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1. Sonochemistry Prepared by Abdel-Baset Mohamed Ahmed

2. • Ultrasonic irradiation of liquids triggers high-energy chemical reactions, often with light emission . • Cavitation can create extreme physical and chemical conditions in cold liquids. • When cavitation occurs near a solid surface, it drives high-speed jets of liquid into the surface, causing surface damage and exposure to heated surfaces. • Sonochemistry can be categorized into homogeneous sonochemistry of liquids, heterogeneous sonochemistry of liquid–liquid or liquid–solid systems, and sonocatalysis. Ultrasonic Irradiation and Sonochemistry

3. Acoustic Cavitation Acoustic cavitation: the origin of sonochemistry Acoustic cavitation is a phenomenon that occurs when ultrasound waves propagate through a liquid medium. When the pressure of the ultrasound waves is sufficiently high, it can create small bubbles or voids in the liquid. These bubbles grow and collapse rapidly due to the alternating high and low pressure cycles of the ultrasound wave

4. A typical sonochemical apparatus with direct immersion ultrasonic horn. Ultrasound can be easily introduced into a chemical reaction with good control of temperature and ambient atmosphere. Sonochemistry primarily come from acoustic cavitation, which concentrates sound energy (frequency > 20 kHz) . This rapid compression of bubbles generates heat, leading to large local temperatures and pressures Acoustic Cavitation

5. The Rayleigh- Plesset equation describes the behavior of the bubble radius 𝑅(𝑡) R ( t ) over time. It takes into account factors such as the surrounding liquid properties, the acoustic pressure field, and the compressibility and surface tension of the bubble. The equation is typically formulated as: The Rayleigh– Plesset equation is often applied to the study of  cavitation  bubbles, shown here forming behind a propeller. Acoustic Cavitation

6. SONOLUMINESCENCE Multiple-bubble Sonoluminescence (MBSL) If this cavitation is sufficiently intense to produce sonoluminescence, then the phenomenon is MBSL Single-bubble Sonoluminescence (SBSL) Forced into large-amplitude pulsations that it produces sonoluminescence emissions on each (and every) acoustic cycle. Types of Sonoluminescence First observed from water in 1934 by Frenzel and Schultes .

7. Spectroscopic Probes Of Cavitation Conditions The MBSL of both aqueous and non-aqueous solutions is similar to the emission expected from high-temperature flames; e.g., excited-state OH - from water High-resolution MBSL spectra from silicone oil under Ar have been reported and analyzed . the relative intensities of atomic emission lines in the sonoluminescence spectra of excited-state metal atoms produced by Sono-lysis of volatile Fe, Cr, and Mo carbonyls.

8. SONOCHEMISTRY Chemistry involves the interaction of energy and matter, with reactions requiring energy to proceed. Ultrasonic irradiation, unlike traditional energy sources, generates high-energy chemistry due to its immense local temperatures, pressures, and heating and cooling rates. This method, similar to photochemistry, introduces large amounts of energy in a short period, but with shorter durations and higher temperatures. Control of sonochemical reactions is limited by the Boltzmann energy distribution

9. Homogeneous Sonochemistry: Bond Breaking And Radical Formation the sonolysis of water, which produces both strong reductants and oxidants, is capable of causing secondary oxidation and reduction reactions. The OH radicals produced from the sonolysis of water are able to attack essentially all organic compounds (including halocarbons, pesticides, and nitroaromatics) and through a series of reactions oxidize them fully.

10. Applications of Sonochemistry to Materials Synthesis Sonochemical decomposition of volatile organometallic precursors in high-boiling solvents produces nanostructured materials in various forms with high catalytic activities. Sonochemical synthesis of nanostructured inorganic materials

11. The sonochemical synthesis of MoS 2 by the irradiation of solutions of molybdenum hexacarbonyl generates a most unusual morphology. Morphology of conventional and sonochemically prepared MoS 2 Applications of Sonochemistry to Materials Synthesis

12. Heterogeneous Sonochemistry: Reactions Of Solids With Liquids High-intensity ultrasound is widely used as a stoichiometric reagent to enhance the reactivity of metal powders and surfaces in various organic and organometallic reactions. Particularly those involving reactive metals such as Mg, Li, or Zn

13. Heterogeneous Sonochemistry (complete) Hydrogenations and hydrosilations by Ni powder, Raney Ni , and Pd or Pt on carbon. For example, the hydrogenation of alkenes by Ni powder is enormously enhanced (>105 -fold) by ultrasonic irradiation. This dramatic increase in catalytic activity is due to the formation of uncontaminated metal surfaces.

14. Some representative examples of heterogeneous sonochemistry

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