title: Dual emission in asymmetric "giant" PbS/CdS/CdS core/shell/shell quantum dots.
abstract: Semiconducting nanocrystals optically active in the infrared region of the electromagnetic spectrum enable exciting avenues in fundamental research and novel applications compatible with the infrared transparency windows of biosystems such as chemical and biological optical sensing, including nanoscale thermometry. In this context, quantum dots (QDs) with double color emission may represent ultra-accurate and self-calibrating nanosystems. We present the synthesis of giant core/shell/shell asymmetric QDs having a PbS/CdS zinc blende (Zb)/CdS wurtzite (Wz) structure with double color emission close to the near-infrared (NIR) region. We show that the double emission depends on the excitation condition and analyze the electron-hole distribution responsible for the independent and simultaneous radiative exciton recombination in the PbS core and in the CdS Wz shell, respectively. These results highlight the importance of the driving force leading to preferential crystal growth in asymmetric QDs, and provide a pathway for the rational control of the synthesis of double color emitting giant QDs, leading to the effective exploitation of visible/NIR transparency windows.
authors.affiliation: CNR-INO SENSOR Lab, Via Branze 45, 25123 Brescia, Italy and Institut National de la Recherche Scientifique, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada. rosei@emt.inrs.ca haiguang.zhao@emt.inrs.ca.
authors.forename: Haiguang
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, piazza L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Sirigu
authors.affiliation: CNR-IMM Sezione di Bologna, Via Gobetti 101, 40129 Bologna, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Parisini
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, piazza L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Camellini
authors.affiliation: CNR-IMM Sezione di Catania, Strada VIII, 5, 95121 Catania, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Nicotra
authors.affiliation: Institut National de la Recherche Scientifique, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada. rosei@emt.inrs.ca haiguang.zhao@emt.inrs.ca and Institute for Fundamental and Frontier Science University of Electronic Science and Technology of China, Chengdu 610054, P.R. China and Center for Self-Assembled Chemical Structures, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 0B8, Canada.
authors.forename: Federico
authors.initials: F
authors.lastname: Rosei
authors.affiliation: CNR-IMM Sezione di Bologna, Via Gobetti 101, 40129 Bologna, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Morandi
authors.affiliation: Dipartimento di Energia, IFN-CNR, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Zavelani-Rossi
authors.affiliation: Institut National de la Recherche Scientifique, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada. rosei@emt.inrs.ca haiguang.zhao@emt.inrs.ca and Department of Engineering Sciences and Mathematics, Luleå University of Technology, 971 98 Luleå, Sweden. alberto.vomiero@ltu.se.
authors.forename: Alberto
authors.initials: A
authors.lastname: Vomiero