Interaction between core and protection shell of N(butyl)4Cl- and N(octyl)4Cl-stabilized Pd colloids

We present X-ray absorption near edge structure (XANES) measurements on N(butyl)4Cl- and N(octyl)4Cl-stabilized Pd colloids at both the Pd LIII- and the Cl K-edge. Metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (HeI) results for these colloids, deposited on silica substrates, are also shown. The results provide detailed insight into the mechanism of bonding between the protection shell and the colloidal core. Both XANES and MIES suggest that the chlorine is present on the inside of the protection shell, located between palladium core and N(alkyl)4 groups forming the protection shell. Moreover, the XANES results suggest a dependence of the equilibrium position of the chlorine between the metal core and the alkyl chain on the length of the alkyl chains. The possible motivation for such an effect is discussed on the basis of different models. MIES, in addition, provides information on the thermal stability of the shell-stabilized Pd colloids.