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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.

Nanostructures with concave surfaces are not common, and their synthesis is still challenging. In this paper, we have successfully synthesized two kinds of five-fold-twinned Au decahedra and dodecagonal plates by changing the reaction conditions. 40 high-index {221} facets were observed in the concave decahedron. The truncated decahedral gold nanocrystals (NCs) with a large size of 250-350 nm were obtained for the first time, which breaks the assumption that the truncated five-fold-twinned Au nanoparticles (NPs) can only be obtained with a size below 5 nm. The growth mechanism and the evolution process of the gold nanostructures were discussed. This work provides a facile way to synthesize concave decahedra, truncated decahedra and dodecagonal plates with controlled nanostructures.