Nanopartículas de prata sintetizadas por Turnera subulata Sm. e sua aplicação como sensor colorimétrico para a detecção de íons metálicos em água

Abstract

This work addresses the green synthesis of silver nanoparticles (AgNPs) using an aqueous extract from the leaves of the plant Turnera subulata Sm., investigating their potential as a colorimetric sensor for the selective detection of metallic ions in water. The synthesis of TS-AgNPs was confirmed by UV-vis spectroscopy, showing a surface plasmon resonance peak at 414 nm, as well as TEM and DLS analyses, which revealed spherical morphology, an average size between 10 and 30 nm, and a bimodal distribution. The high zeta potential (-48 mV) demonstrated excellent colloidal stability, essential for preventing aggregation and preserving particle properties. The stability of the AgNPs was evaluated under three experimental conditions: over 60 days, at different saline concentrations, and pH variations. The results validated the ability of TS-AgNPs to remain stable under adverse conditions. Regarding selectivity, the sensor showed high specificity for Hg²⁺, evidenced by perceptible color changes to the naked eye and significant absorbance alterations. The calibration curve revealed excellent linearity (R² = 0.98), with detection (LOD) and quantification (LOQ) limits of 0.31 ppm and 1.03 ppm, respectively. Tests conducted in complex matrices containing multiple metallic ions demonstrated that the sensor maintained its specificity even in the presence of potential interferents, highlighting its robustness and applicability under real conditions. Additionally, kinetic studies showed the rapid interaction between the nanosensor and Hg²⁺, with a total reaction time of less than 1.5 minutes. In summary, the results obtained confirm the applicability of TS-AgNPs as a colorimetric sensor, offering high selectivity, stability, robustness, and speed in detecting mercury ions. This work not only contributes to advancing green methodologies but also highlights the potential application of biosynthesized nanoparticles in environmental monitoring technologies.