Conventional Spectroscopic Method Research Articles

Maturity characterization and formation mechanisms of nano-scale anisotropic pyrobitumen based on atomic force microscopy (AFM)

Highly evolved pyrobitumen is an important and realistic object for maturity characterization of ancient and deeply buried organic matter, but measurement of its reflectance is challenging due to its strong optical anisotropy and nano-scale relief. Here we conducted a case study in the Sinian (Ediacaran) Dengying Formation of the Sichuan Basin, China. High-resolution, three-dimensional, morphological imaging by atomic force microscopy (AFM), laser Raman (LRM) spectroscopy, and reflectance studies were conducted on the reservoir pyrobitumen. Our results show that Young’s modulus and adhesion, which are mechanical maturity parameter, provides effective characterization of maturity. The increase in Young’s modulus of pyrobitumen lags that of the vitrinite, given that pyrobitumen is formed by oil cracking and is more hydrogen-rich than vitrinite. A quantitative relationship between Young’s modulus, adhesion and reflectance in bright and dark areas of pyrobitumen was established, which can be used for maturity characterization. The changes in Young’s modulus of the pyrobitumen is related to the condensation of organic matter and directional arrangement of microcrystals. Young’s modulus of organic matter is a robust mechanical maturity index at high organic matter maturity (Ro > 2.0 %), but it is important to pay attention to the influence of anisotropy. Compared to Young’s modulus, adhesion is less affected by anisotropy. The nano-mechanics such as Young’s modulus and adhesion will be new maturity indicator in addition to conventional optical and spectroscopic method. The nano-mechanical properties of organic matter are expected to be applied to maturity indicators and macerals classification in the field of organic petrology in the further research.

Development and Testing of an LED-Based Near-Infrared Sensor for Human Kidney Tumor Diagnostics.

Optical spectroscopy is increasingly used for cancer diagnostics. Tumor detection feasibility in human kidney samples using mid- and near-infrared (NIR) spectroscopy, fluorescence spectroscopy, and Raman spectroscopy has been reported (Artyushenko et al., Spectral fiber sensors for cancer diagnostics in vitro. In Proceedings of the European Conference on Biomedical Optics, Munich, Germany, 21–25 June 2015). In the present work, a simplification of the NIR spectroscopic analysis for cancer diagnostics was studied. The conventional high-resolution NIR spectroscopic method of kidney tumor diagnostics was replaced by a compact optical sensing device constructively represented by a set of four light-emitting diodes (LEDs) at selected wavelengths and one detecting photodiode. Two sensor prototypes were tested using 14 in vitro clinical samples of 7 different patients. Statistical data evaluation using principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) confirmed the general applicability of the LED-based sensing approach to kidney tumor detection. An additional validation of the results was performed by means of sample permutation.

Highly Sensitive Multiresponsive Chemosensor for Selective Detection of Hg2+ in Natural Water and Different Monitoring Environments

A new chemosensor RF1 that combines a ferrocene unit and a rhodamine block via the linkage of a carbohydrazone binding unit was designed and prepared for the highly selective detection of Hg (2+) in natural water. This chemosensor displays great brightness and fluorescence enhancement following Hg (2+) coordination within the limit of detection for Hg (2+) at 1 parts per billion (ppb). The fluorescence intensities are nearly proportional to the amount of Hg (2+) at the ppb level. It is capable of distinguishing between the safe and the toxic levels of inorganic mercury in drinking water. Hg (2+)-binding also arouses the absorption of the rhodamine moiety in RF1 significantly with the chromogenic detection limit for Hg (2+) at 50 ppb. The conventional UV-vis spectroscopic method thus has the potential to provide the critical information about the mercury hazard assessment for industrial wastewater discharging. The obvious and characteristic color change of the titration solution from colorless to pink upon the addition of Hg (2+) demonstrates that RF1 can be used for "naked-eye" detection of Hg (2+) in water. The Hg (2+) complexation also causes a significant shift of the redox potential about the ferrocene/ferrocenium couple. The electrochemical responses provide the possibility to quantitative analysis of Hg (2+) at the parts per million (ppm) level. Preliminary investigations in natural water samples including seawater and freshwater indicate that RF1 offers a direct and immediate Hg (2+) detection in complex media, pointing out its potential utility in environment monitoring and assessment. The responses of RF1 are Hg (2+) specific, and the chemosensor exhibits high selectivity toward Hg (2+) over other Group 12 metals, alkali, alkaline earth metals, and most of the divalent first-row transition metals. The RF1-Hg (2+) complex is successfully isolated and the Hg (2+)-binding is reversible. The crystal structure and spectral properties of its congener RF2 that contains one ferrocene group and two rhodamine 6G moieties were also investigated for a comparison.

A kinetic study of oxidation of β-cyclodextrin by permanganate in aqueous media

Kinetic data for the permanganate—β-cyclodextrin redox system are reported for the first time. Conventional spectroscopic method was used to monitor the progress of the reaction. The reaction is first order in both [MnO 4 −] and [β-cyclodextrin]. The [H +] markedly increase the oxidation rate. Formation of an intermediate (Mn(IV)) observed during the course of reaction at 420 nm. Mn(III) is also formed in a rapid step by reaction of β-cyclodextrin and Mn(IV). Increase in [F −] causes the rate to decrease. One of the primary OH group of α- d-glucopyranose unit of β-cyclodextrin is responsible for the oxidation. An autocatalytic effect has been observed due to Mn(II) ions formed as a product of the reaction. The rate of oxidation of d-glucose is higher in comparison to β-cyclodextrin for the same concentration. Reduction of mercuric chloride indicates free radical mechanism operates during the course of reaction. The energy, enthalpy and entropy of activation have been calculated and mechanism agreement with the observation is suggested.

On the Spectroscopic Determination of Atmospheric Parameters and O/Fe Abundances of RR Lyrae Stars

Abstract In order to study how the conventional spectroscopic method based on the equivalent widths of the Fe I and Fe II lines effectively applies to determining the atmospheric parameters ($T_{\mathrm{eff}}, \log g, v_{\mathrm{t}}, [\mathrm{Fe/H}]$) of RR Lyrae variables and how accurately the abundances can be established from such constructed model atmospheres, we analyzed 15 high-dispersion spectrograms of RR Lyr, DX Del, DH Peg, and VY Ser taken at several different phases by using the HDS spectrograph of the Subaru Telescope, and examined the consistency of the resulting phase-to-phase abundances. Taking oxygen as the target element along with Fe, we determined its non-LTE abundance from the O I 6155–8 and 7771–5 triplets. It was found that consistent abundances were obtained for O as well as Fe to a level of $\sim 0.1 \,\mathrm{dex}$, irrespective of the pulsation phase, except for the special near-maximum high-temperature phase. This suggests that classical model atmospheres are reliably applicable to abundance determinations of RR Lyrae stars in most cases. While the oxygen abundances derived from O I 7771–5 well correlate with those from O I 6155–8, the former tends to be systematically larger by 0.1–0.2 dex than the latter, which may be interpreted as being due to the depth-dependence of the microturbulence increasing with height; i.e., the $v_{\mathrm{t}}$ value derived from deep-forming Fe lines of weak/medium-strength may not be simply applied to higher forming strong lines, such as O I 7771–5.

Electrochemical determination of γ-glutamyl transpeptidase activity and its application to a miniaturized analysis system

A novel method to determine the activity of gamma-glutamyl transpeptidase (gamma-GTP) was developed. gamma-l-glutamyl-l-glutamate and glycyl-glycine were used as the substrates for gamma-GTP. l-glutamate produced by the enzymatic reaction was measured with an amperometric l-glutamate sensor. Following the mixing of the substrate solution and a sample solution, the current generated on the l-glutamate sensor continued to increase at a constant rate. The method was used to construct a miniaturized analysis system for the determination of gamma-GTP activity. The system consisted of the l-glutamate sensor formed on a glass substrate and a polydimethylsiloxane (PDMS) flow channel. Since the l-glutamate concentration in the solution increased as the solution was mobilized through the flow channel, a constant current increase was observed. The relation between the slope of the response curve and the activity of gamma-GTP was linear between 35 U l(-1) and 659 U l(-1). The rate analysis in the micro flow channel minimized the influence of interferents. The reproducibility of the output of the micro system was found to be good with a relative standard deviation (R.S.D.) of 5.6% at 659 U l(-1). The activities of gamma-GTP in human serum samples were also determined and compared with values obtained with a conventional spectroscopic method. The values obtained by the two methods were consistent with a correlation coefficient of 0.953.

Stellar Parameters and Photospheric Abundances of Late-G Giants: Properties of the Targets of the Okayama Planet Search Program

Abstract Towards clarifying the properties of late-G giants, for which we are currently conducting a planet-search project at Okayama Astrophysical Observatory, an extensive spectroscopic study has been performed for our first target sample of fifty-seven G6–G9 III stars, in order to establish the atmospheric parameters ($T_{\mathrm{eff}}, \log g, v_\mathrm{t}$, and $\mathrm{[Fe/H]}$), the stellar mass along with the evolutionary status, and the photospheric abundances of various elements. It was confirmed that the conventional spectroscopic method of parameter determination using Fe I / II lines with the assumption of LTE works successfully for these evolved stars. We determined the abundances (relative to the Sun) of 19 elements, and examined how their $\mathrm{[X/Fe]}$ ratios behave themselves with the run of $\mathrm{[Fe/H]}$. While the trends appear to be similar to those exhibited by disk dwarfs for a number of elements, some elements (C, O, Na) showed appreciable anomalies, which may be interpreted as being due to a dredge-up of nuclear-processed material. Since the $\mathrm{[Fe/H]}$ values of these stars tend to be somewhat biased towards a subsolar regime, some mechanism of slightly reducing the metallicity might be suspected.

Visual and Spectroscopic Demonstration of Intercrystalline Migration and Resultant Photochemical Reactions of Aromatic Molecules Adsorbed in Zeolites

We applied a fluorescence microscopy method to investigate the intercrystalline migration of aromatic molecules adsorbed in faujasite zeolites aiming at observing directly the particle-to-particle processes dependent both on interparticle distance and on the time scale of the observation. Photophysical processes such as intersystem crossing and energy transfer and photochemical reactions such as charge transfer (CT) and triplet−triplet energy transfer between guest species incorporated in the zeolites were exploited as indicator reactions to yield a luminescence color characteristic of individual zeolite particles. Two types of migration mechanisms were observed: a through-space diffusional transfer mode between separated zeolite crystals and a molecular injection process from a loaded crystal to another unloaded crystal, both in contact. A preferential direction of guest migration was found to exist for a few cases: for instance, aromatics such as phenanthrene and chrysene migrate from sodium form of zeolite X (Na+−X) to thallium-exchanged zeolite X (Tl+−X). On the other hand, the migration-assisted formation of CT complexes between electron-donating arenes such as phenanthrene and chrysene, and electron-accepting 1,2,4,5-tetracyanobenzene, both incorporated into separate zeolite Na+−X crystals, takes place as a result of the migration of the donors. Comparison of this technique with a conventional fluorescence spectroscopic method for zeolite powders revealed that the microscopy method is advantageous because it is difficult for the spectroscopic method to detect the evolution of new emission bands in strongly emitting matrix. The fluorescence microscopy method utilizing photochemistry in zeolites was found to be a powerful technique for the qualitative investigation of the intercrystalline migration in zeolites.

Determination of intracellular glutathione and thiols by high performance liquid chromatography with a gold electrode at the femtomole level: comparison with a spectroscopic assay

Glutathione (GSH) is an important thiol, which has multiple functions in human metabolism, including the detoxification of xenobiotics, radioprotection and antioxidant defense. Here we provide a sensitive and specific method to quantify intracellular GSH and other thiols using an electrochemical detector coupled to a high performance liquid chromatograph (HPLC-ECD). This HPLC-ECD system includes a specially devised gold electrode with a large surface area and a thin gasket to provide an extremely high sensitivity to thiols. The standard curve for GSH showed a good linear relationship at low femtomole levels ( r=0.970). We could simultaneously detect GSH, cysteine, N-acetylcysteine, γ-glutamyl-cysteine and cysteinyl-glycine by this method. We compared the specificity and sensitivity of this method with those of the conventional spectroscopic method by measuring the amounts of GSH in HL-60 cell extracts. Although the values obtained from these methods were closely correlated ( r=0.984), the electrochemical method was much more specific for GSH. This method could detect 2 fmol of GSH and was 6 orders and 2–3 orders of magnitude more sensitive than the spectroscopic method and previous methods using HPLC, respectively. As an example of the application of this method, we demonstrated that the time-dependent alteration in intracellular GSH and cysteine levels could be easily measured using buthionine sulfoximine, an inhibitor of GSH synthesis. On the basis of these results, the advantage of this electrochemical method is extremely sensitive and specific to detect femtomole levels of GSH and other various thiols.

Guest inclusion properties of calix[6]arene-based unimolecular cage compounds. On their high Cs + and Ag + selectivity and very slow metal exchange rates

The reaction of 1,3,5-tri- O-alkylated calix[6]arenes with 1,3,5-tris(bromomethyl)benzene yielded capped calix[6]arenes ( 2 with tert-butyl groups on the upper rim and 3 without tert-butyl groups) in unexpectedly high yields (80 – 91%). Combined studies of 2 and 3 by MM3 computation, X-ray analysis, and 1H NMR spectroscopy established that these calix[6]arenes feature a unique structure consisting of alternately-arranged three flattened mesitylene-linked phenyl units and three stand-up anisole units. Particularly, compound 2 possesses a closed ionophoric cavity: the upper hemisphere is closed by three tert-butyl groups of anisole units and the lower hemisphere is closed by a mesitylene cap and three anisole methoxy groups. The 1H NMR spectrum was scarcely changed at wide temperature range (30 ∼ 130°C), indicating that the structure is extremely rigidified. Both solvent extraction and spectroscopic studies established that this cavity shows the high selectivity toward Cs + among alkali metal cations, the high affinity with Ag +, and the moderate affinity with RNH 3 +. Very surprisingly, the association-dissociation processes for 2 and cesium picrate was so slow that the rate could be followed by a conventional spectroscopic method . The thermodynamic parameters determined by kinetic studies disclosed that the major driving-force for Cs + inclusion is the entropy term based on the desolvation.

Kinetic Study of the Shape Change of Human Erythrocyte Induced by Sodium Alkyl Sulfates

Abstract In order to clarify the mechanism of the shape change of human erythrocytes induced by anionic surfactants, kinetic experiments were performed using the stopped-flow technique and the conventional spectroscopic method. In the time range from 0.1 s to a few dozen minutes, four kinetic processes were observed. In the dead time of the stopped-flow apparatus (within 10 milli seconds), a decrease in the intensity of the transmitting light was observed. Based on an analysis of the dependence of the relaxation time of each process on the surfactant concentration for various reaction schemes, we propose a most plausible reaction model that includes four kinds of binding processes of the surfactant and three intramolecular processes. In the present paper, based on this model, we discuss the detailed mechanism of the shape change of the erythrocytes.

Thermodynamic studies of slow metal exchange processes in ionophoric calix[n]arenes with a capsule-like closed cavity

It was found that in a triply-capped calix[6]arene ( 1) and doubly-bridged calix[8]arene ( 2a and 2b) with a closed ionophoric cavity the Cs + complexation occurs very slowly in a human time-scale and can be followed by a conventional spectroscopic method. The unusual behavior has enabled us to determine their kinetic activation parameters for both the forward and the reverse reaction. The results established that being different from the concept believed so far, the Cs + complexation is heavily governed by the entropy term but not by the enthalpy term.

Photochromic Dispironaphthoxazine Polyethers: Synthesis and Their Cation Binding Capability

Abstract Dispironaphthoxazines incorporating polyether chain were synthesized. Photochromic effects on cation binding capability of the molecules were investigated. Due to the photochromic spironaphthoxazine unit in these compounds, complexation with metal cations is easily identified by the conventional spectroscopic method. Cation binding ability of dispironaphthoxazine with tetraethylene glycol unit is enhanced under the UV light irradiation. This type of photochromic compound may work as a photoresponsive ionophore.

Surface charge spectroscopy and its applications

Surface Charge Spectroscopy (SCS) is a surface sensitive technique for measuring potential distributions across an ultrathin (<100Å) insulator/semiconductor structure. Although the applicability of the technique is rather narrowly confined to such a specific sample structure, SCS bears considerable industrial significance because insulator/semiconductor structures are the most commonly used functional elements in microelectronics, and because gate insulators used in the industry are indeed getting to a nanometer thickness scale. The basic SCS concept relies on the measurements of the potential energies of electronic states using the conventional photoemission spectroscopic method, energy data which bear the information of the electrical potential gradient across the probed surface region. Surface sensitivity of SCS is thus contained in the framework of photoemission spectroscopy. Unlike conventional photoemission studies, SCS always measures the potential gradients corresponding to a specific surface potential. In fact, its analytical power is only shown when the surface potential of a sample can be controlled, and coincidentally an insulator/semiconductor device structure in microelectronics is only functional when the potential gradient extending into the semiconductor region can be changed effectively by the surface potential of the insulator. When SCS data are examined beyond the simple space-charge model commonly employed by electrical characterisation techniques like capacitance-voltage measurements, they can give information other than the relationship between the insulator surface potential and semiconductor surface potential (and thus interface state distributions across the bandgap of the semiconductor). Rather, they also provide unique information on the depth distributions of various types of fixed charges in the sample structure at an atomic level, and on the insulator breakdown mechanisms.

Inclusion of non-bonded interactions in calculations of vibrational frequencies

The consequences of including non-bonded interactions in the calculation of vibrational frequencies are examined by comparing the results of the consistent force field method (CFF)and a conventional spectroscopic force field calculation method. Sample calculations are given, using ethane as a test case. It is shown that the CFF method is more practical for the calculation of non-bonded interaction parameters for large molecules, provided that the molecular potential energy is first minimized.

Laser-emission cross sections of MeNdP4O12 (Me=Li, Na, K) crystals

Emission cross sections of a Nd stoichiometric laser crystal LiNdP4O12 at 1.048 μm were measured by a direct absorption method and the conventional spectroscopic method. The largest effective-emission cross section was determined to be σbeff= (1.7±0.2) ×10−19 cm2 by these two methods. Emission cross sections of NaNdP4O12, KNdP4O12 and LiNd0.1Ln0.9P4O12 (Ln=Gd, La) were also determined by the conventional spectroscopic method. The radiative lifetime of LiNdP4O12 was calculated from the fluorescence spectra and the quantum efficiency of LiNdP4O12 was found to be 0.34.