Solvation Dynamics of the Fluorescent Probe PRODAN in Heterogeneous Environments: Contributions from the Locally Excited and Charge-Transferred States

Abstract

The coexistence of different excited states with different properties of the same chromophores could have significant consequences for the accurate characterization of solvation dynamics in a heterogeneous environment, such as a protein. The purpose of this work is to study the contributions of the locally excited (LE) and charge-transferred (CT) states of the fluorescent probe molecule 6-propionyl-2-(N,Ndimethylamino)naphthalene (PRODAN) to its solvation dynamics in the heterogeneous environment provided by reverse micelles formed by sodium 1,4-bis-(2-ethylhexyl) sulfosuccinate (AOT)/n-heptane/ water. We have found that the LE and CT states of PRODAN solvate on different time scales in reverse micelles (2 and ∼0.4 ns, respectively), consistent with results suggested in the literature, and have concluded that PRODAN's use as a probe of heterogeneous environments must be used with caution and that, more importantly, the same caution must be exercised with any chromophore capable of emitting from different excited states. ReceiVed: June 1, 2009; ReVised Manuscript ReceiVed: July 20, 2009 The coexistence of different excited states with different properties of the same chromophores could have significant consequences for the accurate characterization of solvation dynamics in a heterogeneous environment, such as a protein. The purpose of this work is to study the contributions of the locally excited (LE) and charge-transferred (CT) states of the fluorescent probe molecule 6-propionyl-2-(N,N-dimethylamino)naphthalene (PRODAN) to its solvation dynamics in the heterogeneous environment provided by reverse micelles formed by sodium 1,4-bis-(2-ethylhexyl) sulfosuccinate (AOT)/n-heptane/water. We have found that the LE and CT states of PRODAN solvate on different time scales in reverse micelles (2 and ∼0.4 ns, respectively), consistent with results suggested in the literature, and have concluded that PRODAN's use as a probe of heterogeneous environments must be used with caution and that, more importantly, the same caution must be exercised with any chromophore capable of emitting from different excited states.

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

“…[24,25] Moreover, we have shown the possibility of switching the state from where PRODAN emits by changing the properties of the AOT RM interfaces. [25] Adhikary et al, [40] by solvation dynamics, have found that the LE and ICT states of PRODAN solvate on different timescales in AOT RMs (2 and % 0.4 ns, respectively), consistent with our results. In consequence, the photophysics of PRODAN is very helpful to test the unique RM interface properties.…”

pH-Activated Nanoparticles for Controlled Topical Delivery of Farnesol To Disrupt Oral Biofilm Virulence

“…81, 82 Briefly, PRODAN® dissolved in methanol was aliquoted into black 96-well plates. After drying overnight, micelle solutions at a range of concentrations (0–2 mg/ml) were added and incubated overnight to achieve final PRODAN® concentrations of 5.45*10 −4 mg/ml.…”

Carbonyl-Twisted 6-Acyl-2-dialkylaminonaphthalenes as Solvent Acidity Sensors

“…15 Because the Stokes shift depends on both polarity and H-bonding, conclusions about micropolarity that are based on the Stokes shift must be considered carefully. 12,16 …”