Near‐Infrared Light‐Driven Zn/Au Janus Micromotors for Multiplex SERS Detection of Anticancer Drugs

ABSTRACT Janus Zn/Au micromotors (MMs) are fabricated by sputtering Au onto one hemisphere of Zn microparticles, resulting in spherical light‐responsive structures with dual photothermal propulsion and SERS detection capabilities. Zn/Au MMs exhibit efficient propulsion under near‐infrared (NIR) light, with motion driven through thermophoretic effects induced by local heating of the Au surface. The MMs are activated by CARS microscopy, enabling label‐free, real‐time trajectory tracking, with propulsion velocities increasing linearly with total laser power and remaining largely independent of the pump wavelength within the NIR range (780–900 nm) under dual‐wavelength excitation. A 30 nm Au coating provides the optimal balance between optical absorption and propulsion efficiency, while independent modulation of the pump and Stokes beams confirms that dual‐beam excitation is essential for sustained motion. Zn/Au MMs work perfectly as active SERS platforms for single and multiplex detection of the anticancer drugs methotrexate (MTX) and 6‐mercaptopurine (6‐MP). Their active motion enhances analyte exchange at the Au surface, reducing affinity‐driven saturation and competitive adsorption effects, which broadens the linear range and improves multiplex SERS detection. The integration of autonomous motion with chemometrics models, including partial least squares‐discrimination analysis (PLS‐DA) on the obtained SERS data, represents a promising step toward MM‐based diagnostic systems.