OH Band Research Articles

Self-diffusion of polycrystalline ice Ih under confining pressure: Hydrogen isotope analysis using 2-D Raman imaging

We have developed a high-resolution technique based on micro Raman spectroscopy to measure hydrogen isotope diffusion profiles in ice Ih. The calibration curve for quantitative analysis of deuterium in ice Ih was constructed using micro Raman spectroscopy. Diffusion experiments using diffusion couples composed of dense polycrystalline H2O and D2O ice were carried out under a gas confining pressure of 100MPa (to suppress micro-fracturing and pore formation) at temperatures from 235K to 245K and diffusion times from 0.2 to 94 hours. Two-dimensional deuterium profiles across the diffusion couples were determined by Raman imaging. The location of small spots of frost from room air could be detected from the shapes of the Raman bands of OH and OD stretching modes, which change because of the effect of the molar ratio of deuterium on the molecular coupling interaction. We emphasize the validity for screening the impurities utilizing the coupling interaction. Some recrystallization and grain boundary migration occurred in recovered diffusion couples, but analysis of two-dimensional diffusion profiles of regions not affected by grain boundary migration allowed us to measure a volume diffusivity for ice at 100MPa of (2.8±0.4)×10-3exp-57.0±15.4kJ/molRTm2/s (R is the gas constant, T is temperature). Based on ambient pressure diffusivity measurements by others, this value indicates a high (negative) activation volume for volume diffusivity of −29.5cm3/mol or more. We can also constrain the value of grain boundary diffusivity in ice at 100MPa to be <104 that of volume diffusivity.

Efficient Spectral Diffusion at the Air/Water Interface Revealed by Femtosecond Time-Resolved Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy.

Femtosecond vibrational dynamics at the air/water interface is investigated by time-resolved heterodyne-detected vibrational sum frequency generation (TR-HD-VSFG) spectroscopy and molecular dynamics (MD) simulation. The low- and high-frequency sides of the hydrogen-bonded (HB) OH stretch band at the interface are selectively excited with special attention to the bandwidth and energy of the pump pulses. Narrow bleach is observed immediately after excitation of the high-frequency side of the HB OH band at ∼3500 cm(-1), compared to the broad bleach observed with excitation of the low-frequency side at ∼3300 cm(-1). However, the time-resolved spectra observed with the two different excitations become very similar at 0.5 ps and almost indistinguishable by 1.0 ps. This reveals that efficient spectral diffusion occurs regardless of the difference of the pump frequency. The experimental observations are well-reproduced by complementary MD simulation. There is no experimental and theoretical evidence that supports extraordinary slow dynamics in the high-frequency side of the HB OH band, which was reported before.

Differentiation of Positional Isomers of Propyl Alcohols Using Filament-Induced Fluorescence**Supported by the National Natural Science Foundation of China under Grant Nos 61427816 and 61235003, the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20130061110047, and the Open Fund of the State Key Laboratory of High Field Laser Physics.

We experimentally demonstrate the recognition of positional isomers of propyl alcohol vapor through nonlinear fluorescence induced by high-intensity femtosecond laser filaments in air. By measuring characteristic fluorescence of n-propyl and isopropyl alcohol vapors produced by femtosecond filament excitation, it is found that they show identical spectra, that is, those from molecular bands of CH, C2, NH, OH and CN, while the relative intensities are different. By comparing the ratios of the CH and C2 signals, the two propyl alcohol isomers are differentiated. The different signal intensities are ascribed to different ionization potentials of the two isomer molecules, leading to different production efficiencies of fluorescing fragments.

Comparison of VLT/X-shooter OH and O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; rotational temperatures with consideration of TIMED/SABER emission and temperature profiles

Abstract. Rotational temperatures Trot derived from lines of the same OH band are an important method to study the dynamics and long-term trends in the mesopause region near 87 km. To measure realistic temperatures, the rotational level populations have to be in local thermodynamic equilibrium (LTE). However, this might not be fulfilled, especially at high emission altitudes. In order to quantify possible non-LTE contributions to the OH Trot as a function of the upper vibrational level v′, we studied a sample of 343 echelle spectra taken with the X-shooter spectrograph at the Very Large Telescope at Cerro Paranal in Chile. These data allowed us to analyse 25 OH bands in each spectrum. Moreover, we could measure lines of O2b(0-1), which peaks at about 94 to 95 km, and O2a(0-0) with an emission peak at about 90 km. The latter altitude is reached in the second half of the night after a rise of several km because of the decay of a daytime population of excited O2. Since the radiative lifetimes for the upper levels of the two O2 bands are relatively long, the derived Trot are not significantly affected by non-LTE contributions. These bands are well suited for a comparison with OH if the differences in the emission profiles are corrected. For different sample averages, we made these corrections by using OH emission, O2a(0-0) emission, and CO2-based temperature profile data from the multi-channel radiometer SABER on the TIMED satellite. The procedure relies on differences of profile-weighted SABER temperatures. For an O2a(0-0)-based reference profile at 90 km, we found a good agreement of the O2 with the SABER-related temperatures, whereas the OH temperatures, especially for the high and even v′, showed significant excesses with a maximum of more than 10 K for v′ = 8. The exact value depends on the selected lines and molecular parameters. We could also find a nocturnal trend towards higher non-LTE effects, particularly for high v′. The amplitude of these variations can be about 2 K or less, which tends to be significantly smaller than the total amount of the non-LTE contributions. The variations revealed may be important for dynamical studies based on Trot derived from OH bands with high v′.

Stark Interference of Electric and Magnetic Dipole Transitions in the A-X Band of OH.

An experimental method is demonstrated that allows determination of the ratio between the electric (E1) and magnetic (M1) transition dipole moments in the A-X band of OH, including their relative sign. Although the transition strengths differ by more than 3 orders of magnitude, the measured M1-to-E1 ratio agrees with the ratio of the abinitio calculated values to within 3%. The relative sign is found to be negative, also in agreement with theory.

Production of char from sewage sludge employing hydrothermal carbonization: Char properties, combustion behavior and thermal characteristics

A comprehensive study was conducted on the properties of chars which derived from hydrothermal carbonization (HTC) of sewage sludge (SS) while varying the operation parameters as reaction temperature 180–300°C, reaction time 30–480min. The properties of chars derived from municipal sewage sludge HTC were evaluated by Elemental analysis, FTIR spectra and thermogravimetric analysis. Elemental analysis showed that O/C and H/C atomic ratios reduce to 0.07 and 1.84, respectively at 300°C, 30min due to dehydration and decarboxylation reactions were significant during HTC process. Higher heating values of the chars have improved 1.02–1.10 times of SS (10.97MJ/kg) when reaction temperature rose to 260°C with holding time between 30min and 90min. The approximate equilibrium moisture content becomes stable at 48.5% after 60min reaction. The FTIR spectra determined that the HTC reaction improved dehydration on the OH band in SS. Higher temperature improved carbon aromaticity during HTC of SS. The thermogravimetric analysis is an effective means to analyze combustion behavior and thermal characteristics. It was also used to determine combustion kinetics of SS and chars. The result shows that the ignition temperature of chars was higher and has better performance on safe handling, storing and transportation than SS.

Non-intrusive optical diagnostics of co- and counter-swirling flames in a dual swirl pulverized coal combustion burner

Optical non-intrusive measurements are performed to a 10kWth laboratory-scale dual swirl pulverized coal combustion burner in order to elucidate the behaviors of internal recirculation zone (IRZ) and heat release region. The pulverized coal flame is operated with four different swirl combinations: co-swirling (low- and high-swirl) and counter-swirling (low- and high-swirl). The flow field is measured using particle image velocimetry (PIV). The IRZ area increases for the high-swirl conditions than that in the low-swirl conditions. With changing from co- to counter-swirl combination, the IRZ appearance changes from a heart- to an elongate-shape IRZ because double stagnation points for the co-swirling flames merges to one stagnation point for the counter-swirling flames. For the co-swirling conditions, a tube-type vortex is detected at the end of the IRZ near the double stagnation points. However, it is not present in the counter-swirling conditions. From two-color pyrometry, the overall temperature in the high-swirl flames is lower than the low-swirl flames. For the counter-swirling flames, higher temperature is observed due to the better mixing, which allows for a more intense combustion reaction of pulverized coal particles. Flame color measurements (OH and CH chemiluminescence band light emission) shows that the devolatilization of coal particles is observed at more upstream region comparing with the heat release reaction for volatile gas combustion. For the high-swirl flames, the CH∗ band intensity for heat release decreases, however its overall dimension increases. For the counter-swirling flames, the higher heat release is observed.

Raman Spectroscopic Studies of Clathrate Hydrate Formation in the Presence of Hydrophobized Particles.

In the present work, Raman spectroscopy was used to study the structure of water molecules in the vicinity of glass particles with different hydrophobicity, immersed in water and in tetrahydrofuran and cyclopentane hydrates. The glass particle surfaces were clean (hydrophilic), coated with N,N-dimethyl-N-octadecyl-3-aminopropyl trimethoxysilyl chloride (partially hydrophobic), or coated with octadecyltrichlorosilane (hydrophobic). The Raman spectra indicate that, prior to nucleation, water molecules in the vicinity of hydrophobic surfaces are more ice-like ordered than those in the bulk liquid or near either hydrophilic or partially hydrophobic surfaces. Furthermore, the degree of hydrogen-bond ordering of water observed prior to hydrate nucleation, as measured by the ratio of the inter- and intramolecular Raman OH bands, was found to have an inverse relationship with the mean induction time for hydrate formation. Following hydration formation, no significant difference in the water molecule structure was observed in the hydrate phase based on their Raman OH bands, irrespective of surface hydrophobicity. These observations made with Raman spectroscopy provide the foundations for a quantitative link between hydrate nucleation promotion and water-ordering near solid surfaces, which could enable direct comparisons with results from corresponding molecular dynamics simulations.

Green Functionalization: Comparison of Different Carbonaceous Materials

This study was carried out to study the effectiveness of green functionalization on three carbonaceous adsorbents which are CNF, MWCNT and GAC. There are two methods of green functionalization used; DI water functionalization and thermal treatment. From FTIR images of H2O-functionalization, CNF and MWCNT shows some improvement where low concentration OH band's intensity is increase. However, MWCNT is the only adsorbent that obtained additional functional group after functionalized in water bath sonicator at 55oC for 24hours which are 2 peaks of O-H at 3849.4 and 3743.2 cm-1, and alkynyl C=C stretch at 2343.1 cm-1. However, there is no significant change in functional group attached to GAC after the sonication. After thermal treatment, the FTIR images show that low concentration OH band of all three adsorbents have reduced or completely removed. While, from FESEM images, all carbonaceous adsorbents were exposed to microwave radiation (heat no 3) for 10minutes. Before the thermal treatment, there are a lot of bright spots can be seen indicating there are surface functional groups present on the surface of the adsorbent. Unfortunately, after being treated by microwave radiation, only a few functional groups attached to the surface can be seen. Adsorbent surface becomes smoother. All these changes will reduce the adsorption capacity of the dye. The diameter range is remained the same after the thermal treatment The diameter range for CNF and MWCNT prior to heat treatment is 52.05 – 105.2 and 12.33 – 22.16nm respectively. After treatment, range of diameters for CNF is 54.51 – 100.1nm, while, for MWCNT diameter is range from 13.49 – 20.37nm.

Structural and optical properties of Eu3+ activated low cost zinc soda lime silica glasses

A low cost method was employed to synthesize ZnO-SLS:xEu3+ phosphors using recyclable bottle glass as silica source. The structural and optical properties of ZnO-SLS:xEu3+ (x=0, 1, 2, 3, 4 and 5wt.%) glasses were determined using X-ray diffraction (XRD), Fourier transform infrared reflectance (FTIR), UV-visible (Uv-Vis) and photoluminescence (PL) spectroscopy. Structural investigation using XRD measurement had broadened the halo peak with the doping of dopants. FTIR spectra showed the glass system consists of –OH and SiO4 bands. Meanwhile, the optical measurement using UV-Vis absorption has been induced a blue shift of the electronic absorption edge. The emission peak intensity of ZnO-SLS:xEu3+ phosphors was enhanced with the progression of doping concentration and thus, revealed their potential as red emitting phosphors under 400nm excitation.

The H2O/D2O isotope effect in crystalline lanthanide sulfates at photo-, radio-, and triboluminescence

We comparatively studied the H2O/D2O isotope effect of lanthanide sulfate crystallohydrates on photo-, radio-, and triboluminescence and lifetimes of the excited Ln3+ ions. Replacing H2O by D2O leads to an increase in the luminescence intensity whereas this process does not affect the maxima positions in photo-, radio-, and triboluminescence spectra. This isotope effect agrees with the known concepts of changes in luminescence quantum yields of the Ln3+ ions being the main emitters. The bands of OH and OD radicals arise in triboluminescence spectra of lanthanide sulfate crystallohydrates (with H2O or D2O) registered in argon atmosphere in UV region. This supports the proposition that water destruction occurs at the degradation of the crystallohydrates.

Effect of oxygen fugacity on OH dissolution in olivine under peridotite-saturated conditions: An experimental study at 1.5–7 GPa and 1100–1300 °C

The dissolution of OH in olivine by experimental studies at simulated conditions has attracted increasing interest over the past three decades, and the influence of pressure, temperature and composition has been relatively well constrained. Oxygen fugacity is highly heterogeneous in the upper mantle, on both temporal and spatial scales, and is an important parameter in characterizing many chemical and physical processes in the mantle. However, less attention has been devoted to the effect of oxygen fugacity on OH dissolution in olivine, and the only few available reports on this topic have led to significant inconsistency and debate. In this study, the correlation between oxygen fugacity and OH solubility in Fe-bearing olivine has been systematically investigated by conducting experiments at 1.5–7GPa and 1100–1300°C and under peridotite- and fluid-saturated conditions, with natural gem-quality olivine single crystals and fresh peridotite xenoliths as starting materials and with oxygen fugacity controlled by the Fe–FeO, Ni–NiO and Fe2O3–Fe3O4 oxygen buffer pairs. The water concentrations were determined by polarized analyses using a Fourier-transform infrared spectroscopy. The results show that, at all the experimental conditions, the OH bands at both high frequency (∼3650–3450cm−1) and low frequency (∼3450–3100cm−1) are prominent. The intensity of OH bands at ∼3355 and 3325cm−1 increases positively with oxygen fugacity, suggesting a dominant role of Fe3+ in their incorporation. Under otherwise identical conditions, the water content is gradually enhanced with increasing pressure, temperature or oxygen fugacity. The effect of oxygen fugacity on the enhancement of OH solubility appears not sensitive to temperature (1100–1300°C) at a given pressure, but becomes progressively stronger with increasing pressure from 1.5 to 7GPa given the temperature. Relative to oxygen fugacity buffers, the OH solubility is on average increased by ∼50% between Fe–FeO and Ni–NiO, independent of pressure and temperature. The enhanced OH solubility at relatively oxidizing conditions could be explained by the role of oxygen fugacity in changing the point defects of olivine. Experimental work concerning the storage capacity of water in olivine and in the upper mantle must consider the effect of oxygen fugacity. The OH solubility of olivine in the reducing deep upper mantle obtained from experiments under oxidizing conditions would be overestimated. The initial OH information of many natural olivines may have been modified by some recent secondary events, e.g., during their shallow residence and/or transport to the surface, and in principle, olivine equilibrated in the upper mantle may be D-depleted relative to its coexisting minerals. Some preliminary constraints on the water storage capacity in the upper mantle of the Earth and the Mars are also provided.

OH solubility in olivine in the peridotite–COH system under reducing conditions and implications for water storage and hydrous melting in the reducing upper mantle

Experimental studies of OH solubility in peridotite minerals are of crucial importance for understanding some key geochemical, geophysical and geodynamical properties of the upper mantle. In reducing depths of the upper mantle, C–O–H fluids are dominated by CH4 and H2O. However, available experimental H-annealing of olivine concerning water storage capacity in the reducing upper mantle has been exclusively carried out by equilibrating olivine with H2O only. In this study, OH solubility in olivine has been investigated by annealing natural olivine crystals under peridotite-bearing and CH4–H2O-present conditions with piston cylinder and multi-anvil apparatus. Experiments were performed at 1–7 GPa and 1100–1350 °C and with oxygen fugacity controlled by Fe–FeO buffer, and OH solubilities were measured from polarized infrared spectra. The olivines show no change in chemical composition during the experiments. The infrared spectra of all the annealed olivines show OH bands in the range 3650–3000 cm−1, at both high (>3450 cm−1) and low (<3450 cm−1) frequency, and the bands at ∼3400–3300 cm−1 are greatly enhanced above ∼3 GPa and 1300 °C. The determined H2O solubility is ∼90–385 ppm for the olivine coexisting with H2O (1–7 GPa and 1100 °C), and is ∼40–380 ppm for the olivine coexisting with CH4–H2O (1–7 GPa and 1100–1350 °C). When CH4 is present in the equilibrium fluid, the H2O solubility is reduced by a factor of ∼2.3 under otherwise identical conditions, indicating a strong effect of CH4 on the partitioning of water between olivine and coexisting fluid. The storage capacity of water in the reducing upper mantle is, modeled with the measured solubility of olivine and available partition coefficients of water between coexisting minerals, up to ∼2 orders of magnitude lower than some previous estimates. Considering the temperature along the geotherm in the reducing oceanic upper mantle, the required H2O concentration to trigger hydrous melting is 250 and 535 ppm at ∼100 and 210 km depth, respectively, and is even larger at greater depths. These values exceed the typical H2O abundance (∼100±50 ppm) in the upper mantle, suggesting that pervasive hydrous melting at reducing depths of the oceanic upper mantle is not likely. Similar arguments may also be casted for the reducing deep upper mantle in the continental regions.

Coordinated airglow observations between IMAP/VISI and a ground‐based all‐sky imager on concentric gravity wave in the mesopause

AbstractWe present a study of concentric gravity waves (CGWs) event from the coordinated observation between Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere mapping (IMAP)/Visible and near‐Infrared Spectral Imager (VISI), all‐sky camera at Rikubetsu, Multi‐functional Transport Satellite (MTSAT), Tropical Rainfall Measuring Mission, and MF radar at Wakkanai combined with Modern‐Era Retrospective Analysis for Research and Application data. IMAP/VISI is the first space‐based imager that capable of imaging the airglow in the mesosphere and lower thermosphere region in the nadir‐looking direction. Therefore, it has a unique ability to observe a great extend of CGWs propagation. Arc‐like shaped, part of CGWs pattern was observed around the mesopause (~95 km) in the O2 762 nm airglow emission obtained by IMAP/VISI at 1204 UT on 18 October 2012. Similar patterns were also observed by the all‐sky imager at Rikubetsu (43.5°N, 143.8°E) in OI 557.7 nm and OH band airglow emissions from ~1100 to 1200 UT. Horizontal wavelengths of the observed small‐scale gravity waves are ~50 km (OH band and OI 557.7 nm) and ~67 km (O2 762 nm). The source is suggested to be a deep convective activity over Honshu Island which likely was an enhanced convective activity related to a typhoon in the south of Japan. The data showed that the CGWs could propagate up to ~1400–1500 km horizontally from the source to the mesopause but not farther away. Using atmospheric temperature profiles obtained by Thermospheric Ionosphere Mesosphere Energetics Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry, we conclude that this long‐distance propagation of the waves could be caused by thermal duct in the middle atmosphere. The arc‐like shaped instead of full circle pattern points out that the wind filtering effect is significant for the particular direction of wave propagation.

Comparison of rotational temperature derived from ground‐based OH airglow observations with TIMED/SABER to evaluate the Einstein coefficients

AbstractGround‐based observations of the OH(9–4, 8–3, 6–2, 5–1, and 3–0) band airglows over Xinglong, China (40°24′N, 117°35′E) from December 2011 to 2014 are used to calculate rotational temperatures. The temperatures are calculated using five commonly used Einstein coefficient data sets. The kinetic temperature from Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics/Sounding the Atmosphere by Broadband Emission of Radiation (SABER) is completely independent of the OH rotational temperature. SABER temperatures are weighted vertically by weighting functions calculated for each emitting vibrational state from two SABER OH volume emission rate profiles. By comparing the ground‐based OH rotational temperature with SABER's, five Einstein coefficient data sets are evaluated. The results show that temporal variations of the rotational temperatures are well correlated with SABER's; the linear correlation coefficients are higher than 0.72, but the slopes of the fit between the SABER and rotational temperatures are not equal to 1. The rotational temperatures calculated using each set of Einstein coefficients produce a different bias with respect to SABER; these are evaluated over each of the vibrational levels to assess the best match. It is concluded that rotational temperatures determined using any of the available Einstein coefficient data sets have systematic errors. However, of the five sets of coefficients, the rotational temperature derived with Langhoff et al.'s (1986) set is most consistent with SABER. In order to get a set of optimal Einstein coefficients for rotational temperature derivation, we derive their ratios from ground‐based OH spectra and SABER temperatures statistically using 3 years of data. The use of a standard set of Einstein coefficients will be beneficial for comparing rotational temperatures observed at different sites.

INFRARED SPECTRAL PROPERTIES OF M GIANTS

We observed a sample of 20 M giants with the Infrared Spectrograph on the Spitzer Space Telescope. Most show absorption structure at 6.6-6.8 um which we identify as water vapor, and in some cases, the absorption extends from 6.4 um into the SiO band at 7.5 um. Variable stars show stronger H2O absorption. While the strength of the SiO fundamental at 8 um increases monotonically from spectral class K0 to K5, the dependence on spectral class weakens in the M giants. As with previously studied samples, the M giants show considerable scatter in SiO band strength within a given spectral class. All of the stars in our sample also show OH band absorption, most noticeably in the 14-17 um region. The OH bands behave much like the SiO bands, increasing in strength in the K giants but showing weaker dependence on spectral class in the M giants, and with considerable scatter. An examination of the photometric properties reveals that the V-K color may be a better indicator of molecular band strength than the spectral class. The transformation from Tycho colors to Johnson B-V color is double-valued, and neither B-V nor BT-VT color increases monotonically with spectral class in the M giants like they do in the K giants.

Reflectance spectroscopy of low atomic weight and Na-rich minerals: Borates, hydroxides, nitrates, nitrites, and peroxides

We have measured reflectance spectra (0.35–20μm) of a suite of minerals and synthetic compounds that contain low-Z (⩽Na) elements as the major cation and/or the major anion in oxides/oxyhydroxides, and are relevant to planetary geology and astrobiology. The suite comprises Na-borates, Na-, K-, Ca-hydroxides, nitrates, nitrites, and peroxides. Na-borate spectra exhibit B–O fundamental vibrations between 7 and 14μm, and overtones/combinations of these bands in the 1.55, 1.75, 2.15, and 2.25μm regions. Na-, K-, and Ca-hydroxide reflectance spectra are characterized by OH and metal–OH fundamental vibrations near 3, 8, and 18μm, and a number of overtone and combination absorption bands at shorter wavelengths, and a characteristic metal–OH band near 2.35μm. The nitrate and nitrite spectra exhibit fundamental N–O vibrations in the 7–14μm region and numerous combinations and overtones that are still detectable to as low as ∼1.8μm. Na-peroxide is largely spectrally featureless below 24μm, making its detection problematic, while H-peroxide has many OH-related absorption features below 2.5μm that differ in position from those of H2O ice and liquid. The results of this study indicate that the borates, hydroxides, nitrates, nitrite, and hydrogen peroxide can all be uniquely identified using characteristic absorption features that are present below 2.5μm. However, some of these features are weak, and their detectability will depend on the types and abundances of any accessory phases that may be present.

Interaction of carboxylic acids with rutile TiO2(110): IR-investigations of terephthalic and benzoic acid adsorbed on a single crystal substrate

The adsorption of two carboxylic acids, benzoic acid (BA) and terephthalic acid (TPA), on a single crystal rutile TiO2(110) substrate was studied using infrared reflection–absorption spectroscopy (IRRAS) in conjunction with DFT calculations. On the basis of the high-quality IR data (in particular for the OH bands), various adsorbate species with different geometries could be identified. The adsorption of both, BA and TPA, on TiO2(110) leads to deprotonation of carboxylic acids and protonation of substrate O-atoms. At low coverage, the deprotonated BA molecule adsorbs on TiO2(110) in an upright, bidentate configuration, while the TPA molecule adopts a flat-lying geometry with both carboxylates bound to the surface in a monodentate geometry. At higher coverages, a transition from flat-lying to upright-oriented TPA molecules occurs. At saturation coverage, both BA and TPA molecules undergo dimerization indicating the presence of pronounced attractive intermolecular interactions. We propose that the BA dimers are stabilized by the interaction between adjacent phenyl rings, while the TPA dimerization is attributed to the formation of double hydrogen bonds between adjacent apical carboxylic groups.

Poly(vinyl alcohol) Nanocomposites Reinforced with Bamboo Charcoal Nanoparticles: Mineralization Behavior and Characterization.

Polyvinyl alcohol (PVA) demonstrates chemical stability and biocompatibility and is widely used in biomedical applications. The porous bamboo charcoal has excellent toxin absorptivity and has been used in blood purification. In this study, bamboo charcoal nanoparticles (BCNPs) were acquired with nano-grinding technology. The PVA and PVA/BCNP nanocomposite membranes were prepared and characterized by the tensile test, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). Results showed that the tensile strength and elongation of the swollen PVA membranes containing 1% BCNPs (PB1) were significantly greater than those of PVA and other PVA/BCNP composite membranes. In addition, the major absorption band of OH stretching in the IR spectra shifted from 3262 cm−1 for PVA membrane containing 1% BCNP to 3244 cm−1 for PVA membrane containing 20% BCNP. This blue shift might be attributed to the interaction between the PVA molecules and BCNPs. Moreover, the intensity of the XRD peaks in PVA was decreased with the increased BCNP content. The bioactivity of the nanocomposites was evaluated by immersion in the simulated body fluid (SBF) for seven days. The mineral deposition on PB5 was significantly more than that on the other samples. The mineral was identified as hydroxyapatite (HA) by XRD. These data suggest that the bioactivity of the composite hydrogel membranes was associated with the surface distribution of hydrophilic/hydrophobic components. The PVA/BCNP composite hydrogels may have potential applications in alveolar bone regeneration.

Wet Etchant Diffusion through Photoresist during Gate Oxide Patterning

Gate oxide patterning during integrated circuits manufacturing is defined by a photolithography – etch sequence. Wet etchants are still preferred to plasma to keep smooth transistors channel. With the transistor nodes evolution, not only the lateral resist dimension has shrunk but also their thickness to get accurate optical performances: from microns thick down to few hundreds of nanometers. Therefore the resist protection of the underlying material is at risk due to wet etchant infiltration through the resist (figure 1) [1], hence the importance of controlling this phenomenon. Hereby, a wide screening is made among the wet etch conditions, polymer nature and plasma use on the resist before wet. Liquid diffusion through resist is in-situ monitored by ATR-FTIR (Attenuated Total Reflection Fourier Transform Infrared) spectroscopy coupled with a liquid cell in direct contact with wafer samples (Figure 1) [2][3]. First study deals with deionized water penetration through a commercial 248 nm Deep UV photoresist, 1,8 micron thick. The IR absorption spectrum of interest for water lays between 2900 and 3700 cm-1 (figure 2). Hence the δ(OH) absorbance band is followed along the contact duration between resist and water and its area is integrated. The absorbance ratio between value at time t and infinite time is drawn versus time (figure 3). The water diffusion follows a Carter and Kibler model [4] divided in three steps: a quick increase in OH band absorption in the first minutes, followed by a slower evolution and finally an even quicker absorption. The first phase corresponds to the free water penetration, the second one to the bound water penetration and finally irreversible polymer deterioration (swelling and hydrolysis). Although wet etch alone is mostly used to preserve smooth surfaces, etch combination can be found with a plasma followed by a wet etch. The plasma can significantly impact the wet etchant penetration through the resist. Indeed, the plasma decreases the resist thickness, changes the polymer surface and structure. The tested CF4 plasma increases both the water penetration speed and sorption in the resist (Figure 4). Furthermore four different 248 nm DUV resist are compared (figure 5). Their diffusion follows previously described model. However the first phase ends at different timing. Beyond this duration, the liquid has reached the underneath material and resist protection isn’t effective anymore. Conclusion Wet etchant penetration through photoresist has been monitored thanks to ATR FTIR, with numerous variations of the studied system. A three-step diffusion model is shown. It enables the determination of key intrinsic parameters of the resist. Eventually a methodology is given to compare the resist protection effectiveness and maximum allowed wet etch duration.