Search results for "fluorescence"
showing 10 items of 2463 documents
Dynamic chemical devices: photoinduced electron transfer and its ion-triggered switching in nanomechanical butterfly-type bis(porphyrin)terpyridines.
2005
A series of butterfly-type molecular constructs has been prepared in good yield by using a double Stille coupling synthetic protocol. They are composed of a terpyridine (terpy) scaffold and two wings composed of appended porphyrins that are capable of switching from an extended W geometry to a compact U geometry upon cation coordination of the terpy unit. The porphyrin moieties exist in the constructs either as free bases or they can be sequentially metallated, thus giving rise to wings of different "colours". Stationary and time-resolved emission studies of the HZn, ZnAu and Zn2Au constructs show that the electronic properties are strongly dependent on the geometry. In the extended W confo…
DNA binding, nuclease activity, DNA photocleavage and cytotoxic properties of Cu(II) complexes of N-substituted sulfonamides.
2013
Abstract Ternary copper(II) complexes [Cu(NST)2(phen)] (1) and [Cu(NST)2(NH3)2]·H2O (2) [HNST = N-(4,5-dimethylthiazol-2-yl)naphthalene-1-sulfonamide] were prepared and characterized by physico-chemical techniques. Both 1 and 2 were structurally characterized by X-ray crystallography. The crystal structures show the presence of a distorted square planar CuN4 geometry in which the deprotonated sulfonamide, acting as monodentate ligand, binds to the metal ion through the thiazole N atom. Both complexes present intermolecular π–π stacking interactions between phenanthroline rings (compound 1) and between naphthalene rings (compound 2). The interaction of the complexes with CT DNA was studied b…
Fluorimetric determination of 1-naphthol and mixtures of carbaryl and 1-naphthol in micellar media
1990
The interaction of 1-naphthol with different types of anionic, cationic and non-ionic surfactants has been studied spectrofluorimetrically in order to obtain a sensitivity enhancement in the determination of this compound. At neutral pH, cetyl trimethyl ammonium bromide (CTAB) provides a 2-fold sensitivity enhancement of 1-naphthol and exhibits a weak interaction with carbaryl. In strong alkaline medium carbaryl is hydrolyzed to 1-naphthol and in the presence of CTAB micells, a 5-fold sensitivity enhancement and a limit of detection of 0.2 μg·ml−1 with a 101±3% percentage of recovery is obtained. These facts permit the development of an accurate method for the fluorimetric analysis of 1-nap…
Sequential-injection determination of traces of disodium phenyl dibenzimidazole tetrasulphonate in urine from users of sunscreens by on-line solid-ph…
2005
Abstract A sensitive and selective method to determine disodium phenyl dibenzimidazole tetrasulphonate (PDT) in the urine of sunscreen users, which is suitable for studies on body accumulation/excretion is proposed. On-line solid-phase extraction allows the analyte to be retained and subsequentely eluted, using a strong anion exchange (SAX) microcolumn. Standard addition calibration was carried out with only one standard. The wavelengths of excitation and emission were 330 and 454 nm, respectively. The method allows PDT to be determined in both, spiked and unspiked human urine samples, without any pre-treatment. Results obtained for spiked urine samples (40–200 ng ml −1 ) showed the accurac…
Automated high-performance liquid chromatographic determination of amphetamine in biological fluids using column-switching and on-column derivatizati…
1999
A rapid and simple liquid-chromatographic method has been developed for on-line quantification of amphetamine in biological fluids. Untreated samples (20 μL) are injected directly into the chromatographic system and purified on a 20 mm×2.1 mm i.d. pre-column packed with 30 μm Hypersil C18 stationary phase. After clean-up the analyte is transferred to the analytical column (125 mm×4 mm i.d., 5 μm LiChrospher 100 RP18) for derivatization and separation using a mixture of acetonitrile and the derivatization reagent (o-phthaldialdehyde andN-acetyl-L-cysteine) as the mobile phase. The experimental conditions for on-line derivatization and resolution of the amphetamine have been optimized, and th…
Anthrylmethylamine functionalised mesoporous silica-based materials as hybrid fluorescent chemosensors for ATP
2005
A number of functionalised mesoporous solids containing anchored anthrylmethylamine groups have been prepared using different co-hydrolysis or grafting synthetic routes. The solids have been characterised using standard solid-state techniques. Solids with a low loading of the anthrylmethylamine probe show typical well defined and structured emission bands centred at ca. 415 nm. Addition of ATP to suspensions of these solids at pH 2.8 resulted in a quenching of the anthracene emission. These solids showed a cooperative effect that resulted in quite a remarkable improvement in ATP response with respect to the free anthrylmethylamine probe in solution. Certain prepared solids showed a remarkab…
Improvement of the atomic fluorescence determination of mercury by using multicommutation
2002
Atomic fluorescence spectrometry (AFS) determination of Hg has been improved by exploiting the possibilities of the multicommutation approach in order to outline a fully mechanised system which supplies the same sensitivity as the use of continuous measurements, reducing drastically the reagents consumed and waste generation. The use of multicommutation with a simultaneous reduction of the liquid–gas separator volume and the insertion point modification of argon transport gas provides a sensitivity of the AFS measurements of 300 mV ng−1 ml (using a full scale of 1000 mV), a limit of detection (3 s) of 1.3 ng l−1 and relative standard deviation values below 0.1% for 10 independent measuremen…
The natural compound chrysosplenol-D is a novel, ultrasensitive optical sensor for detection of Cu(II)
2020
Abstract Herein, we introduce a novel, ultrasensitive optical sensor for determination of Cu(II) ions over the concentration range of 0 to 1 μM Cu(II). The optical sensor is based on the natural molecule chrysosplenol-D (Chp-D) extracted from the flowering plant Chiliadenus montanus (Vahl.) Brullo. Free Chp-D emits fluorescence at 566 nm when excited at 292 nm. Chp-D chelates Cu(II) ions to form a 1:1 (metal:ligand) complex, which quenches the fluorescence emission peak of the free probe at 566 nm. “Turn-off” luminescence could be easily determined and provided distinct proof of the chelation of Cu(II) ions by Chp-D. This novel optical sensor offers a considerable fluorescence mechanism (ch…
Determination of Concentration Profiles of Methyl Mercury Compounds in Surface Waters of Polar and other Remote Oceans by GC-AFD
1998
Abstract The concentration of monomethyl mercury (MeHg+) and dimethyl mercury (Me2Hg) was determined in surface sea-water samples of the Antarctic and Arctic Ocean as well as of other remote areas (South Atlantic and South Pacific) during expeditions of the German research vessel “Polarstern”. A purge and trap/gas chromatographic system, equipped with an atomic fluorescence detector (AFD), was used. For the analysis of MeHg+ conversion into the volatile methylethyl mercury by reaction with tetraethyloborate prior to the purging process was carried out. The detection limit for both methylated mercury compounds was 5 pg Hg/L, which allowed their determination in most ocean water samples even …
Preparation of Hg2+ selective fluorescent chemosensors based on surface modified core–shell aluminosilicate nanoparticles
2010
A synthetic procedure for the preparation of functional structured inorganic–organic hybrid materials consisting of boehmite-silica core–shell nanoparticles and anthracene-containing amines covalently attached to the nanoparticles surface is reported. The system functionalised with the monoamine chain shows a very high sensing performance for Hg2+ detection in pure water reaching a detection limit of 0.2 ppb. Two additional advantages of these systems are their stability over a wide pH window and the feasibility to be recovered by a simple procedure.