Development of a flexible fiber surface-enhanced Raman scattering (SERS) probe using a hollow optical fiber and gold nanoparticles

A flexible fiber probe for surface-enhanced Raman scattering (SERS) measurement was developed for performing an extremely sensitive Raman analysis for biomedical applications. The Raman probe consists of a ball lens mounted on a hollow optical fiber and allows Raman signals to be measured by a contact mode. Gold (Au) nanoparticles were placed on the ball lens by a dip-and-dry method. The increase in the background noise due to the deposition of the Au nanocolloids was very small. By using this new SERS probe, a Raman spectrum of 5% gelatin aqueous solution was successfully measured. A strong SERS signal was observed for the gelatin molecule in the solution. In particular, a C-S stretching band at 732 cm ^-1 due to methionine residues, which could not be observed by an ordinary Raman microscope system, was observed clearly. The content of methionine was less than 1% in the gelatin molecule. The results show that this SERS probe has very high sensitivity and holds considerable promise in the applications of SERS spectroscopy for direct diagnosis of cancer tissues.