Sonofragmentation of Molecular Crystals
25 Aug 2011-Journal of the American Chemical Society (American Chemical Society)-Vol. 133, Iss: 37, pp 14530-14533
TL;DR: Direct particle-shock wave interactions are indicated as the primary mechanism of sonofragmentation of molecular crystals.
Abstract: Possible mechanisms for the breakage of molecular crystals under high-intensity ultrasound were investigated using acetylsalicylic acid (aspirin) crystals as a model compound for active pharmaceutical ingredients. Surprisingly, kinetics experiments ruled out particle–particle collisions as a viable mechanism for sonofragmentation. Two other possible mechanisms (particle–horn and particle–wall collisions) were dismissed on the basis of decoupling experiments. Direct particle–shock wave interactions are therefore indicated as the primary mechanism of sonofragmentation of molecular crystals.
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TL;DR: This tutorial review provides examples of how the chemical and physical effects of high intensity ultrasound can be exploited for the preparation or modification of a wide range of nanostructured materials.
Abstract: High intensity ultrasound can be used for the production of novel materials and provides an unusual route to known materials without bulk high temperatures, high pressures, or long reaction times. Several phenomena are responsible for sonochemistry and specifically the production or modification of nanomaterials during ultrasonic irradiation. The most notable effects are consequences of acoustic cavitation (the formation, growth, and implosive collapse of bubbles), and can be categorized as primary sonochemistry (gas-phase chemistry occurring inside collapsing bubbles), secondary sonochemistry (solution-phase chemistry occurring outside the bubbles), and physical modifications (caused by high-speed jets or shock waves derived from bubble collapse). This tutorial review provides examples of how the chemical and physical effects of high intensity ultrasound can be exploited for the preparation or modification of a wide range of nanostructured materials.
829 citations
TL;DR: The individual and mutual effect of important input parameters on the nanomaterial synthesis process as a start to help understand the underlying mechanism is discussed and an objective discussion of the diversely synthesizednanomaterial follows to divulge the easiness imparted by sonochemistry.
239 citations
Cites background or methods from "Sonofragmentation of Molecular Crys..."
...report the influence of shockwave particle coupling on particle fragmentation by studying the effect of (a) inter-particle collision (b) particle-horn collision and (c) particlevessel collision, individually [24]....
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...This application, known as sonofragmentation, is produced from sonication of millimeter/micrometer sized particles slurry [24][195]....
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...Shock waves may also impact particles directly and induce fragmentation without the need of collision [24]....
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...In addition to interparticle collision, shockwave can interact directly with particle of suitable size and induce fragmentation [24]....
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...report the effect of coupling between aspirin crystal and shock wave that lead to fragmentation [24]....
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TL;DR: This review presents an alternative method of preparing MOF crystals and underline the advantages of ultrasound assisted (sonochemical) synthesis, as the effects of various factors, such as energy input, reagent concentration, adequate solvents, reaction time and more.
176 citations
TL;DR: This tutorial review examines the tribochemical interpretation of sonochemical reactivity and how the multifaceted action of cavitational phenomena determines molecular evolution.
Abstract: Chemists have discovered, and recently actively exploited, the fact that subjecting certain molecules to ultrasound waves can bring about transformations that give insight into the correlation between classical tribological processes and the mechanical action caused by collapsing microbubbles when sonic waves propagate through a liquid medium. Chemical transformations induced by ultrasound take place in solution via mechanisms that are markedly different from those associated with molecular activation in the solid state. Both fields, however, share some striking similarities and numerous sonochemical reactions can be rationalized in purely mechanical terms. This tutorial review examines the tribochemical interpretation of sonochemical reactivity and how the multifaceted action of cavitational phenomena determines molecular evolution. A series of case studies involving solids, crystals, and polymers illustrate the mechanical properties of sound waves.
170 citations
TL;DR: Decoupling experiments were performed to confirm that interactions between shockwaves and crystals are the main contributors to crystal breakage and emphasize the effects of ultrasound on the crystallization of organic molecules.
168 citations
Cites background from "Sonofragmentation of Molecular Crys..."
...Recently, Zeiger and Suslick reported a series of experiments that evaluate the contributions of four potential sources of sonofragmentation: interparticle collisions, particle-horn collisions, particle-wall collisions, or particle–shockwave interactions [73]....
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References
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TL;DR: The chemical effects of ultrasound derive primarily from acoustic cavitation, which results in an enormous concentration of energy from the conversion of the kinetic energy of the liquid motion into heating of the contents of the bubble as mentioned in this paper.
Abstract: The chemical effects of ultrasound derive primarily from acoustic cavitation. Bubble collapse in liquids results in an enormous concentration of energy from the conversion of the kinetic energy of the liquid motion into heating of the contents of the bubble. The high local temperatures and pressures, combined with extraordinarily rapid cooling, provide a unique means for driving chemical reactions under extreme conditions. A diverse set of applications of ultrasound to enhance chemical reactivity has been explored with important uses in synthetic materials chemistry. For example, the sonochemical decomposition of volatile organometallic precursors in low-volatility solvents produces nanostructured materials in various forms with high catalytic activities. Nanostructured metals, alloys, oxides, carbides and sulfides, nanometer colloids, and nanostructured supported catalysts can all be prepared by this general route. Another important application of sonochemistry in materials chemistry has been the preparation of biomaterials, most notably protein microspheres. Such microspheres have a wide range of biomedical applications, including their use in echo contrast agents for sonography, magnetic resonance imaging, contrast enhancement, and oxygen or drug delivery. Other applications include the modification of polymers and polymer surfaces.
1,550 citations
TL;DR: The fundamental principles of both synthetic methods and recent development in the applications of ultrasound in nanostructured materials synthesis are summarized.
Abstract: Recent advances in nanostructured materials have been led by the development of new synthetic methods that provide control over size, morphology, and nano/microstructure. The utilization of high intensity ultrasound offers a facile, versatile synthetic tool for nanostructured materials that are often unavailable by conventional methods. The primary physical phenomena associated with ultrasound that are relevant to materials synthesis are cavitation and nebulization. Acoustic cavitation (the formation, growth, and implosive collapse of bubbles in a liquid) creates extreme conditions inside the collapsing bubble and serves as the origin of most sonochemical phenomena in liquids or liquid-solid slurries. Nebulization (the creation of mist from ultrasound passing through a liquid and impinging on a liquid-gas interface) is the basis for ultrasonic spray pyrolysis (USP) with subsequent reactions occurring in the heated droplets of the mist. In both cases, we have examples of phase-separated attoliter microreactors: for sonochemistry, it is a hot gas inside bubbles isolated from one another in a liquid, while for USP it is hot droplets isolated from one another in a gas. Cavitation-induced sonochemistry provides a unique interaction between energy and matter, with hot spots inside the bubbles of approximately 5000 K, pressures of approximately 1000 bar, heating and cooling rates of >10(10) K s(-1); these extraordinary conditions permit access to a range of chemical reaction space normally not accessible, which allows for the synthesis of a wide variety of unusual nanostructured materials. Complementary to cavitational chemistry, the microdroplet reactors created by USP facilitate the formation of a wide range of nanocomposites. In this review, we summarize the fundamental principles of both synthetic methods and recent development in the applications of ultrasound in nanostructured materials synthesis.
1,501 citations
TL;DR: The effects of high-intensity ultrasound on solid-liquid slurries were examined and Turbulent flow and shock waves produced by acoustic cavitation were found to drive metal particles together at sufficiently high velocities to induce melting upon collision.
Abstract: Ultrasound has become an important synthetic tool in liquid-solid chemical reactions, but the origins of the observed enhancements remained unknown. The effects of high-intensity ultrasound on solid-liquid slurries were examined. Turbulent flow and shock waves produced by acoustic cavitation were found to drive metal particles together at sufficiently high velocities to induce melting upon collision. A series of transition-metal powders were used to probe the maximum temperatures and speeds reached during such interparticle collisions. Metal particles that were irradiated in hydrocarbon liquids with ultrasound underwent collisions at roughly half the speed of sound and generated localized effective temperatures between 2600 degrees C and 3400 degrees C at the point of impact for particles with an average diameter of approximately 10 microns.
548 citations
TL;DR: Application of spectrometric methods of pyrometry as well as tools of plasma diagnostics to relative line intensities, profiles, and peak positions have allowed the determination of intracavity temperatures and pressures.
Abstract: Acoustic cavitation, the growth and rapid collapse of bubbles in a liquid irradiated with ultrasound, is a unique source of energy for driving chemical reactions with sound, a process known as sonochemistry. Another consequence of acoustic cavitation is the emission of light [sonoluminescence (SL)]. Spectroscopic analyses of SL from single bubbles as well as a cloud of bubbles have revealed line and band emission, as well as an underlying continuum arising from a plasma. Application of spectrometric methods of pyrometry as well as tools of plasma diagnostics to relative line intensities, profiles, and peak positions have allowed the determination of intracavity temperatures and pressures. These studies have shown that extraordinary conditions (temperatures up to 20,000 K; pressures of several thousand bar; and heating and cooling rates of >10 12 Ks −1 ) are generated within an otherwise cold liquid.
537 citations
TL;DR: The results obtained so far make foreseeable that crystal size distribution, and even crystal shape, can be 'tailored' by appropriate selection of the sonication conditions.
507 citations