IR Transmission Spectra Research Articles

INFLUENCE OF B2O3 ON THE INTERACTION IN THE SiO–GeO2 SYSTEM

The influence of the B2O3 additive on the nature of the interaction in the SiO–GeO2 system was investigated by X-ray diffraction and IR transmission spectroscopy. The nature of the diffractograms of the SiO–GeO2–B2O3 system with a composition of 1:1:0.5 and 1:1:1 corresponds to the presence of SiO2 phases of hexagonal modification (quartz) and GeO2 of various modifications, as well as, possibly, a crystalline B2O3 phase. The exact value of the content of the reaction products and initial components could not be determined due to the significant content of the X-ray amorphous component of unknown composition. The broadening of the diffraction peaks and the presence of a distinct halo testify to the benefit of the processes of nanostructuring and glass formation. However, the absence of elemental germanium in the SiO–GeO2–B2O3 system, in contrast to the SiO–GeO2 system, was clearly established. The nature of the IR transmission spectra of samples with different content of B2O3 additive differ significantly from each other. Thus, the IR transmission spectra of the sample with a composition of 1:1:0.5 contain weak absorption bands due to the oscillations of the B–O bonds; instead, they reveal periodic oscillations characteristic of nanostructured systems. In the spectra of the sample with a composition of 1:1:1, the absorption bands due to the oscillations of the B–O bonds are very distinct, but there are no oscillations. Therefore, the addition of B2O3 probably accelerates the formation of Germanium monoxide, which in turn reacts with the B2O3 additive and possibly with SiO2 as one of the reaction products. Testing of samples of the SiO–GeO2–B2O3 system by the method of thermal evaporation in a vacuum revealed the advantages of the sample with a composition of 1:1:1 in the ability to form a strong and durable coating. It was possible to determine the refractive index for it, which is 1.93 at a wavelength of 1000 nm. Instead, the coating obtained from the 1:1:0.5 composition sample turned out to be unstable. A conclusion was made about the need for further optimization of the composition and synthesis conditions to obtain materials with the required parameters.

Effect of B2O3 addition on optical properties of Zirconium and Hafnium tetrafluorides in polycrystalline and thin film states

For the first time, the effect of B2O3 additive on the IR transmission spectra of ZrF4 and HfF4 samples and the optical properties of the coatings obtained from them was investigated. A significant difference in the shape of the absorption bands and the position of the vibration peaks of the Zirconium tetrafluoride and Hafnium tetrafluoride bonds was revealed. An assumption is made about the influence of ZrF4 polymorphism on the ratio of the vapor pressures of the specified compounds in the region of the conditional temperature of evaporation in a deep vacuum. The positive effect of the B2O3 additive on the rate of evaporation of system samples and condensation on substrates is shown. The values of the refractive indices of the coatings are about 1.53. An exception is the refractive index of the HfF4 coating (1.57), which can be attributed to the alternative (monoclinic) syngony of its crystal structure.

The parent bodies of CR chondrites and their secondary history

AbstractRenazzo‐type (CR) chondrites are a relatively rare group of carbonaceous chondrites with the vast majority having escaped thermal alteration. This means that CRs are composed of relatively unprocessed material, depending on the extent of aqueous alteration they have experienced. Hydration in CRs ranges from incipient alteration of matrix glass, up to nearly complete replacement of the rock by hydration products. The extent of secondary processes is often difficult to assess in these meteorites, due to their heterogeneity and diversity of alteration products. Yet, this is crucial in order to understand the extent of geological processing that occurred on the primary parent body. Additionally, the parent asteroids of CRs remain a mystery, mainly because terrestrial oxyhydroxide signatures dominate the reflectance spectra of CRs. In this work, we have conducted optical and IR reflectance and transmission spectra of 25 CR chondrites in order to (i) better evaluate the extent of aqueous alteration that occurred on the CR parent body, and (ii) find possible parent body candidates. Terrestrial oxyhydroxides were removed from 12 samples, as these tend to interfere with the optical‐IR spectra of CRs. Our results suggest, among other, that (i) aqueous alteration in most of our CRs was limited to the matrix and (ii) most CRs may stem from a continuum of X‐to‐C complex asteroids, depending on their extent of aqueous alteration. More specifically, the endmembers being Xk/Xn types and Cgh/Ch types. This has strong implication in regard to what we can expect from the Psyche mission.

Up-conversion luminescence and defect structures in Sc: Dy: LiNbO3 crystals affected by Sc3+ concentration

Up-conversion luminescent material LiNbO3 crystal has been studied intensively due to its applications in solar cells, medical applications, color displays and so on. LiNbO3 crystal with poor ability of photodamage resistance limits its application in practice. Up-conversion luminescence properties of Dy: LiNbO3 crystals doped with anti-optical damage dopants have a promising future. Four Sc: Dy: LiNbO3 crystal samples were prepared by the Czochralski technique with Sc3+ concentrations of 0, 1, 2, and 3 mol%. Effective concentrations of Sc3+ and Dy3+ in the crystals were measured by ICP-AES. The occupancy rate of the dopant and crystal structure were investigated by XRD and IR transmission spectra. The properties of up-conversion emission were studied in view of up-conversion emission intensity and fluorescence lifetime. Blue (474 nm), yellow (583 nm), and red (655 nm) up-conversion luminescence were achieved under 800 nm excitation. Remarkably, the luminescence intensity increases significantly by several times when the Sc3+ doping concentration was 3 mol%. This indicates that Sc: Dy: LiNbO3 crystals have potential as optical devices.

Growth of TiO2–CdO coated films: A brief study for optoelectronic applications

Current work reports the deposition of pure and TiO2 doped CdO printed films on glass substrate via cost-effective screen-printing method and then sintered at 550 °C for 10 min. The pure TiO2, CdO and TiO2–CdO coated films were used to investigate the structural, morphological and opto-electrical properties by different analytical techniques. X-ray diffraction pattern of polycrystalline doped analogue confirms the existence of TiO2 anatase phase and cubic phase of CdO with a maximum diffraction of (101) plane. Surface morphology is derived from scanning electron microscopy finding out porous images along with EDS results to confirm the desired composition. The spectra of UV–Vis diffused reflectance spectroscopy and photoluminescence absorbance peaks show a red shift due to change in reflectance. IR transmittance spectra recorded in 4000-400 cm−1 region exhibits the stretching modes of O–Ti–O and Cd–O groups present in these samples. The current vs. voltage (IV) characteristics and direct current conductivity measurement shows p-n junction diode behaviour. All the parameters were calculated and described in-depth, including structural, optical and electrical properties. The obtained results suggest that TiO2–CdO thick film could be used in optoelectronic applications due to the shift in optical radiation absorption to visible region, reduction in recombination rate of charge carriers and increase in electrical conductivity.

Green chemistry based benign approach for the synthesis of titanium oxide nanoparticles using extracts of AzadirachtaIndica

The colossal significance of nanostructured materials and their implications is a coherent incentive for the exploration of novel conventional techniques. This brings attention to the major problem in developing nanomaterials i.e. the hazardous nature of reactants used. The hazardous reactants are harmful to the environment. So here, biogenic synthesis of nanostructured materials utilizing natural herb extracts has enthralled prodigious implications owing to its rapid, clean, eco-friendly, non-toxic, cost-effective, and as a flipside pathway to several chemical and physiochemical approaches. Titanium oxide materials have been the cynosure for several propitious implications due to their low cost, availability, chemical stability, and biocompatibility. Herein, we developed an efficient green chemistry method for the synthesis of titanium oxide nanoparticles utilizing neem (Azadirachta Indica) extracts. The X-ray diffraction studies revealed the polycrystalline titanium oxide (rutile) structure. The spherical shape of the nanoparticles was observed in TEM and SEM images and their size ranged from 10 to 20 nm. UV–vis studies showed an exciton emission peak at about 380 nm while the IR transmission spectrum revealed the characteristic stretching modes of TiO2. It is envisioned that this novel route for the synthesis of TiO2 nanoparticles could be more beneficial in comparison to other conventional approaches. As the greener approach is being carried out in this paper, therefore, the toxic byproduct is not being released.

Phonon assisted charge transfer in complexes of Zn(II) and Cd(II) with 2-acetylpyridine-aminoguanidine

Metal complexes with some Schiff bases, as one of the most widely used groups of ligands, have a wide field of application. In order to find a material with the required optical properties, it is very important to examine the material characteristics as a function of the type of chelating ligand, metal, and the ions present as coligands. In this paper, the synthesis of two new complexes of 2-acetylpyridine-aminoguanidine (L) with zinc(II) and cadmium(II), viz. [Zn(L)(NCO)2] and [{Cd(L)Cl(μ-NCO)}2] is described. Their structural characterization was provided by using SC-XRD. Spectroscopic characterization of these two new complexes and two previously synthesized complexes - [Zn(L)(NSC)2] and [Cd(L)Cl2] are performed. Their phonon structure was determined based on the IR transmission and Raman spectra. The range of Raman modes with significantly increased intensities was registered (1000-1700 cm−1), the same range for all four samples. Also, the registered photoluminescence and energy transfers were analyzed and three photoluminescence peaks (E1, E2, E3) were determined. It was concluded that phonons with significantly increased intensities participate in transitions from the E1 state to the energy levels in the range from E2 to E3. The strength of the peaks was significantly affected by replacing one [Cl]- with the [NCO]- ligand. The addition of the second [NCO]- ligand increases the photoluminescence over the entire measured range. The analysis performed helps to understand the issues related to the electron-phonon interaction. Also, the perspectives for the application of metal complexes with various ligands are expanding.

First La2O2S infrared transparent ceramics

Lanthanum oxysulfide (La2O2S) was investigated as infrared transparent ceramic to benefit from stronger chemical bonds and superior mechanical performances to that of non-oxide benchmark infrared materials. La2O2S ceramics were processed by hot-pressing powders prepared by combustion synthesis followed by a sulfurization treatment. Powders and ceramics were characterised through various techniques (XRD, UV-Vis-IR spectroscopy, particle size analysis, SEM, Impulse Excitation Technique, microhardness and fracture toughness tests) to assess their purity, study their microstructure and determine their optical and mechanical properties. The study reports the first IR transmission spectra, Poisson’s ratio, Young’s and shear moduli and fracture toughness values of La2O2S polycrystalline ceramics. The ceramics showed transparency in the 2–11 µm range and their mechanical performances were all superior to that of commercial infrared ceramics. The best transmission (89% of the theoretical transmission) was measured at 7.3 µm for 1 mm-thick ceramics hot-pressed at 1200–1250 °C.

Mid‐ to Far‐Infrared Anisotropic Dielectric Function of HfS2 and HfSe2

AbstractThe far‐infrared (far‐IR) remains a relatively underexplored region of the electromagnetic spectrum extending roughly from 20 to 100 µm in free‐space wavelength. Research within this range has been restricted due to a lack of optical materials that can be optimized to reduce losses and increase sensitivity, as well as by the long free‐space wavelengths associated with this spectral region. Here the exceptionally broad Reststrahlen bands of two Hf‐based transition metal dichalcogenides (TMDs) that can support surface phonon polaritons (SPhPs) within the mid‐infrared (mid‐IR) into the terahertz (THz) are reported. In this vein, the IR transmission and reflectance spectra of hafnium disulfide (HfS2) and hafnium diselenide (HfSe2) flakes are measured and their corresponding dielectric functions are extracted. These exceptionally broad Reststrahlen bands (HfS2: 165 cm−1; HfSe2: 95 cm−1) dramatically exceed that of the more commonly explored molybdenum‐ (Mo) and tungsten‐ (W) based TMDs (≈5–10 cm−1), which results from the over sevenfold increase in the Born effective charge of the Hf‐containing compounds. This work therefore identifies a class of materials for nanophotonic and sensing applications in the mid‐ to far‐IR, such as deeply sub‐diffractional hyperbolic and polaritonic optical antennas, as is predicted via electromagnetic simulations using the extracted dielectric function.

Influence of Calcium Substitution on Structural, Vibrational and Paramagnetic properties of Magnesium Ferrite

The environment friendly calcium substituted magnesium ferrite with composition MgCaxFe2-xO4 (x = 0.00, 0.01, 0.03, 0.05, 0.07) synthesized by the conventional solid – state reaction powdered samples are studied for structural, vibrational and spin characteristics for chemical sensor application. XRD patterns with Rietveld refinement reveal partial inverse spinel structure of the prepared samples with tentative cation occupancy. The rietveld refinement is performed to know the cation occupancy in the prepared samples which could be further helpful to exploit these ferrite materials for different technological applications. The intensity of  Fe3+-O stretching vibrational peaks arising from tetrahedral (1) and octahedral(2) sites in IR transmittance spectra are composition and cation distribution sensitive. The presence of Ca2+/Mg2+/Fe2+ ionsis evidenced by the splitting of bands and shoulder peaks in IR transmittance spectra. The strong dipolar-dipolar interactionsencourage broad asymmetric EPR derivative signal of Fe3+ ions. The substitution of diamagnetic Ca2+ dopant ions in latticestrengthens dipolar-dipolar interactions, broadens the resonance signal and higher g-values due to spin disorder (spinfrustration).

Chasing Vibro-Polariton Fingerprints in Infrared and Raman Spectra Using Surface Lattice Resonances on Extended Metasurfaces.

We present an experimental investigation of vibrational strong coupling of C=O bonds in poly(methyl methacrylate) to surface lattice resonances (SLRs) on arrays of gold particles in infrared and Raman spectra. SLRs are generated from the enhanced radiative coupling of localized resonances in single particles by diffraction in the array. Compared to previous studies in Fabry–Perot cavities, particle arrays provide a fully open system that easily couples with external radiation while having large field confinement close to the array. We control the coupling by tuning the period of the array, as evidenced by the splitting of the C=O vibration resonance in the lower and upper vibro-polaritons of the IR extinction spectra. Despite clear evidence of vibrational strong coupling in IR transmission spectra, both Raman spectroscopy and micro-Raman mapping do not show any polariton signatures. Our results suggest that the search for vibrational strong coupling in Raman spectra may need alternative cavity designs or a different experimental approach.

STRUCTURAL AND OPTICAL PROPERTIES OF SiC/Si HETEROSTRUCTURES OBTAINED USING RAPID VACCUM-THERMAL CARBIDIZATION OF SILICON

TEM investigation revealed that the rapid vacuum-thermal carbidization of silicon at 1100C leads to the formation of cubic silicon carbide (SiC) layers. The band of the IR transmission spectrum at 798 cm–1 corresponding to the stretching vibration of Si-C and the maximum of Raman spectrum at 793 cm–1 relating to transverse optical phonon mode of SiC confirm the formation of a layer of the cubic SiC politype. The absorption
 band of Si-O-Si (1100 cm–1) was found using the IR-spectroscopy. The dependence of the transmission coefficient on the wavenumber was determined.

IR absorptance of thin carbon multi-walled nanotubes layers

The IR transmittance and reflectance spectra of thin films which consist of multi-walled carbon nanotubes (MWCNT) are measured in the range from 2 to 17 μm. The MWCNT films of various thicknesses not exceeding 1.2 μm were deposited on silicon substrates with Si3N4/Al2O3 dielectric layers. It is shown that the deposition of an Al2O3 layer with a thickness of 2 nm allows to significantly improve the homogeneity and continuity of the MWCNT films. A technique is proposed for measuring the average thickness of rough MWCNT films by means of atomic force microscopy after laser engraving. Suggested method of spectra processing allows to estimate the spectral dependence of the IR radiation absorptance in MWCNT films, which are diffusely scattering objects and have a large absorption coefficient.

Characterization of some optical and physical properties of As11.2S48.0Sb28.8Te12.0 and As20.8S48.0Sb19.2Te12.0 nanostructured polycrystalline semiconductors

This work presents the characterization of As-S-Sb-Te nanostructured polycrystalline semiconductors by X-ray fluorescence (XRF), X-ray diffraction (XRD), electron microscopy (SEM), optical as well as photoelectric methods. The XRD patterns have been shown the presence of amorphous and nanocrystalline phases with the main structural units As2S3, Sb2S3 and Sb2Те3. The IR transmission spectra show a high transparence just with a single weak absorption band about ν=2340 cm-1 caused of the presence of H2S impurity. It was also observed that for the alloys of As11.2S48.0Sb28.8Te12.0 and As20.8S48.0Sb19.2Te12.0, with an increase in the number of As atoms, the transmission in the IR region also increase. The maximum of steady-state photoconductivity for both materials, measured in the linear portion of I-V characteristics, is situated around =0.96 m.

Induced gyrotropy in thin PET films before and after swift heavy ion irradiation evidenced from analysis of optical interference fringes

We present here experimental studies of the UV/vis/near IR transmission spectra of polyethylene terephthalate (PET) films before and after irradiation with Kr+15 ions of energy 1.75 MeV/a.u. and fluence of 1.9 × 10 10 cm−2. Our data show small variations (∼0.5%) in transmission between individual pristine PET film samples in the IR region of the spectrum, as would be expected for films produced to certain manufacturing tolerances. Swift heavy ion (SHI) irradiation of a sample reduces transmission in this region, but by less than the observed variation in transmission between individual pristine samples, and does not affect local transmission variations in the spectrum, indicating that SHI irradiation has not destroyed the molecular structure of the PET film responsible for these variations. We use established methods to separate our experimental spectra into interference-free transmission spectra and isolated interference fringes and estimate the absorption coefficient and dispersion of the refractive index for pristine and irradiated PET films. We show that the observed amplitude modulation of the interference fringes is due to the optical activity of our PET samples and is a signature of induced gyrotropy. In some spectral regions, we observe a refractive index that is negative relative to the Cauchy approximation. We provide evidence that this is due to the ordering/texture of chiral molecules in PET films, suggesting that very highly textured PET films may exhibit a greater degree of negativity.

Fatty Acid Prediction in Bovine Milk by Attenuated Total Reflection Infrared Spectroscopy after Solvent-Free Lipid Separation.

In the present study, a novel approach for mid-infrared (IR)-based prediction of bovine milk fatty acid composition is introduced. A rapid, solvent-free, two-step centrifugation method was applied in order to obtain representative milk fat fractions. IR spectra of pure milk lipids were recorded with attenuated total reflection Fourier-transform infrared (ATR-FT-IR) spectroscopy. Comparison to the IR transmission spectra of whole milk revealed a higher amount of significant spectral information for fatty acid analysis. Partial least squares (PLS) regression models were calculated to relate the IR spectra to gas chromatography/mass spectrometry (GC/MS) reference values, providing particularly good predictions for fatty acid sum parameters as well as for the following individual fatty acids: C10:0 (R2P = 0.99), C12:0 (R2P = 0.97), C14:0 (R2P = 0.88), C16:0 (R2P = 0.81), C18:0 (R2P = 0.93), and C18:1cis (R2P = 0.95). The IR wavenumber ranges for the individual regression models were optimized and validated by calculation of the PLS selectivity ratio. Based on a set of 45 milk samples, the obtained PLS figures of merit are significantly better than those reported in literature using whole milk transmission spectra and larger datasets. In this context, direct IR measurement of the milk fat fraction inherently eliminates covariation structures between fatty acids and total fat content, which poses a common problem in IR-based milk fat profiling. The combination of solvent-free lipid separation and ATR-FT-IR spectroscopy represents a novel approach for fast fatty acid prediction, with the potential for high-throughput application in routine lab operation.

Metastable growth and infrared spectra of CuB2O4:Ni single crystals

The formation of CuB2O4:Ni crystals in fluxes based on Li2WO4–Bi2O3–WO3 has been studied. A distinctive feature of the used flux growing mode is the metastable nature of nucleation. IR reflection and transmission spectra are presented.

Synthesis and Investigation of Magnesium–Aluminum Nanopowders and Ceramics Activated by Copper

Nanopowders of two crystalline phases, magnesium–aluminum spinel (98 wt %), and cuprite (2 wt %) have been obtained by laser evaporation of a solid target, which is a mechanical mixture of simple oxides (MgO, Al2O3, CuO). These nanopowders have been used to prepare test samples of transparent Cu:MgAl2O4 ceramics, the IR transmission spectra of which revealed two new strong absorption bands at λ1 ≈ 1.55 (1.45) μm and λ2 ≈ 3.45 (3.03) μm, corresponding to transitions between the Stark levels 2E( $${\text{t}}_{2}^{6}$$ e3) and 2T2 ( $${\text{t}}_{2}^{5}$$ e4) of Cu2+ ions in octahedral and tetrahedral positions, respectively.

Remediation of Wastewater from Chlorpyrifos Pesticide by Nano-Gold Photocatalyst

AbstractSuccessful disintegration of Chlorpyrifos pesticide by nearly monodisperse nano-gold photcatalyst (∼10 nm) for remediation of wastewater has been reported in current studies. Nano-Gold dispersion reaction with Chlorpyrifos solutions completes in 45 minutes at ambient temperature under the normal daylight and exhibit systematic variations in the solution color from wine red to pink to light sky blue and finally transforming into a transparent solution with fine precipitates. UV-Vis absorption studies correlates well with the systematic color changes as observed in the nano-gold treated Chlorpyrifos solutions with time. The characteristic localized surface plasmon resonance peak of nanogold dispersion observed at 529 nm red shifts to weak, medium and strong intensity peaks at ∼ 640 nm, 740 nm and 890 nm on increasing chlorpyrifos concentration owing to the aggregation of gold nanoparticles in small to bigger sized clusters. The fine turbidity in final transparent solution further confirms the aggregation of nanogold particles into stable bigger ensembles. IR transmission spectra of final transparent solutions showed disappearance of Chlorpyrifos νC-Cl and phosphorothioate functional group peaks indicating degradation of chlorpyrifos.

Influence of the Heat Treatment Conditions on the Elemental Composition and Spectral Properties of Composite Materials Based on Silicate Porous Glass Doped by AgI and Er3+ Ions

Composite materials (CMs) doped by AgI and Er3+ ions are synthesized based on high-silica porous glass matrices. The structures of the CMs are investigated by IR spectroscopy in the frequency range 1100–400 cm–1. The IR transmission spectra of the CMs exhibit bands corresponding to vibrations of the Ag–O, Ag–O–Ag, Er–O–H, and Er–O bonds. In addition, bands that are caused by the presence of Ag2O, AgI, and Er2O3 are found. Energy-dispersive X-ray spectroscopy shows that the conditions of treatment of CMs with heat have an effect on the concentration distribution of elements over the thickness of the samples.