Magnetic Circular Dichroism Study on Dual Plasmonic Au@CuS Core–Shell Nanoparticles: Effects of Shell Thickness and Uniformity

Abstract

Dual plasmonic metal–semiconductor hybrids exhibit multifunctionalities for broad photophysical and photochemical applications. In this study, we focus on the magneto-optical (MO) properties of Au@CuS core–shell nanoparticles examined by magnetic circular dichroism (MCD) spectroscopy. The core–shell nanoparticles are prepared by a seeded growth protocol. The MCD response in the CuS (covellite) spectral region [= near-IR (NIR) region] has an inverted sign with respect to that of Au, demonstrating that the charge carriers inducing the surface plasmon behavior are different between CuS (p-type) and Au (n-type). The hole effective mass of covellite CuS is estimated on the basis of the cyclotron-derived MCD signal analysis. The MO activity, defined here as the maximum MCD amplitude normalized to extinction, is significantly damped when the shell is thin and nonuniform. Thicker and more uniform shell formation leads to the MO activity increase in the NIR region, but it is overall smaller than that of pure CuS nanoparticles, suggesting the existence of magnetoplasmonic coupling between the Au and CuS counterparts. We then believe our work will put forward developments toward the realization of flexible controllability of MO responses in dual plasmonic nanostructures.

Spectroscopic Insights into the Near-Infrared Polaronic Transitions in Surface-Passivated Substoichiometric MoO3–x Nanodots

“…To more clearly evaluate the characteristic features of the polaronic transitions in the NIR region, simultaneous deconvolutions of both absorption and MCD data (+1.6 T) were conducted. The deconvolution is constrained by the requirement that a “single set” of Gaussian components with identical shape parameters be used for the fitting of both absorption and MCD data. , To obtain a numerically adequate description, deconvolution using six Gaussian bands was successful. We here show the typical spectral fits of MCD and absorption spectra for sample ND2 , and the fitted data in water and DMF are shown in Figure a,b, respectively.…”

“…UV–vis–NIR absorption spectra were recorded using a Hitachi U-4100 spectrophotometer. MCD spectroscopic measurements were carried out using a JASCO J-820 spectropolarimeter equipped with a permanent magnet (PM-491LB) of 1.6 T (tesla) with parallel (+1.6 T) and antiparallel (−1.6 T) fields. , Fourier transform infrared (FT-IR) spectra were recorded using a JASCO FT/IR-550 spectrophotometer by the KBr disk pellet method. The phase structure was examined by using a powder X-ray diffraction (XRD) instrument (Rigaku Ultima-IV) with Cu Kα radiation (λ = 1.5405 Å).…”

“…Interestingly, linewidths and intensities of the two lower-energy peaks are strongly dependent on the solvent, whereas those of the highest-energy peak are not. Additionally, magnetic circular dichroism (MCD) reveals that the highest-energy peak arises from two interacting polaronic transitions that are close in energy, giving a derivative-like spectrum. − On the basis of not only the spectroscopic behaviors but also the defective center analysis using X-ray photoelectron spectroscopy (XPS), we propose a new mechanism to account for the NIR polaronic transitions from the viewpoint of bulk or surface polarons.…”

Evolution of Colloidal Plasmonic Heterostructures from Traditional Semiconductor Nanocrystals to Lead Halide Perovskites: A Review

“…Recently, Yao and co-workers developed a dual plasmonic Au-CuS core–shell heterostructure with broadband LSPR absorption surpassing both the visible and NIR regions of the electromagnetic spectrum . The UV–visible-NIR absorbance shows (Figure a) two LSPR peaks corresponding to the Au core (around 600 nm) and due to the CuS shell (around 1000 nm).…”

Smart Design of Noble Metal–Copper Chalcogenide Dual Plasmonic Heteronanoarchitectures for Emerging Applications: Progress and Prospects

“…Control over the shell thickness could be critical for the properties of such nanocomposites. When magneto-optical properties of dual plasmonic NPs were studied, a thicker shell demonstrated higher activity in the NIR region compared to a thin and nonuniform shell . Additionally, it was shown that coating dual plasmonic hybrid nanostructures with a layer of gold and formation of Au@Cu 2– x S@Au NPs results in suppression of the NIR LSPR of the Cu 2– x S nanoshell …”