Recent discoveries in two-dimensional magnetism have intensified the investigation of van der Waals magnetic materials and further improved our ability to tune their magnetic properties. Tunable magnetism has been widely studied in antiferromagnetic metal thiophosphates $M\mathrm{P}{X}_3$. Substitution of metal ions $M$ has been adopted as an important technique to engineer the magnetism in $M\mathrm{P}{X}_3$. In this work, we have studied the previously unexplored chalcogen $X$ substitutions in $M\mathrm{P}{X}_3$ ($M=\mathrm{Mn}$/Ni; $X=\mathrm{S}$/Se). We synthesized the single crystals of $\mathrm{MnP}{\mathrm{S}}_{3-x}{\mathrm{Se}}_x$ $\left(0\le x\le 3\right)$ and $\mathrm{NiP}{\mathrm{S}}_{3-x}{\mathrm{Se}}_x$ $\left(0\le x\le 1.3\right)$ and investigated the systematic evolution of the magnetism with varying $x$. Our study reveals the effective tuning of magnetic interactions and anisotropies in both ${\mathrm{MnPS}}_3$ and ${\mathrm{NiPS}}_3$ upon Se substitution. Such efficient engineering of the magnetism provides a suitable platform to understand the low-dimensional magnetism and develop future magnetic devices.

Despite intensive research on the application of two-dimensional (2D) materials, including MXenes, in nanomedicine, the knowledge concerning the mechanisms responsible for their observed bio-effects is far from being understood. Here we present insight into the mechanism of toxicity in vitro of the 2D Ti₃C₂ MXene. The most important results of this work are that using simple, inexpensive, post-delamination treatments, such as ultrasonication or mild thermal oxidation it is possible to ‘tune’ the cytotoxicity of the Ti₃C₂T _z flakes. Sonication of Ti₃C₂T _z flakes, or sonication followed by mild oxidation in the water at 60 °C, renders them selectively toxic to cancer cells as compared to non-malignant ones. It relates to the appearance of superficial titanium (III) oxide (Ti₂O₃) layer corresponding to the type of post-treatment. The presence of surface-Ti₂O₃ results in a noticeably higher generation of oxidative stress compared to pristine 2D Ti₃C₂. Our findings give evidence that the sonication and thermal treatments were successful in changing the nature of the surface terminations on the Ti₃C₂T _z surfaces. This study makes a significant contribution to the future rationalized surface-management of 2D Ti₃C₂ MXene as well as encourages new rationalized applications in biotechnology and nanomedicine. Bullet points: 1. First study on 2D Ti₃C₂ MXene superficially oxidized to titanium (III) oxide i.e. Ti₂O₃. 2. By sonication Ti₃C₂Tz MXene flakes followed by mild thermal oxidation in the water at 60 °C for 24 h, it is possible to ‘tune’ the toxicity of the flakes to cancerous cell lines. 3. Decreases in cell viabilities were dose-dependent. 4. Highest cytotoxic effect was observed for thermally oxidized samples. 5. The thermally oxidized samples were also selectively toxic towards all cancerous cell lines up to 375 mg l⁻¹. 6. Reactive oxygen species generation was identified as a mechanism of toxicity.

Background: The biological activity of MXenes has been studied for several years because of their potential biomedical applications; however, investigations have so far been limited to 2D titanium carbides. Although monolayered Ti₂NT_x MXene has been expected to have biological activity, experimental studies revealed significant difficulties due to obstacles to its synthesis, its low stability and its susceptibility to oxidation and decomposition. Results: In this paper, we report our theoretical calculations showing the higher likelihood of forming multilayered Ti₂NT_x structures during the preparation process in comparison to single-layered structures. As a result of our experimental work, we successfully synthesized multilayered Ti₂NT_x MXene that was suitable for biological studies by the etching of the Ti₂AlN MAX phase and further delamination. The biocompatibility of Ti₂NT_x MXene was evaluated in vitro towards human skin malignant melanoma cells, human immortalized keratinocytes, human breast cancer cells, and normal human mammary epithelial cells. Additionally, the potential mode of action of 2D Ti₂NT_x was investigated using reactive oxygen tests as well as SEM observations. Our results indicated that multilayered 2D sheets of Ti₂NT_x showed higher toxicity towards cancerous cell lines in comparison to normal ones. The decrease in cell viabilities was dose-dependent. The generation of reactive oxygen species as well as the internalization of the 2D sheets play a decisive role in the mechanisms of toxicity. Conclusions: We have shown that 2D Ti₂NT_x in the form of multilayered nanoflakes exhibits fair stability and can be used for in vitro studies. These results show promise for its future applications in biotechnology and nanomedicine.

We present a systematic study of the electronic and magnetic properties of two-dimensional ordered alloys, consisting of two representative hosts (MnPS₃ and NiPS₃) of transition metal phosphorus trichalcogenides doped with 3d elements. For both hosts, our DFT + U calculations are able to qualitatively reproduce the ratios and signs of all experimentally observed magnetic couplings. The relative strength of all antiferromagnetic exchange couplings, both in MnPS₃ and in NiPS₃, can successfully be explained using an effective direct exchange model: it reveals that the third-neighbor exchange dominates in NiPS₃ due to the filling of the t_2g subshell, whereas for MnPS₃, the first-neighbor exchange prevails, owing to the presence of the t_2g magnetism. On the other hand, the nearest neighbor ferromagnetic coupling in NiPS₃ can only be explained using a more complex superexchange model and is (also) largely triggered by the absence of the t_2g magnetism. For the doped systems, the DFT + U calculations revealed that magnetic impurities do not affect the magnetic ordering observed in the pure phases, and thus, in general in these systems, ferromagnetism may not be easily induced by such a kind of elemental doping. However, unlike for the hosts, the first and second (dopant–host) exchange couplings are of similar order of magnitude. This leads to frustration in the case of antiferromagnetic coupling and may be one of the reasons of the observed lower magnetic ordering temperature of the doped systems.