Vibrational spectroscopic characterization of the phosphate mineral hureaulite – (Mn,Fe)5(PO4)2(HPO4)2·4(H2O)

This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn_3.23, Fe_1.04, Ca_0.19, Mg_0.13)(PO₄)_2.7(HPO₄)_2.6(OH)_4.78. The Raman spectrum of hureaulite is dominated by an intense sharp band at 959 cm⁻¹ assigned to PO stretching vibrations of HPO₄²⁻ units. The Raman band at 989 cm⁻¹ is assigned to the PO₄³⁻ stretching vibration. Raman bands at 1007, 1024, 1047, and 1083 cm⁻¹ are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO₄²⁻ and PO₄³⁻ units. A set of Raman bands at 531, 543, 564 and 582 cm⁻¹ are assigned to the ν₄ bending modes of the HPO₄²⁻ and PO₄³⁻ units. Raman bands observed at 414, and 455 cm⁻¹ are attributed to the ν₂ HPO₄²⁻ and PO₄³⁻ units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood.     

Different level of fluorescence in Raman spectra of montmorillonites

The paper presents the study of selected montmorillonite standards by Raman spectroscopy and microscopy supported by elemental analysis, X-ray powder diffraction analysis and thermal analysis. Dispersive Raman spectroscopy with excitation lasers of 532 nm and 780 nm, dispersive Raman microscopy with excitation laser of 532 nm and 100× magnifying lens, and Fourier Transform-Raman spectroscopy with excitation laser of 1064 nm were used for the analysis of four montmorillonites (Kunipia-F, SWy-2, STx-1b and SAz-2). These mineral standards differed mainly in the type of interlayer cation and substitution of octahedral aluminium by magnesium or iron. A comparison of measured Raman spectra of montmorillonite with regard to their level of fluorescence and the presence of characteristic spectral bands was carried out. Almost all measured spectra of montmorillonites were significantly affected by fluorescence and only one sample was influenced by fluorescence slightly or not at all. In the spectra of tested montmorillonites, several characteristic Raman bands were found. The most intensive band at 96 cm⁻¹ belongs to deformation vibrations of interlayer cations. The band at 200 cm⁻¹ corresponds to deformation vibrations of the AlO₆ octahedron and at 710 cm⁻¹ can be assigned to deformation vibrations of the SiO₄ tetrahedron. The band at 3620 cm⁻¹ corresponds to the stretching vibration of structural OH groups in montmorillonites.     

Characteristics of inclusions in topaz from Serrinha pegmatite (Medina granite,Minas Gerais State,SE Brazil) studied by Raman spectroscopy

Eastern Brazilian Pegmatite Province includes many topaz-bearing pegmatitic bodies. Residual melts from the Fe–K-rich alkaline Medina granite (ca. 500 Ma) formed the Serrinha pegmatite—a system of branched thin pegmatite veins hosted by pink facies of the parent granite. The colourless topaz from Serrinha pegmatite contains both mineral and fluid inclusions. Microcline (513, 476, 456 cm⁻¹), albite (507, 479, 457 cm⁻¹), topaz (926, 858, 267, 239 cm⁻¹), quartz (463 cm⁻¹), rutile (610, 444 cm⁻¹), wolframite (884 cm⁻¹) and uranophane (968, 788 cm⁻¹) represent solid inclusions formed by fluid-induced processes from the pneumatolytic (∼600–400 °C) to hydrothermal (<400 °C) stages of pegmatite crystallization. Fluid inclusions are mainly liquid or liquid-gas, which contain CO₂ (marker bands ∼1388 cm⁻¹ and ∼1285 cm⁻¹) and traces of methane (2917 cm⁻¹). They are mainly of primary and pseudo-secondary origin, indicating tectonic quiescence during and after topaz crystallization (in agreement with the post-collisional nature of the parent granite). Topaz crystallized in high temperature conditions of the pneumatolytic stage at a depth around 8.5–10.0 km.     

Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate (struvite) and its isomorphous analogues. IX: Spectra of protiated and partially deuterated cubic magnesium caesium phosphate hexahydrate

Infrared and Raman spectra of cubic magnesium caesium phosphate hexahydrate, MgCsPO₄·6H₂O (cF100), and its partially deuterated analogues were analyzed and compared to the previously studied spectra of the hexagonal analogue, MgCsPO₄·6H₂O (hP50). The vibrational spectra of the cubic and hexagonal dimorphic analogues are similar, especially in the regions of HOH stretching and bending vibrations. In the difference IR spectrum of the slightly deuterated analogue (<5% D), one distinctive band appears at 2260 cm⁻¹ with a small shoulder at around 2170 cm⁻¹, but only one band is expected in the region of the OD stretchings of isotopically isolated HDO molecules. The small weak band could possibly result from second-order transitions (a combination of HDO bending and some libration of the same species) rather than statistical disorder of the water molecules. By comparing the IR spectra in the region of external vibrations of water molecules of the protiated compound recorded at RT (room temperature) and at LNT (liquid nitrogen temperature) and those in the series of the partially deuterated analogues, it can be stated with certainty that the bands at 924 and 817 cm⁻¹ result from librations of water molecules, rocking and wagging respectively. And the band at 429 cm⁻¹ can be safely attributed to a stretching Mg–O_w mode. In the ν₃(PO₄) and ν₄(PO₄) region in the infrared spectra, one band in each is observed, at 995 and 559 cm⁻¹, respectively. In the region of the ν₁ modes, in the Raman spectrum of the protiated compound, one very intense band was observed at 930 cm⁻¹ which is only insignificantly shifted to 929 cm⁻¹ in the spectrum of the perdeuterated compound. The band at 379 cm⁻¹ in the Raman spectrum could be assigned to the ν₂(PO₄) modes. With respect to the phosphate ion vibrations, the comparison between the two polymorphic forms of MgCsPO₄·6H₂O and their deuterated compounds shows that ν₁(PO₄) and ν₃(PO₄) appear at lower wavenumbers in the cubic phase than in the hexagonal phase. These data are in full agreement with the lower repulsion potential at the cubic lattice sites compared with that for the hexagonal lattice sites.     

In-plane chemical pressure in (U1−yCey)O2 studied by Raman spectroscopy

We investigate the nature of bonding and charge states in (U_1−yCe_y)O₂ (y = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) by Raman spectroscopy. Raman spectrum of UO₂ exhibits two prominent bands below 1000 cm⁻¹, a F_2g mode at 446 cm⁻¹ and a F_1u LO mode at 578 cm⁻¹. As y is increased from 0 to 0.6, the F_1u exhibits a large blue shift of 90 cm⁻¹, and from y = 0.6 to 1.0, a red shift of 54 cm⁻¹. We show that our results can be interpreted as arising from anisotropic compression/relaxation of the lattice under Ce substitution and this can give an indication of its charge states. Alternate interpretations have been given in the literature on the effect of substituents and dopants to the Raman spectra of UO₂ and CeO₂. The present interpretation of chemical stress effects can be taken as another plausible explanation.     

Vibrational spectroscopic study of syngenite formed during the treatment of liquid manure with sulphuric acid

Syngenite (K₂Ca(SO₄)₂·H₂O), formed during treatment of manure with sulphuric acid, was studied by infrared, near-infrared (NIR) and Raman spectroscopy. C_s site symmetry was determined for the two sulphate groups in syngenite (P2₁/m), so all bands are both infrared and Raman active. The split ν₁ (two Raman+two infrared bands) was observed at 981 and 1000 cm⁻¹. The split ν₂ (four Raman+four infrared bands) was observed in the Raman spectrum at 424, 441, 471 and 491 cm⁻¹. In the infrared spectrum, only one band was observed at 439 cm⁻¹. From the split ν₃ (six Raman+six infrared) bands three 298 K Raman bands were observed at 1117, 1138 and 1166 cm⁻¹. Cooling to 77 K resulted in four bands at 1119, 1136, 1144 and 1167 cm⁻¹. In the infrared spectrum, five bands were observed at 1110, 1125, 1136, 1148 and 1193 cm⁻¹. From the split ν₄ (six infrared+six Raman bands) four bands were observed in the infrared spectrum at 604, 617, 644 and 657 cm⁻¹. The 298 K Raman spectrum showed one band at 641 cm⁻¹, while at 77 K four bands were observed at 607, 621, 634 and 643 cm⁻¹. Crystal water is observed in the infrared spectrum by the OH-liberation mode at 754 cm⁻¹, OH-bending mode at 1631 cm⁻¹, OH-stretching modes at 3248 (symmetric) and 3377 cm⁻¹ (antisymmetric) and a combination band at 3510 cm⁻¹ of the H-bonded OH-mode plus the OH-stretching mode. The near-infrared spectrum gave information about the crystal water resulting in overtone and combination bands of OH-liberation, OH-bending and OH-stretching modes.     

Photo-luminescence studies of strontium barium niobate crystals doped with Cr3+ ions

This paper reports the photo-luminescence spectroscopic results of Strontium–Barium–Niobate, Sr_x,Ba_1−xNb₂O₅ (SBN, x = 0.61 for near congruent composition) crystals doped with Cr₂O, at cryogenic temperature (20 K). The experimental results reveal the need of re-assignment of the Cr³⁺ ions defect centres in this material. For first time, a broad emission band in the near infrared region centred at ca. 950 nm is reported. This emission band has micro-seconds decaytime constant and a FWHM band-width > 1700 cm⁻¹ and has been ascribed to the vibronically assisted ⁴T₂ → ⁴A₂ transition. A much narrower emission band centred at ca. 764 nm with milli-seconds decaytime constant and a FWHM band-width of ca. 170 cm⁻¹ is correlated to the ²E → ⁴A₂ radiative transition (R-line).     

Electronic structure and Raman spectroscopy study of dibarium magnesium orthoborate,Ba2Mg(BO3)2

The samples of dibarium magnesium orthoborate Ba₂Mg(BO₃)₂ were synthesized by solid-state reaction. The X-ray diffraction (XRD) patterns and Raman spectra of the samples were collected. Electronic structure and vibrational spectroscopy of Ba₂Mg(BO₃)₂ were systematically investigated by first principle calculation. A direct band gap of 4.4 eV was obtained from the calculated electronic structure results. The top valence band is constructed from O 2p states and the low conduction band mainly consists of Ba 5d states. Raman spectra for Ba₂Mg(BO₃)₂ polycrystalline were obtained at ambient temperature. The factor group analysis results show the total lattice modes are 5E_u + 4A_2u + 5E_g + 4A_1g + 1A_2g + 1A_1u, of which 5E_g + 4A_1g are Raman-active. Furthermore, we obtained the Raman active vibrational modes as well as their eigenfrequencies using first-principle calculation. With the assistance of the first-principle calculation and factor group analysis results, Raman bands of Ba₂Mg(BO₃)₂ were assigned as E_g (42 cm⁻¹), A_1g (85 cm⁻¹), E_g (156 cm⁻¹), E_g (237 cm⁻¹), A_1g (286 cm⁻¹), E_g (564 cm⁻¹), A_1g (761 cm⁻¹), A_1g (909 cm⁻¹), E_g (1165 cm⁻¹). The strongest band at 928 cm⁻¹ in the experimental spectrum is assigned to totally symmetric stretching mode of the BO₃ units.     

Development of micro-tubular SOFCs with an improved performance via nano-Ag impregnation for intermediate temperature operation

Micro-tubular solid-oxide fuel cell consisting of a 10-μm thick (ZrO₂)_0.89(Sc₂O₃)_0.1(CeO₂)_0.01 (ScSZ) electrolyte on a support NiO/(ScSZ) anode (1.8 mm diameter, 200 μm wall thickness) with a Ce_0.8Gd_0.2O_1.9 (GDC) buffer-layer and a La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF)/GDC functional cathode has been developed for intermediate temperature operation. The functional cathode was in situ formed by impregnating the well-dispersed nano-Ag particles into the porous LSCF/GDC layer using a citrate method. The cells yielded maximum power densities of 1.06 W cm⁻² (1.43 A cm⁻², 0.74 V), 0.98 W cm⁻² (1.78 A cm⁻², 0.55 V) and 0.49 W cm⁻² (1.44 A cm⁻², 0.34 V), at 650, 600 and 550 °C, respectively.     

One-step fabrication of chitosan–hematite nanotubes composite film and its biosensing for hydrogen peroxide

This work reports on a novel chitosan–hematite nanotubes composite film on a gold foil by a simple one-step electrodeposition method. The hybrid chitosan–hematite nanotubes (Chi–HeNTs) film exhibits strong electrocatalytic reduction activity for H₂O₂. Interestingly, two electrocatalytic reduction peaks are observed at −0.24 and −0.56 V (vs SCE), respectively, one controlled by surface wave and the other controlled by diffusion process. The Chi–HeNTs/Au electrode shows a linear response to H₂O₂ concentration ranging from 1 × 10⁻⁶ to 1.6 × 10⁻⁵ mol L⁻¹ with a detection limit of 5 × 10⁻⁸ mol L⁻¹ and a sensitivity as high as 1859 μA μM⁻¹ cm⁻².     

Excess molar volumes of binary mixtures of 2,2,2-trifluoroethanol with water,or acetone,or 1,4-difluorobenzene,or 4-fluorotoluene,or α,α,α, trifluorotoluene or 1-alcohols at a temperature of 298.15 K and pressure of 101 kPa

Excess molar volumes V_m^E of binary mixtures of 2,2,2-trifluoroethanol with water, or acetone, or methanol, or ethanol, or 1-alcholos, or 1,4-difluorobenzene, or 4-fluorotoluene or α,α,α-trifluorotoluene were measured in a vibrating tube densimeter at temperature 298.15 K and pressure of 101 kPa. The V_m^E extrema are: 1.540 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1-heptanol); 1.452 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1-hexanol); 1.238 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1-butanol); 0.821 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 4-fluorotoluene); 0.817 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + ethanol); 0.647 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + methanol); 0.618 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + acetone); 0.605 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + α,α,α-trifluorotoluene); 0.485 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + 1,4-difluorobenzene); and −0.656 cm³ · mol⁻¹ for (2,2,2-trifluoroethanol + water). The limiting excess partial molar volumes are estimated.     

Vibrational spectroscopic study of SiO2-based nanotubes

Novel organic–inorganic hybrid nanotubes containing silica and ethane (EtSNT), ethylene (ESNT) and acetylene (ASNT) units, as well as brominated ESNT (Br-ESNT) and glycine-modified Br-ESNT (Gly-ESNT) have been studied by IR and Raman spectroscopy. The results are compared with the spectral features for conventional silica nanotubes (SNT) and amorphous silica. Bands peculiar to organic moieties have been detected and assigned. Assignment of the silicate backbone vibrations was based on the results of normal coordinate calculations. Furthermore, characteristic silicate, so-called ‘nanotube’ vibrations have been identified and their band positions have been summarized to serve as a future reference for such compounds. SiOSi antisymmetric stretchings were observed in the range 1000–1110 cm⁻¹, while the symmetric stretchings appeared between 760 and 960 cm⁻¹ for EtSNT, ESNT and Br-ESNT.Force constants have been refined for models of the repeating structure units: O₃SiOSi(OSi)₃ for SNT and SiCH_nCH_nSi(OSi)₃ for organosilica nanotubes (n = 2, EtSNT; n = 1, ESNT and n = 0, ASNT). The calculated SiO stretching force constants were increased from 4.79 to 4.88 and 5.11 N cm⁻¹ for EtSNT, ESNT and ASNT, respectively. The force constants have been compared with those for several silicates and SiO bond length are predicted and discussed.     

Electronic and vibrational circular dichroism spectroscopic study of non-covalent interactions of meso-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin with (dG-dC)10 and (dA-dT)10

The non-covalent interactions of (dG-dC)₁₀ and (dA-dT)₁₀ with 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) were studied using the combination of electronic circular dichroism (ECD), vibrational circular dichroism (VCD) spectroscopy, and UV–vis and IR absorption spectroscopy at different ratios of both components r = [oligonucleotide]/[TMPyP] = 2/1–10/1 where [oligonucleotide] and [TMPyP] are the amount concentrations of oligonucleotide per base-pair and TMPyP, respectively. It was shown that TMPyP with (dG-dC)₁₀ provided hemiintercalative binding mode for r = 4/1 that is manifested in vibrational spectra: The absorption band assigned to the C6O6 stretching vibration of guanine is shifted from 1683 to 1672 cm⁻¹, the corresponding VCD couplet from 1694(−)/1674(+) to 1684(−)/1663(+) cm⁻¹ and its intensity decreases. The absorption band assigned to the C2O2 stretching vibration of cytosine is shifted from 1652 to 1644 cm⁻¹ and its intensity increases. TMPyP with (dA-dT)₁₀ provided three binding modes: (i) external binding to the phosphate backbone, (ii) external minor groove binding for the ratios >6/1 and (iii) external major groove binging associated with the partial B- to Z-transition for the ratios <4/1. The major groove binding is manifested in VCD spectra by the intensity decrease of the bands 1655 and 1638 cm⁻¹ assigned to the thymine vibrations while the bands assigned to the adenine vibrations are unchanged. In the (dA-dT)₁₀–TMPyP complexes, the external binding to the phosphate backbone accompanied by self-stacking of porphyrins along the phosphate backbone chain is preferred at temperatures higher than 40 °C.     

Partial oxidation of ethane to syngas in an oxygen-permeable membrane reactor

A perovskite-type oxide of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO) with mixed electronic and oxygen ionic conductivity at high temperatures was used as an oxygen-permeable membrane. A tubular membrane of BSCFO made by extrusion method has been used in the membrane reactor to exclusively transport oxygen for the partial oxidation of ethane (POE) to syngas with catalyst of LiLaNiO/γ-Al₂O₃ at temperatures of 800–900 °C. After only 30 min POE reaction in the membrane reactor, the oxygen permeation flux reached at 8.2 ml cm⁻² min⁻¹. After that, the oxygen permeation flux increased slowly and it took 12 h to reach at 11.0 ml cm⁻² min⁻¹. SEM and EDS analysis showed that Sr and Ba segregations occurred on the used membrane surface exposed to air while Co slightly enriched on the membrane surface exposed to ethane. The oxygen permeation flux increased with increasing of concentration of C₂H₆, which was attributed to increasing of the driving force resulting from the more reducing conditions produced with an increase of concentration of C₂H₆ in the feed gas. The tubular membrane reactor was successfully operated for POE reaction at 875 °C for more than 100 h without failure, with ethane conversion of ∼100%, CO selectivity of >91% and oxygen permeation fluxes of 10–11 ml cm⁻² min⁻¹.     

Ni infiltrated Sr2Fe1.5Mo0.5O6-δ-Ce0.8Sm0.2O1.9 electrode for methane assisted steam electrolysis process

It is an effective way to substitute air to methane in the anode of solid oxide electrolysis cells to reduce the electrical consumption for simultaneously producing H₂ and high-quality syngas. In the methane assisted mode, the thermodynamic properties and Nernst potential exhibit one order of magnitude reduction of applied voltage to produce comparable electrolysis current. Ni catalysts are infiltrated to the SFM-SDC anode to improve the catalytic properties for methane assisted steam electrolysis. After Ni infiltration, surface oxygen exchange coefficient is effectively accelerated from 3.03 × 10^− 5 to 2.20 × 10^− 4 cm s^− 1, and the current density is significantly enhanced from − 487 to − 1022 mA cm^− 2 at 850 °C and 0.5 V.     

Variable temperature diffuse reflectance infrared Fourier transform spectroscopic investigation of the effect of ball milling on the water sorbed to kaolin

Variable temperature DRIFTS has been used to investigate temperature variation of the number and population of the different environments occupied by water on unmilled kaolin and samples ball milled for 3, 10 and 30 min. Increasing the milling time resulted in structural damage of the kaolin and an increase in the amount of hydrogen bonded water indicated by bands in the OH stretching and bending regions. Curve fitting of the spectra, collected at 50 °C intervals in the temperature range 25–500 °C, established that the intensity of the bands diminished as the temperature was increased but also revealed bands that were more stable to high temperatures or were generated as the sample temperature was increased. Bands at 3750, 3386 and 3200 cm⁻¹ and 1680, 1650, 1634 and 1600–1580 cm⁻¹ were identified in the OH-stretching and bending regions, respectively. In particular a band at 1670 cm⁻¹ has been attributed to strongly hydrogen bonded water which acts to hold the deformed kaolin sheets together. Upon aging the samples the intensity of this band decreased and was replaced by a band at 1630 cm⁻¹. Boehmite was tentatively identified as a product of the milled kaolin.     

Infrared study and isotopic effect of magnesium hydroxide

The IR spectra of polycrystalline Mg(OH)₂ and Mg(OD)₂ are reported in the 4000–40 cm⁻¹ region. Band assignments were discussed on the basis of isotopic band shifts of the fundamental vibrations by combining the results of factor group analysis for D_3d³ crystal structure with the Teller–Redlich product rule for crystal vibrations. The band assignments proposed are different from the previous IR spectroscopic studies.     

Electronic and vibrational spectra of tourmaline – The impact of electron beam irradiation and heat treatment

Irradiation and heat treatment were performed on tourmalines of various colors from Antandrokomby, Madagascar. The samples were irradiated with 10 MeV electrons to fluencies of 2 ×10¹⁷ cm⁻² for 1 h and were heated at 550 °C for 3 h in air. Their electronic and vibrational spectra were investigated by UV–vis, mid-infrared, and WD-XRF spectroscopy for comparison to pristine samples. Changes in the Mn³⁺ ions after irradiation resulted in darker pink tourmalines, which had absorption peaks at 390 and 520 nm. These samples became colorless after subsequent heat treatment. After irradiation, colorless, light blue and yellow tourmalines displayed a new absorption band at 365 nm. Alteration of the stretching absorption bands and wavenumber after irradiation could be explained by the following reactions:OH⁻ + e⁻ beam irradiation → O⁻ + H°,Mn²⁺ + e⁻ beam irradiation → Mn³⁺ + e⁻ andFe²⁺ + e⁻ beam irradiation → Fe³⁺ + e⁻.Stretching vibration of the BO₃ structure occurred at 1330 cm⁻¹, while the SiO vibration absorption bands were assigned to around 1100 cm⁻¹. Colorless, green, and yellow tourmalines showed high-intensity peaks around 3608 and 3505 cm⁻¹ after irradiation. Pink and dark green tourmalines showed low-intensity peaks at 3605 and 3585 cm⁻¹, respectively. The combination modes of stretching and bending in the range of 4600–4300 cm⁻¹ were split after irradiation and heat treatment, and different color changes occurred after irradiation.     

Raman spectra of carriers in ionic-liquid-gated transistors fabricated with poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene)

We observed the Raman spectra of carriers, positive polarons and bipolarons, generated in a poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14) film by FeCl₃ vapor doping. Electrical conductivity and Raman measurements indicate that the dominant carriers in the conducting state were bipolarons. We identified positive polarons and bipolarons generated in an ionic-liquid-gated transistor (ILGT) fabricated with PBTTT-C14 as an active semiconductor and an ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [BMIM][TFSI] as a gate dielectric using Raman spectroscopy. The relationship between the source−drain current (I_D) at a constant source−drain voltage (V_D) and the gate voltage (V_G) was measured. I_D increased above −V_G = 1.1 V and showed a maximum at −V_G = 2.0 V. Positive polarons were formed at the initial stage of electrochemical doping (−V_G = 0.8 V). As I_D increased, positive bipolarons were formed. Above V_G = −2.0 V, bipolarons were dominant. The charge density (n), the doping level (x), and the mobility of the bipolarons were calculated from the electrochemical measurements. The highest mobility (μ) of bipolarons was 0.72 cm² V⁻¹ s⁻¹ at x = 110 mol%/repeating unit (−V_G = 2.0 V), whereas the highest μ of polarons was 4.6 × 10⁻⁴ cm² V⁻¹ s⁻¹ at x = 10 mol%.     

High-resolution infrared analysis of seven fundamental bands of gaseous isothiazole between 750 and 1500 cm−1

The gas phase IR spectrum of isothiazole, C₃H₃NS, between 550 and 1700 cm⁻¹ was recorded with a resolution of ca. 0.003 cm⁻¹. The rotational structure of seven fundamental bands in the region 750–1500 cm⁻¹ has been assigned and analysed by the Watson Hamiltonian model. A number of local resonances in the bands have been identified and explained qualitatively in terms of Coriolis interactions. For each band upper state spectroscopic constants, including band center, rotational constants, and quartic centrifugal distortion constants are given. From observed crossings due to resonances we locate the weak bands ν₉(A′) and ν₁₃(A′) at 1041.9(2) and 642.0(3) cm⁻¹, respectively. The anharmonic frequencies have been determined using a cc-pVTZ basis set, at the MP2 and B3LYP levels; the two theoretical methods give very similar results for rotational constants, anharmonic band center frequencies and distortion constants, and many of these are in good agreement with experiment.