Chemical interface damping (CID)
is a recently proposed
plasmon-damping
pathway based on the interfacial hot-electron transfer from metal
to adsorbate molecules. However, the in situ reversible tuning of
CID in single gold nanorods (AuNRs) has remained a considerable challenge.
In this study, we used total internal reflection scattering microscopy
and spectroscopy to investigate the CID induced by p-aminoazobenzene (p-AAB), which has fast photoisomerization
characteristics, attached to single AuNRs. We demonstrated the in
situ reversible tuning of CID in single AuNRs by switching between
ultraviolet (UV, 365 nm) and visible (vis, 465 nm) irradiation to
induce photoresponsive structural conversions between the cis and
trans forms of p-AAB in ethanol, leading to different
lowest unoccupied molecular orbital (LUMO) energies for both forms.
The localized surface plasmon resonance (LSPR) line width was wide
under vis irradiation but narrow under UV irradiation, indicating
that hot electrons are more efficiently transferred to trans-p-AAB with a low LUMO energy level. We further
investigated the in situ photoreversible tuning of CID by manipulating
supramolecular host–guest interactions between cucurbit[8]uril
(CB[8]) and p-AAB in the single AuNRs. Additionally,
real-time in situ reversible tuning of CID in single AuNRs was achieved
through photonic switching of the cis–trans forms of p-AAB inside CB[8]. The LSPR line width was narrow under
vis irradiation but gradually widened under UV irradiation before
narrowing again upon returning to vis irradiation, unlike the case
with p-AAB only. These results can be ascribed to
the fact that cis-p-AAB completely
encapsulated within CB[8] in water is thermodynamically more favorable
than trans-p-AAB. Therefore, we
have discovered a new strategy for tuning the CID by performing p-AAB photoisomerization and adjusting the wavelength of
incident light in single AuNRs. In addition, this study demonstrates
that CID can be effectively applied to the development of biosensors
to detect guest molecules and their structural changes inside the
cavity of CB[8] in single AuNRs.