Tuning of Citrate-Stabilized Laser Ablated Silver Nanoparticles for Glyphosate Detection

The recent advances in nanotechnology can help develop both fast and cost-effective detection techniques to verify if the presence of contaminants in water resources is under safe limits, increasing temporal and geographical test coverage. For a specific analyte, the detection performance of citrate-stabilized silver nanoparticles depends on their chemical affinity, as well as on the ensemble characteristic of the colloid upon its de-stabilization by a mediated aggregation process. This work presents the tuning of citrate-stabilized silver nanoparticles produced by pulsed laser ablation in liquids for glyphosate detection in water. For fixed geometry and laser pulse characteristics, the ablation time, surfactant concentration and interaction pH were studied. The resulting colloidal solutions of silver nanoparticles with glyphosate were interrogated employing optical fiber spectroscopy. Two interrogation techniques which are based on a controlled aggregation of the colloid were used: UV-Vis extinction and Surface Enhanced Raman scattering. Using a calibration curve for low concentrations, the obtained limits of detection for glyphosate in water were 6 μM (1.0 mg/L) and 7.5 μM (1.3 mg/L), respectively.