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 peptide-appended 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 pi-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.
