High-resolution IR Research Articles

Shape-controlled TiO2nanoparticles and TiO2P25 interacting with CO and H2O2molecular probes: a synergic approach for surface structure recognition and physico-chemical understanding

Integrated studies of CO on truncated bipyramidal TiO(2) anatase nanoparticles mainly exposing smooth (101) surfaces provide the missing link between TiO(2) single crystals and commercial TiO(2) nanopowders with complex morphology. The synergy among high resolution transmission electron microscopy, IR spectroscopy and modeling correlates adsorbed CO stretching frequency to anatase surface types, and reveals how disorder of the adsorbed CO layer affects CO/TiO(2) IR bands. Comparison of the two TiO(2) nanoparticle types highlights the role of low coordination Ti(4+) sites selectively present on TiO(2) P25 in the photocatalytic decomposition of H(2)O(2), an important Reactive Oxygen Species (ROS) formed in photocatalytic processes.

19 Quantum chemical studies on the formamide-based origin of life

Recently, we have applied quantum chemical calculations to supplement the experimentally available information on the prebiotic synthesis of nucleic acids with a molecular-level insight into the structure, energy, electronic structure, and spectroscopic properties of the compounds involved in these processes. In particular, in the presentation, we will focus on our studies related to the formamide-based origin of life. We will discuss the mechanism of the formamide-based synthesis of nucleobases suggested by Saladino et al. (2007). We show that the computed activation energy of the experimentally proposed pathway is noticeably higher than that of the HCN-based synthetic route, but it is still feasible under the experimental conditions of the Saladino synthesis. Our calculations thus demonstrate that the experimentally suggested reaction path without the involvement of aminoimidazole–carbonitrile intermediates is also a viable alternative for the nonaqueous synthesis of nucleobases (Šponer et al., 2012). Further, we have used quantum chemical calculations to interpret the results of high-resolution infrared spectra obtained for an icy mixture of formamide and an FeNi meteoritic material treated with high-energy laser pulses (Ferus et al., 2012). In this joint experimental-theoretical study, we have identified a new reaction channel for the formation of nucleobases from formamide ices, which might be highly relevant for the formation of nucleobases under a high-energy impact event, e.g. an atmospheric breakup of an icy extraterrestrial body. We have also shown that the theoretically proposed reaction route is highly realistic, because we could detect some of the theoretically proposed key intermediates using high-resolution IR spectroscopy. Thus, formation of nucleobases from formamide in a high-energy impact event may give new, astrobiological dimensions to the increasingly popular idea of formamide-based life originally suggested by Saladino et al., 2007.

HIGHLY DEPLETED ETHANE AND MILDLY DEPLETED METHANOL IN COMET 21P/GIACOBINI-ZINNER: APPLICATION OF A NEW EMPIRICAL ν2-BAND MODEL FOR CH3OH NEAR 50 K

We obtained infrared spectra of Comet 21P/Giacobini-Zinner (hereafter 21P/GZ) using NIRSPEC at Keck II on UT 2005 June 3, approximately one month before perihelion, that simultaneously sampled H2O, C2H6, and CH3OH. Our production rate for H2O (3.885?? 0.074?? 1028?molecules?s?1) was consistent with that measured during other apparitions of 21P/GZ as retrieved from optical, infrared, and radio observations. Our analysis also provided values for rotational temperature (T rot?= 51?? 3?K) and the abundance ratio of ortho and para spin populations for water (OPR?= 2.99?? 0.23, implying a spin temperature exceeding 50?K). Six Q-branches in the ?7 band of C2H6 provided a production rate (5.27?? 0.90?? 1025?s?1) that corresponded to an abundance ratio of 0.136?? 0.023?? 10?2 relative to H2O, confirming the previously reported strong depletion of C2H6 from IR observations during the 1998 apparition, and in qualitative agreement with the depletion of C2 known from optical studies of 21P/GZ. For CH3OH, we applied our recently published quantum model for the ?3 band to obtain a rotational temperature (48+10/?7?K) consistent with that obtained for H2O. In addition, we developed a new empirical model for the CH3OH ?2 band, based on observations of Comet 8P/Tuttle with NIRSPEC. The application of our ?2 model to 21P/GZ yielded a production rate in agreement with that obtained from the ?3 band. Combining results from both ?2 and ?3 bands provided a production rate (47.5?? 4.4??1025?s?1) that corresponded to an abundance ratio of 1.22?? 0.11?? 10?2 relative to H2O in 21P/GZ, indicating mild depletion of CH3OH. Together with observations of 21P/GZ in 1998, our study provides a measure of primary volatile production rates for this Jupiter family comet over multiple apparitions using high-resolution IR spectroscopy.

Detection and structure elucidation of hydroxythiovardenafil as an adulterant in a herbal dietary supplement

A new derivative of vardenafil was detected in an alleged herbal dietary supplement and identified as 2-(2-ethoxy-5-(4-(2-hydroxyethyl)piperazin-1-ylsulfonyl)phenyl)-5-methyl-7-propyl-imidazo[1,5-f][1,2,4]triazin-4(3H)-thione. Structure elucidation was carried out by LC–UV–MS/MS and NMR. Results obtained with high resolution MS and IR spectroscopy confirmed the proposed chemical structure. The compound was distinguished from hydroxyvardenafil, a second active substance identified in the same product, by the conversion of the oxo group to a thio group on the imidazo-triazin moiety. Hydroxythiovardenafil was therefore suggested as a proprietary name for the new molecule. This is the first paper to describe a thio-analog of vardenafil in a commercially available product.

The interaction of thermocapillary perturbations with 3D waves in a heated falling liquid film

The evolution of three-dimensional (3D) waves into thermocapillary-wave structures in a locally heated water film flowing down a vertical plate has been experimentally studied. The interaction of hydrodynamic perturbations with thermocapillary instabilities was monitored using a high-speed high-resolution IR imager. The existence of thermocapillary structures has been observed for the first time at high Reynolds numbers (Re = 150) in regime A, which is characterized by high temperature gradients on the film surface and a definite value of the “most dangerous” wavelength of instability that arises when the heat flux density exceeds a certain threshold. It is established that structures periodically appear in which the distance between temperature maxima is much shorter than that observed before. As the heat flux density is increased, the thermal entry length exhibits a sharp drop when thermocapillary instabilities arise in the vicinity of the upper edge of the heater.

Isolation and characterization of propoxyphenyl linked sildenafil and thiosildenafil analogues in health supplements

Two new phosphodiesterase-5 inhibitors (PDE-5) which consist of one sildenafil analogue and one thiosildenafil analogue have been found in heath supplements. The structural properties of these analogues have been elucidated by NMR, high resolution MS, MS(2), UV and IR spectroscopy. The sildenafil analogue is very similar to aildenafil and the thiosildenafil analogue is similar to thioaildenafil, except the ethoxy group bonded to phenyl ring is replaced by a propoxy group. Hence, the sildenafil analogue is named as propoxyphenyl aildenafil or propoxyphenyl methisosildenafil and the thiosildenafil analogue as propoxyphenyl thioaildenafil or propoxyphenyl thiomethisosildenafil.

Hydrothermal synthesis of a nanostructured TiO2-based material in the presence of chitosan

Quasi-one-dimensional TiO2-based nanostructures have been produced through hydrothermal treatment-without additives and in the presence of chitosan—of anatase nanopowder synthesized by an electrochemical sol-gel process. The morphology, phase composition, and structure of the hydrothermal synthesis products were studied by various physicochemical characterization techniques, including high-resolution electron microscopy, X-ray diffraction, and IR spectroscopy. The results demonstrate that the forming one-dimensional structures are isostructural with β-titanic acid, H2Ti3O7. Heat treatment at t ≥ 500°C yields a mixture of sodium polytitanates, NayTixO2x + 1, with y = 0.5–2 and x = 2–5. The surface morphology and shape of the nanostructures persist up to 700°C. The key features of the formation of quasi-one-dimensional TiO2-based structures in the presence of chitosan have been identified.

Cobalt boride catalysts for hydrogen storage systems based on NH3BH3 and NaBH4

The catalytic activity of cobalt borides forming in situ under conditions of NH3BH3 and NaBH4 hydrolysis have been investigated. The reaction properties of the catalysts depend on the nature of the hydride. According to high-temperature X-ray diffraction, thermal analysis, high-resolution transmission electron microscopy, IR spectroscopy, and chemical analysis data, the nature of the hydride determines the particle size, chemical composition, and crystallization properties of the cobalt borides.

High resolution IR observations of the starburst ring in NGC 7552

We observed the ring galaxy NGC 7552 with the mid-infrared (MIR) instrument VISIR at an angular resolution of 0.3"- 0.4" and with the near-infrared (NIR) integral-field spectrograph SINFONI on the VLT, and complement these observations with data from ISO and Spitzer. The starburst ring is clearly detected at MIR wavelengths at the location of the dust-extincted, dark ring seen in HST observations. This "ring", however, is a rather complex annular region of more than 100 parsec width. We find a large fraction of diffuse [Ne II] and PAH emission in the central region that is not associated with the MIR peaks on spatial scales of \sim30 pc. We do not detect MIR emission from the nucleus of NGC 7552, which is very prominent at optical and NIR continuum wavelengths. However, we have identified nine unresolved MIR peaks within the ring. The average extinction of these peaks is A(V)=7.4 and their total infrared luminosity is L(IR) = 2.1*10^10 Lo. The properties of these peaks are typical for MIR-selected massive clusters found in other galaxies. The ages of the MIR-selected clusters are in the range of 5.9\pm0.3 Myr. The age spread among the clusters of 0.8 Myr is small compared to the travel time of \sim5.6 Myr for half an orbit within the starburst ring. We find no strong evidence for a scenario where the continuous inflow of gas leads to the ongoing formation of massive clusters at the contact points between galactic bar and starburst ring. Instead, it appears more likely that the gas density build up more gradually over larger ring segments, and that the local physical conditions govern cluster formation. We note that the fundamental limitation on the accurate derivation of cluster age, mass and IMF slope is the lack of higher angular resolution.

Synthesis and characterization of novel N-acyl cyclic urea derivatives

A series of novel N-acyl cyclic urea derivatives (3a-3l) have been synthesized by the reactions of 1-((6-chloropyridin-3-yl)methyl)imidazolidin-2-one (1) with various acyl chlorides in the yields of 35-95%. Subsequently, N-acyl cyclic urea derivatives containing α-tertiary amine (5a-5k) have been synthesized by the nucleophilic substitution reaction of 1-(2-haloacetyl)-3-((6chloropyridin-3-yl)methyl)imidazolidin-2-one (3e or 3f) with various secondary amines in the yields of 49-86%. The synthesized compounds were characterized by 1 H NMR spectroscopy, 13 C NMR spectroscopy, high-resolution mass spectroscopy, IR and elemental analysis.

Platinum complexes bearing 2,2′-dipyridylamine ligand

The replacement of the iodide ligands in the complex [PtI2(dpa)] (1) (dpa is 2,2′-dipyridylamine) by silver triflate in acetonitrile afforded the compound [Pt(dpa)(MeCN)2](SO3CF3)2 (2). Homoleptic complexes [Pt(dpa)2](X)2 (3·(X)2) were synthesized by the treatment of [PtI2(dpa)] (1) with 2,2′-dipyridylamine in the presence of silver salts AgX in methanol (X = NO3) or acetonitrile (X = SO3CF3). The deprotonation of the complex [3](SO3CF3)2 to give the homoleptic complex [Pt(dpa-H)2] (4) was performed by two methods, e.g., by the treatment of [3](SO3CF3)2 with 2 equiv. of NaOH in methanol or by the addition of excess Et3N to a suspension of [3](SO3CF3)2 in methanol. The structures of compounds 1–4 were established by elemental analyses, high resolution electrospray ionization mass spectrometry, IR and NMR spectroscopy; the crystal structure of complexes [2](SO3CF3)2, [3](NO3)2·H2O, [3](SO3CF3)2·2H2O, and 4 were determined by single-crystal X-ray diffraction.

Structural elucidation of impurities in 5-n-butyl-4-{4-[2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (Ib), a novel nonpeptide angiotensin AT1 receptor antagonist

5-n-butyl-4-{4-[2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (Ib), a new nonpeptide angiotensin AT1-receptor antagonist, has been observed to play a positive role in the treatment of hypertension in preclinical tests. Four process impurities of Ib were detected by LC-UV and LC/ESI-MS, and the impurities isolated by preparative HPLC chromatography were characterized by LC-MS/MS, high resolution MS (HRMS), NMR and IR analyses. The structures of impurities were confirmed as 5-n-butyl-4-{4-[2-chloro-5-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (I), 5-n-butyl-4-{4-[2-bromo-5-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (II), 5-n-butyl-4-{4-[4-chloro-2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (III) and 5-n-butyl-4-{4-[4-bromo-2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (IV), respectively. All of the four impurities were produced as the by-products of the bromination reaction by NBS (N-bromosuccinimide) in the synthesis of Ib.

A High-Resolution UWB IR Superregenerative Receiver Front End With an SRD Quench Shaper

We present a simple receiver front end that makes use of the baseband superregeneration principle to detect ultrawideband (UWB) impulse radio signals. The UWB antenna is directly connected to the core circuit consisting of a resistor-capacitor (RC) network coupled to a negative resistance that varies under the control of an external quench generator. Due to a step-recovery-diode quench shaper, 50-ps time-domain sensitivity windows are generated that filter the received pulses and reject noise and interference. The circuit achieves high gain, exhibits automatic gain control, and directly demodulates binary phase modulations.

Mid-infrared spectroscopy of molecular ions in helium nanodroplets

High resolution IR spectra of aniline, styrene, and 1,1-diphenylethylene cations embedded in superfluid helium nanodroplets have been recorded in the 300-1700 cm(-1) range using a free-electron laser as radiation source. Comparison of the spectra with available gas phase data reveals that the helium environment induces no significant matrix shift nor leads to an observable line broadening of the resonances. In addition, the IR spectra have provided new and improved vibrational transition frequencies for the cations investigated, as well as for neutral aniline and styrene. Indications have been found that the ions desolvate from the droplets after excitation by a non-evaporative process in which they are ejected from the helium droplets. The kinetic energy of the ejected ions is found to be ion specific and to depend only weakly on the excitation energy.

High Resolution Radio and IR Observations of AGB Stars

AbstractAsymptotic Giant Branch Stars (AGB) are evolved, mass losing red giants with tenuous molecular envelopes which have been the subject of much recent study using infrared and radio interferometers. In oxygen rich stars, radio SiO masers form in the outer regions of the molecular envelopes and are powerful diagnostics of the extent of these envelopes. Spectroscopically resolved infrared interferometry helps constrain the extent of various species in the molecular layer. We made VLBA 7 mm SiO maser, Keck Interferometer near IR and VLTI/MIDI mid IR high resolution observations of the stars U Ari, W Cnc, RX Tau, RT Aql, S Ser and V Mon. This paper presents evidence that the SiO is depleted from the gas phase and speculate that it is frozen onto Al2O3 grains and that radiation pressure on these grains help drive the outflow.

High Resolution IR Spectroscopy of the C–H Stretch Bands of Benzene Monomer and Dimer in Helium Nanodroplets

Abstract The IR spectrum of benzene and benzene dimer embedded in superfluid helium droplets in the region of the C–H stretch vibration (3000–3110 cm-1) was observed. By analyzing the pressure dependence of the spectra it was possible to assign these spectra to benzene monomer and dimer. Based on a comparison of the observed position of the dimer bands to experimental bands recorded in the gas phase and to theoretical frequency predictions the authors assign these to the tilted T-shaped benzene dimer structure. None of the other two possible structures (PD or PTS) were found. The above assignment is firm. For the monomer, we find in helium nanodroplets a splitting of the ν 8+ν 19 combination band observed in the gas phase. We assign this to an additional Fermi resonance which is caused by the matrix shift in helium nanodroplets.

Synthesis, Crystal Structure and Biological Activity of N′-tert-butyl-N-(3-methoxylbenzoyl)-N-(4-methyl-1,2,3-thiadiazole-5-formylhydrazine

The title compound, N′-tert-butyl-N-(3-methoxylbenzoyl)-N-(4-methyl-1,2,3-thiadiazole-5-formylhydrazine (C16H20N4O3S) was prepared from the reaction of 4-methyl-1,2,3-thiadiazole-5-carbonyl chloride with N′-tert-Butyl-3-methoxylbenzohydrazine, and its structure was characterized by 1Hydrogen Nuclear Magnetic Resonance, High-Resolution Mass Spectrometry, IR spectra, and single crystal X-ray diffraction. The crystal of the title compound belongs to monoclinic system, space group P 21/c with cell parameters a = 17.986(2) A, b = 8.0180(10) A, c = 12.0190(14) A, α = 90°, β = 91.160(5)°, γ = 90°, V = 1732.9(4) A3, Z = 4, D c = 1.335 g/cm3, μ (Mo Ka) = 0.209 mm−1, F (000) = 736, R = 0.0367 and wR = 0.0932. X-ray diffraction analysis indicates that all rings in the title compound are non-planar. The bioassay results indicated that, the title compound had good fungicide activity against Sclerotinia sclerotiorum, certain extent of insecticidal activity against Plutella xylostella L. .

Road Tracking from High resolution IRS And IKONOS Images Using Unscented Kalman Filtering

A typical way to update map is to compare recent satellite images with existing map data, detect new roads and add them as cartographic entities to the road layer. At present image processing and pattern recognition are not robust enough to automate the image interpretation system feasible. For this reason we have to develop an image interpretation system that rely on human guidance. More importantly road maps require final checking by a human due to the legal implementations of error. Our proposed technique is applied to IRS and IKONOS images using Unscented Kalman Filter(UKF) . UKF is used for tracing the median axis of the single road segment. The Extended Kalman Filter (EKF) is probably the most widely used estimation algorithm for road tracking. However, more than 35 years of experience in the estimation community has shown that is difficult to implement and is difficult to tune. To overcome this limitation,UKF is introduced in road tracking which is more accurate, easier to implement, and uses the same order of calculations as linearization. The principles and algorithm of EKF and UKF were also discussed. The core of our system is based on profile matching.UKF traces the roadbeyond obstacles and tries to find the continuation of the road finding all road branches initializing at the road junction.The completeness and correctness of road tracking from the IRS and IKONOS images were also compared.

Citropremide and Citropridone: A New Ceramide and a New Acridone Alkaloid from the Stem Bark of Citropsis gabunensis

AbstractThe structure elucidation and complete 1H‐ and 13C‐NMR assignments are reported for two new compounds: the ceramide citropremide (1), and the acridone alkaloid citropridone (2). Both of these secondary metabolites were isolated from the stem bark of Citropsis gabunensis. High‐resolution mass, IR and UV spectrometry, and NMR experiments including COSY, HMQC, and HMBC were used for the determination of the structures and NMR spectral assignments.

Hydrocracking of vacuum gas oil in the presence of supported nickel-tungsten catalysts

The supports containing 70% Al2O3 and 30% β zeolite (AZ-1 and AZ-2), which differed in mixing procedures, and the Ni-W/AZ-1 and Ni-W/AZ-2 catalysts were characterized using an adsorption technique, high-resolution electron microscopy, IR spectroscopy, and X-ray photoelectron spectroscopy and tested in the hydrocracking reaction of vacuum gas oil (VGO). It was found that the supports differed in texture characteristics and surface Lewis acidity at the same composition and similar concentrations of Bronsted acid sites. The formation of Ni-W-S sulfide species on the surfaces of both of the supports occurred in different manners: multilayer Ni-W-S sulfide species were formed on AZ-1 (Ssp = 220 m2/g), whereas single-layer species were mainly formed on AZ-2 (Ssp = 380 m2/g). It was found that catalysts containing multilayer Ni-W-S sulfide species, which were characterized by a higher degree of sulfidation, provided a higher yield of diesel fuel upon the hydrocracking of VGO, whereas catalysts containing single-layer Ni-W-S sulfide species were more active in the reactions of VGO hydrodesulfurization and hydrodenitration.