms of motor neuron degeneration.

Background/Aims : The role of oxidative stress in diclofenac hepatotoxicity is still not clear. This study examined whether the drug induced heme oxygenase-1 (HO-1), a stress protein. Methods : HO-1 mRNA and HO activity were measured in mouse liver and in rat hepatocytes after treatment with diclofenac parallel to release of serum alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) as a marker of hepatic damage. Results : HO-1 was transcriptionally and dose-dependently induced by diclofenac in mouse liver and rat hepatocytes. HO-1 mRNA, ALT and SDH peaked at the same time. Mechanistic studies revealed that the drug synergized with buthionine sulfoximine (BSO) in lowering hepatic glutathione, increased the formation of reactive oxygen intermediates and activated NF-κB and AP-1 in rat hepatocytes. HO-1 induction and hepatic damage were increased by BSO and only HO-1 induction was attenuated by the antioxidant N -acetylcysteine. HO-1 induction was also reduced by the cytochrome P-450 inhibitors ketoconazole and tranylcypromine, concomitantly with a significant decrease in the formation of diclofenac oxidative metabolites, which may give rise to reactive compounds. Conclusions : Acute treatment with diclofenac induces HO-1 in rodent hepatocytes. Induction is influenced by changes in the cellular redox states and by cytochrome P-450 activity and gives a new insight into the response of the liver to diclofenac.