Highly ordered platinum-nanotube arrays for oxidative determination of trace arsenic(III)

Anodic Stripping Voltammetric Analysis of Trace Arsenic(III) on a Au-Stained Au Nanoparticles/Pyridine/Carboxylated Multiwalled Carbon Nanotubes/Glassy Carbon Electrode

A Au-stained Au nanoparticle (Aus)/pyridine (Py)/carboxylated multiwalled carbon nanotubes (C-MWCNTs)/glassy carbon electrode (GCE) was prepared for the sensitive analysis of As(III) by cast-coating of C-MWCNTs on a GCE, electroreduction of 4-cyanopyridine (cPy) to Py, adsorption of gold nanoparticles (AuNPs), and gold staining. The Py/C-MWCNTs/GCE can provide abundant active surface sites for the stable loading of AuNPs and then the AuNPs-initiated Au staining in HAuCl4 + NH2OH solution, giving a large surface area of Au on the Aus/Py/C-MWCNTs/GCE for the linear sweep anodic stripping voltammetry (LSASV) analysis of As(III). At a high potential-sweep rate of 5 V s-1, sharp two-step oxidation peaks of As(0) to As(III) and As(III) to As(V) were obtained to realize the sensitive dual-signal detection of As(III). Under optimal conditions, the ASLSV peak currents for oxidation of As(0) to As(III) and of As(III) to As(V) are linear with a concentration of As(III) from 0.01 to 8 μM with a sensitivity of 0.741 mA μM-1 and a limit of detection (LOD) of 3.3 nM (0.25 ppb) (S/N = 3), and from 0.01 to 8.0 μM with a sensitivity of 0.175 mA μM-1 and an LOD of 16.7 nM (1.20 ppb) (S/N = 3), respectively. Determination of As(III) in real water samples yielded satisfactory results.

Advances in Electrochemical Detection Electrodes for As(III)

Arsenic is extremely abundant in the Earth's crust and is one of the most common environmental pollutants in nature. In the natural water environment and surface soil, arsenic exists mainly in the form of trivalent arsenite (As(III)) and pentavalent arsenate (As(V)) ions, and its toxicity can be a serious threat to human health. In order to manage the increasingly serious arsenic pollution in the living environment and maintain a healthy and beautiful ecosystem for human beings, it is urgent to conduct research on an efficient sensing method suitable for the detection of As(III) ions. Electrochemical sensing has the advantages of simple instrumentation, high sensitivity, good selectivity, portability, and the ability to be analyzed on site. This paper reviews various electrode systems developed in recent years based on nanomaterials such as noble metals, bimetals, other metals and their compounds, carbon nano, and biomolecules, with a focus on electrodes modified with noble metal and metal compound nanomaterials, and evaluates their performance for the detection of arsenic. They have great potential for achieving the rapid detection of arsenic due to their excellent sensitivity and strong interference immunity. In addition, this paper discusses the relatively rare application of silicon and its compounds as well as novel polymers in achieving arsenic detection, which provides new ideas for investigating novel nanomaterial sensing. We hope that this review will further advance the research progress of high-performance arsenic sensors based on novel nanomaterials.

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

A new direction for developing electrocatalysts for hydrogen fuel cell systems has emerged, based on the fabrication of 3D architectures. These new architectures include extended Pt surface building blocks, the strategic use of void spaces, and deliberate network connectivity along with tortuosity, as design components. Various strategies for synthesis now enable the functional and structural engineering of these electrocatalysts with appropriate electronic, ionic, and electrochemical features. The new architectures provide efficient mass transport and large electrochemically active areas. To date, although there are few examples of fully functioning hydrogen fuel cell devices, these 3D electrocatalysts have the potential to achieve optimal cell performance and durability, exceeding conventional Pt powder (i.e., Pt/C) electrocatalysts. This progress report highlights the various 3D architectures proposed for Pt electrocatalysts, advances made in the fabrication of these structures, and the remaining technical challenges. Attempts to develop design rules for 3D architectures and modeling, provide insights into their achievable and potential performance. Perspectives on future developments of new multiscale designs are also discussed along with future study directions.

Ultrathin quasi-hexagonal gold nanostructures for sensing arsenic in tap water

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 μg L-1 (1.51 nM), which is well below the regulatory limit of 10 μg L-1 established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 μg L-1. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.

Electrochemical oxidation of As(iii) on Pd immobilized Pt surface: kinetics and sensing performance

Pd nanoparticles were electrochemically immobilized on a Pt surface in the presence of sodium dodecyl sulfate (SDS) molecules to study the electrokinetics of arsenite oxidation reactions and the corresponding sensing activities. The X-ray photoelectron spectroscopy (XPS) analysis showed that on the Pt surface, Pd atoms exist as adatoms and the contents of Pd(0) and Pd(ii) were 75.72 and 24.28 at%, respectively, and the particle sizes were in the range of 61-145 nm. The experimental results revealed that the catalytic efficiency as well as the charge transfer resistance (at the redox potential of the Fe(ii)/Fe(iii) couple) increased in the order of Pt < Pt-Pd < Pt-Pdsds. A Pt-Pdsds electrode exhibited an open circuit potential (OCP) of 0.65 V in acidic conditions; however, when 50.0 mM NaAsO2 was present, the OCP value shifted to 0.42 V. It has been projected that the As(iii) oxidation proceeds using a sequential pathway: As(iii) → As(iv) → As(v). After optimization of the square wave voltammetric data, the limits of detection of As(iii) were obtained as 1.3 μg L-1 and 0.2 μg L-1 when the surface modification of the Pt surface was executed with Pd particles in the absence and presence of the SDS surfactant, respectively. Finally, real samples were analyzed with excellent recovery performance.

Recent Advances of Electrospun Nanofibrous Membranes in the Development of Chemosensors for Heavy Metal Detection

It is critical to detect and analyze the heavy metal pollutions in environments and foods. Chemosensors have been widely investigated for fast detection of analytes such as heavy metals due to their unique advantages. In order to improve the detection sensitivity of chemosensors, recently electrospun nanofibrous membranes (ENMs) have been explored for the immobilization of chemosensors or receptors due to their high surface-to-volume ratio, high porosity, easiness of fabrication and functionalization, controllability of nanofiber properties, low cost, easy detection, no obvious pollution to the detection solution, and easy post-treatment after the detection process. The purpose of this review is to summarize and guide the development and application of ENMs in the field of chemosensors for the detection of analytes, especially heavy metals. First, heavy metals, chemosensors, and four types of preparation methods for ENM-immobilized chemosensors/receptors are briefly introduced. And then, ENM-immobilized chemosensors/receptors and their application progresses for optical, electro, and mass detections of heavy metals are reviewed according to the four types of preparation methods. Finally, the application of ENM-immobilized chemosensors/receptors is summarized and an outlook is provided. The review will provide an instruction to the research and development of ENM-immobilized chemosensors/receptors for the detection of analytes.

Shape dependent stripping behavior of Au nanoparticles toward arsenic detection: evidence of enhanced sensitivity on the Au (111) facet

This work reports a comparative study of gold cubes {100}, octahedra {111}, and rhombic dodecahedra {110} toward the detection of arsenic for the first time. Au octahedral nanoparticles were found to exhibit the highest sensitivity.

A Versatile Environmental Impedimetric Sensor for Ultrasensitive Determination of Persistent Organic Pollutants (POPs) and Highly Toxic Inorganic Ions

An impedimetric sensor for persistent toxic substances, including organic pollutants and toxic inorganic ions is presented. The persistent toxic substances are detected using an ultrasensitive technique that is based on electron-transfer blockage. This depends on the formation of guest-host complexes, hydrogen bonding, or a cyclodextrin (CD)-metal complex (M_m(OH)_n-β-CD) structure between the target pollutants and β-CD.

Electrodeposited Bi-Au nanocomposite modified carbon paste electrode for the simultaneous determination of copper and mercury

An analytical anodic stripping voltammetry method has been developed for the simultaneous determination of copper and mercury at ultratrace levels using the Bi–AuNP modified CPE.

The size effect of Pt nanoparticles: a new route to improve sensitivity in electrochemical detection of As(iii)

The size effect of Pt nanoparticles on detection of arsenic is clarified and the phenomenon is explained by anodic oxygen-transfer reactions and binding energy.

The influence of gold nanoparticles on the electroactivity of nickel tetrasulfonated phthalocyanine

We report on the electrodeposition of gold nanoparticles ( AuNPs ) on a glassy carbon electrode (GCE) followed by deposition of nickel tetrasulfonated phthalocyanine ( NiTSPc ) film by electropolymerization (poly- NiTSPc -GCE) to form Poly- NiTSPc / AuNPs -GCE. The presence of the gold nanoparticles caused a lowering of the anodic and cathodic peak separation (ΔE p ) of ferricyanide from 126 mV on poly- NiTSPc to 110 mV on poly- NiTSPc / AuNPs . The electrooxidation of nitrite improved on modified electrodes compared to GCE, with the latter giving E p = 0.78 V and the modified electrodes gave E p = 0.62 V or 0.61 V. Poly- NiTSPc / AuNPs -GCE had higher currents compared to poly- NiTSPc -GCE. This indicates the enhancement effect caused by the AuNPs . Electrochemical impedance spectroscopy and chronoamperometric studies also showed that poly- NiTSPc / AuNPs -GCE was a better electrocatalyst than poly- NiTSPc -GCE or AuNPs -GCE.

Nanometer Materials Modified Electrodes for Detection of Heavy Metal Ions by Stripping Voltammetry

More and more heavy metal ions pollution events happen nowadays, so how to detect and remove heavy metal ions is a very important problem. Electrochemical method is relatively simple device, convenient automatic operation. Because of its high sensitivity and good selectivity, it becomes a good method to detect heavy metal ions. This paper summarized the detection of heavy metal ions by stripping voltammetry.

Arrays of microelectrodes: technologies for environmental investigations

Within this work it is our intention to provide an overview of the use of arrays or microelectrodes in the characterisation of environmental samples. Electrochemical methods are often a relatively simple and inexpensive alternative to spectroscopic or chromatographic methods for the analysis of a wide range of analytes. Arrays of microelectrodes display a number of advantages over simple planar macroelectrodes and the reasons for this will be detailed within this work. We will also describe some of the most common methods for constructing microarrays. The application of these arrays for analysis of environmental samples such as soil and water for heavy metal contamination has been the major focus of research in this field and comprises much of this review. However other systems will also be detailed such as determination of various anions or other samples such as pesticides.

Evaluation of trace heavy metal levels in soil samples using an ionic liquid modified carbon paste electrode

An ionic liquid n-octylpyridinium hexafluorophosphate (OPFP) modified carbon paste electrode was developed. This ionic liquid modified carbon electrode showed better electrochemical activities compared with the traditional carbon paste electrode which employed the paraffin oil as the binder. With the electrochemically deposited bismuth film, the developed electrode exhibited well-defined and separate stripping voltammetric peaks for cadmium and lead. The linear range of the bismuth film electrode was from 1.0 μg L(-1) to 100.0 μg L(-1) for both metal ions with a deposition time of 120 s and a deposition potential of -1.2 V in pH 4.5 acetate buffer solution. The detection limit was 0.10 μg L(-1) for cadmium and 0.12 μg L(-1) for lead with a deposition time of 180 s. The electrode was also applied to determine cadmium and lead in soil sample extracts. Results suggested that the proposed electrode was sensitive, reliable and effective for the determination of trace heavy metals.

Electrochemical Response of Platinum Ultrathin Layer Formed by Pulsed Laser Deposition

Ultrathin layer of platinum (ULPt) was deposited on glassy carbon (GC) substrate by using pulsed laser deposition (PLD) method, and electrochemical properties of the ULPt were discussed. The deposition was simply performed at room temperature with short deposition time. Atomic force microscopy and scanning electron microscopy images showed the flat surface of the ULPt. X-ray photoelectron spectroscopy (XPS) characterized the ULPt in the Pt(0) state, and biding energy of ULPt was positively shifted. These results indicated that nanostructure of Pt thin layer was formed. The electrochemical activity of the prepared ULPt on GC substrate was superior to a bulk Pt electrode regarding the potential and the magnitude of current on oxidizing hydrogen peroxide. This fast and easily prepared low-cost electrode had the potential to replace a conventional bulk metal electrode.