Quantitative Single-Particle Analysis: Plasmon Damping Modulation via Interfacial Engineering in Metal-Semiconductor...

Plasmon damping plays a central role in photocatalysis and photochemistry in metal-semiconductor heterostructures, yet the interplay among distinct surface damping pathways remains poorly understood. Here, we synthesize asymmetric matchstick-shaped heterostructures, in which a silver cadmium selenide (AgCdSe) semiconductor bump is selectively attached to one end of a gold nanorod (Au-AgCdSe), and quantitatively analyze plasmon damping at the single-particle level. Single-particle dark-field spectroscopy reveals pronounced semiconductor interface damping (SID) at the metal-semiconductor interface, accounting for up to 37.4% of the total plasmon energy loss. Using 4-nitrothiophenol (4-NTP) as a molecular probe, we further investigate chemical interface damping (CID) and its interplay with SID. 4-NTP chemisorption broadens plasmon line widths in bare gold nanorods but induces anomalous narrowing in Au-AgCdSe heterostructures. This counterintuitive behavior mainly originates from competition between surface damping pathways, with the plasmonic response in these heterostructures governed primarily by SID, thereby suppressing CID. Consistent with this interpretation, surface-enhanced Raman scattering measurements reveal pronounced signal suppression on Au-AgCdSe heterostructures due to substantial plasmon damping, indicating reduced electromagnetic enhancement and attenuated charge-transfer processes, in agreement with d-band center analysis. These findings establish surface damping competition as a governing principle for tailoring plasmon lifetimes in metal-semiconductor heterostructures, with implications for plasmon-enhanced sensing and photocatalysis.