Synthesis and properties of Au-Fe3O4 and Ag-Fe3O4 heterodimeric nanoparticles

Monodisperse Au-Fe 3 O 4 heterodimeric nanoparticles (NPs) were prepared by injecting precursors into a hot reaction solution.The size of Au and Fe 3 O 4 particles can be controlled by changing the injection temperature.UV-Vis spectra show that the surface plasma resonance band of Au-Fe 3 O 4 heterodimeric NPs was evidently red-shifted compared with the resonance band of Au NPs of similar size.The as-prepared heterodimeric Au-Fe 3 O 4 NPs exhibited superparamagnetic properties at room temperature.The Ag-Fe 3 O 4 heterodimeric NPs were also prepared by this synthetic method simply using AgNO 3 as precursor instead of HAuCl 4.It is indicated that the reported method can be readily extended to the synthesis of other noble metal conjugated heterodimeric NPs.     

First assignment of the 5ν4 and ν2+4ν4 band systems of CH4 in the 6287-6550 cm region

This paper reports the first assignment of rovibrational transitions of the 5ν₄ and ν₂+4ν₄ band systems of ¹²CH₄ in the 6287-6550 cm⁻¹ region, which is usually referred to as part of the 1.58 μm methane transparency window. The analysis was based on two line lists previously obtained in Grenoble by cavity ring down spectroscopy at T=297 and 79 K completed by three long-path Fourier transform spectra recorded in Reims (at 290 K, L=1603 m, P=1-34 mbar). In order to determine the dipole transition moment parameters and quantify the intensity borrowing due to the resonance interactions, we had to include in the fit of the effective Hamiltonian model some lines of the stronger ν₁+3ν₄ and ν₂+4ν₄ bands. For this purpose, intensities of 179 additional lines were retrieved from FTS spectra above 6550 cm⁻¹ though the analysis of these higher bands is not complete. About 1955 experimental line positions and 1462 line intensities were fitted with RMS standard deviations of 0.003 cm⁻¹ and 13.1%, respectively. A line list of 8029 calculated and observed transitions which are considered as dominant was constructed for ¹²CH₄ in the 6287-6550 cm⁻¹ region. This is the first high-resolution analysis and modelling of 5-quanta band systems of ¹²CH₄.     

N2 and O2 pressure broadening and pressure shift in the 4ν2 band of OCS

To measure accurately OCS concentrations in planetary atmospheres, it is important to know precisely nitrogen and oxygen pressure broadening and pressure-induced shift coefficients for the lines used in the retrievals. We present in this study the corresponding coefficients for lines of the P and R branches of the 4ν₂ band of the primary isotopologue of carbonyl sulfide (¹⁶O¹²C³²S).For this purpose, infrared absorption spectra of a natural carbonyl sulfide (OCS) gas sample were recorded at an unapodized resolution of 0.004 cm⁻¹, at room temperature for different pressures of N₂ and O₂, using a Bruker IFS125HR spectrometer at the LISA Laboratory in France. The line parameters were derived using the multispectrum fitting method applied to the measured shapes of the lines, including the interference effects caused by the line overlaps.The results are compared with earlier measurements and with values calculated using a semi-classical model based upon the Robert and Bonamy formalism that reproduces rather well the experimental m (m=−J for P(J) lines and m=J+1 for R(J) lines) quantum number dependence of the N₂ and O₂ broadening coefficients. On the other hand most of the lines studied here have positive shift coefficients, which do not show any systematic dependence on m. However, in previous studies of the ν₃, 2ν₃ and ν₂ bands, these coefficients were negative for all lines.     

Effects of BaCu（B2O5 ） addition on sintering temperature and microwave dielectric properties of Ba5Nb4O15–BaWO4 ceramics

The effects of BaCu(B2O5)(BCB) addition on the microstructure, phase formation, and microwave dielectric properties of Ba5Nb4O15–BaWO4ceramic are investigated. As a sintering aid, BaCu(B2O5) ceramic could effectively lower the sintering temperature of Ba5Nb4O15–BaWO4ceramic from 1100?C to 950?C due to the liquid-phase effect. Meanwhile,BaCu(B2O5) addition effectively improves the densification of Ba5Nb4O15–BaWO4ceramic and significantly influences the microwave dielectric properties. X-ray diffraction analysis reveals that Ba5Nb4O15and BaWO4coexist with no crystal phase of BaCu(B2O5) in the sintered ceramics. The Ba5Nb4O15–BaWO4ceramics with 1.0 wt% BaCu(B2O5) sintered at 950?C for 2 h presents good microwave dielectric properties of εr = 19.0, high Q × f of 33802 GHz and low τfof2.5 ppm/?C.     

H2-broadening coefficients in the ν2 and ν4 bands of PH3

H₂-broadening coefficients are measured for 41 transitions of PH₃ in the QR branch of the ν₂ band and the PP, RP, and PQ branches of the ν₄ band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 2 to 16 and K from 0 to 11 are located between 995 and . The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter model provides larger broadening coefficients than the Voigt model. These coefficients γ₀(J,K) are found to decrease slightly on the whole as J increases and they decrease significantly for K values approaching or equal to J(J?4). The H₂-broadenings are also calculated on the basis of a semiclassical model of interacting linear molecules, using an atom-atom Lennard-Jones potential in addition to the weak electrostatic contributions. The theoretical results are in satisfactory agreement with the experimental data and reproduce the J and K dependencies of the broadenings, but the decrease observed for the QR(J,K) transitions with K=J is notably overestimated.     

Varistor and dielectric properties of Cr2O3 doped SnO2–Zn2SnO4 composite ceramics

Cr₂O₃ doped SnO₂–Zn₂SnO₄ composite ceramics were prepared by traditional ceramic processing and the varistor, dielectric properties were investigated. With increasing Cr₂O₃ content, the breakdown electrical field E_B increases from 11 to 92 V/mm and the relative dielectric constant ε_r measured at 1 kHz, 50 °C decreases from 11,028 to 3412, respectively. The barrier height ?_B about 0.8–0.84 eV and the decreasing of SnO₂ grain size suggest that the varistor behavior with high ε_r is originated from SnO₂–SnO₂ or SnO₂–Zn₂SnO₄ grain boundary. In the dielectric spectra lower than 1 kHz, a dielectric peak is presented and depressed with increasing bias voltage. Similarly, at high temperature, the dielectric constant also presents a dielectric peak in the temperature spectra and the peak becomes faint with increasing frequency. The exhibition of the dielectric peak is thought to be attributed to the conduction of grain boundary since it is accompanied by the sharp increase of dielectric loss. In addition, a dielectric relaxation with the activation energy about 0.4–0.5 eV was observed in the temperature range of 20–100 °C. Based on the results, the formation mechanism of Schottky barriers at grain boundaries and the varistor behavior with high dielectric constant are well understood.     

High-resolution infrared and theoretical study of the fundamental bands ν2, ν4 and ν9 and the c-Coriolis interacting dyad ν5, ν14 of 1,3,4-thiadiazole

The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C₂H₂N₂S, has been recorded with a resolution of ca. 0.003 cm⁻¹ in the 800-1500 cm⁻¹ spectral region. Five fundamental bands ν₂(A₁; 1391.9 cm⁻¹), ν₄(A₁; 964.4 cm⁻¹), ν₅(A₁; 894.6 cm⁻¹), ν₉(B₁; 821.5 cm⁻¹), and ν₁₄(B₂; 898.4 cm⁻¹) have been analysed using the Watson model. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. The ν₄ and ν₉ bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying ν₅ and ν₁₄ bands. This dyad system has been analysed by a model including first and second order c-Coriolis resonance using the theoretically predicted Coriolis coupling constant . The ν₂ band is strongly perturbed by a local resonance, and we obtain a set of spectroscopic parameters using a model including second order a-Coriolis resonance with the inactive ν₁₀ + ν₁₄ band. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational α-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement.     

Solvothermal synthesis and characterization of α-Fe2O3 nanodiscs and Mn3O4 nanoparticles with 1,10-phenanthroline

α-Fe₂O₃ nanodiscs and Mn₃O₄ nanoparticles have been prepared by the 1,10-phenanthroline as complexing agent in the presence of sodium hydroxide under hydrothermal conditions. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectra. The average diameter of α-Fe₂O₃ nanodiscs is of 2 μm. In the case of Mn₃O₄ sample, the Mn₃O₄ crystallites are nanoparticles with an average size of 34 nm. A formation mechanism for the α-Fe₂O₃ and Mn₃O₄ nanomaterials was proposed.     

The ν12 band of C2D4

The Fourier transform infrared (FTIR) absorption spectrum of the ν₁₂ fundamental band of ethylene-d₄ (C₂D₄) was recorded in the 1017-1137 cm⁻¹ region with an unapodized resolution of 0.0063 cm⁻¹. Upper state (v₁₂ = 1) rovibrational constants consisting of three rotational and five quartic constants were improved by assigning and fitting 2103 infrared transitions using Watson’s A-reduced Hamiltonian in the I^r representation. The band centre of the A-type ν₁₂ band is found to be 1076.98480 ± 0.00002 cm⁻¹. The present analysis covering a wider wavenumber range and higher J and K_c values yielded upper state constants including the band centre which are more accurate than previously reported. The rms deviation of the upper state fit is 0.00045 cm⁻¹. Improved ground state rovibrational constants were also determined from the fit of 1247 ground state combination differences (GSCD) from the presently-assigned infrared transitions of the ν₁₂ band of C₂D₄. The rms deviation of the GSCD fit is 0.00049 cm⁻¹. In the rovibrational analysis, local frequency perturbations were not detected even at high J and K_a values. The calculated inertial defect Δ₁₂ is 0.32551 ± 0.00001 μŲ. The line intensities of the individual transitions in the ν₁₂ band were measured and the band strength of 39.8 ± 2.0 cm⁻² atm⁻¹ was derived for the ν₁₂ band of C₂D₄.     

Simulation of the electronic structure of simple oxides BeO and SiO2 and complex oxides Be2SiO4 and Be2SixGe1 ? xO4 with the phenacite structure

The ab initio numerical calculations of the electronic structure of simple oxides BeO and SiO₂ and complex oxides Be₂SiO₄ and Be₂Si _x Ge_{1 − x} O₄ with the phenacite structure have been performed using the electron density functional theory. The calculations indicate that the main feature of the systems under investigation is the presence of oxygen states in both the valence and conduction bands. The splitting of the bottom of the conduction band has been revealed in the electronic structure of the Be₂Si _x Ge_{1 − x} O₄ system. The splitting width is about 1.5 eV. The main contribution to the formation of a narrow subband of the conduction band comes from the 2s and 2p states of oxygen and the 4d state of germanium. Microscopic models of the spatial localization of the electron density on lower energy states of the conduction band of oxide crystals have been developed using the Wannier function technique. The reflection spectra of BeO, SiO₂, and Be₂SiO₄ have been analyzed. The reported calculations of the electronic structure imply the exciton nature of the 9.7-eV reflection peak in the Be₂SiO₄ crystal.     

DFT calculation of core– and valence–shell electron excitation and ionization energies of 2,1,3-benzothiadiazole C6H4SN2, 1,3,2,4-benzodithiadiazine C6H4S2N2, and 1,3,5,2,4-benzotrithiadiazepine C6H4S3N2

The vertical core– and valence–shell electron excitation and ionization energies of the three title molecules, 1–3, were calculated by density functional theory (DFT) using adequate functional for each type of processes and atoms under study. The inner shells treated were C1s, N1s, S1s, S2s, S2p. Molecular geometry was optimized by DFT B3LYP/6-311 + (d,p). The basis set of triple zeta plus polarization (TZP) Slater-type orbitals was employed for DFT calculations. The ΔSCF method was used to calculate ionization energies. The average absolute deviation (AAD) from experiment of 26 valence-electron ionization energies calculated by DFT for the three molecules 1–3 was 0.14 eV; while that of 24 calculated core-electron binding energies (CEBEs) from experiment was 0.4 eV. Selected core excitation energies were calculated by the multiplet approximation for the three molecules. The AAD of twelve calculated core excitation energies by the multiplet approximation that exclude S2s cases was 0.56 eV. Time-dependent DFT (TDDFT) was employed to calculate the excitation energies and corresponding oscillator strengths of core- and valence-electrons of the molecules. Some selected occupied core orbitals were used to calculate the core-excitation energies with the TDDFT (Sterner–Frozoni–Simone scheme). The core excitation energies thus calculated were in an average error of ca. 28 eV compared to observed values. They were shifted to the value calculated by the multiplet approximation. Convoluted spectra based upon the shifted energies and accompanying oscillator strengths reproduce low-energy region of observed spectra reasonably well, whereas they deviate from experiment in high-energy region. Reasonable agreement between theory and experiment was obtained for the valence electron excitations of the molecules.     

Effects of K4CuNb8O23 on phase structure and electrical properties of K0.5Na0.5NbO3–LiSbO3 lead-free piezoceramics

Dense K₄CuNb₈O₂₃ (KCN) modified 0.948K_0.5Na_0.5NbO₃–0.052LiSbO₃ (KNNLS) ceramics were prepared by conventional solid state reaction method. The effect of addition of K₄CuNb₈O₂₃ liquid phase sintering aid on the phase structure and electrical properties of ceramics was studied. Results showed that K₄CuNb₈O₂₃ induced a perovskite structure transition from coexistence of orthorhombic and tetragonal phases to orthorhombic symmetry. The addition of K₄CuNb₈O₂₃ promoted the sintering of KNNLS ceramics. In particular, the K₄CuNb₈O₂₃ addition to the KNNLS greatly improved the mechanical quality factor Q_m value. The ceramics with x=0.8 sintered at 1090 °C possess the optimum properties (Q_m=192, d₃₃=135 pC/N, tan δ=0.024 and k_p=0.357). These results indicate that the ceramic is a promising candidate for lead-free high-power piezoelectric devices, such as piezoelectric actuators, transformers and filter materials.     

High resolution rovibrational spectroscopy of pyrimidine: Analysis of the B1 modes ν10b and ν4 and B2 mode ν6b

We report the first high resolution rovibrational analysis of the infrared spectrum of pyrimidine (C₄H₄N₂) based on measurements using our Fourier transform spectrometer, the Bruker IFS 125 HR Zürich Prototype (ZP) 2001. Measurements were conducted at room temperature in a White-type cell with effective optical path lengths between 3.2 and 9.6 m and with resolutions ranging from 0.0008 to 0.0018 cm⁻¹ in the region between 600 and 1000 cm⁻¹. The spectrum was analyzed in the ν₄ (), ν_10b () and ν_6b regions of pyrimidine () using an effective Hamiltonian. A total of about 15 000 rovibrational transitions were assigned. The root mean square deviations of the fitted data are in the ranges d_rms = 0.00018-0.00024 cm⁻¹, indicating an excellent agreement of experimental line data with the calculations. The results are discussed briefly in relation to possible extensions to spectra of DNA bases and to intramolecular vibrational redistribution at higher energy. The analysis of the ν_10b and ν₄ bands will also be useful in the interstellar search for pyrimidine in the infrared region.     

The 2ν4 overtone bands of FClO3

The high resolution infrared spectrum of the mono-isotopic species F³⁵Cl¹⁶O₃ has been studied in the region of the 2ν₄ overtone, from 2560 to 2680 cm⁻¹. The perpendicular component is strong and clearly observed while the parallel component is very weak and almost completely hidden by the perpendicular one. Their origins differ by 12.6 cm⁻¹, the being located at higher wavenumbers. The band is perturbed by the anharmonic interaction between the v₄ = 2, l₄ = ?2 and v₂ = v₄ = v₅ = 1, l₄ = l₅ = ±1 excited states, both of E symmetry. In total 3157 transitions have been assigned, 83% of these to , 12% to , and 5% to . The three bands have been analyzed simultaneously, taking into account the Fermi resonance effective between the excited states of E symmetry. The ro-vibration parameters of the excited states have been obtained, including the deperturbed band origins of and , at 2628.5890(4) and 2619.3342(5) cm⁻¹, respectively. The W₂₄₅ anharmonic constant is equal to 4.0161(4) cm⁻¹. The x₄₄+g₄₄ and x₂₄+x₄₅+g₄₅ anharmonicity constants have been derived from the obtained band origins and those of ν₄ and ν₂ + ν₅.     

(NH4)2SO4，NH4NO3和(NH4)2SO4/NH4NO3混合气溶胶吸湿质量增长因子的快速测量方法

气溶胶颗粒的吸湿性决定了其尺寸、浓度、化学组成以及相态,从而显著影响着全球气候、大气异相化学以及人类健康。运用在线、原位、连续扫描衰减全反射傅里叶变换红外光谱（ATR-FTIR）技术, 结合线性湿度（RH）控制系统,实现了RH连续变化条件下气溶胶FTIR-ATR光谱的快速测量。根据水弯曲振动谱带（~1 640 cm-1）峰面积随RH的变化,得到了(NH₄)₂SO₄,NH₄NO₃和(NH₄)₂SO₄/NH₄NO₃混合气溶胶的质量增长因子（MGFs）、潮解点（DRH）和风化点（ERH）。与气溶胶的E-AIM模型预测值相比较,实验结果表现出良好的一致性,证实该方法是一种测量大气气溶胶MGFs,ERH和DRH的快速测量方法。     

Biomolecule-assisted hydrothermal synthesis of Sb2S3 and Bi2S3 nanocrystals and their elevated-temperature oxidation behavior for conversion into α-Sb2O4 and Bi2O3

We have developed a novel biomolecule-assisted hydrothermal method to prepare Sb₂S₃ and Bi₂S₃ nanocrystals with various sizes and shapes, in which cysteine combined with other sulfur source can exert the synergistic effect on products. The samples were characterized XRPD, TEM, HRTEM, FESEM, and PL techniques. First, we prepared a series of Sb₂S₃ and Bi₂S₃ nanocrystals by simply adjusting the composition of sulfur sources under hydrothermal conditions. Then, we studied the elevated-temperature oxidation behavior of these sulfides in air, which can lead to the formation of α-Sb₂O₄ and Bi₂O₃ samples at 600 °C for 3 h. The optical properties of the α-Sb₂O₄ and Bi₂O₃ samples were also discussed.     

On the Study of Resonance Interactions and Splittings in the PH3 Molecule: ν1, ν3, ν2+ν4, and 2ν4 Bands

The high-resolution (0.005 cm⁻¹) Fourier transform infrared spectrum of PH₃ is recorded and analyzed in the region of the fundamental stretching bands, ν₁ and ν₃. The ν₂+ν₄ and 2ν₄ bands are taken into account also. Experimental transitions are assigned to the ν₁, ν₃, ν₂+ν₄, and 2ν₄ bands with the maximum value of quantum number J equal to 15, 15, 13, and 15, respectively. a₁-a₂ splittings are observed and described up to the value of quantum number K equal to 10. The analysis of a₁/a₂ splittings is fulfilled with a Hamiltonian model which takes into account numerous resonance interactions among all the upper vibrational states.     

A multispectrum analysis of the ν4 band of CH4: Widths, shifts, and line mixing coefficients

Line positions, Lorentz air-broadened half width and air pressure-induced shift coefficients have been measured for nearly 200 transitions in the ν₄ band of ¹³CH₄ from high-resolution spectra recorded with the McMath-Pierce Fourier transform spectrometer. Three room temperature spectra of ¹³CH₄ used in the previous study of Malathy Devi et al. (Air-broadened Lorentz halfwidths and pressure-induced line shifts in the ν₄ band of ¹³CH₄. Appl. Opt. 1988; 27: 2296-2308) were analyzed together with a large number of additional spectra of self- and air-broadened CH₄ recorded at 210-314 K and one room-temperature spectrum of self-broadened ¹³CH₄. Analyses applying the multispectrum nonlinear least squares fitting technique were performed to retrieve the spectral line parameters. In addition to air-broadened half width and shift coefficients, self-broadened half width and shift coefficients were determined for at least 56 ¹³CH₄ ν₄ transitions. Off-diagonal relaxation matrix element coefficients for air-broadened line mixing were also determined for 28 pairs of P and R transitions in a number of J manifolds, and mixing parameters for self-broadening were also determined for some of these pairs. Temperature-dependences of the pressure-induced shift and mixing parameters for the ¹³CH₄ lines could not be determined from the spectra used in the present analysis, but temperature dependences of the half width coefficients were determined for the strongest transitions. The results of this study are compared with other studies of air- and self-broadened ¹³CH₄ and ¹²CH₄.     

Line shifts in the ν2, 2ν2, and ν4 bands of NH3 perturbed by O2

Pressure-induced line shift coefficients have been measured for more than 200 rovibrational lines of NH₃ perturbed by O₂ at room temperature (T = 295 K) in some branches of the ν₂, 2ν₂, and ν₄ bands. These lines with J values ranging from 1 to 13 are located in the spectral range 800-1800 cm⁻¹. Experiments were made with a high-resolution Fourier transform spectrometer. The treatment of vibration-rotation lines includes interference effects caused by the overlapping of lines. The O₂ pressure-induced shift coefficients have been derived from the non-linear least-squares multi-pressure fitting technique. The results illustrate a vibrational dependence of line shifts with vibrational quantum number. Most of the measured shifts are negative in the ν₄ band. They are positive for the ν₂ and 2ν₂ bands. The measured shift coefficients are compared with previous measurements and with those calculated from a semiclassical theory based upon the Robert-Bonamy formalism extended to the case of symmetric top molecule with inversion motion. The predictions are generally in satisfactory agreement with the experimental data. Analyses of measured and predicted results illustrate that these shifts mainly originate from the isotropic part of the intermolecular potential.