Self-assembly at Liquid-Liquid Interface: A New SERS Substrate for Analytical Sensing^†

As a highly powerful and sensitive tool, surface enhanced Raman scattering (SERS) has attracted extensive attention in quantification analysis. However, the strong dependence of SERS signal on the detailed local nanostructure makes quantitative SERS analysis suffer from difficulties in controlling the uniformity of nanoscale hot spots and the inefficiency of placing the targeted molecules in prefabricated hot spots. Thus, the development of uniform SERS substrates is becoming an urgent demand to impulse SERS technique for the application in practical systems. The self-assembly of nanoparticles (NPs) at the liquid-liquid interface (LLI) provides a molecular sharp and defect-free focal plane, in which the stable controlling of nanogap sizes and the feasible location of analytes can be virtually guaranteed, leading to greatly enhanced sensitivity and reproducibility of detections. On the other hand, the benefit of liquid/liquid systems allows for either hydrophilic, hydrophobic molecules to be captured and detected individually or simultaneously. Based on these advantages of the new SERS substrate, a variety of self-assembled NP arrays at the LLI have been developed for multiphase analyte detection. Herein, we review recently developed strategies to induce NPs self-assembly at the LLI and discuss the latest research progress on sensitive and reliable SERS analysis in practical applications. Finally, some perspectives are highlighted in the further development of the efficient methods to enhance the plasmonic properties and more practical SERS sensors for practical applications.