Abstract
Screen-printed carbon nanofiber electrodes (SPCNFEs) represent an alternative with great acceptance due to their results, as well as their low impact on the environment. In order to improve their performance, in the present work they were modified with silver nanoparticles (Ag-NPs) and electrochemically characterized by using anodic stripping voltammetry. From the Ag-NP synthesis, silver seeds (Ag-NS) and silver nanoprisms (Ag-NPr) were obtained. The Ag-NP formation was confirmed by micrographs, where Ag-NPs with diameters of 12.20 ± 0.04 nm for Ag-NS and 20.40 ± 0.09 nm for Ag-NPr were observed. The electrodes were modified by using three different deposition methods—drop-casting, spin-coating, and in situ approaches—that offer different nanoparticle distribution and electrode modification times. It was observed that the last methodology showed a low amount of Ag-NS deposited on the electrode surface and deep alteration of this surface. Those facts suggest that the in situ synthesis methodology was not appropriate for the determination of heavy metals, and it was discarded. The incorporation of the nanoparticles by spin-coating and drop-casting strategies showed different spatial distribution on the electrode surface, as proved by scanning electron microscopy. The electrodes modified by these strategies were evaluated for the cadmium(II) and lead(II) detection using differential pulse anodic stripping voltammetry, obtaining detection limit values of 2.1 and 2.8 µg·L−1, respectively. The overall results showed that the incorporation route does not directly change the electrocatalytic effect of the nanoparticles, but the shape of these nanoparticles (spherical for seeds and triangular for prisms) has preferential electrocatalytic enhancement over Cd(II) or Pb(II).
Highlights
In order to ensure water quality, the World Health Organization (WHO) has published the maximum allowed concentration of pollutants in drinking water [1]
Ag-NSof each type of was monitored by electron microscopy was used in the SPCNFEs, that the modification methodology would not be a determinant factor in the enhancement characterization of their size, shape, and distribution on the of the response of the electrodes
Three different deposition methodologies in situ, drop-casting, and spin-coating regressions and wider linear ranges in the case of Pb(II) calibrations, while for Ag nanoprisms (Ag-NPr) electrodes have been evaluated as feasible strategies for the modification of screen-printed carbon nanofiber better results were obtained for the Cd(II) response
Summary
In order to ensure water quality, the World Health Organization (WHO) has published the maximum allowed concentration of pollutants in drinking water [1]. As, Cr, Hg, Pb, and Cd concentrations must be under 10, 50, 1, 10, and 3 μg·L−1 , respectively [1] Such low values need to be determined by means of highly sensitive techniques, such as flameless atomic adsorption spectrophotometry (FAAS) [2], inductively coupled plasma optical emission spectroscopy (ICP-OES) [3], and inductively coupled plasma mass spectrometry (ICP-MS) [4], among others; these require expensive equipment and specialized technicians. These facts increase both the analysis time and the operation costs. Regarding the determination of HMI, the improvement of the electrochemical performance and sensitivity to HMI are required
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