New Fluorescent Sensors Make it Possible to Detect the Concentration of Mercury in Water

10:46, March 7, 2023

Therefore, they can be used to detect pollutants in water

Scientists from the UrFU, together with Italian and Bulgarian colleagues, synthesised new heterocyclic fluorophores - four types of carboxamides of 2-aryl-1,2,3-triazoles. Their photophysical properties have been investigated under different conditions - solvents and their binary mixtures with water. Sensors based on the fluorophores obtained were sensitive to mercury, so they can be used to detect mercury concentrations in water. Further research will focus on determining the possibility of using these fluorophores to target medicines to affected organs. The authors have published an article on their research and results in the journal Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy.

"A disadvantage of organic fluorophores is their poor solubility in water and aqueous environments. At the same time, when water is added to organic solvents, most dyes and fluorophores have fluorescence quenching. However, in 2001, Professor Ben Zhong Tan of the Chinese University of Hong Kong found that some fluorophores observed not quenching, but rather an increase the fluorescence intensity. This is due to the formation of much larger particles, or nano-aggregates, from the molecules of fluorophores. Tan's discovery was of great significance. Much scientific effort has been devoted to studying the mechanism of his discovery, as well as to the design and synthesis of new fluorophores with the effect of increasing the emission. The fluorophores we obtained have also demonstrated in a mixture of organic solvent and water the effect described by Tang, and with a particular intensity. This opens the way to the practical application of the obtained fluorophores in various fields, especially in the aquatic environment," says Natalya Belskaya, Full Professor of the UrFU Department of Technology of Organic Synthesis and leader of the research team.

According to the scientists, not only the limited solubility of synthesised fluorophores in a water/organic solvent mixture, but also the unique architecture of the nanoparticles formed could be the reason for this strong effect. These include the presence and arrangement of specific functional groups in the structure of the molecules that form the nanoparticles.

The researchers have developed a model for the formation of such nanoparticles in a binary mixture, determined their size (about 100 nanometres), the approximate number of molecules that each of these nanoparticles can contain (about 2×106 molecules), and the energy that excited molecules lose during nanoparticle formation.

"The sensitivity of the fluorophores to a variety of metal ions was the next step in the study.These included both biogenic and toxic metal ions, the detection of which is an important task in environmental monitoring, including water. The synthesised fluorophores showed the ability to selectively detect mercury ions with high sensitivity. The selective detection of only mercury ions is an absolute advantage, as it reduces the probability of error in determining the concentration of this toxic metal in the presence of other metal ions. Another advantage is the possibility of using easy-to-make test strips for the registration of mercury ions. We made such strips from filter paper pre-treated with fluorophore solution," explains Natalya Belskaya.

According to Natalya Belskaya, the described scientific work is a continuation of design, synthesis and research of properties of 2-aryltriazoles and their derivatives with high blue fluorescence carried out at UrFU. In this way, the scientific group of the university, including both experienced scientists and students, Bachelor's and Master's students, created a series of 1,2,3-triazole-4-carboxylic acids and demonstrated the possibility of their application as sensors in the processes of monitoring and controlling the acidity of aqueous solutions.

Further work will involve investigating the potential use of synthesised fluorophores in the design and synthesis of new fluorescent molecular couriers for the study of cellular processes, as well as for the targeted delivery of diagnostic agents or medicines directly to the target - a diseased organ or tissue - in the diagnosis and treatment of socially dangerous diseases such as malignant tumours.

In addition, the synthesized fluorophores may serve as a tool to improve the accuracy of surgical procedures: modern fluorescence surgery has imaging technologies that allow more accurate detection of tumour boundaries and more efficient surgical removal of the affected area of the body.

The research was supported by the Russian Science Foundation (grant № 20-13-00089) and carried out using equipment from the Ural and Siberian Branches of the Russian Academy of Sciences.

Reference

The 1,2,3-triazole nucleus is a common building block in heterocyclic chemistry, used to synthesise agrochemicals, polymers, dyes and pharmaceuticals. In particular, molecules containing the triazole cycle are used in the production of anti-cancer agents and anti-bacterial agents.

The news article was translated by UrFU International Marketing Office. 
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