Simple and rapid mercury ion selective electrode based on 1-undecanethiol assembled Au substrate and its recognition mechanism

Electroless Deposition: A Nonelectroreduction Anodic Stripping Analysis Strategy for Heavy Metal Ions Using Nitrogen-Doped Graphdiynes/Carbon Nanotubes

In the past decades, the anodic stripping voltammetry (ASV) method has been the most commonly utilized electrochemical proposal for detecting trace amounts of heavy metal ions (HMIs). It involves two steps: HMI electroreduction and zerovalent metal reoxidation. However, it has been overlooked that the testing process could be simplified, made more efficient, and energy-saving by avoiding the electroreduction step. In this study, it is revealed that graphdiynes (GDY) as a remarkable material can induce the accumulation and self-reduction of Hg2+ and Cu2+ through a simple electroless deposition process, leading to the formation of zerovalent metals (Hg0 and Cu0). Inspired by this property, a nonelectroreduction ASV (NSV) sensing strategy for HMI detection was then proposed innovatively. By synthesizing a nitrogen-doped GDY/carbon nanotubes (N-GDY/CNTs) nanohybrid as the electrode material, the introduction of CNTs aims to enhance the conductivity and prevent GDY aggregation, while N-doping further improves the sensing performance. The results showed that the N-GDY/CNTs-based NSV sensing strategy not only eliminates the related electroreduction process referring to the common ASV strategy but also enables sensitive detection of Cu2+ and Hg2+ with extremely low detection limits (0.67 nM for Cu2+ and 0.33 nM for Hg2+). This indicates its great potential for wide applications in HMI testing.

Rapid Determination of Mercury Ions in Environmental Water Based on an N-Rich Covalent Organic Framework Potential Sensor

In this article, an N-rich covalent organic framework (COFTFPB-TZT) was successfully synthesized using 4,4′,4′-(1,3,5-triazine-2,4,6-triyl) trianiline (TZT), and 4-[3,5-bis (4-formyl-phenyl) phenyl] benzaldehyde (TFPB). The as-prepared COFTFPB-TZT possesses irregular cotton wool patches with a large specific surface area. A novel selective electrode based on COFTFPB-TZT was used for the determination of Mercury ions. The abundance of N atoms in COFTFPB-TZT provides more coordination sites for Hg2+ adsorption, resulting in a change in the surface membrane potential of the electrode to selectively recognize Hg2+. Under optimal experimental conditions, the ion-selective electrode shows a good potential response to Hg2+, with a linear range of 1.0 × 10−9∼1.0 × 10−4, a Nernst response slope of 30.32 ± 0.2 mV/-PC at 25°C and a detection limit of 4.5 pM. At the same time, the mercury-ion electrode shows a fast response time of 10 s and good reproducibility and stability. The selectivity coefficients for Fe2+, Zn2+, As3+, Cr6+, Cu2+, Cr3+, Al3+, Pb2+, NH4+, Ag+, Ba2+, Mg2+, Na+, and K+ are found to be small, indicating no interference in the detection system. The proposed method can be successfully applied to the determination of Hg2+ in 3 typical environmental water samples, with a recovery rate of 98.6–101.8%. In comparison with the spectrophotometric method utilizing dithizone, the proposed method is simple and fast and holds great potential application prospects in environmental water quality monitoring and other fields.

Design and Characterization of Electrochemical Sensor for the Determination of Mercury(II) Ion in Real Samples Based upon a New Schiff Base Derivative as an Ionophore

The present paper provides a description of the design, characterization, and use of a Hg2+ selective electrode (Hg2+-SE) for the determination of Hg2+ at ultra-traces levels in a variety of real samples. The ionophore in the proposed electrode is a new Schiff base, namely 4-bromo-2-[(4-methoxyphenylimino)methyl]phenol (BMPMP). All factors affecting electrode response including polymeric membrane composition, concentration of internal solution, pH sample solution, and response time were optimized. The optimum response of our electrode was obtained with the following polymeric membrane composition (% w/w): PVC, 32; o-NPOE, 64.5; BMPMP, 2 and NaTPB, 1.5. The potentiometric response of Hg2+-SE towards Hg2+ ion was linear in the wide range of concentrations (9.33 × 10-8-3.98 × 10-3 molL-1), while, the limit of detection of the proposed electrode was 3.98 × 10-8 molL-1 (8.00 μg L-1). The Hg2+-SE responds quickly to Hg2+ ions as the response time of less than 10 s. On the other hand, the slope value obtained for the developed electrode was 29.74 ± 0.1 mV/decade in the pH range of 2.0-9.0 in good agreement with the Nernstian response (29.50 mV/decade). The Hg2+-SE has relatively less interference with other metal ions. The Hg2+-SE was used as an indicator electrode in potentiometric titrations to estimate Hg2+ ions in waters, compact fluorescent lamp, and dental amalgam alloy and the accuracy of the developed electrode was compared with ICP-OES measurement values. Moreover, the new Schiff base (BMPMP) was synthesized and characterized using ATR-FTIR, elemental analysis, 1H NMR, and 13C NMR. The PVC membranes containing BMPMP as an ionophore unloaded and loaded with Hg(II) are reported by scanning electron microscope images (SEM) along with energy-dispersive X-ray spectroscopy (EDX) spectra.

Chitosan-Thiobarbituric Acid: A Superadsorbent for Mercury

In the present investigation, chitosan (CH) was supramolecularly cross-linked with thiobarbituric acid to form CT. CT was well characterized by UV, scanning electron microscopy-energy-dispersive X-ray analysis, Fourier transform infrared, NMR, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction analyses, and its adsorption potential for elemental mercury (Hg⁰), inorganic mercury (Hg²⁺), and methyl mercury (CH₃Hg⁺) was investigated. Adsorption experiments were conducted to optimize the parameters for removal of the mercury species under study, and the data were analyzed using Langmuir, Freundlich, and Temkin adsorption isotherm models. CT was found to have high adsorption capacities of 1357.69, 2504.86, and 2475.38 mg/g for Hg⁰, Hg²⁺, and CH₃Hg⁺, respectively. The adsorbent CT could be reused up to three cycles by eluting elemental mercury using 0.01 N thiourea, inorganic mercury using 0.01 N perchloric acid, and methyl mercury with 0.2 N NaCl.