1,720,981 research outputs found
Residual and exploitable fluorescence in micellar self-assembled ON-OFF sensors for copper(II).
No full textset of new ligands, L2H(2)-L5H(2), containing the 1,4,8,11-tetraaza-5,7-dione framework has been prepared, The ligands feature lipophilic substituents either on the carbon atom in the 6 position or on the amino groups, or on both. The solution behaviour of the ligands when included in TritonX-100 micelles has been investigated by means of potentiometric titrations and protonation and complexation constants for the Cu2+ cation have been determined in micellar medium. Micellar assemblies containing the ligands and pyrene have been prepared, and coupled pH-metric and fluorimetric titrations allowed the determination of the response of the systems as ON-OFF fluorescent sensors for Cu2+. A correlation between the effective lipophilicity of the ligand and the residual fluorescence (i.e. the fluorescence of the OFF state) was observed, and with the more lipophilic ligand, L3H(2), we obtained a residual fluorescence as low as 8%, with a significant improvement with respect to other published systems. On the other hand, introduction of functionalities on the amino groups of 1,4,8,11-tetraaza-5,7-dione brings the drawback of a small but significant decrease of the exploitable fluorescence, i.e. the fluorescence of the system in the absence of added Cu2+, at the pH value suitable for full metal complexatio
Micelles as nanosized containers for the self-assembly of multicomponent fluorescent sensors
No full textMicelles can be used as containers to confine different lipophilic molecules in the same nanometric volume. When two or more molecules are contained in the same micelle their local concentration is dramatically increased, they are much less solvated than in bulk water and their mobility is still allowed as if they were included in an organic solvent nanodroplet. As a consequence intramicellar dynamic interactions are strongly promoted and new overall functions may be expressed by the combination of the properties of each molecular component, obtaining a nanosized supramolecular device. In this paper we will review the micellar systems in which the promotion of metal-ligand coordination between lipophilic fluorescent ligands and lipophilic complexes, and the comicellization of lipophilic fluorophores with lipophilic ligands and bases allow the micellar self-assembling of supramolecular fluorescent sensors for cations, anions, pH-windows, and for some chemical-physical properties of molecule
Residual and exploitable fluorescence in micellar self-assembled ON-OFF sensors for Cu(II)
No full textSmoothly shifting fluorescent windows: a tunable "off-on-off" micellar sensor for pH
Full text linkThe position of the window in an "off-on-off" fluorescent pH sensor may be shifted at will along a pH axis by changing the overall charge of the micellar container. This is obtained by using non-ionic Triton X-100 as the surfactant, and by increasing the molar fraction of the anionic sodium dodecyl sulfate (chi(SDS)) as co-surfactant, with pyrene as the fluorophore and a lipophilic tertiary amine and a lipophilic pyridine as pH-switchable quenchers. As the negative micellar charge increases by increasing cSDS, the observed pKa of the protonated bases move to higher pH values, followed by the dumb-bell shaped "off-on-off" fluorescence intensity vs. pH profil
Self-Assembled monolayers of thiols on grafted silver-nanoparticles: controlling surface coverage at the nanoscale
No full textA Micellar Multitasking Device: Sensing pH Windows and Gauging the Lipophilicity of Drugs with Fluorescent Signals
Full text linkA multitasking fluorescent device can be obtained by forming micelles of Triton X-100, containing a lipophilic macrocyclic Cu2+ complex and the coordinating fluorophore Coumarin 343 (C343), which features a COOH moiety. At low pH the two micellised components do not interact, and the fluorescence of Courmarin 343 (C343) is intense. At intermediate pH, C343 is deprotonated and coordinates to the Cu2+ centre in its apical position, with fluorescence quenching. At higher pH the deprotonated C343 is displaced from Cu2+ by the formation of an OH- complex, and the fluorescence is revived. This allows the system to carry out its first task as it behaves as an "on-off-on" fluorescent sensor for pH windows. The "off" part of the window ranges from pH 6 to 8. In this interval, in which the carboxylate form of C343 is apically coordinated to the Cu2+ complex inside micelles, the device carries out its second task, that is, it behaves as a gauge for lipophilicity. For pHs between 6 and 8, molecules containing a COOH group are in their COO- form and distribute between bulk water and micelles proportionally to their lipophilicity. Upon entering the micelle, their COO- moiety competes for coordination with C343, displacing it from the Cu2+ centre, and this results in fluorescence revival, the intensity of which is also proportional to the lipophilicity of the examined molecule. We have chosen the physiological pH value (7.4) as the working pH, and we have examined the lipophilicity of fatty acids and of the widely used family of nonsteroidal anti-inflammatory drugs (NSAIDs). The device successfully measures their lipophilicity, expressing it with an "off-on" type fluorescent signal, as demonstrated by the correlation of the fluorescence increase with the logarithmic water/octanol partition coefficient (log P) and with the difference between the pK(a) observed in micelles and that measured in water for NSAIDs
Exploiting Micelle-Driven Coordination To Evaluate the Lipophilicity of Molecules
No full textThis is a systematic study based on the calculation of complexation constants between a Zn-complex solubilized in Triton X-100 micellar solutions and a series of linear mono- and dicarboxylic acids, under physiological pH conditions, that allowed the evaluation of the lipophilicity of these molecules. This empirical lipophilicity parameter describes conveniently the partition of organic molecules between hydrophobic microdomains and water. The results can be used to predict the lipophilicity of molecules with similar structure and allows the distinction of intrinsic contributions of the carboxylates and of the methylene groups to the lipophilicity of the molecul
A thermodynamic scale for lipophilicity: evaluating micelle-water distribution of mono- and di-carboxylates under physiological pH condition
No full textMolecular Self-Assembled Monolayers on NanoParticles Self-Assembled Monolayers: an easy optical method to calculate coating from molecular mxtures
No full textmonolayers of thiolatyed dye are obtained on monolayers of silver nanoparticles on glass. A method based on absorption spectra is presented, to determine the surface composition from the composition of the coating solution, in the case of mixed thiol
A fluorescent micellar lipophilicity-meter for carboxylates
No full textThe lipophilicity of molecules such as fatty acids can be measured with a fluorescent signal, due to theirability to penetrate inside micelles where a multicomponent complex is assembled. The more they are lipohilic, the more the enter the micelles, where, by ligand displacement, induce fluorescence variatio
- …
