Quantitative analysis of ethanol–methanol–water ternary solutions using Raman spectroscopy

Raman spectroscopy was used for rapid in-situ measurement of alcohols in ethanol-methanol-water ternary systems. Mass fractions of the individual components were determined using calibration curves for binary systems of ethanol-water, methanol-water, and ethanol-methanol. Calibration curves were constructed by calculating the ratio of the Raman peak intensity of a component and that of an external standard (acetonitrile). Assuming additivity of the spectra, simultaneous equations were written, and mass fractions of ethanol, methanol, and water in the ternary solutions were determined by solving the system of equations through calculating an inverse matrix. The relative errors between the mass fractions obtained from the Raman spectra and those obtained from mass measurements were <0.6%.     

A novel method for quantification of ethanol and methanol in distilled alcoholic beverages using Raman spectroscopy

In this study, direct quantification of ethanol and methanol in distilled alcoholic beverages using Raman spectroscopy was performed. Raman spectra of varying ethanol–methanol mixtures were obtained, baseline corrections were made, and the data were normalized using Raman scattering intensity of an internal standard (acetonitrile, 921 cm^–1). Then, calibration graphs were produced for ethanol and methanol concentrations in the ranges of 0–7 M and 0–10 M, respectively. Accurate R² values of the calibration graphs proved the notable linear correlations (0.998 for ethanol and 0.998 for methanol). The method was validated based on linearity, sensitivity, intraday and interday repeatability, and recovery tests. The limit of detection and limit of quantification values of the validated method were determined for ethanol concentration as 1.2 and 3.7 mM, and for methanol concentration as 3.4 and 10.3 mM, respectively. The ability of the developed method to detect ethanol and methanol concentrations in real samples was also investigated. The results of the developed method were compared with the experimental results from traditional method and high correlation value (R² = 0.926) was obtained. Besides being sensitive and cheap, the developed method is rapid with the analysis time of less than 30 s. Furthermore, it eliminates labor‐consuming operations, chromatographic separation, and measurement error due to the high number of experiment steps in the standard method. Copyright © 2012 John Wiley & Sons, Ltd.     

Quantitative detection of adulterated olive oil by Raman spectroscopy and chemometrics

Commercially available extra virgin olive oils are often adulterated with some other cheaper edible oils with similar chemical compositions. A set of extra virgin olive oil samples adulterated with soybean oil, corn oil and sunflower seed oil were characterized by Raman spectra in the region 1000–1800 cm⁻¹. Based on the intensity of the Raman spectra with vibrational bands normalized by the band at 1441 cm⁻¹ (CH₂), external standard method (ESM) was employed for the quantitative analysis, which was compared with the results achieved by support vector machine (SVM) methods. By plotting the adulterant content of extra virgin olive oil versus its corresponding band intensity in the Raman spectrum at 1265 cm⁻¹, the calibration curve was obtained. Coefficient of determination (R²) of each curve was 0.9956, 0.9915 and 0.9905 for extra virgin olive oil samples adulterated with soybean oil, corn oil and sunflower seed oil, respectively. The mean absolute relative errors were calculated as 7.41, 7.78 and 9.45%, respectively, with ESM, while they were 5.10, 6.96 and 4.55, in the SVM model, respectively. The prediction accuracy shows that the ESM based on Raman spectroscopy is a promising technique for the authentication of extra virgin olive oil. The method also has the advantages of simplicity, time savings and non‐requirement of sample preprocessing; especially, a portable Raman system is suitable for on‐site testing and quality control in field applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Higher order field equations II; Limit properties of green's functions

In a previous paper wave propagation was studied according to a sixth-order partial differential equation involving a complex mass M. The corresponding Yang-Feldman integral equations (indicated as SM-YF-equations), were formulated using modified Green's functions G^M_R(x) and G^M_A(x), which then incorporate the partial differential equation together with certain boundary conditions. In this paper certain limit properties of these modified Green's functions are derived: (a) It is shown that for |M| → ∞ the Green's functions G^M_R(x) and G^M_A(x) approach the Green's functions Δ_R(x) and Δ_A(x) of the corresponding KG-equation (Klein-Gordon equation). (b) It is further shown that the asymptotic behaviour of G^M_A(x) and G^M_A(x) is the same as of Δ_R(x) and Δ_A(x) - and also the same as for D_R(x) and D_A(x) for t→ ± ∞, where D_R and D_A are the Green n's functions for the KG-equation with mass zero. It is essential to take limits in the sense of distribution theory in both cases (a) and (b). The property (b) indicates that the wave propagation properties of the SM-YF-equations, the KG-equation with finite mass and the KG-equation with mass zero are closely related in an asymptotic sense.     

Polarized-neutron scattering in aqueous solutions of fullerenols in a magnetic field

The aqueous solutions of mixtures (T = 25°C) of paramagnetic Gd@C₈₂(OH) _x and diamagnetic C₈₂(OH) _x fullerenols, where x ～ 30, are studied via small-angle polarized-neutron scattering under the conditions of transition from diluted to concentrated systems whose solubility threshold is close to that of fullerenols. When the induction B of an external field varies from 0.001 to 1.0 T, the molecular correlation radius of solutions is R _C ～ 15–20 nm and the aggregation number reaches ～5 × 10⁴ with increasing fullerenol content (C = 0.04?2.0 wt %). Such changes are coupled with both paramagnetic Gd@C₈₂(OH) _x molecules and interactions between the induced diamagnetic moments of fullerenols introduced into aggregates.     

Solid-state NMR study of bioactive binary borosilicate glasses

A series of binary borosilicate glasses prepared by the sol-gel method are shown to be bioactive. Tetraethyl orthosilicate (TEOS) and trimethylborate (TMB) in acidic medium are used to prepare xB₂O₃·(1−x)SiO₂ glass systems for x=0.045-0.167. The formation of a layer of apatite-like mineral on the glass surface becomes apparent after soaking in simulated body fluid for 48 h. We have measured the ¹¹B-¹¹B homonuclear second moments of the borosilicate glasses and inferred that no macroscopic phase separation occurred in our glasses. The ¹¹B chemical shift data also show that the formation of clustered boroxol rings is negligible in our glass system. Although the bioactivity of our borosilicate glasses is less than that of CaO-SiO₂ sol-gel glasses, these simple binary systems could be taken as reference glass systems for the search of new bioactive borosilicate glasses.     

Microstructure and crystallization properties of TeO2?PbF2 glasses

The microstructures of (1 − x)(TeO₂)–xPbF₂, (x = 0.1, 0.15, and 0.25 mol) glasses were investigated by using the Raman spectroscopic technique. The effect of compositions on the TeO₂ glass networks and the intensity ratios of the deconvoluted Raman peaks were determined. The results confirm that the addition of modifiers to the glass network former shifts the Raman intensity and the peak wavenumber values for each band in the 167–165, 652–645, and 747–755 cm⁻¹ wavenumber regions. The structural evaluation was recognized from the Raman spectra, with the structural units described as [TeO₃₊₁] polyhedra, [TeO₃] trigonal pyramids, and [TeO₄] trigonal bipyramids for this binary glass system. Heat‐treatment of the samples shows that the metastable crystalline phase of TeO₂ known as γ‐TeO₂ is formed only when the modifier content is 10 mol% in the glass matrix. Transparent glass properties were not realized when the TeO₂ amount was decreased to less than 10 mol% content. Copyright © 2008 John Wiley & Sons, Ltd.     

Electronic Raman scattering from inter-valence band transition in photo-excited GaP and GaAs1−xPx crystals

Raman scattering from photo-created free carriers in undoped GaP and GaAs_1?xP_x (x = 0.85, 0.73 and 0.66) under high excitation intensity has been studied. Two new Raman bands have been observed and assigned to electronic transitions from the split-off hole band to the heavy hole band and from the light hole band to the heavy hole band. The spin-orbit splitting energies in these crystals have been determined from the analysis of observed Raman bands, and compared with other experimental values.     

Quantitative analysis of chromate (CrVI) by normal Raman spectroscopy and surface-enhanced Raman spectroscopy using poly(diallyldimethylammonium) chloride-capped gold nanoparticles

Chromate (Cr^VI) has emerged as a widespread environmental contaminant found in groundwater and surface water, and there is a great need for rapid detection and monitoring of this contaminant. Normal Raman scattering (NRS) spectroscopy with a detection limit of Cr^VI at concentrations of 0.2 g/L was attached. And surface-enhanced Raman scattering (SERS) spectroscopy technique was found to be capable of detecting Cr^VI at concentrations as low as 2.5 mg/L using poly(diallyldimethylammonium) chloride modified gold nanoparticles (PDDA-AuNPs) as a substrate. The SERS substrate was successfully fabricated by combining the selfassembly technique with a heat-treatment-based strategy using poly(diallyldimethylammonium) chloride (PDDA) as the reducing and stabilizing agents. With the 520 cm^?1 band of silicon as internal standard, band intensity ratios of Cr^VI to silicon, that is I ₉₀₂/I ₅₂₀, were found to have a quantitative relationship with a large concentration range of Cr^VI from 0.2 to 20.0 g/L for NRS (R ² = 0.994) and from 2.5 to 25.0 mg/L for SERS (R ² = 0.980), respectively. Besides, the SERS methodology was reproducible, and susceptible to the interference of pH value. The optimum pH for Cr^VI detection by SERS was 3.38. The application of NRS and SERS showed high practical potential for rapid screening and routine analysis of Cr^VI in environmental samples.     

Raman scattering in brominated (SN)x crystals

Detailed Raman scattering data on brominated (SN)_x crystals ranging in composition from (SNBr_0.27)_x to (SNBr_0.55)_x, and preliminary Raman data on [SN(ICI)_0.125]_x are discussed. The investigation involved a study under various conditions of temperature, pressure and levels of bromination, of the two primary Raman lines at 154 and 230 cm^-1 in brominated (SN)_x, which are polarized along the polymer axis direction. The analysis of the data is consistent with a model in which bromine enters the interfibrillar regions as Br^-₃ and the (SN)_x lattice as Br₂. Infrared data is also presented showing an appreciable decrease in intensity of the SN modes at 995 and 670 cm^-1 on bromination.     

Isotope effect in resonant Raman scattering and induced IR spectra of trans-polyacetylene

We present a full explanation of the isotope effect in resonant Raman scattering, doping induced, and photo-induced IR-active vibrations of previously reported data in trans-(CH)_x, (¹³CH)_x and (CD)_x. The interpretation is given in terms of Raman scattering from amplitude modes of the dimerized chains and absorption by charged induced IR-active modes. It is shown that the bare phonon frequencies are properly modified by the isotope mass whereas the observed frequencies are derived by the dressed phonon propagator, and therefore do not follow the usual mass rule.     

NMR study of the self-induced vortex in (Ce1−xGdx)Ru2

NMR measurement of ¹⁵⁷Gd has been performed in zero external field in (Ce_1?xGd_x)Ru₂ for x = 0.100and 0.119 at low temperature down to 25 mK. Zero field NMR is observed with large enhancements both of H₁ and the intensity of the signal that are characteristic in ferromagnet. T₁T increases rapidly with decreasing temperature, which is attributed to the appearance of the superconducting energy gap whose magnitude is estimated to be 0.066kT_Cforx = 0.100. The NMR intensity in the superconducting state decreases not so drastically as expected in the perfect Meissner state. These results are qualitatively the same as reported previously for x ≥ 0.105 and T ≥ 60 mK. The results suggest that the system is in the state of self-induced vortices predicted theoretically.     

Resonant Raman scattering of polymeric sulfur nitride modified by iodine

Resonance Raman spectra of (SNI_y)_x crystals have been measured at 150 K. The energies of the principal Raman lines of the chromophore (109 and 154 cm^?1) and their intensity behaviour with exciting laser frequency are consistent with the formation of a charge-transfer complex in which iodine enters the interfiber regions of the (SN)_x lattice as I₅^- or I₃^- linked to distorted I₂ units. This structural model is supported by comparison of these Raman data with the excitation profiles of the chromophoric group in starch-iodine and α-cyclodextrine-iodine complexes. Possible mechanisms for the conductivity increase on the basis of the proposed charge transfer model are also discussed.     

LIOUVILLIAN AND ANALYTIC FIRST INTEGRALS FOR THE BRUSSELATOR SYSTEM

We characterize the Liouvillian and analytic first integrals for the polynomial differential systems of the form x′ = a - (b + 1)x + x²y, y′ = bx - x²y, with a, b ∈ ?, called the Brusselator differential systems.     

Chemical composition of matrix-embedded ternary II–VI nanocrystals derived from first- and second-order Raman spectra

A one- and multiphonon Raman scattering study is performed for an extensive set of CdS_1–xSe_x, Cd_1–yZn_yS, Cd_1–yZn_ySe, and CdSe_1–xTe_x nanocrystals to investigate the applicability of first- and second-order Raman spectra for the determination of the matrix-embedded ternary nanocrystal composition. For one-mode ternary systems both the LO and 2LO phonon frequencies in the Raman spectra are shown to be a good measure of the nanocrystal composition. For two-mode systems, the approaches based on the difference of the LO phonon frequencies (first-order Raman spectra) or double LO overtone and combination tone frequencies (second-order Raman spectra) as well as on the LO phonon band intensity ratios are analysed. The weak electron–phonon coupling in the II–VI nanocrystals and the polaron constant values for the nanocrystal sublattices are discussed.     

K0 production in e+e− annihilations at 30 GeV center of mass energy

Inclusive K⁰-production has been measured in e⁺e^- annihilation at a center of mass energy of about W = 30 GeV. The ratio of K⁰ + K⁰ production to μ⁺μ^- production is R_K0 = 5.6 ± 1.1 (statist. error) ± 0.8 (system.error) This value is about a factor of three higher than R_K0 at W = 7 GeV. The cross sections (s/β) dσ/dx is consistent with a scaling behaviour.     

A generalization of Wigner's R-matrix method

A generalization of the Wigner's non-relativistic R-matrix theory of scattering by a central potential field is proposed. The idea is to use an R-matrix expansion basis generated by a Sturm-Liouville problem with an eigenparameter included both in a differential equation and in a boundary condition (in the standard theory an R-matrix basis is obtained by solving an eigenvalue problem with fixed boundary conditions). A partial fraction expansion of an R^(η)-matrix introduced is derived and shown to converge faster than a partial fraction expansion of Wigner's R-matrix used in the standard theory.     

EPR study of clusters of rare-earth ions in mixed fluoride crystals

The EPR spectra of the (BaF₂)_{1 ? x} (CeF₃) _x system are studied for the concentrations x = 0, 0.001, 0.002, 0.005, 0.01, and 0.02. The appearance of new tetragonal centers is detected beginning from x = 0.002, the intensity of these centers being maximal at x = 0.01. The (CaF₂)_{1 ? x ? y} (CeF₃) _x (YF₃) _y double solutions with x = 0.001 and y from 0 to 0.02 are also studied. In addition to the ordinary tetragonal center, beginning from y = 0.001, a new tetragonal center appears with the same structure as in the previously studied mixed crystals based on BaF₂—namely, the Ce³⁺-□-R³⁺ chain elongated along the fourfold axis substitutes the Ca²⁺-Ca²⁺-Ca²⁺ and Ba²⁺-Ba²⁺-Ba²⁺ chains in regular CaF₂ and BaF₂ crystals (□ is the cation vacancy, and R³⁺ is the Ce³⁺, La³⁺, or Y³⁺ trivalent ion).     

正偏离Bragg定律的二元化合物靶中离子射程参数研究

研究了正偏离Bragg定律,即计算S_e(E)值高于实测S_e(E)的二元系化合物靶的离子射程特性。文中应用“regular”观点引入了“双原子模型”,在二元化合物靶的射程计算中,不仅考虑相同“原子对”对离子的阻止本领S₁₁(E),S₂₂(E),而且考虑不同“原子对”对离子的阻止本领S₁₂(E),S₂₁(E)。文中还应用Berthelot关系,使S₁₂(E)=S₂₁(E)=(S₁₁(E)·S₂₂(E))^1/2,则二元系靶的阻止本领及总的射程为NS(E)=1/2[(N₁S₁₁(E))^1/2+(N₂S₂₂(E)^1/2)]², R=4/a[x-A₁(arctg(2x+f)/△^1/2-arctg(f/△^1/2))-B₁(ln(x+g)²/g²·e/(x²+fx+e)) -b/2 ln(x²+fx+e/e)。这里X=E^1/2,E为离子注入能量,所有其它常数是与离子和靶的质量、原子序数有关的常数。结合文献[1]提出的R与R_p,R_p与△R_p的关系式,可计算得正偏离系统的投影射程R_p及其偏差量△R_p。并对各关系式的物理意义作了阐明。 关键词：     

Effect of Dy substitution on structural,magnetic and optical properties of BiFeO3 ceramics

Bi_1−xDy_xFeO₃ (x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.12) ceramics were synthesized by solid state reaction method. Effects of Dy substitution on structural distortion, magnetic and optical properties of BiFeO₃ were examined by X-ray diffraction, Raman and UV–Visible spectroscopy. The samples were found to crystallize in rhombohedral structure of BiFeO₃ with R3c space group. The reduction in lattice parameters and unit cell volume indicate the distortion in FeO₆ octahedra of the rhombohedral structure without any signature of phase transformation up to x=0.12. The predictable weak ferromagnetic hysteresis loops can be observed in the Dy doped samples with maximum remnant magnetization of 0.2103 emu/g for x=0.12. The weak ferromagnetism is ascribed to the suppressed spiral spin structure and magnetically active characteristic of Dy³⁺ ions together with ferromagnetic coupling between Dy³⁺ and Fe³⁺ ions. With optical band gap in visible region, Dy doped BiFeO₃ ceramics are potential material for optoelectronic device and solar cell applications.