Fiber-optic conical microsensors for surface plasmon resonance using chemically etched singlemode fiber

A new type of the fiber-optic microsensor for surface plasmon resonance (SPR) was created on the basis of the fabrication technology of optical fiber probes in nearfield scanning optical microscopy (NSOM). The newly developed SPR microsensors were prepared by coating a gold-metallic film on the chemically etched singlemode fiber containing a conical core. They were applied to the real-time monitoring of the refractive index (RI) of transparent liquids flowing in the microfluidic device. When SPR microsensors were chemically modified with a self-assembled monolayer presenting a hydroxyl group, they successfully responded to the refractive index from 1.33 to 1.40 RI with a sensitivity of 0.008 RI units that covers the interesting regions for SPR biosensor operated in a water solution.