Ultrasensitive optofluidic surface-enhanced Raman scattering detection with flow-through multihole capillaries.

3-Dimensional surface-enhanced Raman scattering (SERS) detection integrated with optofluidics offers many advantages over conventional SERS conducted under planar and static conditions. In this paper, we developed a novel optofluidic SERS platform based on nanoparticle-functionalized flow-through multihole capillaries for rapid, reliable, and ultrasensitive analyte detection. The unique configuration not only provides 3-dimensional geometry for significantly increased SERS-active area and inherent fluidic channels for rapid and efficient sample delivery, but also confines and transmits light along the capillary for large SERS signal accumulation. Using a capillary consisting of thousands of micrometer-sized holes adsorbed with gold nanoparticles, we investigated the proposed optofluidic SERS system using the transverse and longitudinal detection methods, where the SERS excitation and collection were perpendicular to and along the capillary, respectively. A detection limit better than 100 fM for rhodamine 6G was achieved with an enhancement factor exceeding 10(8).