Molecular Orientation at Surfaces:  Surface Roughness Contributions to Measurements Based on Linear Dichroism

Simpson, Garth J.; Rowlen, Kathy L.

doi:10.1021/jp983912k

Cited by 28 publications

(41 citation statements)

References 66 publications

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“…56 For the specific case of 2n ) 2, the expression reproduces the result already reported by others 54 and later derived by Simpson and Rowlen using a different approach to account for surface roughness effects on the second order parameter, 〈P 2 (cos θ)〉. 55 Here, we also extend the expression for any even order parameter, as TIRF experimental results also contain information on 〈P 4 (cos θ)〉. The experimentally determined order parameters relating to θ (the angle between the absorption dipole and the lab surface normal) inherently include these factors, so it is useful to be able to factor them out in order to recover the distribution of the molecule with respect to the local surface plane.…”

Section: Polarized Fluorescencesupporting

confidence: 82%

Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution Based on the Maximum Entropy Method

2006

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This article describes two mathematical formalisms for the determination of the second and fourth order parameters of molecular films using optical spectroscopy. Method A uses polarized total internal reflection fluorescence (TIRF) to calculate the second and fourth order parameters, 〈P 2 (cos θ)〉 and 〈P 4 (cos θ)〉, using an independently determined value for the angle between the absorption and emission dipoles, γ. Method B uses 〈P 2 (cos θ)〉 obtained from attenuated total reflectance (ATR) data, along with polarized TIRF measurements to calculate 〈P 4 (cos θ)〉 and 〈cos 2 γ〉. The choice of a specific method should rely on experimental considerations. We also present a method to separate the contributions of substrate surface roughness and dipole orientation with respect to the molecular axis from the spectroscopically determined second and fourth order parameters. Finally, a maximum entropy approach for construction of an orientation distribution from order parameters is compared with the commonly used delta and Gaussian distributions.

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Section: Polarized Fluorescencesupporting

confidence: 82%

Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution Based on the Maximum Entropy Method

2006

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“…12 It was shown that for an anisotropic media a surface scattering does not affect the retardance values but has an impact on linear dichroism values. 28 The quadratic dependence of α L , α 44 , and α LA on thickness is also confirmed within the experimental range of errors. Moreover, an anisotropic depolarization effect…”

Section: Scb Modelsupporting

confidence: 67%

Analysis of tissue microstructure with Mueller microscopy: logarithmic decomposition and Monte Carlo modeling

Lee

Chandel

et al. 2020

J. Biomed. Opt.

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Significance: Definitive diagnostics of many diseases is based on the histological analysis of thin tissue cuts with optical white light microscopy. Extra information on tissue structural properties obtained with polarized light would help the pathologist to improve the accuracy of his diagnosis.Aim: We report on using Mueller matrix microscopy data, logarithmic decomposition, and polarized Monte Carlo (MC) modeling for qualitative and quantitative analysis of thin tissue cuts to extract the information on tissue microstructure that is not available with a conventional white light microscopy.Approach: Unstained cuts of human skin equivalents were measured with a custom-built liquidcrystal-based Mueller microscope in transmission configuration. To interpret experimental data, we performed the simulations with a polarized MC algorithm for scattering anisotropic media. Several optical models of tissue (spherical scatterers within birefringent host medium, and combination of spherical and cylindrical scatterers within either isotropic or birefringent host medium) were tested.Results: A set of rotation invariants for the logarithmic decomposition of a Mueller matrix was derived to rule out the impact of sample orientation. These invariants were calculated for both simulated and measured Mueller matrices of the dermal layer of skin equivalents. We demonstrated that only the simulations with a model combining both spherical and cylindrical scatterers within birefringent host medium reproduced the experimental trends in optical properties of the dermal layer (linear retardance, linear dichroism, and anisotropic linear depolarization) with layer thickness.Conclusions: Our studies prove that Mueller polarimetry provides relevant information not only on a size of dominant scatterers (e.g., cell nuclei versus subwavelength organelles) but also on its shape (e.g., cells versus collagen fibers). The latter is directly related to the state of extracellular collagen matrix, which is often affected by early pathology. Hence, using polarimetric data can help to increase the accuracy of diagnosis.

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“…(10) with κ 0 = 0), and a microscopic expression which is derived from density functional theory (Eqs. (14) and (19)). Within the Gaussian approximation we have calculated the ensuing variances for the local interface positions and for its derivatives (Eqs.…”

Section: Discussionmentioning

confidence: 94%

“…Unrelated to this latter aspect, in a series of papers Simpson and Rowlen studied the surface roughness contributions to measurements, based on linear dichroism, of the molecular orientations of optically active molecules adsorbed on rough solid surfaces [13,14,15]. In order to infer from such data the local molecular orientation they must be corrected by the effects due to the frozen orientational fluctuations of the rough supporting substrate.…”

Section: Introductionmentioning

confidence: 99%

Local orientations of fluctuating fluid interfaces

Mecke

Dietrich

2005

The Journal of Chemical Physics

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Thermal fluctuations cause the local normal vectors of fluid interfaces to deviate from the vertical direction defined by the flat mean interface position. This leads to a nonzero mean value of the corresponding polar tilt angle which renders a characterization of the thermal state of an interface. Based on the concept of an effective interface Hamiltonian we determine the variances of the local interface position and of its lateral derivatives. This leads to the probability distribution functions for the metric of the interface and for the tilt angle which allows us to calculate its mean value and its mean square deviation. We compare the temperature dependences of these quantities as predicted by the simple capillary wave model, by an improved phenomenological model, and by the microscopic effective interface Hamiltonian derived from density functional theory. The mean tilt angle discriminates clearly between these theoretical approaches and emphasizes the importance of the variation of the surface tension at small wave lengths. Also the tilt angle two-point correlation function is determined which renders an additional structural characterization of interfacial fluctuations. Various experimental accesses to measure the local orientational fluctuations are discussed.

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Molecular Orientation at Surfaces: Surface Roughness Contributions to Measurements Based on Linear Dichroism

Cited by 28 publications

References 66 publications

Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution Based on the Maximum Entropy Method

Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution Based on the Maximum Entropy Method

Analysis of tissue microstructure with Mueller microscopy: logarithmic decomposition and Monte Carlo modeling

Local orientations of fluctuating fluid interfaces

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