Structural properties of Zinc Lithium borate glass

Zinc Lithium Borate glasses of different composition were prepared with the aim of using it for thermoluminescence dosimetry. Melt quenching method was adopted in this process. Fourier transform Infrared (FTIR) spectroscopy and UV-vis-NIR spectroscopy techniques were employed to investigate the infrared spectra and energy band gap of different composition of Zinc Lithium Borate glasses. X-ray diffraction analysis was used to confirm the amorphous nature of the glass samples. Glass forming ability and stability of the glass was checked using Differential thermal analysis (DTA). Density, molar volume, refractive index parameters have been analyzed in the light of different concentration of the modifier. The active vibrational modes of 1200–1600 cm^?1 for B-O stretching of BO₃ units, 800–1200 cm^?1 for B-O stretching of BO₄ units and 400–800 cm^?1 for bending vibration of various borate segments were detected. Addition of ZnO to lithium borate shows its influence in converting the dominant BO₃ group to BO₄ group. BO₄ are known for creating complex defects, a situation that established deep and stable traps good for thermoluminescence phenomena. From optical data, direct and indirect energy band gap has been calculated using the data obtained from UV-vis-NIR spectroscopy. Both direct and indirect band gaps decrease with the increase of modifier Li₂CO₃.     

Localization of conduction electrons in the ferromagnetic clusters AuFe

The optical-conductivity spectra of concentrated solutions Au_{1 ? x} Fe _x with x = 17 and 22 at % have been measured in a frequency range of (10–33) × 10³ cm^?1 at room temperature. The results are analyzed together with previous optical data obtained for compounds with x = 4–12 at %. It is found that the magnetic contributions σ_magn = σ_AuFe ? σ_Au to dc and low-frequency(10 cm^?1) conductivities for an Fe concentration below 4 at % are almost equal, while the low-frequency magnetic contribution for larger concentrations is significantly larger than the dc one. An absorption band at frequencies of 1000–3000 cm^?1 has been found for samples with concentrations x = 6–22 at %. The observed phenomena are attributed to the localization of electrons inside clusters containing ferromagnetically ordered iron ions.     

A comparative study on the effects of salt and filler on transport and structural properties of organic–inorganic hybrid electrolytes

Organic–inorganic hybrid electrolytes based on the reaction of tri-block copolymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether), poly(ethylene glycol diglycidyl ether, and (3-glycidyloxypropyl)trimethoxysilane doped with LiClO₄ and SiO₂ nanoparticles were synthesized by a sol–gel process. The structural and dynamic properties of the materials thus obtained were systematically investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, alternate current impedance, and ¹³C solid-state NMR measurements. A maximum ionic conductivity of 3.2?×?10^?5 S cm^?1 was obtained at 30 °C for the solid hybrid electrolyte with a [O]/[Li] ratio of 16 and 7 wt% of SiO₂ nanoparticles. A Vogel–Tamman–Fulcher-like temperature dependence of ionic conductivity was observed for the hybrid electrolytes, implying that the diffusion of charge carriers was assisted by the segmental motions of the polymer chains.     

Static and high-frequency hole transport in <Emphasis Type="Italic">p</Emphasis>-Si/SiGe heterostructures in the extreme quantum limit

Complex high-frequency (HF), σ^AC = σ₁ ? iσ₂, and static, σ^DC, conductivities, as well as current-voltage characteristics, have been measured in p-Si/SiGe heterostructures with a low hole density (p = 8.2 × 10¹⁰ cm^?2) at temperatures T = 0.3–4.2 K in the ultraquantum limit, when the filling factor is v < 1. In order to determine the components of the HF conductivity, the acoustic contactless method in the “hybrid configuration” is used, when the surface acoustic wave propagates on the surface of the LiNbO₃ piezoelectric and the heterostructure is pressed to the surface by a spring. The conductivities σ₁ and σ₂ are determined from the damping and velocity of the surface acoustic waves that are measured simultaneously with varying the magnetic field. The revealed HF conductivity features—σ₁ ? |σ₂|, the negative sign of σ₂, the threshold behavior of the current-voltage characteristic, and the dependence I ∝ exp(-A/V ^0.3) in the subthreshold region—indicate the formation of a pinned Wigner crystal (glass) in the ultraquantum limit (T = 0.3–0.8 K, B > 14 T).     

Polypyrrole–NiO hybrid nanocomposite films: highly selective,sensitive, and reproducible NO2 sensors

Polypyrrole–nickel oxide (PPy–NiO) hybrid nanocomposite thin-film sensor was prepared by spin-coating method on glass substrate. The PPy–NiO hybrid nanocomposite thin film sensors were used to study room temperature gas-sensing properties for oxidizing (NO₂, Cl₂) as well as reducing (NO₂, H₂S, C₂H₅OH, NH₃, and Cl₂) gases. It was revealed that PPy–NiO (50 %) hybrid nanocomposite thin-film sensor could detect NO₂ at low concentration (100 ppm) with very high selectivity (47 % compared with Cl₂) and high sensitivity (47 %), with better stability (90 %) and reproducibility. The response and recovery times were changed significantly with NO₂ concentration.     

Preparation of n-ZnO/p-Si solar cells by oxidation of zinc nanoparticles: effect of oxidation temperature on the photovoltaic properties

In this study, n-ZnO/p-Si solar cells were fabricated by spraying ZnO nanoparticles (NPs) film synthesised by dissolving of high purity zinc in hydrogen peroxide H₂O₂ followed by thermal oxidation in air on p-type silicon substrates. The oxidation was carried out at different temperatures (200–500) °C. The crystalline structure of the ZnO NPs films was investigated by X-ray diffraction which indicated wurtzite structure films along (100) plane. The morphology of the NPs was studied by atomic force microscopy and scanning electron microscopy. The result showed an average grain size of ZnO NPs in the range of (72.7–95.8) nm and the surface roughness increasing with oxidation temperature. Three peaks located at ultraviolet, violet and green emission regions were noticed in the photoluminescence spectra of ZnO NPs. From optical studies, it was shown that the direct optical band gap is found to be in the range of (3.85–3.96) eV depended on the oxidation temperature. The synthesised ZnO films have n-type conductivity, and the mobility was in the range of (7–24) cm² V^?1 s^?1. Current–voltage I–V and capacitance–voltage C–V of ZnO NPs/Si heterojunction solar cell were investigated as function of oxidation temperature. The spectral response of n-ZnO NPs/p-Si solar cell showed two peaks of response and its maximum value approaching 0.62 mA W^?1 at λ = 800 nm. Solar cell oxidized at 500 °C gave open circuit voltage V _OC of 375 mV, short circuit current density J _SC of 25 mA cm^?2, a fill factor FF of 0.72, and conversion efficiency η of 6.79 % under illumination of 100 mW cm^?2.     

The measurements of correlation times of molecules adsorbed on silica gel,alumina and charcoal using NOESY and MAS NMR

The correlation times (τ_c) and cross relaxation rates of toluene, dimethylformamide, tetrahydrofuran, water-acetone and water-dioxane adsorbed on silica gel, alumina and charcoal were obtained by measurements of the integrated intensities of cross and diagonal peaks in their NOESY spectra. The (τ_c) of the above mentioned systems is in the range of 10^?6?10^?9 s, much longer than that in the liquid (10^?12?10^?14 s). It was found that intramolecular rotation of toluene adsorbed on charcoal is slower than that on SiO₂, Al₂O₃ and the inversion of α and β protons in tetrahydrofuran is very fast (τ_c = 1.76×10^?9 s). The cross relaxation plays an important role in the relaxation of molecules adsorbed on solid surfaces with low electron densities.     

Nd-doped calcium molybdate core and particles: synthesis,optical and photoluminescence studies

CaMoO₄:Nd (core), CaMoO₄:Nd@CaMoO₄ and CaMoO₄:Nd@CaMoO₄@SiO₂ core–shell nanoparticles were synthesized using polyol method under urea hydrolysis. X-ray diffraction and thermogravimetric analysis were employed to examine the structural and thermal properties of the as-prepared core and core–shell nanoparticles. Optical properties of core and core–shell nanoparticles were observed to investigate the influence of surface coating on the spectra of as-prepared nanomaterials in terms of ultraviolet/visible (UV-Vis) absorbance, FTIR, Raman and emission spectra. The optical band gap energy calculated from the UV-Vis absorption spectrum for CaMoO₄:Nd, CaMoO₄:Nd@CaMoO₄ and CaMoO₄:Nd@CaMoO₄@SiO₂ nanoparticles was 3.09, 2.06 and 1.26 eV, respectively. The photoluminescence spectra of the samples showed broad charge transfer emission band of [MoO₄]^2? along with sharp transitions of neodymium ion in the visible and near infrared regions, respectively.     

Highly Water‐Dispersible,Highly Conductive,and Biocompatible Polypyrrole‐Coated Silica Particles Stabilized and Doped by Chondroitin Sulfate

Currently available methods to prepare conducting polymers‐coated colloidal substrates for biomedical applications need to be improved because they involve the use of toxic reagents and tend to result in aggregated products with diminished conductivity. The work herein describes for the first time a facile strategy for preparing highly water‐dispersible, highly conductive, and biocompatible polypyrrole‐coated silica core–shell (SiO₂@PPy) particles using only chondroitin sulfate (CS), a biologically derived polymer, as the stabilizer and dopant. The CS preadsorbed onto silica surface serves as a template to control the confined growth of the PPy shell and doping of in situ polymerized PPy shell. The thickness of the PPy shell can be tuned from 8 to 17 nm by varying the CS preadsorbed amount. Increasing the thickness of the adsorbed CS layer can control the deposition of thinner PPy shells on an SiO₂ core surface to provide highly water‐dispersible SiO₂@PPy particles. Moreover, CS‐doped SiO₂@PPy particles exhibit conductivities as high as 5.3 S cm^?1. The conductivity of the particles depends on the PPy mass loading and the doping level of the PPy shell. Furthermore, the SiO₂@PPy particles exhibit good biocompatibility and therefore have potential applications in biomedicine.     

Optical absorption spectrum and crystal field of erbium aluminum garnet (ErAlG)

The optical absorption spectrum of Erbium Aluminum Garnet (ErAlG) has been measured between 12000 cm^?1 and 26000 cm^?1. The crystal field splitting of the terms⁴I_15/2,⁴I_9/2,⁴F_9/2,⁴S_3/2,²H_11/2,⁴F_7/2,⁴F_5/2,⁴F_3/2,²H_9/2 and⁴G_11/2 was determined from the spectra and has been analysed in terms of the usual parametrization scheme. Nine crystal field parametersA _l ^m 〈r ^l〉≡B _l ^m which are necessary to describe the crystal field with the symmetryD ₂ at the site of the rare earth ion, were fitted to the experimental data. The values are (in cm^?1):B ₂ ⁰=+160B ₄ ⁰=?160B ₆ ⁰=+30B ₆ ⁶=+80B ₂ ²=?100B ₄ ²=+140B ₂ ⁶=?40B ₄ ⁴=?1800B ₆ ⁴=?700 This result is compared with those obtained from similar analysis of other garnets.     

Conductivities and ion association constants of ferric chloride and chromic chloride in DMF and DMSO as a function of temperature

The equivalent conductivities of anhydrous ferric chloride (FeCl₃) and anhydrous chromic chloride (CrCl₃) were measured in nonaqueous aprotic solvents such as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at temperatures between 278.15 and 318.15 K. In both DMF and DMSO, conductivity values for FeCl₃ were found to be higher than those for CrCl₃. In addition, the conductivity values for both FeCl₃ and CrCl₃ in DMF were higher than those in DMSO at all temperatures. The conductivity data were analyzed by the Robinson–Stokes equations. The limiting equivalent ionic conductivities for ferric ion (Fe³⁺) and chromic ion (Cr³⁺) and the ion association constants (K _A ) for FeCl₃ and CrCl₃ were determined in DMF and DMSO. The K _A values calculated for both FeCl₃ and CrCl₃ in DMF were higher than those in DMSO. This can be ascribed to an increase of the ion association constants with a decrease of the relative permittivity of solvents used in this study. The K _A values increased with the increase in temperature in the studied solvents. Thermodynamic functions (Gibbs’ free energy, entropy, and enthalpy of ion association) were estimated from the temperature dependence of the ion association constant. The positive values of entropy and enthalpy found for FeCl₃ and CrCl₃ at all temperatures indicate that the association process in DMF and DMSO is endothermic.     

Mössbauer studies of iron stabilised polymethacrylates

Polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA) and polybutyl methacrylate (PBuMA) containing ferric chloride and ferrous sulphate as stabilisers, were prepared by free radical polymerization. Mössbauer spactra of ferrous sulphate stabilised polymers don't show any change in the value of isomer shift (1.30 mm/s) while quadrupole splitting values are quite different from those for pure ferrous sulphate. This indicates that environment of Fe²⁺ moiety changes in polymers and thus stabilises the polymers. In case of ferric chloride stabilised polymers the isomer shift values don't differ significantly for different polymethacrylates but quadrupole splitting values increase from polymethyl methacrylate to polybutyl methacrylate. The TGA analysis shows that the inclusion of iron salts stabilises the polymers by 40°C (approx.) and at higher temperatures α-Fe₂O₃ is formed.     

New hydrogen associated paramagnetic centre in LiNbO3

A new hydrogen associated paramagnetic centre (g=2.0028±0.0005, A=3±0.5 mT at 77K) was observed in LiNbO₃. This centre is identified as an OH^2? ion, produced as a result of an electron capture by a diamagnetic OH^? ion, substituting the O^2? ion in LiNbO₃. An experimental procedure for detecting the EPR spectrum of the new centre is established. It is based on the observation of the more rapid destruction of O^? and Nb⁴⁺ ions under UV-irradiation at 77 K as compared to the OH^2? ions obtained after γ-irradiation of LiNbO₃ crystals at 77 K.     

Spectral and nonlinear studies of an aniline blue dye in liquid and solid media

Solid-state dye-doped polymers are an attractive alternative to conventional liquid dye solutions. In this paper, the spectral characteristics and nonlinear properties of the Aniline Blue dye has been studied. The third-order nonlinear optical properties of the Aniline Blue dye in ethanol and a dye-doped polymer film were measured by the Z-scan technique using a 632.8-nm He-Ne laser. This material exhibits a negative optical non-linearity. The dye at a 0.4-mM concentration exhibited a nonlinear refractive coefficient (n ₂ = ?4.02 × 10^?8 and ?4.41 × 10^?8 cm²/W in liquid and solid media, respectively), a nonlinear absorption coefficient (β = ?9.7 × 10^?4 and ?11.63 × 10^?4 cm/W in liquid and solid media, respectively), and susceptibility (x ⁽³⁾ = 1.844 × 10^?6 and 2.028 × 10^?6 esu in liquid and solid media, respectively). These results show that the Aniline Blue dye has potential applications in nonlinear optics.     

Study on performance of a novel P(VDF-HFP)/SiO2 composite polymer electrolyte using urea as pore-forming agent

Novel poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))-based composite polymer electrolyte (CPE) membranes doped with different contents of nano-SiO₂ using urea as a pore-forming agent were prepared by phase inversion method, and the desired CPEs were obtained by being immersed into 1.0 M LiPF₆-EC/DMC/EMC electrolytes for 0.5 h. The physicochemical properties of the CPEs were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). The results show that the CPEs doped with 10 % nano-SiO₂ exhibit the best performance, in which the SEM images of the as-prepared polymer membranes present homogeneous surface and abundant micropores; the uptake ratio is up to 107.4 %; EIS and LSV analysis also show that the ionic conductivity at room temperature and electrochemical stability window of the modified membrane can reach 3.652 mS cm^?1 and 5.0 V, respectively; the interfacial resistance R _i is 380 Ω cm^?2 in the first day,then increases rapidly to a stable value about 500 Ω cm^?2 in a 5-day storage at room temperature. The Li/As-fabricated CPEs/LiCoO₂ cell also shows excellent charge-discharge performance, which suggests that it can be a potential electrolyte for the lithium-ion battery.     

Small angle neutron scattering from micellar solutions of triton X-100

Micellar solutions of non-ionic surfactant triton X-100 (8% by weight) show phase separation at cloud pointT _cp ～ 335 K. This paper reports results of small angle neutron scattering (SANS) experiments from this solution as a function of temperature between 298 and 332 K. The range of wave-vector transferQ, covered in these experiments is from 0.02 to 0.15 Å^?1. It is seen that as one approachesT _cp, the neutron scattering cross section diverges in the region of lowQ (<0.06 Å^?1) while it is independent of temperature in region of largeQ(>0.06 Å^?1). We believe that the divergence of scattering at lowQ with an increase in temperature is because of changes in the structure factorS(Q) of the solution. The measured distributions have been analyzed using four different models for inter-micellar potential. The models used to calculate the structure factorS(Q) are (1) mean spherical approximation (MSA) with Yukawa tail for attractive potential, (2) MSA with an attractive square well potential, (3) random phase approximation (RPA) with an attractive square-well potential and (4) Sticky hard sphere model (attractive square-well potential with Percus-Yevick approximation). The strengths of the attractive potential required to fit the SANS data are (?6.6 to ? 14.4)/kt for model (1), (? 6.6 to ? 15.0)/kt for model (2), (? 3.8 to ? 7.3)/k _B T for model (3) and (?2 to ?2.7)/kt for model (4). On the basis of reasonableness of the derived strength of the potential near the phase separation temperature and its relative temperature dependence, it is concluded that present data favour the Sticky hard sphere model.     

Measurement of theK-shell fluorescence yield of13Al,20Ca,23V and25Mn for vacancies produced by the relativistic electron impact

The K-shell fluorescence yield of Al, Ca, V and Mn has been measured by bombarding thin solid targets of 0.5–4.0μg/cm² on 6–10μg/cm² carbon backing with relativistic electrons of 30 and 60 MeV and by simultaneous detection of the x-ray and Auger yield by means of a Si(Li) detector and an electrostatic electron spectrometer, respectively. While the values obtained for₂₅Mn (ω_K=0.310 _?0.020 ^+0.023 ) and₂₃V(ω_K=0.252 _?0.018 ^+0.020 ) agree within their accuracy with known experimental and theoretical data, are the values of₂₀Ca (ω_K=0.127 _?0.011 ^+0.013 ) and₁₃Al(ω_K=0.027±0.005) lower than experimental or recommended empirical values.     

Limits on the τ neutrino electromagnetic properties from single photon searches ate + e − colliders

We set limits on the magnetic moment and charge radius of the τ neutrino by examining the contributions to the processe ⁺ e ^?→v \(\bar \nu \) γ due to such interactions. We find thatK(ν_τ)<4×10^?6 (i.e.μ(ν_τ)<4×10^?6μ _B , μ _B =e/2m _e ) and 〈r ²〉<2×10^?31 cm² using the combined data of the MAC, ASP, CELLO, and Mark J collaborations for this process. We briefly discuss whether these bounds can be improved in any futuree ⁺ e ^? experiments.     

Beta-delayed proton precursors with 59≦Z≦62

The new, beta-delayed proton emitters¹²⁸Pr(3.2 _?0.4 ^+0.5 s),¹³⁰Pm(2.2 _?0.4 ^+0.6 s), and¹³²Pm(5.0 _?0.6 ^+0.8 s) have been observed at the on-line isotope separator OASIS. Also studied were¹²⁹Nd and¹³³Sm. Our on-going study of the decay properties of very neutron-deficient lanthanides has led to detailed information about beta-delayed proton emitters with 59≤Z≤62. The isotopes were produced at the SuperHILAC's on-line isotope separator OASIS [1] in reactions of⁴⁰Ca projectiles on⁹²Mo and⁹⁶Ru targets enriched to >95%. Decay studies were carried out in a low background spectroscopy laboratory. The isotope of interest was passed through a slit in the focal plane of the mass separator, transported ionoptically to a fast cycling tape, and periodically positioned between a silicon charged particle telescope, a HPGe x-ray detector, and a GAMMA-X Ge detector. Decays involving beta-delayed gamma rays and protons along with any coincident positrons, x-rays and gamma rays were measured event-by-event and written to computer tape for subsequent replay and analysis.     

Incorporation of NH4Br in PVA-chitosan blend-based polymer electrolyte and its effect on the conductivity and other electrical properties

Polymer electrolyte system based on poly(vinyl alcohol) (PVA)-chitosan blend doped with ammonium bromide (NH₄Br) has been prepared by solution cast method. Fourier transform infrared (FTIR) spectroscopy analysis confirms the complexation between salt and polymer host. The highest ionic conductivity obtained at room temperature is (7.68?±?1.24)?×?10^?4 S cm^?1 for the sample comprising of 30 wt% NH₄Br. X-ray diffraction (XRD) patterns reveal that PVA-chitosan with 30 wt% NH₄Br exhibits the most amorphous structure. Thermogravimetric analysis (TGA) reveals that the electrolytes are stable until ～260 °C. The conductivity variation can also be explained by field emission scanning electron microscopy (FESEM) study. Dielectric properties of the electrolytes follow non-Debye behavior. The conduction mechanism of the highest conducting electrolyte can be represented by the correlated barrier hopping (CBH) model. From linear sweep voltammetry (LSV) result, the highest conducting electrolyte is electrochemically stable at 1.57 V.