Imaging of Flow Patterns with Fluorescent Molecular Rotors

Mustafic, Adnan; Huang, Hsiao‐Ping; Theodorakis, Emmanuel A.; Haidekker, Mark A.

doi:10.1007/s10895-010-0661-x

Cited by 25 publications

(41 citation statements)

References 17 publications

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“…Images of the intensity increase are strikingly similar to computed fluid dynamics simulations [20], but those images reveal minute irregularities of the flow system that would not normally be considered in computational fluid dynamics. Such a flow sensor has many potential applications in fluid dynamics studies, microfluidics, mixing problems, and closed-loop flow control.…”

Section: Discussionsupporting

confidence: 54%

“…Moreover, the sensitivity of the intensity increase at very low flow rates is unusually high, such that instruments of comparable sensitivity (e.g., heated-plate flow meters) show orders of magnitude lower spatial resolution, and flow measurement with comparable resolution (e.g., particle tracking) has much lower sensitivity. Based on our studies, prerequisite for flow sensitivity is a polar functional group on the molecular rotor and a polar solvent: DCVJ (1) does not exhibit this phenomenon at all, and a carboxylic-acid derivative (CCVJ, 2) does not exhibit this phenomenon in nonpolar fluids, such as hexanes [19,20]. Based on these findings, we hypothesized that either polar-polar interaction or hydrogen bond formation play a role in the apparent flow sensitivity.…”

Section: Introductionmentioning

confidence: 92%

“…With a suitable experimental setup, the apparent flow sensitivity of molecular rotors allows to take images of flow patterns in microfluidic chambers [20]. Moreover, the sensitivity of the intensity increase at very low flow rates is unusually high, such that instruments of comparable sensitivity (e.g., heated-plate flow meters) show orders of magnitude lower spatial resolution, and flow measurement with comparable resolution (e.g., particle tracking) has much lower sensitivity.…”

Section: Introductionmentioning

confidence: 99%

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Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

et al. 2015

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Fluorescent environment-sensitive dyes often change their spectral properties concomitantly with multiple solvent properties, such as polarity, protonation, hydrogen bond formation, or viscosity. Careful consideration of the response is needed when a fluorescent dye is used to report a single property. Recently, we observed an increase of emission intensity of viscosity-sensitive molecular rotors in fluids subject to flow and speculated that either polar-polar interaction or hydrogen bond formation play a role in the apparent flow sensitivity. In this study, we show experimental evidence that photoisomerization to an isomer with a lower quantum yield, first proposed by Rumble et al. (J Phys Chem A 116(44):10786-10792, 2012), plays a key role in the observed phenomenon. We subjected four molecular rotors with different electron acceptor motifs to fluid flow in solvents of different polarity and ability to form hydrogen bonds. We also measured the isomerization dynamics in a custom fluorophotometer with extremely low light exposure. Our results indicate that the photoisomerization rate depends both on the solvent and on the electron acceptor group, as does the recovery of the original isomer in the dark. In most solvents, recovery of the dark isomer is much more rapid than originally reported, and a state of quasiequilibrium between both isomers is possible. Moreover, the sensitivity (i.e., relative intensity increase at the same flow rate) is also solvent-dependent. The intensity increase can be detected at very low velocities (as low as 0.06 mm/s). Characteristic for fluorescent dyes is the high spatial resolution, and no flow measurement device with comparable sensitivity and spatial resolution exists, although the nature of the solvent needs to be taken into account for quantitative flow measurement.

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Section: Discussionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

et al. 2015

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“…10 Fluorescent molecular rotors 11 and aggregation-induced emission luminogens (AIEgens) 12 are representative types of steric-environment sensitive fluorophores, as they exhibit sizable changes in fluorescence intensity, lifetime, and spectral shape in response to subtle steric restrictions.…”

Section: Introductionmentioning

confidence: 99%

Highly Twisted N,N-Dialkylamines as a Design Strategy to Tune Simple Aromatic Hydrocarbons as Steric Environment-Sensitive Fluorophores

et al. 2016

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The steric-environment sensitivity of fluorescence of 9,10-bis(N,N-dialkylamino)anthracenes (BDAAs) was studied experimentally and theoretically. A new design strategy to tune simple aromatic hydrocarbons as efficient aggregation-induced emission (AIE) luminogens and molecular rotors is proposed. For a variety of BDAAs, prominent Stokes shifts and efficient solid-state fluorescence were observed. Calculations on BDAA-methyl suggested that in the ground state (S0) conformations, the pyramidal amine groups are highly twisted, so that their lone-pair orbitals cannot conjugate with the anthracene π orbitals. Fluorescence takes place from the S1 minima, in which one or both amine groups are planarized. The stability of the S1 excited state minima as well as destabilization of the S0 state is the origin of large Stokes shift. Experimental measurement of the nonadiabatic transition rate suggests that para disubstitution by dialkylamino (or strongly electron-donating) groups is a key for fast internal conversion. Minimum energy conical intersection (MECI) between S1 and S0 states was found to have a Dewar-benzene like structure. Although this can be reached efficiently in liquid phase for fast internal conversion, a large amplitude motion is required to reach this MECI, which is prohibited in the solid state and caused efficient AIE. This strategy is used to find experimentally that naphthalene analogues are also efficient AIE luminogens. The flexibility of alkyl chains on amino groups is also found to be important for allowed charge-transfer transition. Thus, three points [(1) highly twisted N,N-dialkylamines, (2) substitution at the para positions, (3) with flexible alkyl groups] were proposed for activation of small aromatic hydrocarbons.

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“…34 Auramine O, one of these fluorescent probes, belongs to the family of molecules called "molecular rotors." Such molecules are characterized by the ability to form, upon photoexcitation, twisted intramolecular charge transfer (TICT) states through the rotation of one segment of the structure with respect to the rest of the molecule.…”

Section: A Molecular Probementioning

confidence: 99%

Reconstruction by fluorescence imaging of the spatio-temporal evolution of the viscosity field in Hele-Shaw flows

et al. 2014

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We study the spatio-temporal evolution of the viscosity field during stable and unstable radial flows of glycerol-water solutions in a horizontal Hele-Shaw cell where a localized temperature gradient is imposed. The viscosity field is reconstructed from the measurement of the fluorescence emitted by a viscosity-sensitive molecular probe (Auramine O). For an immiscible flow, the viscosity and temperature fields are obtained accurately. For miscible displacements, we show how the interplay between the viscosity changes of both fluids and the variation of the fluid thickness in the gap prevents obtaining strict quantitative reconstruction of the viscosity field. We explain how the reconstructed viscosity field can nevertheless be interpreted to obtain information about the fluid thickness and the local viscosity and temperature.

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Imaging of Flow Patterns with Fluorescent Molecular Rotors

Cited by 25 publications

References 17 publications

Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

Highly Twisted N,N-Dialkylamines as a Design Strategy to Tune Simple Aromatic Hydrocarbons as Steric Environment-Sensitive Fluorophores

Reconstruction by fluorescence imaging of the spatio-temporal evolution of the viscosity field in Hele-Shaw flows

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