Absorption spectroscopy

This study demonstrates that ultrasound rapidly degrades the energetic compounds RDX (cyclo-1,3,5-trinitramine-2,4,6-trimethylene) and ADN (ammonium dinitramide) in aqueous microheterogeneous media. The conditions for effective degradation of these nitramines, as monitored by UV absorption spectroscopy, were determined by varying sonication time, the heterogeneous phase and its suspension density, and the concentration of NaOH. In the presence of 5 mg/ml of aluminum powder and at pH $ 12 (10 mM NaOH), 74% of the RDX and 86% of the ammonium dinitramide (ADN) in near-saturated solutions decompose within the first 20 min of sonication (20 kHz; 50 W; 6 5°C). Sonication without Al powder and base yields minimal degradation of either RDX and ADN ($5-10%) or the nitrite/ nitrate ions that are expected byproducts during RDX and ADN degradation. Sonication at high pH in the presence of dispersed aluminosilicate zeolite, alumina, or titanium dioxide also yields minimal degradation. Preliminary electrochemical studies and product analyses indicate that in situ ultrasonic generation of metallic aluminum and/or aluminum hydride drives reductive denitration of the nitramines. Sonochemical treatment in the presence of a reductant offers an effective and rapid waste remediation option for energetic waste compounds. Published by Elsevier Science Ltd.

Photostructural defects resulting from exposure to intense near-infrared femtosecond radiation is studied in three a-SiO 2 glasses with different impurity levels. The photoinduced defects are studied by UV absorption spectroscopy and are correlated to the structural modifications in the glass matrix through Raman spectroscopy. Information in the dynamics of the defect generation is revealed by the small photon energy of IR femtosecond laser radiation.

In this study we report a systematic investigation of phthalocyanine (Pc) optical properties, showing that the effect of re-absorption of fluorescence plays a critical role in the line-shape of Pc optical spectra. We demonstrate that a strong dependence of the photoluminescence parameters on the concentration of phthalocyanines solution accounts for the apparent experimental evidence of a fluorescent dimer band in the emission at high concentrations. Despite a model based on fluorescent aggregates seems to describe the photophysical behavior of the system, additional experiments, such as electronic absorption spectroscopy, and fluorescence spectroscopy in which the optical pathlength inside the solution is suitably modified, provide a correct explanation of the observed optical behavior. We demonstrate that the shapes of optical spectra are completely independent on phthalocyanine aggregation state and are due only to experimental artifacts, i.e. inner filter effects.

Two new ruthenium(II) complexes [Ru(bpy) 2 (HBT)] 2þ (1) and [Ru(phen) 2 (HBT)] 2þ (2) (bpy ¼ 2,2 0bipyridine; phen ¼ 1,10-phenanthroline; HBT ¼ 11H, 13H-4, 5,9,10,12,14-hexaaza-benzo [b] triphenylene) have been synthesized and characterized by elemental analysis, mass spectra, 1 H NMR and cyclic voltammetry. The DNA binding property of the two complexes has been investigated employing absorption spectroscopy, fluorescence spectroscopy and viscosity measurements. Both complexes 1 and 2 have been found to prefer intercalative binding to DNA. The DNA binding constants for the two complexes have been measured to be 5.71 AE 0.20 Â 10 7 and 4.65 AE 0.20 Â 10 7 M À1 through ethidium bromide displacement method. Molecular modeling studies too indicate that both complexes 1 and 2 prefer intercalative binding to DNA and both these complexes exhibit similar DNA binding energies. Both complexes 1 and 2 bring about photocleavage of plasmid DNA when irradiated at 440 nm.

X-ray absorption near edge stru ture spectroscopy has been used to establish the chemical shifts of the technetium K edge in a range of compound \ containing Tc in a variety of formal oxidation states. The edge positions span 19.9 eV from Tc metal to N€L+Tc04. Strong correlation between chemical shift and formal oxidation state is observed. Extended X-ray absorptron fine structure (EXAFS) spectroscopy of Tc2(CO)10 indicates that multiple scattering along the Tc-C-gvector is more important than direct Tc. 0 scattering. TcOz is shown by EXAFS to possess a distorted rutile structure with a closest Tc-Tc distance of 2.61 A. This is rationalized in terms of the Goodenough model for bonding in transition metal dioxides.

The densities of NH and NH 2 radicals in an Ar-NH 3 plasma jet created by the expanding thermal plasma source were investigated for various source-operating conditions such as plasma current and NH 3 flow. The radicals were measured by cavity ringdown absorption spectroscopy using the ͑0,0͒ band of the A 3 ⌸ ← X 3 ⌺ − transition for NH and the ͑0,9,0͒-͑0,0,0͒ band of the à 2 A 1 ← X 2 B 1 transition for NH 2. For NH, a kinetic gas temperature and rotational temperature of 1750± 100 and 1920± 100 K were found, respectively. The measurements revealed typical densities of 2.5 ϫ 10 12 cm −3 for the NH radical and 3.5ϫ 10 12 cm −3 for the NH 2 radical. From the combination of the data with ion density and NH 3 consumption measurements in the plasma as well as from a simple one-dimensional plug down model, the key production reactions for NH and NH 2 are discussed.

The crystallinity degree of thin polyamide ®lms (PA66, 610 and 612) spin coated on four types of substrates are estimated. Two original methods based on the analysis of infrared spectra are proposed. The high sensitivity of polarization modulation re¯ection-absorption spectroscopy for the study of thin polymer ®lms leads to quantitative results. These two methods offer the possibility to estimate the degree of crystallinity by using infrared spectroscopy, independently of any other technique, if the crystallinity degree in the isotropic bulk state is known. Polyamides are spin coated, on the one hand, on inert and highly re¯ecting gold substrates, and on the other hand, on the same gold substrates grafted with different chemical functionality. Our calculations show a lower crystallinity degree for inert substrate and higher values for functionalized systems with respect to the bulk. These results suggest that the surface chemical grafts not only play the role of nucleation seeds, but also affect the crystalline morphology as seen by atomic force microscopy. q

A novel flexible tripodal ligand derived from 3-methylindole, (''InTREN" L), and its mononuclear Zn(II), Cu(II), Ni(II), Hg(II) and Pd(II) complexes are described. All compounds gave analytically pure solid samples. Characterisation of the compounds was accomplished by 1 H NMR, IR and absorption spectroscopies, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and elemental analysis and their geometry optimized using density functional theory (DFT).

The interpretation of UV-visible twilight absorption measurements of atmospheric chemical constituents is dependent on how well the optical path, or air mass factor, of light collected by the spectrometer is understood. A simple single scattering model and a Monte Carlo radiative transfer scheme have been develoj•ed to study the effects of multiple scattering, aerosol scattering, surface albedo and refraction on air mass tactors for scattered light observations. At fairly short visible wavelengths (less than about 450 nm), stratosphedc air mass factors are found to be relatively insensitive to multiple scattering, surface albedo and refraction, as well as aerosol scattering by background aerosols. Longer wavelengths display greater sensitivity to refraction and aerosol scattering. Tropospheric air mass factors are found to be highly dependent on aerosol scattering, surface albedo and, at long visible wavelengths (about 650 nm), refraction. Absorption measurements of NO 2 and 0 4 are shown to support these conclusions.

The paper presents opportunities of cavity enhanced absorption spectroscopy technique application in nitrogen oxides (NO x ) detection. In this method the concentration of an absorbing gas is determined by measure of decay time of the light pulse trapped in an optical cavity. The measurements are not sensitive to fluctuation of both laser power and photodetector sensitivity. The cavity enhanced absorption spectroscopy technique is a modification of cavity ring down spectroscopy technique where the off-axis adjustment of the resonator is used. NO x detection is carried out in the visible and infrared range. The signal is registered with a developed low noise photoreceiver. Features of the presented sensor show that it is possible to build a portable trace gases sensor. Its sensitivity could be comparable with chemical detectors. Such a system has several advantages: relatively low price, small size and weight, and detection possibility of other gases.

A U-type microemulsion of Brij 96 has been characterized with respect to the change in cosurfactant, oil chain length on dilution, water solubility, and water solubilization capacity. The phase behavior of the systems has been mapped with different oils. Several techniques, viz., conductivity, optical microscopy, dilution method, absorption, and FT-IR spectroscopy, have been used for microemulsion analysis. The equilibrium within the microemulsion droplets and liquid crystals has been visualized using optical microscopy. The microemulsions have evidenced volume-induced conductance percolation in all the cosurfactants (n 2 -n 6 alcohols). The energetics of transfer of alcohol from the bulk oil to the interface has been determined through dilution method. To gain insight into the microenvironment of microemulsion, two optical probes, hydrophilic (Methyl orange) and hydrophobic (Nile red), have been utilized in absorption spectroscopy. Lastly, FT-IR has been explored to observe the state and dissolution behavior of water with increasing weight fraction.

The electronic state spectroscopy of vinyl chloride, C 2 H 3 Cl, has been investigated by high resolution VUV photo-absorption spectroscopy in the wavelength range 115-300 nm (10.8-4.2 eV). New assignments are proposed for Rydberg series converging to the four lowest ionisation energies and their associated vibrational excitation is observed for the first time. Absolute cross-section values have been obtained allowing photolysis lifetimes to be derived in the Earth's troposphere and stratosphere.

Graphene is at the centre of nanotechnology research. In order to fully exploit its outstanding properties, a mass production method is necessary. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to ~0.01 mg/ml by dispersion and exfoliation of graphite in organic solvents such as N-methylpyrrolidone. This occurs because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energy matches that of graphene. We confirm the presence of individual graphene sheets with yields of up to 12% by mass, using absorption spectroscopy, transmission electron microscopy and electron diffraction. The absence of defects or oxides is confirmed by X-ray photoelectron, infra-red and Raman spectroscopies. We can produce conductive, semi-transparent films and conductive composites. Solution processing of graphene opens up a whole range of potential large-scale applications from device or sensor fabrication to liquid phase chemistry.

The solution-combustion synthesis (SCS) method was used to prepare silver nanoparticles using glycine and citric acid as fuels. The different combination of fuel to oxidant ratio was used to prepare Ag nanoparticles and its effect on optical spectra, structure and the morphology explored. The purposed method is rapid, effective, cheap and convenient. Silver nanoparticles with different sizes and shapes were synthesized depending upon the different oxidant/fuel ratios. The nanoparticles were characterized using transmission electron microscopy, X-ray diffraction and ultraviolet–visible absorption spectroscopy. Histograms were drawn to compare the mean particle size of synthesized nanoparticles. It was found that citric acid was better fuel as compared to glycine as it results in the more spherical symmetrical nanoparticles, which are supported by various characteristic studies.

This paper addresses the research question "Are more stringent exhaust emissions standards, as applied to light vehicle type approval, resulting in reduced vehicle pollution in an urban area?" The exhaust emissions of a sample of over fifty thousand road vehicles operating in London were measured using roadside remote sensing absorption spectroscopy techniques (infrared and ultraviolet), combined with Automatic Number Plate Recognition for vehicle identification. Levels of carbon monoxide (CO), hydrocarbons (HC), nitric oxide (NO), and smoke (particulate) exhaust emissions are reported by vehicle class, fuel type, and Euro emissions standard. Emissions from petrol cars of each pollutant were all observed to display a statistically significant reduction with the introduction of each successive Euro emissions standard from Euro 1 onwards. However, Euro 2 diesel cars were observed to emit statistically higher rates of NO than either Euro 1 or Euro 3 standard diesel cars. The study also confirms the continuing 'dieselisation' of the UK passenger car fleet. Mean NO emissions from Euro 4 diesel cars were found to be 6 times higher than Euro 4 petrol cars, highlighting the need to develop a sound understanding of the current and future 'in-use' emissions characteristics of diesel vehicles, and their influence on local air quality. Smoke emissions from TXII London taxis (black cabs) were found to be statistically higher than either earlier TX1 or later TX4 model variants, with possible implications for local air quality policy interventions such as maximum age limits for taxis.

Over the last half century, the most frequently used assay for chlorophylls in higher plants and green algae, the Arnon assay [Arnon DI (1949) Plant Physiol 24: 1-15], employed simultaneous equations for determining the concentrations of chlorophylls a and b in aqueous 80% acetone extracts of chlorophyllous plant and algal materials. These equations, however, were developed using extinction coefficients for chlorophylls a and b derived from early inaccurate spectrophotometric data. Thus, Arnon's equations give inaccurate chlorophyll a and b determinations and, therefore, inaccurate chlorophyll a/b ratios, which are always low. This paper describes how the ratios are increasingly and alarmingly low as the proportion of chlorophyll a increases. Accurate extinction coefficients for chlorophylls a and b, and the more reliable simultaneous equations derived from them, have been published subsequently by many research groups; these new post-Arnon equations, however, have been ignored ...

Planetary systems are angular momentum reservoirs generated during star formation. Solutions to three of the most important problems in contemporary astrophysics are needed to understand the entire process of planetary system formation: The physics of the ISM. Stars form from dense molecular clouds that contain ∼ 30% of the total interstellar medium (ISM) mass. The structure, properties and lifetimes of molecular clouds are determined by the overall dynamics and evolution of a very complex system – the ISM. Understanding the physics of the ISM is of prime importance not only for Galactic but also for extragalactic and cosmological studies. Most of the ISM volume (∼ 65%) is filled with diffuse gas at temperatures between 3000 and 300 000 K, representing about 50% of the ISM mass. The physics of accretion and outflow. Powerful outflows are known to regulate angular momentum transport during star formation, the so-called accretion–outflow engine. Elementary physical considerations show that, to be efficient, the acceleration region for the outflows must be located close to the star (within 1 AU) where the gravitational field is strong. According to recent numerical simulations, this is also the region where terrestrial planets could form after 1 Myr. One should keep in mind that today the only evidence for life in the Universe comes from a planet located in this inner disk region (at 1 AU) from its parent star. The temperature of the accretion–outflow engine is between 3000 and 10 7 K. After 1 Myr, during the classical T Tauri stage, extinction is small and the engine becomes naked and can be observed at ultraviolet wavelengths. The physics of planet formation. Observations of volatiles released by dust, planetesimals and comets provide an extremely powerful tool for determining the relative abundances of the vaporizing species and for studying the photochemical and physical processes acting in the inner parts of young planetary systems. This region is illuminated by the strong UV radiation field produced by the star and the accretion–outflow engine. Absorption spectroscopy provides the most sensitive tool for determining the properties of the circumstellar gas as well as the characteristics of the atmospheres of the inner planets transiting the stellar disk. UV radiation also pumps the electronic transitions of the most abundant molecules (H 2, CO, etc.) that are observed in the UV. Here we argue that access to the UV spectral range is essential for making progress in this field, since the resonance lines of the most abundant atoms and ions at temperatures between 3000 and 300 000 K, together with the electronic transitions of the most abundant molecules (H 2, CO, OH, CS, S 2, CO 2+, C 2, O 2, O3, etc.) are at UV wavelengths. A powerful UV-optical instrument would provide an efficient mean for measuring the abundance of ozone in the atmosphere of the thousands of transiting planets expected to be detected by the next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV mission would be optimal for identifying Earth-like candidates.

Simple strategies for producing silver and gold nanoparticles (AgNP and AuNP) along with the corresponding core shell nanoparticles (Au-Ag and Ag-Au) by reduction of the metal salts AgBF 4 and HAuCl 4 by NaBH 4 in water will be presented. The morphologies of the obtained nanoparticles are determined by the order of addition of reactants. The obtained NPs, with sizes in the range 3-40 nm, are characterized by transmission electronic microscopy (TEM) and UV-Vis absorption spectroscopy, so as to evaluate their qualities. Moreover, a direct electrochemical detection protocol based on a cyclic voltammetry in water solution that involves the use of glassy carbon electrode is also applied to characterize the prepared NPs. The developed NPs and the related electroanalytical method seem to be with interest for future sensing and biosensing applications including DNA sensors and immunosensors.

Novel bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) complexes with the formula, ML 3 , where M is Ga(III) or In(III), or of the formula, ML 2 where M is [VO] 2+ , have been synthesized and characterized by mass spectrometry, infrared and absorption spectroscopies, and elemental analysis. A new ligand, bis[4-acetyl-3-hydroxyphenyl]-1,6-heptadiene-3,5-dione (diacetylbisdemethoxycurcumin, DABC) was similarly characterized; an X-ray structure analysis was performed. Vanadyl complexes tested in an acute i.p. testing protocol in STZ-diabetic rats showed a lack of insulin enhancing potential. Vanadyl complexes were, however, more cytotoxic than were the ligands alone in standard MTT (3-[4,5-dimethylthiazole-2-yl]ate, -2,5-diphenyl-tetrazolium bromide) cytotoxicity testing, using mouse lymphoma cells. With the exception of DABC, that was not different from VO(DABC) 2 , the complexes were not significantly different from one another, with IC 50 values in the 5-10 lM range. Gallium and indium curcumin complexes had IC 50 values in the same 5-10 lM range; whereas Ga(DAC) 3 and In(DAC) 3 (where DAC = diacetylcurcumin) were much less cytotoxic (IC 50 = 20-30 lM). Antioxidant capacity was decreased in VO(DAC) 2 , Ga(DAC) 3 , and In(DAC) 3 , compared to vanadyl, gallium and indium curcumin, corroborating the importance of curcuminÕs free phenolic OH groups for scavenging oxidants, and correlated with reduced cytotoxic potential.

a b s t r a c t 2-Benzoylxanthone (BzX) was synthesized, characterized and used as type II photoinitiator (PI) in combination with triethylamine for the polymerization of methylmethacrylate (MMA). The photophysical/photochemical behaviour of the photoinitiator, the involved excited state and the reaction with the amine co-initiator was studied by means of absorption and nanosecond time-resolved absorption spectroscopy. Upon irradiation with 266 or 355 nm laser light, the triplet state 3 BzX* ( max = 355 nm and 530 nm) was generated as the only transient (lifetime of 22.7 s) in nitrogen saturated MeCN solution. 3 BzX* was confirmed through quenching experiments with oxygen, 2-methylbutadiene, perylene and MMA and spectral similarity to benzophenone triplet ( 3 BP*). The quantum yield of its formation (˚T = 0.8) and the molar absorption coefficient (ε = 7500 L mol −1 cm −1 ) was measured in MeCN. The triplet was photoreduced by triethylamine (TEA) via photoinduced electron/proton transfer giving the corresponding ketyl and ␣-amino ethyl radical ( • CHMe-NEt 2 ). From the reduction potential of BzX measured via cyclic voltametry (two cathodic peaks at −1.63 V and −1.91 V vs. Ag/AgCl), an exergonic electron transfer reaction results. The ketyl radical resembles the well-known benzophenone ketyl. In conclusion, the triplet 3 BzX* corresponds to an n → * transition localized on the benzoyl substituent and resembles the benzophenone triplet 3 BP* but deviates from the triplet state of xanthone ( 3 X*). This is supported through DFT/B3LYP calculations, viz., (i) fully ground and triplet state geometry optimizations show that charge and spin densities are localized on the benzoyl group, and (ii) calculation of the electronic transitions via TD-DFT at B3LYP/631G+(d) and PB1BPE/631G+(d) levels of theory shows the local character. Agreement with experiment is better by applying the conductor like polarized continuum model (CPCM) to consider the solvent effect (MeCN).

The CH radical production induced by 193 nm two-photon photolysis of CHCl 3 has been measured for the first time via the cavity ring-down absorption spectroscopy of its A-X bands, using a commercial nanosecond pulsed dye laser. The range of pressure and laser intensity, as well as the time window detection, have been carefully chosen to ensure a constant CH number density during the measurement and to avoid post-photolysis reactivity. Internal energy distribution of the CH(X 2 II) fragment has been derived from population distribution simulations, leading to an average vibrational temperature T vib = 1900 ± 50 K and rotational temperature T rot = 300 ± 20 K. Two competing mechanisms can be invoked for the CH production channel: either two-photon absorption via resonant excited states of CHCl 3 leading to dissociation of excited CHCl 3 , or two-photon sequential dissociation via the formation of the vibrationally excited CHCl 2 fragment. The latter mechanism is proposed to be the prominent process for CH formation.

The structural and spectroscopic properties of [Ru(phen) 2 (dppz)] 2+ and [Ru(tap) 2 (dppz)] 2+ (phen = 1,10phenanthroline; tap= 1,4,5,8-tetraazaphenanthrene; dppz = dipyridophenazine ) have been investigated by means of density functional theory (DFT), time-dependent DFT (TD-DFT) within the polarized continuum model (IEF-PCM) and quantum mechanics/molecular mechanics (QM/MM) calculations. The model of the Δ and Λ enantiomers of Ru(II) intercalated in DNA in the minor and major grooves is limited to the metal complexes intercalated in two guanine-cytosine base pairs. The main experimental spectral features of these complexes reported in DNA or synthetic polynucleotides are better reproduced by the theoretical absorption spectra of the Δ enantiomers regardless of intercalation mode (major or minor groove). This is especially true for [Ru(phen) 2 (dppz)] 2+ . The visible absorption of [Ru(tap) 2 (dppz)] 2+ is governed by the MLCT tap transitions regardless of the environment (water, acetonitrile or bases pair), the visible absorption of [Ru(phen) 2 (dppz)] 2+ is characterized by transitions to metal-to-ligand-charge-transfer MLCT dppz in water and acetonitrile and to MLCT phen when intercalated in DNA. The response of the IL dppz state to the environment is very sensitive. In vacuum, water and acetonitrile these transitions are characterized by significant oscillator strengths and their positions depend significantly on the medium with blue shifts of about 80 nm when going from vacuum to solvent. When the complex is intercalated in the guanine-cytosine base pairs the 1 IL dppz transition contributes mainly to the band at 370 nm observed in the spectrum of [Ru(phen) 2 (dppz)] 2+ and to the band at 362 nm observed in the spectrum of [Ru(tap) 2 (dppz)] 2+ .

Electronic state spectroscopy of CH3COOH has been investigated using Vacuum UltraViolet (VUV) photo-absorption spectroscopy in the energy range 3.5–10.6eV. The availability of a high-resolution photon beam (∼0.075nm) has allowed detailed analysis of the vibrational progressions and allowed us to propose, for the first time, new assignments for several Rydberg series. Excited states located in the 10–14eV region have been studied

Two new ditechnetium complexes possessing Tc-Tc bonds with a formal bond order of 3.5 have been prepared in high yield. Mild chemical oxidation of Tc 2 Cl 4 (PMe 2 Ph) 4 with ferrocenium hexafluorophosphate in acetonitrile produces [Tc 2 Cl 4 (PMe 2 Ph) 4 ][PF 6 ] (1) in 82% yield. One-electron oxidation of Tc 2 Cl 4 (PMe 2 Ph) 4 by ferrocenium hexafluorophosphate in the presence of ppnCl (ppn ) bis(triphenylphosphine)iminium) yielded the neutral compound Tc 2 Cl 5 (PMe 2 Ph) 3 (2) in 89% yield. Both species are paramagnetic, as evidenced by EPR spectroscopy, and possess a σ 2 π 4 δ 2 δ* ground state electronic configuration on the basis of structural and spectroscopic data. The solid state structures of three forms of 1 have been investigated by X-ray crystallography together with the structure of 2. The crystallographic parameters for these structures are as follows: [Tc 2 Cl 4 (PMe 2 Ph) 4 ][PF 6 ] (1a, orthorhombic form), C222 1 with a ) 9.448 Å, b ) 24.299(1) Å, c ) 18.231(1) Å, V ) 4185.4(6) Å 3 , and Z ) 4; [Tc 2 Cl 4 (PMe 2 Ph) 4 ][PF 6 ] (1b, monoclinic form), P2 1 /n with a ) 12.799(4) Å, b ) 18.254(2) Å, c ) 17.945-(5) Å, ) 96.39(1)°, V ) 4166(2) Å 3 , and Z ) 4; [Tc 2 Cl 4 (PMe 2 Ph) 4 ][PF 6 ]‚ 1 / 2 THF (1‚ 1 / 2 THF), P2 1 /c with a ) 10.580(3) Å, b ) 33.327(3) Å, c ) 13.861(5) Å, ) 111.04(2)°, V ) 4562(1) Å 3 , and Z ) 4; Tc 2 Cl 5 (PMe 2 Ph) 3 (2), P2 1 /c with a ) 11.134(1) Å, b ) 14.406(1) Å, c ) 19.501(5) Å, ) 98.144(6)°, V ) 3096.3(7) Å 3 , and Z

A method is described for the hydrothermal preparation of the mixed metal sulfide chalcopyrite (CuFeSz) a t low temperatures (95-100 "C) and a t atmospheric pressure. The preparation produces optically tronsparent sols with a particle size range of 50-90 A. Optical absorption measurements show that the CuFeSz particles have an absorption maximum at 470 nm (~~7 0 = 7.1 X lo4 M-1 cm-1) and a band gap of 0.6 f 0.1 eV.

Silver nanoparticles with different sizes (7, 29, and 89 nm mean values) were synthesized using gallic acid in an aqueous chemical reduction method. The nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), and ultraviolet–visible (UV–Vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopies studies (TEM) we observed that silver nanoparticles have spherical (7 and 29 nm) and pseudospherical shape (89 nm) with a narrow size distribution. The sizes of the silver nanoparticles were controlled by varying some experimental conditions. It was found that the antibacterial activity of the nanoparticles varies when their size diminishes.

Temperature dependent molecular interaction of oxazine dyes, viz., brilliant cresyl blue (C.I. Basic dye), cresyl violet (C.I. Basic violet 3) and nile blue (C.I. Basic blue 12) are studied in aqueous media within a concentration range of 5.0 × 10 − 6 M to 8.0 × 10 − 4 M by UV-visible absorption spectroscopy. The effect of temperature on the geometrical structure of the dimer in solution along with the dimerization equilibria is explained in terms of electrostatic and hydrophobic interactions. Modified non-covalent interaction between two monomer molecules in a dimer as a function of temperature affects the extinction coefficient as well as the geometrical disposition of the dimers and this is well manifested in the exciton splitting of the dimer spectra. The angle θ between main oscillators of the two monomer molecules in a dimer increases by 1.94°for brilliant cresyl blue, whereas an increase of 4.32°and 1.73°were observed for cresyl violet and nile blue respectively due to the increase of temperature from 20°C to 60°C.

Beta-decay experiments are a primary source of information for nuclear-structure studies and at the same time complementary to in-beam investigations of nuclei far from stability. Although both types of experiment are mainly based on γ-ray spectroscopy, they face different experimental problems. The so-called Pandemonium effect is a critical problem in β-decay if we are to test theoretically calculated transition probabilities. In this contribution we will present a solution to this problem using total absorption spectroscopy methods. We will also present some examples of experiments carried out with the Total Absorption Spectrometer (TAS) at GSI an describe a new device LUCRECIA recently installed at CERN.

The densities of N, NH, and NH 2 radicals in a remote Ar-NH 3-SiH 4 plasma used for high-rate silicon nitride deposition were investigated for different gas mixtures and plasma settings using cavity ringdown absorption spectroscopy and threshold ionization mass spectrometry. For typical deposition conditions, the N, NH, and NH 2 radical densities are on the order of 10 12 cm −3 and the trends with NH 3 flow, SiH 4 flow, and plasma source current are reported. We present a feasible reaction pathway for the production and loss of the NH x radicals that is consistent with the experimental results. Furthermore, mass spectrometry revealed that the consumption of NH 3 was typically 40%, while it was over 80% for SiH 4. On the basis of the measured N densities we deduced the recombination and sticking coefficient for N radicals on a silicon nitride film. Using this sticking coefficient and reported surface reaction probabilities of NH and NH 2 radicals, we conclude that N and NH 2 radicals are mainly responsible for the N incorporation in the silicon nitride film, while Si atoms are most likely brought to the surface in the form of SiH x radicals.

A new approach to the formation of oriented monolayers and the assembling of built-up multilayer films is presented. The new method is fundamentally different from the Langmuir-Blodgett (LB) procedure, being based on the spontaneous occurrence of self-organization of amphiphiles at liquid-solid interfaces.

The oxidation mechanism of selected hydroxyquinoline carboxylic acids such as 8-hydroxyquinoline-7-carboxylic acid (1), the two positional isomers 2-methyl-8hydroxyquinoline-7-carboxylic acid (3), 2-methyl-5-hydroxyquinoline-6-carboxylic acid (4) as well as other hydroxyquinolines were studied in aprotic environment using cyclic voltammetry, controlled potential electrolysis, in-situ UV-Vis and IR spectroelectrochemistry and HPLC-MS/MS techniques. IR spectroelectrochemistry showed that oxidation unexpectedly proceeds together with protonation of the starting compound. We proved that the nitrogen atom in the heterocycle of hydroxyquinolines is protonated during the apparent 0.7 electron oxidation process. This was rationalized by the auto-deprotonation reaction by another two starting molecules of hydroxyquinoline, so that the overall oxidation mechanism involves two electrons and three starting molecules. Both, the electrochemical and spectroelectrochemical results showed that the oxidation mechanism is not influenced by the presence of carboxylic group in the chemical structure of hydroxyquinolines, as results from oxidation of 2,7-dimethyl-5hydroxyquinoline (6). In the presence of a strong proton acceptor such as pyridine, the oxidation ECEC process involves two electrons and two protons per one molecule of the hydroxyquinoline derivative. The electron transfer efficiency of hydroxyquinolines in biosystems may be related to protonation of biocompounds containing nitrogen bases. Molecular orbital calculations support the experimental findings.

The structure of glasses [with composition 0.855 (xNa*O-yNb205-zPzOs)-0.145 I&O,; Ln = La, Nd, Eu, and x t y + z = 1001 has been investigated by Raman scattering and optical spectroscopy using Nd3+ and Eu3+ as local structural probes. For the niobium-poor glasses (y < 12.5) octahedral Nb06 groups are inserted within modified metaphosphate chains. In contrast the network former of the niobium-rich glasses (y > 12.5) contains chains of NbOh octahedra sharing common comers. An intermediate situation seems to occur for y = 12.5 which preserves the Nasicon-type structure with a11 oxygen atoms common to Nb06 and PO4 groups. B 1988 Academic press, hc.

The Q y transition dipole moment vectors of all eight chlorophylls in the higher-plant antenna protein CP29 were calculated by an original method on the basis of linear dichroism and absorption spectroscopy. The contribution of individual chromophores was determined from difference spectra between wild type and mutant proteins in which a single chlorophyll has been removed by mutating pigmentbinding residues. Recombinant proteins were constructed by overexpressing the apoprotein in bacteria and refolding of the pigment-protein complex in vitro [Bassi, R., Croce, R., Cugini, D., and Sandonà, D. (1999) Proc. Natl. Acad. Sci. U.S.A. (in press)]. The spectroscopic data are interpreted on the basis of a protein structural model obtained via the homology with the major antenna complex LHCII [Kuhlbrandt, W., Wang, D. N., and Fujiyoshi, Y. (1994) Nature 367, 614-621].

A new family of pyrrole substituted metallophthalocyanine complexes, namely cobalt(II), iron(II), manganese(III), nickel(II) and zinc(II) tetrakis-4-(pyrrol-1-yl)phenoxy phthalocyanines (noted as M(TPhPyrPc), where M is the metallic cation) have been synthesized and fully characterized. In particular, the UV-visible spectra of the iron and nickel complexes showed extensive aggregation even at low concentrations. The cyclic voltammetry of the cobalt, iron and manganese complexes showed three to four redox couples assigned to metal and ring based processes. Spectroelectrochemistry of the manganese derivative confirmed that the synthesized complex is Mn III (TPhPyrPc -2 ) and that the reduction of Mn II (TPhPyrPc -2 ) to be centred on the ring and rather than on the metal, forming the Mn II (TPhPyrPc -4 ) species. Also, the electrochemical polymerization of these newly synthesized pyrrole-substituted phthalocyanines has been demonstrated in the case of the cobalt complex and the electrocatalytic activity of the obtained film has been tested towards the oxidation of L-cysteine.

Intravenous iron therapy is used to treat anemia associated with chronic kidney disease. The chemical structures of parenteral iron agents have not been characterized in detail, and correlations between structure, efficiency of iron delivery, and toxicity via catalysis of oxygen-derived free radical creation remain to be established. In this study, two formulations of parenteral iron have been characterized by absorption spectroscopy, X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis. The samples studied were Venofer Ò (Iron Sucrose Injection, USP) and Ferrlecit Ò (Sodium Ferric Gluconate in Sucrose Injection). The 250-800-nm absorption spectra and the XRD patterns showed that both formulations contain a mineral core composed of iron oxyhydroxide in the b-FeOOH mineral polymorph known as akaganeite. This was further confirmed for each formulation by imaging using TEM and AFM. The average core size for the nanoparticles, after dialysis to remove unbound or loosely bound carbohydrate, was approximately 3 ± 2 nm for the iron-sucrose, and approximately 2 ± 1 nm for the iron-gluconate. Each of the nanoparticles consists of a mineral core, surrounded by a layer of bound carbohydrate. The overall diameter of the average bead in the dialyzed preparations was approximately 7 ± 4 nm for the iron-sucrose, and 3 ± 1 nm for the iron-gluconate. Undialyzed preparations have particles with larger average sizes, depending on the extent of dilution of unbound and loosely bound carbohydrate. At a dilution corresponding to a final Fe concentration of 5 mg/mL, the average particle diameter in the iron-sucrose formulation was approximately 22 ± 9 nm, whereas that of the iron-gluconate formulation was approximately 12 ± 5 nm.

For the surface-optoelectronic study of sugar sensing, we synthesized and characterized dithiobis(4-butyrylamino-m-phenylboronic acid) (DTBA-PBA) as a recognition molecule. DTBA-PBA has a boronic acid group that has been known to form covalently bonded complexes with the 1,2-or 1,3-diol of sugars. A self-assembled monolayer (SAM) of DTBA-PBA was formed on a gold surface and characterized by atomic-force microscopy, Fourier transform infrared reflection absorption spectroscopy, and surface electrochemical measurements. An interaction study between monosaccharides and DTBA-PBA SAM was performed using surface plasmon resonance spectroscopy. The increase in molecular interactions between DTBA-PBA SAM and monosaccharides resulted in an optically induced electron excitation change on the Au surface through a refractive index change of the interfacial recognition layer. This correlation between electron excitation and molecular interaction was measurable at very low monosaccharide concentrations ð1:0 Â 10 À12 MÞ. DTBA-PBA SAM shows a selective fructose sensing among four kinds of monosaccharides, even in a low concentration range.

Semiconductor nanoclusters embedded in thin coatings of transparent and homogeneous silica glasses are suitable materials for the development of optical devices. The optical properties of such systems are strongly dependent on the elemental composition and the morphology of the coatings as well as on the nanocluster size distribution, their mutual interactions and the interactions with the host matrix. To achieve a good control over film composition and morphology the sol–gel route was used. The sol–gel synthesis of ZnO nanocrystals embedded in silica has been faced by the study of the gel-derived binary system ZnO–SiO2. The dip-coating procedure from alcoholic solutions containing tetraethoxysilane [Si(OC2H5)4, TEOS] and zinc acetate [Zn(CH3COO)2] was adopted. Zinc oxide nanograins have been generated in silica by hydrolysis of TEOS and the zinc salt and subsequent thermal annealing of the coatings. The system evolution under thermal treatment was studied by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, UV-Vis absorption spectroscopy and secondary-ion mass spectrometry.

The relationship between the molecular aggregation structures and the optical properties of fully aromatic and semialiphatic polyimide (PI) films were analyzed by synchrotron wide-angle X-ray diffraction (WAXD), infrared absorption, and UV/visible absorption spectroscopy at very high pressures up to 8 GPa. The PIs showed significant reduction in the interchain distances in the first stage of compression up to 1 GPa, which resulted in an appreciable decrease in the interchain free volume. In addition, reduction in the C-C bond lengths of aromatic rings by ca. 0.7% was confirmed by the pressure-induced high wavenumber shift of the infrared stretching vibration of the PIs. Furthermore, pressure-induced bathochromic shifts were observed in the locally excited (LE) absorption band of PIs, which are related to the enhanced van der Waals interaction caused by the reduced interchain distances. The intensity of the charge transfer (CT) absorption band of s-BPDA/PDA poly(p-phenylene biphenyltetracarboximide) PI was reduced up to 0.3 GPa, indicating that conformational changes affect the intramolecular CT interactions. In contrast, the CT absorptions of PMDA/ODA (poly(4,4 0 -oxidiphenylene pyromelliticimide) and PMDA/DCHM (poly(4,4 0 -diaminocyclohexylmethane pyromelliticimide) PIs were enhanced by increasing the pressure, which was caused by an enhancement of intermolecular CT interactions. The significant variations observed in the LE and intermolecular CT bands below 1 GPa accord with the significant decrease in the interchain distance, as indicated by synchrotron WAXD.