Performance Evaluation of Rose Bengal Dye-Decorated Plasmonic Gold Nanoparticles-Coated Fiber-Optic Humidity Sensor: A Mechanism for Improved Sensing

Low-cost fiber-optic humidity sensors with fast response became demanding. Thus, well-dispersed pruned triangular plasmonic gold nanoparticles (AuNPs) of mean size 16.4 ± 7.3 nm were prepared in Rose Bengal dye (RBD) using pulsed laser ablation in liquid method at laser fluence of 7.9 ± 0.3 J/cm2. These stable RBD molecules-decorated AuNPs (RBD-AuNPs) showed enhanced fluorescence (lifetime decay ranged from 7.1 ± 0.9–6.4 ± 0.2 ns) and localized surface plasmon resonance absorption. The fabricated RBD-AuNPs-coated fiber-optic relative humidity sensor (FO-RHS) when tested against polyvinyl alcohol (PVA) at intensity modulation of 40–100 % RH) displayed higher sensitivity (0.08 a.u./%RH) and linearity (0.86 a.u./%RH) compared to the one coated with pure AuNPs. This improvement was mainly due to the adherence mechanism of –OH and COOH functional groups of RBD onto AuNPs surface, enabling in binding strongly the PVA molecules via hydrogen bonds.