PERSONAL DE APOYO
AGUIRRE Maria Del Carmen
congresos y reuniones científicas
Título:
Cu and Ag nanostructures electrodeposited onto carbon substrates for glyphosate quantification
Autor/es:
AGUIRRE MARIA DEL CARMEN; URRETA SILVIA E; BERCOFF PAULA G; CESAR G GOMEZ
Lugar:
Buenos Aires
Reunión:
Encuentro; XIX Encuentro de Superficies y Materiales Nanoestructurados?NANO2019; 2019
Institución organizadora:
CNEA-centro Atomico Constituyentes
Resumen:
Cu and Ag nanostructures are prepared for electrochemical detection of a widely-used herbicide, such as glyphosate (Glyp). In the case of Cu0 nanostructures, they are electrocrystallized onto glassy carbon (GC) surface, at a potential of -0.6 V. It is found that the deposition process involves a 3D progressive nucleation with a diffusion-controlled growth. At short deposition times, round copper nanoparticles (16 nm), forming islands develops on the substrate surface. At longer times, agglomerates of about 200 nm, consisting of round and faceted nanoparticles near 16-50 nm in size, evidencing that nucleation is progressive during the deposition process. For Ag0 nanostructures obtained at potentials of +0.2 V and +0.3 V onto graphite surface (G), a 3D instantaneous nucleation mechanism and diffusion-controlled growth is determined from the current-time transients. The morphology of these nanoparticles (dendritic and cubic, of 100 nm) is consistent with the mechanisms proposed.Different electro-active systems are formed by combining the nanostructures synthesized in background electrolytes of pH 6, containing the metallic ions (Cu2+ or Ag+). In these systems (Cu2+-Cu/GC or Ag+- Ag/G), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are applied to Glyp determination. Interestingly, during the DPV the electrode is regenerated in situ in each determination cycle. A remarkable phenomenon is detected with Cu/GC electrode immersed in presence of ions Cu2+, when glyphosate is added. For an oxidation potential of -0.015 V (vs Ag/AgCl) of the Cu0/Cu+ couple, the current peak is sensitively affected by glyphosate concentration. This effect is related to the formation of a barrier of adsorbed glyphosate molecules onto copper surface, which prevents Cu2+ ions diffusion towards the electrode's surface. The Cu2+-Cu/GC electroactive system allowed a very low detection limit (LOD) for Glyp of (0.186 ± 0.004) μM (31ppb). Glyp determinations with the Cu2+-Cu/GC system in presence of cationic interferers, and in drinking water exhibited similar sensitivity and stability that found for the pure system.DPV was also applied to Ag/G electrode in order to quantify Glyp in absence and in presence of Ag+ ions in a 0.1 M KNO3 solution of pH 6. Optimal herbicide detection properties are found at +0.45 V ( vs Ag/AgCl) in connection with the electroactive Ag+-Ag/G system, generated in situ. This sensor yielded a detection limit (LOD) of (0.52 0.02) M (90 ppb).