Accounting for the species-dependence of the 3500 cm−1H2Otinfrared molar absorptivity coefficient: Implications for hydrated volcanic glasses

McIntosh, I. M.; Nichols, A. R.; Tani, Kazuo; Llewellin, Edward W.

doi:10.2138/am-2017-5952ccby

Cited by 64 publications

(39 citation statements)

References 74 publications

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“…Decades of studies show that the absorption strength of the 6 µm band correlates with the absolute H 2 O content [34][35][36] . Since the 1960s the 6 µm band has been used to measure the H 2 O content of samples in thin section in chemical and geological literature 4,35,[37][38][39] . This suggests that the 6 µm band can be used to estimate H 2 O content from the remote sensing data of the lunar surface.…”

Section: Methodsmentioning

confidence: 99%

“…Spectra were computed assuming that the Target site has the reflectance of Apollo soil 62231 (mature highlands soil) and the Reference site has the reflectance of Apollo soil 15041 (mature mare soil). The effect of water was modelled using the mean molar extinction coefficient for water at 6 µm from McIntosh et al 4 (47.8 l mol-cm), and a radiative transfer model for the band and continuum reflectance based on Hapke 41 was used to compute reflectance as a function of water abundance. Grain sizes were 60 µm per Li and Milliken 7 .…”

Section: Methodsmentioning

confidence: 99%

“…We then used the lunar emission peak intensities to estimate the abundance of water at our observed locations (see Methods). In a laboratory analysis of geologic thin sections, the abundance of H 2 O is quantified by measuring the 6 µm absorbance peak height, controlling for the thickness of the sample and converting these to abundances using the Beer-Lambert law and measured molar extinction values for water 4 . In remote sensing of planetary regolith, surfaces are in particulate form and no work has been done on deriving the absolute abundance of H 2 O from spectra of particulates near 6 µm.…”

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confidence: 99%

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Molecular water detected on the sunlit Moon by SOFIA

et al. 2020

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Widespread hydration was detected on the lunar surface through observations of a characteristic absorption feature at 3 µm by three independent spacecraft 1-3. Whether the hydration is molecular water (H 2 O) or other hydroxyl (OH) compounds is unknown and there are no established methods to distinguish the two using the 3 µm band 4. However, a fundamental vibration of molecular water produces a spectral signature at 6 µm that is not shared by other hydroxyl compounds 5. Here, we present observations of the Moon at 6 µm using the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). Observations reveal a 6 µm emission feature at high lunar latitudes due to the presence of molecular water on the lunar surface. On the basis of the strength of the 6 µm band, we estimate abundances of about 100 to 400 µg g −1 H 2 O. We find that the distribution of water over the small latitude range is a result of local geology and is probably not a global phenomenon. Lastly, we suggest that a majority of the water we detect must be stored within glasses or in voids between grains sheltered from the harsh lunar environment, allowing the water to remain on the lunar surface. Using SOFIA and the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST) instrument, we conducted observations of the lunar surface at 6 µm on 31 August 2018 in a search for molecular water. FORCAST is well suited to look for 6 µm lunar water due to its wavelength coverage from 5 to 8 µm, spectral resolution of R = 200 and high signal-to-noise ratios. The FORCAST entrance slit that defines the portion of the Moon observed is 2.4 × 191 arcsec sampled with 248 pixels. At the lunar centre of disk the slit has a spatial extent of 4.8 × 1.5 km 2 (the spatial resolution near the limb is lower due to foreshortening). During the observations, the Moon was at a phase angle of 57.5°. We observed a region at high southern latitudes near Clavius crater and a low-latitude portion of Mare Serenitatis (Extended Data Fig. 1). Details regarding observations, site selection and data reduction can be found in the Methods. Data from SOFIA reveal a strong 6 µm emission band at Clavius crater and the surrounding terrain (Fig. 1) relative to the control location near the lunar equator, which shows low hydration in some analyses (see Methods). All spectra from the Clavius region exhibit this 6 µm emission feature. The majority of these emission peaks (98%) exceed 2σ significance relative to the background noise, and about 20% exceed 4σ significance (Extended Data Fig. 2). To determine whether the spectral properties of the lunar 6 µm band are consistent with spectra of particulate water-bearing materials, we examined other planetary materials that show a 6 µm

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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Molecular water detected on the sunlit Moon by SOFIA

et al. 2020

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“…Besides, weak bands at 880 and 795 cm −1 related to −O y Si-H x and SiOH, respectively, and the O–H stretching band from SiOH and adsorbed H 2 O at 3350 cm −1 were detected [49]. Moreover, molecular water (H 2 O m ) absorbance band was observed at 1630 cm −1 [50]. These detected functional groups are in agreement with the chemical oxidation of nPSi via H 2 O 2 .…”

Section: Resultsmentioning

confidence: 99%

“…Those bands are related to the polyamino-saccharide chains of Chi, which were used to link the βCD polymer with nPSi microparticles. Regarding the spectrum of nPSi-βCD, bands corresponded to the spectrum of native βCD were observed: C–OH stretching (1021 cm −1 ) [49], C–O–C stretching (1150 cm −1 ) [13], H 2 O m (1630 cm −1 ) [50], CH2 asymmetric stretching (2930 cm -1 ) and O-H stretching from hydroxyl groups (3300 cm −1 ) [49]. nPSi-βCD barely showed an extra band than βCD at 1721 cm −1 which correspond to C=O groups generated during the polymerization achieved between βCD and citric acid [49].…”

Section: Resultsmentioning

confidence: 99%

Use of nPSi-βCD Composite Microparticles for the Controlled Release of Caffeic Acid and Pinocembrin, Two Main Polyphenolic Compounds Found in a Chilean Propolis

et al. 2019

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Propolis is widely recognized for its various therapeutic properties. These are attributed to its rich composition in polyphenols, which exhibit multiple biological properties (e.g., antioxidant, anti-inflammatory, anti-angiogenic). Despite its multiple benefits, oral administration of polyphenols results in low bioavailability at the action site. An alternative to face this problem is the use of biomaterials at nano-micro scale due to its high versatility as carriers and delivery systems of various drugs and biomolecules. The aim of this work is to determine if nPSi-βCD microparticles are a suitable material for the load and controlled release of caffeic acid (CA) and pinocembrin (Pin), two of the main components of a Chilean propolis with anti-atherogenic and anti-angiogenic activity. Polyphenols and nPSi-βCD microparticles cytocompatibility studies were carried out with human umbilical vein endothelial cells (HUVECs). Results from physicochemical characterization demonstrated nPSi-βCD microparticles successfully retained and controlled release CA and Pin. Furthermore, nPSi-βCD microparticles presented cytocompatibility with HUVECs culture at concentrations of 0.25 mg/mL. These results suggest that nPSi-βCD microparticles could safely be used as an alternate oral delivery system to improve controlled release and bioavailability of CA or Pin—and eventually other polyphenols—thus enhancing its therapeutic effect for the treatment of different diseases.

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