Neutron and X-ray Scattering on the Monolayer Structure of a Lecithin Fullerene-Derivative

Using neutron reflectivity with contrast variation, X-ray reflectivity, and grazing incident small-angle X-ray scattering (GISAXS), we have characterized the in-depth and in-plane structural characteristics of the Langmuir and Langmuir-Blodgett (LB) films formed by a novel lecithin C₆₀-derivative, FPTL, of three phospholipids jointly bonded on one single olefinic moiety of a C₆₀ cage. Based on the neutron reflectivity measured, we have proposed a monolayer structure, with the C₆₀ cages of FPTL lifted into the air and hydrophilic phospholipid heads immersed in water, for the FPTL Langmuir layer formed on water. On the other hand, the LB film of FPTL prepared on mica exhibits clear Kiessig fringes in the X-ray reflectivity profile, indicating a 27 Å monolayer film with less molecular orientation. With GISAXS, we have extracted an in-plane correlation length of about 210 Å for a possible in-plane aggregation of C₆₀ of FPTL in the LB monolayer. We have also demonstrated the highly ordered monolayer structures of a lecithin lipid, in elucidating the positive effect of the attached functional group-phospholipids on the monolayer formation of the lecithin C₆₀-derivative.