Optical Fiber Based Gold Nanoparticles and Titanium Dioxide Modified In Situ Refractometer and Immunosensor

Gold nanoparticle (GNP) immobilized optical fiber sensors have been explored extensively in the last few decades. These sensors combine the intrinsic refractive index (RI) sensitivity of the fiber and the localized surface plasmon resonance (LSPR) effect of GNP to provide a high sensing response. On the other hand, titanium dioxide (TiO2) thin-film coating had drawn enormous attention due to its high RI, anti-corrosive nature, and bio-compatibility. In the current study, we have investigated the effect of GNP-TiO2 coating on bare decladded optical fiber for RI sensing. An inexpensive, absorbance-based study method has been proposed to optimize the TiO2 coating and fabricate the most sensitive GNP-TiO2 coated probe. Synergistic effect has been observed for GNP and TiO2 coating on optical fiber. The GNP-TiO2 coated probe has ~95% better response than the only GNP coated U-bend probe, the current state of the art. GNP-TiO2 thin film modified probe was more stable in comparison to the GNP coated probe in changing pH environment. The optimized probe was tested on a handheld
$\mu $
-sense device for RI sensing. The GNP-TiO2 coated probes were used for immunosensing, and the limit of detection of 3.3 nM with human immunoglobulin G (HIgG) was achieved. The GNP-TiO2 coated probes provided stable immunosensing response for a period of at least five weeks.