Surface-spreading of self-enriched analyte for surface-enhanced Raman spectroscopy using nanoporous microarray structures

Abstract

A localized electromagnetic field enhanced by nanophotonic structures can significantly amplify some optical phenomena. Surface-enhanced Raman scattering (SERS) is one of the most famous examples using the light-matter interaction and this has gained a lot of attention due to its potential applications such as single-molecular label-free detection. Although the Brownian diffusion-based molecular delivery was frequently used in early researches, it has a fundamental detection limit in a nanoscale. To overcome the diffusion-limit, hydrophobicity-based molecular enrichment has been utilized. However, electromagnetic hotspots are blocked in realistic fluid since the volume of aggregation is much larger due to water-soluble pollutants and salt. Herein, the self-enriched SERS process was analyzed in realistic fluid with nanophotonic structures based on vertically-aligned carbon nanotube. Also, the limitation of the conventional self-enrichment method and a model explaining the hydrophobic deposition were suggested. Analytes in the realistic fluid were successfully detected by the controlled deposition based on the model. Finally, three-dimensional hydrophobic SERS nanostructures were explored by analyzing the infiltration of molecules into the nanocavities.