Dry Nitrogen Atmosphere Research Articles

Ruthenium complexes as nitric oxide donors and scavengers. Synthesis and crystal and molecular structure for mer,trans-[RuIICl3(NO+)(N-4-ethylisonicotinate)2], and mer,trans-[RuIIICl3(N-CH3CN)(N-4-ethylisonicotinate)2] as obtained via UV-photochemical activation of {RuII(NO+)}3+-core parent complex in acetonitrile solution

The synthesis of mer,trans-[RuIICl3(NO+)(EINT)2] (EINT=N-4-ethylisonicotinate), 1, was achieved by carefully working under ultrapure nitrogen atmosphere, by mixing RuIIICl3(NO)·H2O and EINT (1:2M ratio in anhydrous ethanol) under stirring and at reflux conditions. Single crystals of 1 suitable for X-ray diffraction XRD techniques were also obtained by slow evaporation of solvent under nitrogen from the mother alcoholic solution. The IR spectrum of the solid (KBr matrixes) showed the characteristic sharp and intense band (1866cm−1) relevant to the N–O stretching vibration for the nitrosyl ligand (RuIINO+ core). Then, on irradiating at 25°C a solution of 1 in ultrapure acetonitrile (contained in quartz cuvette) under an UV source (250 throughout 366nm) a color turning from pink to yellow occurred. After a prolonged irradiation (250nm for at least 6h) the cuvette (yellow solution) was stored in a dry nitrogen atmosphere and allowed to slowly concentrate via spontaneous solvent evaporation. The solution produced brown crystals as parallelepipeds, suitable for XRD data collection, that belong to the monoclinic system, C2/c space group, and the molecular structure (mer,trans-[RuIICl3(N-NCCH3)(EINT)2], 2) consists of complex molecules that are mostly paired via stacking interactions that involve the pyridine moiety and through (ethyl)CH3⋯Cl(Ru), (pyridine)CH⋯Cl(Ru) and (ethyl)CH3⋯O(C) hydrogen bond type interactions. The crystals of the parent nitrosyl complex belong to the orthorhombic Pccn space group and the complex molecule has three chlorido ligands in the equatorial positions and two EINT ligands in the axial positions. The nitrosyl ligand occupy two positions that are trans to each other and have half occupancy each.

Proton conductive composite electrolytes in the KH2PO4–H3PW12O40 system for H2/O2 fuel cell operation

Potassium dihydrogen phosphate (KH2PO4, PDP) and phosphotungstic acid (H3PW12O40, PTA) were mechanochemically milled in dry nitrogen atmosphere to synthesize highly proton conductive composite electrolytes in the PDP–PTA system. Proton conductivity of these composites significantly depends on the molar ratio of PDP and PTA in the temperature range of room temperature (RT) to 180°C under both anhydrous and hydrous conditions, and the composites exhibited proton conductivities more than 2 orders of magnitude higher than those of the raw substances. Furthermore, when the binders-free PDP–PTA composites in pellet form were used as an electrolyte in H2/O2 fuel cell systems, higher open circuit potential than 0.9V and a maximum power density of 20mWcm−2 were achieved during the single cell test. The structural studies and solid-state proton-magic angle spinning-nuclear magnetic resonance (1H MAS-NMR) results showed new chemical interaction between dihydrogen phosphate anion and K-substituted PTA via ion-exchange and hydrogen bonds, which manifested the essential role of a newly developed hydrogen-bonding network to the improvement of protic conduction behavior, leading to the increase in the electrochemical performances of these composites.

Measurement of the Performance of an Agricultural Residue-based Activated Carbon Aiming at the Removal of 4-chlophenol from Aqueous Solutions

Looking for versatile adsorbent materials for industrial and environmental applications is a domain of research under active investigation now. Deglet-Nor date variety is one of the most important biomass resource in the south of Algeria, particularly in the region of Ouargla. Date stones, as an agricultural residue, are often unreasonably exploited in this region. Accordingly, in an attempt to valorize this abundant, low cost byproduct, we have studied the micro porosity of this raw material by carrying out two procedures. First, pyrolysis and physical activation were performed respectively under dry nitrogen and carbon dioxide atmospheres. Second, the resulting activated carbons were t h e n characterized by measuring their specific surface area (≈ 782 m2/g) and t h e m i c r o porous volume (≈ 0.27cm3 .g-1). The capacity of adsorption was tested by removing 4-chlorophenol from aqueous solutions. Data analysis show that the better fit was obtained with Langmuir model where the capacity of adsorption was about 390mg.g-1.

Irradiation of KU1 and KS-4V substrate SiO2 overcoated Al mirrors

Previous work on overcoated dielectric mirrors identified several radiation problems; UV–visible reflectivity degradation, unreliability of manufacturers coating specifications, and conversion of SiO coatings to SiO2 leading to swelling and cracking, and hence possible corrosion during LOCAs (loss of coolant accident). We report the results obtained for gamma and neutron irradiation of prototype mirrors with KU1 and KS-4V high purity silicas replacing the standard Pyrex substrate to overcome the problem of activation due to high impurity content. To avoid the SiO to SiO2 conversion problem, the Al layer has been overcoated with SiO2. The mirrors show high reflectivity (>80%) down to 200nm. After gamma irradiation at 170°C in a dry nitrogen atmosphere to 10MGy, no degradation in reflectivity was observed. They were then neutron irradiated in vacuum at 35°C to 6.8×1016n/cm2 (fast fluence) and reflectivity examined with a specially designed spectrometer system with a remote integrating sphere for hot cell use. Again no degradation in reflectivity was observed.

Operating the GridPix detector in dark matter search experiments

The DARWIN (dark matter WIMP search with noble liquids) design study aims to use liquid argon and liquid xenon targets to look for nuclear recoils due to weakly interacting massive particles (WIMPs). To measure the recoil energy in dual-phase noble gas time projection chambers the combination of scintillation and ionisation detection is used to discriminate nuclear from electron recoils. Current experiments use an array of photomultiplier tubes to detect the primary scintillation and the ionisation electrons via secondary scintillation in the gas phase. Within the research framework for DARWIN, one candidate for an alternative direct charge readout is GridPix, a micro-pattern gaseous detector composed of a Micromegas-like amplification grid over the Timepix 65k pixel readout chip. It can achieve a single-electron detection efficiency of up to 98% and has thus great potential to identify the ionisation electrons in dark matter search experiments. The main challenges for this application are low outgassing, thermal robustness, and operation in pure (thus quencher-free) noble gas. To investigate its applicability we operated a GridPix detector in an argon cryostat. We proved GridPix's performance in pure argon. The gas amplification was confirmed in pure argon in the broad temperature range from 300K down to 87K. Additionally, we discuss results of thermal tests of GridPix devices at liquid xenon temperature in a dry nitrogen atmosphere.

The correlation between the ethylene response and its oxidation over TiO2 under UV irradiation

Abstract The anatase and rutile TiO 2 film sensors were prepared by drop-coating method with calcination at 450 and 600 °C, respectively. After tested the ethylene sensing property over the as-prepared TiO 2 sensors under UV irradiation, it was found that the anatase TiO 2 as well as the rutile sensor exhibited a response to ethylene in the dry nitrogen atmosphere, but with anatase showing a much lower response to ethylene (almost no response) than rutile in the dry air atmosphere (containing oxygen). Moreover, this difference to the ethylene response between the anatase TiO 2 sensor and the rutile one was also observed in a wet air atmosphere under UV irradiation. Based on the results of photocatalytically oxidizing ethylene over anatase and rutile TiO 2 , it is proposed that the weak gas response to ethylene over the anatase TiO 2 under UV irradiation can be attributed to the oxidation of ethylene itself. This also suggests that a good photo-assisted semi-conductor sensor should have a strong photoresponse property but a weak photocatalytic performance for the sensed gas.

Anhydrous protic conduction of mechanochemically synthesized CsHSO4–Azole-derived composites

Solid inorganic–organic composites were synthesized for the application as an electrolyte in fuel cells. CsHSO4 (CHS) was mechanochemically treated with Azole, which has a five-membered nitrogen heterocyclic ring such as imidazole (Iz), 1,2,4-triazole (Tz) and benzimidazole (Bz), in dry nitrogen atmosphere to obtain composites with xCHS·(100−x)Azole (x=90–50mol%). Chemical interactions between CHS and Azoles after solid-state mechanochemical treatment were confirmed from structural observation. The proton conductivity of the composites was largely increased by introduction of Azoles, particularly in the lower temperature region than a superprotic phase-transition temperature of CHS and melting points of Azoles. Proton conductivities of 80CHS·20Iz and 80CHS·20Tz composites ranged from 7×10−4 to 2×10−3Scm−1 over a wide temperature range (60–160°C). However, CHS–Bz composites showed lower conductivities due to the lower reactivity of Bz. Proton transfer in CHS–Azole composite systems includes the proton-hopping mechanism and self-dissociation, which probably supports protic diffusion, especially in low temperature regions.

Controlling Nanoscale Friction through the Competition between Capillary Adsorption and Thermally Activated Sliding

We demonstrate measurement and control of nanoscale single-asperity friction by using cantilever probes featuring an in situ solid-state heater in contact with silicon oxide substrates. The heater temperature was varied between 25 and 790 °C. By using a low thermal conductivity sample, silicon oxide, we are able to vary tip temperatures over a broad range from 25 ± 2 to 255 ± 25 °C. In ambient atmosphere with ∼30% relative humidity, the control of friction forces was achieved through the formation of a capillary bridge whose characteristics exhibit a strong dependence on temperature and sliding speed. The capillary condensation is observed to be a thermally activated process, such that heating in ambient air caused friction to increase due to the capillary bridge nucleating and growing. Above tip temperatures of ∼100 ± 10 °C, friction decreased drastically, which we attribute to controllably evaporating water from the contact at the nanoscale. In contrast, in a dry nitrogen atmosphere, friction was not affected appreciably by temperature changes. In the presence of a capillary, friction decreases at higher sliding speeds due to disruption of the capillary; otherwise, friction increases in accordance with the predictions of a thermally assisted sliding model. In ambient atmospheres, the rate of increase of friction with sliding speed at room temperature is sufficiently strong that the friction force changes from being smaller than the response at 76 ± 8 °C to being larger. Thus, an appropriate change in temperature can cause friction to increase at one sliding speed, while it decreases at another speed.

Mechanochemical synthesis of proton conductive composites derived from cesium dihydrogen phosphate and guanine

Solid inorganic–organic composites were synthesized from cesium dihydrogen phosphate (CsH2PO4, CDP) and guanine (C5H5N5O, Gn) to use the solid proton conductive electrolytes. CDP and Gn were mechanochemically milled in dry nitrogen atmosphere to obtain composites with xCDP·(100−x)Gn (x=90–50mol%). The changes in chemical structure, such as tautomerism of Gn and formation of hydrogen bond between CDP and Gn, after solid-state mechanochemical treatment, were confirmed from FT-IR study. The CDP-Gn composite electrolytes showed significantly higher proton conductivity than those of raw substances, particularly in the lower temperature region than the superprotic phase-transition temperature of CDP. The 80CDP·20Gn composite, for example, showed in anhydrous and hydrous proton conductivities from 2.4×10−5 to 8.1×10−4S cm−1, in dry nitrogen atmosphere, and from 1.3×10−4 to 1.3×10−3S cm−1, in humidified nitrogen atmosphere (pH2O=0.6atm) on heating in the temperature range between 80 and 180°C. From the FT-IR and impedance studies, tautomerism of Gn and newly developed hydrogen bonds between CDP and Gn are highly expected in the composites. These structural changes imply that a development of new chemical interactions to form the acid–base composite cluster is essential to improve the proton conductivity.

X-ray Absorption Fine Structure Evidence for Amorphous Zinc Sulfide as a Major Zinc Species in Suspended Matter from the Seine River Downstream of Paris, Ile-de-France, France

Zinc is one of the most widespread trace metals (TMs) in Earth surface environments and is the most concentrated TM in the downstream section of the Seine River (France) due to significant anthropogenic input from the Paris conurbation. In order to better identify the sources and cycling processes of Zn in this River basin, we investigated seasonal and spatial variations of Zn speciation in suspended particulate matter (SPM) in the oxic water column of the Seine River from upstream to downstream of Paris using synchrotron-based extend X-ray absorption fine structure (EXAFS) spectroscopy at the Zn K-edge. First-neighbor contributions to the EXAFS were analyzed in SPM samples, dried and stored under a dry nitrogen atmosphere or under an ambient oxygenated atmosphere. We found a sulfur first coordination environment around Zn (in the form of amorphous zinc sulfide) in the raw SPM samples stored under dry nitrogen vs an oxygen first coordination environment around Zn in the samples stored in an oxygenated atmosphere. These findings are supported by scanning electron microscopy and energy dispersive X-ray spectrometry observations. Linear combination fitting of the EXAFS data for SPM samples, using a large set of EXAFS spectra of Zn model compounds, indicates dramatic changes in the Zn speciation from upstream to downstream of Paris, with amorphous ZnS particles becoming dominant dowstream. In contrast, Zn species associated with calcite (either adsorbed or incorporated in the structure) are dominant upstream. Other Zn species representing about half of the Zn pool in the SPM consist of Zn-sorbed on iron oxyhydroxides (ferrihydrite and goethite) and, to a lesser extent, Zn-Al layered double hydroxides, Zn incorporated in dioctahedral layers of clay minerals and Zn sorbed to amorphous silica. Our results highlight the importance of preserving the oxidation state in TM speciation studies when sampling suspended matter, even in an oxic water column.

Solvent free, N,N′-carbonyldiimidazole (CDI) mediated amidation

The method involves CDI mediated amidation under solvent-free conditions. The protocol is green, simple, and scalable and has broad structural applicability. The protocol has also been used for BOC protection of amine. The protocol has reduced the time for CDI mediated amidation from 2–4h to 5–10min without the use of any dry organic solvent and nitrogen atmosphere.

Influence of Various Process Parameters on the Density of Sintered Aluminium Alloys

This paper presents the results of density measurements carried out on Alumix sintered parts. ECKA Alumix aluminium powders were used because of their wide application in the powder metallurgy industry. The compacts were produced using a wide range of compaction pressures for three different chemical compositions. The compacts were then sintered under a pure dry nitrogen atmosphere at three different temperatures. The heating and cooling rates were the same throughout the entire test. The results showed that the green density increases with compaction pressure, but that sintered density is independent of green density (compaction pressure) for each sintering temperature.

Reorganization of perylene bisimide J-aggregates: from delocalized collective to localized individual excitations

Water-induced reorganization of individual one-dimensional J-aggregates of perylene bisimide (PBI) dyes was observed by fluorescence microscopy. Fluorescence spectra and decay kinetics of individual J-aggregates immobilized on glass surfaces were measured under a dry nitrogen atmosphere and under humid conditions. The fluorescence properties of PBI J-aggregates arisen from collective excitons under dry nitrogen atmosphere were changed to those of non-interacting dye monomers when water vapor was introduced into the environment (sample chamber). Time-dependent changes of the fluorescence spectra and lifetimes upon exposure to water vapor suggest an initial coordination of water molecules at defect sites leading to the formation of H-type dimer units that act as exciton quenchers, and a subsequent slower disintegration of the hydrogen-bonded J-aggregate into monomers that lack resonance coupling. Our present studies resulted in a direct demonstration of how drastically the optical properties of molecular ensembles and characteristics of their excited states can be changed by delicate reorganization of dye molecules at nanometre scales.

Synthesis of new derivatives of 1-[1-(2-pyridyl)-imidazolidine-2-ylidene]-3-aryl(arylakyl)ureas

The synthesis and physicochemical properties of new 1-[1-(2-pirydyl)imidazoline-2-ylidene]-3-aryl(arylalkyl)ureas [I-VIII]. The title compounds were obtained by condensation of 1-(2-pirydyl)-2-aminoimidazoline-2 with aryl isocyanate or arylalkyl isocyanate in dichloromethane under the atmosphere of dry nitrogen. The reaction was conducted in the room temperature for 24 h. Considering the structure of obtained compounds it can be expected that these compounds can reveal pharmacological activity.

Work Function Based Hydrocarbon-Mix Sensing with Nanoparticles Functionalized WO3 Thick Films

Abstract In this work the sensitivity of pure and metal nanoparticles functionalized WO3 thick films towards hydrocarbon-mix (HC-Mix) has been studied based on work function readout by means of Kelvin Probe technique. Measurements have been performed in synthetic air and dry nitrogen atmosphere in the temperature range between 25° and 200 °C. The strongest signals were achieved with PtPd-nanoparticles functionalized WO3 thick layers at 120-140 °C. The influence of oxygen on the sensing mechanism has been discussed.

Tribological properties of ultrananocrystalline diamond films in various test atmosphere

Transformation from higher to ultra low friction coefficient was observed in ultrananocrystalline diamond film (UNCD) while changing the test atmospheric conditions. High friction coefficients were observed in dry argon and nitrogen atmosphere, however, low and ultra low friction coefficients were obtained in dry oxygen and in ambient atmospheric conditions, respectively. Wear rates follow the same trends as the friction coefficients. This fascinating behavior of friction and wear of UNCD film is explained by the chemical changes of sliding surfaces and extent of passivation of dangling covalent bonds.

Synthesizing white-luminescence SrS:Pr powder phosphor

This paper discusses several different methods of synthesizing SrS:Pr phosphor. It is shown that the brightest photoluminescence can be obtained by using strontium sulfide as the main starting substance and doping it with PrF3 in the presence of NaCl flux by roasting the mix in a dry nitrogen atmosphere with an addition of sulfur vapor. It is established that, to obtain luminescence of the SrS:Pr samples, it is necessary to anneal them in vacuum. The praseodymium concentration in the mix, the temperature, and the vacuum-annealing time were optimized, and this made it possible to maximize the photoluminescence brightness and achieve the highest perfection of the phosphor crystals. The synthesized SrS:Pr phosphor possesses white luminescence.

Thermal stability and crystallization behavior of TiO2 doped ZBLAN glasses

ZBLAN glasses with the composition (in mol%) of (100−x)(53 ZrF4+19 BaF2+5LaF3+3AlF3+20NaF)+xTiO2 (x=0, 1.0 and 2.0mol%) were prepared using a conventional melting technique in dry nitrogen atmosphere. The thermal stability, glass-forming ability, and crystallization kinetics of the ZBLAN system as a function of the TiO2 concentrations were investigated by Differential Scanning Calorimetry (DSC). Also, the crystalline phases were determined by X-ray Diffraction (XRD). Our study indicates that adding TiO2 in a fluoride system improves the thermal parameters of the glass, which is interesting for applications as optical fiber.

Water and oxygen induced degradation of small molecule organic solar cells

Small molecule organic solar cells were studied with respect to water and oxygen induced degradation by mapping the spatial distribution of reaction products in order to elucidate the degradation patterns and failure mechanisms. The active layers consist of a 30 nm bulk heterojunction formed by the donor material zinc-phthalocyanine (ZnPc) and the acceptor material Buckminsterfullerene (C 60) followed by 30 nm C 60 for additional absorption. The active layers are sandwiched between 6 nm 4,7-diphenyl-1,10-phenanthroline (Bphen) and 30 nm N, N′-diphenyl- N, N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine p-doped with C 60F 36 (MeO-TPD:C 60F 36), which acted as hole transporting layer. Indium-tin-oxide (ITO) and aluminum served as hole and electron collecting electrode, respectively. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) in conjunction with isotopic labeling using H 2 18O and 18O 2 provided information on where and to what extent the atmosphere had reacted with the device. A comparison was made between the use of a humid (oxygen free) atmosphere, a dry oxygen atmosphere, and a dry (oxygen free) nitrogen atmosphere during testing of devices that were kept in the dark and devices that were subjected to illumination under simulated sunlight. It was found that water significantly causes the device to degrade. The two most significant degradation mechanisms are diffusion of water through the aluminum electrode resulting in massive formation of aluminum oxide at the BPhen/Al interface, and diffusion of water into the ZnPc:C 60 layer where ZnPc becomes oxidized. Finally, diffusion from the electrodes was found to have no or a negligible effect on the device lifetime.

Establishing a new conductance stopped-flow apparatus to investigate the initial fast step of reaction between 1,1,1-trichloro-3-methyl-3-phospholene and methanol under a dry inert atmosphere

In the present work, for the first time, investigation of the initial fast step of reaction between 1,1,1-trichloro-3-methyl-3-phospholene (TCMP) and methanol was studied under a dry inert atmosphere by a newly constructed CSF apparatus by means of a further development in the configuration of the previous stopped-flow spectrophotometer (SFS). Hence, it was necessary to make many changes to the stopped-flow apparatus: replacement of the spectrophotometer amplifier with a conductance amplifier and the use of a conductivity cell to replace the optical one. The conductivity cell was made of polyethylene capillary tube (1 mm internal diameter; i.d.) and its inside dimensions were 1 mm i.d. × 3 mm long. Two tube electrodes which are made of stainless steel (0.8 mm i.d. × 14 mm long) were fixed at opposite ends of the observation cell and their outer surfaces were connected to the conductivity bridge amplifier by the two lead wires. The mixer was a 3-way Teflon valve and the distance between the mixer and the end of the observation cell was 30 mm. For each run, at least 24 µL of solution was required for a typical trace with a dead time of about 5 ms. Because of the extreme sensitivity of TCMP to moisture, the stopped-flow (CSF) apparatus was used inside a glove bag under a dry nitrogen atmosphere. Kinetic parameters for pseudo first-order reaction involving k(obs) = 30 s(-1) at 22 °C and activation energy E(a) = 13.55 KJ mol(-1) were successfully calculated for the initial fast step of the reaction between TCMP and methanol at 22 °C.