Development of plasmonic U‐bent plastic optical fiber probes for surface enhanced Raman scattering based biosensing.

Evanescent wave‐based excitation of noble metal nanostructures on fiber core surface allows simultaneous excitation over a larger area in comparison with free space coupling, and hence highly suitable for development of surface‐enhanced Raman scattering (SERS)‐based sensor applications. This study describes the development of plasmonically active U‐bent plastic optical fiber (POF) probes for SERS‐based sensing. The SERS activity of gold nanostructures on the fiber probe surface obtained by means of electroless deposition, sputtering, and chemisorption of nanoparticles are thoroughly characterized using a confocal microscopic setup. Influence of excitation wavelength and laser excitation power on SERS activity and stability of the plasmonic U‐bent probes is evaluated. Gold‐sputtered POF probes and gold nanoparticle immobilized POF probes show higher enhancement factor in the order to ~108. A biosensor application of these POF‐based SERS sensors is demonstrated by realizing a sandwich immunoassay with 4‐MBA as Raman label. This study describes development of plasmonically active U‐bent plastic optical fiber probes for SERS‐based sensing. The SERS activity of gold nanostructures on the probe surface obtained by means of electroless deposition, sputtering, and chemisorption of nanoparticles are characterized using a confocal microscopic setup. Gold‐sputtered probes and gold nanoparticle immobilized probes show higher enhancement factor in the order to ~108. These probes are demonstrated for biosensor application as SERS sensors by realizing a sandwich immunoassay with 4‐MBA as Raman label. [ABSTRACT FROM AUTHOR]