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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
i. High-resolution MBSL spectra from silicone oil under Ar have been
reported and analyzed.
ii. 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 MoS2 by the irradiation of solutions of
molybdenum hexacarbonyl generates a most unusual morphology.
Morphology of conventional and
sonochemically prepared MoS2
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

15. Thank you