Photophoretic Au@MoS2 micromotors are used as smart mobile substrates for dynamic surface-enhanced Raman spectroscopy (SERS) sensing. The photophoretic capabilities and swarming-like propulsion of the micromotors allow for their schooling and accumulation in the measuring spot, increasing the density of SERS-active gold nanoparticles for Raman mapping and, simultaneously, the preconcentration of the target analyte. The generation of "hot-microflake spots" directly in the Raman irradiation point results in a 15-18-fold enhancement in the detection of crystal violet without the requirement for additional external sources for propulsion. Moreover, the reproducible collective micromotor motion does not depend on the exact position of the laser spot concerning individual micromotors, which greatly simplifies the experimental setup, avoiding the requirements of sophisticated equipment. The strategy was further applied for the detection of malachite green and paraquat with a good signal enhancement. The new on-the-move-based SERS strategy holds great promise for on-site detection with portable instrumentation in a myriad of environmental monitoring and clinical applications.
Keywords: crystal violet; dichalcogenides; malachite green; mobile SERS substrates; paraquat; photophoretic; swarming.