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Reinosuke Hayakawa - One of the best experts on this subject based on the ideXlab platform.

  • electrophoretic microrheology of a dilute lamellar phase relaxation mechanisms in frequency dependent mobility of nanometer sized particles between soft membranes
    Physical Review E, 2004
    Co-Authors: Daisuke Mizuno, Yasuyuki Kimura, Reinosuke Hayakawa
    Abstract:

    : Viscoelastic properties of complex fluids in the microscopic scale can be studied by measuring the transport properties of small, embedded probe particles. We have measured the complex electrophoretic mobility micro*(omega) of nanometer-sized particles dispersed in a lyotropic lamellar phase, which shows two relaxation processes at approximately 1 kHz (high frequency relaxation, HF) and 1 Hz (low frequency relaxation, LF). It is shown quantitatively that these processes are caused by the trapping of particles within two local structures of characteristic size in the lamellar phase: the interbilayer distance and the persistence length. The origin of observed relaxations is further investigated and augmented in this study with data obtained by two other complementary methods, dielectric spectroscopy and the direct observation of fluorescently labelled probe particles under an optical microscope. It is shown that the local Distortion Field of the lamellar phase is induced by the extra steric interaction involving the collision of a colloidal particle with the membrane. The resulting Distortion Field hinders the Brownian motion of colloidal particles parallel to the membranes (not vertical), and causes the observed HF relaxation. On the other hand, the origin of LF relaxation is presumably a result of the defects in the lamellar structure. Since the results of this study show that the transport property is strongly influenced by microscopic environments, this method is referred to as electrophoretic microrheology.

  • electrophoretic microrheology in a dilute lamellar phase of a nonionic surfactant
    Physical Review Letters, 2001
    Co-Authors: Daisuke Mizuno, Yasuyuki Kimura, Reinosuke Hayakawa
    Abstract:

    We measured the complex electrophoretic mobility ${\ensuremath{\mu}}^{*}(\ensuremath{\omega})$ of nanometer-sized particles dispersed in a lyotropic lamellar phase, and observed two relaxation processes corresponding to the two characteristic lengths of lamellar structure. Faster relaxation is caused by the Distortion Field of lamellar phase induced by the colloidal particles, and slower relaxation is presumably due to the defects in lamellar structure. Since the dynamic transport property is strongly influenced by the microscopic circumstances as shown in this paper, this method is referred to as electrophoretic microrheology.

Cesare Soci - One of the best experts on this subject based on the ideXlab platform.

  • polaron self localization in white light emitting hybrid perovskites
    Journal of Materials Chemistry C, 2017
    Co-Authors: Daniele Cortecchia, Jeanluc Bredas, Jun Yin, Annalisa Bruno, Gagik G Gurzadyan, Subodh Mhaisalkar, Cesare Soci
    Abstract:

    Two-dimensional (2D) perovskites with the general formula APbX4 are attracting increasing interest as solution processable, white-light emissive materials. Recent studies have shown that their broadband emission is related to the formation of intra-gap colour centres. Here, we provide an in-depth description of the charge localization sites underlying the generation of such radiative centres and their corresponding decay dynamics, highlighting the formation of small polarons trapped within their lattice Distortion Field. Using a combination of spectroscopic techniques and first-principles calculations to study the white-light emitting 2D perovskites (EDBE)PbCl4 and (EDBE)PbBr4, we infer the formation of Pb23+, Pb3+, and X2− (where X = Cl or Br) species confined within the inorganic perovskite framework. Due to strong Coulombic interactions, these species retain their original excitonic character and form self-trapped polaron–excitons acting as radiative colour centres. These findings are expected to be relevant for a broad class of white-light emitting perovskites with large polaron relaxation energy.

  • polaron self localization in white light emitting hybrid perovskites
    arXiv: Materials Science, 2016
    Co-Authors: Daniele Cortecchia, Jeanluc Bredas, Jun Yin, Annalisa Bruno, Gagik G Gurzadyan, Subodh Mhaisalkar, Cesare Soci
    Abstract:

    Two-dimensional (2D) perovskites with general formula $APbX_4$ are attracting increasing interest as solution processable, white-light emissive materials. Recent studies have shown that their broadband emission is related to the formation of intra-gap color centers; however, the nature and dynamics of the emissive species have remained elusive. Here we show that the broadband photoluminescence of the 2D perovskites $(EDBE)PbCl_4$ and $(EDBE)PbBr_4$ stems from the localization of small polarons within the lattice Distortion Field. Using a combination of spectroscopic techniques and first-principles calculations, we infer the formation of ${Pb_2}^{3+}$, $Pb^{3+}$, and ${X_2}^-$ (where X=Cl or Br) species confined within the inorganic perovskite framework. Due to strong Coulombic interactions, these species retain their original excitonic character and form self-trapped polaron-excitons acting as radiative color centers. These findings are expected to be applicable to a broad class of white-light emitting perovskites with large polaron relaxation energy.

Ralf Tonner - One of the best experts on this subject based on the ideXlab platform.

  • ab initio calculations of the concentration dependent band gap reduction in dilute nitrides
    Physical Review B, 2018
    Co-Authors: Phil Rosenow, Lars C Bannow, Eric W Fischer, Stephan W Koch, W Stolz, K Volz, Ralf Tonner
    Abstract:

    While being of persistent interest for the integration of lattice-matched laser devices with silicon circuits, the electronic structure of dilute nitride III/V-semiconductors has presented a challenge to ab initio computational approaches. The origin of the computational problems is the strong Distortion exerted by the N atoms on most host materials. Here, these issues are resolved by combining density functional theory calculations based on the meta-GGA functional presented by Tran and Blaha (TB09) with a supercell approach for the dilute nitride Ga(NAs). Exploring the requirements posed to supercells, it is shown that the Distortion Field of a single N atom must be allowed to decrease so far that it does not overlap with its periodic images. This also prevents spurious electronic interactions between translational symmetric atoms, allowing us to compute band gaps in very good agreement with experimentally derived reference values. In addition to existing approaches, these results offer a promising ab initio avenue to the electronic structure of dilute nitride semiconductor compounds.

Jun Yin - One of the best experts on this subject based on the ideXlab platform.

  • polaron self localization in white light emitting hybrid perovskites
    Journal of Materials Chemistry C, 2017
    Co-Authors: Daniele Cortecchia, Jeanluc Bredas, Jun Yin, Annalisa Bruno, Gagik G Gurzadyan, Subodh Mhaisalkar, Cesare Soci
    Abstract:

    Two-dimensional (2D) perovskites with the general formula APbX4 are attracting increasing interest as solution processable, white-light emissive materials. Recent studies have shown that their broadband emission is related to the formation of intra-gap colour centres. Here, we provide an in-depth description of the charge localization sites underlying the generation of such radiative centres and their corresponding decay dynamics, highlighting the formation of small polarons trapped within their lattice Distortion Field. Using a combination of spectroscopic techniques and first-principles calculations to study the white-light emitting 2D perovskites (EDBE)PbCl4 and (EDBE)PbBr4, we infer the formation of Pb23+, Pb3+, and X2− (where X = Cl or Br) species confined within the inorganic perovskite framework. Due to strong Coulombic interactions, these species retain their original excitonic character and form self-trapped polaron–excitons acting as radiative colour centres. These findings are expected to be relevant for a broad class of white-light emitting perovskites with large polaron relaxation energy.

  • polaron self localization in white light emitting hybrid perovskites
    arXiv: Materials Science, 2016
    Co-Authors: Daniele Cortecchia, Jeanluc Bredas, Jun Yin, Annalisa Bruno, Gagik G Gurzadyan, Subodh Mhaisalkar, Cesare Soci
    Abstract:

    Two-dimensional (2D) perovskites with general formula $APbX_4$ are attracting increasing interest as solution processable, white-light emissive materials. Recent studies have shown that their broadband emission is related to the formation of intra-gap color centers; however, the nature and dynamics of the emissive species have remained elusive. Here we show that the broadband photoluminescence of the 2D perovskites $(EDBE)PbCl_4$ and $(EDBE)PbBr_4$ stems from the localization of small polarons within the lattice Distortion Field. Using a combination of spectroscopic techniques and first-principles calculations, we infer the formation of ${Pb_2}^{3+}$, $Pb^{3+}$, and ${X_2}^-$ (where X=Cl or Br) species confined within the inorganic perovskite framework. Due to strong Coulombic interactions, these species retain their original excitonic character and form self-trapped polaron-excitons acting as radiative color centers. These findings are expected to be applicable to a broad class of white-light emitting perovskites with large polaron relaxation energy.

Daisuke Mizuno - One of the best experts on this subject based on the ideXlab platform.

  • electrophoretic microrheology of a dilute lamellar phase relaxation mechanisms in frequency dependent mobility of nanometer sized particles between soft membranes
    Physical Review E, 2004
    Co-Authors: Daisuke Mizuno, Yasuyuki Kimura, Reinosuke Hayakawa
    Abstract:

    : Viscoelastic properties of complex fluids in the microscopic scale can be studied by measuring the transport properties of small, embedded probe particles. We have measured the complex electrophoretic mobility micro*(omega) of nanometer-sized particles dispersed in a lyotropic lamellar phase, which shows two relaxation processes at approximately 1 kHz (high frequency relaxation, HF) and 1 Hz (low frequency relaxation, LF). It is shown quantitatively that these processes are caused by the trapping of particles within two local structures of characteristic size in the lamellar phase: the interbilayer distance and the persistence length. The origin of observed relaxations is further investigated and augmented in this study with data obtained by two other complementary methods, dielectric spectroscopy and the direct observation of fluorescently labelled probe particles under an optical microscope. It is shown that the local Distortion Field of the lamellar phase is induced by the extra steric interaction involving the collision of a colloidal particle with the membrane. The resulting Distortion Field hinders the Brownian motion of colloidal particles parallel to the membranes (not vertical), and causes the observed HF relaxation. On the other hand, the origin of LF relaxation is presumably a result of the defects in the lamellar structure. Since the results of this study show that the transport property is strongly influenced by microscopic environments, this method is referred to as electrophoretic microrheology.

  • electrophoretic microrheology in a dilute lamellar phase of a nonionic surfactant
    Physical Review Letters, 2001
    Co-Authors: Daisuke Mizuno, Yasuyuki Kimura, Reinosuke Hayakawa
    Abstract:

    We measured the complex electrophoretic mobility ${\ensuremath{\mu}}^{*}(\ensuremath{\omega})$ of nanometer-sized particles dispersed in a lyotropic lamellar phase, and observed two relaxation processes corresponding to the two characteristic lengths of lamellar structure. Faster relaxation is caused by the Distortion Field of lamellar phase induced by the colloidal particles, and slower relaxation is presumably due to the defects in lamellar structure. Since the dynamic transport property is strongly influenced by the microscopic circumstances as shown in this paper, this method is referred to as electrophoretic microrheology.