Abstract
A well-organized monolayer of alkylated perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI) has been formed onto CVD graphene transferred on a transparent substrate. Its structure has been probed by scanning tunnelling microscopy and its optical properties by polarized transmission spectroscopy at varying incidence. The results show that the transition dipoles of adsorbed PTCDI are all oriented parallel to the substrate. The maximum absorption is consistent with the measured surface density of molecules and their absorption cross section. The spectrum presents mainly a large red-shift of the absorption line compared with the free molecules dispersed in solution, whereas the relative strengths of the vibronic structures are preserved. These changes are attributed to non-resonant interactions with the graphene layer and the neighbouring molecules.
Highlights
Close-packed assemblies of dye molecules exhibit drastically altered photonic properties as compared with the isolated or diluted species [1]
We explore the changes in the optical transmission spectrum of an alkylated derivative of PTCDI upon its self-assembly onto a CVD graphene monolayer, and analyse the results based on scanning tunnelling microscopy (STM) data taken on the very same sample
The self-assembly was probed on two graphitic substrates, highly oriented pyrolytic graphite (HOPG) and monolayers of CVD graphene transferred either onto fused silica (“optical quartz”) or polyethylene terephthalate (PET)
Summary
Close-packed assemblies of dye molecules exhibit drastically altered photonic properties as compared with the isolated or diluted species [1]. The electrical conductivity of a CVD graphene monolayer is sufficiently high to apply scanning tunnelling microscopy (STM) and determine the structural data of the molecular assembly with atomic-scale accuracy. We explore the changes in the optical transmission spectrum of an alkylated derivative of PTCDI upon its self-assembly onto a CVD graphene monolayer, and analyse the results based on STM data taken on the very same sample.
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