Development of Organic Mixed Ion–Electron Conductive and Photoresponsive Property in a Peptide Linked Boronic Acid Conjugated Naphthalimide Derivative

The investigation of organic mixed ion electronic conductivity and photoswitching behavior of the organic chromophoric moiety is quite challenging and attractive to the scientific world. Herein, we have vividly demonstrated the effect of peptide-appended naphthalimide-conjugated boronic acid (PNP) upon exposure to tetrabutyl ammonium fluoride (TBAF) and the formation of radical anions in the system. TBAF reduces PNP to generate radical anions. The generated radical anions play the pivotal role in the enhancement of transport properties of the PNP. At nanomolar concentrations (2 nM) of fluoride ions, dark current is 5 × 10 –7 A, whereas at micromolar levels (2 μM), current has been increased to 1.2 × 10 –6 A at +5 V. Subsequently, current increases to 3 × 10 –5 A with millimolar concentration (2 mM) of fluoride ions at +5 V. Interestingly, the increase in concentration of fluoride ions causes an increment of the current. Moreover, the current–voltage ( I – V ) data show the organic mixed ionic and electronic conductivity (OMIEC) characteristics. The current–time ( I – t ) and Nyquist studies supported the properties of the OMIEC in the system. The material also exhibited good photoswitching properties, achieving the highest photocurrent gain ( I on / I off ) of 5.2 at millimolar fluoride ion concentration, at +5 V. The efficient photoswitching behavior are obtained due to charge–hole separation. This work offers a promising platform for developing a material for use in OMIEC systems.