title: A top-down strategy towards monodisperse colloidal lead sulphide quantum dots.
abstract: Monodisperse colloidal quantum dots with size dispersions <10% are of great importance in realizing functionality manipulation, as well as building advanced devices, and have been normally synthesized via 'bottom-up' colloidal chemistry. Here we report a facile and environmentally friendly 'top-down' strategy towards highly crystalline monodisperse colloidal PbS quantum dots with controllable sizes and narrow dispersions 5.5%<σ<9.1%, based on laser irradiation of a suspension of polydisperse PbS nanocrystals with larger sizes. The colloidal quantum dots demonstrate size-tunable near-infrared photoluminescence, and self-assemble into well-ordered two-dimensional or three-dimensional superlattices due to the small degree of polydispersity and surface capping of 1-dodecanethiol, not only serving as a surfactant but also a sulphur source. The acquisition of monodisperse colloidal PbS quantum dots is ascribed to both the quantum-confinement effect of quantum dots and the size-selective-vaporization effect of the millisecond pulse laser with monochromaticity and low intensity.
authors.affiliation: Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Tao
authors.initials: T
authors.lastname: Ling
authors.forename: Wen-Tian
authors.initials: WT
authors.lastname: Wu
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.forename: Min-Rui
authors.initials: MR
authors.lastname: Gao
authors.forename: Chen
authors.initials: C
authors.lastname: Ling
authors.forename: Lan
authors.initials: L
authors.lastname: Li
authors.forename: Xi-Wen
authors.initials: XW
authors.lastname: Du