Plasmonic Cu_2−xS nanoparticles: a brief introduction of optical properties and applications

Abstract

LSPR of Cu2−xS and the resulting plasmonic applications are summarized. Remaining open questions and further research directions are proposed.

Massive Intracellular Remodeling of CuS Nanomaterials Produces Nontoxic Bioengineered Structures with Preserved Photothermal Potential

“…While some associate this NIR absorption to d−d transition of Cu 2+ ions, which is not affected by the solvent or the surrounding environment, others attribute such a behavior to a plasmonic effect generated by free hole oscillations. 37,38 In this case the effect of morphology on the localized surface plasmon resonance is not clearly understood, and it seems that the morphology has less influence on their plasmon oscillation mode with respect to the composition. 38 In all cases we can attribute the conservation of the photothermal potential to the preservation of the chemical composition, as confirmed by XAS performed over days on the units formed after disintegration of the original CuS nanomaterials.…”

“…While some attributed such absorption to plasmonic effects resulting from free hole oscillations in the semiconductor, others assigned it to a valence band transition, independent from the solvent or the surrounding environment, as opposed to plasmonic NPs, but both mainly governed by the chemical composition of NPs. 37,38 Hollow CuS-based nanostructures have received increasing interest in the field of nanomedicine over the last years. They can be used as cargos for drug delivery applications due to their hollow porous organization and for thermal therapy thanks to their physical plasmonic properties.…”

Two-dimensional copper based colloidal nanocrystals: synthesis and applications

“…Tunability of free charge carrier (∼10 16 to 10 21 cm −3 ) concentration by doping can alter the absorption window from visible to near-infrared to (NIR) mid-infrared (MIR) for Cu based chalcogenides which is not possible for noble metals. 180 For example, for Cu-deficient Cu 2− x S, which possess a diverse phase diagram, the LSPR frequencies can be tuned based on the free hole concentration depending on the Cu/S ratio. 181 Xie et al showcased how LSPR frequency changed depending on hole concentration by adding Cu + into CuS nanoplatelet templates.…”

Crystal structure dependent cation exchange reactions in Cu2−xS nanoparticles

“…1–10 Based on the LSPR, their unique applications including photothermal therapy, photocatalysis, two-photon upconversion as well as SERS probe are extensively exploited. 11–20 In addition to LSPR, the high mobility of Cu + in Cu 2− x S NP lattice, which can be readily exchanged by guest cations ( i.e. , cation exchange reaction), leads to the production of complex nanostructures and phases that would be otherwise inaccessible by traditional synthetic methods.…”

“…In Cu–S system, the crystal structure varies from most copper-sufficient monoclinic α-chalcocite Cu 2 S, hexagonal β-chalcocite Cu 2 S, cubic γ-chalcocite Cu 2 S, monoclinic djurleite Cu 1.94 S, to triclinic roxbyite Cu 1.8 S, cubic digenite Cu 1.8 S and orthorhombic anilite Cu 1.75 S, and to most copper-deficient hexagonal covellite CuS. 20,60 The various crystal structures can be roughly catalogued by either asymmetric hcp (hexagonal close packing) or fcc (face-centered cubic) of sulfur anion framework, with copper cations occupying interstitial spaces in the sulfur lattice. 61 It is worth noting that, the covellite CuS has a unique layered structure despite the simplest stoichiometry, in brief, one planar trigonal CuS 3 layer is sandwiched by two tetrahedral CuS 4 layers and each CuS 4 –CuS 3 –CuS 4 triple layer is stitched to neighboring triple layers through disulfide (S–S) covalent bonds.…”