Anal. Chem. 87, 6017–6024 (2015)

There are a variety of substrates for surface-enhanced Raman scattering (SERS), which are typically in the form of plasmonic nanostructures made using either lithographic processes or biotemplates. However, these are often expensive to make and suffer from a low density of hot spots. Hsuen-Li Chen and colleagues at the National Taiwan University now show that fresh rose petals can act as an eco-friendly and inexpensive alternative substrate for SERS.

The researchers deposited a suspension of silver nanoparticles with diameters of 100 nm on either the upper or lower epidermis of a fresh rose petal and allowed it to dry before depositing a drop of the analyte, rhodamine 6G, on the nanoparticle-decorated petal. Because rose petals are hydrophobic, the large contact angle between the water droplets and the petal surface allowed the nanoparticles to form aggregates, and the analyte to be concentrated into a small spot on the surface upon evaporation. This concentrating effect increased the intensities of the SERS signals, and the method achieved a detection limit of 10−15 M. Further experiments showed that the lower epidermis of white petals gave the best SERS enhancement. Other colour petals gave rise to background signals, and simulation studies showed that nanoparticles distributed more efficiently on the planar nanofolds of the lower epidermis than the micropapillae structures on the upper epidermis.