Determination of copper by AAS in tear fluid of patients with keratoconus

Visualized electrochemiluminescence detection of trace copper in practical food samples

Copper as a widely applied element in food supply chain can cause serious contamination issues that threats food safety. In this research, we present a quick and visible method for trace copper ion (Cu2+) quantification in practical food samples. Polymer dots (Pdots) were firstly conjugated with a copper-specific DNA aptamer and then tailored with rhodamine B (RhB) to extinguish the electrochemiluminescence (ECL) signal through a resonance energy transfer process. The selective release of RhB leads to signal restoration when exposed to trace Cu2+ levels, achieving remarkable linearity with the logarithm of Cu2+ concentration within the range of 1 ng/L to 10 μg/L with an impressively low limit of detection at 11.8 pg/L. Most notably, our device was also applicable on visualizing and quantifying trace Cu2+ (∼0.2 μg/g) in practical Glycyrrhiza uralensis Fisch. samples, underscoring its potential as a tool for the early prevention of potential copper contamination in food samples.

A Reaction-based Ratiometric Fluorescent Probe with Large STOKES Shift for Cu2+ in Neat Aqueous Solution

A novel reaction-based ratiometric fluorescent probe 1 for Cu2+ using picolinate as the reaction site and hemicyanine as the fluorophore was developed. 1 displayed maximum absorption peak at 355 nm and fluorescence emission peak at 500 nm, with large Stokes shift of 145 nm. Upon reaction with Cu2+, the maximum absorption and fluorescence emission peaks red-shifted to 390 nm and 570 nm respectively, owing to Cu2+-induced hydrolysis of the picolinate moiety in 1. Meanwhile, the solution of 1 turned from green to orange under a 365 nm UV lamp. 1 not only could detect Cu2+ ratiometrically by the ratios of both absorbance (A390 nm/A355 nm) and fluorescence intensity (F570 nm/F500 nm), but also displayed large Stokes shift, fast response, high sensitivity and excellent selectivity over other metal ions in neat aqueous solution.

Detection of Arsenic(V) by Fluorescence Sensing Based on Chlorin e6-Copper Ion

The high toxicity of arsenic (As) can cause irreversible harm to the environment and human health. In this study, the chlorin e6 (Ce6), which emits fluorescence in the infrared region, was introduced as the luminescence center, and the addition of copper ion (Cu2+) and As(V) provoked a regular change in fluorescence at 652 nm, whereas that of As(III) was 665 nm, which was used to optionally detect Cu2+, arsenic (As(III), and As(V)). The limit of detection (LOD) values were 0.212 μM, 0.089 ppm, and 1.375 ppb for Cu2+, As(III), and As(V), respectively. The developed method can be used to determine Cu2+ and arsenic in water and soil with good sensitivity and selectivity. The 1:1 stoichiometry of Ce6 with Cu2+ was obtained from the Job plot that was developed from UV-visible spectra. The binding constants for Cu2+ and As(V) were established to be 1.248 × 105 M-1 and 2.35 × 1012 M-2, respectively, using B-H (Benesi-Hildebrand) plots. Fluorescence lifetimes, B-H plots, FT-IR, and 1H-NMR were used to postulate the mechanism of Cu2+ fluorescence quenching and As(V) fluorescence restoration and the interactions of the two ions with the Ce6 molecule.

A ratiometric fluorescence sensor based on gold silver nanoclusters and tungsten disulfide quantum dots with simple fabrication for the detection of copper ions in river water

Copper plays a key role in the human body; meanwhile, excess Cu²⁺ ions can result in various diseases. Nanoclusters (NCs) are often used to measure Cu²⁺ ions, but there are two difficulties. On the one hand, a single probe of NCs is easily affected by environmental factors. On the other hand, it is difficult to mask the interference of Pb²⁺ ions and Cd²⁺ ions in the process of detecting Cu²⁺ ions. As a new type of quantum dots (QDs), tungsten disulfide quantum dots (WS₂-QDs) have some advantages of simple synthesis and stable luminescence properties. Stable WS₂-QDs with blue fluorescence are used as a reference probe, while gold silver nanoclusters (AuAgNCs) with red fluorescence are used as a response probe. A ratiometric fluorescent sensor was constructed by mixing the two styles of fluorescent probes, which is abbreviated as NCs/QDs. This nano-sensor can be used to detect the concentration of Cu²⁺ ions, in which the fluorescence of QDs does not change significantly, while the fluorescence of NCs can be quenched by Cu²⁺ ions. The concentration of Cu²⁺ ions can be determined as low as 0.12 μM with a linear range from 0.3 to 3 μM. The common interference caused by Pb²⁺ and Cd²⁺ ions can be eliminated by the phosphate buffer solution (PBS). This sensor was used to detect the concentration of Cu²⁺ in river water with satisfactory results.

Recent Advances in Nanopore Technology for Copper Detection and Their Potential Applications

Recently, nanopore technology has emerged as a promising technique for the rapid, sensitive, and selective detection of various analytes. In particular, the use of nanopores for the detection of copper ions has attracted considerable attention due to their high sensitivity and selectivity. This review discusses the principles of nanopore technology and its advantages over conventional techniques for copper detection. It covers the different types of nanopores used for copper detection, including biological and synthetic nanopores, and the various mechanisms used to detect copper ions. Furthermore, this review provides an overview of the recent advancements in nanopore technology for copper detection, including the development of new nanopore materials, improvements in signal amplification, and the integration of nanopore technology with other analytical methods for enhanced detection sensitivity and accuracy. Finally, we summarize the extensive applications, current challenges, and future perspectives of using nanopore technology for copper detection, highlighting the need for further research in the field to optimize the performance and applicability of the technique.

Solvent-free synthesis of nitrone-containing template as a chemosensor for selective detection of Cu(II) in water

A state-of-the-art method was developed for repurposing nitrone-containing compounds in the chemosensory field, the ability of the designed molecules to chelate metal cations was evaluated, and their unprecedented solubility in water was confirmed. A facile, rapid, and solvent-free method of synthesizing small molecular mass chemosensors was developed by using a modulative α-aryl-N-aryl nitrone template. α-(Z)-Imidazol-4-ylmethylen-N-phenyl nitrone (Nit1) and α-(Z)-2-pyridyl-N-phenyl nitrone (Nit2) were prepared in 15 min, isolated in less than 60 min with ca. 90% yield, and screened against nine metal cations. Nit1 is a small-molecular-mass compound (188 g mol^-1) that is water-soluble and has specificity for sensing Cu²⁺ with an association constant of K = 1.53 × 10¹⁰ and a limit of detection (LOD) of 0.06 ppm. These properties make Nit1 a competitive chemosensor for the detection of Cu²⁺ in aqueous solution. The nitrone-containing template used in this study is a step forward for new and small chemosensory entities.

Fluorescent Sensor for Copper(II) and Cyanide Ions via the Complexation-Decomplexation Mechanism with Di(bissulfonamido)spirobifluorene

A novel spirobifluorene derivative bearing two bissulfonamido groups is successfully synthesized by Sonogashira coupling. This compound exhibits a strong fluorescence quenching by Cu(II) ion in a 50% mixture between acetonitrile and 20 mM pH 7.0 N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (HEPES) buffer with a detection limit of 98.2 nM. However, this sensor also shows ratiometric signal shifts from blue to yellow in the presence of Zn(II), Pb(II), and Hg(II) ions. The static quenching mechanism is verified by the signal reversibility using ethylenediaminetetraacetic acid (EDTA) and the Stern-Volmer plots at varying temperatures. The Cu(II)-spirobifluorene complex shows a highly selective fluorescence enhancement upon the addition of CN- ion with the detection limit of 390 nM. The application of this complex for quantitative analysis of spiked CN- ion in real water samples resulted in good recoveries.