Unimolecular rectification of monolayers of CH3C(O)S-C14H28Q(+)-3CNQ(-) and CH3C(O)S-C16H32Q(+)-3CNQ(-) organized by self-assembly, Langmuir-Blodgett, and Langmuir-Schaefer techniques

The advantage of "self-assembly" (strong covalent binding to substrates) was combined with the advantage of Langmuir-Blodgett (LB) or Langmuir-Schaefer (LS) transfer to a solid substrate (quantitative transfer of monolayers to the substrate). The electrical rectification (asymmetric conduction) by a monolayer of thioacetylalkylquinolinium tricyanoquinodimethanide was critically compared when these molecules had been transferred, by such competing techniques, onto gold electrodes, and then covered by a "cold gold" pad electrode. Unimolecular rectification was observed in the expected directions in the LB and LS monolayers. The Self-Assembled Monolayers (SAMs) were disordered; macroscopic measurements of rectification were unsuccessful for the SAMs, but successful for the down-stroke LB and LS monolayers, whose orientation and potential bonding to the Au surface should be identical to that of an ideal SAM.