A large-scale SERS substrate fabricated by using femtosecond laser with superhydrophobicity

In this study, a simple method is proposed to fabricate surface-enhanced Raman scattering substrates on Cu surfaces by using the crossed femtosecond laser direct-writing technique. As the scanning speed increases, the nanostructured surfaces exhibit superhydrophobic properties with the contact angle showing a generally rising tendency. With the speed of 2000 mu m/s, we can acquire an area of 2500 x 2500 mu m(2) in just 4 minutes at a static contact angle of 151 degrees, which makes it a potential for large area fabrication. After being modified with Au nanoparticles, the Cu substrates display high SERS sensitivity with an enhancement factor up to 3.60 x 10(9). Possible reasons for the high sensitive SERS involve: 1) the Au nanoparticles with the size of 60 nm are uniformly distributed on the nanostructure-roughened Cu surfaces which induce strong localized surface plasmon resonance; and 2) due to the superhydrophobicity of the substrates, the detected molecules are confined into a small area, which makes the concentration increase equivalently.