Electric field induced birefringence in non-aqueous dispersions of mineral nanorods

Cotte, Alexis de la; Merzeau, Pascal; Kim, Jong Wook; Lahlil, Khalid; Boilot, Jean‐Pierre; Gacoin, Thierry; Grelet, Éric

doi:10.1039/c5sm01427a

Cited by 13 publications

(18 citation statements)

References 38 publications

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“…Combination of these approaches has been useful to prepare active devices modulating strong anisotropic properties by reversibly controlling the director of organized particles with external fields (e.g. electro-optical device 11,13,22 ).…”

Section: Introductionmentioning

confidence: 99%

Measuring the order parameter of vertically aligned nanorod assemblies

et al. 2021

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Section: Introductionmentioning

confidence: 99%

Measuring the order parameter of vertically aligned nanorod assemblies

et al. 2021

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“…[45] The TEB signal carries a specific signature when the particles have a permanent electric dipole. Indeed, since the pioneering work of Peterlin and Stuart [46], it was successfully used to answer similar questions in colloidal dispersions of various kinds of nanoparticles such as clays [47][48][49][50][51], mineral nanorods [52], viruses [53], protein fibrils [54], macromolecules [55], and mixtures of rod-like and spherical colloids [56]. Recently, this technique has also been applied to investigate the field-induced alignment of CdSe nanorods [57] or the orientation of transition metal dichalcogenide nanodiscs.…”

Section: Introductionmentioning

confidence: 99%

Probing permanent dipoles in CdSe nanoplatelets with transient electric birefringence

2020

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Zinc-blende CdSe semiconducting nanoplatelets (NPL) show outstanding quantum confinement properties thanks to their small, atomically-controlled, thickness. For example, they display extremely sharp absorption peaks and ultra-fast recombination rates that make them very interesting objects for optoelectronic applications. However, the presence of a ground-state electric dipole for these nanoparticles has not yet been investigated. We therefore used transient electric birefringence (TEB) to probe the electric dipole of 5-monolayer thick zinc-blende CdSe NPL with a parallelepipedic shape. We studied a dilute dispersion of isolated NPL coated with branched ligands and we measured, as a function of time, the birefringence induced by DC and AC field pulses. The electrooptic behavior proves the presence of a large dipolar moment (> 245 D) oriented along the length of the platelets. We then induced the slow face-to-face stacking of the NPL by adding oleic acid. In these stacks, the in-plane dipole components of consecutive NPL cancel whereas their normal components add. Moreover, interestingly, the excess polarizability tensor of the NPL stacks gives rise to an electro-optic contribution opposite to that of the electric dipole. By monitoring the TEB signal of the slowly-growing stacks over up to a year, we extracted the evolution of their average length with time and we showed that their electro-optic response can be explained by the presence of a 80 D dipolar component parallel to their normal. In spite of the43m space group of bulk zinc-blende CdSe, these NPL thus bear an important ground-state dipole whose magnitude per unit volume is twice that found for wurtzite CdSe nanorods. We discuss the possible origin of this electric dipole, its consequences for the optical properties of these nanoparticles, and how it could explain their strong stacking propensity that severely hampers their colloidal stability.

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“…Moreover, dispersions of nanorods in a solvent usually show a strong response to the application of an alternating electric field. [13][14][15][16] In the nematic phase, the director aligns along or perpendicular to the electric field direction (depending on dielectric anisotropy), whereas, in the isotropic phase at a lower concentration, the electric field induces the orientational order of the nanorods. [11] In this article, we demonstrate the electric switching and polarization dependent luminescence of nematically ordered suspensions of upconversion nanorods in an isotropic medium.…”

Section: Introductionmentioning

confidence: 99%

Liquid Crystalline Order and Electric Switching of Upconversion Luminescence in Colloidal Nanorod Suspensions

Park

Mundoor

Fleury

et al. 2019

Advanced Optical Materials

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We study the polarization dependent photon upconversion luminescence properties of a large-scale orientationally ordered soft matter system formed by colloidal nanorods dispersed in an isotropic solvent. The electrostatically charged photon-upconverting nanorods form an isotropic dispersion at low concentrations, whereas orientational order and a nematic phase emerge at high concentrations. When an alternating electric field is applied, particles align in the direction of the electric field in both nematic and isotropic phases, though the nature of this electric switching is different in these two phases. Owing to the long-range orientational order in the nematic phase, the upconversion luminescence from the particles is polarized without an external field. Polarization dependence of these properties can also be electrically induced in an isotropic phase of the colloidal nanorods. Further, we explore the dynamics of switching of photon upconversion luminescence in both nematic and isotropic dispersions and discuss their potential technological uses.

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Electric field induced birefringence in non-aqueous dispersions of mineral nanorods

Cited by 13 publications

References 38 publications

Measuring the order parameter of vertically aligned nanorod assemblies

Measuring the order parameter of vertically aligned nanorod assemblies

Probing permanent dipoles in CdSe nanoplatelets with transient electric birefringence

Liquid Crystalline Order and Electric Switching of Upconversion Luminescence in Colloidal Nanorod Suspensions

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