Non-equilibrium ionic assemblies of oppositely charged nanoparticles

Zhang, Rui; Jha, Prateek K.; Cruz, Mónica Olvera de la

doi:10.1039/c3sm27529a

Cited by 30 publications

(37 citation statements)

References 60 publications

(77 reference statements)

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“…Ions neighbouring each other can share coordinated water molecules and improve the hydration structure compared with a randomly adsorbed ion. Moreover, alternating positive (ions) and negative (water oxygen atoms) charges improves the stability of the structures as predicted by previous theoretical work 53 .…”

Section: Resultssupporting

confidence: 55%

Water-induced correlation between single ions imaged at the solid–liquid interface

2014

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When immersed into water, most solids develop a surface charge, which is neutralized by an accumulation of dissolved counterions at the interface. Although the density distribution of counterions perpendicular to the interface obeys well-established theories, little is known about counterions' lateral organization at the surface of the solid. Here we show, by using atomic force microscopy and computer simulations, that single hydrated metal ions can spontaneously form ordered structures at the surface of homogeneous solids in aqueous solutions. The structures are laterally stabilized only by water molecules with no need for specific interactions between the surface and the ions. The mechanism, studied here for several systems, is controlled by the hydration landscape of both the surface and the adsorbed ions. The existence of discrete ion domains could play an important role in interfacial phenomena such as charge transfer, crystal growth, nanoscale self-assembly and colloidal stability.

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Section: Resultssupporting

confidence: 55%

Water-induced correlation between single ions imaged at the solid–liquid interface

2014

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“…Note that simulations of oppositely charged particles interacting through static Yukawa potentials show the formation of fibers shorter than those in Fig. 2D at early times (17). The system shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…For pH 5, particles a and b have a charge of −0.5 and +0.5, respectively, and, as expected (17,18), they form square lattice aggregates. The symmetry of the system ensures that the pH range 5 < pH < 7 produces the same structures described for the range 3 < pH < 5, but with the a-type and b-type particles interchanged.…”

Section: Resultsmentioning

confidence: 99%

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Dissipative self-assembly of particles interacting through time-oscillatory potentials

Tagliazucchi¹,

Weiss²,

Szleifer

2014

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

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Dissipative self-assembly is the emergence of order within a system due to the continuous input of energy. This form of nonequilibrium self-organization allows the creation of structures that are inaccessible in equilibrium self-assembly. However, design strategies for dissipative self-assembly are limited by a lack of fundamental understanding of the process. This work proposes a novel route for dissipative self-assembly via the oscillation of interparticle potentials. It is demonstrated that in the limit of fast potential oscillations the structure of the system is exactly described by an effective potential that is the time average of the oscillatory potential. This effective potential depends on the shape of the oscillations and can lead to effective interactions that are physically inaccessible in equilibrium. As a proof of concept, Brownian dynamics simulations were performed on a binary mixture of particles coated by weak acids and weak bases under externally controlled oscillations of pH. Dissipative steady-state structures were formed when the period of the pH oscillations was smaller than the diffusional timescale of the particles, whereas disordered oscillating structures were observed for longer oscillation periods. Some of the dissipative structures (dimers, fibers, and honeycombs) cannot be obtained in equilibrium (fixed pH) simulations for the same system of particles. The transition from dissipative self-assembled structures for fast oscillations to disordered oscillating structures for slow oscillations is characterized by a maximum in the energy dissipated per oscillation cycle. The generality of the concept is demonstrated in a second system with oscillating particle sizes.issipative or dynamic self-assembly is the formation of order due to the continuous input of energy into the system and dissipation of energy by the system into the environment (1). If the input of energy is stopped, dissipative structures are destroyed as the system evolves toward equilibrium; therefore, these structures exist only far from equilibrium. Dissipative self-assembled structures are unique due to their ability to adapt to environmental changes. Consider, for example, a school of fish where each individual dynamically interacts with its neighbors and adjusts its position and velocity accordingly (2). Due to its dynamical nature, the school of fish responds as a whole when a predator threatens one of its individuals. This complex behavior is impossible for a static assembly. Nature excels in using dissipative structures to minimize wasted energy. For example, a swarm of bees can change its size and density to regulate its internal temperature, and a flock of Canada geese reduces energy dissipation due to aerodynamic drag by flying in a V-shaped formation (2).Synthetic dissipative assemblies are restricted to a small number of examples, such as magnetic spinners at the air-water interface (1), magnetic droplets on surperhydrophobic surfaces (3), lanes of colloidal particles under the influence of external fields (4...

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“…However, if the average sizes of oppositely charged particles are different, this can provide formation of not-well-defined crystals. 30 Changes in relative size can also affect the mechanism through the interplay between the electrostatic and van der Waals interactions, 31 and this will be the topic of further investigations.…”

Section: Resultsmentioning

confidence: 99%

Label-Free in Situ Optical Monitoring of the Adsorption of Oppositely Charged Metal Nanoparticles

et al. 2014

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ABSTRACT:The mechanism of alternating deposition of oppositely charged gold nanoparticles (AuNPs) was investigated by optical waveguide lightmode spectroscopy (OWLS). OWLS allows monitoring of the kinetics of layer-by-layer (LbL) adsorption of positively and negatively charged nanoparticles in real time without using any labels so that the dynamics of layer formation can be revealed. Positively charged NPs that are already deposited on a negatively charged glass substrate strongly facilitate the adsorption of the negatively charged particles. The morphology of the adsorbed layer was also investigated with atomic force microscopy (AFM). AFM revealed that the interaction between oppositely charged particles results in the formation of NP clusters with sizes varying between 100 and 6000 NPs. The cluster size distribution is found to be an exponentially decaying function, and we propose a simple theory to explain this finding.

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Non-equilibrium ionic assemblies of oppositely charged nanoparticles

Cited by 30 publications

References 60 publications

Water-induced correlation between single ions imaged at the solid–liquid interface

Water-induced correlation between single ions imaged at the solid–liquid interface

Dissipative self-assembly of particles interacting through time-oscillatory potentials

Label-Free in Situ Optical Monitoring of the Adsorption of Oppositely Charged Metal Nanoparticles

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