On the frequency and isotope effect in sonochemistry

Dekerckheer, Catherine; Dahlem, Olivier; Reisse, Jacques

doi:10.1016/s1350-4177(97)00003-5

Cited by 9 publications

(11 citation statements)

References 11 publications

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“…This interdependence cannot easily be studied experimentally in a nonlinear system like a cavitating liquid in a vessel containing an ultrasound emitter. So as to limit, but probably not eliminate, the risk of an artifact which could be due to an intensity difference at the two frequencies, the intensities at 1.7 MHz and 20 kHz were adjusted in our study in order to obtain the same rate for the Weissler reaction at both frequencies . Since the decay of the chemiluminescent signal and the acoustic relaxation seem to be correlated, it is reasonable to attribute the observed frequency effect to the wave production system even if the exact acoustic relaxation mechanism is not known.…”

Section: Resultsmentioning

confidence: 99%

“…In order to compare the chemiluminescent results at 20 kHz and at 1.7 MHz, a previously described relative method was used. 14 The power output at both frequencies was adjusted in order to obtain the same rate for the Weissler reaction 15 carried out under air. A reactor similar to the one used for the physical measurements but without the lateral extensions was used.…”

Section: Methodsmentioning

confidence: 99%

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Pulsed Sonochemistry

et al. 1998

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Very few papers are devoted to the study of the chemical effects of pulsed ultrasound in the low-frequency range. The present work consists of a systematic experimental study of the effects of pulsed ultrasound in the 20 kHz range using an immersed titanium horn. The light scattered by the bubble cloud, the acoustic pressure, and the sonochemical activity were measured. The sonochemical activity was studied by measuring the light emitted by a fast chemiluminescent reaction (oxidation of luminol). The chemiluminescence behavior observed at 20 kHz was compared with the behavior observed at 1.7 MHz. The chemiluminescence takes time to install when sonication starts and, at 20 kHz, the luminescence intensity decreases monoexponentially when sonication stops. Interestingly, at 1.7 MHz, the luminescence intensity decreases biexponentially with an important fast component. The interpretation of these various behaviors requires that the acoustical characteristics of the ultrasound generator and of the vessel, and also the properties of the bubble field, be considered.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Pulsed Sonochemistry

et al. 1998

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“…Over the past decade or so, there has been growing interest in the effect of frequency on acoustic cavitation and its associated sonochemical effects. ,,− The main reason for this lies in the potential for enhancing a sonochemical effect for a given energy input to the system, with the wider aim of gaining a better understanding of the underlying cavitation process at different frequencies. However, many aspects of cavitation in the multibubble field change when the frequency of sonolysis is altered.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Surfactants at the Gas/Solution Interface of Cavitation Bubbles: An Ultrasound Intensity-Independent Frequency Effect in Sonochemistry

2002

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A major limitation in determining the effects of ultrasound frequency in sonochemistry in relation to cavitation is that no reliable relationship exists between the energy supplied to the system and the energy converted by the cavitation process in producing a sonochemical effect. However, the current study presents a frequency effect that is independent of the energy supplied to the system. Spin-trapping of secondary carbon radicals with 3,5-dibromo-4-nitrosobenzenesulfonic acid-d 2 (DBNBS-d 2 ) and electron paramagnetic resonance (EPR) have been used to determine the relative ability of two nonvolatile surfactants [sodium 1-pentanesulfonic acid (SPSo) and sodium dodecyl sulfate (SDS)] to scavenge • H atoms and • OH radicals at the gas/solution interface of cavitation bubbles. The results obtained at 354 and 1057 kHz are compared to those observed previously at 47 kHz (Sostaric, J. Z.; Riesz, P. J. Am. Chem. Soc. 2001, 123, 11010-11019). At particular bulk surfactant concentrations, both surfactants reached a limiting plateau value in radical scavenging ability. At 354 kHz (and 47 kHz), the magnitude of this plateau was greater for SPSo compared to that for SDS. However, at 1057 kHz, no difference in the plateau value was observed between SPSo and SDS. Decreasing the ultrasound intensity at constant frequency during the sonolysis of SPSo and SDS resulted in a decrease in the -• CH-radical yield. However, there was no change in the relative plateau yield of -• CH-radicals between SPSo and SDS. Thus, at plateau concentrations, the relative ability of these n-alkyl chain surfactants to scavenge radicals at the gas/solution interface of cavitation bubbles depends on the frequency of sonolysis but is independent of ultrasound intensity. The results were interpreted in terms of a decrease in the rate of change of the surface area of "high-energy-stable cavitation bubbles" at higher frequencies. This would affect the relative adsorption and hence radical scavenging efficiencies of SPSo and SDS at the gas/solution interface of these types of cavitation bubbles.

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“…Instead, it has become commonplace to compare sonochemical yields on the basis of constant calorimetric power input to the solution or less commonly, on the basis of constant electrical power input to the transducer. However, as described in detail elsewhere [1][2][3] such comparisons have very limited value for studies on the relationship between acoustic cavitation and sonochemical yield.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous attempts have been made at identifying specific sonochemical reactions with which ultrasound exposure apparatus could potentially be standardized [4][5][6][7], synonymous to the use of the Fricke dosimeter in radiation chemistry [8]. However, none of these studies address the underlying problem with quantitative sonochemistry, a problem that was first brought to light in relation to quantifying sonochemistry at varying ultrasound frequencies [1,2,9]. That is, "… no reliable relationship exists between the energy supplied to the system and the energy converted by the cavitation process in producing a sonochemical effect" [3].…”

Section: Introductionmentioning

confidence: 99%

A comparative sonochemical reaction that is independent of the intensity of ultrasound and the geometry of the exposure apparatus

Sostaric

2008

Ultrasonics Sonochemistry

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Sonolysis of aqueous solutions of n-alkyl anionic surfactants results in the formation of secondary carbon-centered radicals (-*CH-). The yield of -*CH- depends on the bulk surfactant concentration up to a maximum attainable radical yield (the 'plateau yield') where an increasing surfactant concentration (below the critical micelle concentration) no longer affects the -*CH- yield. In an earlier study it was found that the ratio of -*CH- detected following sonolysis of aqueous solutions of sodium pentane sulfonate (SPSo) to that of sodium dodecyl sulfate (SDS) (i.e. CH(SPSo)/CH(SDS)) depended on the frequency of sonolysis, but was independent of the ultrasound intensity, at the plateau concentrations [J.Z. Sostaric, P. Riesz, Adsorption of surfactants at the gas/solution interface of cavitation bubbles: an ultrasound intensity-independent frequency effect in sonochemistry, J. Phys. Chem. B 106 (2002) 12537-12548]. In the current study, it was found that the CH(SPSo)/CH(SDS) ratio depended only on the ultrasound frequency and did not depend on the geometry of the ultrasound exposure apparatus considered.

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On the frequency and isotope effect in sonochemistry

Cited by 9 publications

References 11 publications

Pulsed Sonochemistry

Pulsed Sonochemistry

Adsorption of Surfactants at the Gas/Solution Interface of Cavitation Bubbles: An Ultrasound Intensity-Independent Frequency Effect in Sonochemistry

A comparative sonochemical reaction that is independent of the intensity of ultrasound and the geometry of the exposure apparatus

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