Comparative study on modification of single wall carbon nanotubes by sodium dodecylbenzene sulfonate and melamine sulfonate superplasticiser

In this work, the results of synthesis and characterization of single wall carbon nanotubes (SWCNTs) functionalized by two surfactants (sodium dodecylbenzene sulfonate and melamine sulfonate superplasticiser) have been presented. The properties of pristine and modified SWCNTs have been compared by different techniques: Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Raman analysis reveals the changes in vibrational spectra of SWCNTs after modification by different surfactant molecules. FTIR analysis has shown the presence of sulfonate group which is strong evidence for nanotube modification. AFM analysis has shown separation of big single wall carbon nanotube bundles into thin bundles of them.     

The effect of thermal annealing and laser irradiation on the microstructure of vanadium oxide nanotubes

The microstructure of vanadium oxide nanotubes (VONTs) have been characterized using FTIR spectroscopy and Raman spectroscopy. The temperature effects on the VONTs were studies by changing the laser irradiation power and thermal annealing temperature in air. Raman spectroscopy studies showed that the VONTs could be decomposed even at low laser power irradiation. Also, together with scanning electron microscopy, it was found that thermal annealing in air could lead to the collapse of the tubular structure and convert the nanotubes into V₂O₅ nanoparticle. It was found that the thermal stability of VONTs was relatively low and the tubular morphology was destroyed at temperatures higher than 300 °C. The spectroscopic analyses showed that the Raman signature of the VONTs could be established for probing tubular structure.     

Raman scattering studies of the Ge-In sulfide glasses

Room temperature Raman scattering measurements of samples of the (1−x)GeS₂-xIn₂S₃ (x=0.00-0.35) system have been conducted together with the FTIR transmission spectra of partial samples. Based on the Raman scattering and FTIR transmission spectra of the prepared defect spinel polycrystalline In₂S₃, the additional peaks at 306 and 245 cm⁻¹ were ascribed to the local symmetric stretching vibration of InS₄ tetrahedra and InS₆ octahedra, respectively. According to the Raman scattering spectral evolution of the Ge-In sulfide glasses, the microstructure of the studied glasses was considered to be that S₃Ge-GeS₃ and S₃In-InS₃ ethane-like units originated from the sulfur deficient with the addition of In₂S₃ are homogeneously dispersed in a disordered polymer network formed by GeS₄, InS₄ tetrahedra and a small quantity of InS₆ octahedra interconnected by sulfur bridges.     

Analysis of ferroelectric switching in sodium nitrite:poly(vinyl alcohol) nanocomposite films

The Fourier transform infrared (FTIR) spectra and switching current response in sodium nitrite:poly(vinyl alcohol) nanocomposite films have been studied as a function of composition of NaNO₂. The switching current data fitted well to infinite-grain model (IGM) in the region t<t _s and to finite-grain model (FGM) in the region t≥t _s . The microscopic parameters like the dimensionality, the domain wall velocity, and the nucleation rate have been evaluated which provide more physical insight of the switching phenomena in the composite films. The polarization current and nucleation rate are optimum in 50 wt.% composite film and have been discussed in terms of grain size and strain variations with the composition. The effect of applied field and pulse width variation on the switching behavior of 50 wt.% composition has also been studied. The exponential field dependence of the domain wall velocity and the nucleation rate indicate that nucleation mechanism is responsible for switching phenomena in the composite films. The writing pulse width affects significantly on the switching behavior of the composite films.     

The Vibrational Spectra and Normal Coordinate Analysis of Semiconducting Y2BaCuO5

Both infrared (FTIR) and Raman spectra have been measured for the green semiconducting Y₂BaCuO₅ (2:1:1) in the Y-Ba-Cu-O system. Factor group analysis and normal-coordinate-analysis calculations have been conducted for this phase in order to determine the symmetries, the wavenumber locations and the eigenvector nature of its first-order modes of vibration along with the appropriate set of modified GVF force constants. The predicted vibrational spectral results are in good agreement with the experimentally observed FTIR and Raman spectral data. The generated force constants are interpreted along with those for related phases on the basis of structure.     

Preparation and characterization of Ag nanoparticle-embedded polymer electrospun nanofibers

Poly (vinyl alcohol) (PVA) and poly (vinyl pyrrolidone) (PVP) nanofibers embedding Ag nanoparticles (5–18 nm) have been prepared successfully by electrospinning at room temperature. Scanning electron microscope (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform IR spectra (FTIR), and Raman scattering were used to characterize the structure and properties of Ag nanoparticle-embedded PVA and PVP nanofibers before and after heat treatment at different temperature. The antibacterial activity of Ag nanoparticle-embedded PVP nanofibers after heat treatment was also tested, which indicated that the biological activity of yeast cells was effectively inhibited by these Ag nanoparticle-embedded PVP nanofibers.     

Structural and thermal studies of PVA:NH4I

Proton-conducting polymer electrolytes based on poly vinyl alcohol (PVA; 88% hydrolyzed) and ammonium iodide (NH₄I) has been prepared by solution casting method with different molar ratios of polymer and salt using DMSO as solvent. DMSO has been chosen as a solvent due its high dielectric constant and also its plasticizing nature. The ionic conductivity has been found to increase with increasing salt concentration up to 25 mol% beyond which the conductivity decreases and the highest ambient temperature conductivity has been found to be 2.5×10⁻³ S cm⁻¹. The conductivity enhancement with addition of NH₄I has been well correlated with the increase in amorphous nature of the films confirmed from XRD and differential scanning calorimetry (DSC) analyses. The temperature-dependent conductivity follows the Arrhenius relation. The polymer-proton interactions have been analyzed by FTIR spectroscopy.     

Structural and electronic properties of the LiNiPO4 orthophosphate

Microcrystalline LiNiPO₄ powders have been prepared by solid-state reaction using various precursors. Characterization of the structure and morphology of powders was performed using XRD, SEM, HRTEM, Raman, and FTIR. The electronic properties of materials were investigated by SQUID and ESR. The LiNiPO₄ material adopts the olivine-like structure (Pnma S.G.). Analysis of the Raman and FTIR spectra figures out, with the aid of a molecular vibration model, the bonding between NiO₆ octahedral and (PO₄)^3? tetrahedral groups. The electronic configuration and the local cationic arrangement are confirmed by magnetic susceptibility and electron spin resonance spectroscopy.     

Raman spectroscopy study of REH3 under pressure

The Raman spectroscopic studies of two rare earth trihydrides: Y H₃, HoH₃, have been performed in the pressure range from ambient up to 16 GPa and 25 GPa respectively. For the first time samples of REH₃ in the form of powder have been studied by Raman spectroscopy using the Diamond Anvil Cell (DAC) technique. A rapid decrease of Raman activity has been observed for the hydrides under pressure values in the vicinity of structural phase transition. Metallization as a possible reason for the observed dramatic change of the REH₃ Raman activity has been discussed.     

Facile in situ hydrothermal synthesis of BiVO4/MWCNT nanocomposites as high performance visible-light driven photocatalysts

Visible-light responsive monoclinic BiVO₄/MWCNT nanocomposites were facilely prepared via an in situ hydrothermal method by using sodium dodecyl sulfonate (SDS) as a guiding surfactant. The as-prepared BiVO₄/MWCNT nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), the Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy. The results showed that the hydrothermal temperature and adding SDS had significant influence on the morphology and size of BiVO₄. The photocatalytic activities of BiVO₄/MWCNT nanocomposites were investigated by degrading methylene blue (MB) under visible-light irradiation. Remarkable enhancement in photodecomposition of MB was observed with BiVO₄/MWCNT composite compared with bare BiVO₄ particles. This improvement of photocatalytic was attributed to the effective charge transfer from BiVO₄ nanocrystals to MWCNT, which promoted the migration efficiency of photogenerated electron–hole. Furthermore, a possible mechanism for the photocatalytic oxidative degradation was also discussed.     

Synthesis and characterization of spinel LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles prepared by high-energy milling and hydrothermal method

Spinel LiMn₂O₄ has been known to be a technologically important, environmental-friendly, and low-cost cathode material used in Li-based rechargeable batteries, and it is also widely available. Nanoparticle spinel LiMn₂O₄ has been synthesized by the top-down, high-energy milling, and hydrothermal methods. SEM images, X-ray diffraction patterns, and neutron high-resolution powder diffraction patterns have confirmed the nanocrystalline nature of the spinel LiMn₂O₄ samples. Raman and Fourier transform infrared (FTIR) measurements show typical absorption and vibration spectra typical for the spinel LiMn₂O₄ showing the formation of various metallic bonds in the sample. The strongest Raman and FTIR signals come from the higher frequency region, with weaker signals appearing in the lower frequency range.     

微波等离子体化学气相沉积法制备C3N4薄膜的结构研究

采用微波等离子体化学气相沉积法,用高纯氮气(99.999%)和甲烷(99.9%)作反应气体,在单晶Si(100)基片上沉积C₃N₄薄膜.利用扫描电子显微镜观察薄膜形貌,表明薄膜由密排的六棱晶棒组成.X射线衍射和透射电子显微镜结构分析说明该薄膜主要由β-C₃N₄和α-C₃N₄组成,并且这些结果与α-C₃N₄相符合较好.由虎克定律近似关 关键词： 3N₄')" href="#">C₃N₄ 微波等离子体化学气相沉积法 薄膜沉积     

Structural and electrical properties of pure and NaBr doped poly (vinyl alcohol) (PVA) polymer electrolyte films for solid state battery applications

A sodium ion conducting polymer electrolyte based on poly (vinyl alcohol) (PVA) complexed with sodium bromide (NaBr) was prepared using solution cast technique. Several experimental techniques such as XRD, FTIR, SEM, temperature-dependant conductivity and transference number measurements have been performed. XRD and FTIR studies confirm the complexation of salt with the polymer. Surface morphology was studied using Scanning Electron Microscopy. DC conductivity was measured in the temperature range of 303–373 K, and the conductivity was found to increase with the increase of dopant concentration as well as temperature. Transference number data suggests that the charge transport in this polymer electrolyte system is mainly due to ions. Using these polymer electrolyte films, electrochemical cells were fabricated with configuration Na/(PVA:NaBr)/V₂O₅ and Na/(PVA:NaBr)/(I2+C+electrolyte) and their discharge characteristics like open circuit voltage (OCV), short circuit current (SCC), power density, energy density were evaluated and compared. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Growth, structural, optical and electrical behavior of glycine potassium nitrate (GPN) crystal with non-linear optical response

New trapezoidal, non-linear optical crystals of glycine potassium nitrate (GPN) have been grown by slow cooling from solutions with an initial pH of 4.3. Chemical composition, phase formation and functional groups have been verified by CHN, EDAX, XRF, NMR, XRD, FTIR and Raman studies. UV studies show a much lower cut off wavelength (195 nm) compared to the much investigated glycine sodium nitrate (GSN). The powder SHG efficiency of GPN is found to be 0.6 times compared to that of potassium dihydrogen phosphate (KDP). Cut and polished crystals exposed to light indicate positive photoconductivity. Electrical conductivity studies show an activation energy of 0.16 eV and the dielectric loss is found to decay drastically at higher frequencies (1 MHz) which is desirable in electronic applications. Vickers microhardness studies indicate a Mayer's index value of 2.78. Well resolved, elongated and oriented etch pits have been observed on the side habit face (220) treated in glacial acetic acid for 5 s. Typical circular features resisting the formation of etch pits representing impurity elements have been observed on the cleavage faces. Moisture has been traced on the surface of the crystals subjected to heat treatment.     

A study of smalt and red lead discolouration in Antiphonitis wall paintings in Cyprus

The present analytical study focuses on the degradation phenomena observed in fifteenth century wall paintings of the Christ Antiphonitis monastery in Cyprus. Examination of ten fragments by means of optical microscopy (OM), scanning electron microscopy (SEM/EDS), μRaman and FTIR spectroscopy revealed smalt discolouration and loss, and transformation of red lead from orange Pb₃O₄ to black PbO₂. The chromatic changes have affected the aesthetic effect of the paintings insofar as these pigments were extensively used. The mechanisms of smalt weathering, i.e. leaching of alkali and formation of micro-cracks, are interpreted in relation to its chemical composition and to the aggressive environmental conditions. In addition, it is assumed that red lead degradation may have been induced not only by the effect of temperature, light and humidity but also by the presence of chlorine salts. These phenomena of pigment alteration and loss underline the unsuitability of smalt and minium on wall paintings, regardless of the painting technique (fresco, fresco-secco, secco).     

Paramagnetic susceptibilities, crystal field Stark energies and hyperfine properties of Eu in europium trifluoromethanesulfonate nonahydrate

Hexagonal single crystals of europium trifluoromethanesulfonate nonahydrate (EuTFMS) have been prepared. The paramagnetic susceptibility perpendicular to the symmetry axis (c-axis, χ_⊥) and the principal magnetic anisotropy (Δχ=χ_||−χ_⊥) were measured in the temperature range of 300-13 and 300-80 K, respectively. The paramagnetic susceptibility parallel to the c-axis (χ_||) was calculated using the values of χ_⊥ and Δχ. χ_|| and χ_⊥ increase slowly with decrease of temperature and below ∼93 K, χ_⊥ is more or less constant. But χ_|| levels off below ∼137 K. The calculated value of the effective magnetic moment (P_eff) of Eu³⁺ in the crystalline environment of EuTFMS decreases with lowering of temperature. The Raman and Fourier transform infrared (FTIR) spectra of EuTFMS were recorded in the wavenumber range of 10-1800 and 370-6000 cm⁻¹, respectively. A good theoretical simulation of the observed magnetic properties including the CF Stark energies of the ground term (⁷F) extracted from the Raman and FTIR spectra of Eu³⁺ in EuTFMS have been achieved using one electron crystal field (CF) analysis. The electronic specific heat and other relevant CF dependent hyperfine properties, viz, nuclear quadrupole splitting and hyperfine specific heat have been computed.     

Raman spectroscopic analysis of sulphur-doped TiO2 by co-grinding with TiS2

Doping sulphur into titania has been tried using TiS₂ as a doper based on the mechanically induced solid-state reaction between TiO₂ and TiS₂. The prepared samples have been characterized by X-ray diffraction (XRD), Raman spectroscopy and UV-Vis reflectance spectroscopy. Raman analysis, particularly has been proved to be effective in assessing the sulphur doping by correlating the oxygen deficiency of the doped oxide with the change of active Eg mode of rutile phase.     

Microwave-assisted synthesis and optical property of CdMoO4 nanoparticles

Microwave-assisted synthesis is a novel method used to synthesize CdMoO₄ nanoparticles in propylene glycol. The effects of reaction time and microwave power on phase, morphologies, and optical properties of CdMoO₄ nanoparticles were studied, using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and UV-visible spectroscopy. The present analyses proved that these crystalline powders were scheelite-type tetragonal structured CdMoO₄, with the crystallite size of 14-20 nm, and 4.51-4.73 eV band gaps, controlled by the synthetic conditions.     

Low-temperature vibrational properties of KGd(WO4)2: (Er, Yb) single crystals studied by Raman spectroscopy

Temperature-dependent polarized Raman spectra of KGd(WO₄)₂: (Er, Yb) single crystals have been analyzed over the 77-292 K temperature range. The A_g and B_g spectra obtained are discussed in terms of factor group analysis. The spectra have been found to reveal the bands related to internal and external vibrations of WO₄²⁻, WOW and WOOW molecular groups. Strong depolarization of the majority of the Raman bands has been observed in the whole temperature range. Some anomalies in the spectral parameters of selected Raman bands below 175 K have been discussed in terms of the local distortion of WO₄²⁻ ions in KGd(WO₄)₂: (Er, Yb) crystals.     

Raman spectra of samarium-fullerene intercalation compounds

Samarium-fullerene intercalation compounds of nominal composition Sm_xC₆₀ (x=1,2,…,6) have been synthesized by a solid-state reaction method. We obtain a Sm_2.75C₆₀ superconducting phase with orthogonal structure and a Sm₆C₆₀ phase with body-centered cubic structure. The broadening and weakening of Raman peaks of the Sm_xC₆₀ compounds are due to the distortion of C₆₀ and electron-phonon interaction. The Raman measurements reveal that the distortion of C₆₀ decrease in Sm_xC₆₀ (x=3,4,5) exposed to air, although the fulleride solids have transformed into an amorphous state. The Raman results also show that the distortion of C₆₀ is still very large in the Sm₆C₆₀ exposed to air, or the C₆₀ molecules have been destroyed and become some amorphous carbide.