Tuning and Locking the Localized Surface Plasmon Resonances of CuS (Covellite) Nanocrystals by an Amorphous CuPd_xS Shell

Abstract

We demonstrate the stabilization of the localized surface plasmon resonance (LSPR) in a semiconductor-based core–shell heterostructure made of a plasmonic CuS core embedded in an amorphous-like alloyed CuPdxS shell. This heterostructure is prepared by reacting the as-synthesized CuS nanocrystals (NCs) with Pd2+ cations at room temperature in the presence of an electron donor (ascorbic acid). The reaction starts from the surface of the CuS NCs and proceeds toward the center, causing reorganization of the initial lattice and amorphization of the covellite structure. According to density functional calculations, Pd atoms are preferentially accommodated between the bilayer formed by the S–S covalent bonds, which are therefore broken, and this can be understood as the first step leading to amorphization of the particles upon insertion of the Pd2+ ions. The position and intensity in near-infrared LSPRs can be tuned by altering the thickness of the shell and are in agreement with the theoretical optical simulation based on the Mie–Gans theory and Drude model. Compared to the starting CuS NCs, the amorphous CuPdxS shell in the core–shell nanoparticles makes their plasmonic response less sensitive to a harsh oxidation environment (generated, for example, by the presence of I2).

Anisotropic Plasmonic CuS Nanocrystals as a Natural Electronic Material with Hyperbolic Optical Dispersion

“…It is interesting to note that the simulated spectra for the nanocrystals in air (n=1) exhibit the LSP resonance at 912 nm, in the spectral region where CuS has a natural hyperbolic dispersion, and the plasmonic resonance comes only from the NCs oriented along the in-plane direction with respect to the linearly polarized incident beam (this resonance has also the dominant response for longer wavelengths ( It is interesting to compare the spectral dependencies observed and simulated above to the prior empirical models used to evaluate the properties of LSP in CuS nanocrystals (See Supplementary Materials). 17,[27][28][29][30][31] By solving the inverse problem which takes the experimental values of the position and the linewidth of the measured absorption peak as the input parameters,…”

“…the Drude-Sommerfeld model can be used to determine an isotropic permittivity of CuS, using the plasma frequency and damping as fitting parameters, as is explained in detail in Methods (Figure 2a,b). This approach has been followed in all the previous works 17, [22][23][24][25][26][27][28][29][30][31][32] (Figure 2b).…”

One-pot scalable synthesis of all-inorganic perovskite nanocrystals with tunable morphology, composition and photoluminescence

“…The widely studied hot-injection procedure, involving the injection of precursors into hot reaction media under inert gas protection, is unsuitable for large-scale generation of perovskite NCs. Alternatively, other techniques such as heat-up and RT reaction involving a single one-pot setup at RT, can be readily extended to the gram-scale level, [53][54][55] and have been shown compatible with perovskite NCs production. 2,15,43,52 2 However, currently most reported heat-up or RT approaches involve either the pre-dissolving Cs and/or Pb precursors at high temperature before mixing or the introduction of a toxic solvent such as dimethyl formamide (DMF).…”

Synthesis of Palladium‐Based Crystalline@Amorphous Core–Shell Nanoplates for Highly Efficient Ethanol Oxidation

“…Until now, only a few successful results have been reported. In addition, these materials are either heteromaterials, in which the crystalline and amorphous areas are made of different chemical compositions, such as CuS (crystalline)/Pd‐Cu‐S (amorphous) [ 12,13 ] and Co (crystalline)/Co 3 O 4 (amorphous), [ 14 ] or homomaterials with the random distribution of the crystalline and amorphous areas, such as PtPb, [ 15 ] Pd, [ 11 ] and PdCu. [ 10 ] Furthermore, additional post‐treatment processes, such as ion irradiation treatment of the presynthesized crystalline nanoplates, [ 15,16 ] were required to obtain some of the heterostructures.…”