Insights into Local Framework Conformations of pH‐Tunable Electro‐Optic‐Catalytic β ‐Cyclodextrin‐Synthetic Polymer System: Selective Dual‐Mode Sensing and Electrocatalysis of Amino Acids

ABSTRACT

In polymeric system, local framework conformations provide an effective route to generate supramolecular architectures from identical structural units; herein, pH‐tunable realization in electro‐optic‐catalytic semisynthetic‐polymers for dual‐mode fluorogenic‐electrochemical amino acid sensing/ electrocatalysis is reported. Initially, synthetic fluorescent electroactive conducting polymers (FECPs) were synthesized using N , N ‐dimethylacrylamide and cis ‐butenedioic acid through polymerization in an aqueous medium. The optimized FECP3 was modified with β ‐cyclodextrin to rigidify the matrix and fix the orientation of ─C(═O)N/ ─C(═O)OH groups, inducing local framework conformations. Combined computational and pH‐dependent spectroscopic‐electrochemical studies confirmed two local framework conformations in all the β ‐cyclodextrin/FECP3 (LFCFECPs). In optimum LFCFECP2, coexistence of LFCFECP2‐A and LFCFECP2‐B was validated by the excitation‐dependent emission profile and cathodic peaks of C═N ⁺ →C ^• ─N in cyclic voltammogram of LFCFECP2‐A‐/ LFCFECP2‐B‐modified glassy‐carbon electrode (LFCFECP2‐A|GCE/ LFCFECP2‐B|GCE). LFCFECP2‐A and LFCFECP2‐B exhibited pH‐selective dual‐mode sensing, enabling fluorogenic‐electrochemical detection of Tyrosine and Tryptophan in aqueous solution/ cow milk/ soybean extract at pH 6.0 and 8.0, respectively, with rapid response, low detection limits, and high reproducibility. Compared to LFCFECP2‐A|GCE/ LFCFECP2‐B|GCE, LFCFECP2‐A/ LFCFECP2‐B film working‐electrode (WE) displayed a higher electroactive surface area. Therefore, LFCFECP2‐A and LFCFECP2‐B films (WEs) were employed for efficient electrocatalytic conversions of Tyrosine and Tryptophan to Dopaquinone and 3 a ‐hydroxyhexahydropyrrolo[2,3‐ b ]indole‐2‐carboxylic acid with 95.35 and 92.31% conversion efficiencies, respectively.