Dipole reversal in Langmuir-Blodgett films of an optically nonlinear dye and its effect on the polarity for molecular rectification

Langmuir - Blodgett (LB) films of isomeric donor - (pi-bridge) - acceptor molecules with either a hydrophobically substituted acceptor [D-pi-A-C16H33 ( 1)] or donor [A-pi-D-C16H33 ( 2)] exhibit second-harmonic generation and asymmetric current voltage characteristics: a reversed polarity for rectification arises from an inversion of the dipole orientations in the two types of monolayer.