Exploration of an Organic Mixed-Ion Electronic Conductor by a Peptide-Appended Naphthalene Diimide-Based Photoresponsive Hydrogel

Abstract

Organic soft material-based mixed-ion electronic conductors (MIECs) have nowadays emerged as an important class of material due to their immense use in many electronic fields. In this study, we report a peptideappended naphthalene diimide-based (NDIP) thermoresponsive, mechanosensitive, and photoresponsive hydrogel in the phosphate buffer medium at the physiological pH (7.46), which also shows MIECs properties in the assembled state. The UV−visible study has revealed the J type of aggregation of this NDIP molecule in the gel state. The aggregation-induced emission is clearly evident from the photoluminescence spectra in the molecularly aggregated state. Aggregation of peptide-based molecules in the gel state leads to the formation of supramolecular polymeric nanofibers that can be caused by the electronic conduction of the dried gel state. Moreover, the Na + ions inside the polymeric fiber network of the gel, which are mainly sourced from the sodium phosphate salt of the buffer, show ionic conductance along with the electronic conductance of the NDIP. The synergistic effect of both conductivities has made the aggregated gel system a perfect agent of organic mixed-ion electronic conducting (OMIEC) material. Moreover, the OMIEC nature of the dried gel has been well understood by several electronic techniques such as current− voltage (I−V), current−time (I−t), and Nyquist plot. The perfect stacking of the π-conjugated core of the naphthalene-based gelator in the gel state has shown good photoresponsive behavior by switching "on" and "off" the white light illumination. A stable photocurrent gain with an I on /I off value of 5.58 has been found in the aggregated dry gel state, indicating a potential photoswitching property of the system.

Bicomponent Fluorescent System Composed of Peptide-Substituted Naphthalenediimide and Carbon Dots as Nanothermometer

“…Naphthalene dianhydride (NDA) is one of the important π-conjugated organic molecules among the rylene dyes . The endowed physical properties including molecular planarity, air stability, chemical robustness, and high π-acidity make NDA a promising candidate in diverse research fields like organic light-emitting diodes (OLED), photovoltaic devices, solar cells, field effect transistors, bioprobes, and others. − Functionalization with the peptides at the periphery of NDA leads to the formation of peptide-appended imide and core-substituted naphthalenediimides (NDIs and c-NDIs). − The incorporation of a peptide may facilitate tuning of the self-assembling property of NDIs using the H-bonding interactions of the CO-NH group of the peptide. − Depending on the electron-donating capability of a functional group at the core position of NDIs, a rainbow collection of fluorescent c-NDI can be obtained . The c-NDIs possess high fluorescence quantum yield and cover the absorption span over the entire visible range .…”