Novel Fluorescent Probe Unveiled for Mercury Detection

Mercury is a metallic element with an atomic number of 80. When released in the environment, mercury can pose a major risk to the ecosystem and to human health. As a result, accurate and selective detection methods are needed to monitor and quantify the presence of mercury to ensure the toxicity levels are kept under control.

Beautiful mesmerize colorful pattern of liquid silver, mercury, beautiful background | Image Credit: © DNY3D - stock.adobe.com

A recent study published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy by lead author Young-A Son from Chungnam National University explored this very issue. Son’s study introduces a novel approach to detect and quantify mercury ions (Hg²⁺), marking a step forward in environmental and health monitoring (1).

The study focused on an underexplored topic in mercury detection, which is on the isoquinoline core (IQ). IQ has not been covered extensively in research efforts because of synthetic challenges that traditional methods, such as fluorescent organic small-molecule probes, do not have (1).

In this study, researchers discovered a synthetic route to produce a highly functionalized isoquinoline-based probe, named IQ(1). The synthesis involves the in situ generation of ammonia, followed by an intermolecular [5C + 1 N] aza-annulation reaction with a ketendithioacetal-based precursor, P-IQ (1).

One of the highlights of the study was the ability of IQ to recognize Hg²⁺ ions in a water:acetonitrile solution. This demonstrated a fluorescent quenching behavior via an intramolecular charge transfer (ICT-off) mechanism (1). Extensive spectroscopic and computational analyses validated the proposed mechanisms, while reversible studies confirmed IQ's secondary recognition effect on cysteine (1).

The probe displayed a high binding constant and a low limit of detection (LOD), making it highly sensitive for practical applications (1). Furthermore, IQ was successfully employed to assess mercury ion content in real water samples, showcasing its effectiveness in water quality monitoring (1).

Another important finding in the study is regarding IQ’s versatility and discovering where else it could be applied. The study demonstrated that IQ could be used in several additional applications, including the development of thin-layer chromatography (TLC) strips, Whatman filter-paper strips, and a low-cost, portable Arduino-based platform (1). By interfacing an Arduino microcontroller with an RGB sensor, researchers were able to detect color changes and quantify mercury concentration with respect to RGB values, enhancing the probe's practical utility (1).

The research presents a short and efficient synthetic route to unleash the potential of the IQ scaffold as a fluorescent probe for rapid and robust detection of mercury ions.

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Reference

(1) Bartwal, G.; Manivannan, R.; Son, Y.-A. An ICT-based Highly Fluorescent Isoquinoline Scaffold for Selective Hg(II) Detection in Real-water Samples: Development of a Smart, Low-cost RGB-Arduino Electronic Platform. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2024, 309, 123812. DOI: 10.1016/j.saa.2023.123812