The influence of Fe doping on the structural, magnetic and optical properties of nanocrystalline ZnO particles

We report the results of an investigation of Fe-doped nanocrystalline ZnO particles synthesized using the co-precipitation method with doping concentrations from 5 up to 31 at%. To understand how the dopant influenced the structural, magnetic and optical properties of nanocrystalline ZnO particles, X-ray diffraction, energy dispersive X-ray spectroscopy, infrared absorption spectroscopy, UV-vis spectroscopy, electron spin resonance spectroscopy (ESR) and vibrating sample magnetometer were employed. From the analysis of X-ray diffraction, our Fe-doped nanocrystalline ZnO particles are identified as having the wurtzite crystal structure and the unit cell volume increases with increasing doping concentrations. However, impurity phases are observed for Fe contents higher than 21 at%. Sample structures were further studied by infrared spectra, from which a broad and strong absorption band in the range of 400-700 cm⁻¹ and -OH stretching vibrational mode at approximately 3400 cm⁻¹ were observed. Ultraviolet-visible measurements showed a decrease in the energy gap with increasing Fe content, probably due to an increase in the lattice parameters. Magnetic measurements showed a ferromagnetic behavior for all samples. ESR results indicate the presence of Fe in both valence states Fe²⁺ and Fe³⁺.     

Raman spectroscopic study of synthetic reevesite and cobalt substituted reevesite (Ni,Co)6Fe2(OH)16(CO3)·4H2O

Raman spectroscopy, complemented with infrared spectroscopy of compounds equivalent to reevesite, formula (Ni,Co)₆Fe₂(OH)₁₆(CO₃)·4H₂O, with the ratio of Ni/Co ranging from 0 to 1, have been synthesised and characterised based on the molecular structure of the synthesised mineral. The combination of Raman spectroscopy with infrared spectroscopy enables an assessment of bands attributable to water stretching and brucite‐like surface hydroxyl units to be obtained. Raman spectroscopy shows a reduction in the symmetry of the carbonate anion, leading to the conclusion that the carbonate anion is bonded to the brucite‐like hydroxyl surface and to the water in the interlayer. Variation in the position of the carbonate anion stretching vibrations occurs and is dependent on the Ni/Co ratio. Water bending modes are identified in both the Raman and infrared spectra at positions greater than 1620 cm⁻¹, indicating that water is strongly hydrogen bonded to both the interlayer anions and the hydrotalcite surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Adsorption d'hydrogène entre 300 et 873 K sur un catalyseur Pt/MgO

Hydrogen adsorption on MgO-supported platinum was studied by thermal desorption and infrared spectroscopy at 300 and 800 K. For both temperatures, reversibly and irreversibly adsorbed species have been detected. At 300 K, reversible adsorption leads to the appearance of infrared bands at 2120 and 2060 cm^?1, attributed to terminal Pt-H species. Irreversibly adsorbed hydrogen has been detected by thermal desorption, whereas no infrared band was detected in the spectral range 4000–4750 cm^?1 for Pt/MgO sample. For hydrogen adsorption at 800 K, reversibly adsorbed hydrogen gave the same picture as for the 300 K adsorption. An additional form of irreversibly adsorbed hydrogen has been evidenced both by thermal desorption and infrared spectroscopy. This form corresponds to hydrogen strongly adsorbed on platinum and gives an infrared band at 950 cm^?1 which is characteristic of an hydrogen atom in interaction with more than one platinum atom (multicentered) species.     

Vibrational Spectroscopic Characterization of the Arsenate Mineral Barahonaite: Implications for the Molecular Structure

The mineral barahonaite is in all probability a member of the smolianinovite group. The mineral is an arsenate mineral formed as a secondary mineral in the oxidized zone of sulphide deposits. We have studied the barahonaite mineral using a combination of Raman and infrared spectroscopy. The mineral is characterized by a series of Raman bands at 863 cm^?1 with low wavenumber shoulders at 802 and 828 cm^?1. These bands are assigned to the arsenate and hydrogen arsenate stretching vibrations. The infrared spectrum shows a broad spectral profile. Two Raman bands at 506 and 529 cm^?1 are assigned to the triply degenerate arsenate bending vibration (F ₂, ν₄), and the Raman bands at 325, 360, and 399 cm^?1 are attributed to the arsenate ν₂ bending vibration. Raman and infrared bands in the 2500–3800 cm^?1 spectral range are assigned to water and hydroxyl stretching vibrations. The application of Raman spectroscopy to study the structure of barahonaite is better than infrared spectroscopy, probably because of the much higher spatial resolution.     

Raman spectroscopy of dawsonite NaAl(CO3)(OH)2

Raman spectroscopy both at 298 and 77 K complemented with infrared spectroscopy was used to study the structure of dawsonite. Previous crystallographic studies concluded that the structure of dawsonite was a simple one; however, both Raman and infrared spectroscopy show that this conclusion is incorrect. Multiple bands are observed in both the Raman and infrared spectra in the antisymmetric stretching and bending regions, showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the dawsonite structure. Multiple OH deformation vibrations centred around 950 cm⁻¹ in both Raman and infrared spectra show that the OH units in the dawsonite structure are non‐equivalent. Calculations using the position of the Raman and infrared OH stretching vibrations enabled estimates of the hydrogen‐bond distances of 0.2735 and 0.27219 pm at 298 K, and 0.27315 and 0.2713 pm at 77 K to be made. This indicates strong hydrogen bonding of the OH units in the dawsonite structure. Copyright © 2007 John Wiley & Sons, Ltd.     

Radiocarbon dating by infrared laser spectroscopy

A tunable diode laser and a multipass optical cell are used to investigate the feasibility of performing radiocarbon dating by means of infrared spectroscopy. We show that the detection of¹⁴CO₂ at concentrations of¹⁴C/¹²C?10^?12 is not limited by interferences from the background of normal CO₂ molecules, provided the gas sample is cooled. Using short-time constants, the present sensitivity of the infrared technique is comparable to that of an ideal disintegration counter. The experimental results are extrapolated to long time constants to demonstrate that radiocarbon dating by infrared spectroscopy is feasible, and that carbon samples with a mass of less than 1 gm can be dated by this technique.     

Structural Characterization of Hydroxyl-Terminated Polybutadiene-Bound 2, 2-Thiobis(4-methyl-6-tert-butylphenol) and Its Thermo-Oxidative Aging Resistance for Natural Rubber Vulcanizates

A novel polymeric antioxidant, hydroxyl-terminated polybutadiene-bound 2,2-thiobis(4-methyl-6-tert-butylphenol) (HTPB-IPDI-TPH), was prepared by binding 2, 2-thiobis(4-methyl-6-tert-butylphenol) (TPH) onto hydroxyl-terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI). Fourier-transform infrared spectroscopy (FTIR), ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR), and gel permeation chromatography (GPC) were used to characterize the structure of HTPB-IPDI-TPH. The thermal stability of HTPB-IPDI-TPH was studied by thermogravimetry analysis (TGA). The effect of HTPB-IPDI-TPH on thermo-oxidative aging resistance of NR vulcanizates was investigated, and the mechanism of thermo-oxidative aging resistance was preliminarily discussed. The results showed that HTPB-IPDI-TPH contributed better thermal stability and thermo-oxidative aging resistance to NR vulcanizates than TPH. The thermo-oxidative aging resistance of HTPB-IPDI-TPH was more remarkable in the later stage of aging. Attenuated total-reflectance Fourier-transform infrared spectroscopy (FTIR-ATR) analysis showed that the relative content of carbonyl groups of NR vulcanizate with HTPB-IPDI-TPH was obviously lower than that with TPH after thermo-oxidative aging. It is suggested that ?NHCOO? groups in HTPB-IPDI-TPH enhanced the ability of trapping alkyl peroxide radicals.     

Optical properties of BiFeO<Subscript>3</Subscript> ceramics in the frequency range 0.3–30.0 THz

Reflection and transmission infrared spectra of BiFeO₃ ceramic samples have been measured using submillimeter spectroscopy (on a backward-wave tube spectrometer) and Fourier-transform infrared spectroscopy in the frequency range from 5 to 1000 cm⁻¹ at temperatures in the range from 10 to 500 K. New resonant modes (probably, magnetic in nature) with the eigenfrequencies decreasing with an increase in the temperature have been recorded in the range 10–30 cm⁻¹ by IR spectroscopy for the first time. An additional absorption with a fairly large dielectric contribution has been revealed in the range 30–60 cm⁻¹. It has been demonstrated that the corresponding oscillators couple with both the lowest frequency phonon mode and the magnetic subsystem.     

Synthesis and characterization of core-shell structured SiO2@YVO4:Yb,Er microspheres

In this paper, the core-shell structured SiO₂@YVO₄:Yb³⁺,Er³⁺ microspheres have been successfully prepared via a facile sol-gel process followed by a heat treatment. X-ray diffraction, field emission scanning electron microscopy, energy disperse X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence spectra were used to characterize the samples. The results reveal that the SiO₂ spheres have been successfully coated by YVO₄:Yb³⁺,Er³⁺ phosphors to form core-shell structures and the size of obtained microspheres has a uniform distribution. Additionally, the samples exhibit bright green luminescence under the excitation of a 980 nm laser diode. The photoluminescence intensity increases with the number of coatings. These core-shell structured SiO₂@YVO₄:Yb³⁺,Er³⁺ microspheres may have great potential in the fields of infrared detection and display devices.     

Red, green, and blue lanthanum phosphate phosphors obtained via surfactant-controlled hydrothermal synthesis

A new solution route for the obtainment of highly pure luminescent rare-earth orthophosphates in hydrothermal conditions was developed. By starting from soluble precursors (lanthanide tripolyphosphato complexes, i.e. with P₃O₁₀⁵⁻ as a complexing agent and as an orthophosphate source) and by applying surfactants in a water/toluene medium, the precipitations are confined to reverse micelle structures, thus yielding nanosized and homogeneous orthophosphates. The method was employed to obtain lanthanide-activated lanthanum phosphates, which can be applied as red (LaPO₄:Eu³⁺), green (LaPO₄:Ce³⁺,Tb³⁺) and blue (LaPO₄:Tm³⁺) phosphors. The produced materials were analyzed by powder X-ray diffractometry, scanning electron microscopy, infrared spectroscopy and luminescence spectroscopy (emission, excitation, lifetimes and chromaticity coordinates).     

Study on Infrared Spectral Radiance by Remote Fourier Transform Infrared Spectroscopy

Abstract

Infrared emission spectra emitted by high luminosity infrared pyrotechnics have been observed remotely using the Fourier transform infrared spectroscopy. The primary purpose of the study is to determine infrared spectral radiance distribution, their time—resolved spectra and integrated emission energy. The spectra have been recorded between 4000 – 800cm^?1 region with spectral resolution of 4cm^?1. The study is very important for many applications.     

Optical Characterization of Donor Doped Ternary Alloy Ga1-xNxAs and GaN-Ga1-xNxAs MQW by Using Infrared Fourier Transform Spectroscopy

In this work polarized infrared Fourier transform spectroscopy is employed to study the electronic and optical properties of doped Ga_1-xN_xAs ternary alloy and GaN-Ga_1-xN_xAs MQW. We have analyzed the far infrared spectra of GaN-GaNAs MQW by using a simple macroscopic theory base on effective medium approximation model. The dispersion curve of coupled LO phonon- plasmon modes were calculated from the polarized infrared reflectivity data. The GaNAs layer shows two-mode behavior in the infrared spectral range, a GaAs-like and a GaN-like sublattices. We detect the transverse optic phonon of GaN sublattice around 475 cm^-1. The origin of the sharp feature in p-polarization reflectivity about 300 cm^-1 as well as the dip at LO phonon frequency of GaAs sublattice are due to Brewster mode. The Brewster mode is couple strongly to plasmon mode. Attenuated total reflection spectroscopy has been used to excite and investigate surface plasmon and surface polariton.     

Poly(N-methylaniline)/Montmorillonite Composite: Chemical Synthesis,Characterization, and Application in Water Treatment

Poly(N-methylaniline)/montmorillonite (PNMA/MMT) composite particles were obtained by using a simple in situ chemical oxidative polymerization method in hydrochloric acid solutions. Fourier transform infrared (FTIR) spectra, UV-visible absorption spectra and scanning electron microscopy (SEM) were carried out to characterize the as-prepared PNMA/MMT composite. On the basis of spectroscopy and morphology analysis, the probable polymerization mechanism was proposed. The potential application of PNMA/MMT composite for removal of heavy metal ions, such as Cu²⁺ and Zn²⁺, in aqueous solution was also investigated.     

Mössbauer-Effect Spectra of Iron Phosphonate Compounds

The iron phosphonates, tris (methyl methylphosphonate) iron (III) [Fe(MMP)³]; tris (ethylphosphonate) iron (III) [Fe(EEP)³]; and tris (isopropyl methylphosphonate) iron (III) [Fe(EEP)³]; have been obtained and studied previously by infrared spectroscopy and elemental analysis.¹ The infrared obsorption spectra of the iron phosphonate compounds exhibited bands which could be assigned to functional groups of the phosphonate ligand; however, the role played by the iron atom in the molecule was unknown. In the present article, the results of Mössbauereffect spectroscopy are used to provide evidence for the interaction of the iron with the phosphonate esters.     

Diagnostics of High-Temperature,High-Density Plasma by Radiation Analysis

This article will be restricted to the diagnostics of laboratory plasmas having an average particle energy of higher than 30 eV per particle and a density of greater than 10¹⁹ particles per cm³. Common features of such plasmas related to applied spectroscopy are their complete ionization, the high excitation and ionization levels the particles, the large emission coefficients for continuum radiation over a wide spectral range from the X-ray region up to the infrared, their small size, high temperature and density gradients to the environment, and their transient nature.     

Laser spectroscopy with a pulsed, narrowband infrared optical parametric oscillator system: a practical, modular approach

-1 in a single scan. The potential of the OPO system for linear and nonlinear-optical spectroscopy is demonstrated by recording high-resolution photoacoustic absorption and coherent anti-Stokes Raman spectra of methane, as a gas and in a pulsed supersonic free jet. This narrowband tunable infrared source is shown to scan reliably with an optical bandwidth as small as 0.007 cm^-1 (210 MHz) full width half maximum (fwhm), close to the fourier-transform limit. Received: 5 February 1998/Revised version: 6 March 1998     

液氢平面低温冷冻靶的红外吸收谱

利用自主研制的平面低温冷冻靶系统和低温红外光谱测量系统,测量低温条件下液态氢的红外吸收谱,得出基频Q1(0)吸收峰位在4237.3cm-1处,随着温度从19.75K降到16.75K,吸收峰位几乎没有发生移动,而吸收增强.基于量子力学的非简谐近似,研究了氢分子的振动频率,得出H2的红外吸收频率与实验结果值一致.     

Chitosan loaded with silver nanoparticles,CS‐AgNPs,using thymus syriacus,wild mint,and rosemary essential oil extracts as reducing and capping agents

The present study describes the green method for the preparation of chitosan loaded with silver nanoparticles (CS‐AgNPs) in the presence of 3 different extracted essential oils. The essential oils play dual roles as reductant and capping agents. The reducing power and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) assay for the 3 essential oils—Thymus syriacus (T), wild mint (M), and rosemary (R)—have been reported. The preparation of CS‐AgNPs was performed by 2 steps. The 3 previously extracted essential oils have been used as reducing and capping agent in the first step, while in the second step, silver nanoparticles were integrated in chitosan. The integration of AgNPs in the structure of chitosan was confirmed by ultraviolet‐visible, Fourier transform infrared spectroscopy, scanning electron microscopy techniques, and energy dispersive X‐ray. Surface plasmon resonance confirmed the formation of CS‐AgNPs with maximum absorbance at λ_max between 405 ‐ 410 and 410 ‐ 430 nm for colloidal and films of CS‐AgNPs, respectively. The intensity of bands at 3408 cm^?1 in the fourier transform infrared spectroscopy measurements was decreased substantially and shifted slightly to lower frequency (?υ = 43 cm^?1). Scanning electron microscopy shows a spherical morphology of AgNPs with size of 62 nm for both colloidal and film samples, and energy dispersive X‐ray analysis shows peaks confirming AgNPs formation.     

Near Infrared Spectroscopy of Benzoic Acid Adsorbed on Montmorillonite

ABSTRACT

The adsorption of benzoic acid on both sodium and calcium montmorillonites has been studied by near infrared spectroscopy complimented with infrared spectroscopy. Upon adsorption of benzoic acid, additional near-infrared bands are observed at 8665 cm^?1 and assigned to an interaction of benzoic acid with the water of hydration. Upon adsorption of the benzoic acid on Na-Mt, the NIR bands are now observed at 5877, 5951, 6028, and 6128 cm^?1 and are assigned to the overtone and combination bands of the CH fundamentals. Additional bands at 4074, 4205, 4654, and 4678 cm^?1 are attributed to CH combination bands resulting from the adsorption of the benzoic acid. Benzoic acid is used as a model molecule for adsorption studies. The application of near-infrared spectroscopy to the study of adsorption has the potential for the removal of acids from polluted aqueous systems.     

A study on the influence of dysprosium cation substitution on the structural, morphological, and electrochemical properties of lithium manganese oxide

The synthesis of series of dysprosium-doped lithium manganese oxide in the general formula LiDy _x Mn_2?x O4 (x?=?0.0, 0.05, 0.1, 0.15, and 0.2) using double stage coprecipitation method followed by microwave heat treatment is reported. The characterization results of X-ray diffraction and infrared spectroscopy have illustrated the cubic structure for all the compounds. The lattice parameter has been observed to decrease with dysprosium doping. The influence of doping in elastic property of the samples has been studied with infrared spectroscopy. The grain size of the LiDy_0.05Mn_1.95O₄ has been observed to be less than 1???m. The Image J software has been used to further analyze the micrographs. The initial capacity of the samples are observed to decrease with Dy³⁺ doping, but the capacity retention after 50 cycles for Dy 0.05, 0.1, 0.15, and 0.2 samples are reported as 95.4%, 93.2%, 91.3%, and 87.7%, respectively. The electrochemical impedance spectra has been performed to analyze the effectiveness of Dy³⁺ ion doping and the act of Dy doping has been observed to reduce the charge transfer resistance and increase the Li ion diffusion coefficient.