Hydrophobic Teflon films as concentrators for single-molecule SERS detection

Teflon films, made from polytetrafluoroethylene (PTFE), are widely known hydrophobic materials. In this paper, we utilize Teflon films as concentrators to construct active surface-enhanced Raman scattering (SERS) substrates to achieve a higher sensitivity for SERS detection. The fabrication method is simple via directly depositing a drop of silver colloidal solution on a piece of commercial Teflon film and drying it under ambient conditions. SERS measurements are carried out on Rhodamine6G (R6G) molecules, showing strong enhanced SERS signals even at a concentration of 10(-15) M and allowing single-molecule detection. Silver nanoparticles (Ag-NPs) supported on the Teflon films exhibit a higher SERS enhancement and better reproducibility compared with that on glass slides. Such a high enhancement effect is primarily attributed to the hydrophobic condensation effect of Teflon films towards both silver colloids and R6G molecules, thus causing the aggregation of Ag-NPs for more hot-spots and delivering R6G molecules to the hot-spot areas thereby overcoming the limit of diffusion.