Development of Organic\nMixed Ion–Electron Conductive\nand Photoresponsive Property in a Peptide Linked Boronic Acid Conjugated\nNaphthalimide Derivative

The investigation of organic mixed ion electronic conductivity\nand photoswitching behavior of the organic chromophoric moiety is\nquite challenging and attractive to the scientific world. Herein,\nwe have vividly demonstrated the effect of peptide-appended naphthalimide-conjugated\nboronic acid (PNP) upon exposure to tetrabutyl ammonium fluoride (TBAF)\nand the formation of radical anions in the system. TBAF reduces PNP\nto generate radical anions. The generated radical anions play the\npivotal role in the enhancement of transport properties of the PNP.\nAt nanomolar concentrations (2 nM) of fluoride ions, dark current\nis 5 × 10<sup>–7</sup> A, whereas at micromolar levels\n(2 μM), current has been increased to 1.2 × 10<sup>–6</sup> A at +5 V. Subsequently, current increases to 3 × 10<sup>–5</sup> A with millimolar concentration (2 mM) of fluoride ions at +5 V.\nInterestingly, the increase in concentration of fluoride ions causes\nan increment of the current. Moreover, the current–voltage\n(<i>I</i>–<i>V</i>) data show the organic\nmixed ionic and electronic conductivity (OMIEC) characteristics. The\ncurrent–time (<i>I</i>–<i>t</i>)\nand Nyquist studies supported the properties of the OMIEC in the\nsystem. The material also exhibited good photoswitching properties,\nachieving the highest photocurrent gain (<i>I</i><sub>on</sub>/<i>I</i><sub>off</sub>) of 5.2 at millimolar fluoride\nion concentration, at +5 V. The efficient photoswitching behavior\nare obtained due to charge–hole separation. This work offers\na promising platform for developing a material for use in OMIEC systems.