Adsorption of surfactants at the gas/solution interface of cavitation bubbles: An ultrasound intensity-independent frequency effect in sonochemistry
Adsorption of surfactants at the gas/solution interface of cavitation bubbles: An ultrasound intensity-independent frequency effect in sonochemistry
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DOI：
10.1021/jp022106h
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发表时间：
2002-12-05
影响因子：
3.3
通讯作者：
Riesz, P
中科院分区：
文献类型：
--
作者：
Sostaric, JZ;Riesz, P
确定声化学中与空化有关的超声频率的影响的主要限制是，在提供给系统的能量与产生声化学效应的空化过程所转换的能量之间不存在可靠的关系。然而，目前的研究提出了一个频率的影响，是独立的能量供应给系统。用3，5-二溴-4-亚硝基苯磺酸-d（2）（DBNBS-d（2））对仲碳自由基的自旋俘获和电子顺磁共振（EPR）方法测定了两种非挥发性表面活性剂[1-戊磺酸钠（SPSO）和十二烷基硫酸钠（SDS）]对空化气泡气/液界面上H原子和OH自由基的相对捕获能力。将在354和1057 kHz下获得的结果与先前在47 kHz下观察到的结果（Sostaric，J.Z.; Riesz，P. J. Am. 2001，123，11010-11019）。在特定的散装表面活性剂浓度，这两种表面活性剂达到一个限制平台值的自由基清除能力。在354 kHz（和47 kHz）下，与SDS相比，SPSO的该平台的幅度更大。然而，在1057 kHz下，在SP 50和SDS之间没有观察到平台值的差异。在超声降解SPSO和SDS的过程中，在恒定频率下降低超声强度导致-（CH）-C-的减少。自由基产率然而，-（CH）-C-的相对平台产率没有变化。SPSo和SDS之间的自由基。因此，在平台浓度下，这些n-烷基链表面活性剂在气穴气泡的气体/溶液界面清除自由基的相对能力取决于超声分解的频率，但与超声强度无关。结果进行了解释，在更高的频率下的“高能量稳定的空化气泡”的表面积的变化率的下降。这将影响SPSO和SDS在这些类型的空化气泡的气体/溶液界面处的相对吸附和因此的自由基清除效率。
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)-C-.- radical yield. However, there was no change in the relative plateau yield of -(CH)-C-.- 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.