Control over Colloidal Aggregation in Monolayers of Latex Particles at the Oil−Water Interface

Reynaert, Sven; Moldenaers, Paula; Vermant, Jan

doi:10.1021/la060052n

Cited by 167 publications

(260 citation statements)

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“…As the capillary forces acting on the particles is proportional to the surface-or interface tension, the addition of surfactants significantly lowers the magnitude of capillary attraction. [202] The reduced attraction increases the time that is available for the colloids to find their minimum free energy position and thus, further increases the order of the monolayer. Furthermore, the pH value of the water subphase was used to tune the assembly process.…”

Section: Resultsmentioning

confidence: 99%

Surface Patterning with Colloidal Monolayers

Vogel

2012

Springer Theses

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This thesis focuses on the controlled assembly of monodisperse polymer colloids into ordered two-dimensional arrangements. These assemblies, commonly referred to as colloidal monolayers, are subsequently used as masks for the generation of arrays of complex metal nanostructures on solid substrates.The motivation of the research presented here is twofold. First, monolayer crystallization methods were developed to simplify the assembly of colloids and to produce more complex arrangements of colloids in a precise way. Second, various approaches to colloidal lithography are designed with the aim to include novel features or functions to arrays of metal nanostructures.The air/water interface was exploited for the crystallization of colloidal monolayer architectures as it combines a two-dimensional confinement with a high lateral mobility of the colloids that is beneficial for the creation of high long range order. A direct assembly of colloids is presented that provides a cheap, fast and conceptually simple methodology for the preparation of ordered colloidal monolayers. The produced two-dimensional crystals can be transformed into nonclose-packed architectures by a plasma-induced size reduction step, thus providing valuable masks for more sophisticated lithographic processes. Finally, the controlled co-assembly of binary colloidal crystals with defined stoichiometries on a Langmuir trough is introduced and characterized with respect to accessible configurations and size ratios.Several approaches to lithography are presented that aim at introducing different features to colloidal lithography. First, using metal-complex containing latex particles, the synthesis of which is described as well, symmetric arrays of metal nanoparticles can be created by controlled combustion of the organic material of the colloids. The process does not feature an inherent limit in nanoparticle size and is able to produce complex materials as will be demonstrated for FePt alloy particles. Precise control over both size and spacing of the particle array is presented.Second, two lithographic processes are introduced to create sophisticated nanoparticle dimer units consisting of two crescent shaped nanostructures in close proximity; essentially by using a single colloid as mask to generate two structures simultaneously. Strong coupling processes of the parental plasmon resonances of the two objects are observed that are accompanied by high near-field enhancements. A plasmon hybridization model is elaborated to explain all polarization dependent shifts of the resonance positions. Last, a technique to produce laterally patterned, ultra-flat substrates without surface topographies by embedding gold nanoparticles in a silicon dioxide matrix is applied to construct robust and re-usable sensing architectures and to introduce an approach for the nanoscale patterning of solid supported lipid bilayer membranes.

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Section: Resultsmentioning

confidence: 99%

Surface Patterning with Colloidal Monolayers

Vogel

2012

Springer Theses

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“…The results (from ref. [14]) are given in figure 2. The contact angle increases as SDS is added, i.e.…”

Section: Methodsmentioning

confidence: 99%

“…A first illustration hereof is the remarkable stability of two-dimensional colloidal crystals when the ionic strength of the aqueous phase is increased [12,21,14].…”

Section: Introductionmentioning

confidence: 99%

“…For example, when particles are first spread onto a virgin interface, and salt is added to the aqueous subphase slowly after that, the aggregation proceeds as expected, after the long induction process mentioned. Yet, particles spread onto an aqueous subphase already containing the salt can result in a monolayer where crystalline patches and dense aggregates coexist [14]. Finally, probably the most remarkable illustration of the complexity of the interaction forces is the occurrence of so-called mesoscale structures.…”

Section: Introductionmentioning

confidence: 99%

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Direct Measurements of the Effects of Salt and Surfactant on Interaction Forces between Colloidal Particles at Water−Oil Interfaces

Park¹,

Pantina²,

Furst³

et al. 2008

Langmuir

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192

270

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The forces between colloidal particles at a decane-water interface, in the presence of low concentrations of a monovalent salt (NaCl) and of the surfactant sodium dodecylsulfate (SDS) in the aqueous subphase, have been studied using laser tweezers. In the absence of electrolyte and surfactant, particle interactions exhibit a long-range repulsion, yet the variation of the interaction for different particle pairs is found to be considerable. Averaging over several particle pairs was hence found to be necessary to obtain reliable assessment of the effects of salt and surfactant. It has previously been suggested that the repulsion is consistent with electrostatic interactions between a small number of dissociated charges in the oil phase, leading to a decay with distance to the power -4 and an absence of any effect of electrolyte concentration. However, the present work demonstrates that increasing the electrolyte concentration does yield, on average, a reduction of the magnitude of the interaction force with electrolyte concentration. This implies that charges on the water side also contribute significantly to the electrostatic interactions. An increase in the concentration of SDS leads to a similar decrease of the interaction force. Moreover the repulsion at fixed SDS concentrations decreases over longer times. Finally, measurements of threebody interactions provide insight into the anisotropic nature of the interactions. The unique time-dependent and anisotropic interactions between particles at the oil-water interface allow tailoring of the aggregation kinetics and structure of the suspension structure.2

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“…Thus, water/oil interfaces have been used for growth of 2D colloidal crystals [37,38], while transfer of the resulting 2D colloidal crystals to solid substrates remains problematic. Besides water/air interfaces, air/water/air interfaces have also been utilized for colloidal crystallization.…”

Section: Colloidal Crystallization At Interfacementioning

confidence: 99%