Femtoliter silver cups as surface enhanced Raman scattering active containers

Abstract

Femtoliter capacity Ag cups formed by the pulsed laser ablation of an Ag foil have beentried out as substrates for surface enhanced Raman scattering (SERS) measurements. Thecups are formed as the impinging droplets from the laser plume undergo a flowpattern before freezing into cup-like structures, resulting in a surface roughness(∼35 nm) that makes them ideal for SERS studies. The internal volume of the cups is in the femtoliter(10−15 l) range, well suited for small-scale reactions, particularly in biologicalstudies. The cups exhibit enhancement factors of the order of106 with the analyte molecule thiophenol. Individual cups have been dosed attoliter quantities(10−18 l) of the analyte and detected.