title: Metallic-like stoichiometric copper sulfide nanocrystals: phase- and shape-selective synthesis, near-infrared surface plasmon resonance properties, and their modeling.
abstract: In the realm of semiconductor nanomaterials, a crystal lattice heavily doped with cation/anion vacancies or ionized atomic impurities is considered to be a general prerequisite to accommodating excess free carriers that can support localized surface plasmon resonance (LSPR). Here, we demonstrate a surfactant-assisted nonaqueous route to anisotropic copper sulfide nanocrystals, selectively trapped in the covellite phase, which can exhibit intense, size-tunable LSPR at near-infrared wavelengths despite their stoichiometric, undoped structure. Experimental extinction spectra are satisfactorily reproduced by theoretical calculations performed by the discrete dipole approximation method within the framework of the Drude-Sommerfeld model. The LSPR response of the nanocrystals and its geometry dependence are interpreted as arising from the inherent metallic-like character of covellite, allowed by a significant density of lattice-constitutional valence-band free holes. As a consequence of the unique electronic properties of the nanocrystals and of their monodispersity, coherent excitation of symmetric radial breathing modes is observed for the first time in transient absorption experiments at LSPR wavelengths.
authors.affiliation: Center for Biomolecular Nanotechnologies@UNILE, Istituto Italiano di Tecnologia, Via Barsanti, I-73010 Arnesano, LE, Italy.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xie
authors.forename: Luigi
authors.initials: L
authors.lastname: Carbone
authors.forename: Concetta
authors.initials: C
authors.lastname: Nobile
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Grillo
authors.forename: Stefania
authors.initials: S
authors.lastname: D'Agostino
authors.forename: Fabio
authors.initials: F
authors.lastname: Della Sala
authors.forename: Cinzia
authors.initials: C
authors.lastname: Giannini
authors.forename: Davide
authors.initials: D
authors.lastname: Altamura
authors.forename: Christian
authors.initials: C
authors.lastname: Oelsner
authors.forename: Carola
authors.initials: C
authors.lastname: Kryschi
authors.forename: P Davide
authors.initials: PD
authors.lastname: Cozzoli
mesh_terms: D000042:Absorption; D016880:Anisotropy; D001698:Biomedical Engineering; D003102:Colloids / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D003460:Crystallization; D053768:Metal Nanoparticles / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D055095:Optics and Photonics; D020349:Surface Plasmon Resonance; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D003102:Colloids; D013501:Surface-Active Agents; D003300:Copper; C017846:cupric sulfide