Quaternized tetraethylenepentamine-capped AgNPs for selective and rapid colorimetric detection of mercury(II) in water

This work utilized silver nanoparticles (AgNPs) capped with both tetraethylenepentamine (TEPA) and quaternized tetraethylenepentamine (Q-TEPA) as stabilizer and selective recognition element for Hg²⁺ over competing metal ions (Fe²⁺, Fe³⁺, Zn²⁺, Cu²⁺, Pb²⁺, Cr³⁺, Ni²⁺, Cd²⁺, Mn²⁺, As⁵⁺, Co²⁺, Al³⁺, La³⁺). The performance of Q-TEPA-AgNPs was compared to TEPA-AgNPs, demonstrating significantly higher selectivity for Hg²⁺ detection. The effect of Q-TEPA concentration (1 mM, 2 mM, and 4 mM) during the preparation of Q-TEPA-AgNPs on Hg²⁺ selectivity, limit of detection (LOD), and limit of quantification (LOQ) was investigated. LOD and LOQ values of Q-TEPA(1 mM)-AgNPs and Q-TEPA(2 mM)-AgNPs were ~ 10 µM and ~ 31 µM, respectively. However, the linear detection range was wider for Q-TEPA(1 mM)-AgNPs (spanning 20-150 µM) compared to Q-TEPA(2 mM)-AgNPs (20-100 µM). LOD and LOQ of Q-TEPA(4 mM)-AgNPs increased to ~ 20 µM and ~ 60 µM, respectively, with linear range between 20 and 100 µM. Higher concentration of Q-TEPA enhanced Hg²⁺ selectivity but adversely increased LOD and LOQ, and narrowed the linear detection range. The response is rapid: after Hg²⁺ addition the plasmon band disappears within ≤ 12 s, enabling near-real-time visual readout. The nanosensor enabled highly selective Hg²⁺ sensing and functions effectively under real-world conditions, with performance remaining consistent when tested using Hg²⁺ spiked into tap water, confirming robustness against matrix interferences. This optimized Q-TEPA-AgNPs nanosensor offers a promising, selective, and practical approach for mercury detection in complex aqueous environments.