Detection Of Multiple Heavy Metal Ions Research Articles

A Sulfur-Containing Capsule-Based Metal-Organic electrochemical sensor for Super-Sensitive capture and detection of multiple Heavy-Metal ions

Development of an effective way for super-sensitive capture and sensing of heavy metal ions (HMIs) is a great challenge because they are extremely toxic to public health and environment. Herein, a new sulfur-containing nano-capsule-based electrochemical metal–organic framework (MOF) sensor [Co2(TMC4R)(1,4-BDC)2(μ2-H2O)]·3DMF·CH3OH·5CH3CN·H2O (Co-TMC4R-BDC) was designed for capture and detection of HMIs in aqueous solutions (TMC4R = tetra(4-mercaptopyridine)calix[4]resorcinarene, 1,4-BDC = 1,4-benzenedicarboxylic acid and DMF = N,N’-dimethylformamide). Remarkably, the designed MOF sensors exhibited excellent capture and detection performances for HMIs under the optimal experimental condition. The wide linear ranges of 0.05–12.0, 0.05–13.0, 0.1–17.0 and 0.75–18.0 μM are obtained for Cu2+, Pb2+, Cd2+ and Hg2+, respectively. The corresponding limit of detection (LOD) values are 13, 11, 26, and 18 nM, respectively. Particularly, the LOD values for Cu2+, Pb2+ and Cd2+ are lower than the standard drinking water ones from the World Health Organization. X-ray photoelectron spectroscopy (XPS) confirmed that the exposed S atoms of the nano-capsule units effectively captured HMIs through the complexation between S atoms and HMIs. Further, density functional theory (DFT) calculations indicated the presence of cation···π interactions between phenyl rings and HMIs. Thereby, the synergistic effects accomplished the effective capture and sensitive detection of HMIs. This work provides a feasible strategy for the capture and electrochemical detection of HMIs in an aqueous solution with the sulfur-containing MOF sensors.

Simultaneous Electrochemical Detection of Multiple Heavy-Metal Ions Based on Furfural/Reduced Graphene Oxide Composites

An efficient and sensitive electrochemical sensor for simultaneous detection of heavy metal ions was developed based on furfural/reduced graphene oxide composites (FF/RGO). The preparation of FF/RGO were performed through a one-step high-pressure assisted hydrothermal treatment, which is recommended as a green, convenient, and efficient way for the reduction of graphene oxide and the production of FF/RGO composites. RGO not only serves as the skeleton for furfural loading but also improves the conductivity of the composites in the matrix. FF/RGO with large specific surface area and abundant oxygen-containing functional groups was used to provide more binding sites for the effificient adsorption of heavy-metal ions due to the interaction between hydrophilic groups (–COOH, –OH, and –CHO) and metal cations. The developed sensor showed identifiable electrochemical response toward the heavy metal ions separately and simultaneously, exhibiting superior stability, outstanding sensitivity, selectivity and excellent analytical performance. Impressively, the sensor developed in this experiment has been successfully applied to the simultaneous determination of various heavy metal ions in actual samples, which has definitely exhibited a promising prospect in practical application.

A Series of Cobalt-Based Coordination Polymer Crystalline Materials as Highly Sensitive Electrochemical Sensors for Detecting Trace Cr(VI), Fe(III) Ions, and Ascorbic Acid

Convenient, sensitive, and reliable detection of multiple heavy-metal ions is a significant and challenging task with the use of high-yielding and easily synthesized materials. To solve this challenge, five cobalt-based coordination polymers (CPs), [Co2(4-dptb)2(1,3-BDC)2]·2H2O (1), [Co(4-dptb)(5-DIP)] (2), [Co(4-dptb)(5-NIP)] (3), [Co(4-dptb)(5-AIP)] (4), and [Co(4-dptb)(5-MIP)] (5) (4-dptb = N3,N4-bis(pyridin-4-ylmethyl)thiophene-3,4-dicarboxamide, 1,3-BDC = 1,3-benzenedicarboxylate, 5-DIP = 5-hydroxyisophthalic acid, 5-NIP = 5-nitroisophthalic acid, 5-AIP = 5-methylisophthalic acid, 5-MIP = 5-aminoisophthalic acid), have been synthesized by hydrothermal methods. A remarkable electrochemical sensing for Cr(VI) and Fe(III) was confirmed by cyclic voltammetry (CV) and current–time curves (i–t). The results showed that all CPs have a low limit of detection (LOD) of Cr(VI) and Fe(III) and fast electrochemical responses of within 3 s. At the same time, compounds 1–5 have a significant electrocatalytic oxidation effect on ascorbic acid (AA) and can be used as electrochemical sensors for AA.

Graphene Aerogel-Metal-Organic Framework-Based Electrochemical Method for Simultaneous Detection of Multiple Heavy-Metal Ions.

The development of an effective method for detecting heavy-metal ions remains a serious task because of their high toxicity to public health and environments. Herein, a new electrochemical method based on a graphene aerogel (GA) and metal-organic framework (MOF) composites was developed for simultaneous detection of multiple heavy-metal ions in aqueous solutions. The GA-MOF composites were synthesized via the in situ growth of the MOF UiO-66-NH2 crystal on the GA matrix. GA not only serves as the backbone for UiO-66-NH2 but also enhances the conductivity of the composites by accelerating the electron transfer in the matrix. UiO-66-NH2 worked as a binding site for heavy-metal ions because of the interaction between hydrophilic groups and metal cations. The detection performance of the GA-UiO-66-NH2 composite-modified electrodes was determined. The developed electrochemical method can be successfully applied for individual and simultaneous detection of heavy-metal ions, namely, Cd2+, Pb2+, Cu2+,and Hg2+, in aqueous solutions with high sensitivity and selectivity. The method can also be used for simultaneous detection of Cd2+, Pb2+, Cu2+, and Hg2+ in river water and the leaching solutions of soil and vegetable with high accuracy and reliability. This work provides a new approach for simultaneous detection of multiple heavy-metal ions in practical applications.

Bubble-Mediated Ultrasensitive Multiplex Detection of Metal Ions in Three-Dimensional DNA Nanostructure-Encoded Microchannels.

The development of rapid and sensitive point-of-test devices for on-site monitoring of heavy-metal contamination has great scientific and technological importance. However, developing fast, inexpensive, and sensitive microarray sensors to achieve such a goal remains challenging. In this work, we present a DNA-nanostructured microarray (DNM) with a tubular three-dimensional sensing surface and an ordered nanotopography. This microarray enables enhanced molecular interaction toward the rapid and sensitive multiplex detection of heavy-metal ions. In our design, the use of DNA tetrahedral-structured probes engineers the sensing interface with spatially resolved and density-tunable sensing spots that improve the microconfined molecular recognition. A bubble-mediated shuttle reaction was used inside the DNM-functionalized microchannel to improve the target-capturing efficiency. Using this novel DNM biosensor, the sensitive and selective detection of multiple heavy-metal ions (i.e., Hg2+, Ag+, and Pb2+) was achieved within 5 min, the detection limit was down to 10, 10, and 20 nM for Hg2+, Ag+, and Pb2+, respectively. The feasibility of our DNM sensor was further demonstrated by probing heavy-metal ions in real water samples with a direct optical readout. Beyond metal ions, this unique DNM sensor can easily be extended to in vitro bioassays and clinical diagnostics.

Synthesis of Bismuth-Nanoparticle-Enriched Nanoporous Carbon on Graphene for Efficient Electrochemical Analysis of Heavy-Metal Ions.

A BiNPs@NPCGS nanocomposite was designed for highly efficient detection of multiple heavy-metal ions by in situ synthesis of bismuth-nanoparticle (BiNP)-enriched nanoporous carbon (NPS) on graphene sheet (GS). The NPCGS was prepared by pyrolysis of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals deposited on graphene oxide and displayed a high surface area of 1251 m(2) g(-1) and a pore size of 3.4 nm. BiNPs were deposited on NPCGS in situ by chemical reduction of Bi(3+) with NaBH4 . Due to the restrictive effect of the pore/surface structure of NPCGS, the BiNPs were uniform and well dispersed on the NPCGS. The BiNPs@NPCGS showed good conductivity and high effective area, and the presence of BiNPs allowed it to act as an efficient material for anodic-stripping voltammetric detection of heavy-metal ions. Under optimized conditions, the BiNPs@NPCGS-based sensor could simultaneously determine Pb(2+) and Cd(2+) with detection limits of 3.2 and 4.1 nM, respectively. Moreover, the proposed sensor could also differentiate Tl(+) from Pb(2+) and Cd(2+). Owing to its advantages of simple preparation, environmental friendliness, high surface area, and fast electron-transfer ability, BiNPs@NPCGS showed promise for practical application in sensing heavy-metal ions.