Characterization and conductivity of Langmuir-Blodgett films prepared from an amine-substituted oligo(phenylene ethynylene)

Ana Villares, Donocadh P. Lydon, Paul J. Low, Benjamin J. Robinson, Geoffrey J. Ashwell, Felix M. Royo, Pilar Cea

Research output: Contribution to journalArticlepeer-review

30 Citations (Web of Science)

Abstract

This paper reports the assembly of well-defined molecular films from 4-[4-(4-hexyloxyphenylethynyl)phenylethynyl] -aniline (HBPEB amine), an oligomeric phenylene ethynylene (OPE) derivative, by means of the Langmuir-Blodgett technique. Initially, Langmuir films of HBPEB amine were prepared at the air-water interface and characterized with surface pressure vs area per molecule isotherms. Brewster Angle Microscopy was used to map the different phases of the monolayer at the air-water interface. UV-vis reflection spectroscopy showed a blue shift of 20 nm of the reflection spectrum of the Langmuir film with respect to the spectrum of a chloroform solution of HBPEB amine, which indicates that two-dimensional H-aggregates are formed at the air-water interface. The monolayers were transferred onto solid substrates with a Y-type deposition and a transfer ratio of 1. The excellent transfer characteristics permitted the construction of films comprising up to 150 layers, with a uniform architecture. The LB films fabricated from HBPEB amine show a blue shift of ca. 30 nm with respect to the chloroform solution of HBPEB amine, likely arising from a change in the orientation of the molecular transition dipole with respect to the surface normal in the solid-supported films in comparison with the Langmuir films at the air-water interface. The current-voltage (I-V) characteristics of LB monolayers are unexpectedly symmetrical, the asymmetric contacts not being apparent from the observed I-V characteristics.

Original languageEnglish
Pages (from-to)258-264
Number of pages7
JournalChemistry of Materials
Volume20
Issue number1
DOIs
Publication statusPublished - 8 Jan 2008
Externally publishedYes

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