title: Near-Infrared Emitting CuInSe₂/CuInS₂ Dot Core/Rod Shell Heteronanorods by Sequential Cation Exchange.
abstract: The direct synthesis of heteronanocrystals (HNCs) combining different ternary semiconductors is challenging and has not yet been successful. Here, we report a sequential topotactic cation exchange (CE) pathway that yields CuInSe2/CuInS2 dot core/rod shell nanorods with near-infrared luminescence. In our approach, the Cu(+) extraction rate is coupled to the In(3+) incorporation rate by the use of a stoichiometric trioctylphosphine-InCl3 complex, which fulfills the roles of both In-source and Cu-extracting agent. In this way, Cu(+) ions can be extracted by trioctylphosphine ligands only when the In-P bond is broken. This results in readily available In(3+) ions at the same surface site from which the Cu(+) is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE. Consequently, controlled cation exchange can occur even in large and anisotropic heterostructured nanocrystals with preservation of the size, shape, and heterostructuring of the template NCs into the product NCs. The cation exchange is self-limited, stopping when the ternary core/shell CuInSe2/CuInS2 composition is reached. The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates. The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible.
authors.affiliation: Debye Institute for Nanomaterials Science, Utrecht University , P.O. Box 80000, 3508 TA Utrecht, The Netherlands.
authors.forename: Ward
authors.initials: W
authors.lastname: van der Stam
authors.affiliation: Electron Microscopy for Materials Science (EMAT), University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Eva
authors.initials: E
authors.lastname: Bladt
authors.affiliation: Debye Institute for Nanomaterials Science, Utrecht University , P.O. Box 80000, 3508 TA Utrecht, The Netherlands.
authors.forename: Freddy T
authors.initials: FT
authors.lastname: Rabouw
authors.affiliation: Electron Microscopy for Materials Science (EMAT), University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Sara
authors.initials: S
authors.lastname: Bals
authors.affiliation: Debye Institute for Nanomaterials Science, Utrecht University , P.O. Box 80000, 3508 TA Utrecht, The Netherlands.
authors.forename: Celso de Mello
authors.initials: Cde M
authors.lastname: Donega
keywords: cation exchange; copper indium chalcogenide; heteronanocrystals; nanorods; quantum dots