Templating Interfacial Nanoparticle Assemblies via in Situ Techniques

Abstract

In situ surface modification of nanoparticles has a rich industrial history, but in recent years, it has also received increased attention in the field of directed selfassembly. In situ techniques rely on components within a Pickering emulsion system, such as amphiphiles that act as hydrophobizers or ionic species that screen charges, to drive the interfacial assembly of particles. Instead of stepwise procedures to chemically tune the particle wettability, in situ methods use elements already present within the system to alter the nanoparticle interfacial behavior, often depending on Coulombic interactions to simplify operations. The surface modifications are not contingent on specific chemical reactions, which further enables a multitude of possible nanoparticles to be used within a given system. In recent studies, in situ methods have been combined with external means of shaping the interface to produce materials with high interfacial areas and complex geometries. These systems have facilely tunable properties, enabling their use in an extensive array of applications. In this feature article, in honor of the late Prof. Helmuth Moḧwald, we review how in situ techniques have influenced the development of soft, advanced materials, covering the fundamental interfacial phenomena with an outlook on materials science.

Stabilizing liquid drops in nonequilibrium shapes by the interfacial crosslinking of nanoparticles

“…However, in the mixture, HTA + renders the SNP surface active, as it adsorbs electrostatically on silica, covering the surface partially with hexyl-chains in situ. 19 This is confirmed by measurements of the contact angles of sessile water droplets on flat HTA + modified silica surfaces, which show decreasing hydrophilicity of the surface. 20 The HTA + adsorption on the SNP increases their interfacial attachment energy, given by DG attach = ÀpÁr 2 Ág ow (1 À cos y) 2 , with r the particle radius, g ow the water/oil interfacial tension and y the contact angle.…”

Surface Properties of Colloidal Particles Affect Colloidal Self-Assembly in Evaporating Self-Lubricating Ternary Droplets

“…Nevertheless, the interaction of colloidal particles with the various interfaces is governed by multiple competing effects such as van der Waals, electrostatic (including image-charge effects), steric, capillary, and solvation interactions. 61 − 64 Further studies can address the role of these interactions in more detail.…”

Swelling Cholesteric Liquid Crystal Shells to Direct the Assembly of Particles at the Interface

“…Nanoparticles with appropriate surface functionalization adsorb at the CLC-water interface to create assemblies templated by the liquid crystal patterns [8,26]. We use 200 nm FluoSpheresfluorescent polystyrene particles with amine-functionalized surfaces-dispersed in solutions of the same SDS surfactant that induces homeotropic anchoring.…”