OH Band Research Articles

Optical emission spectra analysis of thermal plasma treatment of poly(vinyl chloride)

Abstract Decomposition of poly(vinyl chloride) (PVC) was investigated in radiofrequency thermal plasma in neutral, oxidative and reductive conditions. Optical emission spectroscopy (OES) was applied for the characterization of the plasma column. OES was used to identify active plasma components such as excited atoms, ions, radicals and molecules. The spectra were dominated by molecular C2, CN, OH, and CH bands, and atomic H, Ar, C, Cl and O lines. Emission intensities of main species were monitored versus various experimental parameters. The rotational-vibrational temperatures determined from different bimolecular species were considered in the range of 2000–6400 K. Solid soot samples were collected and purified to investigate the possibility of graphene formation as a by-product of the decomposition process.

Dual-template synthesis of nanostructured CoAPSO-34 used in methanol to olefins: Effect of template combinations on catalytic performance and coke formation

Methanol conversion to light olefins was investigated over SAPO-34 catalysts with Co introduction exploring the effect of different mixed templates. Applying mixed templates resulted in enhancement of catalyst life time and causing the reduction in catalyst preparation costs compared to those prepared with single template. Current research was focused on the synthesis of CoAPSO-34 catalysts with various mixtures of templates including TEAOH template. Three sets of mixed templates are taken into account for CoAPSO-34 synthesis, being TEAOH/TEA, TEAOH/DEA and TEAOH/morpholine with constant composition of 50%:50%. The catalysts were prepared via hydrothermal method and characterized with XRD, FESEM, PSD, TEM, EDX, BET and FTIR techniques. Nanostructured catalysts synthesized with TEAOH/DEA and TEAOH/morpholine mixtures exhibit high crystallinity evidenced by XRD analysis. TEAOH/TEA mixed template has the smallest particle size and the most uniform particle size distribution. Application of TEAOH/DEA and TEAOH/morpholine binary templates resulted in higher dispersion of Si and Co metals. Methanol to light olefins reaction was carried at different reaction temperatures. The stability test was conducted maintaining at constant temperature, molar feed ratio and GHSV to distinguish the effect of time on stream. In comparison, later emergence of DME in the products stream for the catalyst prepared with TEAOH/morpholine can be due to its higher crystallinity, better Si distribution and higher structural OH bands evidenced by XRD, EDX and FTIR techniques, respectively. Moreover, TGA, BET and FTIR techniques were implemented to characterize the coke deposit.

Estimation of combustion air requirement and heating value of fuel gas mixtures from flame spectra

This paper explores an optical method for evaluating the quality of fuel gases with uncertain composition. A spectrometer is used to acquire the radiation from flames generated with different fuel gas mixtures. Natural gas flame spectra are known to have features which vary with air/fuel ratio. In the current study flame spectra were collected from a number of fuel gas mixtures consisting of a reference hydrocarbon gas and varying amounts of a low calorific gas. During these tests the fuel flow rate was kept constant and the air flow rate was varied to generate flames with different air/fuel ratios. Analysis of the spectra showed that as air is decreased from a value greater than the stoichiometric requirement for the reference gas the OH band intensity goes through a maximum and decreases at lower air flow rates. The air flow rate at which the OH maximum occurs is correlated to the stoichiometric or combustion air requirement and the higher heating value, which are fuel quality parameters for that mixture. This observation suggests the basis for a method which has the potential to be designed and applied for estimating the combustion air requirement and heating value of gas mixtures with unknown fuel properties. To the best of our knowledge very little research is reported in literature on the application of flame emission spectroscopy for direct fuel quality evaluation.

Development of dense films from Melia azedarach polysaccharides

ABSTRACTThe aim of this work was to prepare dense films from polysaccharides extracted from Melia azedarach (MA) to be used e.g. in agricultural industry. Crosslinking of MA films with glutaraldehyde (Glu) through immersion method were performed. Structural features of films were elucidated by FTIR and XRD analysis. The influence of crosslinking in mechanical properties, water uptake and water vapor permeation was evaluated. Results showed neat Melia azedarach film presented high elongation and elastic modulus. Hydroxyl functional groups present in MA were reacted with glutaraldheyde to render a crosslinked matrix. It was observed through FTIR analysis that OH band reduces intensity due to the formation of acetal linkage, as the crosslinking time increases. XRD evidenced structural changes in MA arrangement with the crosslinking time. Chemical crosslinking during 12 h and 24 h rendered insoluble but less deformable films. Water uptake and water vapor permeability were reduced as the crosslinking time increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41624.

Identification of hydrogen defects linked to boron substitution in synthetic forsterite and natural olivine

Experimental and theoretical evidence for the coupled substitution of B and H in synthetic forsterite and a natural olivine is presented. The intensities of OH bands at 3704 cm -1 (//z), 3598 cm -1 (//x,y), and 3525 cm -1 (//x) in a heterogeneous B-doped synthetic forsterite crystal matches the zoning of B concentration measured by ion probe. The two anti-symmetric stretching vibrations of BO 3 groups occur at 1301 cm -1 (//x) and 1207 cm -1 (//z) for the 10 B and at 1256 and 1168 cm -1 for the 11 B isotope. A microscopic model of the mixed (B,H) defect that accounts for experimental observations is obtained from quantum mechanical calculations. The BO 3 group lies on the (O3-O1-O3) face of the vacant Si site and the H atom is bonded to the O2 atom at the remaining apex. The occurrence of the same OH bands associated with v 3 BO 3 vibrations in a natural olivine sample from Pakistan confirms the occurrence of this defect in nature. The three diagnostic OH bands can be used as a signature of H associated with boron substitution in olivine and forsterite, leading to a quantitative analysis of their contribution to H-defects.

Vibrational spectroscopic study of poldervaartite CaCa[SiO3(OH)(OH)

We have studied the mineral poldervaartite CaCa[SiO3(OH)(OH)] which forms a series with its manganese analogue olmiite CaMn[SiO3(OH)](OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is reasonably pure and contains only calcium and manganese with low amounts of Al and F. Thermogravimetric analysis proves the mineral decomposes at 485°C with a mass loss of 7.6% compared with the theoretical mass loss of 7.7%. A strong Raman band at 852cm−1 is assigned to the SiO stretching vibration of the SiO3(OH) units. Two Raman bands at 914 and 953cm−1 are attributed to the antisymmetric vibrations. Intense prominent peaks observed at 3487, 3502, 3509, 3521 and 3547cm−1 are assigned to the OH stretching vibration of the SiO3(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a detailed assessment of the molecular structure of poldervaartite.

Development of thermoplastic starch blown film by incorporating plasticized chitosan

The objective of the present work was to improve blown film extrusion processability and properties of thermoplastic starch (TPS) film by incorporating plasticized chitosan, with a content of 0.37–1.45%. The effects of chitosan on extrusion processability and melt flow ability of TPS, as well as that on appearance, optical properties, thermal properties, viscoelastic properties and tensile properties of the films were investigated. The possible interactions between chitosan and starch molecules were evaluated by FTIR and XRD techniques. Chitosan and starch molecules could interact via hydrogen bonds, as confirmed from the blue shift of OH bands and the reduction of V-type crystal formation. Although the incorporation of chitosan caused decreased extensibility and melt flow ability, as well as increased yellowness and opacity, the films possessed better extrusion processability, increased tensile strength, rigidity, thermal stability and UV absorption, as well as reduced water absorption and surface stickiness. The obtained TPS/chitosan-based films offer real potential application in the food industry, e.g. as edible films.

Advanced mesospheric temperature mapper for high-latitude airglow studies.

Over the past 60 years, ground-based remote sensing measurements of the Earth's mesospheric temperature have been performed using the nighttime hydroxyl (OH) emission, which originates at an altitude of ∼87 km. Several types of instruments have been employed to date: spectrometers, Fabry-Perot or Michelson interferometers, scanning-radiometers, and more recently temperature mappers. Most of them measure the mesospheric temperature in a few sample directions and/or with a limited temporal resolution, restricting their research capabilities to the investigation of larger-scale perturbations such as inertial waves, tides, or planetary waves. The Advanced Mesospheric Temperature Mapper (AMTM) is a novel infrared digital imaging system that measures selected emission lines in the mesospheric OH (3,1) band (at ∼1.5 μm) to create intensity and temperature maps of the mesosphere around 87km. The data are obtained with an unprecedented spatial (∼0.5 km) and temporal (typically 30″) resolution over a large 120° field of view, allowing detailed measurements of wave propagation and dissipation at the ∼87 km level, even in the presence of strong aurora or under full moon conditions. This paper describes the AMTM characteristics, compares measured temperatures with values obtained by a collocated Na lidar instrument, and presents several examples of temperature maps and nightly keogram representations to illustrate the excellent capabilities of this new instrument.

Hydrogen implantation in silicates: The role of solar wind in SiOH bond formation on the surfaces of airless bodies in space

AbstractHydroxyl on the lunar surface revealed by remote measurements has been thought to originate from solar wind hydrogen implantation in the regolith. The hypothesis is tested here through experimental studies of the rate and mechanisms of OH bond formation due to H+ implantation of amorphous SiO2 and olivine in ultrahigh vacuum. The samples were implanted with 2–10 keV H+, in the range of solar wind energies, and the OH absorption band at ~2.8 µm measured by transmission Fourier transform infrared spectroscopy. For 2 keV protons in SiO2, the OH band depth saturated at fluences F ~5 × 1016 H+/cm2 to a maximum 0.0032 absorption band depth, corresponding to a column density ηs = 1.1 × 1016 OH/cm2. The corresponding values for 5 keV protons in olivine are >2 × 1017/cm2, 0.0067, and 4.0 × 1016 OH/cm2. The initial conversion rate of implanted H+ into hydroxyl species was found to be ~90% and decreased exponentially with fluence. There was no evidence for molecular water formation due to proton irradiation. Translating the laboratory measurements in thin plate samples to the granular lunar regolith, it is estimated that the measurements can account for a maximum of 17% relative OH absorption in reflectance spectroscopy of mature soils, consistent with spacecraft observations in the infrared of the Moon.

Organic molecules in translucent interstellar clouds.

Absorption spectra of translucent interstellar clouds contain many known molecular bands of CN, CH+, CH, OH, OH+, NH, C2 and C3. Moreover, one can observe more than 400 unidentified absorption features, known as diffuse interstellar bands (DIBs), commonly believed to be carried by complex, carbon-bearing molecules. DIBs have been observed in extragalactic sources as well. High S/N spectra allow to determine precisely the corresponding column densities of the identified molecules, rotational temperatures which differ significantly from object to object in cases of centrosymmetric molecular species, and even the 12C/13C abundance ratio. Despite many laboratory based studies of possible DIB carriers, it has not been possible to unambiguously link these bands to specific species. An identification of DIBs would substantially contribute to our understanding of chemical processes in the diffuse interstellar medium. The presence of substructures inside DIB profiles supports the idea that DIBs are very likely features of gas phase molecules. So far only three out of more than 400 DIBs have been linked to specific molecules but none of these links was confirmed beyond doubt. A DIB identification clearly requires a close cooperation between observers and experimentalists. The review presents the state-of-the-art of the investigations of the chemistry of interstellar translucent clouds i.e. how far our observations are sufficient to allow some hints concerning the chemistry of, the most common in the Galaxy, translucent interstellar clouds, likely situated quite far from the sources of radiation (stars).

Investigating skin barrier function utilizing reflectance NIR spectroscopy.

Near Infrared Spectroscopy is seen as a potentially valuable technique for skin analysis, and has been employed by many previous studies to measure skin hydration, since it is competent of providing information regarding various functional groups including OH, CH and NH bands. The aim of this study was to investigate the capability of further utilizing this method by attempting to analyze skin barrier function as well as water content, through the evaluation of skin water uptake on two test sites, one untreated, and another treated with a high lipid moisturizer for a period of 7 days. Reflectance NIRS measurements were supported by capacitance readings obtained using the Corneometer® CM 825. Baseline recordings taken on the first day following treatment showed that more differences were observed between the treated and untreated sites in the regions belonging to, or are influenced by CH and NH groups rather than purely on the water bands. On the hand, moisture levels measured after placing a wet patch on the skin remained nearly equal for both sites but second derivative spectra showed that a clear contrast existed between absorbance heights at the water bands of the treated and untreated, suggesting that moisturizer use could have limited water uptake to a more superficial layer of the skin, whereas for the untreated site, the opposite would have been true and water was able to penetrate deeper. Overall, results here suggest that NIR spectroscopy can possibly provide valuable information not only on skin water contents but perhaps on other skin parameters such as barrier function.

CO2-induced small water solubility in olivine and implications for properties of the shallow mantle

H2O and CO2 are important components of fluids in the mantle at ∼30–150 km depth, and may affect strongly water dissolution in nominally anhydrous olivine; however, available experimental hydrogenation of olivine has been nearly exclusively carried out in coexistence with H2O (CO2-free). In this study, the effect of CO2 on water solubility in olivine has been investigated by H-annealing natural olivine under peridotite- and fluid-saturated conditions. Experiments were conducted at 1.5–5 GPa and 1100–1300 °C, with oxygen fugacity controlled by Ni–NiO and with either H2O or H2O–CO2 as buffering fluid. The olivine shows no change in composition during the experiments. The infrared spectra of the hydrated olivine are characterized by prominent OH bands from ∼3650 to 3000 cm−1 in all the runs, at both high frequency (>3450 cm−1) and low frequency (<3450 cm−1), and the H2O solubility is ∼120–370 ppm for the olivine in coexisting with H2O, and ∼65–180 ppm for the olivine in coexisting with H2O–CO2. When CO2 is present in the buffering fluid, the H2O solubility of olivine is reduced by a factor of ∼2, due to effect on the partitioning of water between minerals and coexisting fluid, and the measured H2O solubility shows independence on fluid composition (the molar ratio of CO2 to CO2 + H2O at ∼0.2–0.5) given pressure, temperature and oxygen fugacity. Olivine equilibrated in the shallow mantle is probably dominated by OH groups in the wavenumber ∼3650–3000 cm−1, and the intensity of OH bands at low frequency may be higher than or comparable to those at higher frequencies. The storage capacity of water in the shallow mantle in previous estimates may have been overestimated by a factor of at least ∼4 if the observed effect of CO2 on water solubility is correct. Our results have profound influence on understanding partial melting, electrical conductivity anomalies and metasomatism in the shallow mantle.

Near-infrared spectra of H2O under high pressure and high temperature: Implications for a transition from proton tunneling to hopping states

The nature of protons in ice VII up to 368°C and 16GPa was investigated with synchrotron near-infrared spectroscopy. The absorption band of the first OH stretching overtone mode divided into doublet peaks above 5GPa at room temperature, suggesting that proton tunneling occurs at the overtone level. As the temperature increased, the doublet peaks gradually reduced to a singlet. This result implies that thermally activated protons hop between the two potential minima along the oxygen–oxygen axis. A pressure–temperature diagram for the proton state was constructed from the changing band shape of the overtone mode.

Photoacoustic spectroscopy and thermal diffusivity measurement on hydrogenated amorphous carbon thin films deposited by plasma-enhanced chemical vapor deposition

In this work, the photoacoustic spectroscopy and the open photoacoustic cell method are employed in the thermo-optical characterization of hydrogenated amorphous carbon thin films. The samples were fabricated in a modified plasma-enhanced chemical vapor deposition system with varying deposition time from 2 to 30min. The optical absorption spectrum was determined for wavelengths of 300 to 2200nm. The optical transmission spectrum was also recorded from photoacoustic spectroscopy. The energy gap was determined from the optical absorption spectra. The thermal diffusivity was found using open photoacoustic cell technique. The thickness of the films was confirmed to be an important parameter for the optimization of the fabrication process and the improvement of thermo-optical performances of the thin films. Spectroscopic results showed lower absorption and UV transparency for the thinner film. In the infrared region the −OH band decreased with increasing film thickness. On the other hand, the thermal diffusivity measurement presented an increase of this variable with decreasing film thickness.

Response of the mesopause temperatures to solar activity over Yakutia in 1999–2013

OH(6-2) rotational temperature trends and solar cycle effects are studied. Observations were carried out at the Maimaga station (63.04°N,129.51°E) for the period August 1999 to March 2013. Measurements were conducted with an infrared spectrograph. Temperatures were determined from intensity ratios in the P branch of the OH band. The monthly average residuals of temperature after the subtraction of the mean seasonal variation were used for a search for the solar component of temperature response. The dependence of temperatures on solar activity has been investigated using the Ottawa 10.7cm flux as a proxy. A linear regression fitting on residual temperatures yields a solar cycle coefficient of 4.24±1.39K/100solar flux units (SFU). The cross-correlation analyses showed that changes of the residual temperature follow changes of solar activity with a quasi-two year delay (25months). The temperature response at the delay of 25months reaches 7K/100SFU. The possible reason of the observed delay can be an influence of quasi-biennial oscillations (QBO) of the atmosphere on the relation of temperature and solar activity. The value of the temperature trend after the subtraction of seasonal and solar components is not statistically significant.

Microwave plasma torches used for hydrogen production

A microwave plasma torch operating at 2.45 GHz and atmospheric pressure has been used as a medium and a tool for decomposition of alcohol in order to produce molecular hydrogen. Plasma in a gas mixture of argon and ethanol/methanol, with or without water, has been created using a waveguide surfatron launcher and a microwave generator delivering a power in the range 0.2-2.0 kW. Mass, Fourier Transform Infrared, and optical emission spectrometry have been applied as diagnostic tools. The decomposition yield of methanol was nearly 100 % with H2, CO, CO2, H2O, and solid carbon as the main reaction products. The influence of the fraction of Ar flow through the liquid ethanol/methanol on H2, CO, and CO2 partial pressures has been investigated, as well as the dependence of the produced H2 flow on the total flow and power. The optical emission spectrum in the range 250–700 nm has also been detected. There is a decrease of the OH(A-X) band intensity with the increase of methanol in the mixture. The emission of carbon atoms in the near UV range (240–300 nm) exhibits a significant increase as the amount of alcohol in the mixture grows. The obtained results clearly show that this microwave plasma torch at atmospheric pressure provides an efficient plasma environment for hydrogen production.

Detoxification of rats subjected to nickel chloride by a biomaterial-based carbonated orthophosphate

Recently, the therapeutic approaches of the detoxification against the metals (nickel) in the body are the use of biomaterials such as carbonated hydroxyapatite. The aim of this study is therefore to analyze the physiological and physicochemical parameters of strain white rats "Wistar" receiving nickel chloride and to study the protective associative of apatite against adverse effects of this metal, and this in comparison with control rats. Our results showed that the nickel induced in rats an oxidative stress objectified by elevated levels of thiobarbituric acid-reactive substances and conjugated dienes associated with inhibition of the activity of the antioxidant defense system such as glutathione peroxidase, superoxide dismutase and catalase in the liver, kidney, spleen and erythrocyte. Disorders balances of ferric, phosphocalcic, a renal failure and a liver toxicity were observed in rats exposed to nickel. As well as a significant increase in the rate of nickel in the bones and microcytic anemia was revealed. However, the implantation of carbonated hydroxyapatite in capsule form protects rats intoxicated by the nickel against the toxic effects of this metal by lowering the levels of markers of lipid peroxidation and improving the activities of defense enzymes. Our implantation technique is effective to correct ferric balance and phosphocalcic equilibrium, to protect liver and kidney function, to reduce the rate of bone nickel and to correct anemia. They clearly explain the beneficial and protective of our biomaterial which aims the detoxification of rats receiving nickel by substituting cationic (Ca(2+) by Ni(2+)) and anionic (OH(-) by Cl(-)) confirmed by physicochemical characterization like the IR spectroscopy and X-ray diffraction. These techniques have shown on the one hand a duplication of OH(-) bands (IR) and on the other hand the increase of the volume of the apatite cell after these substitutions (X-ray diffraction).

Optical Measurements of Atmospheric Pressure Direct Current He/H2 Microplasma in Open Air for Surface Modification

Gas discharge parameters of a direct current Ar+2%H2 non-thermal microplasma operated at atmospheric pressure were measured in this work. The microplasma was investigated in the normal and abnormal glow regimes, for current ranging from 10 to 130 mA, at ~ 160 - 250 V of applied voltage for a cathode formed with Cu+Mo+Fe foils, covered with mica at front face Cu foil. The microplasma goes through an opening hole traversing the dielectric and metal foils and emerging on open air. Both OH (A 2 Σ + , ν = 0 → X 2 Π, ν ' = 0) and N2(C 3 ∏u , ν = 0 → B 3 ∏g, ν ' = 2) bands were used to estimate the gas temperature, which ranges from 450 to 800 K. The electron number densities, ranging from 3.0 × 10 14 to 8.0 × 10 14 cm -3 , were determined by the Hβ line. Excitation temperatures were measured from three methods: from two Cu I and Mo I spectral lines ratio (Texc = 2 700 K) and from Boltzmann-plot of both Fe I and He I transitions (Texc = 3 000 K). The vibrational temperature was carried out from the second positive system N2 (C 3 ∏u → B 3 ∏g) for Δν = -2 and it was in the range 2500 - 3000 K for a current varying from 20 to 100 mA.

Atmospheric pressure plasma jet utilizing Ar and Ar/H2O mixtures and its applications to bacteria inactivation

An atmospheric pressure plasma jet generated with Ar with H2O vapor is characterized and applied to inactivation of Bacillus subtilis spores. The emission spectra obtained from Ar/H2O plasma shows a higher intensity of OH radicals compared to pure argon at a specified H2O concentration. The gas temperature is estimated by comparing the simulated spectra of the OH band with experimental spectra. The excitation electron temperature is determined from the Boltzmann's plots and Stark broadening of the hydrogen Balmer Hβ line is applied to measure the electron density. The gas temperature, excitation electron temperature, and electron density of the plasma jet decrease with the increase of water vapor concentration at a fixed input voltage. The bacteria inactivation rate increases with the increase of OH generation reaching a maximum reduction at 2.6% (v/v) water vapor. Our results also show that the OH radicals generated by the Ar/H2O plasma jet only makes a limited contribution to spore inactivation and the shape change of the spores before and after plasma irradiation is discussed.

Composition and mineralogy of dark material units on Vesta

Vesta is the asteroid with the largest albedo variation among the known rocky Solar System objects and shows a widespread occurrence of dark material (DM) and bright material (BM) units. In the first observation phases by the Dawn spacecraft, two main extensions of low albedo areas were identified on Vesta and found to be closely correlated with carbonaceous, OH-rich, material. In this work we use the hyperspectral data provided by the VIR-Dawn imaging spectrometer onboard Dawn to detect and analyze individual, well-defined, dark material units. We define DM units assuming a relative criterion, i.e. reflectance lower than the surroundings. By coupling visible and infrared images of the same area we are able to select real dark material units, discarding false detections created by shadowing effects. A detailed final catalogue of 123 dark units is presented, containing the geographical parameters and the main spectral characteristics for each unit. Independently of the geological context of the dark units, all DMs show similar spectral properties, dominated by the pyroxene absorption features, as is the average spectrum of Vesta. This finding suggests a similar composition, with the presence of darkening agents that also weaken pyroxene band depths. The majority (90%) of the DM units shows a positive correlation between low albedo and an OH band centered at 2.8μm, confirming the hypothesis that the darkening agents are carbonaceous chondrites, probably delivered by low-velocity impacts of primitive asteroids. A comparison with laboratory spectra allows us to better constrain the size and the composition of the darkening agents. These DM areas seem to be made of eucritic material. The regolith grain size seems to be nearly constant around an average value of 25μm, and is quite homogenous at least in the first hundreds of meters beneath the Vesta surface, suggesting similar processing mechanisms for both DM and BM.