Mechanical, adsorption and detection properties of functionalized N-CQDs/P(AM-U-ChCl) composite hydrogels

Abstract

In this paper, nitrogen-doped carbon quantum dots (N-CQDs) were prepared by using citric acid as a carbon source and ethylenediamine as a nitrogen source. Then, N-CQDs were added into a deep eutectic solvent (DES) synthesized from acrylamide (AM), urea (U), and choline chloride (ChCl). The N-CQDs/P(AM-U-ChCl) composite hydrogels were prepared by light polymerization. The chemical composition and microstructure of N-CQDs/P(AM-U-ChCl) composite hydrogels were characterized in detail using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). This article further explored the influence of the content of N-CQDs on the mechanical properties, adsorption properties, and detection performance of the composite hydrogel. The results showed that the composite hydrogels exhibited the best mechanical properties when N-CQDs' content was 0.3 wt%. The adsorption performance of N-CQDs/P(AM-U-ChCl) composite hydrogels for Fe³⁺ was significantly enhanced due to the carboxyl groups contained in N-CQDs. In detecting tert-butylhydroquinone (TBHQ), the composite hydrogel showed a good linear correlation in the concentration range of 0–200 mg L⁻¹, and the detection limit of TBHQ reached 0.849 mg L⁻¹. This study provides a new idea for preparing composite hydrogel materials with excellent mechanical properties and functionality. Also, it demonstrates their potential application value in heavy metal ion adsorption and organic molecule detection.