Polythiophene-g-poly(methacrylic acid) and perylene diimide appended peptide conjugates with tuneable photoluminescence, OMEIC, and photo-switching properties

Abstract

A water-soluble polymer–peptide conjugate, composed of poly(thiophene methacrylate) (PTMA) and cationic peptide appended perylene diimide (PBI-NH₃⁺), was fabricated. The dipolar interaction between PTMA and PBI-NH₃⁺ helped to uncoil the polythiophene backbone, resulting in an increase of the conjugation length, which was thoroughly studied by UV-Vis, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) spectra. The morphology of PTMA changes from vesicular to a highly entangled fibrillar network in the hybrid as evident from the HR-TEM study. Fluorescence spectroscopic study and time-correlated single-photon counting (TCSPC) studies were made to understand the effect of interaction on the photoluminescence (PL) properties of the hybrid. The current–voltage (I–V) plots of hybrid materials showed synergistic enhancement of current with voltage, showing an interesting organic mixed ionic and electronic conductivity (OMIEC) property, which was further supported through current–time (I–t) and Nyquist plot results. This conjugate material shows an enhancement of photo-switching behaviour with the highest photocurrent gain of 9. 8 (I_on/I_off) for the composite with 27 wt% PBI-NH₃⁺. The increase in photoswitching property is attributed to efficient charge (electron–hole) separation and holds a future promise for fabricating new types of macromolecular OMIEC systems along with excellent photocurrent switching efficiency.