Polycyanurate Nanorod Arrays for Optical-Waveguide-Based Biosensing

Abstract

We demonstrate high-sensitivity biosensing by optical waveguide spectroscopy (OWS) at visible wavelengths using aligned polycyanurate thermoset nanorods (PCNs) arranged in extended arrays as waveguides. The PCNs formed by thermal polymerization of a cyanate ester monomer in self-ordered nanoporous alumina templates were 60 nm in diameter and 650 nm in length. Subtle refractive index changes of the medium surrounding the nanorods could be detected by monitoring the angular shifts of waveguiding modes. The sensing figure of merit thus achieved amounted to 196 reciprocal refractive index units and is, therefore, higher than that of other sensors based on angular modulation, while the configuration used here is eligible for further surface functionalization. Kinetics of the binding of taurine to the surface cyanate groups of the PCNs was monitored by OWS. Thus, modified PCNs bearing sulfonic acid groups at their surfaces were obtained. PCN arrays may represent a versatile platform for the design of biosensors.