Title
Solvent Directed Morphogenesis and Electrical Properties of a Peptide-Perylenediimide Conjugate
Author
Sahnawaz Ahmed, Kandan Natarajan Amba Sankar, Bapan Pramanik, Kallol Mohanta, Debapratim Das
Year
2018
Journal
Langmuir
Abstract
Molecular organization of electron-deficient aromatic systems like perylenediimides (PDI) is extremely appealing, as they are potential candidates for organic electronics. Performance of these molecules in such applications primarily depends on the self-organization of the molecules. However, any correlation between the morphology of these self-assembled semiconducting molecules and their electrical performances have not yet been formulated. Herein, for the first time, we have made an effort to find such a correlation by studying the self-assembly, morphology and their conducting properties for a peptide-PDI conjugate. The PDI-conjugate formed fiber like morphology in relatively non-polar solvents (THF and CHCl3) while in more polar solvents (HFIP, MeOH, CAN, Acetone), spherical morphology could be found. Interestingly, the self-assembly and the morphologies showed clear dependence on the solvent polarity. In polar solvents, the conjugate aggregates more efficiently than in the non-polar solvents and with decrease in solvent polarity, the dimension of the nano-structures increased. However, in all the tested solvents, irrespective of their polarity, the PDI-peptide conjugate adopts a right handed helicity. To find a correlation between the morphologies with the conducting property, detailed electrical characterization of these nano-structures were carried out. While no significant change could be observed for the dc conductivities of these nano-structures, the ac conductivities show prominent difference at low frequency region. A dispersion of conductivity was observed for the nano-spheres due to polarization effect. A critical correlation between the nano-structures and the activation energy was observed as with decrease in radii of curvature of the aggregates the activation energy increases with an exception in case of MeOH. The observed results suggests that the long range transport of charge carriers is less favorable when the aggregates are small and closely packed.
Instrument
J-1500
Keywords
Circular dichroism, Cotton effect, Chemical stability, Aggregation, Nanostructures, Materials