The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

This feature article highlights work from the authors' laboratories on the synthesis, assembly, reactivity, and optical applications of metallic nanoparticles of nonspherical shape, especially nanorods. The synthesis is a seed-mediated growth procedure, in which metal salts are reduced initially with a strong reducing agent, in water, to produce ∼4 nm seed particles. Subsequent reduction of more metal salt with a weak reducing agent, in the presence of structure-directing additives, leads to the controlled formation of nanorods of specified aspect ratio and can also yield other shapes of nanoparticles (stars, tetrapods, blocks, cubes, etc.). Variations in reaction conditions and crystallographic analysis of gold nanorods have led to insight into the growth mechanism of these materials. Assembly of nanorods can be driven by simple evaporation from solution or by rational design with molecular-scale connectors. Short nanorods appear to be more chemically reactive than long nanorods. Finally, optical applica...

Anisotropic metal nanoparticles: Synthesis, assembly, and optical applications

The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

http://depa.fquim.unam.mx/amyd//archivero/FidelmarLechugaSanabria_4940.pdf

Recent advances in the liquid-phase syntheses of inorganic nanoparticles.

Surface plasmons (SPs) are coherent oscillations of conduction electrons on a metal surface excited by electromagnetic radiation at a metal -dielectric interface. The growing field of research on such light -metal interactions is known as ‘plasmonics’. 1-3 This branch of research has attracted much attention due to its potential applications in miniaturized optical devices, sensors, and photonic circuits as well as in medical diagnostics and therapeutics. 4-8

Nanostructured plasmonic sensors.

In this paper, copper nanocrystals are produced by using Cu(AOT)2−isooctane−water solution as a template. Even if the template does not change with various salt additions, the nanocrystal growth markedly depends on the salt used. It is demonstrated that chloride ions enable the growth of nanorods with an aspect ratio varying with chloride concentration. Conversely, only a slight amount of bromide ion is needed to increase the nanorod aspect ratio from 3 to 5 without any changes when increasing the bromide ion concentration. A rather large number of cubes are produced. Formations of nanorods and cubes are explained in terms of anion adsorption on (111) and (100) faces, respectively. By replacing chloride by other ions, the morphology of copper nanocrystals drastically changes. In all cases, the nanocrystals formed are fcc single crystals with a polyhedral shape or crystals composed of fcc tetrahedra (deformed or not) bounded by (111) faces. Some cylinders are formed by the connection of 2 different crystal...

Is the anion the major parameter in the shape control of nanocrystals

In this review, we show that chemical reduction in colloidal assemblies favors the formation of size- and shape-controlled metallic nanoparticles. The key parameters that make possible the size control of spherical nanoparticles produced in spherical reverse micelles are the degree of hydration of the reactants, the dynamic character of the micelles, the capping with the surfactant, and the reducing agent concentration. The particle shape can be controlled by combining the strategy of the surfactant-based template and the capping of salts or molecules. Proof of the quality of the samples is given by the observation of two- and three-dimensional spontaneous self-organizations.

Size, shape, and structural control of metallic nanocrystals.

Direct Relationship Between Shape and Size of Template and Synthesis of Copper Metal Particles

Face-Centered-Cubic “Supracrystals” of Cobalt Nanocrystals

The use of reverse micelles makes it possible to produce copper nanocrystals characterized by various sizes and shapes. By increasing the water content, the average size of the metallic nanocrystal...

Isabelle Lisiecki

Papers

Is the anion the major parameter in the shape control of nanocrystals

Size, shape, and structural control of metallic nanocrystals.

Direct Relationship Between Shape and Size of Template and Synthesis of Copper Metal Particles

Face-Centered-Cubic “Supracrystals” of Cobalt Nanocrystals

Collections of copper nanocrystals characterized by different sizes and shapes: Optical response of these nanoobjects