Size and shape control

Kongkanand A, Tvrdy K, Takechi K, Kuno M, Kamat PV (2008) Quantum dot solar cells. Tuning photoresponse through size and shape control of CdSe-Ti02 architecture. J Am Chem Soc 130 4007-4015... 

Scheme 1 Illustration of the general synthetic method followed in our group for the synthesis of metal nanoparticles i decomposition of the precimsor, nucleation ii first growth process in ripening or coalescence leading to size and shape controlled objects through addition of stabilizers which prevent the full precipitation of the metal (iv)...

Figure 11. Size- and shape-control of nanoparticles via salt reduction in (a) the hydrophobic core of a surfactant oil in water micelle and (b) the hydrophilic core of a water-in-oil reverse micelle.

Scheme 2. Encapsulation of size- and shape-controlled Pt nanoparticles under neutral hydrothermal synthesis conditions of SBA-15. Silica templating block copolymers and silica precursors were added to PVP-protected Pt nanoparticle solutions and subjected to the standard SBA-15 silica synthesis conditions. Neutral, rather than acidic pH conditions were employed to prevent particle aggregation and amorphous silica formation [16j. (Reprinted from Ref. [16], 2006, with permission from American Chemical Society.)...

Among the several strategies used to achieve size and shape control, by far the most common one is to employ... 

X., Tohji, K., Jeyadevan, B., Shinoda,K., Ogawa, T., Arai, T., Hihara,T., and Sumiyama, K. (2002) Size- and shape-controls and electronic functions of nanometer-scale semiconductors and oxides. Colloids and Surfaces A Physicochemical and Engineering Aspects, 202 (2-3), 291-296. 

The possibility of obtaining size- and shape-controlled nanoparticles, thereby giving efficient activities. 

Preliminary studies [1,2] suggest that the use of supercritical CO2 allows size- and shape-control of polymeric particles, in particular in the production of protein-loaded microparticles [3], However, to realise an industrial application of such a production, a reasonable economic income has to be expected. 

Gold nanorods (GNRs) can be produced with reasonable yields through several approaches such as template-based methods [158, 159], electrochemical methods [160, 161], or via seed-mediated wet chemistry methods. Due to their simplicity and the ease of nanorod size and shape control, the latter, seed-mediated growth methods in the presence or absence of Ag+ ions are commonly preferred [162-165],... 

An additional advantage of using microfluidic devices, which we do not have the space to discuss in detail here, is the absence of turbulence (Koo and Kleinstreuer, 2003). In the context of nanoparticle synthesis, turbulence gives rise to unpredictable variations in physical conditions inside the reactor that can influence the nature of the chemical product and in particular affect the size, shape, and chemical composition. In microfluidic devices, turbulence is suppressed (due to the dominance of viscous over inertial forces) and fluid streams mix by diffusion only. This leads to a more reproducible reaction environment that may in principle allow for improved size and shape control. 

Stranski-Krastanov mode). For many catalytic reactions the metal cluster s size and shape controls the turn-over rate of the reaction, resulting in a particular interest for the understanding of the cluster growth. Three processes are defined for the initial growth process the adsorption step, the diffusion step and the nucleation step. We will pay special attention to these three processes. 

The development of synthetic methods is one of the fundamental aspects to the understanding and development of nano-scale materials. The novel properties and numerous applications of nano-scale materials have encouraged many researchers to invent and explore preparation methods that allow control over such parameters as particle size, shape, size distributions and composition. While considerable progress has taken place, one of the major challenges is the development of a synthetic toolbox which would afford access to size and shape control of structures on the nano-scale and conversely allow scientists to study the effects these parameters impart to the chemical and physical properties of the nanoparticles. 

Finally, a study of fairly monodisperse CdSe semiconducting nanorods functionalized with amphiphilic molecules in a suspension of cyclohexane has recently been published that shows preliminary results indicative of a typical nematic behavior [ 102]. Note that these nanorods have been synthesized by the pyrolysis of organometallic precursors of Cd and Se in hot surfactant mixture allowing a good control of the aspect ratio. This state of the art particle size and shape control method should allow one to customize accurately their semiconducting properties. 

Size and Shape Control of y-AlOOH Boehmite Nanoparticles, a Precursor of y-Al203 Catalyst... 

Size and shape control ofboehmite nanoparticles, a precursor of y-Al20j catalyst... 

In addition to the reactions between ionic species in aqueous media, the reaction between metal and chalcogen-containing molecular carriers are readily kinetically controlled and allow better size- and shape-control of final materiakl l-l ... 

Esumi K, Ghosh SK, Kundu S, Mandal M, Pal T. 2002. UV photoactivation for size and shape controlled synthesis and coalescence of gold nanoparticles in micelles. Langmuir 75 7792-7797. 

Size- and shape-controlled cubo-octahedral platinum(o) nanoparticles of 4nm average size stabilized by sodium polyacrylate showing 111 and 100 surfaces were used to prepare Vulcan supported electrocatalysts. Cyclic voltammetric CO oxidation studies carried out by the thin film rotating disc method show two different sites of CO oxidation (Fig. 2.19). This can be assigned to differences in the activity of the crystal surfaces and is in agreement with single crystal studies. TEM results after cyclic voltammetric characterization show a complete absence of agglomerations. 

The product directly formed by extrusion is not strong and needs to be handled with considerable care. A system for the proper handling of extrudate is essential. For a product needed in the exact shape of the die or the holes in a die plate, a sophisticated system such as a belt or sequence of rollers having the same speed as the extrudate is needed. For some products, it is sufficient to simply allow the material to fall off the die plate under the action of gravity. This would be satisfactory if the product is to be of a granular form where very close size and shape control are not necessary. 

It was found that different growth strategies lead to fullerene-like nanoparticles and nanotubes with quite distinct structures, for example, chiral versus achiral nanotubes, as discussed later. Size and shape control of M0S2 nanotubes has been recently achieved [20], but has yet to be developed to other nanotubes and fullerene-like structures. Such control... 

Tailored Nanoparticles for Clean Technology - Achieving Size and Shape Control... 

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