Hotspots on the Move: Active Molecular Enrichment by Hierarchically Structured Micromotors for Ultrasensitive SERS Sensing

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Abstract
Surface-enhanced Raman scattering (SERS) is recognized as one of the most sensitive spectroscopic tools for chemical and biological detections. Hotspots engineering has expedited promotion of SERS performance over the past few decades. Recently, molecular enrichment has proven to be another effective approach to improve SERS performance. In this work, we propose a concept of “motile hotspots” to realize ultrasensitive SERS sensing by combining hotspots engineering and active molecular enrichment. High-density plasmonic nanostructures supporting hotspots are assembled on the tubular outer wall of micromotors via nanoimprint and rolling origami techniques. The dense hotspots carried on these hierarchically structured micromotors (HSMs) can be magnet-powered to actively enrich molecules in fluid. Active enrichment manner of HSMs are revealed to be effective in accelerating the process of molecular adsorption. Consequently, SERS intensity increases significantly due to more molecules adjacent to hotspots after active molecular enrichment. This “motile hotspots” concept provides a synergistical approach in constructing SERS platform of high-performance. Moreover, the newly developed construction method of HSMs manifests possibility of tailoring tubular length and diameter as well as surface patterns on the outer wall of HSMs, demonstrating good flexibility in constructing customized micromotors for various applications.
Funding Information
  • Ministry of Education of the People's Republic of China
  • Ministry of Science and Technology of the People's Republic of China (2017YFA0403600)
  • National Natural Science Foundation of China (11874108)
  • Southeast University

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