Attenuated Total Reflection Spectra Research Articles

Bidentate cation-anion coordination in the ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate supported by vibrational spectra and NBO, AIM and SQMFF calculations

Experimental attenuated total reflectance (ATR) and Raman spectra for the synthesized ionic liquid 1-Ethyl-3-methylimidazolium hexafluorophosphate [EMIM+][PF6−] have been combined with the functional hybrid B3LYP and the 6-31G∗ and 6-311++G∗∗ basis sets in order to evaluate the coordination mode of [PF6−] anion and determine the its structural, electronic, topological and vibrational properties. The scaled quantum mechanical force fields (SQMFF) methodology allowed us to obtain a set of scaled force constants fitting the observed wavenumbers because, so far, they have not reported. Experimental ATR and Raman spectra for the ionic liquid [EMIM+][PF6−] in the solid phase are consistent with the corresponding predicted by using both levels of theory. Here, complete vibrational assignments of 72 normal modes of vibration expected for ionic liquid were performed by using B3LYP/6-311++G∗∗ level and considering that the [PF6−] anion adopts a bidentate coordination mode. Atomic Merz-Kollman (MK) charges and bond orders studies have revealed a distorted octahedral symmetry of anion in the ionic liquid and have suggested bidentate coordination of anion by two C–H⋯F hydrogen bonds, as experimentally was also proposed. Natural bond orbital (NBO) and atoms in molecules (AIM) calculations support the high stability of ionic liquid and its high dipole moment value. Frontier orbitals for the three species show that the [PF6−] anion increases the reactivity of ionic liquid. Here, we determine that the B3LYP/6-311++G∗∗ molecular force field for the ionic liquid [EMIM+][PF6−] with the bidentate coordination mode adopted by [PF6−] anion is well represented, as also was supported by the scaled force constants calculated for both C–H⋯F hydrogen bonds.

Evaluation of surface roughness of metal films using plasmonic Fano resonance in attenuated total reflection

Attenuated total reflection (ATR) by surface plasmon polariton (SPP) is a method for evaluating the dispersion relation of SPP from the position of a dip in the reflection spectrum. However, recent studies have shown that the dips are displaced from SPP resonance because they are produced by a type of Fano resonance, i.e., the interference between the resonant reflection process accompanied by resonant excitation of SPP and the direct reflection process without resonant excitation. This result suggests that the system properties difficult to be achieved in the dispersion relation of SPP can be characterized using the ATR method. In this study, we investigate the effect of surface roughness due to nanosized dimples created in the initial stage of pitting corrosion on the ATR spectrum, from the viewpoint of Fano resonance. Using the temporal coupled-mode method, it is shown that the Fano resonance in ATR is caused by the phase change of direct reflection because of the absorption on the metal surface, and the spectral shape is determined by this phase, along with the ratio of the external (radiative) decay rate to the total decay rate of the resonant mode. Moreover, it is clarified that the internal and external decay rates extracted from the ATR spectrum provide information on corrosion, such as the effective thickness of the metal film and the randomness in dimple distribution.

Transformation of aqueous protein attenuated total reflectance infra-red absorbance spectroscopy to transmission.

Infrared (IR) spectroscopy is increasingly being used to probe the secondary structure of proteins, especially for high-concentration samples and biopharmaceuticals in complex formulation vehicles. However, the small path lengths required for aqueous protein transmission experiments, due to high water absorbance in the amide I region of the spectrum, means that the path length is not accurately known, so only the shape of the band is ever considered. This throws away a dimension of information. Attenuated total reflectance (ATR) IR spectroscopy is much easier to implement than transmission IR spectroscopy and, for a given instrument and sample, gives reproducible spectra. However, the ATR-absorbance spectrum varies with sample concentration and instrument configuration, and its wavenumber dependence differs significantly from that observed in transmission spectroscopy. In this paper, we determine, for the first time, how to transform water and aqueous protein ATR spectra into the corresponding transmission spectra with appropriate spectral shapes and intensities. The approach is illustrated by application to water, concanavalin A, haemoglobin and lysozyme. The transformation is only as good as the available water refractive index data. A hybrid of literature data provides the best results. The transformation also allows the angle of incidence of an ATR crystal to be determined. This opens the way to using both spectral shape and spectra intensity for protein structure fitting.

SYNTHESIS AND STUDY OF ATR SPECTRA OF POLYANILINE/GRA NANOCOMPOSITES

Nano composites are a particular class of materials resulting from combinations of two or more compounds by an appropriate method, which results in materials having unique physicochemical properties and large potential for application in diverse areas. Some of the distinctive properties of polymeric Nano composites can be derived from the successful combination of the uniqueness of the parent constituents into a particular polymer. These composites vary from the pure polymers in respect to some of the physical and chemical properties and hence are useful for many different applications. We synthesized Polyaniline (PANI) in Emeraldine form by chemical oxidation method using Ferric Chloride (FeCl3) as a catalyst and Hydrogen peroxide (H2O2), as an oxidant. Simultaneous synthesis of polyaniline (PANI)/ GRA Nano composites was also done by the same chemical oxidation method. The characteristic absorption peaks of Attenuated Total Reflectance (ATR) spectra for GRA, PANI and PANI/GRA provide information about the changes in the chemical structure of PANI. ATR spectra also give indication that the incorporation of GRA in the matrix of PANI seems to be effective for the improvement of the physicochemical properties of the Polyaniline.

ANALYSIS OF PALM OIL AS OIL ADULTERANT IN OLIVE AND PUMPKIN SEED OILS IN TERNARY MIXTURE SYSTEMS USING FTIR SPECTROSCOPY AND CHEMOMETRICS

Objective: The study was designed to develop Fourier transform infrared (FTIR) spectroscopy in conjunction with chemometrics techniques of multivariate calibration and discriminant analysis (DA) for analysis of palm oil in a ternary mixture with EVOO and PSO.
 Methods: FTIR spectra of pure palm oil (PO), extra virgin olive oil (EVOO), pumpkin seed oil (PSO) and its ternary mixtures randomly prepared were scanned using FTIR spectrophotometer at wavenumbers of 4000-650 cm-1 corresponding to mid-infrared region, with resolution of 8 cm-1 and 32 scanning using sampling technique of attenuated total reflectance (ATR). Two calibrations in multivariate models, namely principle component (PCR) and partial least square (PLS) regressions were used to facilitate quantification of PO.
 Results: The PLS using first derivative FTIR–ATR spectra at 3100-2750 combined with 1500-663 cm-1 showed the best prediction models for quantification of PO in ternary mixtures with EVOO and PSO. Using this condition, correlation coefficient (R) values for the relationship between actual values and FTIR predicted values of 0.9967 and 0.9906 were achieved in calibration and validation models, respectively. The errors in calibration and prediction models, expressed by RMSEC and RMSEP, were low, i.e. 0.0080% and 0.0152%, respectively. DA using absorbance values at the same wavenumbers also offered the optimum discrimination model for discrimination between PO and PO mixed with EVOO and PSO in ternary mixtures.
 Conclusion: This result concluded that FTIR spectra in conjunction with DA (for classification) and PLS (for quantification) is fast and accurate tools during the analysis of PO as oil adulterant in EVOO and PSO.

Differential ATR FTIR spectroscopy of membrane fouling: Contributions of the substrate/fouling films and correlations with transmembrane pressure

This study examined the formation of fouling films deposited on the surface of a polyethersulfone (PES) membrane during the filtration of alginate solutions with various ionic strengths. Membrane fouling was characterized by changes of the transmembrane pressure (TMP) and ex situ measured attenuated total reflectance (ATR) Fourier-transform IR (FTIR) spectra at varying stages of filtration runs. The ATR spectra that comprise the vibration bands characteristic of the PES substrate and the deposited film were processed taking into the gradual weakening of the PES substrate-specific bands, whose intensity was shown to depend on the wavenumber of IR radiation and the thickness of the deposited layer. Strongly linear correlations between ratios of first derivatives intensity and wavenumbers of the PES reference lines were established. Calculations of the PES bands’ attenuation coefficients allowed determining the apparent thickness and ATR FTIR vibrations of the fouling films per se. Strong correlations between TMP development and ATR-determined apparent thickness of the fouling layers were observed. The intensity of ATR absorbance at 3200 cm−1 was linearly correlated with TMP development for small TMP values before the point of rapidly developing failure of the hydraulic permeability of the system was reached.

Application of Different Fourier Transform Infrared (FT-IR) Methods in the Characterization of Lime-Based Mortars with Oxblood.

Organic compounds have frequently been added into lime mortars for property modifications, in order to satisfy various functional needs in building techniques. This study applies Fourier transform infrared (FT-IR) spectroscopy in transmission, reflection, and attenuated total reflection (ATR) modes to characterize lime-based mortar specimens containing oxblood, which has been used as additive as a common practice of long history in many parts of the world. The specimens were prepared basing upon a 19th-century Italian historic recipe, with the intention to have a better understanding on the possible characteristics of such mortars. Thermal analysis, color measurement, and static contact angle test were also used. After curing, the specimens show a distinctive dark-red color on the top surface, which is different from the bulk. Color measurements on the surface suggest that this color was formed at an early stage and was able to maintain stable for a relatively long period of time. Both transmission and reflection FT-IR confirm the preferential accumulation of proteins on the top surface, which should have induced their water repellency according to the static contact angle test. In addition, specimens show weaker calcite bands in FT-IR transmission, reflection, as well as ATR spectra; the pattern of ATR spectra after the thermal analysis to 500 °C suggests the formation of amorphous calcium carbonate, which is related to the presence of oxblood.

Probing of Free Charge Carriers in Nanostructured Silicon Layers by Attenuated Total Reflectance Technique

Infrared spectroscopy in attenuated total reflection (ATR) mode is used to evaluate the concentration of free charge carriers (electrons) in n‐type macroporous silicon (Si) layers formed by metal‐assisted chemical etching of crystalline silicon (c‐Si) followed by additional doping with phosphorus. The ATR spectra are fitted by considering an effective medium approximation and Drude model, which is modified to describe an additional scattering of the charge carriers on the surface of Si nanocrystals. The electron concentration is of the order of 1019 cm−3 and it is slightly dependent on the layer thickness, while the surface scattering of charge carriers increases with layer thickness. The obtained results are discussed in view of possible applications of the ATR method for an express diagnostics of doping efficiency of Si nano‐ and microstructures for photonic and thermoelectrical applications.

On the Widths of Bands in the Infrared Spectra of Oxyanions.

It is well known that the antisymmetric stretching (ν3) band in the mid-infrared spectra of oxyanion salts is usually very broad, whereas all the other fundamental bands are narrow. In this paper, we propose that the underlying cause of the increased width is the effect of the very high absorption index of this band for samples prepared with a range of particle sizes. When oxyanion salts are ground, the diameter of the resulting particles usually varies from less than 100 nm to about 2 µm. While the peak absorbance of the ν3 band of the smaller particles (diameter < 200 nm) is less than 1, that of the larger particles can be as high as 6. We show that the average transmittance of these particles leads to a significant band broadening, especially when there are small voids in the resulting sample. Although the effect is always seen in the spectra of alkali halide disks and mineral oil mulls, it is also seen in diffuse reflection and attenuated total reflection (ATR) spectra. Because the depth of penetration of infrared radiation below 1500 cm-1 is less than 1 µm for ATR spectra measured with a germanium internal reflection element (IRE), the width of the ν3 band is lower than that of ATR spectra measured with an IRE of lower refractive index such as diamond on zinc selenide.

Development of Infrared Library Search Prefilters for Automotive Clear Coats from Simulated Attenuated Total Reflection (ATR) Spectra

A previously published study featuring an attenuated total reflection (ATR) simulation algorithm that mitigated distortions in ATR spectra was further investigated to evaluate its efficacy to enhance searching of infrared (IR) transmission libraries. In the present study, search prefilters were developed from transformed ATR spectra to identify the assembly plant of a vehicle from ATR spectra of the clear coat layer. A total of 456 IR transmission spectra from the Paint Data Query (PDQ) database that spanned 22 General Motors assembly plants and served as a training set cohort were transformed into ATR spectra by the simulation algorithm. These search prefilters were formulated using the fingerprint region (1500 cm-1 to 500 cm-1). Both the transformed ATR spectra (training set) and the experimental ATR spectra (validation set) were preprocessed for pattern recognition analysis using the discrete wavelet transform, which increased the signal-to-noise of the ATR spectra by concentrating the signal in specific wavelet coefficients. Attenuated total reflection spectra of 14 clear coat samples (validation set) measured with a Nicolet iS50 Fourier transform IR spectrometer were correctly classified as to assembly plant(s) of the automotive vehicle from which the paint sample originated using search prefilters developed from 456 simulated ATR spectra. The ATR simulation (transformation) algorithm successfully facilitated spectral library matching of ATR spectra against IR transmission spectra of automotive clear coats in the PDQ database.

Optical properties of nucleobase thin films as studied by attenuated total reflection and surface-enhanced Raman spectroscopy

Optical properties of nucleobase thin films were studied by attenuated total reflection (ATR) and surface-enhanced Raman spectroscopy (SERS). Adenine and guanine films were deposited on fused silica and silver at room temperature by thermal evaporation, and the normal dispersion of refractive indices of transparent adenine and guanine films in the visible and near-infrared regions were analyzed. The measured ATR spectra of adenine (guanine) films and numerical simulations by optical transfer matrix formalism demonstrate that the shift of surface plasmon resonance (SPR) wavelength is approximately linearly proportional to the adenine (guanine) film thickness, indicating that SPR can be used for quantitative measurements of biomaterials. The Raman spectra indicated that the adenine (guanine) films can be deposited by thermal evaporation. The adenine (guanine) films on silver exhibited Raman intensity enhancement as compared to those on glass, which was attributed to the SPR effect of silver platform and might play a role as a hot plate for SERS detection of biomaterials.

Rabi like angular splitting in Surface Plasmon Polariton – Exciton interaction in ATR configuration

We have studied the coupling of propagating Surface Plasmon Polaritons (SPP) on silver films and excitons in CdS quantum dots (QDs). We employed the Kretschmann-Raether configuration of the attenuated total reflection (ATR) to propagate the SPP on silver film of thickness 47.5 nm at three different wavelengths. The CdS QD have been chemically synthesized with particular size such that its exciton of energy would resonate with SPP. High resolution transmission electron microscopy (HRTEM) and scan tunneling microscopy (STM) were used to measure the corresponding QDs size and confirm its shape. Further confirmation of the size has been performed by the effective mass approximation (EMA) model utilizing the band gap of the prepared QDs. The band gaps have been measured through UV–vis absorption spectra as well as scan tunneling spectroscopy (STS). The coupling has been observed as two branching dips in the ATR spectra indicating Rabi like splitting. To the best of our knowledge, this is the first time that Rabi interaction is directly observed in an ATR angular spectra. This observation is attributed to the use a high resolution angular scan (±0.005°), in addition to the Doppler width of the laser line as well as the energy distribution of the excitons. The effect of three different linker molecules (TOPO, HDA), (Pyridine) and (Tri-butylamine) as surface ligands, on SPP-Exciton interaction has been examined.

Surface Plasmon Polariton Resonance of Gold, Silver, and Copper Studied in the Kretschmann Geometry: Dependence on Wavelength, Angle of Incidence, and Film Thickness

Surface plasmon polariton (SPP) resonance spectra for noble metals (Au, Ag, and Cu) were comprehensively studied in the Kretschmann attenuated total reflection (ATR) geometry, in the wavelength (λ) range from 300 to 1000 nm with the angle of incidence (θ) ranging from 45 to 60° and the film thickness (d) ranging from 41 to 76 nm. The experimental plasmon resonance spectra were reproduced by a calculation that included the broadening effects as follows: (1) the imaginary part of the bulk dielectric constant, (2) the thickness-dependent radiative coupling of the SPP at the metal–air interface to the prism, (3) the lack of conservation of the wavevector parallel to the interface kx(k||) caused by the surface roughness, (4) scanning λ at a fixed θ (changing both energy and kx at the same time) over the SPP dispersion relation. For Au and Ag, the experimental results were in good agreement with the calculated results using the bulk dielectric constants, showing no film thickness dependence of the plasmon resonance energy. A method to extract the true width of the plasmon resonance from raw ATR spectra is proposed and the results are rigorously compared with those expected from the bulk dielectric function given in the literature. For Au and Ag, the width increases with energy, in agreement with that expected from the relaxation of bulk free electrons including the electron–electron interaction, but there is clear evidence of extra broadening, which is more significant for thinner films, possibly due to relaxation pathways intrinsic to plasmons near the interface. For Cu, the visibility of the plasmon resonance critically depends on the evaporation conditions, and low pressures and fast deposition rates are required. Otherwise, scattering from the surface roughness causes considerable broadening of the plasmon resonance, resulting in an apparently fixed resonance energy without clear incident angle dependence. For Cu, the observed plasmon dispersion agrees well with that expected from the bulk dielectric function even with nominal oxidation of the surface, but the widths at long wavelengths are much larger than those theoretically expected.

Simulation of Surface Plasmon Resonance Biosensor Based on Nanoparticle Coreshell in 633 nm

In this research, we developed the modeling and simulated the biosensor based on Surface Plasmon Resonance (SPR) phenomenon which detected the analyte i.e DNA. This SPR biosensor consists four layers where one of thus layers is the composite material. This nanocomposite spherical nanoparticle consisting of a spherical Fe3O4@Au core covered by Au shell, were applied as active material for DNA detection in 633 nm. Here, we present the simulation of detection amplification technique through Attenuated Total Reflection (ATR) spectrum. Here, SPR system using the Kretschmann configuration, whereas the dielectric function determination of composite coreshell nanoparticle using Effective Medium Theory approximation. Finally, the reflectivity calculation was investigated by varied the size of the core and the shell of the coreshell. The refractive index of the prism is 1,723; the refractive index of 40 nm Ag thin film is 0.13455+3,98651i and the refractive index of the composites were variated dependent the size of nanoparticle coreshell. Our results show that by varying the radius of core and shell thickness, the peak of the reflectivity (ATR spectrum) was shifted to the different angle of incident light. From its result, we can conclude that the addition of coreshell in SPR biosensor leads to enhancement the biosensor sensitivity in DNA detection.

Integrative Temporo-Spatial, Mineralogic, Spectroscopic, and Proteomic Analysis of Postnatal Enamel Development in Teeth with Limited Growth.

Tooth amelogenesis is a complex process beginning with enamel organ cell differentiation and enamel matrix secretion, transitioning through changes in ameloblast polarity, cytoskeletal, and matrix organization, that affects crucial biomineralization events such as mineral nucleation, enamel crystal growth, and enamel prism organization. Here we have harvested the enamel organ including the pliable enamel matrix of postnatal first mandibular mouse molars during the first 8 days of tooth enamel development to conduct a step-wise cross-sectional analysis of the changes in the mineral and protein phase. Mineral phase diffraction pattern analysis using single-crystal, powder sample X-ray diffraction analysis indicated conversion of calcium phosphate precursors to partially fluoride substituted hydroxyapatite from postnatal day 4 (4 dpn) onwards. Attenuated total reflectance spectra (ATR) revealed a substantial elevation in phosphate and carbonate incorporation as well as structural reconfiguration between postnatal days 6 and 8. Nanoscale liquid chromatography coupled with tandem mass spectrometry (nanoLC-MS/MS) demonstrated highest protein counts for ECM/cell surface proteins, stress/heat shock proteins, and alkaline phosphatase on postnatal day 2, high counts for ameloblast cytoskeletal proteins such as tubulin β5, tropomyosin, β-actin, and vimentin on postnatal day 4, and elevated levels of cofilin-1, calmodulin, and peptidyl-prolyl cis-trans isomerase on day 6. Western blot analysis of hydrophobic enamel proteins illustrated continuously increasing amelogenin levels from 1 dpn until 8 dpn, while enamelin peaked on days 1 and 2 dpn, and ameloblastin on days 1–5 dpn. In summary, these data document the substantial changes in the enamel matrix protein and mineral phase that take place during postnatal mouse molar amelogenesis from a systems biological perspective, including (i) relatively high levels of matrix protein expression during the early secretory stage on postnatal day 2, (ii) conversion of calcium phosphates to apatite, peak protein folding and stress protein counts, and increased cytoskeletal protein levels such as actin and tubulin on day 4, as well as (iii) secondary structure changes, isomerase activity, highest amelogenin levels, and peak phosphate/carbonate incorporation between postnatal days 6 and 8. Together, this study provides a baseline for a comprehensive understanding of the mineralogic and proteomic events that contribute to the complexity of mammalian tooth enamel development.

Rich hybridized-polarization surface phonon polaritons in hyperbolic metamaterials

We investigated hybridized-polarization surface phonon polaritons (HSPhPs) of transversely truncated a metamaterial (MM) that consists of alternating ionic-crystal and ordinary-dielectric layers. We predicted five HSPhPs in the reststrahlen frequency window of ionic-crystal layers, which belong to five different types, respectively. One is of Dyakonov-like type and another is traditional-like. The other three HSPhPs are of new type. We used a numerical-simulating method of attenuated total reflection (ATR) measurements to examine them. The obtained ATR spectra also demonstrate that they are observable and exhibit their polarization features. These results expand the potential-application space of phononics and photonics in the infrared to the terahertz range.

Infrared spectroscopic study of sulfate-bearing calcite from deep-sea bamboo coral

The powder infrared spectra of a sulfate-bearing calcitic coral sample are recorded at room temperature in attenuated total reflectance (ATR) geometry and at low temperature in transmission geometry. The comparison of ATR spectra recorded with diamond or Ge crystal confirms that the width and the shape of the prominent absorption bands, related to CO 3 groups, are dominantly affected by macroscopic electrostatic interactions. In contrast, the temperature-dependence of the position and width of weak and narrow absorption bands, related to CO 3 or SO 4 groups, can be interpreted in terms of thermal expansion, anharmonic coupling, and local strain fluctuations. The three SO 4 stretching bands display a contrasted thermal behavior, the frequency of one of them increasing with temperature. Based on first-principles calculation, this unusual temperature dependence is traced back to the anisotropy of calcite thermal expansion. These results sustain the previously proposed atomic-scale model of sulfate in calcite and attest to a dominantly structural nature of sulfate in the investigated sample. Accordingly, structurally substituted sulfur in deep-sea calcitic bamboo coral could be used as proxy of seawater sulfate.

A Correction Method for Attenuated Total Reflection-Far Ultraviolet Spectra Via the Use of Charge Transfer to Solvent Band Intensities of Iodide in the Ultraviolet Region.

Attenuated total reflection (ATR) spectra, which are often used in IR analysis, can be transformed into extinction and refraction spectra by Kramers-Kronig transformation (KKT) with Fresnel equations. However, it is often difficult to obtain correct optical indices due to the inherent instrumental functions. This paper proposes a simple practical method for correction of KKT with two parameters, which include all the effects of the instrumental function. In order to obtain the parameters of the instrumental function, absorption ratios of charge transfer to solvent (CTTS) transitions of aqueous iodide ions observed at 195 nm and 230 nm were used as a standard. The absorption indices calculated from the ATR spectra with the parameters correspond reasonably well to those given by the transmittance spectra not only in the UV region but also in the far-ultraviolet (FUV, 120-200 nm) region. By applying the corrected KKT to the ATR-FUV spectra of aqueous potassium halide solutions in the range of 0-2 M, correct features of the absorption spectra of KCl and KBr, whose CTTS bands are thought to be observed in FUV region, were confirmed. It is possible to use the parameters representing the instrument function as long as the instrument is not changed.

In Operando Measurement of Lithium Polysulfides in Lithium-Sulfur Batteries Using Attenuated Total Reflection Spectroscopy

Li-S cells promise a theoretical capacity much greater than existing Li-ion technology, but the problem of polysulfide shuttling, which leads to self-discharge and loss of active material, remains one of the largest barriers to commercial adoption. We report a spectro-electrochemical cell designed for in operando measurements of the order and concentration of lithium polysulfides (Li2Sn, where n is the order). The design is a major improvement on existing cells, which typically require significant modifications from commercial cell geometries and require low charge/discharge rates during operation. The optically accessible Li-S cell resembles a CR2032 battery, and is constructed on a metallic disc with a diamond crystal at its center. Attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy is used for in-operando measurements of soluble polysulfides, which are present in the electrolyte-saturated pores of the sulfur electrode. The diagnostic was calibrated using ATR spectra of lithium polysulfide standards, prepared from direct reaction of lithium sulfide and sulfur. The order and concentration of lithium polysulfides in a sample are determined from the position and area of a characteristic IR absorption band. The diagnostic routine can measure polysulfide order and concentration to within 5% and 0.1 M, respectively. Polysulfides smaller than Li2S4 are insoluble and are not present in ATR spectra. Li-S cells were discharged at C rates up to 2 with simultaneous measurement of lithium polysulfide order and concentration. The obtained voltage profiles are consistent with those reported in literature. During discharge, polysulfide order steadily decreases while polysulfide concentration initially increases followed by a steady decrease. The initial increase in concentration is attributed to: i) reduction from elemental sulfur to Li2S8, and ii) reduction of Li2S8 to smaller polysulfides. The subsequent decrease in concentration is attributed to formation of insoluble polysulfides, which are not measured by the diagnostic. Charging the cell follows the opposite trend, except that elemental sulfur is not recovered.

Diversiform hybrid-polarization surface plasmon polaritons in a dielectric–metal metamaterial

Hybrid-polarization surface plasmon polaritons (HSPPs) at the interface between an isotropic medium and a one-dimensional metal–dielectric metamaterial (MM) were discussed, where the metal-layer permittivity was described with the improved Drude model. From the obtained dispersion equations, we predicated five types of HSPPs. One type is the Dyakonov-like surface polariton and another type is the tradition-like surface polarton. The others are new types of HSPPs. We establish a numerical simulation method of the attenuated total reflection (ATR) measurement to examine these HSPPs. The results from the ATR spectra are consistent with those from the dispersion equations and indicate the different polarization features of these HSPPs. The numerical results also demonstrate that the observation of each type of HSPPs requires different conditions dictated by the material parameters and the polarization direction of incident light used in the ATR spectra. These results may further widen the space of potential applications of surface plasmon polaritons.