title: Cu3-xP Nanocrystals as a Material Platform for Near-Infrared Plasmonics and Cation Exchange Reactions.
abstract: Synthesis approaches to colloidal Cu3P nanocrystals (NCs) have been recently developed, and their optical absorption features in the near-infrared (NIR) have been interpreted as arising from a localized surface plasmon resonance (LSPR). Our pump-probe measurements on platelet-shaped Cu3-xP NCs corroborate the plasmonic character of this absorption. In accordance with studies on crystal structure analysis of Cu3P dating back to the 1970s, our density functional calculations indicate that this material is substoichiometric in copper, since the energy of formation of Cu vacancies in certain crystallographic sites is negative, that is, they are thermodynamically favored. Also, thermoelectric measurements point to a p-type behavior of the majority carriers from films of Cu3-xP NCs. It is likely that both the LSPR and the p-type character of our Cu3-xP NCs arise from the presence of a large number of Cu vacancies in such NCs. Motivated by the presence of Cu vacancies that facilitate the ion diffusion, we have additionally exploited Cu3-xP NCs as a starting material on which to probe cation exchange reactions. We demonstrate here that Cu3-xP NCs can be easily cation-exchanged to hexagonal wurtzite InP NCs, with preservation of the anion framework (the anion framework in Cu3-xP is very close to that of wurtzite InP). Intermediate steps in this reaction are represented by Cu3-xP/InP heterostructures, as a consequence of the fact that the exchange between Cu+and In3+ions starts from the peripheral corners of each NC and gradually evolves toward the center. The feasibility of this transformation makes Cu3-xP NCs an interesting material platform from which to access other metal phosphides by cation exchange.
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: De Trizio
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Gaspari
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy ; IMEM-CNR, Parco Area delle Scienze, 37/A, 43124 Parma, Parma, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bertoni
authors.affiliation: Department of Physics, Politecnico di Milano , Piazza L. Da Vinci 32, 20133 Milano, Milano, Italy ; Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia (IIT) , Via Giovanni Pascoli 70/3, 20133 Milano, Milano, Italy.
authors.forename: Ilka
authors.initials: I
authors.lastname: Kriegel
authors.affiliation: Department of Physics, Politecnico di Milano , Piazza L. Da Vinci 32, 20133 Milano, Milano, Italy ; Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia (IIT) , Via Giovanni Pascoli 70/3, 20133 Milano, Milano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Moretti
authors.affiliation: Department of Physics, Politecnico di Milano , Piazza L. Da Vinci 32, 20133 Milano, Milano, Italy ; Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia (IIT) , Via Giovanni Pascoli 70/3, 20133 Milano, Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Scotognella
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Maserati
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Gabriele C
authors.initials: GC
authors.lastname: Messina
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Mirko
authors.initials: M
authors.lastname: Prato
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Marras
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy ; Department of Pharmacy and Biotechnology, University of Bologna , via Belmeloro 6, Bologna, Bologna I-40126, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cavalli
authors.affiliation: Department of Nanochemistry, CONCEPT Lab, Department of Nanostructures, and CompuNet, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Genova, Italy.
authors.forename: Liberato
authors.initials: L
authors.lastname: Manna