Engineering luminescent pectin-based hydrogel for highly efficient multiple sensing

Abstract

Luminescent hydrogels with sensing capabilities have attracted much interest in recent years, especially those responsive to stimuli, making such materials potential for various applications. Pectin is a high-molecular-weight carbohydrate polymer that has the ability to form hydrogel upon heating or mixing with divalent cations. However, intrinsic pectin gels are weak and lack of functionalities. In this study, lanthanide ions and silk fibroin derived carbon dots were incorporated into Pectin/PVA hydrogel (PPH) to form luminescent tough hydrogels. The luminescence of the hydrogel can be tuned by adjusting the ratio of blue emission carbon dots to Eu³⁺ ions (red emission) and Tb³⁺ ions (green emission). Such incorporation of emitters only slightly changed the mechanical properties of the tough hydrogel. Notably, the luminescent Pectin/PVA hydrogel (LPPH) showed chromic response to external stimuli, like pH and metal ions. By measuring the ratio of luminescent intensity at 473 nm and 617 nm (I₄₇₃/I₆₁₇), the pH response can be quantified in high sensitivity. In addition, the specific detection of Cu²⁺ and Fe³⁺ ions using the fabricated hydrogel were demonstrated, the mechanism was also proposed. The different chromic responses to Fe²⁺ and Fe³⁺ endow the luminescent tough Pectin/PVA hydrogel potential for multiple sensing applications.

Keywords: Chromic response; Integrated luminescent emitters; Pectin hydrogel; Sensing application; Stimuli-responsive.