Electric field induced orientational order of gold nanorods in dilute organic suspensions

Fontana, Jake; Costa, G.; Pereira, J.A.M.; Naciri, Jawad; Ratna, Banahalli R.; Palffy‐Muhoray, Peter; Carvalho, Isabel C. S.

doi:10.1063/1.4942969

Cited by 38 publications

(52 citation statements)

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“…Furthermore, while the exact mechanism is not yet clear, we believe viscosity also affects the rotational dynamics of the rods and the degree of nanorod alignment at equilibrium. More specifically, the viscosity of toluene reported in the literature is smaller than that of water, enabling the orientations of gold nanorods to be readily controlled by an external field [18,19].…”

Section: A Solvent-dependent Nonlinear Responsementioning

confidence: 99%

“…The underlying mechanism for this phenomenon is not quite clear, though, and we believe it may be related to interactions between the soliton beam and the probe beam. In any case, it is with no doubt that nanorods can be aligned by high electric fields [18][19][20], so the proposed scheme in Fig. 5(b) and associated anisotropic optical properties should be achievable with intense optical beams under appropriate conditions.…”

Section: E Soliton-mediated Anisotropic Optical Propertymentioning

confidence: 99%

“…The collective alignment of a large quantity of gold nanorods in a liquid environment may lead to macroscopic anisotropic optical response and can find applications in information processing and display technologies. While ordering of an ensemble of rods has been demonstrated with techniques including applying electric fields [15][16][17][18][19][20], self-assembly based fabrication [21][22][23], the stretched-film method [24][25][26], and the electrospinning technique [27,28], so far only manipulation of individual plasmonic nanorods was demonstrated experimentally with optical traps [29][30][31][32][33][34]. Recently, we attempted to achieve orientational ordering of gold nanorods inside an optical soliton channel established by pumping a colloidal suspension of gold nanorods with a 532 nm laser beam [35].…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we study optical nonlinearity in suspensions of gold nanorods and explore the effect of the solvent environment (aqueous versus organic) on soliton formation. Toluene is chosen as the organic solvent here, motivated by previous reports of obtaining good alignment of gold nanorods in toluene by applying an electrical field [18,19]. The threshold power for soliton formation for both suspensions is measured as a function of wavelength.…”

Section: Introductionmentioning

confidence: 99%

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Plasmonic resonant nonlinearity and synthetic optical properties in gold nanorod suspensions

Alvaro

Xiang

et al. 2018

Photon. Res.

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We experimentally demonstrate self-trapping of light, as a result of plasmonic resonant optical nonlinearity, in both aqueous and organic (toluene) suspensions of gold nanorods. The threshold power for soliton formation is greatly reduced in toluene as opposed to aqueous suspensions. It is well known that the optical gradient forces are optimized at off-resonance wavelengths at which suspended particles typically exhibit a strong positive (or negative) polarizability. However, surprisingly, as we tune the wavelength of the optical beam from a continuous-wave (CW) laser, we find that the threshold power is reduced by more than threefold at the plasmonic resonance frequency. By analyzing the optical forces and torque acting on the nanorods, we show theoretically that it is possible to align the nanorods inside a soliton waveguide channel into orthogonal orientations by using merely two different laser wavelengths. We perform a series of experiments to examine the transmission of the soliton-forming beam itself, as well as the polarization transmission spectrum of a low-power probe beam guided along the soliton channel. It is found that the expected synthetic anisotropic properties are too subtle to be clearly observed, in large part due to Brownian motion of the solvent molecules and a limited ordering region where the optical field from the self-trapped beam is strong enough to overcome thermodynamic fluctuations. The ability to achieve tunable nonlinearity and nanorod orientations in colloidal nanosuspensions with low-power CW laser beams may lead to interesting applications in all-optical switching and transparent display technologies.

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Section: A Solvent-dependent Nonlinear Responsementioning

confidence: 99%

Section: E Soliton-mediated Anisotropic Optical Propertymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plasmonic resonant nonlinearity and synthetic optical properties in gold nanorod suspensions

Alvaro

Xiang

et al. 2018

Photon. Res.

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“…4 A key advantage of plasmonic nanorods is that the polarizibility of a single nanorod in a dilute suspension is adequately large to couple to an external electric field, enabling alignment and the ability to tune the optical properties at visible and near infrared wavelengths.…”

Section: 2mentioning

confidence: 99%

Digital electric field induced switching of plasmonic nanorods using an electro-optic fluid fiber

Etcheverry

Araujo

Carvalho

et al. 2017

Applied Physics Letters

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We demonstrate the digital electric field induced switching of plasmonic nanorods between "1" and "0" orthogonal aligned states using an electro-optic fluid fiber component. We show by digitally switching the nanorods, that thermal rotational diffusion of the nanorods can be circumvented, demonstrating an approach to achieve submicrosecond switching times. We also show, from an initial unaligned state, that the nanorods can be aligned into the applied electric field direction in 110 nanoseconds. The high-speed digital switching of plasmonic nanorods integrated into an all-fiber optical component may provide opportunities for remote sensing and signaling applications.In general, the permanent or induced dipole moment and resulting polarizability of a molecule is too small to couple to external electric fields to overcome disordering thermal forces, preventing alignment. If anisotropic molecules are condensed into a liquid crystal phase, then the additional van der Waal forces from the nearneighbor interactions increases the polarizability to enable alignment of the molecules and control the optical properties. The electric field induced alignment of anisotropic molecules in liquid crystal phases has enabled disruptive technologies such as smart phones and flat screen displays. 1,2The switching time of these materials depends on the sum of their on-and off -times. The on-time needed to align the molecules into the direction of the applied electric field is predominately set by the magnitude of the field applied, τ on ≈ γ/εE 2 , where γ is the viscosity, ε is the dielectric permittivity and E is the electric field. The off -time is related to the thermal rotational diffusion of the liquid crystal molecules and typically is the limiting factor to determine the overall switching time. In the case of liquid crystals, the near-neighbor interactions create strong electrohydrodynamic coupling, leading to a slow characteristic off -time, τ of f ≈ γd 2 /K ≈ ms, where d is the cell thickness and K is the elastic constant of the liquid crystal. This well-known limitation has constrained potential electro-optic applications for decades.A recent elegant approach avoided re-alignment of the molecules altogether by rapidly electrically inducing a change in the refractive index of the molecules in a liquid crystal phase.3 The response time of this system was 10 s of nanoseconds, yet the change in the optical properties was small and cannot be maintained for long times before a) Electronic mail: walter.margulis@ri.se b) Electronic mail: jake.fontana@nrl.navy.mil the usual electric field induced alignment of the molecules occurs.The electric field induced alignment of plasmonic nanorods is a paradigm to anisotropic molecules in liquid crystal phases.4 A key advantage of plasmonic nanorods is that the polarizibility of a single nanorod in a dilute suspension is adequately large to couple to an external electric field, enabling alignment and the ability to tune the optical properties at visible and near infrared wavelengths.4,5 A sig...

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A Lyotropic Liquid‐Crystal‐Based Assembly Avenue toward Highly Oriented Vanadium Pentoxide/Graphene Films for Flexible Energy Storage

Liu

Tang

Wang

et al. 2017

Adv Funct Materials

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1606269(1 of 7) materials and their practical applications, which require functional macroscopic architectures. [3] To meet the application necessities, various strategies have been established to achieve fine control over the arrangement of 2D materials in the bulk or in thin films, such as vacuum filtration deposition, [4] field-induced alignment, [5] and freeze-casting. [1,6] Among these methods, the formation of lyotropic liquid crystals (LCs) is one of the most attractive protocols because it is a mild, solution processible means to obtain oriented colloids of nanosheets, which can be further fabricated into ordered bulk structures with optimal performances in optic/electronic devices. [7,8] As exemplified by graphene, graphene oxide (GO), and other 2D materials, when the anisotropic nanosheets are dispersed in a liquid medium at a proper concentration, the thermodynamically controlled LC phase transition will occur spontaneously without the assistance of any special devices. [9][10][11] Generally, these LCs are in nematic phases or isotropic-nematic phases, [12] which have no positional order, but do possess a certain degree of orientation. The driving forces for such phase behavior include the high aspect ratio of 2D materials, and the attractive interactions (van der Waals forces, Coulombic interactions between opposite charges, or depletion interactions) and repulsive interactions (steric hindrance, Coulombic interactions between same charges) between them. [13] The self-organization of 2D materials in LC phases can bring enhanced performances on account of the cumulative effect of individual components. Nevertheless, previous research has been mainly focused on LCs of a single 2D component. [14] We envision that the phase transition process is feasible with more than one type of nanosheet, as long as they have good compatibility in solution. More importantly, the resultant lyotropic LCs can be utilized in constructing hierarchical composites with highly oriented architectures. However, the application of this strategy in the fabrication of 2D materials based composites is still rare.Herein, we demonstrate, for the first time, the fabrication of a composite film of vanadium pentoxide (V 2 O 5 ) nanobelts and GO sheets, with well-ordered layer structures (VrGO) from their lyotropic LCs in aqueous dispersion. The mixed suspension of A novel lyotropic liquid-crystal (LC) based assembly strategy is developed for the first time, to fabricate composite films of vanadium pentoxide (V 2 O 5 ) nanobelts and graphene oxide (GO) sheets, with highly oriented layered structures. It is found that similar lamellar LC phases can be simply established by V 2 O 5 nanobelts alone or by a mixture of V 2 O 5 nanobelts and GO nanosheets in their aqueous dispersions. More importantly, the LC phases can be retained with any proportion of V 2 O 5 nanobelts and GO, which allows facile optimization of the ratio of each component in the resulting films. Named VrGO, composite films manifest high electrical conductivity, good mec...

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Electric field induced orientational order of gold nanorods in dilute organic suspensions

Cited by 38 publications

References 11 publications

Plasmonic resonant nonlinearity and synthetic optical properties in gold nanorod suspensions

Plasmonic resonant nonlinearity and synthetic optical properties in gold nanorod suspensions

Digital electric field induced switching of plasmonic nanorods using an electro-optic fluid fiber

A Lyotropic Liquid‐Crystal‐Based Assembly Avenue toward Highly Oriented Vanadium Pentoxide/Graphene Films for Flexible Energy Storage

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