Investigation of pressure response, adsorption performance, and detection capability of multifunctional P(AM-Gly-ChCl)/N-CQDs composite hydrogels

Abstract

In this work, nitrogen-doped carbon quantum dots (N-CQDs) were successfully synthesized via a microwave-assisted route using citric acid and o-phenylenediamine as precursors. A deep eutectic solvent was subsequently constructed using choline chloride as the hydrogen bond acceptor and glycerol/acrylamide as hydrogen bond donors. The N-CQDs were introduced as functional nanofillers, and a P(AM-Gly-ChCl)/N-CQDs composite hydrogel was obtained through photopolymerization. The chemical composition and microstructure of the composite hydrogel were systematically characterized by SEM, XPS, and FTIR, verifying the effective incorporation of N-CQDs into the hydrogel network. The effect of N-CQDs content on the mechanical, sensing, and adsorption properties of the hydrogel was elucidated. With increasing N-CQDs content, both tensile fracture stress and tear energy were substantially improved. The composite hydrogel exhibited an enhanced pressure-sensitive response, with a relative capacitance change of 137.0% achieved at an applied load of 1 N for the hydrogel containing 0.3 wt% N-CQDs. In addition, incorporation of N-CQDs endowed the hydrogel with effective Fe³⁺ adsorption capability and pronounced fluorescence quenching behavior, highlighting its potential for multifunctional applications that integrate pressure sensing and metal-ion detection.