Light diffusion from non-spherical particles: rotational diffusion micro-rheology using ultrasound-assisted diffusing-wave spectroscopy

2019 ◽  
Author(s):  
Ram Mohan Vasu
Keyword(s):  
Rotational Diffusion ◽  
Spherical Particles ◽  
Diffusing Wave Spectroscopy ◽  
Light Diffusion ◽  
Ultrasound Assisted

Monte Carlo simulation of fluorescence correlation spectroscopy data

2011 ◽  
Vol 76 (3) ◽  
pp. 207-222 ◽  
Author(s):  
Peter Košovan ◽  
Filip Uhlík ◽  
Jitka Kuldová ◽  
Miroslav Štěpánek ◽  
Zuzana Limpouchová ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Diffusion Coefficients ◽  
Fluorescence Correlation Spectroscopy ◽  
Rotational Diffusion ◽  
Correlation Spectroscopy ◽  
Analytical Models ◽  
Spherical Particles ◽  
Fluorescence Signal ◽  
Fluorescence Correlation

We employed the Monte Carlo simulation methodology to emulate the diffusion of fluorescently labeled particles and understand the source of differences between values of diffusion coefficients (and consequently hydrodynamic radii) of fluorescently labeled nanoparticles measured by fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS). We used the simulation program developed in our laboratory and studied the diffusion of spherical particles of different sizes, which are labeled on their surface. In this study, we focused on two complicating effects: (i) multiple labeling and (ii) rotational diffusion which affect the fluorescence signal from large particles and hinder the analysis of autocorrelation functions according to simple analytical models. We have shown that the fluorescence fluctuations can be well fitted using the analytical model for small point-like particles, but the obtained parameters deviate in some cases significantly from the real ones. It means that the current data treatment yields apparent values of diffusion coefficients and other parameters only and the interpretation of experimental results for systems of particles with sizes comparable to the size of the active illuminated volume requires great care and precaution.

Fluorescence correlation spectroscopy applied to rotational diffusion of macromolecules

1976 ◽  
Vol 9 (1) ◽  
pp. 69-81 ◽  
Author(s):  
Måns Ehrenberg ◽  
Rudolf Rigler
Keyword(s):  
Rotational Motion ◽  
Fluorescence Correlation Spectroscopy ◽  
Rotational Diffusion ◽  
Quantitative Relationship ◽  
Correlation Spectroscopy ◽  
Spherical Particles ◽  
Fluorescence Correlation ◽  
Fluorescence Light

A quantitative relationship between polarization properties of fluorescence light and molecular rotational diffusion was first derived by Perrin (1926). His results, which concerned spherical particles, have later been refined to the more complex rotational motion of asymmetric bodies (Memming, 1961; Chuang & Eisenthal, 1972; Ehrenberg & Rigler, 1972; Belford, Belford & Weber, 1972).

scholarly journals Light diffusion and diffusing-wave spectroscopy in nematic liquid crystals

1997 ◽  
Vol 14 (1) ◽  
pp. 156 ◽  
Author(s):  
H. Stark ◽  
M. H. Kao ◽  
K. A. Jester ◽  
T. C. Lubensky ◽  
A. G. Yodh ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Diffusing Wave Spectroscopy ◽  
Light Diffusion

scholarly journals Orthotropic elastic moduli of biological tissues from ultrasound-assisted diffusing-wave spectroscopy

2017 ◽  
Vol 34 (11) ◽  
pp. 1945
Author(s):  
Dibbyan Mazumder ◽  
Gurudas Kar ◽  
Ram Mohan Vasu ◽  
Debasish Roy ◽  
Rajan Kanhirodan
Keyword(s):  
Elastic Moduli ◽  
Biological Tissues ◽  
Diffusing Wave Spectroscopy ◽  
Ultrasound Assisted

scholarly journals Assessment of Analytical Orientation Prediction Models for Suspensions Containing Fibers and Spheres

2021 ◽  
Vol 5 (4) ◽  
pp. 107
Author(s):  
Bastien Dietemann ◽  
Fatih Bosna ◽  
Harald Kruggel-Emden ◽  
Torsten Kraft ◽  
Claas Bierwisch
Keyword(s):  
Diffusion Model ◽  
Prediction Models ◽  
Rotational Diffusion ◽  
Spherical Particles ◽  
Model Parameters ◽  
Closure Model ◽  
Filling Fraction ◽  
Complex Orientation ◽  
Complex Models ◽  
Rotary Diffusion

Analytical orientation models like the Folgar Tucker (FT) model are widely applied to predict the orientation of suspended non-spherical particles. The accuracy of these models depends on empirical model parameters. In this work, we assess how well analytical orientation models can predict the orientation of suspensions not only consisting of fibers but also of an additional second particle type in the shape of disks, which are varied in size and filling fraction. We mainly focus on the FT model, and we also compare its accuracy to more complex models like Reduced-Strain Closure model (RSC), Moldflow Rotational Diffusion model (MRD), and Anisotropic Rotary Diffusion model (ARD). In our work, we address the following questions. First, can the FT model predict the orientation of suspensions despite the additional particle phase affecting the rotation of the fibers? Second, is it possible to formulate an expression for the sole Folgar Tucker model parameter that is based on the suspension composition? Third, is there an advantage to choose more complex orientation prediction models that require the adjustment of additional model parameters?

STEM Study of Surface Plasmon Excitation in Small Spherical Particles

1990 ◽  
Vol 48 (2) ◽  
pp. 42-43
Author(s):  
Daniel UGARTE
Keyword(s):  
Energy Loss ◽  
Spherical Particles ◽  
Small Particles ◽  
Bulk Materials ◽  
Low Loss ◽  
Plasmon Excitation ◽  
Surface Modes ◽  
Surface Plasmon Excitation ◽  
Analytical Electron ◽  
Analytical Electron Microscope

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.

Sign in / Sign up

Export Citation Format

Share Document