Rectification in langmuir-blodgett monolayers of organic d-D-σ-A molecules

Abstract

Amphiphilic molecules of the type D-σ-A (D = one-electron organic donor, s = saturated linking bridge, A = good organic one-electron acceptor, such as TCNQ) have been prepared which form Pockels-Langmuir monolayers at the air-water interface, and which can be transferred as Langmuir-Blodgett films onto solid substrates. MNDO calculations for some of these molecules are presented. Fourier transform infrared spectra of multilayers and monolayers by grazing-angle reflectance are also given. Crude rectification experiments of sandwiches Al I D-σ-A I Al gave only the ohmic conduction characteristic of the Al substrate, presumably because of defects.A very recent experiment experiment by scanning tunneling microscopy revealed that a single molecule of bis-(n-dodecyl)-aminophenylcarbamate of 2-bromo-5-hydroxyethoxyTCNQ (BDDAP-C-BHTCNQ) transferred as part of a Langmuir-Blodgett monolayer onto a Au I Agl mica surface does rectify electrical current; later results cast doubt on this interpretation.