Janus Particles: Synthesis, Self-Assembly, Physical Properties, and Applications

Walther, Andreas; Müller, Axel H. E.

doi:10.1021/cr300089t

Cited by 1,661 publications

(1,434 citation statements)

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“…Like Janus particles of a single metal covered with different surface groups, these bimetallic Janus particles are expected to have very interesting self-assembly for formation of superstructures, which could not be formed from homogeneous particles. 23,24 As nanoparticles themselves exhibit very interesting self-assembly behavior, 25,26 The idea behind hierarchical assembly is to use nanoparticles and other building blocks to produce materials with tailored properties. As the self-assembly is typically driven by electrostatic, van der Waals, hydrophobic, and other interactions at the nanoscale, 28 the formation of electrostatic dipoles due to contact charging gives one more tool to induce this self-assembly.…”

Section: Introductionmentioning

confidence: 99%

Charge distribution and Fermi level in bimetallic nanoparticles

Holmberg

Laasonen

Peljo

2016

Phys. Chem. Chem. Phys.

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Upon metal-metal contact, a transfer of electrons will occur between the metals until the Fermi levels in both phases are equal, resulting in a net charge difference across the metal-metal interface. Here, we have examined this contact electrification in bimetallic model systems composed of mixed Au-Ag nanoparticles containing ca. 600 atoms using density functional theory calculations. We present a new model to explain this charge transfer by considering the bimetallic system as a nanocapacitor with a potential difference equal to the work function difference, and with most of the transferred charge located directly at the contact interface. Identical results were obtained by considering surface contacts as well as by employing a continuum model, confirming that this model is general and can be applied to any multimetallic structure regardless of geometry or size (going from nano-to macroscale). Furthermore, the equilibrium Fermi level was found to be strongly dependent on the surface coverage of different metals, enabling the construction of scaling relations. We believe that the charge transfer due to Fermi level equilibration has a profound effect on the catalytic, electrocatalytic and other properties of bimetallic particles. Additionally, bimetallic nanoparticles are expected to have very interesting self-assembly for large superstructures due to the surface charge anisotropy between the two metals.

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Section: Introductionmentioning

confidence: 99%

Charge distribution and Fermi level in bimetallic nanoparticles

Holmberg

Laasonen

Peljo

2016

Phys. Chem. Chem. Phys.

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“…In fact, these structures could consist of two different organic polymeric materials, two inorganic materials, or one organic and one inorganic material [30,31]. This variety of combinations enables the application of these materials in multitude fields, such as in the upgrade of new and more powerful sensors, in electronics, catalysis or in the development of new medical devices to facilitate the control of drug delivery [30][31][32]. Here, we propose the independent functionalization of one face of free-standing SWCNT film electrode.…”

Section: Introductionmentioning

confidence: 99%

Spectroelectrochemistry at free-standing carbon nanotubes electrodes

Ibáñez

Garoz‐Ruiz

Plana

et al. 2016

Electrochimica Acta

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms 1. ISE member. Abstract.A versatile and low-cost methodology for fabricating free-standing carbon nanotubes (CNT) electrodes for electrochemical and spectroelectrochemical applications is described. The uniformity, flexibility and resistance to bending of these films make them one of the most interesting membranes in a wide range of applications. CNT electrodes were characterized by Raman spectroscopy and scanning electron microscopy and their electrochemical performance was assessed employing various redox species such as ferrocenemethanol, hexacyanoferrate (II) and dopamine. Free-standing single-walled CNT electrodes exhibit good conductivity and transparency to UV-Vis radiation, making them suitable as optically transparent electrodes. This is exemplified by monitoring, using UV-Vis absorption spectroelectrochemistry, the electrodeposition of gold nanoparticles (AuNPs) on one face of the free-standing CNT electrodes, while the other face remained unmodified.

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“…Structuring a spherical particle azimuthally-rather than radially-has traditionally been a more demanding fabrication task, and to date is limited to "Janus" structures in polymers in which two materials are compartmentalized in two hemispheres or only the surface is treated (47)(48)(49). Although symmetry principles may potentially enable higher-order discrete rotational symmetry through directed template growth, arbitrary control over the azimuthal structure of a spherical particle displaying no symmetry is out of reach of current approaches.…”

Section: Resultsmentioning

confidence: 99%

Digital design of multimaterial photonic particles

Tao

Kaufman

Shabahang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Scattering of light from dielectric particles whose size is on the order of an optical wavelength underlies a plethora of visual phenomena in nature and is a foundation for optical coatings and paints. Tailoring the internal nanoscale geometry of such "photonic particles" allows tuning their optical scattering characteristics beyond those afforded by their constitutive materials-however, flexible yet scalable processing approaches to produce such particles are lacking. Here, we show that a thermally induced in-fiber fluid instability permits the "digital design" of multimaterial photonic particles: the precise allocation of high refractive-index contrast materials at independently addressable radial and azimuthal coordinates within its 3D architecture. Exploiting this unique capability in all-dielectric systems, we tune the scattering cross-section of equisized particles via radial structuring and induce polarization-sensitive scattering from spherical particles with broken internal rotational symmetry. The scalability of this fabrication strategy promises a generation of optical coatings in which sophisticated functionality is realized at the level of the individual particles.multimaterial fibers | particles | optical scattering | fluid instabilities T he prospect of exercising complete control over the internal 3D structure of multimaterial microparticles and nanoparticles produced in a scalable fashion has profound implications for scientific disciplines ranging from photonics (1, 2) to biomedicine (3-5), and for a multitude of industrial applications, such as cosmetics, sunscreen lotions, optical coatings, and paints (6-8). For example, most paints are emulsions containing dielectric "photonic particles" designed to optimize optical scattering through judicious selection of size-typically on the order of an optical wavelengthand refractive index (9). Further tailoring their scattering characteristics requires tuning an internal high refractive-index contrast nanoscale architecture, which remains an outstanding fabrication challenge despite recent progress (10-14). Indeed, the process kinetics in bottom-up and top-down particle fabrication strategies impose fundamental constraints on the extent of structural control and the magnitude of refractive-index contrast. To date, there is no viable approach for what may be termed "digital design" of a photonic particle: the precise placement of disparate materials compartmentalized at independently addressable coordinates within a particle at the scale of an optical wavelength. Such structural control is envisioned to introduce entirely new optical functionalities that exploit the particle's resonances (15), such as the elimination of backscattering and increasing the directionality of optical scattering (16)(17)(18)(19)(20). Nevertheless, mapping out the phase function of a single isolated photonic particle-to verify its functionality without ensemble averaging-has proven so far to be prohibitively difficult, leading to measurements being carried out on scaled-up pa...

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Janus Particles: Synthesis, Self-Assembly, Physical Properties, and Applications

Cited by 1,661 publications

References 396 publications

Charge distribution and Fermi level in bimetallic nanoparticles

Charge distribution and Fermi level in bimetallic nanoparticles

Spectroelectrochemistry at free-standing carbon nanotubes electrodes

Digital design of multimaterial photonic particles

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