OH Vibrations Research Articles

Atmospheric Pressure DBD Low-Temperature Plasma Reactor for the Treatment of Sugarcane Bagasse

This paper embodies the results of experimental studies of a dielectric barrier discharge low-temperature nonequilibrium plasma reactor that runs in air and nitrogen at atmospheric-pressure conceived for surface treatment applications. A homemade reactor, of typical plane-to-plane geometry with the dielectric covering the upper electrode which is stressed by a high voltage (40 kV, 3–20 kHz) is used. Electrical signals (current and voltage), optical emission spectroscopy records, and total light emission measured by photomultiplier have been analyzed and used to distinguish different plasma regimes which are studied for the treatment of a lignocellulosic material (sugarcane bagasse). In the filamentary discharge regime, the gas temperature of few tens of degree Celsius above the ambient one was determined, the electronic temperature of some electronvolts and electron density in the range of 1012–1013 cm−3 were estimated. Plasma treated pellets of sugarcane bagasse were analyzed by diffuse reflectance infrared Fourier transform spectrometry and the relative results obtained under filamentary discharge regime have shown significant degradation of the lignin macromolecule. It has been shown important modifications on the lignocellulosic material, namely, the plasma attacks drastically the lignin bonds. Strong modification of lignin was observed near wavenumber of 3400 cm−1, due to stretching vibrations of OH, and for the band 1114 cm−1 which is related to C=C and C=O stretching. Severe decrease of the band intensity 1596 cm−1, which due to C=C stretching and C=O, is also a result of the treatments done in this paper.

Synthesis Of 4-Alil-6- (Hydroxymethyl) -2-Methody Phenol Compounds from Eugenol Through Mannich Reaction Followed Methylation with Methyl Iodide and Subtitution Using NaOH

Eugenol derivative compound 4-allyl-6-hydroxymethyl-2-methoxy phenol was synthesized through Mannich reaction, methylation, dan nucleophilic substitution. Mannich reaction was carried out by reacting eugenol, formaldehyde 37%, and dimethylamine 40 % in reflux condition with n-heptane solvent at temperature 98o-100oC for 10 hours produced 4-allyl-6-(dimethylamino)methyl-2-methoxy phenol with yield of 83 %. The formation of dimethylaminomethyl group supported by C-N stretching vibration at 1246,16 cm-1 and ion molecule peak at 221 in GC-MS analysis. Methylation of 4-allyl-6-(dimethylamino)methyl-2-methoxy phenol was carried out with methyl iodide in ethanol solvent produced 6-((N-iodo-N-methyl-N-methyl-N-methylamino) methyl)-4-allyl-2-methoxy phenol in solid form, which then purified by recrystallization with 78,15 % yield. 4-allyl-6-(hydroxymethyl)-2-methoxy phenol was synthesized by nucleophilic substitution reaction of 6-((N-iodo-N-methyl-N-methyl-N-methylamino)methyl)-4-allyl-2-methoxy phenol with sodium hydroxide in reflux condition then purified by coloum chromatography gave liquid compound with yield of 65,05%. The formation of hydroxymethyl group supported by OH vibration at 3433,9 cm-1 and ion molecule peak at 194 in GC-MS analysis show the relative molecular mass of synthesized product.

Siloxene: A Potential Layered Silicon Intercalation Anode for Na, Li and K Ion Batteries

Silicon is one of the most promising anodes for lithium-ion (LIB) and sodium-ion (NIB) batteries due to its high theoretical capacity, 3590 mAh/g for Li15Si4 [1] and 954 mAh/g for NaSi.[2] Nevertheless, its practical application is hindered by a series of obstacles. For lithium (Li), the access to such high lithiated phases causes extreme volume expansion (310%), resulting in a rapid capacity fade. For sodium (Na), the slow kinetics and the ionic radius restrict the sodiation of c-Si. In an attempt to address these problems, recent attention has been given to the two-dimensional 2D silicon structures, comprising calcium silicide (CaSi2), polysilane (Si6H6) and siloxene (Si6O3H6), due to their potential ability to buffer the electrode volume changes during cycling and their facile synthesis through soft-chemical methods. In this work, the lamellar siloxene was obtained via topotactic deintercalation of Ca from CaSi2 and its electrochemical performance was evaluated with Li, Na and K. The results show the versatility of siloxene as anode for LIB, NIB and KIB, with delivered reversible capacities of 2300, 311 and 203 mAh/g for Li, Na and K, respectively. The material exhibits a noticeable structural stability after several cycles, deriving in a good capacity retention and coulombic efficiency. The electrochemical mechanism taking place upon cycling is highlighted on the basis of ex situ Raman characterization combined with IR spectroscopy, SEM and TEM. The results are unsuccessful in explaining all the observed phenomena by means of a merely silicon alloying mechanism, therefore a possible alkali intercalation alternative has been proposed. Preliminary evidence of this approach can be found in the siloxene structural integrity after several cycles, the presence of Na in the discharged compound as observed by EDX, the absence of any of the diffraction peaks from NaSi/Li15Si4 (both crystalline and proper from the alloying mechanism) by XRD, and the lack of their respective Raman vibration bands [3- 4], at the end of the discharge. Indeed, by Raman spectroscopy it was possible to observe a reversible shift of the main Si-plane vibration band for the discharged and charged siloxene, accompanied by a loss of the –OH and Si-H vibrations observed in the pristine siloxene. Undoubtedly, these two last ones are likely related to a change in the bond nature of the Si-planes with the substituent group producing a different interlayer separation, probably the electrochemical cycling induces an exchange between –OH and –H with Li/Na. In fact, the intercalation of Na/Li into a layered Si-based materials has been theoretically predicted for a single layer of siloxene (silicene), with no experimental record. The calculations foresee a high coverage of the silicene with alkali ions like Na, Li and K due to the nature of their interactions. The full sodiated/lithiated state of silicene corresponds to X1Si1 (X=Li/Na), the predicted binding energies and diffusion barriers indicate that their intercalation is achievable without the kinetic limitations (higher diffusion coefficient for silicene), structure degradation and volume expansion of bulk Si. [5–9] This feasibility for alkali intercalation with such high structural stability introduces siloxene as a potential anode for LIB, NIB and KIB batteries. Nevertheless, a better understanding of its electrochemical mechanism is necessary to develop its maximum performance. To the best of our knowledge, it is the first time that a lamellar Silicon based material shows such high stable capacity without volume expansion, representing a real breakthrough for the batteries field and particularly for NIB.

1-Hexanol conformers in a nitrogen matrix: FTIR study and high-level ab initio calculations

FTIR spectra of 1-hexanol trapped in a nitrogen matrix were registered in the temperature range from 10 to 40 K. The experiment has shown that only non‑hydrogen-bonded alcohol molecules were present in the sample at 10 K. Conformational analysis using high-level ROCBS-QB3 ab-initio calculations has shown that only 111 of 122 1-hexanol conformers can exist. The most stable conformer was determined. Anharmonic quantum-chemistry calculations and further special scheme of principal component analysis resulted in at least 12 unneglectable conformers in the sample, 6 of which form about 85% of FTIR spectra in the region of the stretching OH vibrations. Sample heating leads to a significant redistribution between conformers. Relative weights of different conformers at all investigated temperatures did not match Boltzmann probability distribution. Moreover, 1-hexanol structure was formed not by all the most stable structures, but only by some of them.

Study of the structural order of native starch granules using combined FTIR and XRD analysis

The structural order of native starch granules with different crystalline patterns was analyzed by combined X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and the results were compared to that of X-ray diffraction (XRD). The FTIR spectra of 13 starch samples were evaluated by principal component analysis (PCA). The main differences among the polymorphs were observed in the intensity of two regions: the OH vibration region, 3650–3000 cm−1, and the region of major adsorption bands, 1200–800 cm−1. The variation in these regions showed that two different groups can be distinguished, one for B-type starches and one for A- and C-type starches. A-type starches exhibited a well-resolved band at 1022 cm−1, suggesting that A-type starch granules have a greater amount of ordered short-range double helices than B-type starches. The intensity and shape of the OH band were different for the three starches and were associated with different local molecular environments of the two water populations of the starch granule. The PCA analysis for X-ray diffraction patterns showed a clear segregation between A- and B-type starches, defined by three typical diffraction peaks at 2θ = 15.0°, 18.1° and 23.1° for A-type starches. There was no correlation in the crystallinity degree obtained by the FTIR and XRD methods.

Investigation on synthesis and characterization of Fe-doped Al2O3 nanocrystals by new sol–gel precursors

Pure aluminum oxide (Al2O3) and Fe-doped Al2O3 nanoparticles (NPs) with impurities of 1%, 2%, and 4% were synthesized by the sol-gel method with AlCl3 and FeSO4 new precursors in the presence of CTAB stabilizer and NaBH4 reduction agent. To study the structural, optical, and magnetic properties of the samples, they were exposed to heat treatment at 1000 °C. The structural results of XRD analysis showed that the sample had a crystalline γ-alumina phase in pure state, and with the increase of Fe dopant up to 1% and 2%, the δ-alumina phase appears in the sample. The novelty of this work is that, with an increase in dopant to 4%, the crystalline structure of the sample changes into α-alumina at constant temperature. The results of the FESEM analysis showed that the sample uniformity and porosity increases with increasing Fe impurities. EDX analysis also showed that Al content increased with an increase in Fe dopant from 63.39 wt% to 67.21 wt%, indicating a change in the crystalline phase of the sample to α-alumina structure. The results of the TEM analysis showed that the size of the NPs decreased through increasing the 4% Fe dopant. The Al–OH vibrations were characterized by FTIR analysis in the vibrational frequencies of 1332 and 1419 cm−1. It was also found in this analysis that the absorption in the frequencies of 580 cm−1 and 802 cm−1 increased, which is related to the sites of octahedral AlO6 and tetrahedral AlO4, suggesting the phase change into the state α-alumina in the 4% dopant. In the UV-DRS analysis, it was found that the band gap decreased with an increase in the Fe dopant from 4.20 eV for a pure Al2O3 to 3.50 eV for a sample with a 4% dopant which is less than the band gap energy of 6–8 eV obtained by many researchers. Finally, the VSM analysis showed that with increasing dopant, the magnetic behavior of the sample changes to a ferromagnetic state. Saturation magnetization and coercivity are also obtained at 0.145 emu g−1 and 127 G for the 4% dopant, respectively. The results of this study showed that in the formation of Fe–Al2O3 NPs, the structural change into the α-alumina phase is carried out with a 4% increase in the Fe dopant at 1000 °C.

Terrestrial humic-like fluorescence peak of chromophoric dissolved organic matter as a new potential indicator tracing the antibiotics in typical polluted watershed

Natural surface waters are threatened globally by antibiotics pollution. In this study, we analyzed antibiotics and CDOM (Chromophoric dissolved organic matter) fluorescence in different water bodies using HPLC method and Excitation Emission Matrix- Parallel factor analysis, respectively. A combination of field studies in the Yinma River Watershed were conducted in rivers, reservoirs and urban rivers, and 65 CDOM and antibiotic samples were taken in April, May, July, and August 2016. EEM-PARAFAC analysis identified two components; a humic-like (C1) component and a tryptophan-like (C2) component. The redundancy analysis (RDA) demonstrated that CDOM could explain 38.2% (two axes) of the five antibiotics in reservoirs (N = 31), and 26.0% (two axes) of those in rivers and urban water (N = 30). Furthermore, the Pearson correlation coefficient between Sulfamethoxazole and C1 in reservoir water was 0.91 (t-test, 2-tailed, p < 0.01), and that between Sulfamethoxazole and C2 was 0.68 (t-test, 2-tailed, p < 0.01). This indicated that the humic-like component of CDOM PARAFAC fluorescence could detect Sulfamethoxazole contamination levels in the homogenized reservoir waters. Our results identified Sulfamethoxazole and Quinolones (Norfloxacin, 16.5 ng L−1; Enrofloxacin, 0.3 ng L−1; Ciprofloxacin, 30.9 ng L−1) at mean concentrations of 369.5 ng L−1 and 15.9 ng L−1, respectively, which were the higher levels in natural surface waters. The FTIR spectroscopy of the mixture of humic acid and sulfamethoxazole showed that the absorbance at 3415 cm−1 linked to OH stretching of OH groups and at 1386 cm−1 because of OH bending and vibration of COOH groups became weaker, indicating that COOH groups of humic acid can adsorb and react with –NH2 of sulfamethoxazole. The CDOM PARAFAC components can be adapted for online or in situ fluorescence measurements as an early warning of Sulfamethoxazole distribution and contamination in similar aquatic environments.

Removal of hydroxyl routes enhancing 2.85 μm mid-infrared luminescence in oxyfluorotellurite glass with high ZnF2 content

The near ~3 μm mid-infrared laser demonstrates real and potential applications in many military and civilian areas, but the lack of host materials with nice optical quality and the overlapped vibrations of OH– hamper the emission intensity. To eliminate the OH– absorption, ZnF2 was adopted in Yb3+/Ho3+ codoped binary TeO2-PbF2 glass to partially till totally replace PbF2. The high ZnF2 concentration would raise the glass transition temperature and enhance the thermal stability of matrix, especially enhance the intensity of 2.85 μm mid-infrared luminescence obviously. TeO2-ZnF2 glass with 45.5% ZnF2 original content has high ratio of the strength parameter Ω4/Ω6 (=2.90) and possesses higher spontaneous transition probability (45.25 S−1) along with the larger calculated emission cross section (0.96 × 10−20 cm2) corresponding Ho3+: 5I6 → 5I7 transition. Fourier transmittance of infrared spectra revealed ZnF2 could reduce the OH– concentration in glass substantially, which were favor of 2.85 μm mid-infrared emission. Our results indicated that the use of ZnF2 to effectively remove the hydroxyl groups is an efficacious way to develop near ~3 μm mid-infrared optical glass with high efficient luminescence and thermochemical reliability.

Role of Ti Content on the Occurrence of the 3309-cm–1 Peak in FTIR Absorption Spectra of Ruby Samples

The study is based on the determination of trace elements in ruby samples, Ti in particular, using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS). The samples were then divided into three groups: high (≥ 200 ppma), moderate (100–200 ppma), and low (≤ 50 ppma) Ti content. In addition, X-ray absorption spectroscopy (XAS) was employed to confirm that the Ti oxidation state was Ti4+. The heat experiment conditions were set at 800, 1200, and 1650°C to investigate the transformation of the –OH vibration in the FTIR spectra of ruby samples. The FTIR spectra showed that samples containing a low Ti concentration did not show the 3309-cm–1 absorption peak either before or after heating at any of the designed temperatures. An obvious 3309-cm–1 peak appeared only in samples with a moderate to high Ti content after heating at ≥ 1200°C. The results also suggest that, in addition of Ti4+, the occurrence of the 3309-cm–1 peak in the FTIR spectra is strongly affected by the charge compensation of –OH in Al sites, i.e., the structural –OH; thus, the structural –Ti–OH stretching in the ruby samples. Hence, for gemological identification, the 3309-cm–1 peak can be applied to indicate whether a ruby has undergone heat treatment if those samples contain enough Ti ions in their structure, i.e., Ti ≥ 100 ppma. This condition is usually found in ruby samples from major deposits such as Mong Hsu and Mogok, Myanmar; Luc Yen, Vietnam; and Montopuez, Mozambique.

Vibrational spectra, structure, theoretical calculations of 3-Fluoro-4-Hydroxybenzaldehyde: With evidence of hydrogen bonding

Fourier-Transform Laser Raman (3500-100 cm−1) and FT-IR (4000-400 cm−1) spectral measurements have been made for the solid 3-Fluoro-4-Hydroxybenzaldehyde. Geometry optimization and frequency calculations performed at two levels namely, RHF/6-31G* and B3LYP/6-31G* have yielded Cs symmetry with energies of −517.1388109 hartrees and −520.0240034 hartrees. A detailed interpretation of infrared and Raman spectra aided by the PEDs (potential energy distributions) for the computed frequencies has been reported. The PES scan yielded four distinct conformers out of which the most stable conformer is that with the orientation of CO of aldehyde group with respect to the hydroxyl group and fluorine in the cis form. The Fluorine substitution is seen to affect its structure and charge distributions in its vicinity as is seen by the NBO analysis and mulliken charges distribution.A broad IR band near 3130 cm−1, due to OH stretch shows evidence of hydrogen bonding. The aldehydic CH vibration predicted at 2801 cm−1 is observed at 2750 cm−1. Downshifting of the aldehydic CO stretch vibration predicted at 1725 cm−1 to an intense IR band at 1670 cm−1; increase in the frequency of in-plane bending vibration of OH as a shoulder absorption band at 1290 cm−1 from its predicted mode 1243 cm−1 are all further indications of OH⋯O bonding. Dimerization for the most stable conformer has been evaluated by B3LYP/6-31G* level. The dimer spectrum is seen to agree fairly well with the observed spectra. CF stretching vibration predicted at 1235 cm−1 is seen to couple with ring bending vibrations and is assigned to a strong Raman band at 1259 cm−1. The optimized structure and harmonic frequencies computed at B3LYP/6-31G* level are in good agreement with the experimental values.

Spectral Characteristics of Chemically Weathered Sandstones in the Yungang Grottoes, China

ABSTRACTMany of the sandstones at cultural heritage sites around the world are susceptible to chemical weathering, and long-term monitoring of the chemical weathering would be of great value for heritage conservation and would also provide reference data for environmental protection policies and projects. Reflectance spectroscopy is a potential tool for monitoring sandstone weathering due to its non-destructive characteristics. In this paper, we present the results of an investigation into the reflectance spectra of sandstones at the Yungang Grottoes, China, where the sandstones are variously fresh, calcite-dissolved, or argillitic-altered. We found several spectral absorptions, including those at 490, 675, 900, 1410, 1918, 2205, 2330, 2350, and 2380 nm. The absorptions at 490, 675, and 900 nm are related to hematite cement, while that at 2330 nm is associated with calcite cement. The absorptions at 1410, 2205, 2350, and 2380 nm are induced by the Al–OH vibration of kaolinite, and that at 1918 nm is related to crystal water. The calcite-dissolved sandstones have lower absorption intensities at 2330 nm than fresh sandstones, and the argillitic-altered sandstones have lower absorption intensities at 490, 675, and 900 nm than the fresh sandstones. In the 1st-derivative reflectance plots, the absorption peaks at ∼1400 nm shift towards shorter wavelengths with increasing kaolinite contents. The spectral features of the fresh, calcite-dissolved, and argillitic-altered sandstones are all different, and this means they can be distinguished spectroscopically, which demonstrates the usefulness of reflectance spectroscopy for the long-term monitoring of sandstone weathering in the Yungang Grottoes.

Structural Dynamics of Dispersed Titania During Dehydration and Oxidative Dehydrogenation Studied by In Situ UV Raman Spectroscopy

The structural dynamics of dispersed titania, i.e., silica supported titania, is investigated during dehydration and oxidative dehydrogenation (ODH) of ethanol using optical spectroscopy. UV Raman spectroscopy enabling resonance enhancements proves to be a valuable tool to identify Ti–OH, Ti–O–Si, and Ti–O–Ti groups. Upon dehydration, a transformation of Ti–OH into Ti–O–Si and Ti–O–Ti groups is observed. Two types of Ti–OH vibrations (isolated, geminal) are identified at around 700 and 800 cm− 1 in agreement with theoretical models. Dispersed titania is catalytically active in ethanol ODH with a performance comparable to dispersed vanadia. In situ UV Raman spectra reveal a consumption of Ti–O–Ti, Ti–O–Si, and Ti–OH groups during ethanol adsorption to the titania surface. The presented results are consistent with an ODH reaction mechanism involving a structural transformation of oligomerized or closely neighbored monomeric TiOX structures. The relevance of the proposed mechanism is discussed in the context of other supported transition metal oxide catalysts.

Frequencies of Stretching and Bending OH (OD) Vibrations in KDP (DKDP) Crystals, According to the Temperature Dependence of Their Raman Spectrum

The temperature dependence of OH (OD) vibrations in KDP (DKDP) crystals is studied by Raman spectroscopy in different scattering geometries at temperatures from 30 to 299 K. The three lower frequencies from the five well-known high-frequency bands of OH (OD) vibrations soften upon an increase in the paraelectric phase temperature. This results from the softening of the corresponding harmonic potential upon an increase in the interatomic distance, and these frequencies are attributed to bending vibrations. The two higher frequencies of OH (OD) vibrations are virtually independent of temperature with a slight tendency to grow upon an increase in the paraelectric phase temperature. This is in better agreement with the complicated temperature dependence of the energy levels of the double-well potential along a hydrogen bond and allows these bands to be attributed to stretching OH (OD) vibrations.

EDIBLE FILM FROM POLYBLEND OF GINGER STARCH, CHITOSAN, AND SORBITOL AS PLASTICIZER

Polyblend ginger starch/chitosan based edible film has been succesfully prepared and characterized. The purpose of this research was to produce edible film from polyblend of ginger starch, chitosan, and sorbitol as plasticizer. The resulted edible film were characterized by using FTIR, TGA and UTM. Edible film of ginger starch had OH vibration (3430 cm-1). Besides, edible film had elongation up to 15.63%. The thermal degradation of this material reached 208°C indicating high termal stability. The water uptake of the edible film was 42.85%. It concluded that edible film produce in this research has potential as a packaging.

Synthesis and Characterization of Allophane-Like as Chromium (Cr) Ion Adsorbent

The synthesis and characterization of allophane-like as chrom (Cr) ion adsorbent has been studied. The objectives of this study is to determine the characteristics of allophane-like and determine ratio of Al/Si, chromium solution pH, and contact time to get the best decreasing metal ion chrom (Cr) adsorption condition. The study was conducted with the ratio of Al/Si ratios 0.5; 0.75; 1.0; 1.25 and 1.5 from Tetraetyl Orthosilicate (TEOS) solution and Aluminium Nitrate Nonahydrate [Al(NO3)3.9H2O] in pH 3-4. The result of synthetic was characterized on functional groups and cristallinity. Experiment of adsorption ability using variation of Cr solution pH 3-7, contact time 30, 60, 90 and 120 minutes with batch method. The results by FTIR shows that functional groups-OH, the asymmetry groups O-Si-O or O-Al-O, relatively weak absorption which stronger then the presence of OH and bending vibration Si-O or Al-O on allophane-like. The best conditions of chromium metal adsorption with adsorbent allophane-like was obtained at pH 5, contact time 90 minutes, and the ratio Al/Si 1.5. Types of adsorption in this study follows Freundlich and Langmuir isotherm.

Reduced Near-Resonant Vibrational Coupling at the Surfaces of Liquid Water and Ice.

We study the resonant interaction of the OH stretch vibrations of water molecules at the surfaces of liquid water and ice using heterodyne-detected sum-frequency generation (HD-SFG) spectroscopy. By studying different isotopic mixtures of H2O and D2O, we vary the strength of the interaction, and we monitor the resulting effect on the HD-SFG spectrum of the OH stretch vibrations. We observe that the near-resonant coupling effects are weaker at the surface than in the bulk, for both water and ice, indicating that for both phases of water the OH vibrations are less strongly delocalized at the surface than in the bulk.

Hydrogenolysis of sorbitol over Ni supported on Ca- and Ca(Sr)-hydroxyapatites

Ca-hydroxyapatite (HAP) was synthesized with different morphologies, in needle (N), sphere (S) and rod (R) shapes. A partially Sr-substituted sample (Ca(Sr)-hydroxyapatite) with the stoichiometric composition of Sr0.6Ca9.4(PO4)6(OH)2, and possessing a rod shaped morphology was also hydrothermally synthesized (SrHAP-R). The samples were characterized by X-ray diffraction, Fourier-Transform infra-red spectroscopy (FT-IR), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS) and surface area measurement. Nickel (6 wt%) was loaded on the samples by an impregnation method. Rod-shaped hydroxyapatite (HAP-R) was more crystalline than the others. FT-IR results showed characteristic bands for (PO4)3− and OH vibrations. XPS results indicated Ni to be in the 2+ state, and O 1s satellite features revealed a phosphoric oxide environment in all the samples. The catalytic activities of the Ni-containing samples were tested in the hydrogenolysis of sorbitol into ethylene and propylene glycols in an aqueous medium in a stirred high pressure reactor at different process conditions. The most active catalyst was Ni/SrHAP-R. The catalyst was reusable many times with only a minor activity loss.

An Experimental Study on Transforming Montmorillonite to Glauconite: Implications for the Process of Glauconitization

AbstractThe objective of this study was to explore the geological origin of glauconite, which is believed to precipitate and mature very slowly (~1 Myr) in neritic environments (shallow water, oceanic coastal zones, at water depths of 100–200 m) with very low sedimentation rates. A series of simulation experiments was designed and carried out in sealed tubes placed in an oven and heated to a constant temperature of 50°C (±2°C) for 60 or 150 d. The parent materials used for these experiments were two low-Fe montmorillonites with different crystallinities. The montmorillonites were introduced to solutions with concentrations of 0.02–0.1 mol/L Fe3+ and 0.05–0.2 mol/L K+ with various values of pH and Eh. The products were analyzed using X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectrometry, electron spin resonance (ESR) spectrometry, scanning electron microscopy (SEM), and Mössbauer spectroscopy. The morphological changes from parent material to product were observed under SEM, which revealed the formation of a flaky mineral (e.g. a product formed in the interstitial spaces between montmorillonite crystals). The formation of a flaky mineral indicates that the product is a layer silicate. Qualitative analysis of XRD patterns revealed that the main product phase was a mica group mineral and the d060 value was consistent with the presence of glauconite (0.152 nm) and/or Fe-illite (0.150 nm). A glauconite and Fe-illite mineral assemblage formed in a weakly acidic solution, while Fe-illite, mixed-layer Fe-illite, and montmorillonite formed in neutral and alkaline solutions. Stretching vibrations of Fe(III)Fe(III)OH-AlFe(II)OH and/or MgFe(III)OH were observed in FTIR spectra (3550–3562 cm−1) of the products formed in acidic solutions, which along with the g = 1.978 ESR signal indicated that Fe(III) entered octahedral positions in the tetrahedral/octahedral/tetrahedral layer (TOT) platelets. The AlFe(II)OH-MgFe(III)OH (3550–3562 cm−1) and AlFe(III)OH (870 cm−1) vibrations were only observed in products formed in neutral and alkaline solutions. Analysis of the Mössbauer spectra showed that Fe(III) substituted for Al and Mg in the cis octahedral sites of montmorillonite. The simulation experiments demonstrated that the pH and redox conditions (Eh) of the environment controlled the nature of the product mineral species. Results of the present study revealed that glauconitization and illitization occurred under different conditions, where glauconitization preferentially occurred in an acidic environment and illitization preferentially occurred in a nearly neutral to alkaline environment.

Raman spectroscopic analysis of oral cells in the high wavenumber region

Raman spectroscopy can provide a molecular-level signature of the biochemical composition and structure of cells with submicrometer spatial resolution and could be useful to monitor changes in composition for early stage and non-invasive cancer diagnosis, both ex-vivo and in vivo. In particular, the fingerprint spectral region (400–1800cm−1) has been shown to be very promising for optical biopsy purposes. However, limitations for discrimination of dysplastic and inflammatory processes based on the fingerprint region have been demonstrated. In addition, the Raman spectral signal of dysplastic cells is one important source of misdiagnosis of normal versus pathological tissues. The high wavenumber region (2800–3600cm−1) provides more specific information based on NH, OH and CH vibrations and can be used to identify the subtle changes which could be important for discrimination of samples. In this study, we demonstrate the potential of the high-wavenumber spectral region in this context by collecting Raman spectra of nucleolus, nucleus and cytoplasm from oral epithelial cancer (SCC-4) and dysplastic (DOK) cell lines and from normal oral epithelial primary cells, in vitro, in water immersion, which were then analyzed by principal components analysis as a method to discriminate the spectra. Analysis was performed before and after digital subtraction of the bulk water signal. In the normal cell line, the three subcellular regions are well differentiated before water subtraction, although the discrimination of the two nuclear regions is less well defined after water subtraction. Comparing the respective subcellular regions of the three cell lines, before water subtraction, the cell lines can be discriminated using sequential PCA and Feature Discriminant Analysis with up to ~100% sensitivity and 97% specificity for the cytoplasm, which is improved to 100% sensitivity and 99% specificity for the nucleus. The results are discussed in terms of discrimination comparing the CH vibrational modes of nucleic acids, proteins and lipids. The potential role of the OH vibrations, considering free water and confined water, in the discrimination of cell cultures and pathological processes are also discussed.

Variation in the structure of a time-dependent SRS spectrum in microfiltered water

The time-dependent stimulated Raman scattering of light in water subjected to structural transformation by track membrane microfiltration is investigated. It is shown that the probability of SRS at the frequency of the ice spectral component in the band of stretching OH vibrations of water molecules decreases as a result of water filtration.