Polymer vs Polyphenol Aqueous Biphasic Systems in the Extraction of Fe-Tannic Acid Nanocomposites and Sensing of H ₂ O ₂

Two polyphenols, tannic acid (TA) and gallic acid (GA), were introduced as aqueous phase-forming components. Three aqueous biphasic systems (ABSs) composed of polymers (PEG#6000, PPG#400, PEG-PPG-PEG block copolymer) against aqueous solutions of these polyphenols were generated. The phase diagrams were constructed using the node determination method at three different temperatures, with the corresponding binodal graphs using the Merchuk equation. The reducing and stabilizing properties of TA in the synthesis of Fe-TA nanocomposites, with manifold biological functionalities, were also explored. The newly designed PEG/TA biphasic system was used to extract this Fe-TA nanocomposite at different pH values and found to be maximum at pH 3. The polymer-rich phase of the PEG/TA biphasic system with prior addition of the Fe-TA nanocomposite was further utilized for H2O2 sensing using kinetic spectrophotometric studies, which was not observed in pure aqueous or pristine PEG media. The calibration curve depicted a good linear range from 145.1 to 361.9 nM with a limit of detection (LOD) and limit of quantification (LOQ) of 90.06 and 272.9 nM, respectively. The mechanism behind the sensing was also explored using dynamic light scattering (DLS) measurements, FTIR spectroscopy, and isothermal calorimetric (ITC) studies, and was found to be due to reverse micelle formation in the PEG-rich phase.