Directing the deposition of ferromagnetic cobalt onto Pt-tipped CdSe@CdS nanorods: synthetic and mechanistic insights.
TL;DR: Key synthetic considerations are discussed, with particular emphasis on reporting isolated yields of all intermediates and products from scale up of intermediate precursors.
Abstract: A methodology providing access to dumbbell-tipped, metal–semiconductor and metal oxide–semiconductor heterostructured nanorods has been developed. The synthesis and characterization of CdSe@CdS nanorods incorporating ferromagnetic cobalt nanoinclusions at both nanorod termini (i.e., dumbbell morphology) are presented. The key step in the synthesis of these heterostructured nanorods was the decoration of CdSe@CdS nanorods with platinum nanoparticle tips, which promoted the deposition of metallic CoNPs onto Pt-tipped CdSe@CdS nanorods. Cobalt nanoparticle tips were then selectively oxidized to afford CdSe@CdS nanorods with cobalt oxide domains at both termini. In the case of longer cobalt-tipped nanorods, heterostructured nanorods were observed to self-organize into complex dipolar assemblies, which formed as a consequence of magnetic associations of terminal CoNP tips. Colloidal polymerization of these cobalt-tipped nanorods afforded fused nanorod assemblies from the oxidation of cobalt nanoparticle tips a...
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TL;DR: In this article, a review of recent advances in the area of semiconductor-metal hybrid nanoparticles is presented, focusing on optical properties, electronic structure, electrical characteristics, and light induced charge separation effects.
Abstract: Hybrid nanoparticles combine two or more disparate materials on the same nanosystem and represent a powerful approach for achieving advanced materials with multiple functionalities stemming from the unusual materials combinations. This review focuses on recent advances in the area of semiconductor–metal hybrid nanoparticles. Synthesis approaches offering high degree of control over the number of components, their compositions, shapes, and interfacial characteristics are discussed, including examples of advanced architectures. Progress in hybrid nanoscale inorganic cage structures prepared by a selective edge growth mechanism of the metal onto the semiconductor nanocrystal is also presented. The combined and often synergistic properties of the hybrid nanoparticles are described with emphasis on optical properties, electronic structure, electrical characteristics, and light induced charge separation effects. Progress toward the application of hybrid nanoparticles in photocatalysis is overviewed. We conclude...
303 citations
TL;DR: The principles and examples of three major classes of conversion chemical reactions are reviewed: the Kirkendall effect for metal NPs, galvanic exchange, and anion exchange, each of which can result in void formation in NPs.
Abstract: Conversion chemistry is a rapidly maturing field, where chemical conversion of template nanoparticles (NPs) into new compositions is often accompanied by morphological changes, such as void formation. The principles and examples of three major classes of conversion chemical reactions are reviewed: the Kirkendall effect for metal NPs, galvanic exchange, and anion exchange, each of which can result in void formation in NPs. These reactions can be used to obtain complex structures that may not be attainable by other methods. During each kind of conversion chemical reaction, NPs undergo distinct chemical and morphological changes, and insights into the mechanisms of these reactions will allow for improved fine control and prediction of the structures of intermediates and products. Conversion of metal NPs into oxides, phosphides, sulphides, and selenides often occurs through the Kirkendall effect, where outward diffusion of metal atoms from the core is faster than inward diffusion of reactive species, resulting in void formation. In galvanic exchange reactions, metal NPs react with noble metal salts, where a redox reaction favours reduction and deposition of the noble metal (alloying) and oxidation and dissolution of the template metal (dealloying). In anion exchange reactions, addition of certain kinds of anions to solutions containing metal compound NPs drives anion exchange, which often results in significant morphological changes due to the large size of anions compared to cations. Conversion chemistry thus allows for the formation of NPs with complex compositions and structures, for which numerous applications are anticipated arising from their novel catalytic, electronic, optical, magnetic, and electrochemical properties.
288 citations
TL;DR: Recent trends in the self-assembly of amphiphilic block copolymers to multicompartment nanostructures (MCNs) under (semi-)dilute conditions are reviewed, with special emphasis on ABC triblock terpolymers.
Abstract: Compartmentalization is ubiquitous to many biological and artificial systems, be it for the separate storage of incompatible matter or to isolate transport processes. Advancements in the synthesis of sequential block copolymers offer a variety of tools to replicate natural design principles with tailor-made soft matter for the precise spatial separation of functionalities on multiple length scales. Here, we review recent trends in the self-assembly of amphiphilic block copolymers to multicompartment nanostructures (MCNs) under (semi-)dilute conditions, with special emphasis on ABC triblock terpolymers. The intrinsic immiscibility of connected blocks induces short-range repulsion into discrete nano-domains stabilized by a third, soluble block or molecular additive. Polymer blocks can be synthesized from an arsenal of functional monomers directing self-assembly through packing frustration or response to various fields. The mobility in solution further allows the manipulation of self-assembly processes into specific directions by clever choice of environmental conditions. This review focuses on practical concepts that direct self-assembly into predictable nanostructures, while narrowing particle dispersity with respect to size, shape and internal morphology. The growing understanding of underlying self-assembly mechanisms expands the number of experimental concepts providing the means to target and manipulate progressively complex superstructures.
270 citations
TL;DR: In this paper, a simple room temperature self-assembly method was proposed to synthesize highly efficient 1D semiconductor-1D carbon nanotubes composite photocatalyst, which showed that RGO cannot readily manifest its unique and prominent advantage over CNT for specific photocatalytic application.
156 citations
TL;DR: It is reported that the rod-to-seed exciton localization efficiency decreases with the rod length but is independent of band alignment between the CdSe seed and CdS rod.
Abstract: A critical step involved in many applications of one-dimensional seeded CdSe@CdS nanorods, such as luminescent solar concentrators, optical gains, and photocatalysis, is the localization of excitons from the light-harvesting CdS nanorod antenna into the light-emitting CdSe quantum dot seed. We report that the rod-to-seed exciton localization efficiency decreases with the rod length but is independent of band alignment between the CdSe seed and CdS rod. This universal dependence can be well modeled by the competition between exciton one-dimensional diffusion to the CdSe seed and trapping on the CdS rod. This finding provides a rational approach for optimizing these materials for their various device applications.
88 citations
Cites methods from "Directing the deposition of ferroma..."
...CdSe@CdS NRs of varying dimensions were synthesized using approaches reported by Manna and co-workers,(16) with slight modifications.(58,59) CdSe QDs of different sizes were used as seeds, and the lengths and diameters of overcoated CdS NRs were controlled by the ratio of CdSe QD seeds to CdS NR precursors....
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References
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TL;DR: Solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year, and if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user.
Abstract: Global energy consumption is projected to increase, even in the face of substantial declines in energy intensity, at least 2-fold by midcentury relative to the present because of population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of CO2 emissions in the atmosphere demands that holding atmospheric CO2 levels to even twice their preanthropogenic values by midcentury will require invention, development, and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable energy resources, solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. In view of the intermittency of insolation, if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user. An especially attractive approach is to store solar-converted energy in the form of chemical bonds, i.e., in a photosynthetic process at a year-round average efficiency significantly higher than current plants or algae, to reduce land-area requirements. Scientific challenges involved with this process include schemes to capture and convert solar energy and then store the energy in the form of chemical bonds, producing oxygen from water and a reduced fuel such as hydrogen, methane, methanol, or other hydrocarbon species.
7,076 citations
TL;DR: This work is able to synthesize as much as 40 g of monodisperse nanocrystals in a single reaction, without a size-sorting process, and the particle size could be controlled simply by varying the experimental conditions.
Abstract: The development of nanocrystals has been intensively pursued, not only for their fundamental scientific interest, but also for many technological applications. The synthesis of monodisperse nanocrystals (size variation <5%) is of key importance, because the properties of these nanocrystals depend strongly on their dimensions. For example, the colour sharpness of semiconductor nanocrystal-based optical devices is strongly dependent on the uniformity of the nanocrystals, and monodisperse magnetic nanocrystals are critical for the next-generation multi-terabit magnetic storage media. For these monodisperse nanocrystals to be used, an economical mass-production method needs to be developed. Unfortunately, however, in most syntheses reported so far, only sub-gram quantities of monodisperse nanocrystals were produced. Uniform-sized nanocrystals of CdSe (refs 10,11) and Au (refs 12,13) have been produced using colloidal chemical synthetic procedures. In addition, monodisperse magnetic nanocrystals such as Fe (refs 14,15), Co (refs 16-18), gamma-Fe(2)O(3) (refs 19,20), and Fe(3)O(4) (refs 21,22) have been synthesized by using various synthetic methods. Here, we report on the ultra-large-scale synthesis of monodisperse nanocrystals using inexpensive and non-toxic metal salts as reactants. We were able to synthesize as much as 40 g of monodisperse nanocrystals in a single reaction, without a size-sorting process. Moreover, the particle size could be controlled simply by varying the experimental conditions. The current synthetic procedure is very general and nanocrystals of many transition metal oxides were successfully synthesized using a very similar procedure.
3,704 citations
"Directing the deposition of ferroma..." refers methods in this paper
...To our knowledge, this level of synthetic detail has not been reported for these types of colloids and is an important step to facilitate wider utilization of these synthetic methods by the materials chemistry community.(52,87) Scheme 1....
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TL;DR: A simple extension of the process yielded platinum–cobalt oxide yolk-shell nanostructures, which may serve as nanoscale reactors in catalytic applications, and provides a general route to the synthesis of hollow nanostructureures of a large number of compounds.
Abstract: Hollow nanocrystals can be synthesized through a mechanism analogous to the Kirkendall Effect, in which pores form because of the difference in diffusion rates between two components in a diffusion couple. Starting with cobalt nanocrystals, we show that their reaction in solution with oxygen and either sulfur or selenium leads to the formation of hollow nanocrystals of the resulting oxide and chalcogenides. This process provides a general route to the synthesis of hollow nanostructures of a large number of compounds. A simple extension of the process yielded platinum-cobalt oxide yolk-shell nanostructures, which may serve as nanoscale reactors in catalytic applications.
3,059 citations
Journal Article•
TL;DR: Alivisatos et al. as mentioned in this paper demonstrate that hollow nanocrystals can be synthesized through a mechanism analogous to the Kirkendall Effect, in which pores form due to the difference in diffusion rates between two components in a diffusion couple.
Abstract: Formation of Hollow Nanocrystals through the Nanoscale Kirkendall Effect Yadong Yin, Robert M. Rioux, Can K. Erdonmez, Steven Hughes, Gabor A. Somorjai, A. Paul Alivisatos* Department of Chemistry, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. *To whom correspondence should be addressed. Email: alivis@uclink4.berkeley.edu Abstract We demonstrate that hollow nanocrystals can be synthesized through a mechanism analogous to the Kirkendall Effect, in which pores form due to the difference in diffusion rates between two components in a diffusion couple. Cobalt nanocrystals are chosen as a primary example to show that their reaction in solution with oxygen, sulfur or selenium leads to the formation of hollow nanocrystals of the resulting oxide and chalcogenides. This process provides a general route to the synthesis of hollow nanostructures of large numbers of compounds. A simple extension of this process yields platinum-cobalt oxide yolk-shell nanostructures which may serve as nanoscale reactors in catalytic applications.
2,678 citations
TL;DR: The synthesis of epitaxially grown, wurtzite CdSe/CdS core/shell nanocrystals is reported in this paper, where shells of up to three monolayers in thickness were grown on cores ranging in diameter from 23 to 39.
Abstract: The synthesis of epitaxially grown, wurtzite CdSe/CdS core/shell nanocrystals is reported Shells of up to three monolayers in thickness were grown on cores ranging in diameter from 23 to 39 A Shell growth was controllable to within a tenth of a monolayer and was consistently accompanied by a red shift of the absorption spectrum, an increase of the room temperature photoluminescence quantum yield (up to at least 50%), and an increase in the photostability Shell growth was shown to be uniform and epitaxial by the use of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and optical spectroscopy The experimental results indicate that in the excited state the hole is confined to the core and the electron is delocalized throughout the entire structure The photostability can be explained by the confinement of the hole, while the delocalization of the electron results in a degree of electronic accessibility that makes these nanocrystals
2,584 citations