Designing Zwitterionic SiO2NH2-Au Particles with Tunable Patchiness using Wrinkles

A facile template-based approach toward zwitterionic SiO2NH2-Au patchy particles is presented. Therefore, wrinkle templates prepared by stress release in a bilayer system comprised of an elastic PDMS fundament and a thin SiOx top layer are used. After aligning positively charged, amine-functionalized silica particles in wrinkle grooves, their surfaces are partially modified with negatively charged gold nanoparticles in an electrostatic adsorption step. Patchiness is precisely controlled by the degree of immersion of the initial particles into wrinkles of varying dimensions. By ultrasonication or wetting with a water droplet, patchy particles are easily released from the substrate-yielding particles with two oppositely charged hemispheres. Interfacial tension measurements prove the surface activity of the SiO2NH2-Au particles in an oil/water system and are explained in the view of the Janus-type surface charges of the particles and the charge of the oil/water interface.