A top–down strategy towards monodisperse colloidal lead sulphide quantum dots

Abstract

Monodisperse colloidal quantum dots with size dispersions o10% 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%oso9.1%, 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.

Nickel/Iron Oxide Nanocrystals with a Nonequilibrium Phase: Controlling Size, Shape, and Composition

“…In addition, an increased decomposition time led to reduced polydispersity, as defined by the standard deviation in size divided by the mean size. 67 As t d increased from 15 to 30 min, the polydispersity was reduced from 11.3% to 7.1%. This reduction in polydispersity is significant, since sub-10% polydispersity is considered the benchmark value of a highly monodisperse nanoparticle solution.…”

Pontos quânticos ambientalmente amigáveis: destaque para o óxido de zinco

“…[60][61][62][63] As sínteses de nanomateriais são subdivididas em duas categorias gerais de métodos, conhecidos como "bottom-up" e "top-down". Este último método, "de cima para baixo", consiste em tentar construir os nanocristais a partir de materiais massivos, 64 realizando técnicas físi-cas, como a litografia por feixes de íons ou lasers, 63,65,66 corrosão por íons reativos, 67 corrosão química em solução, 68 e eletrodeposição. 69 Esses métodos trazem vantagens na obtenção de nanomateriais com elevado grau de pureza e são facilmente aplicáveis para produção em larga escala.…”

“…As técnicas de síntese da química coloidal trazem ainda mais vantagens em relação aos métodos "top down", pois além de controlar com maior precisão e uniformidade o tamanho dos nanocristais, permitem modificar a superfície dos QDs no mesmo meio reacional. [60][61][62][63]65 Atualmente, as vias químicas de síntese são as mais utilizadas e estudadas para produção de QDs por envolverem métodos simples, uso de materiais acessíveis de baixo custo. Entre as diversas sínteses reportadas na literatura, algumas se destacam por serem reproduzidas com os precursores em solução, tendo os QDs como a fase coloidal, o que permite controlar a cristalização através dos processos de nucleação e crescimento.…”

Preparation of MoO3 QDs through combining intercalation and thermal exfoliation

“…For example, powerful oxidizing species, such as H 2 O 2 18 and hydroxyl radicals ( OH), induced by both electro-Fenton 19 and photo-Fenton 15 reactions were used to break chemical bonds in MoS 2 nanosheets and graphene oxide to acquire their QDs. 17 Compared to traditional methods for the preparation of QDs of non-layered materials 20 by chemical synthesis routes, such as the hot-injection method 21 or physical synthesis methods, such as laser physical vapor deposition 22 and laser irradiation, [23][24][25] top-down approaches to prepare QDs of layered materials do not rely on harsh reaction conditions and low-cost, high-yield preparation of materials, is feasible. 13,16 Solvothermal treatment was used to exfoliate MoS 2 /WS 2 nanosheets in good solvents to prepare monolayer QDs.…”