Charge transfer dynamics in self-assembled monomolecular films

Azobenzene-functionalized alkanethiols in self-assembled monolayers on gold

“…This case was, e.g., observed for N 2 on graphite, where the Auger spectrum following core ionization showed decay from both an ionic and a neutral intermediate state [42]. The interpretation is also in line with recent results by Feulner and coworkers, who proved that for alkanethiol SAMs with nitrile tailgroup, charge transfer in the N 1s π * -resonance depends strongly on the length of the aliphatic chain [41]. For a chain length of n = 16, no charge transfer occurred, and the N 1s XPS line was found at E res = −0.2 eV, i.e., above the π * -resonance transition.…”

“…This is similar to the findings for aromatic polymers [33,40] or benzene weakly chemisorbed on Cu(110) [32]. From the autoionization studies of Feulner and coworkers [41] we conclude that the alkane chain decouples the azobenzene chromophore from the surface rather effectively, and we would expect a high intensity of the satellites. The observed weak contribution of distinct shake-up transitions to the XP spectrum thus suggests that intermolecular interactions in the SAM are strong and lead to a quenching of intramolecular excitations.…”

“…In the SAMs headgroup and chromophore with tailgroup are separated by the alkane chain. As already mentioned, on the femtosecond time scale of core excitation and decay, charge transfer across this linker is very slow [41]. This again indicates that screening of the C 1s core holes in the azobenzene chromophore must be mediated by sizeable intra-and intermolecular screening.…”

Probing charge transfer dynamics in self-assembled monolayers by core hole clock approach

“…This problem could be however solved by specific molecular design suggested by us recently [51] and illustrated in Fig. 2.…”

Ways to Spin Resolved Core-Hole-Clock Measurements

“…It was also used to determine charge transit times through thin dielectric layers [13] and through monolayers of graphene on different substrates [14], and it was extensively applied in studies of charge transport dynamics in hybrid systems containing larger organic molecules [3,4,15]. For self-assembled monolayers, charge transfer times from distinct ligands through the aromatic or aliphatic backbones to the substrate have been explored [16][17][18][19][20]. By varying the length of the backbone, it was possible to untangle the transit times through the backbone, and across the anchor group at the interface [17].…”