Scientists of LDMS and SRC IN proposed a promising sorbent for wastewater treatment from antibiotics

The article was published in Nanomaterials.

As a result of the constant increase in the use of drugs, the accumulation of antibiotics and their breakdown products in wastewater has become a serious problem for humans and the environment. Most often, antibiotics enter rivers and groundwater as waste from pharmaceutical companies, medical and pharmacy facilities, and agriculture. The presence of antibiotics in water leads to the growth of bacteria and microorganisms resistance to them, the development of allergic reactions, and even the multiplication of dangerous bacteria.

Currently, there are various methods of wastewater treatment. However, each method has its own limitations. One of the simplest and inexpensive methods of purification, which do not require complex production structures or additional chemical reactions is sorption. This is what the researchers at the Laboratory of Digital Materials Science and the Scientific Research Center "Inorganic Nanomaterials" have focused on. There is no need to create special expensive equipment or artificially introduce additional chemical or biologically active components that can disturb the ecological balance. It is enough just to pass contaminated water through a filter or suspension of boron nitride nanoparticles.

The sorbent created by the researchers based on hexagonal boron nitride is able to effectively clean antibiotic wastewater. Researchers chose three types of antibiotics, which are among the most common pollutants: ciprofloxacin, tetracycline and bicillin.

In the future, scientists are planning to increase the sorption capacity of nanoparticles by applying a polymer or metal ion deposition, as well as to expand the range of antibiotics studied.

Feature of the endohedral metallofullerene Y@C82 and Gd@C82 polymerization under high pressure

The paper was published in J. Phys. Chem. C (2022).

Fullerenes have attracted the attention of researchers since their discovery and further development of large-scale production. The unique symmetric structure, attractive physical and chemical properties make fullerenes promising for many fields of science and technology. An attractive feature of fullerenes is the possibility of tuning and modifying their structure in various ways. The accessibility of the outer surface allows functionalization, while the vast cavity inside the molecule can be used for introducing various guest atoms that can significantly change the physicochemical properties of the fullerene without essential structural distortion. For example, the endohedral metal atoms may lead to the appearance of magnetic moments in fullerenes and further apply them in quantum electronics and medicine. It is extremely interesting to study the physicochemical properties of endohedral metallofullerene (EMF), including their behavior under pressure. However, so far the lack of methods for their large-scale synthesis has not allowed such experimental studies.

The situation has changed since we developed a method for the synthesis of fullerene endohedral complexes in macroscopic quantities. In our recent work, we showed that introduction of Sc2C2 cluster inside a fullerene cavity significantly changes its behavior under pressure. To clarify the influence of metal ions on the polymerization behavior of fullerenes, it is important to investigate the behavior of EMF with only single guest metal ion inside, which would allow to exclude the anisotropic effects associated with the low symmetry of the Sc2C2 complex.

Here we present the first study of the properties under high pressures of the gadolinium and yttrium endohedral metallofullerenes as bulk material. The polymerization processes of both complexes were studied theoretically and experimentally. It was shown that the presence of the metal ions significantly affects the polymerization of endohedral complexes which are studied at high pressures up to 40 GPa. It was found that the process of polymerization of both classes of endohedral complexes is similar to each other but differs from the pure fullerene polymerization. DFT simulation results demonstrated that both metal ions dramatically change the fullerene bonding process by the polarization of the carbon bonds which leads to their increased chemical activity. The values of the bulk modulus were calculated for the resulting polymerized materials using the Raman measurements at a pressure range of 3-27 GPa. The moduli were equal to ~340 GPa for gadolinium and yttrium endohedral complexes which is lower than the B value of diamond (443 GPa) but comparable with Sc2C2@C82 (330 GPa).

Edges in bilayered h-BN. Insights into atomic structure

The paper was published in Nanoscale (2022).

The surface has always been of particular interest because of its wide variability in structure and unexpected properties. On the other hand, “surface of surface” – an edge of a nanostructure might become important and bring new phenomena. The precise fabrication of edges on 2D materials at a certain crystallographic orientation is challenging and requires precise knowledge about edge chemistry. In some cases, edge displays very specific structure. For example, multilayered graphene edges tend to connect with each other. The case of bilayered graphene was investigated in detail and it was shown that the connection of the edges even does not require the overcoming of any barrier and, therefore, hollow sp2-hybridized graphene structure forms spontaneously. In our previous work was shown that the structure of the graphene closed edges is precisely defined and can be represented as the grain boundary between two graphene domains generally misoriented.

The understanding of the edge structure is important also for the case formation of holes in the 2D structure because this is an attractive object for tuning the material properties. For the single-layer graphene, many studies have explored holes for DNA sequencing, gas sensing, ion and molecules sieve, (in particular water desalination), molecular transport and others. Several comparable studies also have been done with hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2). The variety of hole shapes and the type of passivation of their edges does not allow systematic experimental studies to be carried out. Usually, studies focus on performance tests without the information of edge configuration and chemical stability which may affect to the performance significantly.

The carbon counterpart, boron nitride is less investigated in such a case, although it seems promising to create holes not in bigraphene, but specifically in bilayered h-BN. Indeed, the strong tendency of the layers to be AA’ stacked allows one to be confident that the bilayered structure will be predetermined. However, it remains completely unclear which edges of the bilayered h-BN will tend to close and what the final structure will be. The structure of the edges of multilayered h-BN is usually unknown whereas from general logic the similar effect of self-passivation can be expected due to the close values of flexural rigidity and edge energy.

The presented paper is devoted to the study of the edges of bilayered h-BN. It is shown that the edges tend to connect regardless of the edge cut. A defectless connection can be expected only in the case of a zigzag edge, while in other cases a series of tetragonal, and octagonal defects will be formed. This result was obtained by carrying out an analogy between the edge of bilayered h-BN and the interface of monolayer h-BN (see the Figure). Information on the structure and energetics of closed edges allowed us to predict the shape of holes in h-BN, which agreed with the reference experimental data. Finally, it is shown that the closed edges do not create states in the band gap, thus not changing the dielectricity of h-BN.

a) The top view of bilayered h-BN with closed edge. θ is the boundary inclination with respect to armchair direction. b) The scheme illustrates how a bilayered h-BN with a closed edge can be unfolded into a flat structure. c) Flat layer h-BN with a grain boundary obtained from a bilayer with a connected edge shown in (a).