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Synthetic Methods to WO2.72 Nanorods

Vapor deposition techniques have been extensively studied for the fabrication of metal and metal oxide structures. Indeed, the first reported tungsten oxide nanorods were essentially grown by this method. This groundbreaking synthesis of W02.72 leaves room for improvement, however, as it requires a reaction temperature of 1600°C in an argon atmosphere. Additionally, the researchers found the reaction product to be commingling WO2.72 nanorods and WO3 platelets rather than pure nanorods. Later, [Pg.120]

It is worth reviewing how kinetic and thermodynamic factors generally affect the growth of nanostructures under the influence of surfactants. Though they used CdSe and PbS respectively to study the surfactant-assisted synthesis of nanorods, Peng et al. and Lee et al. have produced a pair of quite complimentary studies. Peng etal. observed that kinetic control via monomer concentration was the principle factor in their growth [Pg.121]

FIGURE 8.5. The effect of synthesis temperature on the anisotropy of PbS nanocrystals. Anisotropy is quantified by the / -factor (rioo/fm, the ratio of the central distance of the 100 faces to that of the 111 faces). The decreasing trend is hypothesized to be due to the increased ability to overcome the activation energy necessary to grow the higher energy faces of the crystal at higher temperature. After Lee et al. [Pg.122]

Lou and Zeng spotted the work of Park et al. and sought to improve on it by developing an aqueous synthetic route. In this method, water and sodium sulfate are added to freshly prepared tungstic acid and autoclaved at up to 200°C for up to 24 h (assuming saturated steam conditions, this corresponds to pressures of up to 15.5 bars). [Pg.122]

By varying the amount of sodium sulfate and the reaction time, the size of these rods was controlled. Only centrifugation was necessary to collect the nanorods, indicating that rod-rod repulsion was minimal. Though the authors don t offer a detailed explanation for the mechanism of the reaction, they h) othesize that the sulfate ions may adsorb onto side surfaces or modify the ionic strength to allow the formation of nanorods. This will be discussed in the following section. [Pg.123]


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