Microstructure and luminescence of transparent glass ceramic containing Er:BaF2 nano-crystals

Transparent BaF₂-SiO₂ glass ceramics doped with different content of Er³⁺ were prepared by sol-gel method. The microstructural evolution of the samples was studied with X-ray diffraction (XRD), transmission electron microscope (TEM), absorption and infrared spectra (IR). BaF₂ nano-crystals with 2-15 nm in size, depending on the crystallization temperature, distributed homogeneously among the amorphous silica matrix. The BaF₂ lattice parameters decreased with the increasing of Er³⁺ doping, indicating the incorporation of Er³⁺ into nano-crystals, which was further confirmed by energy dispersive X-ray spectroscopy (EDS) and absorption spectra analysis. The upconversion emissions of Er³⁺ emerged under the excitation at 980 nm for glass ceramic heat-treated at 800 °C.     

Infrared high temperature spectra of aluminium chloride and related species

Isothermal cells of nickel with diamon windows were used to study various melts and vapours by infrared emission, transmission and reflectance techniques in the 860 to 300 K range with an evacuable Fourier transform spectrometer.IR vapour spectra of AlX₃ (X = Cl, Br, I) and GaCl₃ in transmission and emission were measured between 700 and 50 cm^?1. A comparable signal/noise ratio between the transmission and emission spectra was obtained above 200 cm^?1, below 200 cm^?1 the transmission spectra had better quality. The dimer and monemer spectra were assigned in terms of $\text{D}$_2h and $\text{D}$_3h symmetry, respectively, and compared with earlier Raman and IR matrix isolation data.Emission spectra of chloroaluminates AlkAlCl₄ (Alk = Li, Na, K, Rb, Cs) were recorded as melts between 1500 and 50 cm^?1. Increasing distortion of the tetrahedral AlCl^?₄ ion in the series Cs<Rb<K<Na<Li was observed. Emission spectra of AlkAl₂Cl₇ (Alk = Li, Na, K, Cs) indicate $\text{D}$_3d symmetry for Al₂Cl^?₇ with a linear Al-Cl-Al bridge as proposed from earlier Raman data. As a demonstration of reflectance technique an IR spectrum of ZnAl₂Cl₈ at ambient temperature is presented.     

A highly selective and sensitive dopamine and uric acid biosensor fabricated with functionalized ordered mesoporous carbon and hydrophobic ionic liquid

An ordered mesoporous carbon material functionalized with carboxylic acid groups was synthesized. It was characterized by powder X-ray diffraction, transmission electron microscopy, Fourier transform IR spectroscopy and N₂ adsorption/desorption. Furthermore, this material was used to modify an electrode surface combined with a hydrophobic ionic liquid. The functionalized ordered mesoporous carbon/ionic liquid gel modified electrode shows excellent electrocatalytic performances for the oxidation of dopamine, uric acid and ascorbic acid. The presence of the ionic liquid promotes the electron transfer. Linear responses for dopamine and uric acid were obtained in the ranges of 0.1 to 500 μM and from 0.1 to 100 μM with detection limits of 4.1 and 2.5 nM (signal-to-noise ratio of 3), respectively, under optimum conditions. A quick and sensitive biosensor based on functionalized ordered mesoporous carbon and an ionic liquid has been developed for the first time for the detection of dopamine and uric acid in the presence of a large amount of ascorbic acid.     

Influence of xenon difluoride on the optical properties of fluorozirconate and fluorohafnate glasses

To study the effect of xenon difluoride as a fluorinating agent on optical properties of glasses in ZBLAN (ZrF₄–BaF₂–LaF₃–AlF₃–NaF) and HBLAN (HfF₄–BaF₂–LaF₃–AlF₃–NaF) systems, their optical transmission in the range from UV to IR was investigated. The treatment of the initial fluorides with XeF₂ was shown to lead to a broadening of the transmission region of the obtained glasses both in the UV and IR ranges. Moreover, the treatment of the batch with xenon difluoride leads to the removal of oxygen-containing impurities that absorb in the region of 2.8 μm.     

Temperature dependence of the optical properties of liquid benzene in the infrared between 25 and 50 degrees C

The vibrational properties of benzene have long been a topic of interest. A recent comparison presented in the literature of the liquid and gas intensities at 25 degrees C have revealed some intriguing results regarding how the interaction between the hydrogens and the neighbouring pi-clouds in the liquid affect the vibrational intensities. To gain insight into the effect of temperature on the optical properties of liquid benzene and these interactions, the optical constants of liquid benzene have been determined through transmission measurements between 7,400 and 800 cm(-1). The spectra were measured in cells with KBr windows over a path length range of 15-1,000 microm and were collected over a temperature range of 30-50 degrees C in 5 degrees C increments. Variations in the imaginary molar polarizability spectra are examined and compared to a similar study of liquid toluene completed several years ago.     

Hydrothermal synthesis of nanocrystalline ZnSe: An in situ synchrotron radiation X-ray powder diffraction study

The hydrothermal synthesis of nanocrystalline ZnSe has been studied by in situ X-ray powder diffraction using synchrotron radiation. The formation of ZnSe was studied using the following starting mixtures: Zn+Se+H₂O (route A) and ZnCl₂+Se+H₂O+Na₂SO₃ (route B). The route A experiment showed that Zn powder starts reacting with water at 134 °C giving ZnO and H₂ followed by the formation of ZnSe which takes place in temperature range from 167 to 195 °C. The route B experiment shows a considerably more complex reaction path with several intermediate phases and in this case the formation of ZnSe starts at 141 °C and ZnSe and Se were the only crystalline phases observed at the end of the experiment where the temperature was 195 °C. The sizes of the nanocrystalline particles were determined to 18 and 9 nm in the route A and B experiments, respectively. Nanocrystalline ZnSe was also synthesized ex situ using the route A and B methods and characterized by conventional X-ray powder diffraction and transmission electron microscopy. An average crystalline domain size of ca. 8 nm was determined by X-ray powder diffraction in fair agreement with TEM images, which showed larger aggregates of nanoparticles having approximate diameters of 10 nm. Furthermore, a method for purification of the ZnSe nanoparticles was developed and the prepared particles showed signs of anisotropic size broadening of the diffraction peaks.     

Infrared study of phases III,IV and V of NH4NO3

Polarized transmission and reflection IR spectra of single crystal samples were recorded. Thin films of NH₄NO₃ on BaF₂ substrate were used to study the symmetric stretch and asymmetric stretch region of the NH⁺₄ ion, as well as the NH⁺₄ deformation and NO⁻₃ asymmetric region. Assignments based on factor group analysis are given. Possible coupling between NH⁺₄ and N⁻₃ ions is discussed and the degrees of motion of the two different ion groups are shown to be related to the stabilities of the crystal structures. Our results support the suggestion that a phase VII exists at low temperature.     

Free energy in vertically aligned liquid crystal mode

Vertical alignment (VA) is a widely applied operation mode for liquid crystal displays. To achieve optimum brightness, the electrode of VA is often patterned with fish-bone fine slits to generate fringe field, so the negative liquid crystal aligns along the fine slits when the electric field is applied. VA is usually simply modelled by the bend geometry along the cell gap. However, defects, domain boundaries and periodical splay induced by the fine slits also exist in real pixels and disturb the liquid crystal alignment. Polymer-stabilised VA test cells with various fine slit pitches which lead to various strength of fringe field were fabricated to observe the deformation of liquid crystal. Then the models of liquid crystal deformation nearby the defects and in the fine slit area were proposed to calculate the electromagnetic (f_EM) and elastic free energy (f_elastic). The results show that the key factor to regulate f_EM and f_elastic is the pitch of the fine slits, and the optimum liquid crystal alignment is obtained when f_EM and f_elastic are equal. The models are useful for further investigation on the dynamics of liquid crystal alignment and applications in industrial products.     

Interaction of [Mo6Cl14]2− with H2Se: Selective Preparation of [Mo6SeCl13]3−

Reaction of [Mo₆(μ₃-Cl)₈Cl₆]²⁻ with H₂Se, generated in situ from ZnSe and 4 M HCl under hydrothermal conditions lead to the substitution of one or two bridging chlorides, depending on the reagents ratio. With the Mo₆/ZnSe 1:3 molar ratio [Mo₆(μ₃-SeCl₇)Cl₆]³⁻ forms selectively in high yield. Further substitution is more hindered, and even at 1:20 cluster-to-selenide molar ratio a mixture of [Mo₆(μ₃-SeCl₇)Cl₆]³⁻ and [Mo₆(μ₃-Se₂Cl₆)Cl₆]⁴⁻ is formed. The products were characterized by X-ray, Raman spectra and electrospray ionization mass spectrometry.     

Molecular structure and vibrational spectra of trimethylarsenite

The molecular structure and vibrational spectra of trimethylarsenite were studied by gas phase electron diffractometry and IR and Raman spectroscopv. The configuration of the O-methyl groups with respect to the lone electron pair of the arsenic atom is established to be close to gosh-gosh-trans. The main geometrical parameters are: bond lengths (r_a, Å) As-O 1.780, C-0 1.451, and C-H 1.101; bond angles (deg) As-O-C 115.0, O-As-0 99.5, and O-C-H 115.3. The experimental IR and Raman spectra were obtained for pure liquid and CCl₄ solution. The frequencies and forms of normal vibrations were calculated.     

Hydrothermal synthesis and characterization of Nd-doped ZnSe nanoparticles with enhanced visible light photocatalytic activity

In the present study, Nd³⁺-doped ZnSe nanoparticles with variable Nd contents were successfully synthesized via a hydrothermal process using Neodymium (III) chloride hexahydrate as the doping source. X-ray diffraction, UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy and transmission electron microscopy were used for characterization of the synthesized nanoparticles. It was confirmed by the DRS analysis that both of the undoped and Nd-doped ZnSe samples had significant optical absorption in the visible light range. The photocatalytic performance of as-synthesized nanoparticles was investigated towards the decolorization of C. I. Acid Orange 7 solution under visible light irradiation. Results indicated that the loading of Nd dopant into ZnSe nanoparticles significantly enhanced the photocatalytic activity of pure ZnSe with increasing Nd loading up to 6 mol% (color removal efficiency of 24.31 % for ZnSe and 84.20 % for Nd_0.06Zn_0.94Se after 120 min of treatment) and then the photocatalytic activity began to decrease.     

In situ evaluation of breast cancer cell growth with 3D ATR-FTIR spectroscopy

A 3D attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy is applied to the in situ monitoring of the growth of breast cancer cell (MCF-7) on a ZnSe surface. The good biocompatibility of the ZnSe crystal results in a tight adhesion of the cells on the surface, with corresponding remarkable IR signals. The series spectrum curves are corresponding to each stage of the cell growth, elucidating the distinguishing phase of the cell cycle. The characteristic absorbance bands of MCF-7 breast cancer cells shift in comparison to the spectra of breast normal cells. However, no changes are observed as compared to the spectra of dead cells with those of the live cells.     

Study of electrodeposited zinc selenide (ZnSe) nanostructure thin films for solar cell applications

Electrodeposition approach was used to grow the ZnSe nanostructure on indium doped tin oxide (ITO) layered glass substrate. Due to low cost and high degree of absorption, binary semiconductors made from chalcogens such as CdSe, ZnO, ZnS and ZnSe provide significant features in photovoltaic and photoelectrochemical cells. The structural and morphological properties of deposited nanostructures were examined by XRD and SEM. X-ray diffraction analysis informed about cubic structure with a preferred orientation and the calculated crystal size was approximately 75 nm. The optical properties were examined by UV–visible absorbance spectra and optical band gap was measured using Tauc plot. The deposited ZnSe nanostructure has direct band gap ∼2.52 eV at room temperature which was less than 2.82 eV which is the band gap of bulk ZnSe. Investigations also focused on additional qualities like excellent optical transmission, low electrical resistance, and good photosensitivity. Because of the presence of defect states in the deposited nanostructure, the band gap energy is smaller than that of bulk material. The current-voltage characteristics were measured in dark mode and under illumination of normal tungsten filament light and LED. There was notable change in the current for both normal light and LED in comparison to dark mode. The findings of all the characterization methodologies suggested that for the production of solar cells low cost ZnSe may be used as an alternative environment friendly Cd-free window layer.     

Adsorption of gases on binary and multicomponent semiconductors of the ZnSe-CdTe system

Adsorption of carbon monoxide(II) and oxygen on powders and nanofilms of solid solutions and binary compounds of the ZnSe-CdTe system was studied volumetrically, and by piezoquartz microweighing and IR spectroscopy of multiple disturbed complete internal reflections. The mechanisms and principles of adsorption were established in dependence on the conditions of the habitus of an experimental sample and the composition of the system’s semiconductors, based on an analysis of IR spectra; the thermodynamic and kinetic characteristics of adsorption; experimental dependences αp = f(T), αT = f(P), and αT = f(t); and the acid-base and other physicochemical characteristics of adsorbents and the electron nature of adsorbate molecules. Conclusions drawn earlier as to the retention of local active centers on the surface of a diamond-like semiconductor (which are responsible for adsorption and catalytic processes) upon a change in the habitus of a sample were confirmed. Certain features in the behavior of solid solutions (ZnSe) _x (CdTe)_{1 − x} were revealed alongside commonalities with binary compounds (ZnSe, CdTe), testifying to the presence of critical points on “adsorption characteristics-composition” diagrams. The most active adsorbents (with respect to CO and O₂) were discovered on the basis of these diagrams, which were used in creating highly sensitive and selective sensors.     

Synthesis,crystal structure,and magnetic properties of 1D Azido-bridged copper(II) complex

A novel copper(II)-azide complex of [Cu₂(DMAP)₂(μ-1,1-N₃)₂(μ-1,3-N₃)₂]_n (DMAP = 4-(dimethylamino)pyridine) has been synthesized and characterized by IR spectra, X-ray diffraction, elemental analysis, and magnetism measurement. The complex reveals a 1D ladder-like chain structure, in which two μ-1,1-N₃ and two μ-1,3-N₃ bridges form a dimeric unit of [Cu₂(DMAP)₂(μ-1,1-N₃)₂(μ-1,3-N₃)₂] and are then connected to each other from the tail nitrogens of two asymmetric μ-1,3-N₃ bridges to generate a chain structure that stacks in the cell to construct the 3D crystal. The Cu atom is five-coordinated by azide anions to form a distorted square-pyramid of CuN₅ (τ = 0.2667). Magnetic susceptibility of complex exhibits a ferromagnetic interaction between the copper(II) ions through two kinds of azido-bridges. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Sonochemical synthesis and luminescence properties of single-crystalline BaF2:Eu nanospheres

BaF₂ nanocrystals doped with 5.0 mol% Eu³⁺ has been successfully synthesized via a facile, quick and efficient ultrasonic solution route employing the reactions between Ba(NO₃)₂, Eu(NO₃)₃ and KBF₄ under ambient conditions. The product was characterized via X-ray powder diffraction (XRD), scanning electron micrographs (SEM), transmission electron microscopy (TEM), high-resolution transmission electron micrographs (HRTEM), selected area electron diffraction (SAED) and photoluminescence (PL) spectra. The ultrasonic irradiation has a strong effect on the morphology of the BaF₂:Eu³⁺ particles. The caddice-sphere-like particles with an average diameter of 250 nm could be obtained with ultrasonic irradiation, whereas only olive-like particles were produced without ultrasonic irradiation. The results of XRD indicate that the obtained BaF₂:Eu³⁺ nanospheres crystallized well with a cubic structure. The PL spectrum shows that the BaF₂:Eu³⁺ nanospheres has the characteristic emission of Eu^{3+ 5}D₀-⁷F_J (J=1-4) transitions, with the magnetic dipole ⁵D₀-⁷F₁ allowed transition (590 nm) being the most prominent emission line.     

Raman and FT IR ATR study of diethylsulfoxide/water mixtures

The Raman and FT IR ATR spectra of diethylsulfoxide (DESO)-water mixtures in the SO and C-H stretching vibration regions at different molar ratios are considered. Noticeable changes are observed in the ν_SO region, suggesting the existence of strong H-bonds between DESO and water molecules; on the contrary the ν_CH bands change only in a less extent, supporting the existence of SO?HC hydrogen bonds in pure DESO that gradually break in the presence of water. In addition, FT IR measurements confirm the existence of ‘free’ SO group at low concentrations of DESO.The results obtained are well explainable in frame of the cluster-structure model of liquid water.     

Infrared optical constants, dielectric constants, molar polarizabilities, transition moments, dipole moment derivatives and Raman spectrum of liquid cyclohexane

Previous studies have been done in this laboratory focusing on the optical properties of several liquid aromatic and aliphatic hydrocarbons in the infrared. The current study reports the infrared and absorption Raman spectra of liquid cyclohexane. Infrared spectra were recorded at 25 °C over a wavenumber range of 7400–490 cm⁻¹. Infrared measurements were taken using transmission cells with pathlengths ranging from 3 to 5000 μm. Raman spectra were recorded between 3700 and 100 cm⁻¹ at 25 °C using a 180° reflection geometry. Ab initio calculations of the vibrational wavenumbers at the B3LYP/6311G level of theory were performed and used to help assign the observed IR and Raman spectra. Extensive assignments of the fundamentals and binary combinations observed in the infrared imaginary molar polarizability spectrum are reported. The imaginary molar polarizability spectrum was curve fitted to separate the intensity from the various transitions and used to determine the transition moments and magnitudes of the derivatives of the dipole moment with respect to the normal coordinates for the fundamentals.     

Modifying infrared scattering effects of single yeast cells with plasmonic metal mesh

The scattering effects in the infrared (IR) spectra of single, isolated bread yeast cells (Saccharomyces cerevisiae) on a ZnSe substrate and in metal microchannels have been probed by Fourier transform infrared imaging microspectroscopy. Absolute extinction [(3.4±0.6)×10(-7) cm(2) at 3178 cm(-1)], scattering, and absorption cross sections for a single yeast cell and a vibrational absorption spectrum have been determined by comparing it to the scattering properties of single, isolated, latex microspheres (polystyrene, 5.0 μm in diameter) on ZnSe, which are well modeled by the Mie scattering theory. Single yeast cells were then placed into the holes of the IR plasmonic mesh, i.e., metal films with arrays of subwavelength holes, yielding "scatter-free" IR absorption spectra, which have undistorted vibrational lineshapes and a rising generic IR absorption baseline. Absolute extinction, scattering, and absorption spectral profiles were determined for a single, ellipsoidal yeast cell to characterize the interplay of these effects.     

Structural,thermal, and impedance properties of a gel polymer electrolyte containing ionic liquid

The gel polymer electrolytes composed of ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF₄) and the copolymer of acrylonitrile (AN), methyl methacrylate (MMA), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) are synthesized and characterized by FT‐IR spectra, TGA, DSC, and AC impedance measurements. IR spectra show that there is an interaction between PEO side chains of the copolymer and imidazolium cations. TGA measurements indicate that the gel polymer electrolytes are stable until 120°C. By using the equivalent circuit proposed, the experimental data and the simulated data fit very well. The bulk resistance R_b is found to decrease with the increase in BMImBF₄ content. Copyright © 2009 John Wiley & Sons, Ltd.