A novel C-shaped, gold nanoparticle coated, embedded polymer waveguide for localized surface plasmon resonance based detection

Abstract

In this study, a novel embedded optical waveguide based sensor which utilizes localized surface plasmon resonance of gold nanoparticles coated on a C-shaped polymer waveguide is being reported. The sensor, as designed, can be used as an analysis chip for detection of minor variations in the refractive index of its microenvironment, which makes it suitable for wide scale use as an affinity biosensor. The C-shaped waveguide coupled with microfluidic channel was fabricated by single step patterning of SU8 on an oxidized silicon wafer. The absorbance due to the localized surface plasmon resonance (LSPR) of SU8 waveguide bound gold nano particle (GNP) was found to be linear with refractive index changes between 1.33 and 1.37. A GNP coated C-bent waveguide of 200 μ width with a bend radius of 1 mm gave rise to a sensitivity of ∼5 ΔA/RIU at 530 nm as compared to the ∼2.5 ΔA/RIU (refractive index units) of the same dimension bare C-bend SU8 waveguide. The resolution of the sensor probe was ∼2 × 10⁻⁴ RIU.