Chemists have developed zinc nanosheets for water purification systems.

The results of the research, funded by a grant from the Russian Science Foundation, have been published in the high-ranking scientific journal of the first quartile Ceramics International.

Organic compounds—such as dyes and antibiotics—are classified as toxic, which is why they must be properly disposed of in household applications to minimize harmful effects on the environment. There are currently specialized services and conditions for this purpose, but they are not accessible to everyone, leading to regular discharge of harmful substances into sewage systems from industrial wastewater and livestock farms.

As explained by Olga Osmolovskaya, head of the synthesis and research group for nanoparticles and nanostructured materials at St. Petersburg State University (SPbGU), and associate professor in the Department of General and Inorganic Chemistry, the most promising modern method for combating water pollution is photocatalysis. This process involves semiconductor particles breaking down pollutant molecules through a chemical reaction under the influence of light.

However, to develop an effective photocatalyst, it is essential to understand the specifics of its operation. For this purpose, chemists from St. Petersburg University synthesized a series of nanoparticles using the chemical precipitation method, then studied the properties of the resulting materials to comprehend the true mechanism of their action, which is necessary for the application of these particles.

Scientists are well aware that the properties of nanoparticles are highly dependent on their size and shape. In this case, these are flakes approximately 20 nanometers thick, hence they are referred to as nanosheets. During the research, chemists tested an approach that involved not only varying the synthesis conditions—key factors influencing the outcome—but also introducing substances that provide counterions into the reaction medium, which are meant to arrange the nascent crystals in a specific order. This ultimately led to the production of particles in the form of nanosheets.

“To visualize the results, one can imagine a typical leaf. It has a large surface where droplets of dew form, and it is on this surface that contact with pollutants and their breakdown occurs. However, such a leaf also has thickness and a thin lateral surface, the role of which should not be underestimated. We demonstrated that this is precisely what in nanosheets is responsible for the formation of radicals—special forms of water molecules and dissolved oxygen that destroy harmful molecules,” said Ksenia Meshina, a research assistant in the Department of General and Inorganic Chemistry at SPbGU and one of the study's authors.

A distinctive feature of the work, as explained by another author, Mikhail Voznesensky, associate professor in the Department of Physical Chemistry at SPbGU, is the conduction of quantum-chemical calculations. Such detail allows for accounting defects in the crystalline structure of nanoparticles and using the obtained data to understand the processes of adsorption and photocatalysis.

Thus, the approaches developed by the scientific group of chemists at St. Petersburg University enable the explanation of the photocatalyst's effectiveness for each specific pollutant. Another advantage of this approach is that the zinc oxide used by the authors is non-toxic and possesses antibacterial properties, meaning that materials made from it are environmentally friendly and biocompatible.

“Experiments on the decomposition of dyes using light and computational chemistry methods have helped create a material that purifies water from specific contaminants by more than 90 percent. It is important to understand that there is no universal photocatalyst suitable for all cases: what works for one substance may not be effective for another. Therefore, precise parameter selection of the photocatalyst is necessary for effective water purification from a given pollutant. The results of our work allow for this to be done significantly faster, reducing the number of experiments through computational calculations,” noted Mikhail Osmolovsky, associate professor in the Department of General and Inorganic Chemistry at SPbGU.

Previously, scientists from this research group developed an approach for synthesizing magnetite nanoparticles coated with a zinc oxide shell.