title: Sonoluminescence and sonochemiluminescence from a microreactor.
abstract: Micromachined pits on a substrate can be used to nucleate and stabilize microbubbles in a liquid exposed to an ultrasonic field. Under suitable conditions, the collapse of these bubbles can result in light emission (sonoluminescence, SL). Hydroxyl radicals (OH()) generated during bubble collapse can react with luminol to produce light (sonochemiluminescence, SCL). SL and SCL intensities were recorded for several regimes related to the pressure amplitude (low and high acoustic power levels) at a given ultrasonic frequency (200kHz) for pure water, and aqueous luminol and propanol solutions. Various arrangements of pits were studied, with the number of pits ranging from no pits (comparable to a classic ultrasound reactor), to three-pits. Where there was more than one pit present, in the high pressure regime the ejected microbubbles combined into linear (two-pits) or triangular (three-pits) bubble clouds (streamers). In all situations where a pit was present on the substrate, the SL was intensified and increased with the number of pits at both low and high power levels. For imaging SL emitting regions, Argon (Ar) saturated water was used under similar conditions. SL emission from aqueous propanol solution (50mM) provided evidence of transient bubble cavitation. Solutions containing 0.1mM luminol were also used to demonstrate the radical production by attaining the SCL emission regions.
authors.affiliation: Mesoscale Chemical Systems, MESA + Research Institute, University of Twente, ME147, P.O. Box 217, 7500AE Enschede, The Netherlands. d.fernandezrivas@utwente.nl
authors.forename: David
authors.initials: D
authors.lastname: Fernandez Rivas
authors.forename: Muthupandian
authors.initials: M
authors.lastname: Ashokkumar
authors.forename: Thomas
authors.initials: T
authors.lastname: Leong
authors.forename: Kyuichi
authors.initials: K
authors.lastname: Yasui
authors.forename: Toru
authors.initials: T
authors.lastname: Tuziuti
authors.forename: Sandra
authors.initials: S
authors.lastname: Kentish
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse
authors.forename: Han J G E
authors.initials: HJ
authors.lastname: Gardeniers
mesh_terms: D000433:1-Propanol / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D049449:Luminescence; D008165:Luminol / Q000737:chemistry; D013010:Sonication / Q000295:instrumentation*; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D017665:Hydroxyl Radical; D008165:Luminol; D000433:1-Propanol