Highly sensitive surface-enhanced Raman scattering using vertically aligned silver nanopetals

Surface-enhanced Raman scattering (SERS) has attracted great attention due to its high sensitivity and specificity in the detection of a variety of molecules. Recently, much effort has been focused on the development of novel nanostructured SERS substrate with reliable and excellent sensing performance. In this work, a transparent Ag thin film composed of vertically aligned, single-crystalline silver nanopetals with uniform distribution is fabricated by galvanic replacement reaction. The growth mechanism of such novel Ag nanopetals is proposed. Furthermore, the outstanding SERS performance of the as-prepared Ag nanostructured thin film is demonstrated using crystal violet as the model compound, and the Raman intensity shows concentration-dependent behavior following the Freundlich equation. Crystal violet as low as 500 pM is facilely detected with high reproducibility (n = 8). The enhancement factor is determined to be 108, which potentially enables the identification of crystal violet at single molecule level on the probed surface. The high sensitivity is attributed to the “hot spots” resulting from proximate edges of Ag nanopetals and the nanocavity architecture bounded by Ag nanopetals.