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 modificatio

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 micromotors

Potential Use of Precipitates from Acid Mine Drainage (AMD) as Arsenic Adsorbents

The role of precipitates from acid mine drainage (AMD) in arsenic removal in water is a process to be investigated in more detail. The present study is focused on the potential use of two AMD precipitates using oxidation and Ca(OH)2 (OxPFe1) or CaCO3 (OxPFe2) as As(V) adsorbents and the comparison of their performance with two commercial adsorbents (nanohematite and Bayoxide®). The AMD's supernatants and precipitates were characterized using several techniques and assessed with theoretical speciation and mass balance methods. Gypsum was identified by XRD and assessed as the main component of the precipitates. Amorphous iron hydroxide was assessed as the second component (22% in mass), and jurbanite or aluminum hydroxide were present in the third likely phase. The equilibrium adsorption of As(V) in water at a pH between 4 and 6 was tested with the four adsorbents, and the Langmuir model correlated well. The maximum adsorption capacity (qmax) had the highest value for OxPFe1 and the lowest value for nanohematite (that could be explained in terms of the adsorbent surface speciation). The two precipitates have limited application to the adsorption of very low concentrations of arsenic because they have a binding constant (b) lower than the commercial adsorbents and could release a small amount of the arsenic contained in the precipitate

Composite Electrodes Based on Carbon Materials Decorated with Hg Nanoparticles for the Simultaneous Detection of Cd(II), Pb(II) and Cu(II)

Monitoring water quality has become a goal to prevent issues related to human health and environmental conditions. In this sense, the concentration of metal ions in water sources is screened, as these are considered persistent contaminants. In this work, we describe the implementation of customized graphite electrodes decorated with two types of Hg nanoparticles (Hg-NPs), optimized toward the electrochemical detection of Cd, Pb and Cu. Here, we combine Hg, a well-known property to form alloys with other metals, with the nanoscale features of Hg-NPs, resulting in improved electrochemical sensors towards these analytes with a substantial reduction in the used Hg amount. Hg-NPs were synthesized using poly(diallyldimethylammonium) chloride (PDDA) in a combined role as a reducing and stabilizing agent, and then appropriately characterized by means of Transmission Electron Microscopy (TEM) and Zeta Potential. The surface of composite electrodes with optimized graphite content was modified by the drop-casting of the prepared Hg-NPs. The obtained nanocomposite electrodes were morphologically characterized by Scanning Electron Microscopy (SEM), and electrochemically by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The results show that the Hg-NP-modified electrodes present better responses towards Cd(II), Pb(II) and Cu(II) detection in comparison with the bare graphite electrode. Analytical performance of sensors was evaluated by square-wave anodic stripping voltammetry (SWASV), obtaining a linear range of 0.005-0.5 mg·L−1 for Cd2+, of 0.028-0.37 mg·L−1 for Pb2+ and of 0.057-1.1 mg·L−1 for Cu2+. Real samples were analyzed using SWASV, showing good agreement with the recovery values of inductively coupled plasma-mass spectrometry (ICP-MS) measurement

Morphological changes of gel-type functional polymers after intermatrix synthesis of polymer stabilized silver nanoparticles

This paper reports the results of intermatrix synthesis (IMS) of silver metal nanoparticles (Ag-MNPs) in Purolite C100E sulfonic ion exchange polymer of the gel-type structure. It has been shown that the surface morphology of the initial MNP-free polymer is absolutely smooth, but it dramatically changes after the kinetic loading of Ag on the polymer and then IMS of Ag-MNPs. These morphological changes can be explained by the interaction of Ag-NPs with the polymer chains, leading to a sort of additional cross-linking of the polymer. As a result, the modification of the gel-type matrix with Ag-MNPs leads to the increase of the matrix cross-linking, which results in the increase of its surface area and the appearance of nanoporosity in the polymer gel. Ag-MNPs are located near the polymer surface and do not form any visible agglomerations. All these features of the nanocomposites obtained are important for their practical applications in catalysis, sensor applications, and bactericide water treatme

Functionalization of Screen-Printed Electrodes with Grape Stalk Waste Extract-Assisted Synthesized Silver and Gold Nanoparticles: Perspectives of electrocatalytically Enhanced Determination of Uranyl Ion and Other Heavy Metals Ions

Recently, nanotechnology and nanoparticles (NPs) such as AgNPs and AuNPs have become important in analytical chemistry due to their great potential to improve the performance of electrochemical sensors. In this work, Ag and Au nanoparticles have been synthesized using a green route in which a grape stalk waste extract is used as a reducing agent to obtain metallic nanoparticles. These NPs were used to customize the surface of commercial screen-printed electrodes (SPCNFEs). The spin-coating method was used to modify commercial SPCNFEs under a nitrogen atmosphere. The resulting electrodes were used in a determination study of Cd(II), Pb(II), and U(VI) with differential pulse anodic stripping voltammetry (DPASV). The customized green AgNPs and AuNPs electrodes presented higher sensitivity and electroanalytical performance than the nonmodified SPCNFE. The results showed that the best analytical parameters were obtained with the green, silver nanoparticle SPCNFEs, with a LOD of 0.12 µg L−1 for Pb(II), which is a lower value compared to the most restrictive regulation guidelines. Additionally, the U(VI) ion was successfully determined using the developed G-AgNPs-SPCNFE in spiked tap water, showing comparable results with the ICP-MS techniqu

Bacterial Biohybrid Microswimmers

Over millions of years, Nature has optimized the motion of biological systems at the micro and nanoscales. Motor proteins to motile single cells have managed to overcome Brownian motion and solve several challenges that arise at low Reynolds numbers. In this review, we will briefly describe naturally motile systems and their strategies to move, starting with a general introduction that surveys a broad range of developments, followed by an overview about the physical laws and parameters that govern and limit motion at the microscale. We characterize some of the classes of biological microswimmers that have arisen in the course of evolution, as well as the hybrid structures that have been constructed based on these, ranging from Montemagno's ATPase motor to the SpermBot. Thereafter, we maintain our focus on bacteria and their biohybrids. We introduce the inherent properties of bacteria as a natural microswimmer and explain the different principles bacteria use for their motion. We then elucidate different strategies that have been employed for the coupling of a variety of artificial microobjects to the bacterial surface, and evaluate the different effects the coupled objects have on the motion of the 'biohybrid.' Concluding, we give a short overview and a realistic evaluation of proposed applications in the field

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)

Bifunctional Polymer-Metal Nanocomposite Ion Exchange Materials

Peer ReviewedPostprint (published version

Morphological changes of gel-type functional polymers after intermatrix synthesis of polymer stabilized silver nanoparticles

This paper reports the results of intermatrix synthesis (IMS) of silver metal nanoparticles (Ag-MNPs) in Purolite C100E sulfonic ion exchange polymer of the gel-type structure. It has been shown that the surface morphology of the initial MNP-free polymer is absolutely smooth, but it dramatically changes after the kinetic loading of Ag on the polymer and then IMS of Ag-MNPs. These morphological changes can be explained by the interaction of Ag-NPs with the polymer chains, leading to a sort of additional cross-linking of the polymer. As a result, the modification of the gel-type matrix with Ag-MNPs leads to the increase of the matrix cross-linking, which results in the increase of its surface area and the appearance of nanoporosity in the polymer gel. Ag-MNPs are located near the polymer surface and do not form any visible agglomerations. All these features of the nanocomposites obtained are important for their practical applications in catalysis, sensor applications, and bactericide water treatment