“Development of a sulfamethoxazole-based azo dye chemosensor and dye-functionalized TiO2 nanosensor for rapid and selective colorimetric detection of Hg²⁺ ions” (2026), by Ali Dadellahi et al. Chemistry research paper. Original abstract below, unchanged. A free PDF is available.

Development of a sulfamethoxazole-based azo dye chemosensor and dye-functionalized TiO2 nanosensor for rapid and selective colorimetric detection of Hg²⁺ ions

Ali Dadellahi, Asadollah Mohammadi · November 4, 2026 · Chemistry

Abstract

A novel sulfamethoxazole-based azo dye was synthesized as a molecular chemosensor and subsequently immobilized onto TiO₂ nanoparticles to fabricate a nanosensor for the selective colorimetric detection of Hg²⁺ ions. The synthesized chemosensors were comprehensively characterized by FT-IR, NMR, XRD, EDX, and FE-SEM analyses. Their sensing performance was evaluated using naked-eye detection and UV-Vis spectroscopy. Both chemosensors exhibited a distinct color change from yellow to orange upon exposure to Hg²⁺, enabling rapid visual detection with high selectivity over competing metal ions. Job’s plot confirmed a 1:1 binding stoichiometry, while the binding constant was determined to be 2.82 × 10 4 M − ¹. The molecular chemosensor showed a lower detection limit (0.37 µM) than the nanosensor (3.11 µM). Moreover, the Hg²⁺ recognition process was reversible, allowing repeated sensing without significant loss of performance. In addition, both the molecular chemosensor and nanosensor exhibited antibacterial effects against Gram-positive and Gram-negative bacteria. Owing to their selective detection ability, satisfactory sensing performance, reusability, and antibacterial effects, the developed chemosensors represent promising candidates for Hg²⁺ detection in aqueous solutions.

Free PDF DOI: 10.1038/s41598-026-79190-x