Surface-enhanced Raman of dopamine and neurotransmitters using sol-gel substrates and polymer-coated fiber-optic probes

Surface-enhanced Raman spectroscopy (SERS) is used to detect catecholamines-viz., dopamine, norepinephrine, epinine, and isoproterenol-using a new substrate prepared with sol-gel technology. Catecholamines are complexed at the surface by iron(III) ions, which were introduced during the reduction of the silver ions embedded inside the sol-gel matrix. With the use of a He-Ne laser at a power of only 12 mW, it is possible to measure dopamine in the micromolar concentration range. A single-fiber SERS probe system was also introduced that has great potential for sampling in micro-environment applications such as in vivo measurements of dopamine. In this microprobe design both excitation and SERS signals are transmitted through the same fiber simultaneously. The tips of tapered fibers were coated with a polyvinyl alcohol polymer doped with metallic silver particles. The potential of the SERS method and microprobes for medical diagnostics is discussed.