Generation of emissive nanosphere from micro-aggregates in anionic perylene diimide: Co-relation of self-assembly, emission, and electrical properties

The comprehension of the controlling factors for the self-assembly and corresponding nanostructure formations are very necessary to elucidate the structure-property relation in semiconducting organic molecules. Herein, we are reporting the successful tuning of the self-assembly property and emission behavior of anionic perylene diimide molecule, disodium salt of N,N '-bis(4-benzosulfonic acid)perylene-3,4,9,10-tetracarboxylbisimide (PSA) using a simple solvent-induced technique. The emission enhancement of anionic PSA is revealed with the addition of miscible polar solvents like ethanol, tetrahydrofuran, or dimethyl sulfoxide with water. The lowering of aggregation in the mixed solvent is demonstrated using UV-Vis and photoluminescence studies. The solvent tuneable different assembled structures in water and the mixed solvent were further confirmed by nuclear magnetic resonance (NMR), X-ray diffraction (XRD), dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), confocal microscopy, and time-correlated single-photon counting (TCSPC) techniques. Alongside the spectroscopic changes, FESEM reveals the change of assembly morphology from highly ordered micro-rod structure in water to homogeneous nanosphere. Furthermore, experimental results of solventinduced tuneable self-assembly are validated by computational simulation study which elucidates the feasible dimer formation in water and that is not thermodynamically favorable with increasing the ethanol percentage in water. The micro-rods show superior semiconducting characteristics to the nanosphere as investigated by the I-V characteristic due to the extended percolating pathway.

Automated summary

The study focuses on controlling the self-assembly and emission behavior of the anionic perylene diimide molecule PSA through solvent tuning, with the addition of miscible polar solvents resulting in enhanced emission. Various techniques were used to confirm the reduction of aggregation in mixed solvents, with FESEM revealing changes in assembly morphology.