Measuring single-nanoparticle wetting properties by freeze-fracture shadow-casting cryo-scanning electron microscopy

Isa, Lucio; Lucas, Falk; Wepf, Roger; Reimhult, Erik

doi:10.1038/ncomms1441

Cited by 181 publications

(234 citation statements)

References 40 publications

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“…Passive probe particle tracking, atomic force microscopy (AFM), and freeze-fracture shadow-casting cryogenic scanning electron microscopy (FreSCa cryo-SEM) 29 concurrently show that nematic fibril domains form upon increase in interfacial density r. We follow the evolution of LC ordering in the absence of an external compressive force, as opposed to the majority of previous experimental works. The apparent flexibility of fibrils adsorbed at the interface changes as a function of alignment and crowding.…”

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Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

et al. 2013

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Two-dimensional alignment of shape-anisotropic colloids is ubiquitous in nature, ranging from interfacial virus assembly to amyloid plaque formation. The principles governing two-dimensional self-assembly have therefore long been studied, both theoretically and experimentally, leading, however, to diverging fundamental interpretations on the nature of the two-dimensional isotropic-nematic phase transition. Here we employ single-molecule atomic force microscopy, cryogenic scanning electron microscopy and passive probe particle tracking to study the adsorption and liquid crystalline ordering of semiflexible b-lactoglobulin fibrils at liquid interfaces. Fibrillar rigidity changes on increasing interfacial density, with a maximum caused by alignment and a subsequent decrease stemming from crowding and domain bending. Coexistence of nematic and isotropic regions is resolved and quantified by a length scale-dependent order parameter S 2D (d). The nematic surface fraction increases with interfacial fibril density, but depends, for a fixed interfacial density, on the initial bulk concentration, ascribing the observed two-dimensional isotropic-nematic coexistence to non-equilibrium phenomena.

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Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

et al. 2013

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“…More recently, freezefracture shadow-casting cryo SEM has been performed with single-particle resolution of these assemblies. 40 However, most of these techniques are time consuming and require specialized equipment. There exists a need for a fast, in situ technique that would probe, with nanometer resolution, the structural characteristics of these films.…”

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Plasmonic Ruler at the Liquid–Liquid Interface

et al. 2012

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We report on a simple, fast, and inexpensive method to study adsorption and desorption of metallic nanoparticles at a liquid/liquid interface. These interfaces provide an ideal platform for the formation of two-dimensional monolayers of nanoparticles, as they form spontaneously, cannot be broken, and are defectcorrecting, acting as 2D 'nanoparticle traps'. Such two-dimensional self-assembled nanoparticle arrays have a vast range of potential applications in displays, catalysis, plasmonic rulers, optoelectronics, sensors and detectors. Here, we show that 16 nm diameter gold nanoparticles can be controllably adsorbed to a water/1,2-dichloroethane interface, and we can direct the average inter-particle spacing at the interface over the range 6-35 nm. The particle density and average inter-particle spacing are experimentally assessed by measuring the optical plasmonic response of the nanoparticles in the bulk and at the interface, and by comparing the experimental data with existing theoretical results.Keywords: liquid-liquid interface, Plasmonic Ruler, Nanoparticles, Self Assembly, Centrifugation. Nanoparticle (NP) adsorption at liquid-liquid interfaces (LLI) is a well established phenomenon that was first reported independently more than a century ago by Ramsden and Pickering. 1, 2 More recently, plasmonic NPs at LLIs have been reported to possess novel "metal liquid like" properties 3 that have sparked a renewed interest. Driven by the growing need for cheap, fast and reproducible bottom-up assembly for nanotechnological applications, the unique optical, 4 magnetic, 5 electrical 6 and chemical 7 properties of such films has attracted intensive research in a rapidly growing field.NP assemblies at LLIs hold great promise in diverse fields ranging from electrovariable optics 8 to templates for hierarchical self assembly, 9 and plasmonic rulers. 10 One of the main benefits of localising NPs at a LLI for these applications is the aforementioned self-assembly. 11 Currently, most technological applications of nanoassemblies are based around solid-state fabrication. Although the control that the solid interface offers is unparalleled, it does have several drawbacks when compared to a LLI. One such drawback is topological defects -these can be introduced either during or post-manufacturing and are extremely difficult to correct. In fact it is often easier to fabricate a new device rather than attempting to repair defects. Conversely, a LLI system has the ability to self-correct without any external manipulation. 12 An additional drawback of a solid state system becomes clear when introducing the exciting concept of a plasmonic ruler. [13][14][15] The coupling between excitations of localized plasmons in NPs can allow for precise spatial information. This concept has been demonstrated between 2D arrays, 10 particle dimers 14 at solid interfaces and tethered NPs in bulk solution. 16 It has even been recently demonstrated to provide 3-dimensional structural information. 17 The use of plasmonic particles at the LLI sh...

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“…[10][11][12][13] Many experimental studies have been devoted to investigate the factors controlling the behavior of nanoparticles at an interface, including their size, surface morphology, shape, materials polarizability, and coatings. [14][15][16][17][18] Some of these factors influence the location and orientation of individual nanoparticles; others influence their mutual interactions and assembly geometry. However, in experiments these factors are usually intertwined to yield collective effects and it is difficult to single out the effect of each factor alone.…”

Section: Introductionmentioning

confidence: 99%

Structure and diffusion of nanoparticle monolayers floating at liquid/vapor interfaces: A molecular dynamics study

Cheng

Grest

2012

The Journal of Chemical Physics

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Large-scale molecular dynamics simulations are used to simulate a layer of nanoparticles floating on the surface of a liquid. Both a low viscosity liquid, represented by Lennard-Jones monomers, and a high viscosity liquid, represented by linear homopolymers, are studied. The organization and diffusion of the nanoparticles are analyzed as the nanoparticle density and the contact angle between the nanoparticles and liquid are varied. When the interaction between the nanoparticles and liquid is reduced the contact angle increases and the nanoparticles ride higher on the liquid surface, which enables them to diffuse faster. In this case the short-range order is also reduced as seen in the pair correlation function. For the polymeric liquids, the out-of-layer fluctuation is suppressed and the short-range order is slightly enhanced. However, the diffusion becomes much slower and the mean square displacement even shows sub-linear time dependence at large times. The relation between diffusion coefficient and viscosity is found to deviate from that in bulk diffusion. Results are compared to simulations of the identical nanoparticles in 2-dimensions.

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Measuring single-nanoparticle wetting properties by freeze-fracture shadow-casting cryo-scanning electron microscopy

Cited by 181 publications

References 40 publications

Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

Non-equilibrium nature of two-dimensional isotropic and nematic coexistence in amyloid fibrils at liquid interfaces

Plasmonic Ruler at the Liquid–Liquid Interface

Structure and diffusion of nanoparticle monolayers floating at liquid/vapor interfaces: A molecular dynamics study

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