Comparison of different substrates for laser-induced electron transfer desorption/ionization of metal complexes

Four different substrates, namely, graphite, tungsten, amorphous silicon (alpha-Si) and titanium dioxide (TiO2) films, were compared in view of the laser-induced electron transfer desorption/ ionization ( LETDI) of metal coordination complexes. A rhenium complex with 8mercaptoquinoline, a copper complex with diphenylthiocarbazone and chlorophyll A were studied as the test analytes. The dependencies of the ion yield and the surface temperature on the incident radiation fluence were investigated experimentally and theoretically. The temperature was estimated using the numerical solution of a one-dimensional heat conduction problem with a heat source distributed in time and space. It was found that at the same temperature, the ion yield from the different substrates varies in the range of three orders of magnitude. The direct comparison of all studied substrates revealed that LETDI from the TiO2 and alpha-Si films offer a better choice for producing molecular ions of metal coordination complexes.