Sonolumineszenz der Blasen, die nah Oberflächen zusammenbrechen
Physikalische Chemie von Molekülen, Flüssigkeiten und Grenzflächen, Biophysikalische Chemie
Zusammenfassung der Projektergebnisse
In this project I carried out studies on light emitting gas microbubble(s) in order to address the main problems of sonoluminescence (SL) and get new knowledge about this exciting phenomenon. This challenging work elegantly shows not only the bubble energy distribution in the close proximity of a surface, but also new excitation pathways to observe non-SL SiO emission from glass in water. The bubble energy is high enough to cause the fracture of the glass surface by shock wave and high pressure impact. On the other hand, glass itself can act as a secondary source for a material excitation if SL is perturbed at the closest experimentally achievable distance. Perturbation by a glass can dramatically change the spatial geometry of SL in multiple bubbles (MBSL) and excite Ar atoms on the surface. Moreover, it can initiate the formation of O I, O II, S I and S II features not observable in SBSL. It is remarkable that perturbation of MBSL can open new pathways for the induced crystallization in a bulk liquid: dissociation of sulphuric acid products in sonication causes the color change of the solution and yields small particles as precipitant. Single SL bubble (SBSL) cools down thermally as high resolution SBSL Ar atom lines systematically narrow with different symmetries in vertical (along Z axis) or horizontal (along X) perturbation by a glass. At the closest distance to the glass rod SBSL remains hot (~ 6,500 K) comparable to MBSL. Vertically perturbed SBSL is more effective with 10^2 times higher electron density Ne and twice higher pressure gradient, Psbsl . Even at low driving acoustic pressure amplitude (1.2-1.4 bar) the SBSL is still hot and emission peaks of Ar+ ions can appear: more experimental proof of plasma. To understand the light emission mechanism, SL spectra can be resolved in time with a 300 picosecond resolution. Two noble gases can be probed: krypton and xenon as SBSL is the brightest. The time-resolved SBSL spectra can be consistent with blackbody emission over all time ranges of the determined spectral shape (200-700 nm). A heating regime and a slightly longer cooling period can be evident with modest spectral changes. It is remarkable that time-resolved SBSL spectra support the compressional heating mechanism of sonoluminescence phenomenon. There are heating and cooling regimes that are nearly temporally symmetric. Time-resolved SBSL spectra fit well to Planck’s law. The peak emission SBSL temperature with krypton is ~16,000 K and with xenon is ~14,000 K. These values are only a few thousand K above time-averaged SBSL temperatures in the bulk. Overall, the reported results can be of significant interest to scientific community and industry dealing with cavitation bubbles and its application in surface science, green energy chemistry, sonochemistry, nanotechnology, biology and medicine. Last two disciplines are especially important as the findings of this work can be useful to predict the energy distribution from a bubble near a boundary and calculate the temperature or pressure delivered over a distance.
Projektbezogene Publikationen (Auswahl)
- 2nd Postdoctoral Symposium at the Beckman Institute for Advanced Science and Technology at Illinois (January, 2012) “Spectroscopy of Acoustic Cavitation”
Darya Radziuk
- 8th International Symposium on Cavitation „CAV 2012“ (Nanyang Technological University and National University of Singapore, Singapore, August, 2012) “Sonoluminescence near Glass Surface”
Darya Radziuk
- Summer School of the Max-Planck Institute of Colloids and Interfaces (Bari, October, 2012) “Single Bubble Sonoluminescence Resolved in Time and Perturbed near Glass”
Darya Radziuk
- “Sonoluminescence near glass surface”, Proceedings of the Eighth International Symposium on Cavitation (CAV 2012), 2012, 088, 802-803, Edited by C.-D. Ohl, E. Klaseboer, S. W. Ohl, S. W. Gong, B. C. Khoo, Singapore, ISBN: 978-981-07-2826-7
- 27th European Colloid and Interface Science “ECIS 2013” (Bulgarian Academy of Sciences, Sofia, September, 2013) “Single Bubble Perturbation in Cavitation Proximity of Solid Glass: Hot Spot versus Distance”
Darya Radziuk
- “Single bubble perturbation in cavitation proximity of solid glass: hot spot versus distance”, J. Phys. Chem. Chem. Phys., 2014, 16(8), 3534-3541
D. Radziuk, H. Moehwald, K. S. Suslick
(Siehe online unter https://doi.org/10.1039/c3cp52850b)
