Transient light scattering of suspensions of charged nonspherical particles subjected to an electric field

Baloch, K.M; Ven, Theo G. M. van de

doi:10.1016/0021-9797(89)90418-9

Cited by 11 publications

(10 citation statements)

References 29 publications

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“…The transmission rises to a plateau, and tting the onset curves gives a reliable exponential rise $(1 À exp[Àt/s ON ]) with the characteristic timescale of structure formation s ON z 0.3 s. Following eld removal, the transmission also decayed exponentially with a longer characteristic time s OFF z 5 s. It has been shown that the relaxation in such an electro-optical signal as a result of rotational diffusive decay may be approximated (to rst order) as T/T 0 z exp[À6D r t], where D r is the rotational diffusion coefficient. 33 For the data shown in Fig. 2, D r z 0.03 s À1 is in good agreement with 0.01 s À1 calculated for rod-like particles with an aspect ratio of 20.…”

Section: Aggregation Time and Reversibilitysupporting

confidence: 81%

Fast and reversible microscale formation of columns in carbon nanotube suspensions

Wongsuwarn

Cicuta

et al. 2013

Soft Matter

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Homogeneous carbon nanotube suspensions are studied in the semidilute regime, which is permitted by the use of an effective polysiloxane surfactant, PySi70, as a liquid matrix. We study such suspensions under an AC electric field by optical microscopy, transient light transmission and impedance spectroscopy. Optical microscopy shows the formation of long-range microscale columnar order as a result of a fast field-induced phase separation. The aggregation process is found to be reversible and repeatable, with nanotubes re-dispersing into a homogeneous solution, in a diffusive manner, in the seconds following removal of the electric field. The suggested role of the induced dipolar forces is consistent with the relatively fast columnar formation and characteristic concentration of maximum field-response. The equilibrium columnar structure provides fast field-induced control of the transparency and dielectric response, while avoiding electrical breakdown.

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Section: Aggregation Time and Reversibilitysupporting

confidence: 81%

Fast and reversible microscale formation of columns in carbon nanotube suspensions

Wongsuwarn

Cicuta

et al. 2013

Soft Matter

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“…We note that the electrophoretic rotation discussed in this paper is distinct from the weak rotation caused by dielectric polarization. , Rotation by dielectric polarization is an E ∞ 2 effect that causes little rotation for E ∞ < 100 V/cm and diameters less than 10 μm. Electrophoretic rotation is proportional to E ∞ and is significant even for fields of 1 V/cm.…”

Section: Theory Of Electrophoretic Rotationmentioning

confidence: 62%

Probing the Structure of Colloidal Doublets by Electrophoretic Rotation

1996

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A doublet formed by the coagulation of two colloidal spheres rotates toward alignment with an applied electric field. The rotation rate is proportional to the difference in the zeta potentials of the two spheres and a geometric coefficient N. This coefficient can be calculated from the electrohydrodynamic equations and depends on the kinematic boundary condition imposed on the spheres. If the doublet rotates as a single rigid body, so that the surfaces of the two spheres do not move relative to one another, then the value of N is a factor of 2 or 3 smaller than if the two spheres are free to rotate relative to one another. Thus, one can evaluate the rigidity of the doublet by determining the value of N experimentally. We have tracked the motion of individual doublets formed from micrometer-size polystyrene latex spheres differing in zeta potential and determined the value of N for different solution conditions. The influence of Brownian motion was taken into account when interpreting the rotational trajectories of the doublets. Over a range of electrolyte concentration, pH, sphere size, and electric field, all the values of N agree with the theoretical values for rigid-body rotation. This result is surprising because in many of the experiments the conditions were such that the two spheres should have been in a secondary minimum with a gap between 5 and 20 nm according to classical DLVO theory. In these cases the freely-rotating condition on each sphere is expected. Possible explanations for the rigid-body behavior of the doublets are suggested.

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“…For small colloids, as the electric field approaches zero, 1/τ al should deviate from its linear relationship with E 2 and asymptotically approach 6 D r according to the theory ( D r is the rotary Brownian diffusion coefficient). However, the straight lines of 1/τ al vs E 2 in Figure pass through the origin.…”

Section: Resultsmentioning

confidence: 99%

“…for all scattering geometries, as well as for transmission, 3 and even for semiconcentrated dispersions. 24 Thus, the correlation is still valid in our electro-optics setup for changes in transmitted light.…”

Section: Electro-optics Studymentioning

confidence: 99%

“…Despite extensive research on electro-optics of colloidal dispersions ,, and the rapid progress in the study of nanotubes, there are few reports of electro-optics diagnostics applied to nanotubes. Kappes et al demonstrated that single-wall carbon nanotubes (SWNT) can be aligned by an alternating electric field; and because of their differences in polarizability, metallic tubes can be separated from semiconducting ones by dielectrophoresis.…”

Section: Introductionmentioning

confidence: 99%

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Electro-optics of Polymer Nanotube Dispersions

2011

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Polyelectrolyte-stabilized polymer nanotubes with high rigidity are electro-optically characterized in the dilute and semidilute regimes. Nanotube alignment with the electric field and subsequent orientation relaxation in the absence of electric field are confirmed by optical microscopy, and a simple UV−vis electro-optical setup is used to detect the transient light transmittance. The effects of ionic strength, pulse duration, electric field strength, and particle concentration on particle alignment and orientation relaxation dynamics were systematically varied. The charge-dependent field-induced interfacial polarization, particularly the double layer polarization, plays a predominant role in the thin-walled nanotube alignment, which diminishes with increasing salt screening, approaching predictions for uncharged dielectric tubes. The experimentally obtained rotary diffusivity from nanotube orientation relaxation dynamics agrees with theoretical predictions, with negligible ionic strength effects, indicating the absence of salt-induced aggregation events. When the scaled particle concentration ϕ/ϕ* increases from 0.06 to 15, the alignment is slowed by crowding, whereas the measured collective rotary diffusion coefficient increases due to the gradient of orientation probability.

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Transient light scattering of suspensions of charged nonspherical particles subjected to an electric field

Cited by 11 publications

References 29 publications

Fast and reversible microscale formation of columns in carbon nanotube suspensions

Fast and reversible microscale formation of columns in carbon nanotube suspensions

Probing the Structure of Colloidal Doublets by Electrophoretic Rotation

Electro-optics of Polymer Nanotube Dispersions

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