Strong Vibrational Bands Research Articles

Immersion infrared reflection‐absorption spectroscopy studies on diamond‐like carbon surfaces. I. Formation of electrophilic groups on surfaces of amorphous carbon films aging in ambient air

AbstractTo study chemical functional groups on surfaces of diamond‐like carbon (DLC) films, a highly sensitive infrared reflection‐absorption spectroscopic technique, immersion infrared reflection‐absorption spectroscopy (IRRAS), is applied in the present study. The method employs (i) a conventional attenuated total reflection (ATR) accessory with a Ge crystal as an immersion medium and (ii) an aluminum underlayer beneath the 50–70 nm thick DLC film. Sensitivity, selectivity, and quantifiability of the method can be enhanced by chemical derivatization (CD), coupling chemical moieties with strong characteristic vibrational bands to specific functional groups on the DLC surface. The method is applied to amorphous sputtered carbon films (a‐C) to demonstrate that electrophilic groups, most probably epoxy groups, are formed during aging under ambient conditions.

Efficient adsorption and antimicrobial application of bio-synthesized porous CeO2 nanoparticles

The present research demonstrates the green synthesis of CeO2 nanoparticles (NPs) using the Acacia Concinna fruit extract by sol–gel route. The synthesized CeO2 NPs are applied for the adsorptive removal of Reactive Blue (RB) azo dye and antimicrobial activities. The CeO2 NPs are characterized using different techniques e.g. X-ray Diffraction Spectroscopy (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), UV–vis Spectroscopy, Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), Dynamic Light Scattering (DLS), Raman Spectroscopy, etc. The structural investigations (XRD) reveal the single-phase cubic fluorite-type structure of CeO2 with 22.7 nm of crystallite size. The spectral analysis (FTIR) shows a strong vibration band below 849 cm−1 owing to Ce-O-Ce stretching vibrations. A porous network-like morphology of the CeO2 NPs is observed by SEM, where HR-TEM micrographs reveal that the nanoparticles are roughly spherical in nature. Raman spectroscopy confirms the vibrational mode of the cubic fluorite type structure of CeO2 NPs at 462 cm−1. The maximum loading capacity of CeO2 NPS is 188.67 mg/g. The antibacterial activity of the CeO2 NPs is evaluated against S. pneumoniae and E.coli, which shows 96.17 % and 96.89 % growth inhibition at 20 mg/l.

A mid-IR laser diagnostic for HCN detection

Hydrogen cyanide (HCN) is a major source of prompt-NOx formation especially in fuel-bound nitrogen systems. To date, there is still a significant disagreement between experimental data and theoretical predictions of the rate coefficients of combustion reactions involving HCN as a prompt-NOx precursor. Accurate modeling of NOx formation would greatly benefit from a diagnostic capable of performing high-fidelity measurements of HCN formation/consumption time-histories. In this study, a laser diagnostic is developed for sensitive and selective HCN sensing by probing its most intense absorption feature in the mid-infrared (MIR). The diagnostic is based on difference-frequency generation (DFG) between a CO2 gas laser and an external-cavity quantum cascade laser in a nonlinear orientation-patterned gallium arsenide crystal which results in a DFG laser tunable over 11.56 − 15 µm. HCN measurements were carried out at the peak of the Q-branch of its strong ν2 vibrational band near 14 µm. Pressure dependence of the absorption cross-section was investigated at room temperature over the pressure range of 0.07 − 1.07 bar. Temperature-dependent absorption cross-section measurements were conducted behind reflected shock waves over the temperature range of 850 − 3000 K. The diagnostic was demonstrated in reactive experiments in a shock tube where HCN mole fraction time-histories were measured during the thermal decomposition of isoxazole (C3H3NO) and the first-order rate coefficients of C3H3NO → HCN + CH2CO reaction were determined.

Development of a Sub-ppb Resolution Methane Sensor Using a GaSb-Based DFB Diode Laser near 3270 nm for Fugitive Emission Measurement.

A challenge for mobile measurement of fugitive methane emissions is the availability of portable sensors that feature high sensitivity and fast response times, simultaneously. A methane gas sensor to measure fugitive emissions was developed using a continuous-wave, thermoelectrically cooled, GaSb-based distributed feedback diode laser emitting at a wavelength of 3.27 μm to probe methane in its strong ν3 vibrational band. Direct absorption spectra (DAS) as well as wavelength-modulated spectra (WMS) of pressure-broadened R(3) manifold lines of methane were recorded through a custom-developed open-path multipass cell with an effective optical path length of 6.8 m. A novel metrological approach was taken to characterize the sensor response in terms of the linearity of different WMS metrics, namely, the peak-to-peak amplitude of the X2f component and the peak and/or the integrated area of the background-subtracted quadrature signal (i.e., Q(2f - 2f0)) and the background-subtracted 1f-normalized quadrature signal (i.e., Q(2f/1f - 2f0/1f0)). Comparison with calibration gas concentrations spanning 1.5 to 40 ppmv indicated that the latter WMS metric showed the most linear response, while fitting DAS provides a traceable reference. In the WMS mode, a sensitivity better than 1 ppbv was achieved at a 1 s integration time. The sensitivity and response time are well-suited to measure enhancements in ambient methane levels caused by fugitive emissions.

Dynamics of photodissociation of nitric oxide from S-nitrosylated cysteine and N-acetylated cysteine derivatives in water.

Cysteine and N-acetylated cysteine derivatives are ubiquitous in biological systems; they have thiol groups that bind NO to form S-nitrosothiols (RSNOs) such as S-nitrosocysteine (CySNO), S-nitroso-N-acetylcysteine (NacSNO), and S-nitroso-N-acetylpenicillamine (NapSNO). Although they have been utilised as thermally or catalytically decomposing NO donors, their photochemical applications are yet to be fully explored owing to the lack of photodissociation dynamics. To this end, the photoexcitation dynamics of these RSNOs in water at 330 nm were investigated using femtosecond time-resolved infrared (TRIR) spectroscopy over a broad time range encompassing the entire reaction, which includes the primary reaction, secondary reactions of the reaction intermediates, and product formation. We discovered that the acetate and amide groups in these RSNOs have strong vibrational bands sensitive to the bondage of NO and the electronic state of the compound, which facilitates the identification of reaction intermediates involved in photoexcitation. The simplest thiol available with the acetate group-thioglycolic acid-was nitrosylated; it produced S-nitrosothioglycolic acid (TgSNO) and was comparatively investigated. Transient absorption bands in the TRIR spectra of the RSNOs were assigned using quantum chemical calculations. Photoexcited cysteine-related RSNOs either decompose into RS and NO within 0.3 ps after excitation at 330 nm with a primary quantum yield (Φ1) of 0.46-1 or relax into an electronically excited intermediate state lying at 42 ± 3 kcal mol-1 above the ground state, which relaxes into the ground state with a time constant of 460-520 ps. A majority (62-80%) of the RS radical geminately rebinds with NO at a time constant of 3-7 ps. The remaining RS reacts with the neighbouring RSNO, which produces additional NO and RSSR with a (nearly) diffusion-limited rate constant that doubles the amount of NO produced; further, it remarkably extends the time window for the dissociated NO to react with the target compound. The final fraction of NO produced from these RSNOs at 330 nm was 0.32-0.58, and it depends on the geminate rebinding yield and Φ1. The detailed dynamics of the photoexcited RSNO can be utilised in the quantitative application of these RSNOs in practical use and in the synthesis of more efficient photoactivated NO precursors.

Cavity Ring-Down Spectroscopy for Molecular Trace Gas Detection Using A Pulsed DFB QCL Emitting at 6.8 µm

A trace gas sensor based on pulsed cavity ring-down spectroscopy (CRDS) was developed for measurement of the ν4 fundamental vibrational band of ammonia (NH3) centered at 1468.898 cm−1. A pulsed distributed feedback quantum cascade laser (DFB-QCL) operating at 6.8 µm (1470.58 cm−1) quite well covered the absorption band of the ammonia and strong fundamental vibrational absorption bands of different molecular gases in this unexplored region. The cavity was partially evacuated down to 0.4 Atm by a turbo-molecular pump to reduce the partial interference between the NH3 spectra and water near the absorption peak of ammonia. A sensitivity of nine parts per billion was reached for a measurement time of 120 s as well as an optical path length of 226 m. The device demonstrated high spectral performance and versatility due to its wide tuning range, narrow linewidth, and comparatively high-energy mid-IR radiation in the relatively unexplored 6.8 µm region, which is very important for high-resolution spectroscopy of a variety of gases.

Glass-forming ability and the structure of glasses in the BaO-WO3-P2O5 system

The purpose of this work was to prepare and study new glasses from the system BaO-WO3–P2O5 focusing on their basic physical properties and studying their structure by Raman and 31P NMR spectroscopies in five compositional glass series. The glass transition temperature increases in all compositional series with increasing WO3 content. The 31P MAS NMR spectra of the glasses revealed depolymerization of the phosphate network. In the Raman spectra of glasses with a low WO3 content, two strong vibrational bands at 885 and 945 cm−1 were assigned to the vibration of WO and W-O− bonds in tungstate structural units. In glasses with a high WO3 content, a broad band at 820–841 cm−1, ascribed to W-O-W bonds, indicated the formation of clusters composed of WO6 units. Raman spectra also revealed partial transformation of WO6 units into WO4 units in glasses with a low P2O5 content.

A novel application of biologically synthesized nanoparticles for enhanced biohydrogen production and carbon monoxide bioconversion

This work details the synthesis and characterization of iron nanoparticles (GT-INP) from green-tea extract and its effect on biohydrogen production from CO by anaerobic biomass. Analysis of the GT-INP by UV–visible spectroscopy revealed spherical or quasi-spherical shape of the iron oxide nanoparticles. X-ray diffraction analysis confirmed the presence of iron oxide (Fe3O4) and iron(III) oxide-hydroxide (FeO(OH)) in the GT-INP. The appearance of strong vibrational bands in fourier transform infrared spectra indicated the presence of amide, C–N and hydroxyl groups due to flavonoids, alkaloids and polyphenols as capping agents in the GT-INP. Field emission scanning electron microscopy and field emission transmission electron microscopy analyses revealed that the size of GT-INP was within 50–90 nm range with a spherical shaped aggregated structure. In the presence of GT-INP at 1000 mg/l, more than 56 ± 5.32% enhancement in aqueous solubility of CO was achieved along with a maximum H2 production of 1.58 ± 0.13 mmol/l by anaerobic biomass, which is nearly 44% more than that obtained without any GT-INP addition. Continuous bioreactor study using a gas lift reactor further established the potential of GT-INP in improving biohydrogen production from CO with a maximum H2 titre of 30.7 mmol/l due to GT-INP addition in the system.

Hydrothermal synthesis of novel Mn1/3Ni1/3Co1/3MoO4 on reduced graphene oxide with a high electrochemical performance for supercapacitors

The novel chemical composition of pristine Mn1/3Ni1/3Co1/3MoO4 (MNC) and Mn1/3Ni1/3Co1/3MoO4 dispersed in various percentages of reduced graphene oxide (MNC/rGO) composites were prepared via the one-step hydrothermal method. X-ray diffraction (XRD) patterns showed pure crystalline phase CoMoO4 for the heat treated powder at 350 °C. Fourier Transform Infrared (FT-IR) spectra showed that the chemical band structure of Mn1/3Ni1/3Co1/3MoO4 corresponds to the strong vibrational bands of MoO, MoO and MoOMo bonds. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Mn, Ni, Co, Mo, C and O elements and its valance in the MNC/rGO powder. Field Emission Scanning Electron Microscope (FE-SEM) images displayed the nanorods morphology of the MNC/rGO powders. High-resolution Transmission Electron Microscopy (HR-TEM) images showed the morphology of MNC nanorods wrapped with the reduced graphene oxide of the MNC/rGO composite. The MNC/rGO composite displayed the highest specific capacitances of 1750 F g−1 at 1 A g−1 in 3 M KOH. The MNC/rGO composite demonstrated a better cycling stability with a cycling efficiency of 85.5% after 5000 cycles at 10 A g−1. The high rate performances, good reversibility and capacity retention at a range of current densities were demonstrated the structural stability of the MNC/rGO composite. The high energy density of 38.8 W h kg−1 at a constant power density of 200 W kg−1was achieved for the MNC/rGO composite.

Study of the exposure repetition over word recognition in children with different reading level

The novel chemical composition of pristine Mn1/3Ni1/3Co1/3MoO4 (MNC) and Mn1/3Ni1/3Co1/3MoO4 dispersed in various percentages of reduced graphene oxide (MNC/rGO) composites were prepared via the one-step hydrothermal method. X-ray diffraction (XRD) patterns showed pure crystalline phase CoMoO4 for the heat treated powder at 350 °C. Fourier Transform Infrared (FT-IR) spectra showed that the chemical band structure of Mn1/3Ni1/3Co1/3MoO4 corresponds to the strong vibrational bands of MoO, MoO and MoOMo bonds. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Mn, Ni, Co, Mo, C and O elements and its valance in the MNC/rGO powder. Field Emission Scanning Electron Microscope (FE-SEM) images displayed the nanorods morphology of the MNC/rGO powders. High-resolution Transmission Electron Microscopy (HR-TEM) images showed the morphology of MNC nanorods wrapped with the reduced graphene oxide of the MNC/rGO composite. The MNC/rGO composite displayed the highest specific capacitances of 1750 F g−1 at 1 A g−1 in 3 M KOH. The MNC/rGO composite demonstrated a better cycling stability with a cycling efficiency of 85.5% after 5000 cycles at 10 A g−1. The high rate performances, good reversibility and capacity retention at a range of current densities were demonstrated the structural stability of the MNC/rGO composite. The high energy density of 38.8 W h kg−1 at a constant power density of 200 W kg−1was achieved for the MNC/rGO composite.

Analysis of Zn substitution on structure, optical absorption, magnetization, and high temperature specific heat anomaly of the nano-crystalline LaFeO3

Nano-crystalline LaFe1−xZnxO3 (0 ≤ x ≤ 0.3) samples synthesized through the sol-gel auto-combustion technique have been studied. X-ray diffraction patterns reveal that all the samples have an orthorhombic crystal structure and exist in a single phase. Bond lengths and bond angles determined using Rietveld refinement change with the concentration, leading to the modification of the parent structure. The change in the structure is reflected in the thermal measurements too. The morphological studies reveal a wide-range of particle size distribution, consisting of nanometer-sized particles to macro-agglomerations. FTIR spectra show two strong active vibrational bands present at 564 cm−1 and 410 cm−1, which are related to the functional groups present in the material. The optical bandgap has been determined and is found to decrease with the increase in the concentration of Zn. Raman spectroscopy rules out the symmetry breaking or any other structural phase transition in the system. The Raman spectra reveal the strain present in the samples on increasing the concentration of Zn doping. The doping of Zn in place of Fe produces distortion mainly in the oxygen bending and stretching vibrations. Specific heat as a function of temperature has been studied and found to be sensitive to magnetic ordering. The Neel temperature decreases from 411 °C to 377 °C with the increase in the Zn concentration, which is concomitant with the Rietveld analysis. The density of our system decreases with Zn doping and leads to the increased value of specific heat. Hysteresis loops indicate that Zn doping increases the magnetic moment and decreases the coercivity.

Structural study of BaO-MoO3-P2O5 glasses by Raman and NMR spectroscopy

Glasses in the BaO-MoO3–P2O5 ternary system were prepared, their basic physical properties measured and their structure studied by Raman and 31P NMR spectroscopies. A modified glass-forming region in this system under slow cooling of the melt was determined. Four compositional series, namely (50-x/2)BaO-xMoO3-(50-x/2)P2O5 (A), 50BaO-yMoO3-(50-y)P2O5 (B), 20BaO-zMoO3-(80-z)P2O5 (C) and (70-u)BaO-uMoO3-30P2O5 (D) were chosen for a discussion on changes of the structure and properties of the studied glasses. The glass transition temperature revealed a maximum in series A at x=40mol% MoO3 and in series C at z=50mol% MoO3, whereas monotonous increase of Tg in the series B and monotonous decrease in the series D was observed. 31P MAS NMR spectra of the glasses revealed depolymerization of the phosphate network, due to the incorporation of molybdate units, and isolated PO4 groups were identified in glasses with high MoO3 content. Fitting the NMR spectra provided compositional dependences of phosphate units Qn. On the Raman spectra of glasses with low MoO3 content, a strong vibrational band at 940–944cm−1, with a shoulder at ~910cm−1, dominated the spectra, which was assigned to the vibration of terminal oxygen atoms in molybdate structural units (MO– and MO). In glasses with high MoO3 content, a broad band at ~854cm−1, ascribed to MoOMo bonds, showed on the formation of octahedral clusters composed of MoO6 units in the structure of these glasses.

Characterisation of the Chemical Composition and Structural Features of Novel Antimicrobial Nanoparticles.

Three antimicrobial nanoparticle types (AMNP0, AMNP1, and AMNP2) produced using the TesimaTM thermal plasma technology were investigated and their compositions were determined using a combination of analytical methods. Scanning electron micrographs provided the morphology of these particles with observed sizes ranging from 10 to 50 nm, whilst FTIR spectra confirmed the absence of polar bonds and organic impurities, and strong Raman active vibrational bands at ca. 1604 and 1311 cm−1 ascribed to C–C vibrational motions were observed. Carbon signals that resonated at δC 126 ppm in the solid state NMR spectra confirmed that sp2 hybridised carbons were present in high concentration in two of the nanoparticle types (AMNP1 and AMNP2). X-ray powder diffraction suggested that AMNP0 contains single phase Tungsten carbide (WC) in a high state of purity and multiple phases of WC/WC1-x were identified in both AMNP1 and AMNP2. Finally, X-ray photoelectron spectral (XPS) analyses revealed and quantified the elemental ratios in these composite formulations.

Structure–property relationships in barium borophosphate glasses modified with niobium oxide

Phosphate glasses containing a high amount of niobium oxide exhibit non-linear optical properties which make them attractive for various optical devices. This contribution is devoted to the investigation of glasses of the series (100−x)[0.5BaO–0.1B2O3–0.4P2O5]–xNb2O5 with x=0–45 and 80[0.5BaO–yB2O3–(0.5−y)P2O5]–20Nb2O5 with y=0–0.25. The basic characteristic parameters of the prepared glasses were determined. The index of refraction of these glasses increases substantially with increasing Nb2O5 content from 1.620 to 2.007 and the glass transition temperature increases within the range of 551–704°C. The glass structure was investigated by 31P, 11B and 93Nb NMR, and Raman spectroscopies. Raman spectra revealed that at low Nb2O5 content a strong vibrational band of isolated NbO6 octahedra dominates the spectra. New bands appear in the Raman spectra in the glasses with 30mol% of Nb2O5 that were assigned to vibrations of Nb–O–Nb bonds interconnecting NbO6 octahedra. 11B MAS NMR spectra reveal the dominant role of BO4 units in the glass structure. 11B MAS NMR spectra revealed that with increasing Nb2O5 content new resonances of BO4 units appear in the spectra due to the replacement of B–O–P bonds by B–O–Nb and B–O–B bonds. With an increasing Nb2O5 content, part of the BO4 units is also converted to BO3 units. 93Nb MAS NMR spectra primarily reflect changes in the length of Nb–O bonds in the NbO6 octahedra manifested in a decreasing asymmetry of the octahedra with increasing Nb2O5 content and the formation of niobate clusters. Niobo-borophosphate glasses reveal very high chemical durability as well as high glass transition temperatures due to the replacement of weaker P–O bonds with stronger Nb–O bonds.

Fabrication and Crystallization of ZnO-SLS Glass Derived Willemite Glass-Ceramics as a Potential Material for Optics Applications

Willemite glass-ceramics were successfully derived from conventional melt-quench ZnO-SLS precursor glass by an isothermal heat treatment process. The effect of heat treatment temperatures on the physical properties was investigated by Archimedes principle and linear shrinkage. The generation of willemite crystal phase and morphology with increase in heat treatment temperature was examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM) techniques. X-ray diffraction revealed that the metastableβ-Zn2SiO4and thermodynamically stable zinc orthosilicateα-Zn2SiO4phases can be observed at temperatures above 700°C. The experimental results indicated that the density and shrinkage of the glass-ceramic vary with increasing the sintering temperature. FTIR studies showed that the structure of glass-ceramic consists of SiO2and ZnO4units and exhibits the structural evolution of willemite glass-ceramics. The characteristic of strong vibrational bands can be related to theSiO44-tetrahedron corresponding to reference spectra of willemite.

HIGH-RESOLUTION IR ABSORPTION SPECTROSCOPY OF POLYCYCLIC AROMATIC HYDROCARBONS: THE REALM OF ANHARMONICITY

We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micron CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (~4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilises intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main modes that fall within 0.5% of the experimental frequencies. The implications for the Aromatic Infrared Bands, specifically the 3 micron band are discussed.

Characterization and structural investigation of lead borophosphate glasses modified by tungsten oxide

The effect of WO3 on the properties and structure of PbO–B2O3–P2O5–WO3 quaternary system was studied. Glasses containing up to 60 mol% WO3 were prepared and the variation of several physical properties was determined with respect to chemical composition in a broad compositional range. Chemical durability of WO3-containing glasses is very high and their thermal stability as well. Glass transition temperature increases with increasing WO3 content up to 566 °C. Glass structure was studied by Raman spectroscopy and 31P and 11B MAS NMR spectroscopy. NMR spectroscopy reveals the formation of B–O–W linkages and also the existence of tetrahedral BO4 units and trigonal units BO3 in the glass structure. With increasing WO3 content in the glasses, the number of starting tetrahedral B(OP)3O units decreases and B–O–P bridges are replaced gradually by B–O–W and B–O–B bridges, while the number of BO3 units increases. Raman spectra of the studied glasses possess a doublet of strong vibrational bands in the range at 800–1000 cm−1, assigned to vibrations of W–O− and WO bonds in tungstate structural units. In glasses with a higher WO3 content WO6 octahedra form tungstate clusters interconnected by W–O–W bridges as reflected in the Raman spectra. The formation of strong P–O–W and B–O–W linkages in the studied glasses explains high chemical durability of the glasses and the observed increase in the glass transition temperature.

The Influence of Nitric Acid Treatment on the Crystallographic Structure of Multiwalled Carbon Nanotubes

Commercially available Multiwalled Carbon Nanotubes (MWCNTs) were refluxed with nitric acid in order to improve the density of the acidic surface functional groups. The formation of oxygen containing functional groups may lead to surface enhancement of MWCNTs for further modifications. The crude MWCNTs were refluxed in nitric acid at 100 °C for time ranging between 3 to 24 h. The influence of treatment time on crystalline structure was investigated using X-Ray Diffraction (XRD); the results confirmed that all treated MWCNTs are crystalline. The density of the surface functional groups on treated MWCNTs was examined by Fourier Transform Infrared (FTIR). The FTIR spectrums revealed a strong vibration band at 1739, 1219, 1369 cm-1 that indicates covalently bound acidic surface functional groups existed on the treated MWCNTs. The amount of acidic groups increased with the reflux time up to 15 h treatment as measured by an acid-base Boehm titration. The vibrational spectroscopy of these functional groups also increased with the increasing reflux time.

Spectral properties of Ca-sulfates: Gypsum, bassanite, and anhydrite

This study of the spectral properties of Ca-sulfates was initiated to support remote detection of these minerals on Mars. Gypsum, bassanite, and anhydrite are the currently known forms of Ca-sulfates. They are typically found in sedimentary evaporites on Earth, but can also form via reaction of acidic fluids associated with volcanic activity. Reflectance, emission, transmittance, and Raman spectra are discussed here for various sample forms. Gypsum and bassanite spectra exhibit characteristic and distinct triplet bands near 1.4–1.5 μm, a strong band near 1.93–1.94 μm, and multiple features near 2.1–2.3 μm attributed to H2O. Anhydrite, bassanite, and gypsum all have SO4 combination and overtone features from 4.2–5 μm that are present in reflectance spectra. The mid-IR region spectra exhibit strong SO4 ν3 and ν4 vibrational bands near 1150–1200 and 600–680 cm−1 (~8.5 and 16 μm), respectively. Additional weaker features are observed near 1005–1015 cm−1 (~10 μm) for ν1 and near 470–510 cm−1 (~20 μm) for ν2. The mid-IR H2O bending vibration occurs near 1623–1630 cm−1 (~6.2 μm). The visible/near-infrared region spectra are brighter for the finer-grained samples. In reflectance and emission spectra of the mid-IR region the ν4 bands begin to invert for the finer-grained samples, and the ν1 vibration occurs as a band instead of a peak and has the strongest intensity for the finer-grained samples. The ν2 vibration is a sharp band for anhydrite and a broad peak for gypsum. The band center of the ν1 vibration follows a trend of decreasing frequency (increasing wavelength) with increasing hydration of the sample in the transmittance, Raman, and reflectance spectra. Anhydrite forms at elevated temperatures compared to gypsum, and at lower temperature, salt concentration, and pH than bassanite. The relative humidity controls whether bassanite or gypsum is stable. Thus, distinguishing among gypsum, bassanite, and anhydrite via remote sensing can provide constraints on the geochemical environment.

TNF-α and Th2 Cytokines Induce Atopic Dermatitis–Like Features on Epidermal Differentiation Proteins and Stratum Corneum Lipids in Human Skin Equivalents

Atopic dermatitis (AD) is a chronic inflammatory skin disease in which the skin barrier function is disrupted. In this inflammatory AD environment, cytokines are upregulated, but the cytokine effect on the AD skin barrier is not fully understood. We aimed to investigate the influence of Th2 (IL-4, IL-13, IL-31) and pro-inflammatory (tumor necrosis factor alpha (TNF-α)) cytokines on epidermal morphogenesis, proliferation, differentiation, and stratum corneum lipid properties. For this purpose, we used the Leiden epidermal model (LEM) in which the medium was supplemented with these cytokines. Our results show that IL-4, IL-13, IL-31, and TNF-α induce spongiosis, augment TSLP secretion by keratinocytes, and alter early and terminal differentiation-protein expression in LEMs. TNF-α alone or in combination with Th2 cytokines decreases the level of long chain free fatty acids (FFAs) and ester linked ω-hydroxy (EO) ceramides, consequently affecting the lipid organization. IL-31 increases long chain FFAs in LEMs but decreases relative abundance of EO ceramides. These findings clearly show that supplementation with TNF-α and Th2 cytokines influence epidermal morphogenesis and barrier function. As a result, these LEMs show similar characteristics as found in AD skin and can be used as an excellent tool for screening formulations and drugs for the treatment of AD.