High-performance eco-engineered uranyl nanocomposite based on Schiff base-modified nanocellulose: from DFT insight to...

Uranyl ions (UO₂ ²⁺) are hazardous to ecosystems and human health due to their toxicity, radiological risks, and persistence in aquatic systems. To detect UO₂ ²⁺ in water with high selectivity, a unique nanocomposite chemosensor (UNS) was developed. A sustainable sensing platform was created by immobilizing 2-(((4-bromophenyl)imino)methyl)naphthalen-1-ol (HM) onto nanocellulose fibers from cotton linters. A simple one-step condensation of 1-hydroxy-2-naphthaldehyde and 4-bromoaniline produced the HM Schiff base ligand, which showed significant coordination affinity for uranyl ions. The UNS exhibited excellent analytical performance, with a rapid response time (90 s), an exceptional detection limit (3.26 ppb), and a linear range (0-0.25 µM), all below WHO limits. The sensor exhibited excellent selectivity for uranyl ions against competing metal ions in complex matrices. Its detection mechanism is based on chelation-mediated spectral shifts, represented as a hyperchromic shift in the UV-visible absorption spectra. The sensor was stable from pH 5.5 to 8.0, and the signal loss changed by less than 10% after regeneration for seven cycles. The use of CNCs as an environmentally friendly support matrix represents a co-benefit by tracking a major pollutant. DFT calculations indicated that uranyl coordination reduced the HOMO-LUMO energy gap from 6.003 to 5.39 eV, which accounted for the observed spectroscopic changes. Collectively, these results establish the UNS as a robust, low-cost, and field-deployable platform for on-site uranyl detection in environmental water monitoring.