Preparation of metal–SAM–dendrimer–SAM–metal junctions by supramolecular metal transfer printing†
Metal–self-assembled monolayer (SAM)–dendrimer–SAM–metal junctions were prepared by a new type of metal transfer printing (mTP) that uses multiple β-cyclodextrin (βCD) host–guest interactions between a metal-coated stamp decorated with a monolayer of host molecules and a substrate which is functionalized with the same host molecules. Metal transfer from the stamp to the substrate is mediated by multivalent guest molecules, immobilized at either the host-functionalized stamp or the substrate, which act as a supramolecular “glue”. A βCD SAM was formed at thin Au films that were deposited onto PDMS stamps. Conformal contact of these functionalized PDMS stamps with redox-active monolayers of different generations of ferrocenyl- (Fc-) and biferrocenyl- (BFc-) terminated dendrimers, or redox-inactive monolayers of adamantyl- (Ad-) terminated dendrimers adsorbed at βCD SAMs (“molecular printboards”) resulted in transfer of the Au from the PDMS stamp to the substrate. βCD SAMs at different substrates were used, e.g.Au and SiO2. Also transfer of metal to SiO2 surfaces was possible owing to electrostatic interactions between the positively charged dendrimers and the SiO2 substrate. Various types of metal patterns were transferred, such as dots, squares or lines with dimensions varying from 5 µm to 50 µm. Lines of 10 µm width and as long as 10 mm could be faithfully transferred.