  A crown-ether dithiol quaterthiophene is synthesized for its covalent
immobilization by double fixation on gold surface. While the corresponding
dithioester precursor exhibits Pb2+ complexation properties in solution as
evidenced by UV-vis spectroscopy and cyclic voltammetry, this Pb2+ affinity is
still maintained for monolayers of the dithiol on gold. In addition,
current-voltage measurements by Eutectic GaIn drop contact on the monolayer
show a significant increase (up to 1.6 x 1E3) of the current at low bias after
Pb2+ complexation.
