The use of acridine orange base (AOB) as molecular probe to characterize nonaqueous AOT reverse micelles

Falcone, R. Darío; Correa, N. Mariano; Biasutti, M. Alicia; Silber, Juana J.

doi:10.1016/j.jcis.2005.08.049

Cited by 53 publications

(78 citation statements)

References 53 publications

(111 reference statements)

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“…Moreover, different emission maxima are observed at different excitation wavelengths (results not shown) due to the PRODAN heterogeneity in the ground state of the molecule. [58] Indeed, PRODAN emits from two different microenvironments: the organic nonpolar pseudophase and the RM interfaces. The K p values calculated from the PRODAN emission spectral changes obtained by varying the surfactant concentration are gathered in Table S1 (Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Comparison between Two Anionic Reverse Micelle Interfaces: The Role of Water–Surfactant Interactions in Interfacial Properties

Quintana¹,

Falcone²,

Silber³

et al. 2011

ChemPhysChem

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The water/sodium bis(2-ethylhexyl) phosphate (NaDEHP) reverse micelle (RM) system is revisited by using, for the first time, molecular probes to investigate interface properties. The solvatochromic behavior of 1-methyl-8-oxyquinolinium betaine (QB) and 6-propionyl-2-(N,N-dimethyl)aminonaphthalene (PRODAN) in the water/NaDEHP/toluene system is studied, and the results are compared with those obtained in water/sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT)/toluene RM media. The results demonstrate that the micropolarity, microviscosity, interfacial water structure, molecular probe partition, and intramolecular electron-transfer processes are dramatically altered for NaDEHP RM interfaces in comparison to the AOT systems. Because of organic nonpolar solvent penetration into the interface, NaDEHP RM media offer an interface with lower micropolarity and microviscosity than AOT media. Also, the interfacial water in the NaDEHP system shows enhanced water-water hydrogen-bond interaction in comparison with bulk water. The AOT RM interface represents a unique environment for PRODAN to undergo dual emission.

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Section: Resultsmentioning

confidence: 99%

Comparison between Two Anionic Reverse Micelle Interfaces: The Role of Water–Surfactant Interactions in Interfacial Properties

Quintana¹,

Falcone²,

Silber³

et al. 2011

ChemPhysChem

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“…[10,18,20] For example, FTIR [10,11,18,19] and 1 H NMR [18,20] spectroscopy have shown that GY and EG interact with the AOT surfactant polar head through H-bond interactions that maintain the typical spherical reverse micelle structure but break the solvent H-bond structure present in the bulk. [6,16,18,19] Thus, even at the highest solvent loading, that is, when W S is between two and four, EG and GY show no evidence of the presence of bulklike solvent interactions inside the reverse micelles. In contrast, recent studies have shown that FA inside AOT reverse micelles conserves the bulklike intersolvent H-bond interactions.…”

Section: [Water]/a C H T U N G T R E N N U N G [Aot] = 10 (Aqueous) Wmentioning

confidence: 99%

“…To do this, we used different approaches: i) invasive techniques, such as absorption and emission spectroscopy of different molecular probes dissolved in different nonaqueous reverse micelles media, [16,17,19,28,29] and ii) noninvasive techniques, such as FTIR and 1 H NMR spectroscopy, [18,20,25] where the main effort was focused on the interpretation of the spectra of different polar solvents encapsulated inside reverse micelles to gain insights into their structure and the existence or not of a polar solvent pool. Thus, we have followed how the n OD or the n ND bands for EG, GY, PG, and FA change as the W S ratio increases.…”

Section: [Water]/a C H T U N G T R E N N U N G [Aot] = 10 (Aqueous) Wmentioning

confidence: 99%

Effect of the Constrained Environment on the Interactions between the Surfactant and Different Polar Solvents Encapsulated within AOT Reverse Micelles

et al. 2009

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Herein, we report a study of the interactions between different nonaqueous polar solvents, namely, ethylene glycol (EG), propylene glycol (PG), glycerol (GY), dimethylformamide (DMF), and dimethylacetamide (DMA), and the polar heads of sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) in nonaqueous AOT/n-heptane reverse micelles. The goal of our study is to gain insights into the unique reverse-micelle microenvironment created upon encapsulation of these polar solvents. For the first time, the study is focused on determining which regions of the AOT molecular structure are involved in the interactions with the polar solvents. We use FTIR spectroscopy--a noninvasive technique--to follow the changes in the AOT C=O band and the symmetric and asymmetric SO(3)(-) vibration modes upon increasing the content of polar solvents in the micelles. The results show that GY interacts through H bonds with the SO(3)(-) group, thereby removing the Na(+) counterions from the interface remaining in the polar core of the micelles. PG and EG interact through H bonds, mainly with the C=O group of AOT, penetrating into the oil side of the interface. Thus, they interact weakly with the Na(+) counterion, which seems to be close to the AOT sulfonate group. Finally, DMF and DMA, encapsulated inside the reverse micelles, interact neither with the C=O nor with the SO(3)(-) groups, but their weakly bulk-associated structure is broken because of the interactions with Na(+). We suggest that DMF and DMA can complex the Na(+) ions through their carbonyl and nitrogen groups. Hence, our results do not only give insights into how the constrained environment affects the bulk properties of polar solvents encapsulated within reverse micelles but--more importantly--they also help us to answer the tricky question about which regions of the AOT moiety are involved in the interactions with the polar solvents. We believe that our results show a clear picture of the interactions present at the nonaqueous reverse-micelle interface; this is important because these media are interesting nanoreactors for heterogeneous chemistry, templates for nanoparticles, and models for membranes.

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“…6,34,36,50 This model considers the reverse micelle as a distinct pseudophase whose properties are independent of the AOT concentration and are only determined by the value of the characteristic parameter W S . In this model, only two solubilization sites are considered, that is, the external solvent and the reverse micelle interface (i.e.…”

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confidence: 99%

“…From the slope of these plots, the value of K b can be calculated in the range of [AOT] concentrations where the equilibrium between the bound and free nitroaniline was observed. 17,18,36 A linear regression analysis leads to the K b values reported in Table 1. This The order of the K b values follows: GY < water < EG ~ W S = 0 ~ FA < DMF ~ DMA (Table 1).…”

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Binding of o-nitroaniline to nonaqueous AOT reverse micelles

Falcone¹,

Silber²,

Biasutti³

et al. 2011

Arkivoc

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The use of acridine orange base (AOB) as molecular probe to characterize nonaqueous AOT reverse micelles

Cited by 53 publications

References 53 publications

Comparison between Two Anionic Reverse Micelle Interfaces: The Role of Water–Surfactant Interactions in Interfacial Properties

Comparison between Two Anionic Reverse Micelle Interfaces: The Role of Water–Surfactant Interactions in Interfacial Properties

Effect of the Constrained Environment on the Interactions between the Surfactant and Different Polar Solvents Encapsulated within AOT Reverse Micelles

Binding of o-nitroaniline to nonaqueous AOT reverse micelles

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