Synthesis of Polymer Nanohybrids for Glycerol Sensing, Fluorometric Viscosity Detection, and Metal-Free Electrocatalytic Glycerol Oxidation

This research provides a constructive approach for developing high-performance polymer nanohybrids toward enhancing optoelectronic properties, fluorogenic viscosity sensing, and metal-free electrocatalytic oxidation of glycerol to value-added organic(s). Herein, reduced graphene oxide (RGO) and mildly oxidized RGO (MRGO) are strategically combined with fluorescent electroactive polymers (FEPs) to develop a promising sustainable metal-free electrocatalytic system suitable for amplifying opto-electrochemical properties, multiplatform sensing capacity, and electrocatalytic efficiency. The optimized polymeric counterpart (FEP2) promotes dual-state emission in the supramolecular network of RGO-/MRGO-incorporated fluorescent electroactive hybrid polymers (RFEHPs/MFEHPs) through physicochemically confined atypical electron-rich -C(═O)NH-/-C(═O)O-/-SO₃H fluorophores of (hydroxyethyl)methacrylate and 2-acrylamido-2-methylpropane-1-sulfonic acid monomers. The photophysical processes of the spectroscopically optimized RFEHP1 and MFEHP3 are well explored in the solid state and in solution in order to employ them in viscosity-dependent turn-on fluorogenic detection of mono-/di-/trihydric alcohol in aqueous medium. Again, redox-active O-containing functional groups of FEP2 and RGO/MRGO impart strong electroactivity and substantial electrical conductivity to RFEHPs/MFEHPs. Subsequently, electrochemically optimized RFEHP1 and MFEHP3 are applied to fabricate GCE-RFEHP1 and GCE-MFEHP3 electrodes having maximum open-circuit potentials (1.30 and 1.32 V vs Ag/AgCl) to deliver the glycerol electro-oxidation reaction (GLYOR) in water medium. In the GLYOR, peaks at 1.18 and 1.42 V vs Ag/AgCl for GCE-RFEHP1 indicated the formation of two-/three-carbon-containing glycolate/glycerate along with a significant amount of formate. However, the sole anodic response at 1.42 V vs Ag/AgCl for GCE-MFEHP3 signifies a higher-degree GLYOR producing formate as the major product. The formation of these GLYOR products is confirmed by NMR spectral analyses. Therefore, optoelectrochemically active RFEHP1 and MFEHP3 are implemented in selective and sensitive fluorogenic, voltammetric, and impedimetric sensing of glycerol with appreciably low detection limits. In addition to such multiplatform sensing, high stability and reproducibility of GCE-RFEHP1 and GCE-MFEHP3 electrodes pave way for efficient execution of the metal-free electrocatalytic GLYOR.