Improved Synthetic Methods for Patchy Particles
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Patchy particles are patterned particles with at least one well-defined patch that can have highly directional and strongly anisotropic interactions with other particles or surfaces. Multiple theoretical studies point to interesting self-assembly of these particles into superstructures and, as a result, a multitude of possible applications. However, reliable synthetic methods for patchy particles, especially at the sub-micron level, are still a challenge and an active area of research. This work presents a novel synthesis route for making patchy particles at the sub-micron level that involves the use of capillary condensation. Colloidal silica particles of various sizes were synthesized and ordered into closely-packed arrays via evaporative self-assembly. Various chemical agents were capillary condensed into the voids of this assembly which, due to the face-centered cubic structure of the crystallized colloidal silica, produced distinct \patches" on the particle surface. The patches on these particles were successfully functionalized with gold nanoparticles. This method was shown to provide control over the patch size by modifying the silica particle radius, which thermodynamically changes the amount of capillary condensation. The patchy nature of the resultant particles was confirmed using infrared spectroscopy, scanning electron and optical microscopies, energy dispersive x-ray analysis and zeta potential measurements.