Sonochemical synthesis advantages

Over the past few years, a large number of experimental approaches have been successfully used as routes to synthesize nanorods or nanowires based on titania, such as combining sol-gel processing with electrophoretic deposition,152 spin-on process,153 sol-gel template method,154-157 metalorganic chemical vapor deposition,158-159 anodic oxidative hydrolysis,160 sonochemical synthesis,161 inverse microemulsion method,162 molten salt-assisted and pyrolysis routes163 and hydrothermal synthesis.163-171 We will discuss more in detail the latter preparation, because the advantage of this technique is that nanorods can be obtained in relatively large amounts. 

Rana [117] has recently demonstrated that ultrasound radiation can be employed for the formation of vesicular mesoporous silica. The dimension of the vesicles ranged from 50-500 nm. If the synthesis is compared with a previous work on the synthesis of MSP silica vesicles [118], the advantages of the sonochemical synthesis are as follows (1) It employs the commonly used CTAB as a surfactant, instead of Gemini surfactant, C H2 +iNH(CH2)2NH2 (2) the sonochemical reaction takes 1 h as compared with 48 h (3) the reaction is conducted at 25-35 °C instead of 100 °C and (4) a higher surface area is obtained, 940, as compared with 280-520 m g k The special role of the bubbles in the formation of the vesicle is also explained. 

The addition of an allylic group was reported in the synthesis of heneicos-6-en-ll-one, the sex pheromone of the Douglas fir tussock moth.67 This method was compared advantageously to the classical processes employing the toxic tin hydrides, with respect to the rates, yields, and chemoselectivity.68,69 Concerning the stereoselectivity however, no major difference exists between the conventional and sonochemical methods.70,71... 

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