Selective detection of Cu2+ and S2− by a colorimetric chemosensor: Experimental and theoretical calculations

A Highly Selective and Sensitive Nano-Silver sol Sensor for Hg2+ and Fe3+: Green Preparation and Mechanism

The development of highly selective and highly sensitive nanometer colorimetric chemical sensors is an urgent requirement in the immediate detection of heavy metal ions. In this work, silver-nanoparticle (Ag NPs)-based chemosensors were prepared by a simple and green method, in which the silver nitrate, carboxymethyl cellulose sodium (CMS) and Polyvinylpyrrolidone (PVP), and glucose are used as the silver source, double stabilizer and green reductant, respectively. The obtained colloidal CMS/PVP-Ag NPs showed a high dispersibility and stability, and creating a high selectivity and sensitivity to detect Hg2+ and Fe3+ with remarkable and rapid color variation. Low limits of detection (LOD) of 7.1 nM (0–20 μM) and 15.2 nM (20–100 μM) for Hg2+ and 3.6 nM for Fe3+ were achieved. More importantly, the CMS/PVP-Ag NPs has a high sensitivity even in a complex system with multiple heavy ions, the result of the practical ability to detect Hg2+ and Fe3+ in tap water and seawater reached a rational range of 98.33~104.2% (Hg2+) and 98.85~104.80% (Fe3+), indicating the great potential of the as-prepared nanocomposites colorimetric chemosensor for practical applications.

Recent Advances in Chemical Sensors for Soil Analysis: A Review

The continuously rising interest in chemical sensors’ applications in environmental monitoring, for soil analysis in particular, is owed to the sufficient sensitivity and selectivity of these analytical devices, their low costs, their simple measurement setups, and the possibility to perform online and in-field analyses with them. In this review the recent advances in chemical sensors for soil analysis are summarized. The working principles of chemical sensors involved in soil analysis; their benefits and drawbacks; and select applications of both the single selective sensors and multisensor systems for assessments of main plant nutrition components, pollutants, and other important soil parameters (pH, moisture content, salinity, exhaled gases, etc.) of the past two decades with a focus on the last 5 years (from 2017 to 2021) are overviewed.

Facile and Green Fabrication of Carrageenan-Silver Nanoparticles for Colorimetric Determination of Cu2+ and S2

In the present work, silver nanoparticles (AgNPs) were prepared by a simple and green method using carrageenan as reducing and capping agent. The as-synthesized carrageenan-AgNPs was demonstrated as an effective duel colorimetric sensing for selective and sensitive recognition of Cu²⁺ and S²⁻, which could be used to detect these ions with naked eyes. In addition, the possible sensing mechanism was that Cu²⁺ ions caused serious aggregation of carrageenan-AgNPs, which led to the color change of carrageenan-AgNPs. AgNPs were etched by S²⁻ forming Ag₂S, which played an important role in the determination of S²⁻ ions. Furthermore, it has been successfully applied to the determination of Cu²⁺ and S²⁻ in tap water and lake water, showing its great potential for the analysis of environmental water samples.

Highly Sensitive Dansyl-Based Chemosensor for Detection of Cu2+ in Aqueous Solution and Zebrafish

A new dansyl-based chemosensor (2-(4-((5-(dimethylamino)naphthalen-1-yl)sulfonyl)piperazin-1-yl)-N-(quinolin-8-yl)acetamide) (DC) for detecting Cu2+ was synthesized and characterized. DC showed great selectivity to Cu2+ by a fluorescent "on-off" detection method. Job plot, ESI-mass spectroscopy, and 1H NMR titration suggested a 1 to 1 binding mode between DC and Cu2+. The detection limit was determined to be 43 nM, which is greatly below the WHO guidelines. In addition, DC can be applied to real samples and zebrafish imaging. The fluorescence quenching mechanism was proposed as the enhancement of intramolecular charge transfer with calculations.