EDTA Assisted Highly Selective Detection of As3+ on Au Nanoparticle Modified Glassy Carbon Electrodes: Facile in Situ Electrochemical Characterization of Au Nanoparticles

Practical Strategy for Arsenic(III) Electroanalysis without Modifier in Natural Water: Triggered by Iron Group Ions in Solution

Significant progress has been made in nanomaterial-modified electrodes for highly efficient electroanalysis of arsenic(III) (As(III)). However, the modifiers prepared using some physical methods may easily fall off, and active sites are not uniform, causing the potential instability of the modified electrode. This work first reports a promising practical strategy without any modifiers via utilizing only soluble Fe³⁺ as a trigger to detect trace-level As(III) in natural water. This method reaches an actual detection limit of 1 ppb on bare glassy carbon electrodes and a sensitivity of 0.296 μA ppb^-1 with excellent stability. Kinetic simulations and experimental evidence confirm the codeposition mechanism that Fe³⁺ is preferentially deposited as Fe⁰, which are active sites to adsorb As(III) and H⁺ on the electrode surface. This facilitates the formation of AsH₃, which could further react with Fe²⁺ to produce more As⁰ and Fe⁰. Meanwhile, the produced Fe⁰ can also accelerate the efficient enrichment of As⁰. Remarkably, the proposed sensing mechanism is a general rule for the electroanalysis of As(III) that is triggered by iron group ions (Fe²⁺, Fe³⁺, Co²⁺, and Ni²⁺). The interference analysis of coexisting ions (Cu²⁺, Zn²⁺, Al³⁺, Hg²⁺, Cd²⁺, Pb²⁺, SO₄^2-, NO₃^-, Cl^-, and F^-) indicates that only Cu²⁺, Pb²⁺, and F^- showed inhibitory effects on As(III) due to the competition of active sites. Surprisingly, adding iron power effectively eliminates the interference of Cu²⁺ in natural water, achieving a higher sensitivity for 1-15 ppb As(III) (0.487 μA ppb^-1). This study provides effective solutions to overcome the potential instability of modified electrodes and offers a practical sensing platform for analyzing other heavy-metal anions.

A recent advancement on the applications of nanomaterials in electrochemical sensors and biosensors

Industrialization and globalization, both on an international and local scale, have caused large quantities of toxic chemicals to be released into the environment. Thus, developing an environmental pollutant sensor platform that is sensitive, reliable, and cost-effective is extremely important. In current years, considerable progress has been made in the expansion of electrochemical sensors and biosensors to monitor the environment using nanomaterials. A large number of emerging biomarkers are currently in existence in the biological fluids, clinical, pharmaceutical and bionanomaterial-based electrochemical biosensor platforms have drawn much attention. Electrochemical systems have been used to detect biomarkers rapidly, sensitively, and selectively using biomaterials such as biopolymers, nucleic acids, proteins etc. In this current review, several recent trends have been identified in the growth of electrochemical sensor platforms using nanotechnology such as carbon nanomaterials, metal oxide nanomaterials, metal nanoparticles, biomaterials and polymers. The integration strategies, applications, specific properties and future projections of nanostructured materials for emerging progressive sensor platforms are also observed. The objective of this review is to provide a comprehensive overview of nanoparticles in the field of electrochemical sensors and biosensors.

Recent Progress in Nanobiosensors for Precise Detection of Blood Glucose Level

Diabetes mellitus (DM) follows a series of metabolic diseases categorized by high blood sugar levels. Owing to the increasing diabetes disease in the world, early diagnosis of this disease is critical. New methods such as nanotechnology have made significant progress in many areas of medical science and physiology. Nanobiosensors are very sensible and can identify single virus particles or even low concentrations of a material that can be inherently harmful. One of the main factors for developing glucose sensors in the body is the diagnosis of hypoglycemia in individuals with insulin-dependent diabetes. Therefore, this study aimed to evaluate the most up-to-date and fastest glucose detection method by nanosensors and, as a result, faster and better treatment in medical sciences. In this review, we try to explore new ways to control blood glucose levels and treat diabetes. We begin with a definition of biosensors and their classification and basis, and then we examine the latest biosensors in glucose detection and new biosensors applications, including the artificial pancreas and updating quantum graphene data.

A novel and sensitive electrochemical sensor based on nanoporous gold for determination of As(III)

Three-dimensional porous gold nanoparticles (NPG) were synthesized in situ on indium-doped tin oxide (ITO) substrates by a green and convenient one-step electrodeposition method to achieve super-sensitive As(III) detection. The introduction of NPG method not only greatly improves the electron transfer capacity and surface area of sensor interface but provides more active sites for As(III) enrichment, thus boosting sensitivity and selectivity. The sensor was characterized by scanning electron microscopy, energy dispersion spectroscopy, differential pulse anode stripping voltammetry (DPASV), and electrochemical impedance to evaluate its morphology, composition, and electrochemical performance. The wall thickness of NPG was customized by optimizing the concentration of electroplating solution, dissolved electrolyte, deposition potential, and reaction time. Under optimal conditions, the electrochemical sensor showed a wide linear range from 0.1 to 50 μg/L As(III), with a detection limit (LOD) of 0.054 μg/L (S/N = 3). The LOD is far below 10 μg/L, the recommended maximum value by the world health organization for drinking water. Stability, reproducibility, and repeatability of NGP/ITO were determined to be 2.77%, 4.9%, and 4.1%, respectively. Additionally, the constructed sensor has been successfully applied to determine As(III) in three actual samples, and the results are in good agreement with that of hydride generation atomic fluorescence spectrometry (AFS). Graphical abstract.

Fabrication of Robust Hydrogen Evolution Reaction Electrocatalyst Using Ag2Se by Vacuum Evaporation

Much research has been done on reliable and low-cost electrocatalysts for hydrogen generation by water splitting. In this study, we synthesized thin films of silver selenide (Ag₂Se) using a simple thermal evaporation route and demonstrated their electrocatalytic hydrogen evolution reaction (HER) activity. The Ag₂Se catalysts show improved electrochemical surface area and good HER electrocatalytic behavior (367 mV overpotential @ 10 mA·cm⁻², exchange current density: ~1.02 × 10⁻³ mA·cm⁻², and Tafel slope: 53 mV·dec⁻¹) in an acidic medium). The reliability was checked in 0.5 M sulfuric acid over 20 h. Our first-principles calculations show the optimal energy of hydrogen adsorption, which is consistent with experimental results. The works could be further extended for finding a new catalyst by associating the selenide, sulfide or telluride-based materials without complex catalyst synthesis procedures.

Colorimetric Assay Conversion to Highly Sensitive Electrochemical Assay for Bimodal Detection of Arsenate Based on Cobalt Oxyhydroxide Nanozyme via Arsenate Absorption

This study reports a novel and convenient bimodal method for label-free and signal-off detection of arsenate in environmental samples. Cobalt oxyhydroxide (CoOOH) nanoflakes with facile preparation and intrinsic peroxidase-like activity as nanozyme can efficiently catalyze the conversion of chromogenic substrate such as 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with the presence of H₂O₂ into green-colored oxidation products. CoOOH nanoflakes can specifically bind with arsenate via electrostatic attraction and As-O bond interaction, which gives rise to inhibition of the peroxidase-like activity of CoOOH. Thus, through arsenate specific inhibition of CoOOH nanozyme toward ABTS catalysis, a simple colorimetric method was developed for arsenate detection with a detection limit of 3.72 ppb. Based on the system of CoOOH nanozyme and ABTS substrate, this colorimetric method can be converted into an electrochemical sensor for arsenate assay by the utilization of CoOOH nanoflake-modified electrode. The electrochemical measurement can be realized by chronoamperometry, which showed more sensitive and a lower limit of detection as low as 56.1 ppt. The applicability of this bimodal method was demonstrated by measuring arsenate and total arsenic in different real samples such as natural waters and soil extracted solutions, and the results are of satisfactory accuracy as confirmed by inductively coupled plasma mass spectrometry analysis. The bimodal strategy offers obvious advantages including a label-free step, convenient operation, on-site assay, low cost, and high sensitivity, which is promising for reliable detection of arsenate and total arsenic in environmental samples.

Preparation of Au nanoparticles on a magnetically responsive support via pyrolysis of a Prussian blue composite

A strategy is described for the direct preparation of Au nanoparticles (AuNPs) on a Fe-based support, coated with porous carbon (PC), via pyrolysis of an AuCN functionalised Prussian Blue (PB) metal organic framework (MOF). The composite starting material was prepared with an even distribution of AuCN on the surface via galvanic exchange of PB with a gold salt in solution. The resulting structures after pyrolysis were shown to be active Au-based nanomaterials for model applications including catalysis (4-nitrophenol reduction) and electroanalysis (arsenic (III) detection), suggesting broad application where Au nanoparticles are required at a liquid-solid interface. The Fe based support was seen to consist of Fe, Fe₃C and Fe₄C phases, and the carbon coating increased the stability and improved the conductivity of the materials. The temperature of pyrolysis was seen to affect the activity of the supported nanoparticles, with an increased Au surface area obtained at the higher pyrolysis temperature (650 °C) tested. A general strategy is thus confirmed for preparation of noble metal nanoparticles evenly distributed on a magnetic support, allowing easy separation of catalysts from products in heterogeneous applications.

UV-Light-Induced Improvement of Fluorescence Quantum Yield of DNA-Templated Gold Nanoclusters: Application to Ratiometric Fluorescent Sensing of Nucleic Acids

The use of DNA as a template has been demonstrated as an effective method for synthesizing different-sized silver nanoclusters. Although DNA-templated silver nanoclusters show outstanding performance as fluorescent probes for chemical sensing and cellular imaging, the synthesis of DNA-stabilized gold nanoclusters (AuNCs) with high fluorescence intensity remains a challenge. Here a facile, reproducible, scalable, NaBH4-free, UV-light-assisted method was developed to prepare AuNCs using repeats of 30 adenosine nucleotides (A30). The maximal fluorescence of A30-stabilized AuNCs appeared at 475 nm with moderate quantum yield, two fluorescence lifetimes, and a small amount of Au(+) on the surface of the Au core. Results of size-exclusion chromatography revealed that A30-stabilized AuNCs were more compact than A30. A series of control experiments showed that UV light played a dual role in the reduction of gold-ion precursors and the decomposition of citrate ions. A30 also acted as a stabilizer to prevent the aggregation of AuNCs. In addition, single-stranded DNA (ssDNA) consisting of an AuNC-nucleation sequence and a hybridization sequence was utilized to develop a AuNC-based ratiometric fluorescent probe in the presence of the double-strand-chelating dye SYBR Green I (SG). Under conditions of single-wavelength excitation, the combination of AuNC/SG-bearing ssDNA and perfectly matched DNA emitted fluorescence at 475 and 525 nm, respectively. The formed AuNC/SG-bearing ssDNA enabled the sensitive, selective, and ratiometric detection of specific nucleic acid targets. Finally, the AuNC-based ratiometric probes were successfully applied to determine specific nucleic acid targets in human serum.