Dual fluorometric and colorimetric sensor based on quenching effect of copper (II) sulfate on the copper nanocluster for determination of sulfide ion in water samples

Challenges and Opportunities of Using Fluorescent Metal Nanocluster-Based Colorimetric Assays in Medicine

Development of rapid colorimetric methods based on novel optical-active metal nanomaterials has provided methods for the detection of ions, biomarkers, cancers, etc. Fluorescent metal nanoclusters (FMNCs) have gained a lot of attention due to their unique physical, chemical, and optical properties providing numerous applications from rapid and sensitive detection to cellular imaging. However, because of very small color changes, their colorimetric applications for developing rapid tests based on the naked eye or simple UV-vis absorption spectrophotometry are still limited. FMNCs with peroxidase-like activity have significant potential in a wide variety of applications, especially for point-of-care diagnostics. In this review, the effect of using various capping agents and metals for the preparation of nanoclusters in their colorimetric sensing properties is explored, and the synthesis and detection mechanisms and the recent advances in their application for ultrasensitive chemical and biological analysis regarding human health are highlighted. Finally, the challenges that remain as well as the future perspectives are briefly discussed. Overcoming these limitations will allow us to expand the nanocluster's application for colorimetric diagnostic purposes in medical practice.

One-step hydrothermal synthesis of fluorescent silicon nanoparticles for sensing sulfide ions and cell imaging

We have presented a hydrothermal approach for synthesizing fluorescent silicon nanoparticles (F-SiNPs) with yellow-green emission. The obtained F-SiNPs exhibited excellent stability and good biocompatibility. By virtue of the specific reaction between S^2- and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), colorimetric assay of S^2- was realized with a good linear range of 0-100 μM. The colorimetric detection system could be further combined with F-SiNPs to construct a probe for fluorescence turn-off sensing S^2- in aqueous solution due to inner filter effect. In the fluorescent detection system, a good linearity with S^2- concentration in the range of 0-50 μM was accomplished. And as low as 0.1 μM S^2- was successfully detected. Moreover, the F-SiNPs displayed low cytotoxicity and good biocompatibility, and was further utilized for cell imaging. These results demonstrated the promising applications of F-SiNPs in S^2- analysis and bioimaging.

A Quinoxaline-Naphthaldehyde Conjugate for Colorimetric Determination of Copper Ion

This work facilitates detection of bivalent copper ion by a simple Schiff base probe QNH based on a quinoxaline−naphthaldehyde framework. The detailed study in absorption spectroscopy and theoretical aspects and crystal study of the probe and probe−copper complex has been discussed. The detection limit of the probe in the presence of Cu²⁺ is 0.45 µM in HEPES−buffer/acetonitrile (3/7, v/v) medium for absorption study. The reversibility of the probe−copper complex has been investigated by EDTA. The selective visual detection of copper has been established also in gel form.

Synthesis optimization of rich-urea carbon-dots and application in the determination of H2S in rich- and barren-liquids of desulphurizing solutions

In the research of carbon dots (CDs) containing various nitrogen sources, it was first found that urea/citric acid-CDs showed a selective discolouration reaction with sulphide ions. Therefore, by optimizing various synthesis and detection conditions of the CDs determining sulfur ions, such as the raw material ratio, temperature, time, pH, and oxidation atmosphere in the CD synthesis, a discolour CD-probe method for trace-level sulphide ions was developed. The method is environmentally friendly, shows two linear-response ranges in 0.050-1.0 mg L^-1 (A = -0.0827c + 0.8366) and 1.0-15 mg L^-1 S^2- (A = -0.0209c + 0.7587) and can be used for the high and low concentration quantification of sulphide in various wastewaters. Subsequently, in order to realize the separation and detection of sulphide ions in wastewaters or rich- and barren-liquids containing N-methyldiethanolamine and other substances in desulphurizing solutions, an automatic pretreatment system was also established.

A novel selective detection method for sulfide in food systems based on the GMP-Cu nanozyme with laccase activity

A selective and sensitive colorimetric strategy for sulfide analysis was developed using GMP-Cu nanozymes with a laccase-like activity. This research discovered for the first time that sulfide could significantly enhance the catalytic activity of the GMP-Cu nanozymes by about 3.5 folds. The enhanced laccase activities duo to two reasons. First, Cu²⁺ in GMP-Cu nanozymes was reduced to Cu⁺. The other reason was the formation of Cu-S bond which was beneficial to accelerate the electron transfer rate to improve catalytic activity. Therefore, this method showed an excellent selectivity for sulfide. And it had a linear relationship in the sulfide concentration range of 0-220 μmol/L with a detection limit of 0.67 μmol/L. Furthermore, the proposed method was successfully applied to examine sulfide in the food systems. This new method may be used in sulfide detection to improve food quality and safety.

Synthesis of Copper Nanocluster and Its Application in Pollutant Analysis

Copper nanoclusters (Cu NCs) with their inherent optical and chemical advantages have gained increasing attention as a kind of novel material that possesses great potential, primarily in the use of contaminants sensing and bio-imaging. With a focus on environmental safety, this article comprehensively reviews the recent advances of Cu NCs in the application of various contaminants, including pesticide residues, heavy metal ions, sulfide ions and nitroaromatics. The common preparation methods and sensing mechanisms are summarized. The typical high-quality sensing probes based on Cu NCs towards various target contaminants are presented; additionally, the challenges and future perspectives in the development and application of Cu NCs in monitoring and analyzing environmental pollutants are discussed.

A high-efficiency salamo-based copper(ii) complex double-channel fluorescent probe

In this paper, a salamo-based copper(ii) complex probe L-Cu²⁺ was synthesized, which combined with copper(ii) ions to form L-Cu²⁺ for the detection of S²⁻ and had a good fluorescence chemical response. Through spectral analysis, we found that S²⁻ could be identified with high sensitivity and selectivity in the presence of various anions and could be used for the detection of S²⁻ by the naked eye. With the addition of S²⁻, the solution color changed from colorless to bright yellow. UV absorption, fluorescence and other characterization methods were carried out, and the mechanism of action was determined. In addition, we performed a visual inspection of H₂S gas, and the probe L-Cu²⁺ could detect S²⁻ in the gas molecules, revealing its potential application value in biology and medicine.

A highly sensitive and selective salamo-based copper(ii) complex probe, L-Cu²⁺, was synthesized; it could be used for the detection of S²⁻ by UV and fluorescence spectroscopies. And it also could detect S²⁻ in gas molecules.