Fabrication and characterization of asymmetric Janus and ternary particles.

Asymmetric Janus and ternary silica particles with an average diameter of 450 nm were fabricated by sequentially arranged particle-embedding and surface-modification processes. Thermally induced embedding of particles into polymer-fiber substrates allowed for precise control of the degree of particle submergence and the subsequent chemical modification of the hemispherical exposed particle surfaces. In addition to Janus particles with the desired surface-functionality ratios of 1:2, 1:1, and 2:1, this unique fabrication approach was also used to produce complicated and well-defined heterogeneous materials, including bifunctionalized Janus and ternary particles. The bifunctionalized Janus particles were produced with two hemispherical surfaces alternately labeled with gold and iron oxide nanoparticles, which simultaneously enabled anisotropic surface-plasmon resonance and a magnetic response. Ternary particles were also constructed, yielding submicrometer spheres with functionalized equatorial belts. The surface distributions of functional components in these spherical materials were carefully examined for uniformities in particle embedding. Statistical analyses revealed that the functional components were distributed with a uniformity of over 80% for all of the asymmetric Janus and ternary particles.