Detection of Hg2+ ions in aqueous medium using an indole-based fluorescent probe: Experimental and theoretical investigations

Mercury (Hg2+) Sensing Using Coumarin-Derived Fluorescent Chemo-Sensors: An Intuitive Development from 2015 to 2023

Mercury is known as a highly toxic metal that is poisonous even if present in a trace amount. Generally, it enters in the food chain (especially fish) and water resources via different pathways and leads to harmful effects. Owing to the detrimental nature of the metal, traditionally several methods were employed by researchers for regular monitoring of the mercury metal ions. However, these methods are associated with many limitations like high cost of technical expertise, and intricacy of the detection procedure. So, using these methods to detect mercury ions in real time is challenging. Therefore, in recent years fluorescent-based analytical tools emerged rapidly. Among the various fluorescent organic scaffolds, coumarin has been scorching, owing to quick response, light stability, high sensitivity, good selectivity, excellent fluorescence intensity, and fluorescence quantum yield. This review provides a deep dive into the coumarin-derived chemo-sensors development throughout 2015-2023. We anticipate that the review will assist to broad scientific community as a reference document to design more interesting sensors.

A Review on Pyrazolines as Colorimetric Fluorescent Chemosensors for Cu2

The Pyrazoline derivatives display promising potential as sensitive and selective chemosensors for detecting Cu2+ ions. It has undergone screening for its sensing behavior with various metals using absorption, emission spectroscopic techniques. Their unique structure incorporates both donating and accepting sites, characterized by delocalized orbitals. These derivatives exhibit notable chromogenic and fluorogenic capabilities facilitated by intramolecular charge transfer. The sensors based on pyrazoline demonstrate exceptional selectivity, low detection limits, and precise detection of metal ions, particularly Cu2+. This review offers a comprehensive summary of recent discoveries concerning as pyrazoline-based "On-Off" chemosensors. The discussion places emphasis on exploring the design and photophysical properties of these chemosensors, with the primary objective of detecting Cu2+ metal ions. The unique features of pyrazoline derivatives make them promising candidates for practical applications in environmental and biological monitoring, showcasing their potential significance in advancing sensing technologies.

Small-molecule fluorogenic probes based on indole scaffold

Indoles are the most versatile organic N-heterocyclic compounds widely present in bioactive natural products and used in different fields such as coordination chemistry, pharmacy, dyes, and medicine, as well as in the biology and polymer industries. More recently, the indole scaffold has been widely used in analytical chemistry for the design and development of small-molecule fluorescent chemosensors in the fields of molecular recognition and molecular imaging. The indole-based chemosensor derivatives contain heteroatoms like N-, O-, and S-, through which they interact with analytes (cations, anions, and neutral species), producing measurable analytical signals that can be used for the fluorimetric and colorimetric detection of different analytes in biological, agricultural and environmental samples. This review focuses on indole-based small-molecule fluorimetric and colorimetric chemosensors for detecting cations, anions, and neutral species in a comprehensive manner. Furthermore, the recognition mechanisms are discussed in detail, which could help researchers design and develop more powerful and efficient fluorescent chemosensors in the near future.

Chemosensors based on N-heterocyclic dyes: advances in sensing highly toxic ions such as CN- and Hg2

CN- and Hg2+ ions are harmful to both the environment and human health, even at trace levels. Thus, alternative methods for their detection and quantification are highly desirable given that the traditional monitoring systems are expensive and require qualified personnel. Optical chemosensors (probes) have revolutionized the sensing of different species due to their high specificity and sensitivity, corresponding with their modular design. They have also been used in aqueous media and different pH ranges, facilitating their applications in various samples. The design of molecular probes is based on organic dyes, where the key species are N-heterocyclic compounds (NHCs) due to their proven photophysical properties, biocompatibility, and synthetic versatility, which favor diverse applications. Accordingly, this review aims to provide an overview of the reports from 2016 to 2021, in which fluorescent probes based on five- and six-membered N-heterocycles are used for the detection of CN- and Hg2+ ions.

An ultrasensitive ratiometric fluorescent probe for the detection of Hg2+ and its application in cell and zebrafish

Mercury is a highly toxic metal element, and the accumulation of mercury in the human body can cause great harm, including but not limited to brain damage, kidney damage and behavioral disorders. Therefore, an effective way to detect mercury ions in the environment is urgently needed. In this study, a novel fluorescent probe (CP-Hg) was synthesized with coumarin as the fluorophore and propanethiol as the recognition receptor. The probe was characterized with high sensitivity (detection limit is approximately 0.5 nM) and selectivity. Note that the probe can react with mercury ions with a distinct color change. In addition, it has been proved to have low toxicity and successfully applied to detect mercury in water samples, macrophages and zebrafish model.