In situ reversible tuning of chemical interface damping in mesoporous silica-coated gold nanorods via direct adsorption and removal of thiol.

Chemical interface damping (CID) is a recently proposed plasmon decay channel in gold nanoparticles. However, thus far, a very limited number of studies have focused on controlling CID in single gold nanoparticles. Herein, we describe a new simple method for reversible tuning of CID in single gold nanorods coated with a mesoporous silica shell (AuNRs@mSiO2). We used 1-alkanethiols with two different carbon chain lengths (1-butanethiol and 1-decanethiol) as adsorbates to induce CID. In addition, NaBH4 solution was used to remove the attached thiol from the AuNR surface. We confirmed the adsorption and removal of 1-alkanethiols on single AuNRs@mSiO2 and the corresponding changes in localized surface plasmon resonance (LSPR) peak wavelengths and linewidths. Furthermore, we investigated the effect of immersion time in NaBH4 solution on thiol removal from AuNRs@mSiO2. Therefore, the LSPR properties and CID can be controlled, thereby paving the way for in situ reversible tuning of CID by repeated adsorption and desorption of thiol molecules on single AuNRs@mSiO2.

Enhanced refractive index sensitivity of localized surface plasmon resonance inflection points in single hollow gold nanospheres with inner cavity.

Hollow gold nanoparticles have great potential for localized surface plasmon resonance (LSPR) sensing. In this study, we investigated the refractive index (RI) sensitivities of single hollow gold nanosphere (HAuNS) with thin Au shell and inner cavity and single solid gold nanosphere (AuNS) in media with different RIs. The HAuNS exhibited a remarkable improvement in the RI sensitivity than the AuNS of similar size. The increased RI sensitivity of HAuNSs was ascribed to plasmon coupling between the inner and outer surface of the Au nanoshell. We then investigated the homogeneous LSPR scattering inflection points (IFs) to better understand the RI sensitivity of single HAuNS. The LSPR IF at the long wavelength side exhibited a better RI sensitivity compared to the wavelength shift of its counterpart LSPR maximum peak. Furthermore, the single HAuNS showed a remarkable improvement in the RI sensitivity at the LSPR IFs when compared to the AuNS of similar size. Therefore, we provided a new insight into the effect of inner cavity of HAuNS on the RI sensitivity of homogeneous LSPR IFs for use in LSPR-based biosensors.