Influence Of The Preferred Orientation Of Pyridine Derivatives With Donor Substituents On Chemical Interface Damping Induced In Silver-Coated Gold Nanorods With Different Shell Thicknesses

Chemical interface damping (CID) is one of the plasmon decay processes caused by adsorbate molecules in gold nanoparticles. Despite the advances in this field, the effect of pyridine derivatives having a preferred orientation on CID in silver-coated gold nanorods (AuNRs@Ag, core@shell) with different shell thicknesses remains unknown. Herein, dark-field scattering studies using pyridine derivatives with donor substituents as adsorbates in single AuNRs@Ag with two different Ag shell thicknesses are described. Pyridine derivatives having electron-donating groups (EDGs) were adsorbed on single AuNRs@Ag and induced a strong CID through the interaction of nitrogen with the Ag surface. AuNRs@Ag with thick shells showed a considerably enhanced CID effect compared with AuNRs@Ag with thin shells for all pyridine derivatives. Furthermore, pyridine derivatives with EDGs in the para position (4-aminopyridine and 4-dimethylaminopyridine) caused a decrease in the localized surface plasmon resonance (LSPR) linewidth broadening of single AuNRs@Ag compared with unsubstituted pyridine under the same experimental conditions. In contrast to the high inclination of pyridine molecules, pyridine derivatives bearing EDGs adopted a parallel orientation to the Ag surface according to surface-enhanced Raman spectroscopy and dynamic light scattering measurements, which resulted in different surface coverage on the Ag surface and decreased LSPR linewidth broadening. Therefore, this study provides deeper understanding of the effects of pyridine derivatives with donor substituents and Ag shell thickness on CID in single AuNRs@Ag.