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Identifier 000441439
Title Ανάπτυξη και εφαρμογή ταυτόχρονης ατομικής φασματοσκοπίας εκπομπής πλάσματος λέιζερ και μοριακής φασματομετρίας μάζας υπερηχητικού ιοντισμού (LIBS-SSI-MS) στη μελέτη βιομορίων και συμπλόκων
Alternative Title Development and application of simultaneous Laser-Induced Breakdown Spectroscopy with Sonic-Spray Ionization Mass Spectrometry (LIBS-SS-MS) in the study of biomolecules and co-ordination compounds
Author Μαρματάκης, Κωνσταντίνος Ε
Thesis advisor Άγγλος, Δημήτριος
Reviewer Περγαντής, Σπυρίδων
Βελεγράκης, Μιχαήλ
Κιτσόπουλος, Θεοφάνης
Κουρής, Στυλιανός
Μαστοράκος, Επαμεινώνδας
Παπάζογλου, Δημήτριος
Abstract In the context of this research thesis a new hybrid technique (LIBS/SSI-MS) that combines Sonic-Spray Ionization Mass Spectrometry (SSI-MS) with Laser-Induced Breakdown Spectroscopy has been developed and tested. The new analytical technique will be able to provide simultaneously, in real time, information on both elemental composition and molecular weight of the target compounds. The combination of the two techniques is achieved by means of a pneumatic nebulizer, which is used to produce an aerosol spray from a liquid solution. Due to sonic-spray ionization, charged droplets are generated in the aerosol, leading in turn to the formation of charged molecules in the gas phase, which are analyzed in the mass spectrometer. In parallel, focusing of nanosecond laser pulses in the aerosol gives rise to the formation of a transient micro-plasma, whose intense emission is wavelength- and time-resolved producing LIBS spectra which enable determination of the elemental composition of the solution. In order to validate the accuracy, the applicability and the potential of the LIBS/SSI-MS methodology, various types of samples were studied including: standard solutions of Ca(II) and Ba(II) ions complexed with EDTA, metalloprotein solutions, containing alpha-lactalbumin and superoxide dismutase, and a Cu6-Er co-ordination compound (Mr = 1574 amu). In the case of metalloprotein analysis the proposed LIBS/SSI-MS technique enables determination of the metal ion concentration in the protein solution, which, combined with the protein molecular mass, yields the [Metal]:[Protein] concentration ratio. This represents the stoichiometry of the metal ions in the protein solution and can be related with the protein biological activity. In parallel, the time evolution of the aerosol plasma has been investigated, by means of time-resolved imaging spectroscopy, aiming to unravel the processes occurring during plasma formation and in particular its interaction with the aerosol droplets. More specifically images of the plasma plume have been collected over a long time scale following plasma initiation at the arrival of the laser pulse in the aerosol. Also, light sheet imaging has been employed for visualizing the spatial distribution of droplets emerging from the pneumatic nebulizer. These images showed that despite the constant gas flow through the nebulizer the number density of droplets varies in short time scales relevant to laser- and plasma-aerosol interaction. Under typical irradiation conditions (ΕPulse > 160 mJ), plasma formation is at first observed in the air-argon interface. The aerosol droplets within the plasma formation region gradually evaporate and diffuse in the plasma volume (V ≈ 20 mm3). The atomization and diffusion of the droplets are essentially complete at about 10 μs following plasma formation. Finally, the potential to use ultraviolet (λ = 248 nm) femtosecond (τ = 450 fs) laser pulses for plasma formation in the aerosol has been examined. The sensitivity of the fs-LIBS approach is about one order of magnitude lower compared to the ns-LIBS methodology, a fact that is attributed to the significantly lower energy (ΕPulse ≈ 15 mJ) that is used for plasma formation and to the lack of interaction between the plasma and the femtosecond laser pulses.
Language Greek
Subject Aerosol
Φασματοσκοπία πλάσματος λέιζερ
Issue date 2021-07-27
Collection   School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
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