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 <i>in vivo</i> 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.
Mürvet Volkan, David L. Stokes, and Tuan Vo-Dinh, "Surface-Enhanced Raman of Dopamine and Neurotransmitters Using Sol-Gel Substrates and Polymer-Coated Fiber-Optic Probes," Appl. Spectrosc. 54, 1842-1848 (2000)