Sonochemical production

The sonochemical method has gained increasing attention as a useful technology for preparing nanoscale metals [33-35], metal oxides [36-38] and nanocomposites [39]. Excellent surface resonance can be obtained for nanoscale metallic copper 

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Yasui K, Tuziuti T, Iida Y (2004) Optimum bubble temperature for the sonochemical production of oxidants. Ultrasonics 42 579-584... 

Hua, I., Hoffmann, M. R., Sonochemical Production of Hydroxyl Radical and Hydrogen Peroxide The Effect of Frequency and Saturating Gas,Environmental Science and Technology, 31(8), pp. 2237-2243, 1997. 

Fig. 12.13 Relationship between sonochemical products and NaCl concentration. Ultrasound 200kHz, 200W Temperature 25°C Atmosphere Ar.

There is a correlation between sonochemical and sonoluminescence measurements, which is usually not observed. Sonoluminescence is the consequence that both the sonochemical production (under air) of oxidizing species and the emission of light reflect the variations of the primary sonochemical acts, which are themselves due to variations of the number of active bubbles. Pulsed ultrasound in the high-frequency range (> 1 MHz) is extensively used in medical diagnosis, and the effects of pulsed ultrasound in the 20-kHz range using an immersed titanium horn has been reported. ... 

Bradley M, Ashokkumar M, Grieser F (2003) Sonochemical production of fluorescent and phosphorescent latex paiticles. J Am Chem Soc 125 525-529... 

P. Diodati, G. Giannini, L. Mirri, C. PetriUo, F. Sacchetti, Sonochemical production of a noncrystalline phase of palladium. Ultrson. Sonochem. 4, 45—48 (1997)... 

M. Bradley, M. Ashokkumar, F. Grieser, Sonochemical production of fluorescent and phosphorescent latex particles. J. Am. Chem. Soc. 125, 525-529 (2003)... 

Numerical simulations of sonochemical production of BaTiOs nanoparticles. Ultrason. Sonochem., 18, 1211-1217. 

A moderate diastereoselectivity was observed in these reactions where a mixture of diastereomers could be generated.58 The reactivity of the halides followed the order of tertiary > secondary primary and iodide> bromide (chlorides did not react). The preferred solvent system was aqueous ethanol. The process was suggested to proceed by a free radical mechanism occurring on the metal surface under sonochemical conditions. Efforts to trap the intermediate [A] intramolecularly gave only a very low yield of the cyclization product (Scheme 10.4).59... 

As the temperature and pressure dramatically increase inside a bubble at the end of the collapse, water vapor and oxygen, if present, are dissociated inside a bubble and oxidants such as OH, O, and H2O2 are created [12, 13]. They dissolve into the liquid and solutes are oxidized by them. This is called sonochemical reaction. For example, potassium iodide (KI) in aqueous solution is oxidized by the irradiation of ultrasound ((1.1)), and the solution is gradually colored by the product (I3 ) as the irradiation time increases. 

Fig. 1.9 The calculated results as a function of ambient radius at 300 kHz and 3 bar in ultrasonic frequency and pressure amplitude, respectively. The horizontal axis is in logarithmic scale, (a) The peak temperature (solid) and the molar fraction of water vapor (dash dotted) inside a bubble at the end of the bubble collapse, (b) The rate of production of oxidants with the logarithmic vertical axis. Reprinted with permission from Yasui K, Tuziuti T, Lee J, Kozuka T, Towata A, Iida Y (2008) The range of ambient radius for an active bubble in sonoluminescence and sonochemical reactions. J Chem Phys 128 184705. Copyright 2008, American Institute of Physics...

Similar spatial distribution of active bubbles has been observed in partially degassed water and in pure water irradiated with pulsed ultrasound [67]. For both the cases, the number of large inactive bubbles is smaller than that in pure water saturated with air under continuous ultrasound, which is similar to the case of a surfactant solution. As a result, enhancement in sonochemical reaction rate (rate of oxidants production) in partially degassed water and in pure water irradiated with pulsed ultrasound has been experimentally observed [70, 71]. With regard to the enhancement by pulsed ultrasound, a residual acoustic field during the pulse-off time is also important [71]. 

Mizukozhi Y, Makise Y, Shuto T, Hu J, Tominaga A, Shrionita S, Tanabe S (2007) Immobilization of noble metal nanoparticles on the surface of Ti02 by the sonochemical method photocatalytic production of hydrogen from an aqueous solution of ethanol. Ultrason Sonochem 14 387-392... 

Bhattacharya and Gedanken [11] have reported a template-free sonochemical route to synthesize hexagonal-shaped ZnO nanocrystals (6.3 1.2 nm) with a combined micro and mesoporous structure (Fig. 8.1) under Ar gas atmosphere. The higher porosity with Ar gas has been attributed to the higher average specific heat ratio of the Ar which leads to higher bubble collapse temperatures. With an intense bubble collapse temperature, more disorder is created in the product due to the incompleteness of the surface structure that led to greater porosity. Importance of gas atmosphere has been noted when the same process was carried out in the presence of air which results in the formation of ZnO without any porosity. 

The objective of this chapter is to compile work related to the beginning of sonochemical research and its extension to the aqueous solutions of metal ions. Ultrasound propagation in aqueous salt solutions leads to the hydrolysis, reduction, complexation, decomplexation and crystallization. Such works from different laboratories, along with the effect of dissolved gases on the production of free radicals in water and aqueous solutions upon sonication has been reviewed in this chapter. The generation of turbidity, due to the formation of metal hydroxides and changes in the conductivity of these aqueous solutions, carried out in this laboratory, has also been reported, to give firsthand information of the ultrasound interaction of these solutions. 

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