Additional Absorption Band Research Articles

Structure and electronic properties of conducting, ternary TixTa1−xN films

We report on the electronic structure and optical properties of conducting ternary transition metal nitrides consisting of metals of different groups of the periodic table of elements. For the study of the bonding, electronic structure, and optical properties of conducting TixTa1−xN film growth, optical spectroscopy and ab initio calculations were used. Despite the different valence electron configuration of the constituent elements, Ta(d3s2) and Ti(d2s2), we show that TiN and TaN are completely soluble due to the hybridization of the d and sp electrons of the metals and N, respectively, that stabilizes the ternary TixTa1−xN systems to the rocksalt structure. The optical properties of TixTa1−xN have been studied using spectroscopic methods and detailed electronic structure calculations, revealing that the plasma energy of the fully dense TixTa1−xN is varying between 7.8 and 9.45 eV. Additional optical absorption bands are manifested due to the N p→Ti/Ta d interband transition the t2g→eg transition due to splitting of the metals’ d band, with the major exception of the Ti0.50Ta0.50N, where the eg unoccupied states are not manifested due to the local structure of the ternary system; this finding is observed for the first time and proves previous assignments of optical transitions in TaN.

Photon cascade emission of [formula omitted] ion in alkaline-earth fluorides

Absorption, emission, excitation spectra of CaF 2 , SrF 2 , BaF 2 crystals doped by PrF 3 in concentration ranging from 0.005% to few molar % were studied in 1.4–10 eV spectral region. Specific type of Pr centres possessing photon cascade emission (PCE active) was observed in all crystals. Concentration of centres monitored by excitation and emission spectra grows superlinearly with increasing of Pr concentration in SrF 2 and BaF 2 crystals. A new additional absorption band at 7.0 eV which coincided with excitation band of PCE-active centres was observed in CaF 2 – Pr crystals. The absorption coefficient of this band grows twice that coefficient of 5.7 eV band of single Pr centres.

Spectrodensitometry Application to Analytical Identification of Estradiol, Hydrocortisone, Testosterone and Cholesterol on Diol Plates

The selected steroid compounds such as: estradiol (E), hydrocortisone (H), testosterone (T), and cholesterol (CH) were separated by using thin-layer chromatography on glass plates precoated with Diol F254s (E. Merck, #1.05636) and using a chloroform as mobile phase. The densitometric detection of these compounds with and without the use of sulphuric acid solutions as visualizing reagents was compared. A robust and sensitive detection procedure for selected steroid compounds using the sulphuric acid as a visualizing reagent was described. Spot intensities on the plates were quantified after dipping in sulphuric acid solutions and heating at temperatures from 80°C to 140°C for times ranging from 5 to 30 min. The best detection conditions for high signal intensity [AU] were determined. Particularly robust and sensitive detection of investigated compounds separated was observed by dipping the plate for 15 s in the solution of sulphuric acid in methanol in the volume composition 1:19, and for temperature equal to 120°C and for heating for 10 min. The spectrodensitograms of hydrocortisone, estradiol, testosterone, and cholesterol on DiolF254 plates and by the use of sulphuric acid as visualizing reagents are different than the spectrodensitograms obtained on the plate without the use of a visualizing reagent. The obtained spectrodensitograms of investigated compounds after the detection with the use of sulphuric acid as visualizing reagents differ in the number and intensity of additional absorption bands. This fact has analytical and pharmaceutical significance in the identification of hydrocortisone, estradiol, testosterone, and cholesterol. Comparison and characterization of chromatographic spots of examined compounds on the basis of resolution (RS), separation factor (α), constant of the pair separation (), and ΔRF values were discussed. It was stated, that the resolution Rs values are similar at the wavelengths 250, 275, 300, 325, 375, and 400 nm for the particular separated compounds analyzed after the use of sulphuric acid solution as visualizing reagent.

Structural and electronic properties of ZnO polycrystals doped with Co

Zn1−xCoxO samples were prepared by a standard solid-state reaction method.Zn1−xCoxO crystals in the wurtzite structure were obtained with a Co composition of up to 22.1%. Thea- andc-axis lengths increased and decreased, respectively, with an increase inCo composition. Raman spectra showed systematic broadening of theE2 (high) phonon mode associated with the increase in Co composition, and electronictransitions of Co in the oxygen tetrahedron were observed in optical absorptionmeasurement. These results indicated systematic substitution of Co into the Zn sites.Furthermore, an additional broad absorption band at 2.4–3.3 eV corresponding to thecharge transfer (CT) process was also observed. The Raman spectra showed strong enhancement of the LOphonon due to a resonant Raman process induced with the coupling of the LOphonon and a photo-excited carriers mediated CT gap. These results suggest thepossibility of carrier-induced ferromagnetism based on double exchange interaction inZn1−xCoxO by visible light irradiation.

Optical properties, structural parameters, and bonding of highly textured rocksalt tantalum nitride films

Tantalum nitride is an interesting solid with exceptional properties and it might be considered as a representative model system of the d3s2 transition metal nitrides. In this work highly textured, stoichiometric, rocksalt TaN(111) films have been grown on Si(100) by pulsed laser deposition. The films were under a triaxial stress, which has been determined by the sin2 ψ method. The stress-free lattice parameter was found to be 0.433±0.001 nm, a value which has been also determined by ab initio calculations within the local spin density approximation. The optical properties of TaN have been studied using spectroscopic ellipsometry and detailed band structure calculations. The electron conductivity of TaN is due to the Ta 5dt2g band that intercepts the Fermi level and is the source of intraband absorption. The plasma energies of fully dense rocksalt TaN were found to be 9.45 and 9.7 eV based on the experimental results and ab initio calculations, respectively. Additional optical absorption bands were also observed around 1.9 and 7.3 eV and attributed to be due to crystal field splitting of the Ta 5d band (t2g→eg transition) and the N p→Ta d interband transition, respectively.

A novel, conjugated polymer containing fluorene, pyridine and unsymmetric carbazole moieties: Synthesis, protonation and electrochemical properties

An optically active, conjugated polymer bearing unsymmetric pendant carbazole chromophores was prepared via the Suzuki coupling of 9,9-dioctylfluorene-2,7-diboronic acid and a novel pyridine-containing compound. The polymer had a T g of 192 °C and T d10 at 437 °C under a nitrogen atmosphere and exhibited absorption bands at 320–400 nm and displayed an additional absorption bands at 380–480 nm after protonation with aq. HCl solution. The photoluminescence of the polymer shifted from 360–460 nm to 460–560 nm after protonation and the photoluminescence quantum yield of the polymer in THF solution was 0.88. The emission color of the polymer film changed from blue (439 nm) to yellow (551 nm) under an applied bias voltage of 2.5 V.

Influence of thickness and growth temperature on the optical and electrical properties of ZnO thin films

Zinc oxide transparent conductive thin films were prepared using the pulsed laser deposition technique onto Corning glass substrates and the dependences of their optical and electrical properties on the thickness and the growth temperature were investigated. As shown, the films present 90% average transmittance, their energy gap position depending on the film thickness and the growth temperature. An additional absorption band was also observed near 3.44 eV, the position of its maximum also depending on the growth parameters. Finally, the electrical properties of the films were found to be affected mainly by the growth temperature and less by the thickness.

Infrared absorption spectra of pure and doped YAl3(BO3)4 single crystals

Several weak absorption bands have been observed in the optical absorption spectra of pure and rare-earth-doped YAl3(BO3)4 single crystals in the 3350– 3650 cm−1 wave number region. Two of them, peaking at about 3377 cm−1 and 3580 cm−1 in the 8 K spectra, appear in most of the samples. They are tentatively attributed to the stretching mode of OH− ions incorporated in the crystal during the growth. An additional absorption band at about 5250 cm−1 at 8 K has also been detected in almost all samples. The temperature and polarization dependences of these bands, and their possible origin, are discussed.

Crystal chemistry of macfallite: Relationships to sursassite and pumpellyite

The crystal chemistry of macfallite from Keweenaw County, Michigan was studied using electron microprobe, thermogravimetry (TG), differential thermal analysis (DTA), powder Fourier transform infrared (FTIR) spectroscopy, and single-crystal X-ray diffraction methods. The chemical formula derived from the electron-microprobe measurements is (Ca2.03Na0.01)(Sigma 2.04)(Mn2.513+Al0.27Mg0.09Cu0.032+V0.013+)(Sigma 2.91)Si3.05O10.88(OH)(3.12) (Z = 2). An analysis using the intensities of the MnL beta and MnL alpha X-ray lines shows that most Mn is trivalent.The weight loss from TG measurement is 7.7 wt% at 1000 degrees C, most of which is interpreted to be due to the loss of structural OH groups. The crystal structure of macfallite [a = 8.959(3), b = 6.072(2), c = 10.218(4) angstrom, beta = 110.75(3)degrees, space group P2(1)/m], which is isostructural with sursassite, was refined using 1717 unique reflections to R = 4.1%. The site populations at the three independent octahedral sites, Mn1, Mn2, and Mn3, are Mn0.82Al0.06Mg0.09Cu0.03, Mn0.75Al0.25, and Mn0.95Al0.05, respectively. In agreement with a bond-valence analysis, three crystal-chemically different OH groups are located at the O6, O10, and O11 positions. The site O7 is mostly occupied by oxygen, but ininor amounts of hydroxyl may be located there as well. The powder FTIR spectrum in the region of the OH-stretching vibrations is characterized by three strong bands at 3413, 3376, and 3239 cm(-1) and an additional broad absorption band around 2900 cm(-1). The latter results from a relatively strong hydrogen bond, O6-H center dot center dot center dot O11, with a length of similar to 2.63 angstrom. Although there are three main hydroxyl groups occurring in macfallite, the exact number depends on the concentration of trivalent and divalent cations at the Mn1 site. If divalent cations occur at Mn1, a fourth OH group is necessary to maintain charge balance.

Activation of indigenous micorflora in oil-contaminated soils using photoluminescent films

A stimulating effect of sunlight transformed by a photoluminescent polymer film on the abundance dynamics and fermentation and respiration of indigenous microflora in oil-contaminated soils was investigated. Polymer film doped with photoluminophores based on inorganic Eu-complexes and common glasshouse film was used as a cover material for oil-contaminated soils at experimental and control sites. The application of photoluminescent film has been reported to stimulate a hundredfold growth of the microflora population, with the soil respiration intensity and catalase activity being increased by a factor of 2.5-3, respectively. The extents of biodegradation of petroleum hydrocarbons within 60 days were up to 70 and 30% of the overall background pollution level for the experimental and control site, respectively. Residual hydrocarbons extracted from samples of the contaminated soils were analyzed by infrared spectroscopy to show the appearance of additional absorption bands at 3350, 1600, and 1710 cm(-1), thus indicating the formation of metabolites during enzymatic oxidation of oil. Chromatographic data corroborated the occurrence of intense oxidation. The hydrocarbon biodegradation factor increases sixfold when the photoluminescent films are used.

Optical and Vibrational Properties of Thin Film Fullerene‐Zn(II) Tetraphenylporphyrin Complexes

In this work a novel material, fullerene‐Zn(II) tetraphenylporphyrin, is obtained and studied using UV‐Vis‐NIR absorption and Raman scattering methods. C60–ZnTPP thin films were produced by vacuum evaporation in hot‐wall reactor. The detection of the Ag2‐derived modes at 1460 and 1452 cm−1 in the Raman spectra manifests the charge‐transfer C60–ZnTPP complex formation. It is shown that additional absorption band at 1.38–1.53 eV observed in the films corresponds to the HOMO‐LUMO gap of C60–ZnTPP complex.

Effects of annealing treatment and gamma irradiation on the absorption and fluorescence spectra of Cr:GSGG laser crystal

The influence of annealing treatments and gamma-ray irradiation on the absorption and fluorescence spectra of Cr:GSGG crystals grown by the Czochralski method has been investigated. Two absorption bands located near 686 nm and 1050 nm were weakened markedly after the crystal was re-annealed in H2 atmosphere, which is due to the Cr4+ ions being de-oxidized into Cr3+ ions. The other two weak additional absorption bands induced by gamma-ray irradiation appearing near 310 nm and 480 nm are ascribed to the Fe2+ ions and F-type color centers, respectively. In particular, the gamma-ray irradiation with a dose of 100 Mrad has an effect of improving slightly the luminescence properties of Cr:GSGG crystals. The improvement mechanism is analyzed and discussed.

Sulphuric acid and Pt treatment of the photocatalytically active titanium dioxide

The study focuses on preparation, surface sites characterization and catalytic activity testing of pure (TiO 2), sulfated (TiO 2-S), loaded with 1 wt% Pt (TiO 2-Pt) and platinized/sulfated (TiO 2-Pt-S) high surface area anatase TiO 2 (100% anatase, 340 m 2/g). Sulfation was performed in 4 M H 2SO 4 solution and was not followed by a high temperature calcination. TEM images reveal the formation of a 3 Å amorphous layer over TiO 2 and TiO 2-Pt surface after their sulfation. Infrared spectrum of TiO 2-S contains additional absorption bands at 1235, 1333 and 1378 cm −1 that are assigned to S O stretch and distorted adsorbed SO 4 2 − vibrations. Low temperature CO adsorption and organic species adsorption from heptane solutions was performed for characterization of surface sites. TiO 2-S showed 3–5 cm −1 shift of adsorbed CO absorption band compared to initial TiO 2. The quantity of adsorbed CO increased by a factor of 1.5 for TiO 2-S indicating the increase of the quantity of surface Lewis sites. Sulfation also resulted in disappearance of OH groups having absorption band at 3690 cm −1 that was attributed to substitution by monodentate and bidentate sulfates. Four bases and two acids with different p K were used as probes in solution titration revealing that the quantity of different acid sites in TiO 2-S increases 1.07–2.17 times. Unexpectedly the quantity of acid and base sites in TiO 2-Pt-S decreases relatively to other catalysts studied. Catalytic activity of the samples in acetone deep photooxidation was measured as a function of acetone vapor concentration in a flow-circulating reactor. All dependences are well described by the one site Langmuir–Hinshelwood kinetic model. The maximum oxidation rate was similar for all samples and was observed at acetone concentration above 1500 ppm. However, in the range of low acetone concentration the activity of TiO 2-Pt-S was about triple of pure TiO 2 activity. The high activity of sulfated/platinized and sulfated TiO 2 is due to the much increased acetone adsorption constant.

Influence of Gamma-Ray Irradiation on Absorption and Fluorescent Spectra of Nd:YAG and Yb:YAG Laser Crystals

We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd3+:Y3A15O12 (Nd:YAG) and Yb3+:Y3A15O12 (Yb:YAG) crystals grown by the Czochralski method. Two additional absorption (AA) bands induced by gamma-ray irradiation appear at 255nm and 340 nm. The former is contributed due to Fe3+ impurity, the latter is due to Fe2+ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd:YAG crystal decrease after the irradiation of 100Mrad gamma-ray In contrast, the same dose irradiation does not impair the fluorescent properties of Yb:YAG crystal. These results indicate that Yb:YAG crystal possesses the advantage over Nd:YAG crystal that has better reliability for applications in harsh radiant environment.

Gamma-ray irradiation effect on the absorption and luminescence spectra of Nd:GGG and Nd:GSGG laser crystals

Laser crystals Nd 3+:Gd 3Ga 5O 12 (Nd:GGG) and Nd 3+:Gd 3Sc 2Ga 3O 12 (Nd:GSGG) were grown by Czochralski method. The influence of gamma-ray irradiation on their absorption and luminescence spectra has been investigated. Two additional absorption (AA) bands induced by gamma-ray irradiation appear in the spectra of Nd:GGG crystal while only a very weak AA band appears for the Nd:GSGG crystal. This indicated that Nd:GSGG crystal has stronger ability to resist the color center formation by irradiation. The intensity of the excitation and emission spectra of Nd:GGG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, a luminescence strengthening effect was observed in Nd:GSGG crystal after exposure to the same irradiation dose. The results showed that the Nd:GSGG crystal is a promising candidate used under radiation environments such as in outer space.

Fabrication and gas sensing property of honeycomb-like ZnO

We report the structural characterization and proposed formation mechanism of honeycomb-like ZnO conglomerations fabricated by direct precipitation method. X-ray diffraction (XRD), energy-disperse X-ray spectrometry (EDS), scanning electron microscopy (SEM) showed that the as-prepared ZnO calcined at 700 °C were micron sphere particles with honeycomb-like structure. In the UV–vis absorbing spectrum, it was observed that there is a new additional absorption band at 260 nm, and it was speculated that the absorption may be caused by defects on the surface and interface of honeycomb-like ZnO. The as-products showed high sensitivity and short response time to sulfured hydrogen gas. These results demonstrate that honeycomb-like ZnO conglomerations are very promising materials for fabricating H 2S gas sensors.

Influence of Impregnation of a Mixture of Silica Gel and Kieselguhr with Copper (II) Sulphate (VI) on Profile Change of the Spectrodensitograms and the RF Values of Nicotinic Acid and its Derivatives

Nicotinic acid and its derivatives were separated using adsorption TLC on aluminum plates precoated with a mixture of silica gel 60 and kieselguhr F254 non impregnated and impregnated with 2.5% and 5% aqueous solutions of CuSO4. The mixture of an acetone‐n‐hexane in different volume compositions was used as mobile phase. The obtained results of the investigations concerning the evaluation of chromatographic separations were considered in three groups, namely, 1st group: nicotinic acid (1), methyl nicotinate (2), ethyl nicotinate (3), isopropyl nicotinate (4), butyl nicotinate (5), hexyl nicotinate (6), benzyl nicotinate (7); 2nd group: nicotinic acid (1), nicotinamide (8), N‐methylnicotinamide (9), N,N‐diethylnicotinamide (10); and 3rd group: nicotinic acid (1), nicotinamide (8), 3‐pyridinecarbaldehyde (11), 3‐pyridinecarbonitrile (12), 3‐pyridylmethanol (13), methyl 3‐pyridyl ketone (14). Impregnation of the mixture of silica gel and kieselguhr with 2.5% and 5% aqueous solutions of CuSO4 causes a decrease of the RF values of the 1st, 2nd, and 3rd groups of the compounds in relation to the RF values of these substances obtained on non impregnated solid support. Impregnation with a water solution of copper (II) sulphate (VI) of the mixture of silica gel and kieselguhr worsens the separation of the 2nd and 3rd groups of the investigated compounds. Improvement of the chromatographic separations is observed only in the case of esters of nicotinic acid (1st group of compounds). It was found that the spectrodensitograms of the studied compounds on impregnated plates and by use of Rhodamine B as visualizing reagent were different than the spectrodensitograms obtained on the plates without use of a visualizing reagent. Spectra of the investigated compounds on non impregnated plates and impregnated with aqueous solution of CuSO4 and without the use of a visualizing reagent have two or three absorption bands. Investigated compounds on the plates impregnated with the aqueous solution of CuSO4 and by use of Rhodamine B as visualizing reagent have one additional absorption band at λ≈560 nm. This fact has analytical significance in the identification of the investigated substances.

High-pressure phase of natural fullerene C 60 in iridium-rich Cretaceous–Tertiary boundary layers of Deccan intertrappean deposits, Anjar, Kutch, India

We report here for the first time the presence of the natural, toluene-soluble C 60 and the toluene-insoluble high-pressure and temperature phase of fullerene C 60 in the carbonaceous matter extracted from the iridium-rich layers of the intertrappean sediments of Anjar, India. The toluene-insoluble form of fullerene is formed at high-temperature and pressure (HPT) and is distinguished from normal fullerene by UV–visible and Fourier-transform infrared (FT-IR) spectroscopic techniques. The C 60 fullerene has been identified by high-resolution electron-impact ionization mass spectrometric analysis, as well as by Fourier-transform infrared (FT-IR), UV–visible, and 13C-nuclear magnetic resonance (NMR) spectroscopy. In iridium-poor horizons of this section, fullerenes are absent, but complex hydrocarbons are sometimes present. The FT-IR spectroscopic studies on the insoluble fullerenes show strong absorption peaks at about 740 and 509 cm −1 and a number of weak peaks at 1380, 1300, 1205, 1120, 1000, 608, 554, and 441 cm −1, which are characteristic of a high-pressure and temperature C 60 fullerene. The UV–visible spectra of the toluene-soluble fullerene, as well as the insoluble fullerene, show strong absorption bands at 270 and 348 nm, which are characteristic of pristine fullerene C 60. The toluene-insoluble carbon-rich residue shows additional absorption bands at 710, 640, and 395 nm. These UV–visible bands independently confirm the presence of the high-pressure–temperature (HPT) phase of fullerene C 60. Conditions of high-pressure and temperature required for formation of the HPT fullerene phase can be created by an energetic impact event. Therefore, the presence of HPT fullerene in the KT boundary layer at Anjar is linked to the impact event at the KT transition.

Strong UV absorption and visible luminescence in ytterbium-doped aluminosilicate glass under UV excitation

A broad visible luminescence band and characteristic IR luminescence of Yb(3+) ions are observed under UV excitation in ytterbium-doped aluminosilicate glass. Samples made under both oxidizing and reducing conditions are analyzed. A strong charge-transfer absorption band in the UV range is observed for glass samples containing ytterbium. Additional absorption bands are observed for the sample made under reducing conditions, which are associated with f-d transitions of divalent ytterbium. The visible luminescence band is attributed to 5d-4f emission from Yb(2+) ions, and the IR luminescence is concluded to originate from a relaxed charge-transfer transition. The findings are important to explain induced optical losses (photodarkening) in high-power fiber lasers.

EPR and optical measurements of weakly doped LiNbO 3: Er

Optical spectroscopy measurements of the congruent LiNbO 3 (LN) single crystals, weakly doped with Er (0.1–0.3 wt%) and Er (0.3 wt%) and Yb (0.5 wt%), have been carried out. The shape of the optical absorption and additional absorption bands registered after γ-irradiation suggests the presence of Er 3+ ion pairs. EPR investigations were performed for LN single crystal doped with Er (0.1 wt%). Unusual behaviour of the temperature dependence of the intensity and linewidth of the main EPR line—corresponding to the fine transition of evenEr 3+—ions, is reported. The main EPR line appears to be a superposition of several paramagnetic centres originating from isolated evenEr 3+ ions and evenEr 3+– evenEr 3+ pairs of ions. In low temperature region (below 20 K), the main EPR signal is dominated by signals arising from evenEr 3+– evenEr 3+ pairs of ions. The inverse intensity of the EPR line at low temperature region fulfils the Curie–Weiss law and enabled to determine the Curie–Weiss constant Θ=1.5±0.5 K. The positive sign of Θ suggests that the ferromagnetic interactions arise in the system of evenEr 3+– evenEr 3+ ion pairs in LN. Our results suggest that the distribution of Er ions in congruent LN is not homogeneous and Er impurity ions can form clusters in host lattice even in the case of weak erbium doping.