Utilização da química verde e funcionalização de moléculas para aplicação em eletrônica orgânica

Abstract

In this work, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecules were functionalized by imidization using a decylamine. The functionalized molecule has been identified as PDI-C10 and the resulting yield of the synthesis was 56.4%. This method can be performed in aqueous medium, reflux tempeture (~100º C to 200º C) and reduced reaction time (~8 h), when compared with traditional processes from perylene derivates functionalisation. RMN and FTIR results indicated effective molecule modification, being observed signals related to the chemical shift for the hydrogen in decilamine in the RMN spectrum and, for the FTIR spectrum, an addictional peak in ~1350cm-1, relative to the vibration from the C-N bond in the imide group. From the XRD patterns, considering the peaks at 2ϴ = 7.8º and 9.5º (d = 1.12 nm and 0,93 nm) from PDI-C10 and PTCDA, respectively, a slight increase on the interplanar distances arises due to the alkyl side-chain in PDI-C10. Moreover, PDI-C10 films were produced from chloroform solution using the drop-casting method. SEM and confocal images pointed outa 1D nanobelts-like structures with width = 4.1 ± 0.4 µm and a length = 64 ± 6 µm, structures with length up to 170 µm were also observed. The UV-Vis absorbance spectrum acquired from PTCDA is composed of narrow bands with maxima in 428, 457, 488 and 525 nm and, comparatively, PDI-C10 has similar spectrum with a bathochromic shift of ~2 nm. As a result from the functionalization, higher interplanar distances and reduction of excimers, the PDI-C10 shows emission spectrum characteristic of isolated molecules, with Stokes shift of 11 nm in relation to the absorption spectrum and narrow bands at 538 e 577 and 624 nm. Increased solubility of PDI-C10 allowed the production of more homogeneous thin films, when compared whit PTCDA, and the application in optoelectronic devices, for instance, as sensing layer for organic vapours. PDI-C10 film produced on glass substrate, by dropcasting method from chloroform solution (0.1 mmol/L), presented sheet resistance of ~14 ± 0,06 kΩ/ . Moreover, in order to produce electrical sensors whose resistance variations can be used to monitor the presence of ethylic alcohol at the atmosphere, the PDI-C10 film was also deposited onto paper substrate containing carbon nanotubes (CN) electrodes. The results indicated an increase of 3% in the electrical resistance upon exposition to ethylic alcohol vapour with proper sensibility, stability and reproducibility.