Low-temperature synthesis of oil-soluble CdSe, CdS, and CdSe/CdS core - Shell nanocrystals by using various water-soluble anion precursors
24 Mar 2007-Journal of Physical Chemistry C (American Chemical Society)-Vol. 111, Iss: 15, pp 5661-5666
TL;DR: In this article, a two-phase approach at a toluene-water interface was used to synthesize colloidal CdSe and CdS quantum dots at low temperatures (60-90 degrees C).
Abstract: Colloidal CdSe and CdS quantum dots were synthesized at low temperatures (60-90 degrees C) by a two-phase approach at a toluene-water interface. Oil-soluble cadmium myristate (Cd-MA) was used as cadmium source, and water-soluble Na2S, thiourea, NaHSe, Na2SeSO3, and selenourea were used as sulfur and selenium sources, respectively. When a cadmium precursor in toluene and a selenium precursor in water were mixed, CdSe nanocrystals were achieved at a toluene-water interface in the range of 1.2-3.2 nm in diameter. Moreover, we also synthesized highly luminescent CdSe/CdS core-shell quantum dots by a two-phase approach using poorly reactive thiourea as sulfur source in an autoclave at 140 degrees C or under normal pressure at 90 degrees C. Colloidal solutions of CdSe/CdS core-shell nanocrystals exhibit a photoluminescence quantum yield (PL QY) up to 42% relative to coumarin 6 at room temperature.
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TL;DR: A general strategy to craft a variety of plain nanorod, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors is reported.
Abstract: The ability to synthesize a diverse spectrum of one-dimensional (1D) nanocrystals presents an enticing prospect for exploring nanoscale size- and shape-dependent properties. Here we report a general strategy to craft a variety of plain nanorods, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors. These cylindrical unimolecular nanoreactors enable a high degree of control over the size, shape, architecture, surface chemistry, and properties of 1D nanocrystals. We demonstrate the synthesis of metallic, ferroelectric, upconversion, semiconducting, and thermoelectric 1D nanocrystals, among others, as well as combinations thereof.
283 citations
TL;DR: Bi(2)S(3) nanocrystals/BiOCl hybrid architectures with tunable band gaps were synthesized by a controlled anion exchange approach and they displayed highly efficient visible light photoactivities, which is associated with suitable energetics and structural topotactic relationship that can benefit the interfacial charge transfer.
247 citations
TL;DR: In this article, the chemical reactions between common precursors used in the synthesis of metal chalcogenide nanocrystals and how they affect the mechanism and kinetics of nanocrystal growth are surveyed.
Abstract: We survey the chemical reactions between common precursors used in the synthesis of metal chalcogenide nanocrystals and outline how they affect the mechanism and kinetics of nanocrystal growth. We emphasize syntheses of cadmium selenide and cadmium sulfide where a variety of metal and chalcogenide precursors have been explored, though this is supplemented by studies of zinc and lead chalcogenide formation where appropriate. This review is organized into three sections, highlighting kinetics, metal precursors, and chalcogenide precursors, respectively. Section I is dedicated to the role of precursor conversion as a source of monomers and the importance of the supply rate on nanocrystal nucleation and growth. Section II describes the structure and reactivity of cadmium carboxylates, phosphonates, and chalcogenolates. Section III describes the reaction chemistry of commonly employed chalcogenide precursors and the mechanisms by which they react with metal precursors.
180 citations
TL;DR: Hierarchical flower-like CuS hollow nanospheres were prepared using a solvothermal approach as mentioned in this paper, which could facilely prepare CuS with desired surface morphology by tuning the reaction conditions.
Abstract: Hierarchical flower-like CuS hollow nanospheres were prepared using a solvothermal approach. We could facilely prepare CuS with desired surface morphology by tuning the reaction conditions. Based on our results, we propose a phenomenological pathway for the formation of hierarchical flower-like CuS hollow nanospheres via nucleation, nuclei aggregate and inside out Ostwald ripening process. The prepared CuS was characterized for the structural and morphological properties by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained hierarchical flower-like CuS hollow nanospheres exhibited greatly enhanced visible-light photocatalytic activity for photodegradation of Rhodamine B and 2,4-dichlorophenol aqueous solution due to the synergistic effect of surface hierarchical structure with large surface area, porous hollow sphere structure and high visible light utilization.
102 citations
TL;DR: In this paper, a review focusing on recent developments in the study of hydrogen generation from water splitting using photoelectrochemical (PEC) cells based on metal oxide (MO) nanomaterials is presented.
Abstract: This review focuses on recent developments in the study of hydrogen generation from water splitting using photoelectrochemical (PEC) cells based on metal oxide (MO) nanomaterials. The emphasis is on the unique properties of MO nanostructures and their advantages as well as limitations for PEC solar hydrogen generation. While abundant and stable, metal oxide nanomaterials tend to have weak visible light absorption that limits their use for solar energy conversion. In addition, MO nanomaterials tend to exhibit a high density of trap states or defect sites that limit their overall efficiency. Different strategies have been developed to enhance visible light absorption (e.g., doping, dye, or quantum dot sensitization and band structure engineering using composite structures) as well as to enhance transport by reducing the density of trap states via surface modification, improving crystallinity, or using 1D structures. In some cases, combining different strategies has led to strong synergistic effects. Recent studies point to the importance and promise of engineering electronic band structure for improving PEC performance of MO nanostructures for hydrogen generation and other potential applications.
102 citations
References
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TL;DR: Semiconductor nanocrystals prepared for use as fluorescent probes in biological staining and diagnostics have a narrow, tunable, symmetric emission spectrum and are photochemically stable.
Abstract: Semiconductor nanocrystals were prepared for use as fluorescent probes in biological staining and diagnostics. Compared with conventional fluorophores, the nanocrystals have a narrow, tunable, symmetric emission spectrum and are photochemically stable. The advantages of the broad, continuous excitation spectrum were demonstrated in a dual-emission, single-excitation labeling experiment on mouse fibroblasts. These nanocrystal probes are thus complementary and in some cases may be superior to existing fluorophores.
8,542 citations
TL;DR: In this paper, a simple route to the production of high-quality CdE (E=S, Se, Te) semiconductor nanocrystallites is presented, based on pyrolysis of organometallic reagents by injection into a hot coordinating solvent.
Abstract: A simple route to the production of high-quality CdE (E=S, Se, Te) semiconductor nanocrystallites is presented. Crystallites from ∼12 A to ∼115 A in diameter with consistent crystal structure, surface derivatization, and a high degree of monodispersity are prepared in a single reaction. The synthesis is based on the pyrolysis of organometallic reagents by injection into a hot coordinating solvent. This provides temporally discrete nucleation and permits controlled growth of macroscopic quantities of nanocrystallites. Size selective precipitation of crystallites from Portions of the growth solution isolates samples with narrow size distributions (<5% rms in diameter). High sample quality results in sharp absorption features and strong «band-edge» emission which is tunable with particle size and choice of material
8,374 citations
TL;DR: Using two-phase reduction of AuCl4 by sodium borohydride in the presence of an alkanethiol, solutions of 1-3 nm gold particles bearing a surface coating of thiol have been prepared and characterised; this novel material can be handled as a simple chemical compound as mentioned in this paper.
Abstract: Using two-phase (water–toluene) reduction of AuCl4– by sodium borohydride in the presence of an alkanethiol, solutions of 1–3 nm gold particles bearing a surface coating of thiol have been prepared and characterised; this novel material can be handled as a simple chemical compound.
6,251 citations
TL;DR: In this article, the extinction coefficient per mole of nanocrystals at the first exitonic absorption peak, e.g., for high-quality CdTe, CdSe, and CdS, was found to be strongly dependent on the size of the nanocrystal, between a square and a cubic dependence.
Abstract: The extinction coefficient per mole of nanocrystals at the first exitonic absorption peak, e, for high-quality CdTe, CdSe, and CdS nanocrystals was found to be strongly dependent on the size of the nanocrystals, between a square and a cubic dependence. The measurements were carried out using either nanocrystals purified with monitored purification procedures or nanocrystals prepared through controlled etching methods. The nature of the surface ligands, the refractive index of the solvents, the PL quantum yield of the nanocrystals, the methods used for the synthesis of the nanocrystals, and the temperature for the measurements all did not show detectable influence on the extinction coefficient for a given sized nanocrystal within experimental error.
4,802 citations
TL;DR: In this paper, a synthesis of highly luminescent (CdSe)ZnS composite quantum dots with CdSe cores ranging in diameter from 23 to 55 A was reported.
Abstract: We report a synthesis of highly luminescent (CdSe)ZnS composite quantum dots with CdSe cores ranging in diameter from 23 to 55 A. The narrow photoluminescence (fwhm ≤ 40 nm) from these composite dots spans most of the visible spectrum from blue through red with quantum yields of 30−50% at room temperature. We characterize these materials using a range of optical and structural techniques. Optical absorption and photoluminescence spectroscopies probe the effect of ZnS passivation on the electronic structure of the dots. We use a combination of wavelength dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, small and wide angle X-ray scattering, and transmission electron microscopy to analyze the composite dots and determine their chemical composition, average size, size distribution, shape, and internal structure. Using a simple effective mass theory, we model the energy shift for the first excited state for (CdSe)ZnS and (CdSe)CdS dots with varying shell thickness. Finally, we characterize the...
4,293 citations