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The ability to manipulate the absorption, scattering, or reflectivity of light using synthetic materials has inspired innovations in nano‐ and micro‐materials for applications ranging from geoengineering to display optics. Asymmetric materials, like Janus particles, offer one solution to meet the needs of such technologies, as composition and geometry can be optimized to maximize directional optical properties in response to magnetic and/or electric fields, light, or electrostatic charge. In this work, a gram‐scale synthesis is applied to generate Janus matchstick particles comprising a gold head with a silica rod. Conditions are explored and optimized to elicit rotation of these matchstick particles under an alternating current (AC) electric field with varying field strength and frequency to maximize particle alignment. While only modest changes in transmission (≈8%) are observed over the visible spectral region with a bare silica rod, the application of an absorbing element increased transmission changes up to ≈23% demonstrating their utility as color‐changing materials. Experimental results are supported by theory and computation and highlight an important first step in activating directional optical effects in these materials which can be optimized for future adaptive technologies. [ABSTRACT FROM AUTHOR]

We present a gram-scale synthesis of metallodielectric Janus matchsticks, which feature a gold-coated silica sphere and a silica rod. SiO2 Janus matchsticks are synthesized in one batch by growing amine-functionalized SiO2 spheres at the end of SiO2 rods. Gold deposition on the spheres produces Au–SiO2 Janus matchsticks with an aspect ratio controlled by the rod length. The metallodielectric Janus matchsticks, produced by scalable colloidal synthesis, hold great potential as functional colloidal materials. [ABSTRACT FROM AUTHOR]