The use of nanoparticles in electroanalysis: an updated review

Modified Working Electrodes for Organic Electrosynthesis

Organic electrosynthesis has gained much attention over the last few decades as a promising alternative to traditional synthesis methods. Electrochemical approaches offer numerous advantages over traditional organic synthesis procedures. One of the most interesting aspects of electroorganic synthesis is the ability to tune many parameters to affect the outcome of the reaction of interest. One such parameter is the composition of the working electrode. By changing the electrode material, one can influence the selectivity, product distribution, and rate of organic reactions. In this Review, we describe several electrode materials and modifications with applications in organic electrosynthetic transformations. Included in this discussion are modifications of electrodes with nanoparticles, composite materials, polymers, organic frameworks, and surface-bound mediators. We first discuss the important physicochemical and electrochemical properties of each material. Then, we briefly summarize several relevant examples of each class of electrodes, with the goal of providing readers with a catalog of electrode materials for a wide variety of organic syntheses.

Electrochemical Analysis of Methanol with Nafion-Coated Copper Oxide Nanoparticles

This work introduces a Nafion-coated copper(I) oxide nanoparticle electrode (Nafion/Cu2O/GC) designed for the electrochemical detection of methanol (CH3OH). The responses of the composite material toward CH3OH were enhanced by the selective permeation of CH3OH through the hydrophilic channels of the Nafion membrane in combination with the electroactivity of Cu2O nanoparticles. The sensor displayed a linear detection range of 0.33-100 mM CH3OH with a sensitivity of 0.17 μA·mM-1 and a detection limit (3 s/m) of 0.10 mM. It exhibited excellent reproducibility with a relative standard deviation of <5%. The sensor's practical applicability was demonstrated through recovery studies on hand sanitizer samples, achieving ca. 100% recovery. The sensor was further used to elucidate CH3OH adsorption on activated carbon, revealing that the process conforms to the Langmuir isotherm model.

Electrochemical deposition of gold nanoparticles on carbon ultramicroelectrode arrays

Electrode surfaces functionalized with gold nanoparticles (AuNP) are widely used in electroanalysis, electrocatalysis, and electrochemical biosensing due to their increased surface area and conductivity. Electrochemical deposition of AuNPs offers advantages over chemical synthesis, including better control over AuNP size, dispersion, and morphology. This study examines the electrodeposition of AuNPs on carbon ultramicroelectrode arrays (CUAs) focusing on electrodeposition parameters, such as deposition potential, deposition time, and gold ion concentration. Detailed analysis based on scanning electron microscopy revealed that higher reductive potentials and shorter deposition times result in smaller AuNP particle sizes and greater particle counts. Unlike previous studies using planar, macro-sized electrodes and millimolar concentrations of gold ion, as well as longer deposition times (e.g., 100-300 s), this research employed micromolar concentration ranges (25-50 μM) of gold ion solution and shorter deposition times (5-60 s) for successful electrodeposition of AuNPs on the array-based CUAs. This is attributed to the physical properties of the ultramicroelectrodes in the array geometry and the distinct material composition of the CUAs. The gold amounts deposited on the CUA electrodes were determined (88.73 ± 0.06 nmol cm-2), which were in correlation with the electrocatalytic responses for the hydrogen evolution reaction (HER) measured on AuNP-modified CUAs. Overall, the array-based geometry, nanometer-scale electrode sizes, and unique material composition of the CUAs significantly influence AuNP electrodeposition. This study underscores the importance of systematically characterizing the electrodeposition parameters on novel electrode surfaces.

Creation of a 3D Goethite-Spongin Composite Using an Extreme Biomimetics Approach

The structural biopolymer spongin in the form of a 3D scaffold resembles in shape and size numerous species of industrially useful marine keratosan demosponges. Due to the large-scale aquaculture of these sponges worldwide, it represents a unique renewable source of biological material, which has already been successfully applied in biomedicine and bioinspired materials science. In the present study, spongin from the demosponge Hippospongia communis was used as a microporous template for the development of a new 3D composite containing goethite [α-FeO(OH)]. For this purpose, an extreme biomimetic technique using iron powder, crystalline iodine, and fibrous spongin was applied under laboratory conditions for the first time. The product was characterized using SEM and digital light microscopy, infrared and Raman spectroscopy, XRD, thermogravimetry (TG/DTG), and confocal micro X-ray fluorescence spectroscopy (CMXRF). A potential application of the obtained goethite-spongin composite in the electrochemical sensing of dopamine (DA) in human urine samples was investigated, with satisfactory recoveries (96% to 116%) being obtained.

Impact of nanotechnology on progress of flow methods in chemical analysis: A review

In evolution of instrumentation for analytical chemistry as crucial technological breakthroughs should be considered a common introduction of electronics with all its progress in integration, and then microprocessors which was followed by a widespread computerization. It is seems that a similar role can be attributed to the introduction of various elements of modern nanotechnology, observed with a fast progress since beginning of this century. It concerns all areas of the applications of analytical chemistry, including also progress in flow analysis, which are being developed since the middle of 20th century. Obviously, it should not be omitted the developed earlier and analytically applied planar structures like lipid membranes or self-assembled monolayers They had essential impact prior to discoveries of numerous extraordinary nanoparticles such as fullerenes, carbon nanotubes and graphene, or nanocrystalline semiconductors (quantum dots). Mostly, due to catalytic effects, significantly developed surface and the possibility of easy functionalization, their application in various stages of flow analytical procedures can significantly improve them. The application of new nanomaterials may be used for the development of new detection methods for flow analytical systems in macro-flow setups as well as in microfluidics and lateral flow immunoassay tests. It is also advantageous that quick flow conditions of measurements may be helpful in preventing unfavorable agglomeration of nanoparticles. A vast literature published already on this subject (e.g. almost 1000 papers about carbon nanotubes and flow-injection analytical systems) implies that for this reviews it was necessary to make an arbitrary selection of reported examples of this trend, focused mainly on achievements reported in the recent decade.

Spongin as a Unique 3D Template for the Development of Functional Iron-Based Composites Using Biomimetic Approach In Vitro

Marine sponges of the subclass Keratosa originated on our planet about 900 million years ago and represent evolutionarily ancient and hierarchically structured biological materials. One of them, proteinaceous spongin, is responsible for the formation of 3D structured fibrous skeletons and remains enigmatic with complex chemistry. The objective of this study was to investigate the interaction of spongin with iron ions in a marine environment due to biocorrosion, leading to the occurrence of lepidocrocite. For this purpose, a biomimetic approach for the development of a new lepidocrocite-containing 3D spongin scaffold under laboratory conditions at 24 °C using artificial seawater and iron is described for the first time. This method helps to obtain a new composite as "Iron-Spongin", which was characterized by infrared spectroscopy and thermogravimetry. Furthermore, sophisticated techniques such as X-ray fluorescence, microscope technique, and X-Ray diffraction were used to determine the structure. This research proposed a corresponding mechanism of lepidocrocite formation, which may be connected with the spongin amino acids functional groups. Moreover, the potential application of the biocomposite as an electrochemical dopamine sensor is proposed. The conducted research not only shows the mechanism or sensor properties of "Iron-spongin" but also opens the door to other applications of these multifunctional materials.

Signaling strategies of silver nanoparticles in optical and electrochemical biosensors: considering their potential for the point-of-care

Silver nanoparticles (AgNPs) have long been overshadowed by gold NPs' success in sensor and point-of-care (POC) applications. However, their unique physical, (electro)chemical, and optical properties make them excellently suited for such use, as long as their inherent higher instability toward oxidation is controlled. Recent advances in this field provide novel strategies that demonstrate that the AgNPs' inherent capabilities improve sensor performance and enable the specific detection of analytes at low concentrations. We provide an overview of these advances by focusing on the nanosized Ag (in the range of 1-100 nm) properties with emphasis on optical and electrochemical biosensors. Furthermore, we critically assess their potential for point-of-care sensors discussing advantages as well as limitations for each detection technique. We can conclude that, indeed, strategies using AgNP are ready for sensitive POC applications; however, research focusing on the simplification of assay procedures is direly needed for AgNPs to make the successful jump into actual applications.

Recent advances in electrochemical sensor developments for detecting emerging pollutant in water environment

In the latest times, considerable studies have been performed closer to detecting emerging pollutant such as paracetamol in wastewater. Electrochemical sensor developments have recently started to determine in fewer concentrations effectively. The detection of paracetamol using standard protocols corresponding to electroanalytical techniques has a greater impact noticed in directing the detecting process toward biosensors. Non-enzymatic sensors are the peak of all electro analysis approaches. Functionalized materials, such as metal oxide nanoparticles, conducting polymers, and carbon-based materials for electrode surface functionalization have been used to create a fortification for distributing passive enzyme-free biosensors. Synergic effects are possible by enhancing loading capacity and mass transfer of reactants for attaining high analytical sensitivity using a variety of nanomaterials with large surface areas. The main focus of this study is to address the prevailing issues in the identification of paracetamol with the tasks in the non-enzymatic sensors field, followed by the useful methods of electro analysis studies.

Safety of Lavender Oil-Loaded Niosomes for In Vitro Culture and Biomedical Applications

(1) Background: Essential oils have long been used as therapeutic agents. Lavender (Lavandula angustifolia) oil (LO) is an antispasmodic, anticonvulsant, relaxant, painkilling, and antimicrobial essential oil investigated as a natural substance for biomedical therapies. Nanoparticles have shown significant promise in improving drug delivery and efficacy. Considering these benefits, the aim of this study was to evaluate the toxicity of LO and lavender oil niosomes (LONs) in stem cells and myofibroblast models cultured in vitro. (2) Methods: Adipose tissue-derived stem cells and myometrial cells were cultured with LO or LONs at different concentrations (0, 0.016%, 0.031%, and 0.063%) and toxicity was evaluated with PrestoBlue™ and live/dead assay using calcein and ethidium homodimer. (3) Results: Cell viability was similar to controls in all groups, except in 0.063% LO for myometrial cells, which showed lower viability than the control medium. (4) Conclusion: These results suggest that both LO and LONs are safe for cell culture and may be used for pharmaceutical and biomedical therapies in future applications in regenerative medicine.

Electrochemical sensors based on metal nanoparticles with biocatalytic activity

Biosensors have attracted a great deal of attention, as they allow for the translation of the standard laboratory-based methods into small, portable devices. The field of biosensors has been growing, introducing innovations into their design to improve their sensing characteristics and reduce sample volume and user intervention. Enzymes are commonly used for determination purposes providing a high selectivity and sensitivity; however, their poor shelf-life is a limiting factor. Researchers have been studying the possibility of substituting enzymes with other materials with an enzyme-like activity and improved long-term stability and suitability for point-of-care biosensors. Extra attention is paid to metal and metal oxide nanoparticles, which are essential components of numerous enzyme-less catalytic sensors. The bottleneck of utilising metal-containing nanoparticles in sensing devices is achieving high selectivity and sensitivity. This review demonstrates similarities and differences between numerous metal nanoparticle-based sensors described in the literature to pinpoint the crucial factors determining their catalytic performance. Unlike other reviews, sensors are categorised by the type of metal to study their catalytic activity dependency on the environmental conditions. The results are based on studies on nanoparticle properties to narrow the gap between fundamental and applied research. The analysis shows that the catalytic activity of nanozymes is strongly dependent on their intrinsic properties (e.g. composition, size, shape) and external conditions (e.g. pH, type of electrolyte, and its chemical composition). Understanding the mechanisms behind the metal catalytic activity and how it can be improved helps designing a nanozyme-based sensor with the performance matching those of an enzyme-based device.

A state of the art overview of carbon-based composites applications for detecting and eliminating pharmaceuticals containing wastewater

The growing prevalence of new toxins in the environment continues to cause widespread concerns. Pharmaceuticals, organic pollutants, heavy metal ions, endocrine-disrupting substances, microorganisms, and others are examples of persistent organic chemicals whose effects are unknown because they have recently entered the environment and are displaying up in wastewater treatment facilities. Pharmaceutical pollutants in discharged wastewater have become a danger to animals, marine species, humans, and the environment. Although their presence in drinking water has generated significant concerns, little is known about their destiny and environmental effects. As a result, there is a rising need for selective, sensitive, quick, easy-to-handle, and low-cost early monitoring detection systems. This study aims to deliver an overview of a low-cost carbon-based composite to detect and remove pharmaceutical components from wastewater using the literature reviews and bibliometric analysis technique from 1970 to 2021 based on the web of science (WoS) database. Various pollutants in water and soil were reviewed, and different methods were introduced to detect pharmaceutical pollutants. The advantages and drawbacks of varying carbon-based materials for sensing and removing pharmaceutical wastes were also introduced. Finally, the available techniques for wastewater treatment, challenges and future perspectives on the recent progress were highlighted. The suggestions in this article will facilitate the development of novel on-site methods for removing emerging pollutants from pharmaceutical effluents and commercial enterprises.

Electrochemical Synthesis of Unique Nanomaterials in Ionic Liquids

The review considers the features of the processes of the electrochemical synthesis of nanostructures in ionic liquids (ILs), including the production of carbon nanomaterials, silicon and germanium nanoparticles, metallic nanoparticles, nanomaterials and surface nanostructures based on oxides. In addition, the analysis of works on the synthesis of nanoscale polymer films of conductive polymers prepared using ionic liquids by electrochemical methods is given. The purpose of the review is to dwell upon an aspect of the applicability of ILs that is usually not fully reflected in modern literature, the synthesis of nanostructures (including unique ones that cannot be obtained in other electrolytes). The current underestimation of ILs as an electrochemical medium for the synthesis of nanomaterials may limit our understanding and the scope of their potential application. Another purpose of our review is to expand their possible application and to show the relative simplicity of the experimental part of the work.

A voltammetric sensor based on a carbon black and chitosan-stabilized gold nanoparticle nanocomposite for ketoconazole determination

A modified glassy carbon electrode with carbon black (CB) and gold nanoparticles (AuNPs) within a crosslinked chitosan (CTS) film is proposed in this work. The electroanalytical performance of the modified CB-CTS-AuNPs/GCE has been evaluated towards the voltammetric sensing of ketoconazole (KTO), a widespread antifungal drug. The nanocomposite was characterized by scanning electron microscopy, X-ray diffraction spectroscopy, and electrochemistry experiments. The evaluation of the electrochemical behaviour of KTO on the proposed modified electrode shows an irreversible oxidation process at a potential of +0.65 V (vs. Ag/AgCl (3.0 mol L^-1 KCl)). This redox process was explored to carry out KTO sensing using square-wave voltammetry. The analytical curve was linear in the KTO concentration range from 0.10 to 2.9 μmol L^-1, with a limit of detection (LOD) of 4.4 nmol L^-1 and a sensitivity of 3.6 μA L μmol^-1. This modified electrode was successfully applied to the determination of KTO in pharmaceutical formulations and biological fluid samples.

Local Field Induced Mass Transfer: New Insight into Nano-electrocatalysis

Unravelling the complex kinetics of electrocatalysis is essential for the design of electrocatalysts with high performance. Mass transfer and electron transfer are two primary factors that need to be optimized in order to enhance electrocatalytic reactions. The use of nanocatalysts proves to be a promising way of promoting the performance of electrocatalytic reactions, this improvement is usually attributed to their ability to enhance electron transfer. However, when catalysts are taken down to the nanoscale, their size is comparable to the thickness of an electrical double layer, so any curvature can lead to an inhomogeneous local electric field on the electrode, which then changes the mass transfer essentially. In this article, we introduce the new concept of local-field-induced mass transfer in nano-electrocatalytic systems, and provide a brief review of recent progress, revealing its effect on nano-electrocatalysis, which may bring new insight into the future design of nano-electrocatalysts.

Photo-induced green synthesis of bimetallic Ag/Pd nanoparticles decorated reduced graphene oxide/nitrogen-doped graphene quantum dots nanocomposite as an amperometric sensor for nitrite detection

The present study introduces a novel nanocomposite based on reduced graphene oxide, nitrogen-doped graphene quantum dots, and palladium and silver nanoparticles (rGO/NGQD/AgPd) as an electrocatalyst toward nitrite oxidation reaction. Metal nanoparticles were prepared via a green one-pot photochemical reduction procedure utilizing UV light and NGQD simultaneously as a reducing and directing agent. Formation of the nanocomposite was thoroughly demonstrated by the FT-IR, XRD, Raman, XPS, FE-SEM, and TEM characterization tests. Various electrochemical tests evaluated the efficiency of the prepared sensing platform on the surface of a gold working electrode. Sensitivity and limit of detection (LOD) were calculated to be 0.854 μA.μM^-1.cm^-2 and 0.052 μM, respectively, from the chronoamperometry data. Finally, the proposed sensor was successfully applied for the determination of nitrite ions in river and mineral water samples as natural water sources.

Glassy Carbon Electrode Modified with C/Au Nanostructured Materials for Simultaneous Determination of Hydroquinone and Catechol in Water Matrices

The simultaneous determination of hydroquinone and catechol was conducted in aqueous and real samples by means of differential pulse voltammetry (DPV) using a glassy carbon electrode modified with Gold Nanoparticles (AuNP) and functionalized multiwalled carbon nanotubes by drop coating. A good response was obtained in the simultaneous determination of both isomers through standard addition to samples prepared with analytical grade water and multivariate calibration by partial least squares (PLS) in winery wastewater fortified with HQ and CT from 4.0 to 150.00 µM. A sensitivity of 0.154 µA µM−1 and 0.107 µA µM−1, and detection limits of 4.3 and 3.9 µM were found for hydroquinone and catechol, respectively. We verified the reliability of the developed method by simultaneously screening analytes in spiked tap water and industrial wastewater, achieving recoveries over 80%. In addition, this paper demonstrates the applicability of chemometric tools for the simultaneous quantification of both isomers in real matrices, obtaining prediction errors of lower than 10% in fortified wastewater.

Fully integrated 3D-printed electrochemical cell with a modified inkjet-printed Ag electrode for voltammetric nitrate analysis

To address the need for low-cost analytical tools for on-site aquaculture water quality monitoring, miniaturized electrochemical sensor systems can be readily fabricated using additive manufacturing technologies such as 3D printing and inkjet printing. In this work, we report the design and fabrication of an additively manufactured electrochemical platform featuring a reusable 3D-printed electrochemical cell with integrated reference and counter electrodes, and a replaceable inkjet-printed Ag (IJP-Ag) working electrode. The electrochemical cell was 3D-printed with acrylonitrile butadiene styrene (ABS) filament and features a 3D-printed ABS-carbon counter electrode and a Ag|AgCl|gel-KCl reference electrode with a 3D-printed porous junction directly integrated along the sides of the sample compartment. The application of the integrated cell is demonstrated with the analysis of nitrate ions on the IJP-Ag electrode, which was modified with electrodeposited nanostructured Ag to enhance sensitivity to nitrate reduction. Linear sweep voltammetry (LSV) was successfully applied to detect nitrate with a LOD of 1.40 ppm and a sensitivity of 0.2086 μA ppm^-1 in a background of artificial brackish aquaculture water (pH 8.0). The sensor response showed intra- and inter-electrode reproducibility and no significant interferences to most of the commonly encountered cations and anions in brackish water. The electrochemical sensor system was also applied to nitrate determination in real aquaculture water samples and demonstrated no significant differences with the results obtained using the standard spectrophotometric method at a 95% confidence level. Our results show how additive manufacturing is a promising approach to readily fabricate fit-for-purpose, low-cost miniaturized electrochemical sensor systems for point-of-use applications.

Revealing Dynamic Rotation of Single Graphene Nanoplatelets on Electrified Microinterfaces

Nanoparticles interact with a variety of interfaces, from cell walls for medicinal applications to conductive interfaces for energy storage and conversion applications. Unfortunately, quantifying dynamic changes of nanoparticles near interfaces is difficult. While optical techniques exist to study nanoparticle dynamics, motions smaller than the diffraction limit are difficult to quantify. Single-entity electrochemistry has high sensitivity, but the technique suffers from ambiguity in the entity's size, morphology, and collision location. Here, we combine optical microscopy, single-entity electrochemistry, and numerical simulations to elucidate the dynamic motion of graphene nanoplatelets at a gold ultramicroelectrode (radius ∼5 μm). The approach of conductive graphene nanoplatelets, suspended in 10 μM NaOH, to an ultramicroelectrode surface was tracked optically during the continuous oxidation of ferrocenemethanol. Optical microscopy confirmed the nanoplatelet size, morphology, and collision location on the ultramicroelectrode. Nanoplatelets collided on the ultramicroelectrode at an angle, θ, enhancing the electroactive area, resulting in a sharp increase in current. After the collision, the nanoplatelets reoriented to lay flat on the electrode surface, which manifested as a return to the baseline current in the amperometric current-time response. Through correlated finite element simulations, we extracted single nanoplatelet angular velocities on the order of 0.5-2°/ms. These results are a necessary step forward in understanding nanoparticle dynamics at the nanoscale.

Determination of paracetamol using a sensor based on green synthesis of silver nanoparticles in plant extract

The biosynthesis of nanometals using a plant extract is simple, efficient, fast, cost-effective and eco-friendly. In this study, a pine nut extract (Araucaria angustifolia) was obtained and used as a reducing and stabilizing agent in the synthesis of silver nanoparticles. An electrochemical sensor based on the silver nanoparticles obtained and exfoliated graphite nanoplatelets applied to a glassy carbon electrode was developed for the determination of paracetamol. To optimize the synthesis of the silver nanoparticles, important factors such as temperature, extract:water ratio, silver nitrate concentration and extract stability time were studied. The factors influencing the performance of the sensor were studied in detail and the results demonstrated good repeatability and electrode-to-electrode repeatability (relative standard deviations of 1.8 and 4.0 %, respectively). Under optimized conditions, there was a linear response to paracetamol concentrations of 4.98 × 10^-6 to 3.38 × 10^-5 mol L^-1, with a detection limit of 8.50 × 10^-8 mol L^-1. No reports on the biosynthesis of AgNPs using Araucaria angustifolia could be found in the literature. The sensor developed showed good stability and was used successfully for the quantification of paracetamol in pharmaceutical products.

Hybrid Carbon Film Electrodes for Electroanalysis

Carbon materials have been widely used for electrochemical analysis and include carbon nanotubes, graphene, and boron-doped diamond electrodes in addition to conventional carbon electrodes, such as those made of glassy carbon and graphite. Of the carbon-based electrodes, carbon film has advantages because it can be fabricated reproducibly and micro- or nanofabricated into electrodes with a wide range of shapes and sizes. Here, we report two categories of hybrid-type carbon film electrodes for mainly electroanalytical applications. The first category consists of carbon films doped or surface terminated with other atoms such as nitrogen, oxygen and fluorine, which can control surface hydrophilicity and lipophilicity or electrocatalytic performance, and are used to detect various electroactive biochemicals. The second category comprises metal nanoparticles embedded in carbon film electrodes fabricated by co-sputtering, which exhibits high electrocatalytic activity for environmental and biological samples including toxic heavy metal ions and clinical sugar markers, which are difficult to detect at pure carbon-based electrodes.

A novel nanostructured poly(thionine)-deep eutectic solvent/CuO nanoparticle film-modified disposable pencil graphite electrode for determination of acetaminophen in the presence of ascorbic acid

A new electrochemical sensor based on thionine (TH), an electroactive polymer, and CuO nanoparticle (CuONP)-modified pencil graphite electrode (PGE) has been developed. Poly(thionine) (PTH) was formed on the CuO/PGE surface by electropolymerisation in ethaline deep eutectic solvent (DES) containing acetic acid dopant to form PTH_Ethaline/CuO/PGE. Cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry were utilized to evaluate the fabrication process, electrochemical properties, and performance parameters of the modified electrodes. The analytical performance of the PTH_Ethaline/CuO/PGE was evaluated with respect to linear range, limit of detection, repeatability, and reproducibility for the detection of acetaminophen (APAP) by electrooxidation in the presence of ascorbic acid (AA). Analytical parameters such as pH were optimized. The combined use of PTH and CuONP led to enhanced performance towards APAP due to the large electroactive surface area and synergistic catalytic effect, with a wide linear working range and low detection limit. The reliability of the proposed sensor for the detection of APAP was successfully tested in pharmaceutical samples containing APAP and AA, with very good recoveries. Graphical abstract.

Palladium nanoparticles in situ synthesized on Cyclea barbata pectin as a heterogeneous catalyst for Heck coupling in water, the reduction of nitrophenols and alkynes

This study develops an effective method for in situ synthesis of PdNPs using Cyclea barbata pectin as green reducing and stabilizing reagent. The catalytic activity of nanocomposite was evaluated for Heck coupling reaction, reduction of nitrophenols and reduction of alkynes.

Nanoporous silver using pulsed laser deposition for high-performance oxygen reduction reaction and hydrogen peroxide sensing

Silver (Ag)-based materials have shown great application potential in the oxygen reduction reaction (ORR) and hydrogen peroxide (H2O2) detection. The porous structures of Ag have attracted a lot of research interest due to their large specific surface area and high electrochemical activity. In this work, nanoporous Ag structures composed of nano-sized particles were prepared by a one-step pulsed laser deposition (PLD) under controlled background gas pressure. The porous PLD-Ag showed a high ORR performance (Eonset: 1.007 V vs. RHE, E1/2: 0.863 V vs. RHE), high sensitivity (613.1 μA cm-2 mM-1 at -0.2 V vs. SCE) and selectivity for H2O2 detection. The PLD technique provided a new, yet universal approach to producing high-performance, metal-based electrochemical electrodes.

Green Wastes Mediated Zinc Oxide Nanoparticles: Synthesis, Characterization and Electrochemical Studies

Zinc Oxide (ZnO) nanoparticles were prepared using a simple green synthesis approach in an alkaline medium, from three different extracts of citrus peels waste. The synthesized nano-crystalline materials were characterized by using ultraviolet-visible spectroscopy (UV-vis), x-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive x-ray spectroscopy (EDS), environmental scanning electron microscopy (ESEM), and transmission electron microscopy (TEM). UV-vis analysis of the nanoparticles showed broad peaks around 360 nm for the ZnO NPs (Zinc oxide nanoparticles) from three citrus peels’ extracts. ZnO NPs exhibited Zn–O band close to 553 cm⁻¹, which further verified the formation of the ZnO NPs. A bandgap of 3.26 eV, 3.20 eV and 3.30 eV was calculated for the ZnO NPs from grape (ZnO NPs/GPE), lemon (ZnO NPs/LPE), and orange (ZnO NPs/OPE) peels extract, respectively. The average grain sizes of the ZnO nanoparticles were evaluated to be 30.28 nm, 21.98 nm, and 18.49 nm for grape (ZnO NPs/GPE), lemon (ZnO NPs/LPE), and orange (ZnO NPs/OPE) peel extract, respectively. The surface morphology and sizes of the nanoparticle were confirmed by ESEM and TEM analysis, respectively. Furthermore, the zeta potential of the as-prepared ZnO NPs from OPE, LPE, and GPE was −34.2 mV, −38.8 mV, and −42.9 mV, respectively, indicating the high stability of the nanoparticles. Cyclic voltammetric properties of the synthesized nanoparticles were investigated across extracts, and the results showed that the citrus peels extracts (CPE) mediated ZnO NPs modified screen plate carbon (SPC/ ZnO NPs/CPE) electrodes exhibited enhanced catalytic properties when compared with the bare SPCE. The electroactive areas computed from the enhancement of the bare SPCE was approximately three times for SPCE/ ZnO NPs/LPE, and SPCE/ZnO NPs/GPE, and two times for SPCE/ZnO NPs/OPE, higher than that of the bare SPCE. Comparison across the extracts suggested that the catalytic properties of the nanoparticles were unique in ZnO NPs from GPE.

Synthesizing of a nanocomposite based on the formation of silver nanoparticles on fumed silica to develop an electrochemical sensor for carbendazim detection

In this study, a nanocomposite was synthesized via the formation of silver nanoparticles on fumed silica (FS@Ag) to prepare an electrochemical sensor for the determination of carbendazim (CBZ), a common pesticide. The electrochemical sensor was designed by the combination of the carbon paste electrode (CPE) with the FS@Ag nanocomposite. Based on the electrochemical sensor prepared here, a voltammetric method was developed for the determination of CBZ in water and food samples. Characterization of the nanocomposite was conducted by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analyses. Modified electrodes were also electrochemically characterized via cyclic voltammetry and electrochemical impedance spectroscopy analyses. The FS@Ag showed electrocatalytic activity on the electrochemical oxidation of CBZ via increasing the peak currents tremendously. With the proposed method, a very low limit of detection (9.4 × 10^-10 M) and a wide linear range (5.0 × 10^-8 M - 3.0 × 10^-6 M) were obtained for CBZ. The slope of the calibration line obtained with CPE/15FS@Ag was 194-times higher than that of bare CPE, indicating the high sensitivity of the electrochemical sensor. The performance of the electrochemical sensor has been investigated in real samples such as river water, tomato juice, orange juice, and apple juice samples. The results reveal that the electrochemical sensor prepared here can be used as an alternative to current analytical methods used for the quantification of CBZ.

Interaction between Amorphous Zirconia Nanoparticles and Graphite: Electrochemical Applications for Gallic Acid Sensing Using Carbon Paste Electrodes in Wine

Amorphous zirconium oxide nanoparticles (ZrO₂) have been used for the first time, to modify carbon paste electrode (CPE) and used as a sensor for the electrochemical determination of gallic acid (GA). The voltammetric results of the ZrO₂ nanoparticles-modified CPE showed efficient electrochemical oxidation of gallic acid, with a significantly enhanced peak current from 261 µA ± 3 to about 451 µA ± 1. The modified surface of the electrode and the synthesised zirconia nanoparticles were characterised by scanning electrode microscopy (SEM), Energy-dispersive x-ray spectroscopy (EDXA), X-ray powdered diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Meanwhile, the electrochemical behaviour of GA on the surface of the modified electrode was studied using differential pulse voltammetry (DPV), showing a sensitivity of the electrode for GA determination, within a concentration range of 1 × 10⁻⁶ mol L⁻¹ to 1 × 10⁻³ mol L⁻¹ with a correlation coefficient of R² of 0.9945 and a limit of detection of 1.24 × 10⁻⁷ mol L⁻¹ (S/N = 3). The proposed ZrO₂ nanoparticles modified CPE was successfully used for the determination of GA in red and white wine, with concentrations of 0.103 mmol L⁻¹ and 0.049 mmol L⁻¹ respectively.