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Surface Pressure Induced Charge Transfer |
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Abstract: Structures and electronic states of a 1:1 mixture of bis-tetrathiafulvalene annulated macrocycle (1) and C60 in Langmuir films at the air-water interface and Langmuir-Blodgett (LB) films on solid substrates were examined. Compression of the Langmuir films induced for the first time a phase transition from a weakly interacting state without charge transfer (CT) to a neutral CT state. The scanning force microscope images of LB films transferred onto mica by a single withdrawal showed quite different spatial patterns depending on the CT states observed. When deposited at around 1 mNm-1, a domain structure with 3 nm height was obtained, which corresponded to the state without CT interaction. Contrastingly, once the CT interaction was induced by applying surface pressure, a network structure was observed with a height of 6 nm. The CT band, whose transition moment was almost parallel to the substrate surface, was observed at 11. 5x103 cm-1 in the polarized UVVIS-NIR spectra of the films deposited at 9 mNm-1. The phase transition was irreversible, although the surface pressure-area isotherm showed a reversible behavior below 9 mNm-1. The morphology and electronic state of the film was controllable merely by changing the surface pressure at the air-water interface. Keywords: Langmuir-Blodgett Film, Fullerene, Charge Transfer Transition, AFM, Nanowire. DOI:10.1166/jnn.2006.205 |