Search results for "Fluorescence"
showing 10 items of 2463 documents
Fluorescence Probe and Scanning Force Microscopic Studies of Water Soluble Comb-Shaped Copolymers Consisting of a Hydrophobic Poly(p-alkylstyrene) Ma…
2002
Fluorescence Probe and Scanning Force Microscopic Studies of Water Soluble Comb-Shaped Copolymers Consisting of a Hydrophobic Poly( p -alkylstyrene) Main Chainand Hydrophilic Poly(ethylene oxide) Grafted Chains
Fluorescent Type II Materials from Naphthylmethyl Polyamine Precursors
2004
Speciation studies in aqueous solution on the interaction of Cu2+ and Zn2+ with a series of polyaminic ligands N-naphthalen-1-ylmethyl-N′-{2-[(naphthalen-1-ylmethyl)-amino]-ethyl}-ethane-1,2-diamine (Ll), N-naphthalen-1-ylmethyl-N′-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethyl)-ethane-1,2-diamine (L2) and N-naphthalen-1-ylmethyl-N′-[2-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethylamino)-ethyl]-ethane-1,2-diamine (L3) containing two naphthylmethyl groups at their termini and N 1-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethyl)-ethane-1,2-diamine (L4) containing just one naphthylmethyl group have been carried out at 298.1 K in 0.15 mol dm−3 NaCl. In the case of the …
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...
Ground and excited state properties of polyamine chains bearing two terminal naphthalene units
2002
A series of compounds bearing two naphthalene units linked through methylene groups to both ends of different open-chain polyamines has been investigated. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state and length of the polyamine chains and implies the existence of a bending movement in the excited state allowing the two naphthalene units to approach and interact. This interpretation was clearly proven by time-resolved fluorescence with the appearance of double exponential decays with a rise time observed at the excimer emission wavelength. For comparison purposes one bis-chromophoric compound containing a rigid cha…
Evidence for reverse pathways and equilibrium in singlet energy transfers between an artificial special pair and an antenna
2013
A dyad, 1, built on an artificial special pair (bis(meso-nonyl)zinc(II)porphyrin), [Zn2], a spacer (biphenylene), a bridge (1,4-benzene), and an antenna (di-meso-(3,5-di(t-butyl)phenyl)porphyrin free base), FB, is prepared by Suzuki coupling and is analyzed by absorption and steady state, and time-resolved emission spectroscopy at 298 and 77 K. Using bases from the Förster theory, evidence for two pathways for S 1 energy transfer, FB* → [Zn2], and [Zn2]* → FB, along with their respective rates, k ET ( S 1)1 and k ET ( S 1)-1, are extracted from the comparison of the fluorescence decays monitored at the emission maximum. At 77 K, the unquenched (1.79 ([Zn2]) and 10.6 ns (FB)) and quenched c…
Ultrafast energy transfer in dansylated POPAM–eosin complexes
2006
Abstract Excitation energy transfer (EET) in dendritic host–guest complexes has been studied. Three generations G2, G3 and G4 of dansyl substituted poly(propyleneamine) dendrimers (POPAM) were complexed with a fluorescent dye eosin in chloroform solution. Arrival of excitation from dansyls to eosin was monitored by femtosecond transient absorption spectroscopy. EET rates from the dansyls to eosin(s) are characterised by two time constants 1 ps and 6 ps independent of dendrimer generation. Relaxation processes in eosin were clearly faster when complexed with dendrimer than in solution. As several eosins are bound to G3 and G4 dendrimers, besides host–guest interaction, also eosin–eosin inter…
Anion Receptors Based on a Quinoline Backbone
2007
2-Amido-8-urea substituted quinoline derivatives are potent receptors for the binding of halide or benzoate anions in chloroform. The selectivity and affinity of the receptors for fluoride can be tuned by variation of the substituents at the receptor side chains. Computational considerations show that the cleft of the receptors provides space for effective binding of F–, but not bigger anions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
FIA-Fluorimetric assembly for the determination of noradrenaline hydrochloride by a solid-phase reactor with immobilized hexacyanoferrate(III)
1997
An FIA assembly provided with immobilized hexacyanoferrate(III) is proposed for the fluorimetric determination of noradrenaline hydrochloride. The oxidative reagent is immobilized by means of a strong anion-exchange resin. The FIA manifold is very simple and the calibration graph is linear over the range 0.5–75mgl−1 noradrenaline hydrochloride with an r.s.d of 0.88% (17 replicates) and a sample throughput of 84h−1. Foreign compounds such as NaCl, sucrose, lactose and sodium sulfate caused no significant errors. The procedure is applied to the determination of noradrenaline in a medicinal formulation.
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…
Steady-state fluorescence emission studies on polyazacyclophane macrocyclic receptors and on their adducts with hexacyanocobaltate(III)
1995
The steady-state fluorescence emission spectra of the azacyclophanes 2,5,8,11-tetraaza[12] paracyclophane (L1), 2,6,9,13-tetraaza[14]paracyclophane (L2), 14,15,17,18-tetramethyl-2,5,8,11-tetraaza[12]paracyclophane (L3) and 16,17,19,20-tetramethyl-2,6,9,13-tetraaza[14]paracyclophane (L4) as a function of pH have been measured. The fully protonated species of each cyclophane gives the highest fluorescence-emission quantum yield. The shapes of the titration curves have been explained by the existence of an electron-transfer quenching effect from a non-protonated amine to the benzene chromophore. This effect is greater for macrocycles in which the first deprotonated amine group is closer to the…