טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentFun-Young Victoria
SubjectApplication of Short Pulse Multiphoton Ionization
for Surface Analysis under Ambient Conditions
DepartmentDepartment of Chemistry
Supervisor Professor Israel Schechter
Full Thesis textFull thesis text - English Version


Abstract

We developed an analytical method based on Multiphoton Ionization (MPI). It provides direct analysis of organic compounds on surfaces under ambient conditions. Multiphoton Ionization - Fast Conductivity (MPI-FC) facility was used to examine the intensity of MPI signals. This setup detects short-lived photoionization currents. This scheme was suggested as a detection method for reading Thin Layer Chromatographic (TLC) plates. The technique is suitable for non-fluorescent compounds and does not require complicated preparatory work. The data, obtained from direct scanning of the developed TLC plates, were represented as "MPI-chromatograms". The method was evaluated for environmentally relevant contaminants such as Polycyclic Aromatic Hydrocarbons (PAH). A quantitative correlation between analyte quantity and MPI signal intensity was observed. Detection limits as low as 3 pg mm‑2 were obtained. The effects of substrate conductivity were studied. Improved results were obtained using glycerol-wetted TLC plates during the MPI-FC scanning. In this approach one can obtain very stable and reproducible signals. The advantages of applying femtosecond laser pulses were also examined.