Development of Hexylpectinamide‐Grafted Poly(Ethylene Glycol) Dimethacrylate Hydrogels Loaded With Nitrogen–Carbon Quantum Dots for Controlled Nutrient Release

ABSTRACT The development of slow‐release fertilizers face challenges such as biodegradability, irrigation, and poor soil retention. Hydrogels act as efficient carriers that improve plant growth and soil quality. Nitrogen–carbon quantum dots (N‐CQD) serve as promising nano‐fertilizers because nitrogen‐containing amine and amide groups gradually hydrolyze and degrade microbially, releasing bioavailable nitrogen species (NH 4 + , NO 3 − ). Their photoluminescence converts UV/blue light into wavelengths usable by chloroplasts, enhancing photosynthesis, though rapid soil loss requires controlled release. In this study, N‐CQD is entrapped in hexylpectinamide‐g‐poly(ethylene glycol) dimethacrylate hydrogels (HPPD N‐CQD ) for sustained release. Hexylpectinamide (HP) synthesis is confirmed by FTIR, 1 H and 13 C NMR, while crosslinking with N, N′‐methylenebisacrylamide (MBA), and poly(ethylene glycol) dimethacrylate (PD) is verified by the disappearance of C=C peaks. N‐CQD incorporation is confirmed by characteristic peaks. XRD shows amorphous structures, and DSC reveals increased endothermic temperature with N‐CQD inclusion. HPPD retains less water than pectin hydrogel (PPD), while N‐CQD enhances swelling in ultrapure water but restricts it at pH 4. Rheology shows higher storage modulus ( G ′) in HPPD, reduced when N‐CQD is entrapped. PPD N‐CQD releases faster than HPPD N‐CQD , indicating more sustained release behavior in the latter. These results demonstrate tunable physicochemical properties of HP‐based hydrogels for controlled nutrient release in sustainable agricultural applications.