Improved stability of gold nanoparticles on the optical fiber and their application to refractive index sensor based on localized surface plasmon resonance

A simple method for firmly immobilizing gold (Au) nanoparticles on optical fibers without using any binding molecules, via an Au capping process based on seed-mediated growth which controls the size of Au nanoparticles (AuNPs), was investigated. Changes in the size of AuNPs in relation to the growth times of these particles in aqueous chloroauric acid solution were examined. Connectivity between AuNPs and the optical fiber surface was analyzed using a spectrometer and a field emission scanning electron microscope. Because of advantages gained via this immobilization method, the fiber-optic based localized surface plasmon resonance sensor demonstrated higher stability and an improved refractive index sensitivity. The sensing performance of the sensor was studied using the antibody-antigen model. Changes in localized surface plasmon resonance intensity were highly correlated to antigen concentrations. Based on these results, we tested our sensor's ability to detect thyroglobulin (Tg) in the sera of patients, by comparing our results with those obtained via currently used clinical techniques.