Search results for " Spectra"
showing 10 items of 709 documents
Binding and Fluorescent Sensing of Dicarboxylates by a Bis(calix[4]pyrrole)-Substituted BODIPY Dye
2013
A bis(calix[4]pyrrole)-substituted BODIPY ditopic receptor 1 has been synthesised and characterised. The binding and sensing properties of 1 towards several aliphatic and aromatic dicarboxylates have been evaluated by using UV/Vis fluorescence and 1H NMR spectroscopy. The receptor strongly binds linear α,ω-dicarboxylates of appropriate lengths (C9 and C10) by acting as a cleft. For all dicarboxylates, the binding event is detected by a bathochromic shift in the UV/Vis spectra of the receptor and by strong quenching of its fluorescence.
Effect of S1 Torsional Dynamics on the Time-Resolved Fluorescence Spectra of 9,9‘-Bianthryl in Solution
1997
Time-resolved fluorescence spectra of 9,9‘-bianthryl (BA) were measured in methylcyclohexane (MCH) and a Decalin−isooctane (D−ISOO) mixture at several temperatures between 127 and 200 K. A suitable...
Konvergenz von Absorption und Fluoreszenz bei gekreuzt konjugierten Oligomeren aus Chalkon-Bausteinen
1999
The absorption and fluorescence spectra of two series of chalcone oligomers (1a–d) and (2a–d) are reported. Due to small or vanishing orbital coefficients (HMO calculation) within the cross-conjugated systems, the bathochromic shifts caused by the extension of the chains are modest. The effective conjugation lengths amount to 6 and 14 chalcone building blocks in the absorptions of the series 1 and 2. The convergence of the fluorescence bands is already reached in 1d and 2d with 4 and 8 enone units, respectively. Besides the uniform or alternate arrangement of the chalcone building blocks, the positions of the propoxy substituents show a considerable influence on the electronic transitions p…
The Nonanuclear [Mo(IV) {(CN)Fe(III)(3-ethoxy-saldptn)}8]Cl4 Complex Compound Exhibits Multiple Spin Transitions Observed by Mössbauer Spectroscopy
2004
The pentadentate ligand 3-EO-5LH2 = 3-ethoxy-saldptn = N,N′-bis(3-ethoxy-1-hydroxy-2-benzyliden)-1,7-diamino-4-azaheptane has been prepared by a Schiff base condensation between 1,7-diamino-4-azaheptane and the corresponding 3-ethoxy-salicyaldehyde. 3-EO-5LH2 is a sterical extention to 5LH2. Its complexation with Fe(III) gave the high-spin (S = 5/2) complex of [Fe(III)(3-EO-5L)Cl]. This precursor was combined with [Mo(CN)8]4− and a blue nonanuclear cluster [Mo(IV){(CN)Fe(III)(3-EO-5L)}8]Cl4 resulted. This starshaped nonanuclear compound is a high-spin system at room temperature. On cooling to 10 K some of the eight iron(III) centers switched to the low-spin state as proven by Mossbauer spec…
Terrylene in p-terphenyl: single-molecule experiments at room temperature
1999
Abstract This paper reports on fluorescence microscopy and spectroscopy of single terrylene molecules embedded in p -terphenyl at room temperature. The basic photophysical parameters of this crystalline host/guest system such as photostability, single-molecule emission rates and the properties of dispersed fluorescence spectra are reported. The stability of the single-molecule signals allowed the direct observation of singlet–triplet quantum jumps at room temperature, by means of which the underlying intersystem crossing rates can be investigated. The results of earlier investigations at liquid-helium temperatures are reviewed briefly where appropriate. The properties of terrylene in p -ter…
Determination of fatty acids and lipid classes in salmon oil by near infrared spectroscopy
2017
International audience; Near-infrared (NIR) spectroscopy was evaluated as a rapid method for the determination of oleic, palmitic, linoleic and linolenic acids as well as omega-3, omega-6, and to predict polyunsaturated, monounsaturated and saturated fatty acids, together with triacylglycerides, diglycerides, free fatty acids and ergosterol in salmon oil. To do it, Partial Least Squares (PLS) regression models were applied to correlate NIR spectra with aforementioned fatty acids and lipid classes. Results obtained were validated in front of reference procedures based on high performance thin layer and gas chromatography. PLS-NIR has a good predictive capability with relative root mean squar…
Copper Octacarboxyphthalocyanine Aggregation in Buffered Solutions
2008
Results of spectral UV-Vis absorption investigations on association of copper octa-carboxyphthalocyanine, CuPcOC, are reported. Influence of pH on association is discussed. In pH < 5.5 only ag gre gates are present. Monomer appears above pH = 5.5 and at pH Greater-than or equal to 6.2 only monomeric Pc forms exist. CuPcOC exhibits higher tendency to wards association in phosphate buffer solutions than in redistilled water. In pH 5.9–6.0 monomers, dimers and trimers coexist in equilibrium in 1.0×10–6 – 1.2×10–5 mol/dm3 concentration range at 25°C. The average assembling number n = 3 was determined for pH 5.6, 5.9 and 6.0 solutions. The spectrum of aggregate was calculated with two maxima at …
Dimerization of Copper Octacarboxyphthalocyanine in Aqueous Solutions
2005
Spectral absorption UV-Vis investigations on association of copper(II) octacarboxyphthalocyanine in aqueous solutions are reported. In 5.0x10-7-5.0x10-5 mol/dm3 concentration range monomers and dimers are mainly present. The calculated dimerization constant 106dm3/mol at 25°C and the hypsochromic spectral shift for the dimer 1164 cm-1 (688 nm_ 637 nm) indicate a stack-like association of molecules and suggestpi-pi interactions between Pc macrocycles in dimer and higher aggregates, in contrast to hydrogen bonding between carboxylic groups of adjacent Pc molecules.
Measurement of the cosmic-ray energy spectrum above 2.5×1018 eV using the Pierre Auger Observatory
2020
We report a measurement of the energy spectrum of cosmic rays for energies above 2.5×10^18 eV based on 215,030 events recorded with zenith angles below 60°. A key feature of the work is that the estimates of the energies are independent of assumptions about the unknown hadronic physics or of the primary mass composition. The measurement is the most precise made hitherto with the accumulated exposure being so large that the measurements of the flux are dominated by systematic uncertainties except at energies above 5×10^19 eV. The principal conclusions are(1) The flattening of the spectrum near 5×10^18 eV, the so-called "ankle,"is confirmed.(2) The steepening of the spectrum at around 5×10^19…