On the mechanism of photoinduced phase transitions in ternary liquid crystal systems near thermal equilibrium

Quevedo, Wilson; Petri, M.; Busse, G.; Techert, Simone

doi:10.1063/1.2943200

Cited by 13 publications

(16 citation statements)

References 31 publications

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“…The ternary mixture is dye-sensitized, so the optical infrared pulse excites solid matter coherently introducing a heat-jump on the system. The excitation mechanism has already been extensively studied on similar lyotropic liquid crystals [19]. Note that in the present case, the excitation conditions are well within the Stokes regime leading to a highly efficient energy transfer from the dye to the surrounding liquid crystal following a temperature jump scheme.…”

Section: Resultsmentioning

confidence: 82%

“…The system of investigation is a ternary mixture composed of C 16 E 7 /paraffin/glycerol/formamide and is photo-sensitized with the infrared laser dye IR 5 [18]. Our past studies show the possibility to photo-induce phase transitions in similar ternary lyotropic liquid crystal systems [19] upon optical excitation. In this work, the focus is on the stability of structural liquid crystal nano-ensembles formed within the ternary mixture.…”

Section: Introductionmentioning

confidence: 99%

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Time-Resolved Soft X-ray Diffraction Reveals Transient Structural Distortions of Ternary Liquid Crystals

Quevedo

Peth

Busse

et al. 2009

IJMS

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Home-based soft X-ray time-resolved scattering experiments with nanosecond time resolution (10 ns) and nanometer spatial resolution were carried out at a table top soft X-ray plasma source (2.2–5.2 nm). The investigated system was the lyotropic liquid crystal C16E7/paraffin/glycerol/formamide/IR 5. Usually, major changes in physical, chemical, and/or optical properties of the sample occur as a result of structural changes and shrinking morphology. Here, these effects occur as a consequence of the energy absorption in the sample upon optical laser excitation in the IR regime. The liquid crystal shows changes in the structural response within few hundred nanoseconds showing a time decay of 182 ns. A decrease of the Bragg peak diffracted intensity of 30% and a coherent macroscopic movement of the Bragg reflection are found as a response to the optical pump. The Bragg reflection movement is established to be isotropic and diffusion controlled (1 μs). Structural processes are analyzed in the Patterson analysis framework of the time-varying diffraction peaks revealing that the inter-lamellar distance increases by 2.7 Å resulting in an elongation of the coherently expanding lamella crystallite. The present studies emphasize the possibility of applying TR-SXRD techniques for studying the mechanical dynamics of nanosystems.

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Section: Resultsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Time-Resolved Soft X-ray Diffraction Reveals Transient Structural Distortions of Ternary Liquid Crystals

Quevedo

Peth

Busse

et al. 2009

IJMS

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“…15 Our earlier studies show the possibility to photoinduce phase transitions in similar photosensitized ternary lyotropic LC systems. 16,17 In the present work, the fluorescence lifetime of the dye IR 5 is in the picosecond regime and has an absorption maximum at 1090 nm. The energy is transferred from the dye to the system via collision, hence increasing the temperature of the system.…”

Section: Introductionmentioning

confidence: 98%

Nanosecond Dynamics of Photoexcited Lyotropic Liquid Crystal Structures

et al. 2010

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Home-based soft X-ray time-resolved diffraction (TR-SXD) experiments with nanosecond time resolution (10 ns) and nanometer spatial resolution were carried out at a tabletop soft X-ray plasma source (2.7-5.9 nm). The investigated system was the lyotropic liquid crystal C(16)E(7)/paraffin/glycerol/formamide/IR 5. Usually, major changes in physical, chemical, and/or optical properties of the sample result from structural changes and shrinking morphology. Here, these effects occur as a consequence of the energy absorption in the sample upon optical laser excitation in the IR regime. The variations observed are integral intensity modulations and displacement in the Bragg diffraction angle. To follow the diffracted integral intensity changes, Patterson analysis was used, and the lattice parameter d variations have been followed by applying the Bragg diffraction law. The experimental intensity modulations occur on the nanosecond time scale, and they are assigned to photoinduced diffusion processes within the liquid crystalline phase. The structural response after photoexcitation is experimentally observed as an increase of the lattice constant by 0.5-1 A and is interpreted as a decrease of order in the liquid crystalline phase. This coincides with a reorientation to a photocreated liquid crystal lattice in the surface plane and with respect to the E-field vector of the laser light. The present studies emphasize the possibility of using TR-SXD techniques for studying the transient mechanical dynamics of nanosystems at the submicrosecond time scale.

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“…The lamellar structure [ Fig. 1(d)] is typical for such long carbon chain compounds [12] and is similar to that of fibrils, nanotubes, or liquid crystals [2]. Scanning electron microscopy investigations reveal a needlelike morphology [20 nm in diameter, between 1.5 and 20 m long, Fig.…”

mentioning

confidence: 95%

“…They can be used to determine the electron density distribution of aperiodic systems and to determine the periodic structures of nanoensembles with lattice constants of about 5-10 nm and bigger, i.e., of periodic selfassembled structures or macromolecular crystals [1,2]. Structural studies on such materials are of particular importance for the development of nanoconfined materials with new and extraordinary physical, chemical, or medical properties [3][4][5].…”

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confidence: 99%

Diffraction Properties of Periodic Lattices under Free Electron Laser Radiation

et al. 2010

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In this Letter, we report the pioneering use of free electron laser radiation for the investigation of periodic crystalline structures. The diffraction properties of silver behenate single nanocrystals (5.8 nm periodicity) with the dimensions of 20 nm Â 20 nm Â 20 m and as powder with grain sizes smaller than 200 nm were investigated with 8 nm free electron laser radiation in single-shot modus with 30 fs long free electron laser pulses. This work emphasizes the possibility of using soft x-ray free electron laser radiation for these crystallographic studies on a nanometer scale.

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On the mechanism of photoinduced phase transitions in ternary liquid crystal systems near thermal equilibrium

Cited by 13 publications

References 31 publications

Time-Resolved Soft X-ray Diffraction Reveals Transient Structural Distortions of Ternary Liquid Crystals

Time-Resolved Soft X-ray Diffraction Reveals Transient Structural Distortions of Ternary Liquid Crystals

Nanosecond Dynamics of Photoexcited Lyotropic Liquid Crystal Structures

Diffraction Properties of Periodic Lattices under Free Electron Laser Radiation

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