Infrared Transmission Spectroscopy Research Articles

Synthesis and Properties of SrBi2Ta2O9-Based Glass-Ceramics Modified with Eu3+

The Eu3+-doped novel precursor glass in the K2O–SiO2–SrO–Bi2O3–Ta2O5 system was prepared using the melt-quench technique. The transparent SrBi2Ta2O9 (SBT) glass-ceramic nanocomposites were derived from this glass using a controlled crystallization process. The formation of SBT crystal phase, size, and morphology with increase in heat-treatment time was examined using X-ray diffraction, field emission scanning electron microscopy, and fourier transform infrared transmission spectroscopy. Vicker's hardness study indicates marked improvement of hardness in the glass-ceramics compared to precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 467 nm. These spectra reveal that the Eu3+ ions are gradually entering into the SBT nanocrystals present in the glass-ceramics. This study indicates that the incorporation of Eu3+ ions into SBT crystal lattice enhances the photoluminescence performance of the glass-ceramics by two-fold. It is believed that this work would generate significant impact in the exploration of SBT glass-ceramic nanocomposites.

Ultra-high vacuum deposition and characterization of silicon nitride thin films

Silicon nitride thin films were deposited on (100) Si wafers in an ultra-high vacuum system using a Si effusion cell and reactive nitrogen from a radio-frequency plasma source. The films were characterized using infrared transmission spectroscopy, infrared reflectance, Rutherford backscattering spectrometry, spectroscopic ellipsometry, specular x-ray reflectivity, wet etching in a buffered-oxide etch solution, and the electrical characterization of metal-insulator-semiconductor capacitors. High-quality, stoichiometric silicon nitride films with a refractive index of 2.05 at 632.8 nm are produced when the deposition temperature is 750 °C. Lower deposition temperatures produce nitrogen-rich silicon nitride films with lower refractive index, lower density, greater tendency toward oxidation in ambient air, faster etching in a buffered oxide etch solution, and greater electrical leakage. A deposition model involving thermal evolution of weakly-bonded excess N is proposed to explain our observations.

Electronic excitation induced controlled modifications of semiconductor-to-metal transition in epitaxial VO2 thin films

Abstract

Fast Analysis of Entire Sunflower Seeds with Shell by near Infrared Transmission Spectrometry to Determine Fat

Fast Analysis of Entire Sunflower Seeds with Shell by near Infrared Transmission Spectrometry to Determine Fat

Application of the Temkin Model to the Adsorption of CO on Gold

A treatment of the Temkin model was developed for describing the adsorption of CO on gold. In this presentation, it is made clear that the Temkin thermodynamic model is an extension of the Langmuir model that incorporates a linear variation of the adsorption enthalpy. It is also stressed that the Temkin model can be interpreted in terms of two distinct physical situations: the first assumes equivalent binding sites and an adsorption enthalpy that varies with coverage due adsorbate interactions, while the second assumes a uniform distribution of heterogeneous binding sites and an adsorption enthalpy that varies due to the heterogeneity of sites. In addition, a midrange approximation, where the surface is roughly half covered with adsorbates, is commonly employed. While each of these situations is similar, they are not equivalent and yield slightly different analytical expressions that describe the adsorption coverage as a function of pressure and temperature. Fitting data with the different analytical expressions therefore produces slightly different thermodynamic values for the adsorption enthalpy and entropy. These different cases are explicitly defined and developed. For the adsorption of CO on gold, the adsorbate interaction case is shown to be most consistent with the current body of experimental and theoretical evidence. The various analytical expressions are used to apply the Temkin model to data for CO adsorption on 1% Au/TiO2 real-world catalysts (from the World Gold Council) studied under catalytically relevant isothermal (T = 275–325 K) and isobaric (PCO = 0–10 Torr) experimental conditions. Infrared transmission spectroscopy was the analytical technique used for quantitatively measuring the adsorption coverage. The coverage as a function of pressure (θ,P) and as a function of temperature (θ,T) was fit with the Temkin adsorption models. The models yield the thermodynamic adsorption enthalpy at zero and full coverage as well as the adsorption entropy. The values of these thermodynamic parameters differ slightly depending upon the particular Temkin situation considered (cf. adsorbate interaction, heterogeneous surface, and midrange approximation cases). While all three Temkin cases produced excellent fits to both the isothermal and isobaric data sets, the adsorbate interaction case is most consistent with experimental and theoretical evidence describing the adsorption of CO on gold. The average enthalpy values from fitting the isothermal and isobaric data sets using the adsorbate interaction model are −ΔH0 = 59.2 kJ/mol and −ΔH1 = 54.6 kJ/mol for zero and full coverage, respectively. The adsorption entropy, −ΔS = 142 J/(K mol), was determined by fitting the data sets from multiple isothermal experiments with the adsorbate interaction case. These thermodynamic adsorption values are in excellent agreement with previously reported values. The validity of the Temkin adsorbate interaction model was further supported by fitting isothermal and isobaric data for the adsorption of CO on a well-defined gold surface, as reported previously by Gottfried et al. This new treatment of the Temkin adsorption model is theoretically and experimentally straightforward and applicable to both isothermal and isobaric data sets. It provides meaningful thermodynamic values of adsorption enthalpy and entropy, which can be used to characterize and explain differences between various catalysts. The model should also be applicable to the adsorption of other small molecules on metal surfaces and particles that show coverage-dependent adsorption properties.

O] [H] functionalization on carbon nanotube using (O2–H2) gas mixture DC glow discharge

The (O) (H) functionalization of carbon nano- tube (CNT) was studied using oxygen-hydrogen (O2-H2) gas mixture direct current (DC) glow discharge plasma technique for cathode/CNT-anode separation of 0.10 ± 0.01 cm. O2 and H2 were fixed at flowrate of 10.0 ml/min in order to obtain gas mixture ratio of 1:1. During the (O2-H2) gas mixture DC glow discharge, current-voltage (I-V) characteristic of gaseous species studied for various settings of gas pressures 1, 2, 3 and 4 mbar. The voltage at gap between cathode/CNT and anode, a breakdown voltage, was identified as ''functionalization voltage'' (Vfunc). Vfunc was noticed responsible for functionalization of functional groups on sidewall of CNT. The Vfunc were recorded as 796, 707, 594, and 663 V for gas pressures of 1, 2, 3 and 4 mbar, respectively. The co-relation between Vfunc and gas pressure was identified as linear relationship. But a voltage obtained due to the CNT/Cathode fall shows exponential relationship with the gas pressures. The possibility of (O) (H) functional- ization was proved using Fourier transmission infra-red (FTIR) spectroscopy. Hydroxyl (-OH), carboxyl (-COOH), and carbonyl (-C=O) functional groups were identical as identified in the FTIR spectra. The field emission scanning electron microscope images show significant changes in the morphology of CNT which proves that the DC gas discharge plasma is a possible technique for (O) (H) functionalization on the sidewall of CNT.

Nanostructured VOx/VO(PO4)n Using Solid-State Vanadium Containing Phosphazene Precursors: A Useful Potential Bi-Catalyst System

Pyrolysis of molecular precursors containing vanadium organometallic and cyclic phosphazene affords mixtures of nanostructured vanadium oxides and pyrophosphates. The products from the molecular precursor [N3P3(OC6H5)5OC5H4N·Cp2VCl][PF6], and of the mixtures Cp2VCl2/N3P3(OC6H4CHO)6 and Cp2VCl2/[NP(O2C12H8)]3 in several relationships 1:1, 1:3, 1:5 and 1:10, pyrolyzed under air and at 400 °C and 600 °C, give mixtures mainly V2O5 and VO(PO3)2. Varied morphologies depending on the molecular or mixture precursors and of the temperature used were observed. Nanowires with diameters of approximate 40 nm were observed for the 1:5 Cp2VCl2/[NP(O2C12H8)]3 mixture pyrolyzed at 400 °C, while the same mixture pyrolyzed at 600 °C, affords xerogels of V2O5. The products were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), infra-red (IR) spectroscopy and X-ray diffraction (XRD). The preparation method constitutes a novel one-pot solid-state way to nanostructured materials with potential applications both in oxidative dehydrogenation of light hydrocarbons with V2O5, as well as alkenes oxidations with VO(PO3)2.

Research of the Detection of Apple Sugar Conten Based on Machine Vision and near Infrared Spectroscopy

In this paper, use the basic principles of near infrared to detect the spectral characteristics of apple, as the research object of Fuji apple, and then establish the model of near infrared technology forecasting apple sugar content, to discover the sugar content in apple. The results show that near infrared transmission spectroscopy can be used as an accurate, reliable, nondestructive testing method, the test has obvious advantages for detecting indicators of Fuji apple sugar.

A study of Sn addition on bonding arrangement of Se-Te alloys using far infrared transmission spectroscopy

Far infrared transmission spectra of Se92Te8−xSnx (x = 0, 1, 2, 3, 4, 5) glassy alloys are obtained in the spectral range 50–600 cm−1 at room temperature. The results are interpreted in terms of the vibrations of the isolated molecular units in such a way so as to preserve fourfold and twofold coordination for Sn and chalcogen atoms (Se,Te), respectively. With the addition of Sn, Far-IR spectra shift toward high frequency side and some new bands start appearing. Sn atoms appear to substitute for the selenium atoms in the outrigger sites due to large bond formation probability. Theoretical calculations of bond energy, relative probability of bond formation, force constant, and wave number were also made to justify the result.

Preparation and optical properties of silica gels doped with a new Eu(III) complex

The preparation and incorporation in silica gels of a novel europium complex, [Eu(ntac) 3][pphendcn] containing 4,4,4-trifluoro-1-(naphthalene-2-yl) butan-1,3-dione (Hntac) and pyrazino[2,3-f][1,10-phenathroline-2,3-dicarbonitrile (pphendcn) is demonstrated. An effective energy transfer from the organic ligands to the Eu(III) ions leads to a strong f–f luminescence even at low activator concentrations, n Eu/ n Si ≈ 1 × 10 −5. The new amorphous materials are characterized by UV/Vis reflectance and transmission spectroscopy, luminescence/excitation spectroscopy, X-ray diffraction, elemental analysis, IR spectroscopy, DTA/TG and NMR. The optical properties of gels with a different Eu(III) doping are discussed. The stability of the europium complex in the silica matrix during time (up to 4 months) and after heating is discussed. The Eu(III) spectra–structure correlation is used to characterize the site symmetry of the activator.

COMPARATIVE STUDY OF LA0.7CA0.3MN0.95FE0.05O3 PEROVSKITES PREPARED BY DIFFERENT METHODS AND EFFECT OF PREPARATION ON CATALYTIC ACTIVITY FOR HYDROXYLATION OF BENZENE

Magnetic nanoparticles of La0.7Ca0.3Mn0.95Fe0.05O3 perovskites were synthesized by various wet chemical routes, namely co-precipitation, oxalate-gel and citrate-gel methods. Phase formation and crystal structure of the synthesized powders were examined by the X-ray diffraction (XRD) using the Rietveld analysis. The micro- structure was determined by means of scanning electron microscopy (SEM). Infrared transmission spectroscopy revealed that stretching and bending modes are influenced by preparation methods. Synthesis using the oxalate-gel method yielded incomplete reaction irrespective of the calcination temperature adopted. The citrate-gel method yielded better powder properties in terms of particle size and morphology as compared to co-precipitation synthesis. The highest activity for the catalytic oxidation of benzene to phenol in presence of H2O2 was obtained with the sample prepared by the citrate–gel method.

Comparison of the optical, thermal and structural properties of Ge–Sb–S thin films deposited using thermal evaporation and pulsed laser deposition techniques

Thin films of Ge 23Sb 7S 70 glass were prepared by thermal evaporation (TE) and pulsed laser deposition (PLD) techniques. We measured their thermal, optical and structural properties and compared with those of the parent bulk. The probe penetration temperature ( T p) of the bulk glass, measured using a micro-thermal analyzer, was found to be 412 ± 10 °C, while those of the TE and PLD films were 468 and 470 ± 10 °C, respectively. The refractive index of the bulk and thin films was measured by ellipsometry and ultraviolet–visible–near infrared transmission spectroscopy, and we show that the films have similar refractive indices, which are lower than those of the parent bulk glass. Using micro-Raman spectroscopy, the structure of the film was investigated. The films contain homopolar Ge–Ge bonds and a lower number of homopolar S–S bonds compared to bulk material, which leads to an increase in the proportion of corner shared GeS 4/2 units in the films as compared to the bulk glass. Comparison of structural entities associated with each deposition process showed that the TE film possesses a lower number of S–S bonds and a slightly higher number of SbS 3/2 units compared to the PLD film. These structural changes lead to a more interconnected glass network, and therefore to a higher viscosity at elevated temperatures, as well as a higher refractive index, presumably through increased density. Post-deposition of annealing of these films causes their thermal and optical properties to revert to a more bulk-like state, suggesting that these property differences are due to a difference in the thermal histories of the bulk and film glass networks. For the first time to our knowledge, the refractive index of the bulk glass in the 0.6–10.6 μm range, measured using the prism coupling technique, is also presented.

Non-destructive prediction of hardening pericarp disorder in intact mangosteen by near infrared transmittance spectroscopy

A non-destructive technique to predict a hardening pericarp disorder in intact mangosteen is proposed by using near infrared (NIR) transmittance spectroscopy in the wavelength range of 660–960 nm. The study found that the spectral features of normal pericarp mangosteen and hardening pericarp mangosteen were different. The averaged spectra and individual spectra of hardening pericarp mangosteen from a calibration set ( N = 560) were used to develop classification models, using partial least squares discriminant analysis (PLS-DA). A model based on individual spectra obtained better classification. The overall accuracy of classification for a prediction set ( N = 358) was 91%. Out of 179 samples of normal pericarp fruits, 167 were identified correctly, while 159 samples out of 179 samples with hard pericarp were predicted correctly. The results showed that NIR transmittance spectroscopy can be used to predict hard pericarp disorder in intact mangosteen fruit accurately.

Obsidian hydration dating by infrared spectroscopy: method and calibration

Low temperature (90–190 °C) hydrothermal experiments have been conducted on seven obsidians where composition of the glass varies significantly in the concentration of structural water within the unhydrated bulk material. Infrared transmission spectroscopy was used to track the diffusion of molecular water into the glass surface as a function of time and temperature. Long-term (60–360 days) hydration sequences at 90 °C show a t 0.6 time dependence for the mass uptake of molecular water that forms the hydration layer. The structural water concentration of the unhydrated bulk obsidian is highly correlated with the pre-exponential and activation energy and may be used to estimate the Arrhenius constants. In addition, secondary ion mass spectrometry (SIMS) hydrogen profiling of Napa Glass Mountain obsidian hydrated at 90 °C reveals that the early stages of diffusion exhibit a dynamic behavior that includes a fluctuating hydrogen concentration and a changing diffusion coefficient that slows with time.

Lyman-α driven molecule formation on SiO2 surfaces—connection to astrochemistry on dust grains in the interstellar medium

As a model for silicate dust grains in the interstellar medium, we have used high area amorphous SiO(2) as a surface on which to carry out Lyman-α (10.2 eV) photodecomposition of adsorbed N(2)O at 71 K and at a coverage of ∼0.3 monolayer. The N(2)O molecules are adsorbed by hydrogen bonding to surface Si-OH groups. Transmission IR spectroscopy measurements permit the observation of the consumption of adsorbed N(2)O and the production of various photoproducts. It is observed that in comparison to N(2)O consumption, the relative rate of formation of the products NO(2) and N(2)O(4) made by combination reactions is enhanced significantly on the SiO(2) surface. Reactions between photogenerated radicals themselves or between radicals and parent N(2)O on the SiO(2) surface exceed the relative rates observed in the gas phase by factors of up to ∼20. As the complexity of the combination product increases, its relative production rate, compared to the gas phase, increases due to the involvement of multiple surface-combination elementary steps. It is proposed that the enhancement of combination reactions on the SiO(2) surface is due to the surface's ability to absorb excess energy evolved during the chemical-bond-forming events on the surface. This principle is probably significant on grain surfaces supporting photochemical processes of astrochemical interest, and indeed is expected. The cross section for adsorbed N(2)O photodecomposition on the porous SiO(2) surface is about 7 × 10(-20) cm(2) and the quantum yield for the adsorbed molecule decomposition is about 0.006, compared to a quantum yield of 1.46 in the gas phase. This decrease in photon efficiency is attributed to absorption and scattering of Lyman-α radiation by the SiO(2) particles.

Macrocyclic Core Phosphorus Dendrimers Covered on the Surface by N,P Ligands

AbstractA new family of dendrimers up to the third generation is synthesized starting from a 15‐membered triolefinic azamacrocycle. γ‐Iminophosphane groups are anchored on the surface of the second and third generations, and their corresponding PdII complexes are prepared. To investigate the effect of shielding upon the coordinating ability of the macrocyclic core, the coordination with Pd0 and Pt0 atoms is studied. During this process, two new materials containing Pd0 or Pt0 nanoparticles stabilized by these dendrimers are characterized by high‐resolution transmission electron microscopy, IR spectroscopy, and elemental analysis.

Plasma-Assisted Deposition of Au/SiO2 Multi-layers as Surface Plasmon Resonance-Based Red-Colored Coatings

In this work, the expanding thermal plasma chemical vapor deposition in combination with radio frequency magnetron sputtering is used to deposit dielectric/metal multi-layers with controlled size and density of nanoparticles. The multi-layer structure serves the purpose of increasing the nanoparticle number density, without changing the metal particle size, shape and the interparticle distance. The possibility of independently tuning and, therefore, controlling the nanoparticle size and number density allows developing surface plasmon resonance-based deep-colored coatings. The influence of the number of layers, metal surface area coverage, and thickness of the dielectric layer on the multi-layer nanostructure and on the developed color is presented here in detail. The nanoparticle size and distribution have been measured by transmission electron microscopy. Rutherford back-scattering and infra-red transmission spectroscopy have been used to determine the metal surface coverage and the film chemistry, respectively. Optical properties of the nano-composite layers have been investigated by UV-VIS spectroscopy and exhibit an increase in amplitude of the plasmon absorption spectra at a fixed plasmon resonance frequency with an increase in the number of layers.

Solvothermal synthesis and electrochemical properties of 3D flower-like iron phthalocyanine hierarchical nanostructure

In the present work, a highly uniform three-dimensional flower-like 2,9,16,23-tetra-nitrophthalocyanine iron (TNFePc) hierarchical nanostructure has been successfully obtained by a facile ethylene glycol solvothermal synthetic route. The as-obtained product was characterized by mass spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), IR spectroscopy, UV-vis spectroscopy, and Brunauer–Emmett–Teller analysis. The results showed that the flower-like hierarchical nanostructure was made up of numerous two-dimensional nanoplates with a thickness of about 50 nm. Electrochemical measurements revealed that the TNFePc hierarchical nanostructure exhibited excellent capacitance behavior, which could be ascribed to the ultrahigh surface area and large pore volume. Finally, a possible mechanism for the formation of three-dimensional flower-like TNFePc was suggested.

A study of stabilization of P3HT/PCBM organic solar cells by photochemical active TiO x layer

We describe a study of the stabilization behavior of P3HT/PCBM organic solar cells under air and UV irradiation using a 20 nm thin TiO x protection layer made by partial hydrolysis of a Ti-alkoxide and spin coating in air. Data on the degradation of solar cell performance under air and under UV exposure are presented indicating that significant improvements are observed with TiO x layer protection. The protection mechanism has been investigated by transmission IR and UV spectroscopy and by ESR spectroscopy. The results of this study suggest how sol–gel derived TiO x films containing organic functionalities serve as effective passivation films for protection from oxygen when excited by photons, where the photooxidation of the bound organic moieties causes oxygen gas scavenging.

CdSe/Zns-QD Incorporated Microbeads for Ultra-sensitive Chemo-sensor Applications

CdSe/ZnS QD microbeads for detecting toxic and bio-materials with high sensitivity were prepared by the incorporation of CdSe/ZnS QDs into mesoporous silica. CdSe/ZnS core/shell QDs were synthesized from precursors such as CdO and zinc stearate with lower toxicity than pyrophoric precursors. In order to enhance the number of QDs encoded into the silica beads, the spherical mesoporous silica with the pore size of 20 - 30 nm is surface-modified by octadecyl silane. The QDs and QD microbeads were characterized by using transmission electron microscopy, IR spectroscopy and fluorescence microscopy. Based on the surface derivative reaction of the alkyl chains on the microbeads, the compatibility between the surface wetting properties of the QDs and the mesoporous silica is noted to play a key role in enhancing the diusion of QDs into mesoporous silica.