Mostly of the organic electronic devices are built from synthetic small molecules, conjugated polymers, oligomeric or blended semiconducting materials. Other straightforward approaches include self-organized columnar stacks of aromatic compounds like discotic liquid crystals (DLCs), bent-core molecules and polyaromatic dendrons. Besides the organic π-conjugated classes cited above a quite different alternative has been emerged in the recent years for device fabrication. Vladu, Sariciftci and Bauer called this new class as “exotic” materials and it comprehends biological or bioinspired materials like paper, leather, silk, gelatine, DNA and peptides. The motivation behind the use of such biodegradable materials as substrate, dielectrics or semiconductors is to generate more sustainable and eco-friendly electronics.
In this contribution, we report for the first time the preparation of a hybrid material having (L)-diphenylalanine (Phe-Phe or FF) as biological component and semiconducting polymers (SP) (e.g. P3HT, PFO or PCDTBT) as organic semiconductor. Conventionally, FF nanostructures have been obtained by simple mixing a small amount of highly concentrate (ca. 100 mg/mL) solution of FF in fluorinated solvent (e.g. hexafluoro isopropanol or hexafluoro ethanol) with deionized water (DI). By doing so, FF molecules self-assembly mostly into bundles of nanotubes. Our attempts using the conventional synthesis protocol were fruitless to produce FF nanostructures with SP. To enhance the incorporation of semiconducting polymer and also to get control over the shape and size distribution of FF structures we developed a procedure using ultrasound energy. In a brief, to a solution of FF in 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) was added a stoichiometric amount of SP in 1,2-dichlorobenzene (DCB) and 100 mL of DI water. The process of self-organization initiated spontaneously by ultrasound tip giving rise to FF:P3HT hybrid material as a light-violet precipitated. The temperature was kept at 0-4 °C with an ice-water bath during all the process. After ceased the ultrasound energy application the material was allowed to stand for 8h. The crude product was washed and harvested with centrifugation-redispersion cycles (2265 g) using DCB as solvent. Then, the resulting solid was finally dried in vacuum oven at 60 °C for 24h. The hybrid materials as prepared were fully characterized by SEM, optical microscopy, dynamic light scattering (DLC), circular dichroism (CD), cyclic voltammetry (CV), FT-IR, XRD and thermal gravimetric analysis (TGA).
Those new bio-organic materials have the semiconducting properties of the conjugate polymers while keep the inherent self-organization of biological systems. Benefiting from such synergy high-performance organic electronic devices like OFETs can be envisioned.