Fabrication and luminescence of designer surface patterns with beta-cyclodextrin functionalized quantum dots via multivalent supramolecular coupling.

Supramolecular microcontact printing was used to obtain controlled patterns consisting of quantum dots (QDs) functionalized at their periphery with beta-cyclodextrin (beta-CD) in combination with adamantyl terminated dendrimeric "glues". Functionalization of core--shell CdSe/ZnS QDs was achieved by surface ligation. Immobilization of the QDs from solution onto glass substrates printed with (a) adamantyl-terminated poly(propylene imine) dendrimers and (b) via direct microcontact printing of QDs onto the dendrimer layer both yielded stable and robust multilayer structures. The stability of the patterns was primarily due to multivalent supramolecular host--guest interactions between beta-CD located at the QD surface and adamantyl groups at the dendrimer periphery as the dendrimers acted as a "supramolecular glue". The surface-immobilized QDs were capable of forming host--guest complexes with other molecules of interest at binding cavities not occupied by adamantyl groups. Complex formation with ferrocene-functionalized molecules at these sites led to partial quenching of the luminescence emission of QDs demonstrating the principle for sensing using the QD multilayer structures.