Search results for "Fluorescence spectroscopy"
showing 10 items of 188 documents
Nitroanilines as Quenchers of Pyrene Fluorescence
2012
The quenching of pyrene and 1‐methylpyrene fluorescence by nitroanilines (NAs), such as 2‐, 3‐, and 4‐nitroaniline (2‐NA, 3‐NA, and 4‐NA, respectively), 4‐methyl‐3‐nitroaniline (4‐M‐3‐NA), 2‐methyl‐4‐nitroaniline (2‐M‐4‐NA), and 4‐methyl‐3,5‐dinitroaniline (4‐M‐3,5‐DNA), are studied in toluene and 1,4‐dioxane. Steady‐state fluorescence data show the higher efficiency of the 4‐NAs as quenchers and fit with a sphere‐of‐action model. This suggests a 4‐NA tendency of being in close proximity to the fluorophore, which could be connected with their high polarity/hyperpolarizability. In addition, emission and excitation spectra evidence the formation of emissive pyrene—NA ground‐state complexes in…
Inhibitoren der Korrosion (11). Nachweis der auf Eisengrenzflächen gebildeten Sekundärinhibitoren durch UV-Absorptions- und Fluoreszenzspektroskopie
1972
Aus Triphenylbenzylphosphoniumchlorid bildet sich in saurer Losung auf der Eisenoberflache eine Schicht, die aufgrund der UV-Reflexionsspektroskopie mit Triphenylphosphin identisch sein durfte. Auch das Mono- und Bis-Phosphoniumsalz wird an der Eisengrenzflache reduktiv abgebaut; die dabei entstehenden Anthracenderivate werden auf dieselbe Weise identifiziert. Es handelt sich um Methylanthracen. Die zur weiteren Aufgliederung der Reaktionsprodukte vorgenommene dunnschicht-chromatografische Auftrennung (Untersuchung des Extrakts in Cyclohexanol und Methanol) ergibt kein sich deutlich unterscheidenden Fluoreszenzspektren. Identification, by UV absorption and fluorescence spectroscopy, of the …
Interaction between nitroxyl radicals and CdTe quantum dots: Determination of fluorescence-quenching mechanisms in aqueous solution
2019
Abstract The present work characterizes the optical properties of CdTe quantum dots (CdTe QDs) after interaction with nitroxyl radicals based on steady-state and time-resolved fluorescence spectroscopy studies. QDs of different sizes were exposed to 2 different nitroxyl radicals, i.e., TEMPO and 4-amino-TEMPO radicals. A clear dependence of dynamic and static Stern-Volmer constants values, KD and KS, respectively, was observed as a function of the size of QDs used, with a change from a mostly static mechanism (for smaller QD sizes) to a dynamic mechanism predominating as the nanoparticles increase in size. All observed effects are dependent on both the concentration of the radical and the s…
FIA-fluorimetric determination of adrenaline in pharmaceutical formulations by oxidation with molecular oxygen
1998
The fluorimetric determination of adrenaline is carried out in a continuous-flow assembly and by means of the molecular dissolved oxygen. The sample solution merges with an NaOH stream, then the resulting mixture is heated at 73 °C and led to the flow-cell of the fluorimeter. The flow-assembly is very simple and the procedure is quick (107 samples h−1) reproducible (R.S.D. 0.6%), selective and suitable to be applied to determination of adrenaline in formulations. Calibrations graph are linear over the ranges 0.05–15 and 20–40 mgl−1.
Interaction of quinine with negatively charged lipid vesicles studied by fluorescence spectroscopy Influence of the pH
1997
Abstract The interaction of quinine with dimyristoylphosphatidic acid (DMPA) and dimyristoylphosphatidyl glycerol (DMPG) small unilamellar vesicles in the gel phase was studied by steady-state fluorescence spectroscopy at pHs 7, 6, 5 and 4 and 20°C. In aqueous solution, with excitation at 335 nm, the emission fluorescence spectrum of quinine varied with pH reflecting the occurrence of different charged species of the drug. In all cases, the emission maximum centered at 383 or 443 nm shifted to lower wavelength in the presence of vesicles. This indicates that the membrane-bound state quinine is in an environment of low polarity. Drug monocationic species were deeply buried in DMPG relative t…
Solubilization of an Organic Solute in Aqueous Solutions of Unimeric Block Copolymers and Their Mixtures with Monomeric Surfactant: Volume, Surface T…
2008
The ability of aqueous systems, formed by unimeric copolymers and their mixtures with a monomeric surfactant, in solubilizing large quantities of 1-nitropropane (PrNO2) was explored. The copolymers are F68 and L64, which differ for the hydrophilicity, and the surfactant is sodium dodecanoate. For a better understanding of the mechanism of solubilization, thermodynamic (volume and differential scanning calorimetry), spectroscopy (steady-state fluorescence), viscosity, and interfacial investigations were carried out. PrNO2 causes the micellization of the unimeric copolymer, and the required amount of PrNO2 depends on the composition, the copolymer nature, and the temperature. Large quantities…
[2]Catenanes and inclusion complexes derived from self-assembled rectangular PdII and PtII metallocycles
2012
New inclusion complexes and [2]catenanes were self-assembled from a fluorescent diazapyrenium based ligand, a PdII or PtII complex, and cyclic or acyclic electron rich aromatic guests in aqueous and organic media. The molecular rectangles display a π-deficient cavity suitable to incorporate π-donor aromatic systems. The inclusion complexes between the metallocycles and phenylenic (2a,b) and naphthalenic (3a,b–5a,b) derivatives were studied by NMR, UV-vis and fluorescence spectroscopy. The crystal structure of (3b) ⊂ 1a·6PF(6) confirmed the insertion of the guest into the cavity of the metallocycle. Following the same self-assembly strategy, the use of polyethers 6,7 as π-donors resulted in …
The Protohistoric sword from Le Gué-de-Velluire (Vendée, France): a pasticcio's history unveiled by archaeometrical research
2020
International audience; The Gué-de-Velluire sword (Vendée, France) is part of the Rochebrune collection collected during the 19 th and the 20 th centuries and now preserved in the Dobrée Museum in Nantes (Loire-Atlantique, France). The unusual shape of its hilt, its uncorroded rivets and the rather uncommon combination of a bronze grip with an iron blade made this sword an exceptional object. It has been depicted in a large number of papers since the 20 th century, but the question of its authenticity has hardly ever been tackled. New analyses performed with the support of the Dobrée Museum, the Arc'Antique laboratory and Ghent University delivered new data enabling us to discuss this delic…
Pyrene derived functionalized low molecular weight organic gelators and gels
2008
Pyrene derived binary functionalized low molecular weight organic gelators (FLMOGs) and gels thereof in selected organic solvents were synthesized and characterized. The functionality refers to a functional group that does not take part in formation of the supramolecular gel network, but remains free and available for other purposes, such as to bind nanoparticles or other molecules into the gel structure. Functional groups were observed to disturb gel formation strongly, if they interact with each other within the same supramolecule due to the formation of competitive structures. Preventing such interactions restored the original gel properties. A gel with weaker supramolecular bonding than…
Development of Polyamine‐Substituted Triphenylamine Ligands with High Affinity and Selectivity for G‐Quadruplex DNA
2019
Currently, significant efforts are devoted to designing small molecules able to bind selectively to guanine quadruplexes (G4s). These noncanonical DNA structures are implicated in various important biological processes and have been identified as potential targets for drug development. Previously, a series of triphenylamine (TPA)-based compounds, including macrocyclic polyamines, that displayed high affinity towards G4 DNA were reported. Following this initial work, herein a series of second-generation compounds, in which the central TPA has been functionalised with flexible and adaptive linear polyamines, are presented with the aim of maximising the selectivity towards G4 DNA. The acid-bas…