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1.
ABSTRACT

Single-crystal and powder EPR studies of VO2+-doped lithium hydroxylammonium sulphate (LiNH3OHSO4) were carried out at room temperature. The results indicate the presence of two magnetically inequivalent VO2+ sites. The VO2+ ion takes up a substitutional position in the host lattice. The angular variation of EPR spectra in three mutually perpendicular planes were used to determine the spin Hamiltonian parameters, and the values obtained were the following: For Site 1, gx = 2.0249 ± 0.0002, gy = 1.9698 ± 0.0002, gz = 1.9552 ± 0.0002, Ax = (51 ± 2) × 10?4 cm?1, Ay = (93 ± 2) × 10?4 cm?1, and Az = (165 ± 2) × 10?4 cm?1; and for Site 2, gx = 2.0267 ± 0.0002, gy = 1.9743 ± 0.0002, gz = 1.9213 ± 0.0002, Ax = (40 ± 2) × 10?4 cm?1, Ay = (80 ± 2) × 10?4 cm?1, and Az = (155 ± 2) × 10?4 cm?1. The optical absorption spectrum recorded at room temperature shows four bands. From the optical and EPR data, various molecular coefficients are evaluated, and the nature of bonding in the crystal is discussed.  相似文献   

2.
In this work, three different preparation conditions were used for testing the performance of p-conducting copper phthalocyanine (CuPc) organic field-effect transistors (OFETs). The charge carrier mobility (μ sat=(1.5±0.6)×10?3 cm2/V?s) of the CuPc OFETs with the CuPc film deposited while keeping the substrate at room temperature could be improved when the gate dielectric was modified by a self-assembled monolayer of n-octadecyltrichlorosilane (μ sat=(3.8±0.4)×10?3 cm2/V?s) or when elevated temperatures were applied to the substrate (T S,av=127 °C) during the deposition of the organic film (μ sat=(6.5±0.8)×10?3 cm2/V?s). For the latter case, the dependence of the mobility and threshold voltage with increasing thickness of the organic film was tested—above 13 nm film thickness, no further significant increase of the hole mobility or change in the threshold voltage could be observed. The environmental stability of the OFETs was checked by performing ex situ measurements immediately as the sample was exposed to atmosphere and after 40 days of exposure. The effect of the different preparation conditions on the morphology of the organic films prepared in this work is also discussed in this context.  相似文献   

3.
The free volume of the microvoids in the polyimide samples, irradiated with 6 MeV electrons, was measured by the positron annihilation technique. The free volume initially decreased the virgin value from ~13.70 to ~10.98 Å3 and then increased to ~18.11 Å3 with increasing the electron fluence, over the range of 5?×?1014 – 5?×?1015 e/cm2. The evolution of gaseous species from the polyimide during electron irradiation was confirmed by the residual gas analysis technique. The polyimide samples irradiated with 6 MeV electrons in AgNO3 solution were studied with the Rutherford back scattering technique. The diffusion of silver in these polyimide samples was observed for fluences >2?×?1015 e/cm2, at which microvoids of size ≥3 Å are produced. Silver atoms did not diffuse in the polyimide samples, which were first irradiated with electrons and then immersed in AgNO3 solution. These results indicate that during electron irradiation, the microvoids with size ≥3 Å were retained in the surface region through which silver atoms of size ~2.88 Å could diffuse into the polyimide. The average depth of diffusion of silver atoms in the polyimide was ~2.5 μm.  相似文献   

4.
Sulfur dioxide (SO2) trace gas detection based on quartz-enhanced photoacoustic spectroscopy (QEPAS) using a continuous wave, distributed feedback quantum cascade laser operating at 7.24 μm was performed. Influence of water vapor addition on monitored QEPAS SO2 signal was also investigated. A normalized noise equivalent absorption coefficient of NNEA (1σ) = 1.21 × 10?8 cm?1 W Hz?1/2 was obtained for the ν 3 SO2 line centered at 1,380.93 cm?1 when the gas sample was moisturized with 2.3 % H2O. This corresponds to a minimum detection limit (1σ) of 63 parts per billion by volume for a 1 s lock-in time constant.  相似文献   

5.
Co2+ binding to the nicotinamide adenine dinucleotide (NAD+) molecule in water solution was studied by electron paramagnetic resonance (EPR) and electron spin echo at low temperatures. Cobalt is coordinated by NAD+ when the metal is in excess only, but even in such conditions, the Co/NAD+ complexes coexist with Co(H2O)6 complexes. EPR spin-Hamiltonian parameters of the Co/NAD+ complex at 6 K are g z  = 2.01, g x  = 2.38, g y  = 3.06, A z  = 94 × 10?4 cm?1, A x  = 33 × 10?4 cm?1 and A y  = 71 × 10?4 cm?1. They indicate the low-spin Co2+ configuration with S = 1/2. Electron spin echo envelope modulation spectroscopy with Fourier transform of the modulated spin echo decay shows a strong coordination by nitrogen atoms and excludes the coordination by phosphate and/or amide groups. Thus, Co2+ ion is coordinated in pseudo-tetrahedral geometry by four nitrogen atoms of adenine rings of two NAD+ molecules.  相似文献   

6.
A crystalline structure of LiCoO2 sample was synthesized at different stirring times via sol-gel method. This was followed by the electrochemical characterization of LiCoO2 in 5 M LiNO3 aqueous electrolyte. The hexagonal LiCoO2 was stirred for 30 h produced the highest peak intensity and smallest particle size. A morphological analysis showed the particle size distribution within the range of 0.32–0.47 μm. At lower scan rates of cyclic voltammetry, three pairs of redox peaks at ESCE = 0.81/0.65, 0.89/0.83 and 1.01/0.95 V were observed. The peak separation was proportionally consistent with Li+ diffusion coefficients of 7.42 × 10?8 cm2 s?1 (anodic) and 3.59 × 10?8 cm2 s?1 (cathodic). For specific capacity, the LiCoO2 demonstrated a higher initial specific capacity (115.49 mA h g?1). A small difference (1.92 Ω) in the charge transfer resistance before and after a charge discharge analysis indicated that the Li+ ions had been well-diffused during the intercalation/de-intercalation process.  相似文献   

7.
ABSTRACT

Papagoite is a silicate mineral named after an American Indian tribe and was used as a healing mineral. Papagoite CaCuAlSi2O6(OH)3 is a hydroxy mixed anion compound with both silicate and hydroxyl anions in the formula. The structural characterization of the mineral papagoite remains incomplete. Papagoite is a four-membered ring silicate with Cu2+ in square planar coordination.

The intense sharp Raman band at 1053 cm?1 is assigned to the ν1 (A 1g) symmetric stretching vibration of the SiO4 units. The splitting of the ν3 vibrational mode offers support to the concept that the SiO4 tetrahedron in papagoite is strongly distorted. A very intense Raman band observed at 630 cm?1 with a shoulder at 644 cm?1 is assigned to the ν4 vibrational modes.

Intense Raman bands at 419 and 460 cm?1 are attributed to the ν2 bending modes.

Intense Raman bands at 3545 and 3573 cm?1 are assigned to the stretching vibrations of the OH units. Low-intensity Raman bands at 3368 and 3453 cm?1 are assigned to water stretching modes. It is suggested that the formula of papagoite is more likely to be CaCuAlSi2O6(OH)3 · xH2O. Hence, vibrational spectroscopy has been used to characterize the molecular structure of papagoite.  相似文献   

8.
X-band electron paramagnetic resonance (EPR) study of Cr3+-doped dipotassium tetrachloropalladate single crystal is done at liquid nitrogen temperature. EPR spectrum shows two sites. The spin-Hamiltonian parameters have been evaluated by employing hyperfine resonance lines observed in EPR spectra for different orientations of crystal in externally applied magnetic field. The values of spin-Hamiltonian and zero-field splitting (ZFS) parameters of Cr3+ ion-doped DTP for site I are: g x  = 2.096 ± 0.002, g y  = 2.167 ± 0.002, g z  = 2.220 ± 0.002, D = (89 ± 2) × 10?4 cm?1, E = (16 ± 2) × 10?4 cm?1. EPR study indicates that Cr3+ ion enters the host lattice substitutionally replacing K+ ion and local site symmetry reduces to orthorhombic. Optical absorption spectra are recorded at room temperature. From the optical absorption study, the Racah parameters (B = 521 cm?1, C = 2,861 cm?1), cubic crystal field splitting parameter (Dq = 1,851 cm?1) and nephelauxetic parameters (h = 2.06, k = 0.21) are determined. These parameters together with EPR data are used to discuss the nature of bonding in the crystal.  相似文献   

9.
Gel polymer electrolytes were prepared using agar polymer host, NH4I, and I2 salts. The sample of agar paste with 1.0 M of NH4I and 0.2 μM of I2 exhibits the highest conductivity and lowest viscosity values at room temperature of (2.64?±?0.19)?×?10?3?S?cm?1 and 1.17?±?0.29 Pa?s, respectively. All of the gel polymer electrolytes display Arrhenian behavior, and the optimum agar paste gave the lowest activation energy of 0.25 eV. It also had a good physical appearance compared with the other samples. This gel polymer electrolyte had a good potential and was applicable to a role as electrolyte in ITO-ZnO (N719 dye)/agar paste?+?1.0 M NH4I?+?0.2 μM I2/Au-Pd-ITO dye-sensitized solar cell.  相似文献   

10.
In this paper ~16 μm-emitting multimode InP-related quantum cascade lasers are presented with the maximum operating temperature 373 K, peak and average optical power equal to 720 mW and 4.8 mW at 303 K, respectively, and the characteristic temperature (T0) 272 K. Two types of the lasers were fabricated and characterized: the lasers with a SiO2 layer left untouched in the area of the metal-free window on top of the ridge, and the lasers with the SiO2 layer removed from the metal-free window area. Dual-wavelength operation was obtained, at λ  15.6 μm (641 cm?1) and at λ  16.6 μm (602 cm?1) for lasers with SiO2 removed, while within the emission spectrum of the lasers with SiO2 left untouched only the former lasing peak was present. The parameters of these devices like threshold current, optical power and emission wavelength are compared. Lasers without the SiO2 layer showed ~15% lower threshold current than these ones with the SiO2 layer. The optical powers for lasers without SiO2 layer were almost twice higher than for the lasers with the SiO2 layer on the top of the ridge.  相似文献   

11.
Bulk samples of oriented carbon nanotubes were prepared by electric arc evaporation of graphite in a helium environment. The temperature dependence of the conductivity σ(T), as well as the temperature and field dependences of the magnetic susceptibility χ(T, B) and magnetoresistance ρ(B, T), was measured for both the pristine and brominated samples. The pristine samples exhibit an anisotropy in the conductivity σ(T)/σ>50, which disappears in the brominated samples. The χ(T, B) data were used to estimate the carrier concentration n 0 in the samples: n 0ini ~3×1010 cm?2 for the pristine sample, and n 0Br~1011 cm\t—2 for the brominated sample. Estimation of the total carrier concentration n=n e+n p from the data on ρ(B, T) yields n ini=4×1017 cm?3 (or 1.3×1010 cm?2) and n Br=2×1018 cm?3 (or 6.7×1010 cm?2). These estimates are in good agreement with one another and indicate an approximately fourfold increase in carrier concentration in samples after bromination.  相似文献   

12.
Electron paramagnetic resonance spectra of Cu2+ impurities in cytosine hydrochloride single crystals are observed at liquid nitrogen temperature. Two magnetically equivalent sites for Cu2+ have been observed. The parameters of 63Cu obtained with the fitting of spectra to rhombic symmetry spin Hamiltonian are: g x  = 2.047 ± 0.002, g y  = 2.187 ± 0.002, g z  = 2.390 ± 0.002, A x  = (86 ± 3) × 10?4 cm?1, A y  = (87 ± 3) × 10?4 cm?1, and A z  = (138 ± 3) × 10?4 cm?1. The observed bands in optical spectra of the single crystal recorded at room temperature are assigned to various d–d and charge-transfer transitions. Using both EPR and optical data, the nature of bonding of metal ion with different ligands is discussed.  相似文献   

13.
Abstract

Three new bands of the B 2Σ+X 2Σ+ system of 12C17O+ have been investigated using conventional spectroscopic techniques. The spectra were observed in a graphite hollow‐cathode lamp by discharging molecular oxygen (enriched in about 45% of the 17O2 isotope) under 1.0 Torr pressure. The rotational analysis of the 2–4, 2–5, and 2–6 bands was performed with the effective Hamiltonian of Brown (Brown et al., J. Mol. Spectrosc. 1979; 74: 294–318). Molecular constants were derived from a merge calculation, including both the current wavenumbers and the spectroscopic data published by the authors previously. The principal equilibrium constants for the ground state of 12C17O+ are ωe=2185.9658(84), ωe x e = 14.7674(11), B e=1.927001(38), αe=1.8236(22)×10?2, γe=?0.331(28)×10?4, D e=6.041(12)×10?6, βe=0.100(31)×10?7 cm?1, and the equilibrium constants for the excited state are σe=45876.499(15), ωe=1712.201(12), ωe x e=27.3528(39), B e=1.754109(35), αe=2.8706(57)×10?2, γe = ?1.15(19)×10?4, D e=7.491(20)×10?6, βe=2.13(12)×10?7, γe = 2.0953(97)×10?2, and αγe=?9.46(59)×10?4 cm?1, respectively. Rydberg–Klein–Rees potential energy curves were constructed for the B 2Σ+ and X 2Σ+ states of this molecule, and Franck–Condon factors were calculated for the vibrational bands of the BX system.  相似文献   

14.
X-band electron paramagnetic resonance (EPR) studies are carried out on Fe3+ ions doped in ammonium dihydrogen phosphate (ADP) single crystals at room temperature. The crystal field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular rotations. The obtained values of spin Hamiltonian and zero-field parameters of the Fe3+ ion in ADP are: g = 1.994 ± 0.002, |D| = (220 ± 5) × 10?4 cm?1 and a = (640 ± 5) × 10?4 cm?1. On the basis of EPR data, the site symmetry of the Fe3+ ion in the crystal is discussed. The Fe3+ ion enters the lattice substitutionally replacing the NH4 + sites. The optical absorption of the crystal is also studied at room temperature in the wavelength range of 195–925 nm. The energy values of different orbital levels are calculated. The observed bands are assigned as transitions from the 6 A 1g (S) ground state to various excited quartet levels of the Fe3+ ion in a cubic crystalline field. From the observed band positions, Racah interelectronic repulsion parameters (B and C), cubic crystal field splitting parameter (D q ) and Trees correction are calculated. There values are: B = 970, C = 1,923, D q  = 1,380 cm?1 and α = 90 cm?1, respectively. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The zero-field splitting (ZFS) parameters are also determined theoretically using B kq parameters estimated from the superposition model. The values of ZFS parameters thus obtained are |D| = (213 ± 5) × 10?4 cm?1 and |E| = (21 ± 5) × 10?4 cm?1.  相似文献   

15.
Al-doped ZnO (AZO) was sputtered on the surface of LiNi1/3Co1/3Mn1/3O2 (NCM) thin film electrode via radio frequency magnetron sputtering, which was demonstrated to be a useful approach to enhance electrochemical performance of thin film electrode. The structure and morphology of the prepared electrodes were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer, and transmission electron microscopy techniques. The results clearly demonstrated that NCM thin film showed a strong (104) preferred orientation and AZO was uniformly covered on the surface of NCM electrode. After 200 cycles at 50 μA μm?1 cm?2, the NCM/AZO-60s electrode delivered highest discharge capacity (78.1 μAh μm?1 cm?2) compared with that of the NCM/AZO-120s electrode (62.4 μAh μm?1 cm?2) and the bare NCM electrode (22.3 μAh μm?1 cm?2). In addition, the rate capability of the NCM/AZO-60s electrode was superior to the NCM/AZO-120s and bare NCM electrodes. The improved electrochemical performance can be ascribed to the appropriate thickness of the AZO coating layer, which not only acted as HF scavenger to keep a stable electrode/electrolyte interface but also reduced the charge transfer resistance during cycling.  相似文献   

16.
The present work is devoted to investigation of optical absorption in pure and neodymium-doped YAlO3 (YAP) single crystals in the spectral range 0.2–1.1 μm induced by the influence of 12C ions irradiation with energy 4.50 MeV/u (MeV per nucleon) and a fluence 2 × 109 cm?2 or of 235U ion irradiation with energy 9.35 MeV/u and a fluence 5 × 1011 cm?2. The induced absorption in the case of 12C ions irradiation is caused by recharging of point growth defects and impurities under the radiation influence. After irradiation by 235U ions with fluence 5 × 1011 cm?2 the strong absorption rise is probably caused by contribution of the lattice destruction as a result of heavy ion bombardment.  相似文献   

17.
This study presents a novel exposure protocol for synthesized nanoparticles (NPs). NPs were synthesized in gas phase by thermal decomposition of metal alkoxide vapors in a laminar flow reactor. The exposure protocol was used to estimate the deposition fraction of titanium dioxide (TiO2) NPs to mice lung. The experiments were conducted at aerosol mass concentrations of 0.8, 7.2, 10.0, and 28.5 mg m?3. The means of aerosol geometric mobility diameter and aerodynamic diameter were 80 and 124 nm, and the geometric standard deviations were 1.8 and 1.7, respectively. The effective density of the particles was approximately from 1.5 to 1.7 g cm?3. Particle concentration varied from 4 × 105 cm?3 at mass concentrations of 0.8 mg m?3 to 12 × 106 cm?3 at 28.5 mg m?3. Particle phase structures were 74% of anatase and 26% of brookite with respective crystallite sized of 41 and 6 nm. The brookite crystallites were approximately 100 times the size of the anatase crystallites. The TiO2 particles were porous and highly agglomerated, with a mean primary particle size of 21 nm. The specific surface area of TiO2 powder was 61 m2 g?1. We defined mice respiratory minute volume (RMV) value during exposure to TiO2 aerosol. Both TiO2 particulate matter and gaseous by-products affected respiratory parameters. The RMV values were used to quantify the deposition fraction of TiO2 matter by using two different methods. According to individual samples, the deposition fraction was 8% on an average, and when defined from aerosol mass concentration series, it was 7%. These results show that the exposure protocol can be used to study toxicological effects of synthesized NPs.  相似文献   

18.
H.A. Mohamed 《哲学杂志》2013,93(30):3467-3486
This work investigates dependence of the short-circuit current density, open-circuit voltage, fill factor and efficiency of a thin film CdS/PbS solar cell on thickness of transparent conductive oxide (TCO) layer, thickness of window layer (CdS), concentration of uncompensated acceptors (width of space-charge region), carrier lifetime in PbS and the reflectivity from metallic back contact. The effect of optical losses, front and rear recombination losses as well as the recombination losses on space-charge region are also considered in this study. As a result, by thinning the front contact layer indium tin oxide from 400 to 100 nm and window layer (CdS) from 200 to 100 nm it is possible to reduce the optical losses from 32 to 20%. The effect of electron lifetime on the internal and external quantum efficiency can be neglected at high width of the space-charge region. The maximum current density of 18.4 mA/cm2 is achieved at wide space-charge region (concentration of uncompensated acceptors = 1015 cm?3) and the longest lifetime (τn = 10?6 s) where the optical and recombination losses are about 55%. The maximum efficiency of 5.17%, maximum open-circuit voltage of 417 mV and approximately fixed fill factor of 74% are yielded at optimum conditions such as: electron lifetime = 10?6 s; concentration of uncompensated acceptors = 1016 cm?3; thickness of TCO = 100 nm; thickness of CdS = 100 nm; velocity of surface and rear recombination = 107 cm/s and thickness of absorber layer = 3 μm. When the reflectance from the back contact is 100%, the cell parameters improve and the cell efficiency records a value of 6.1% under the above conditions.  相似文献   

19.
In order to establish the mechanism and to determine the parameters of lithium transport in electrodes based on lithium-vanadium phosphate (Li3V2(PO4)3), the kinetic model was designed and experimentally tested for joint analysis of electrochemical impedance (EIS), cyclic voltammetry (CV), pulse chronoamperometry (PITT), and chronopotentiometry (GITT) data. It comprises the stages of sequential lithium-ion transfer in the surface layer and the bulk of electrode material’s particles, including accumulation of lithium in the bulk. Transfer processes at both sites are of diffusion nature and differ significantly, both by temporal (characteristic time, τ) and kinetic (diffusion coefficient, D) constants. PITT data analysis provided the following D values for the predominantly lithiated and delithiated forms of the intercalation material: 10?9 and 3 × 10?10 cm2 s?1, respectively, for transfer in the bulk and 10?12 cm2 s?1 for transfer in the thin surface layer of material’s particles. D values extracted from GITT data are in consistency with those obtained from PITT: 3.5–5.8 × 10?10 and 0.9–5 × 10?10 cm2 s?1 (for the current and currentless mode, respectively). The D values obtained from EIS data were 5.5 × 10?10 cm2 s?1 for lithiated (at a potential of 3.5 V) and 2.3 × 10?9 cm2 s?1 for delithiated (at a potential 4.1 V) forms. CV evaluation gave close results: 3 × 10?11 cm2 s?1 for anodic and 3.4 × 10?11 cm2 s?1 for cathodic processes, respectively. The use of complex experimental measurement procedure for combined application of the EIS, PITT, and GITT methods allowed to obtain thermodynamic E,c dependence of Li3V2(PO4)3 electrode, which is not affected by polarization and heterogeneity of lithium concentration in the intercalate.  相似文献   

20.
Nanocomposite polymer electrolyte thin films of polyvinyl alcohol (PVA)-orthophosphoric acid (H3PO4)-Al2O3 have been prepared by solution cast technique. Films are irradiated with 50 MeV Li3+ ions having four different fluences viz. 5?×?1010, 1?×?1011, 5?×?1011, and 1?×?1012 ions/cm2. The effect of irradiation on polymeric samples has been studied and characterized. X-ray diffraction spectra reveal that percent degree of crystallinity of samples decrease with ion fluences. Glass transition and melting temperatures have been also decreased as observed in differential scanning calorimetry. A possible complexation/interaction has been shown by Fourier transform infrared spectroscopy. Temperature-dependent ionic conductivity shows an Arrhenius behavior before and after glass transition temperature. It is observed that ionic conductivity increases with ion fluences and after a critical fluence, it starts to decrease. Maximum ionic conductivity of ~2.3?×?10?5 S/cm owing to minimum activation energy of ~0.012 eV has been observed for irradiated electrolyte sample at fluence of 5?×?1011 ions/cm2. The dielectric constant and dielectric loss also increase with ion fluences while they decrease with frequency. Transference number of ions shows that the samples are of purely ionic in nature before and after ion irradiation.  相似文献   

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