Search results for "Dye"
showing 10 items of 577 documents
Supramolecular Chemical Sensors Based on Pyrene Monomer-Excimer Dual Luminescence
2010
The past ten years have seen a spectacular development of chemical sensors based on the monomer-excimer dual luminescence of aromatic systems, such as pyrene. Either in the form of integrated or multicomponent molecular devices these chemosensors have been attracting a high interest above all because of their unique ratiometric properties. This review will focus on the latter systems, which can be classified into two classes: Firstly, the assembly of receptor-effector conjugates is triggerred by the analyte of interest. As a result, the sensor shows monomer to excimer fluorescence switching upon substrate binding. Secondly, the supramolecular assembly that constitutes the sensor is perturbe…
More about sampling and estimation of mercaptans in air samples
2013
[EN] Several strategies have been developed for sampling and determination of volatile thiols. The selectivity and sensitivity of the proposed methodologies are achieved by using a specific derivatizing reagent. The different procedures assayed are based on air sampling followed by derivatization of the analytes with OPA and isoleucine in alkaline solution. The derivatization products are separated and determined by liquid chromatography and fluorescence detection. To start, the derivatization conditions and stability of the derivates have been studied in order to establish the storage conditions. In general, the strategies studied consisted on trapping and detivatization the thiol compound…
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…
Highly Selective Detection of Nerve‐Agent Simulants with BODIPY Dyes
2014
Two chromo-fluorogenic probes, each based on the boron dipyrromethene core, have been developed for the detection of nerve-agent mimics. These chemosensors display both a color change and a significant enhancement of fluorescence in the presence of diethylcyanophosphonate (DCNP) and diisopropylfluorophosphate (DFP). No interference from other organophosphorus compounds or acids has been observed. Two portable chemosensor kits have been developed and tested to demonstrate its practical application in real-time monitoring.
Theoretical study on the influence of electric field direction on the photovoltaic performance of aryl amine organic dyes for dye-sensitized solar ce…
2019
It is very important to reveal the influence of different electric field directions on dye sensitizers. Thus, in this study, we investigated the electronic structures and optical properties of six designed aryl amine organic dye models under different electric fields using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Moreover, the electronic structures and optical properties of these studied dyes with different electric field in tetrahydrofuran (THF) were also calculated. The key parameters of the short-circuit current density (Jsc), including light harvesting efficiency (LHE) and intra-molecular charge transfer (ICT), are discussed in detail. With …
[3.3]Ferrocenophanes with guanidine bridging units as multisignalling receptor molecules for selective recognition of anions, cations, and amino acid…
2007
The synthesis, electrochemical, and optical properties of a new [3.3]ferrocenophane framework in which two ferrocene subunits, with similar electronic environments, are linked through two substituted guanidine moieties, are reported. The receptors 4-7 have been prepared in good yields by the reaction of bis(carbodiimide) 3 with primary amines. This architecture is exceptionally "tunable" because a variety of "legs" may be appended to the basic [3.3]ferrocenophane scaffold to give a wide range of signaling units. These receptors show remarkable ion-sensing properties, due to the presence of a redox active unit (ferrocene), and an amphoteric binding site (guanidine). In this nitrogen-rich str…
Superoxide Flux in Endothelial Cells via the Chloride Channel-3 Mediates Intracellular Signaling
2007
Reactive oxygen species (ROS) have been implicated in both cell signaling and pathology. A major source of ROS in endothelial cells is NADPH oxidase, which generates superoxide (O2.−) on the extracellular side of the plasma membrane but can result in intracellular signaling. To study possible transmembrane flux of O2.−, pulmonary microvascular endothelial cells were preloaded with the O2.−-sensitive fluorophore hydroethidine (HE). Application of an extracellular bolus of O2.−resulted in rapid and concentration-dependent transient HE oxidation that was followed by a progressive and nonreversible increase in nuclear HE fluorescence. These fluorescence changes were inhibited by superoxide dism…
DNA fluorescence induced by polymethine cation pyrvinium binding
1991
Pyrvinium is a polymethine cation which shows interesting fluorescence emission and DNA binding properties. In diluted aqueous solution, pyrvinium pamoate induced a bright yellow fluorescence in kinetoplast DNA from Trypanosoma cruzi epimastigotes as well as in chicken erythrocyte nuclei under a wide range of excitations. No fading was observed after mounting in suitable media. Spectroscopic studies on pyrvinium solutions revealed bathochromic and hypochromic shifts in the absorption spectrum of its complex with DNA. A striking enhancement of pyrvinium fluorescence was found in solvents of high viscosity or after binding to DNA. Experimental results and the chemical structure of pyrvinium a…
On Pathways for Small Molecules Into and Out of Human Hair Fibers
1996
This paper represents an experimental approach of histology of the human hair fiber in dyeing and diffusion phenomena and its contribution to the interpretation of hair analysis results for drug abuse. Rhodamine B was applied to human hair fibers from either aqueous solution or methanol/ethanol solvent. The experiments were performed on natural hair of different ethnic groups as well as on extensively bleached hair strands. The microscopical study of the pathway of diffusion of rhodamine B into the hair fibers indicated that the reagent had entered the unmodified fibers at the scale edges between the cuticle cells. At the beginning of the diffusion process intercellular diffusion was the pr…
Design, Synthesis and Evaluation of Enzyme-Responsive Fluorogenic Probes Based on Pyridine-Flanked Diketopyrrolopyrrole Dyes
2020
The ever-growing demand for fluorogenic dyes usable in the rapid construction of analyte-responsive fluorescent probes, has recently contributed to a revival of interest in the chemistry of diketopyrrolopyrrole (DPP) pigments. In this context, we have explored the potential of symmetrical and unsymmetrical DPP derivatives bearing two or one 4-pyridyl substituents acting as optically tunable group(s). The unique fluorogenic behavior of these molecules, closely linked to N-substitution/charge state of their pyridine unit (i.e., neutral pyridine or cationic pyridinium), has been used to design DPP-based fluorescent probes for detection of hypoxia-related redox enzymes and penicillin G acylase …