Dynamic enrichment of plasmonic hot-spots and analytes on superhydrophobic and magnetically functionalized platform for surface-enhanced Raman scattering

Abstract

Surface-enhanced Raman scattering (SERS) has been considered as one powerful tool for trace detection in various fields from biochemical analysis to environmental monitoring. Even metallic nano-particles based platform has proved to be an efficient way for signal enhancement, the random distribution of plasmonic nano-particles and target analytes normally impose restrictions on the detection limit and signal uniformity. In this work, we propose a facile and effective strategy to realize the dynamic enrichment of analyte molecules and AuNPs within the evaporating micro-droplet for SERS based on the superhydrophobic and magnetically functionalized PDMS membrane. Integrated with the computer-based controller, the membrane decorated with hydrophobic silica nanoparticles enables to maintain the de-pinning status of the micro-droplet by driving the droplet back-and-forth during the evaporation and enrichment process. Through optimizing the parameters of the dynamic enrichment strategy, the diameter of the final deposition pattern of the micro-droplet (containing 10 μL AuNPs and 10 μL R6 Gmolecules) has been concentrated to ∼ 0.4 mm thanks to the continuous de-pinning effect. The Raman signal has been further intensified by ∼3.9 times with optimized uniformity (RSD of ∼8.2 %) compared with the static enrichment mode on superhydrophobic surface. Thanks to the ultra-enrichment capability, the platform can well detect the concentration of R6 G probe molecules down to 10−17 mol/L. We believe that the proposed approach can be promising for exploiting cost-effective and versatile platform in future application such as biological analysis, chemical micro-reactions, and trace molecule detections.