KCS

This paper presents the elucidation of the mercury (Hg) amalgamation induced by electrochemical reduction on gold nanorods coated with mesoporous silica shell (AuNRs@mSiO₂) by single-particle spectroelectrochemistry. First, the silica shell significantly enhanced the structural stability of AuNR cores after Hg amalgamation with application of linear sweep voltages (LSVs). Thus, it became possible to focus on the spectral changes of AuNRs@mSiO₂ induced by the deposition of Hg without disturbance of structural deformation that also strongly affects the localized surface plasmon resonance (LSPR) properties. Second, following the application of LSV in the presence of Hg²⁺, a remarkable blue shift of LSPR peak was observed, caused by lowering of the work function due to the Hg adsorption, donating electron density to Au. Furthermore, the LSPR linewidth also showed a dramatic increase after the Hg deposition with LSV. Last, direct observation of the evolution of the Hg amalgamation process was presented by monitoring real-time LSPR peak and LSPR linewidth shifts of single AuNRs@mSiO₂ in the Hg solution according to application of electrochemical potential. Moreover, the results showed the possibility of in-situ tuning of the LSPR properties of AuNRs@mSiO₂ by the Hg deposition via electrochemical potential manipulations without disturbance of structural variations of AuNR cores. Keywords: Spectroelectrochemistry, Au-Hg amalgamation, Gold nanorods, Mesoporous silica shell, Single particle spectroscopy, Localized surface plasmon resonance