Photosensitivity and electrical properties of some azobenzene derivatives in Langmuir-Blodgett films

Abstract

Langmuir‐Blodgett (LB) multilayers prepared from methyl‐acylamino‐azobenzene derivatives have been investigated. Reversible transl cis photolsomerisation of N,N′‐dicyclohexyl‐N‐4‐[4‐(methyl‐palmitoylamino)phenylazo]benzoyl urea in LB films has been observed on alternate irradiation with UV (360 nm) and visible (450 nm) light. Anisotropy in the electrical conductivity of LB multilayers was observed. The electrical conductivity through the sample (bulk conductivity) was of the order of 10−10 S cm−1. In the case of in‐plane samples the conductivity is higher by several orders. The charge carrier trapping states in the energy gap of LB multilayers were deduced.

In Situ Raman Spectroscopy of Bias-Induced Structural Changes in Nitroazobenzene Molecular Electronic Junctions

“…Significant research effort has been invested toward understanding metal/molecule/metal molecular junctions, due to the interesting and possibly valuable properties of molecules as components in electronic circuits. , Such characteristics may include negative differential resistance, rectification, − conductance switching, − and photocurrent. − Molecular junction designs reported to date range from single-molecule junctions in scanning tunneling microscopy experiments or break junctions, − to monolayer junctions consisting of many molecules oriented in parallel between metallic or semiconducting contacts. − The nanometer size of such junctions in at least one dimension makes them difficult to probe by spectroscopic techniques that provide information about molecular structure. Furthermore, the generally opaque metallic contacts prevent characterization of molecular junctions with optical spectroscopy, even those with monolayer sensitivity.…”

Characterization of Carbon/Nitroazobenzene/Titanium Molecular Electronic Junctions with Photoelectron and Raman Spectroscopy

“…Of particular relevance here are molecular junctions composed of an array of molecules or a single molecule between two conventional conductors. An extensive effort has been expended to determine a variety of current−voltage responses of molecular junctions, such as rectification, − negative differential resistance, conductance switching, ,− photocurrent, − and various electron transport mechanisms. − ,− To date, the majority of this research has been performed on self-assembled organothiolate monolayers on gold substrates (SAMs) 4,5,16,19-21 or Langmuir−Blodgett (L−B) 2,3,7 films with either vapor-deposited metals, a mercury drop, or a scanning probe microscopy tip to complete the circuit. While these systems have exhibited interesting electronic behavior, they are difficult to characterize structurally with conventional spectroscopic techniques.…”