Bifunctional Polymer-Metal Nanocomposite Ion Exchange Materials

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CdS quantum dots as a scattering nanomaterial of carbon nanotubes in polymeric nanocomposite sensors for microelectrode array behavior

This work is focused on evaluating the direct electrochemical effect of semi-conducting nanocrystals when they are integrated in bulky nanocomposite sensors based on multiwalled carbon nanotubes (MWCNTs). For this aim, MWCNTs have successfully been functionalized with CdS quantum dots (CdS–QDs@MWCNTs) and then dispersed within an insulating polymeric matrix, as epoxy resin, for electroanalytical sensing purposes. After an accurate voltammetric and impedimetric characterization, some electrochemical parameters were surprisingly enhanced regarding the non-modified sensors, such as peak current height, electroactive area, and emphasizing the double-layer capacitance. These results can be explained since CdS–QDs confer to the nanocomposite sensor a microelectrode array behavior, dispersing the conductive microzones through the polymeric matrix, as revealed by morphological experiments. The feasibility of this approach was amperometrically evaluated for ascorbic acid and hydrogen peroxide, both used as reference analytes. Electroanalytical results demonstrated that this approach provides to the CdS–QDs-modified nanocomposite sensors the capability to determine low concentrations of analytes and improved sensitivities.Peer ReviewedPostprint (author's final draft

Strategies for surface modification with Ag-shaped nanoparticles: electrocatalytic enhancement of screen-printed electrodes for the detection of heavy metals

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)Postprint (published version

Direct As(V) Determination Using Screen-Printed Electrodes Modified with Silver Manoparticles

Carbon-nanofiber-based screen-printed electrodes modified with silver nanoparticles (Ag-NP-SPCNFEs) were tested in a pioneering manner for the direct determination of As(V) at low µg L–1 levels by means of differential pulse anodic stripping voltammetry. Screen-printed electrodes were modified with two different types of Ag-NPs, nanoseeds (NS), and nanoprisms (NPr) and characterized both microscopically and electrochemically. Furthermore, after optimizing the direct voltammetric determination of As(V), the analytical performance of considered sensors was compared for the direct determination of As(V). These results suggest that Ag-NS offer a better analytical response compared to Ag-NPr, with a detection and quantification limit of 0.6 and 1.9 µg L–1, respectively. The proposed methodology was validated using a spiked tap water sample with a very high reproducibility and good agreement with inductively coupled plasma - mass spectrometry (ICP-MS) measurementsPeer ReviewedPostprint (published version

Ecologically Friendly Polymer-Metal and Polymer-Metal Oxide Nanocomposites for Complex Water Treatment

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Galvanic replacement induced electromotive force to propel Janus micromotors

Electrochemistry is a highly versatile part of chemical research which is involved in many of the processes in the field of micromotion. Its input has been crucial from the synthesis of microstructures to the explanation of phoretic mechanisms. However, using electrochemical effects to propel artificial micromotors is still to be achieved. Here, we show that the forces generated by electrochemical reactions can not only create active motion, but they are also strong enough to overcome the adhesion to the substrate, caused by the increased ionic strength of the solutions containing the ions of more noble metals themselves. The galvanic replacement of copper by platinum ions is a spontaneous process, which not only provides a sufficiently strong electromotive force to propel the Janus structures but also results in asymmetric Pt-hatted structures, which can be further used as catalytic micromotorsPeer ReviewedPostprint (published version

Carbon/polymer nanocomposite (Bio)sensors containing nanoparticles: functionalization and applications

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Customized In situ functionalization of nanodiamonds with nanoparticles for composite carbon-paste electrodes

The incorporation of nanomaterials on (bio)sensors based on composite materials has led to important advances in the analytical chemistry field due to the extraordinary properties that these materials offer. Nanodiamonds (NDs) are a novel type of material that has raised much attention, as they have the possibility of being produced on a large scale by relatively inexpensive synthetic methodologies. Moreover, NDs can present some other interesting features, such as fluorescence, due to surface functionalization and proved biocompatibility, which makes them suitable for biomedical applications. In addition, NDs can be customized with metallic nanoparticles (NPs), such as silver or gold, in order to combine the features of both. Raw NDs were used as modifiers of sensors due to the electrocatalytic effect of the sp2 and oxygenated species present on their surface. The aim of this research work is evaluating the applicability of NDs modified with silver (Ag@NDs) and gold (Au@NDs) nanoparticles for the development of a suitable (bio)sensing platform. A complete morphological and electrochemical characterization as a function of the prepared nanocomposite composition was performed in order to improve the electroanalytical properties of the developed (bio)sensors. In the present work, the optimal composition for Au@NDs present on the nanocomposite matrix is 3.5% and the one for Ag@NDs is 1%. Good results were obtained in the evaluation of the optimal composition towards hydrogen peroxide and glucose as a model analyte using a (bio)sensor based on graphite-epoxy-Ag@NDs (17:82:1)Peer ReviewedPostprint (published version

Carbon/polymer nanocomposite (Bio)sensors containing nanoparticles: functionalization and applications

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Recent trends in the improvement of the electrochemical response of screen-printed electrodes by their modification with shaped metal nanoparticles

Novel sensing technologies proposed must fulfill the demands of wastewater treatment plants, the food industry, and environmental control agencies: simple, fast, inexpensive, and reliable methodologies for onsite screening, monitoring, and analysis. These represent alternatives to conventional analytical methods (ICP-MS and LC-MS) that require expensive and non-portable instrumentation. This needs to be controlled by qualified technicians, resulting moreover in a long delay between sampling and high-cost analysis. Electrochemical analysis based on screen-printed electrodes (SPEs) represents an excellent miniaturized and portable alternative due to their disposable character, good reproducibility, and low-cost commercial availability. SPEs application is widely extended, which makes it important to design functionalization strategies to improve their analytical response. In this sense, different types of nanoparticles (NPs) have been used to enhance the electrochemical features of SPEs. NPs size (1–100 nm) provides them with unique optical, mechanical, electrical, and chemical properties that give the modified SPEs increased electrode surface area, increased mass-transport rate, and faster electron transfer. Recent progress in nanoscale material science has led to the creation of reproducible, customizable, and simple synthetic procedures to obtain a wide variety of shaped NPs. This mini-review attempts to present an overview of the enhancement of the electrochemical response of SPEs when NPs with different morphologies are used for their surface modificationPeer ReviewedPostprint (published version