Localized surface plasmon resonance improving sensitivity of dye-sensitized photoelectrochemical sensors for Hg²⁺...

The impact is investigated of localized surface plasmon resonance (LSPR) in noble metal nanoparticles on the light absorption of dye molecules and its effect on the detection sensitivity of photoelectrochemical (PEC) systems. Results demonstrate that Au@SiO₂ nanoparticles (Au@SiO₂ NPs) enhance the light absorption of dye N3, potentially due to the increased polarity of the dye molecules in the electromagnetic field surrounding the plasmonic nanoparticles. The nanoparticles were integrated into N3-sensitized tin dioxide (SnO₂) electrode for mercury ions (Hg²⁺) PEC detection. The photocurrent response indicated that the PEC system with LSPR effect exhibits higher sensitivity. The photocurrent shows a strong linear correlation (R² = 0.991) with Hg²⁺ concentration over a wide range (10^-6 to 10^-12 mol·L^-1). The density functional theory (DFT) calculations show that Hg²⁺ interacts with the isothiocyanate (NCS) groups, widening the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the dye, leading to reduced absorbance and decreased electron-hole separation efficiency. These findings highlight the potential of the SnO₂/Au@SiO₂ NPs-N3-based PEC sensing platform for highly sensitive and selective detection of Hg²⁺ ions.