Abstract
This work utilized silver nanoparticles (AgNPs) capped with both tetraethylenepentamine (TEPA) and quaternized tetraethylenepentamine (Q-TEPA) as stabilizer and selective recognition element for Hg(2+) over competing metal ions (Fe(2+), Fe(3+), Zn(2+), Cu(2+), Pb(2+), Cr(3+), Ni(2+), Cd(2+), Mn(2+), As(5+), Co(2+), Al(3+), La(3+)). The performance of Q-TEPA-AgNPs was compared to TEPA-AgNPs, demonstrating significantly higher selectivity for Hg(2+) detection. The effect of Q-TEPA concentration (1 mM, 2 mM, and 4 mM) during the preparation of Q-TEPA-AgNPs on Hg(2+) 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 Hg(2+) selectivity but adversely increased LOD and LOQ, and narrowed the linear detection range. The response is rapid: after Hg(2+) addition the plasmon band disappears within ≤ 12 s, enabling near-real-time visual readout. The nanosensor enabled highly selective Hg(2+) sensing and functions effectively under real-world conditions, with performance remaining consistent when tested using Hg(2+) 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.