Sequentially Synthesized Dual-State Dual-FRET Optoelectronic Polymer-Thiolated Collagen Nanohybrids for Ultra-High S^2–/ Cd(II) Relay Sensing and Electrocatalytic Nitrobenzene Reduction

This work reports the strategic development of state-of-the-art optoelectronic nanohybrid polymers for high-performance fluorogenic S 2– /Cd(II) relay-sensing and electrocatalytic reduction of nitrobenzene (NB) to aniline. Initially, amino-graphene oxide (AGO)-incorporated conductive fluorescent polymers (AGO-CFPs) are fabricated using N, N -dimethylacrylamide to explore the roles of AGO-nanoparticle in governing fluorescence resonance energy transfer (FRET) and enhancing reduction efficacy of the optimum AGO3-CFP. To further enhance the FRET efficacy and lower open circuit potential (OCP), AGO3-CFP is modified using thiolated collagen having amidic subfluorophores, redox-active cysteine, and hydrophilic proton-conduction channels. The as-fabricated dual-state dual-FRET-active optimum AGO- and thiolated collagen-containing conductive fluorescent polymer (AGO3-CCFP2) is employed for trace-level S 2– /Cd(II) relay-sensing and electrocatalytic NB reduction. To further increase the electrocatalytic efficacy, AGO3-CCFP2 is sequentially modified to AGO3-CCFP2(I) and AGO3-CCFP2(II) by adding S 2– and Cd(II), respectively. Here, stepwise lowering of the OCP from 0.76 V (AGO3-CFP) to −0.13 V (AGO3-CCFP2(II)) renders enhanced NB to aniline conversion from 92.6% to 98.5% (DMSO)/92.1% to 96.5% (H 2 O), indicating the utility of the adopted strategy toward sequential synthesis of AGO-CFPs → AGO3-CCFPs → AGO3-CCFP2(I) → AGO3-CCFP2(II). The stability, selectivity-sensitivity, reversibility-reusability, low responsetime/LODs, complete NB conversion, and very high percentage aniline formation confirm much better sensing and electrocatalytic performances of these nanohybrid polymers compared to reported sensors/electrocatalysts.