Probing the pH‐Induced Spectral Modifications of NSAIDs for Designing Molecular Logic Gates and Combinational Logic Circuits

The current paper investigates the absorption and emission spectra of two non‐steroidal anti‐inflammatory drugs (NSAIDs), acetaminophen (N4HPA) and diclofenac (2DAPA), in aqueous solutions across different pH values. Both molecules exhibit significant changes in absorption and fluorescence spectra as a function of pH, which are attributed to the existence of these molecules in different forms (uncharged, anionic, and cationic) based on pH. The interpretation of these pH‐dependent spectral behaviors in the presence or absence of the chemical inputs offers the possibility for the realization of a variety of unimolecular logic circuits, which are able to perform combinational logic operations. In this study, we aimed to implement two‐input logic gates, namely, implication (IMP), inhibit (INH), and XNOR, using chemical inputs (H + and OH − ) and spectroscopic signals as outputs. Additionally, we have explored the design possibility of combinational logic circuits, namely, digital magnitude comparators and half‐subtractor, by judiciously selecting positive or negative logic conventions for one or more output channels.