Magnetism in two dimensions is traditionally considered an exotic phase mediated by spin fluctuations, but far from collinearly ordered in the ground state. Recently, 2D magnetic states have been discovered in layered van der Waals compounds. Their robust and tunable magnetic state by material composition, combined with reduced dimensionality, foresee a strong potential as a key element in magnetic devices. Here, a class of 2D magnets based on metallic chlorides is presented. The magnetic order survives on top of a metallic substrate, even down to the monolayer limit, and can be switched from perpendicular to in-plane by substituting the metal ion from iron to nickel. Using functionalized STM tips as magnetic sensors, local exchange fields are identified, even in the absence of an external magnetic field. Since the compounds are processable by molecular beam epitaxy techniques, they provide a platform with large potential for incorporation into current device technologies.

• Klíčová slova
• 2D material, XMCD, ferromagnetism, nickelocene, transition metal halides, van der waals material,
• Publikační typ
• časopisecké články MeSH

We study the ballistic properties of two-dimensional (2D) materials upon the hypervelocity impacts of C60 fullerene molecules combining ab initio density functional tight binding and finite element simulations. The critical penetration energy of monolayer membranes is determined using graphene and the 2D allotrope of boron nitride as case studies. Furthermore, the energy absorption scaling laws with a variable number of layers and interlayer spacing are investigated, for homogeneous or hybrid configurations (alternated stacking of graphene and boron nitride). At the nanolevel, a synergistic interaction between the layers emerges, not observed at the micro- and macro-scale for graphene armors. This size-scale transition in the impact behavior toward higher dimensional scales is rationalized in terms of scaling of the damaged volume and material strength. An optimal number of layers, between 5 and 10, emerges demonstrating that few-layered 2D material armors possess impact strength even higher than their monolayer counterparts. These results provide fundamental understanding for the design of ultralightweight multilayer armors using enhanced 2D material-based nanocomposites.

• Klíčová slova
• graphene, hexagonal boron nitride, hypervelocity impact, multiscale modeling, nanoarmors,
• Publikační typ
• časopisecké články MeSH

Efficient flexible energy storage systems have received tremendous attention due to their enormous potential applications in self-powering portable electronic devices, including roll-up displays, electronic paper, and "smart" garments outfitted with piezoelectric patches to harvest energy from body movement. Unfortunately, the further development of these technologies faces great challenges due to a lack of ideal electrode materials with the right electrochemical behavior and mechanical properties. MXenes, which exhibit outstanding mechanical properties, hydrophilic surfaces, and high conductivities, have been identified as promising electrode material candidates. In this work, taking 2D transition metal carbides (TMCs) as representatives, we systematically explored several influencing factors, including transition metal species, layer thickness, functional group, and strain on their mechanical properties (e.g., stiffness, flexibility, and strength) and their electrochemical properties (e.g., ionic mobility, equilibrium voltage, and theoretical capacity). Considering potential charge-transfer polarization, we employed a charged electrode model to simulate ionic mobility and found that ionic mobility has a unique dependence on the surface atomic configuration influenced by bond length, valence electron number, functional groups, and strain. Under multiaxial loadings, electrical conductivity, high ionic mobility, low equilibrium voltage with good stability, excellent flexibility, and high theoretical capacity indicate that the bare 2D TMCs have potential to be ideal flexible anode materials, whereas the surface functionalization degrades the transport mobility and increases the equilibrium voltage due to bonding between the nonmetals and Li. These results provide valuable insights for experimental explorations of flexible anode candidates based on 2D TMCs.

• Klíčová slova
• 2D material, DFT, MXene, lithium storage, strain modification,
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

2D oxide nanomaterials constitute a broad range of materials, with a wide array of current and potential applications, particularly in the fields of energy storage and catalysis for sustainable energy production. Despite the many similarities in structure, composition, and synthetic methods and uses, the current literature on layered oxides is diverse and disconnected. A number of reviews can be found in the literature, but they are mostly focused on one of the particular subclasses of 2D oxides. This review attempts to bridge the knowledge gap between individual layered oxide types by summarizing recent developments in all important 2D oxide systems including supported ultrathin oxide films, layered clays and double hydroxides, layered perovskites, and novel 2D-zeolite-based materials. Particular attention is paid to the underlying similarities and differences between the various materials, and the subsequent challenges faced by each research community. The potential of layered oxides toward future applications is critically evaluated, especially in the areas of electrocatalysis and photocatalysis, biomass conversion, and fine chemical synthesis. Attention is also paid to corresponding novel 3D materials that can be obtained via sophisticated engineering of 2D oxides.

• Klíčová slova
• 2D catalysts, 2D zeolites, energy transitions, environmentally friendly catalysis, layered oxides,
• MeSH
• katalýza MeSH
• nanostruktury chemie   MeSH
• oxidy chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• oxidy MeSH

Extrinsic dilute magnetic semiconductors achieve magnetic functionality through tailored interaction between a semiconducting matrix and a non-magnetic dopant. The absence of intrinsic magnetic impurities makes this approach promising to investigate the newly emerging field of 2D dilute magnetic semiconductors. Here the first realization of an extrinsic 2D DMS in Pt-doped WS2 is demonstrated. A bottom-up synthesis approach yields a uniform and highly crystalline monolayer where platinum selectively occupies the tungsten sub-lattice. The orbital overlap between W 4d and Pt 5d results in spin-selective hybrid states that produce a strong valley-Zeeman splitting. Combined experimental and theoretical results show that this interaction yields a sizable ferromagnetic response with a Curie temperature ≈375 K. These results open up a new route toward 2D magnetic properties through tailoring of atomic interactions for future applications in spintronics and magnetic nanoactuation.

• Klíčová slova
• 2D material, dilute, doping process, magnetic, semiconductor,
• Publikační typ
• časopisecké články MeSH

The edges of 2D materials have emerged as promising electrochemical catalyst systems, yet their performance still lags behind that of noble metals. Here, we demonstrate the potential of oriented electric fields (OEFs) to enhance the electrochemical activity of 2D materials edges. By atomically engineering the edge of a fluorographene/graphene/MoS2 heterojunction nanoribbon, strong and localized OEFs were realized as confirmed by simulations and spatially resolved spectroscopy. The observed fringing OEF results in an enhancement of the heterogeneous charge transfer rate between the edge and the electrolyte by 2 orders of magnitude according to impedance spectroscopy. Ab initio calculations indicate a field-induced decrease in the reactant adsorption energy as the origin of this improvement. We apply the OEF-enhanced edge reactivity to hydrogen evolution reactions (HER) and observe a significantly enhanced electrochemical performance, as evidenced by a 30% decrease in Tafel slope and a 3-fold enhanced turnover frequency. Our findings demonstrate the potential of OEFs for tailoring the catalytic properties of 2D material edges toward future complex reactions.

• Klíčová slova
• 2D edges, 2D materials, HER, electrochemistry, oriented electric fields,
• Publikační typ
• časopisecké články MeSH

An in-depth investigation was conducted on a promising composite material (BiVO4/TiO2), focusing on its potential toxicity, photoinduced catalytic properties, as well as its antibiofilm and antimicrobial functionalities. The preparation process involved the synthesis of 2D TiO2 using the lyophilization method, which was subsequently functionalized with sphere-like BiVO4 through wet impregnation. Finally, we developed BiVO4/TiO2 S-scheme heterojunctions which can greatly promote the separation of electron-hole pairs to achieve high photocatalytic performance. The evaluation of concentration- and time-dependent viability inhibition was performed on human lung carcinoma epithelial A549 cells. This assessment included the estimation of glutathione levels and mitochondrial dehydrogenase activity. Significantly, the BiVO4/TiO2 composite demonstrated minimal toxicity towards A549 cells. Impressively, the BiVO4/TiO2 composite exhibited notable photocatalytic performance in the degradation of rhodamine B (k=0.135 min-1) and phenol (k=0.016 min-1). In terms of photoinduced antimicrobial performance, the composite effectively inactivated both gram-negative E. coli and gram-positive E. faecalis bacteria upon 60 minutes of UV-A light exposure, resulting in a significant log 6 (log 10 CFU/mL) reduction in bacterial count. In addition, a 49 % reduction of E. faecalis biofilm was observed. These promising results can be attributed to the unique 2D morphology of TiO2 modified by sphere-like BiVO4, leading to an increased generation of (intracellular) hydroxyl radicals, which plays a crucial role in the treatments of both organic pollutants and bacteria. This research has significant potential for various applications, particularly in addressing environmental contamination and microbial infections.

• Klíčová slova
• 2D TiO2, antibiofilm, antimicrobial, cytotoxicity, photocatalysis, sphere-like BiVO4,
• MeSH
• antibakteriální látky * chemie   farmakologie   MeSH
• biofilmy účinky léků   MeSH
• bismut * chemie   MeSH
• buňky A549 MeSH
• Enterococcus faecalis účinky léků   MeSH
• Escherichia coli * účinky léků   MeSH
• fotochemické procesy * MeSH
• fotolýza MeSH
• katalýza MeSH
• lidé MeSH
• nanostruktury chemie   MeSH
• rhodaminy chemie   MeSH
• titan * chemie   MeSH
• vanadáty * chemie   farmakologie   MeSH
• viabilita buněk účinky léků   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antibakteriální látky * MeSH
• bismut * MeSH
• bismuth vanadium tetraoxide MeSH Prohlížeč
• rhodamine B MeSH Prohlížeč
• rhodaminy MeSH
• titan * MeSH
• titanium dioxide MeSH Prohlížeč
• vanadáty * MeSH

Control over the optical properties of atomically thin two-dimensional (2D) layers, including those of transition metal dichalcogenides (TMDs), is needed for future optoelectronic applications. Here, the near-field coupling between TMDs and graphene/graphite is used to engineer the exciton line shape and charge state. Fano-like asymmetric spectral features are produced in WS2, MoSe2, and WSe2 van der Waals heterostructures combined with graphene, graphite, or jointly with hexagonal boron nitride (h-BN) as supporting or encapsulating layers. Furthermore, trion emission is suppressed in h-BN encapsulated WSe2/graphene with a neutral exciton red shift (44 meV) and binding energy reduction (30 meV). The response of these systems to electron beam and light probes is well-described in terms of 2D optical conductivities of the involved materials. Beyond fundamental insights into the interaction of TMD excitons with structured environments, this study opens an unexplored avenue toward shaping the spectral profile of narrow optical modes for application in nanophotonic devices.

• Klíčová slova
• electron energy-loss spectroscopy, excitons, transition metal dichalcogenides, two-dimensional materials, van der Waals heterostructure,
• Publikační typ
• časopisecké články MeSH

In recent years, two-dimensional (2D) materials have attracted a lot of research interest as they exhibit several fascinating properties. However, outside of 2D materials derived from van der Waals layered bulk materials only a few other such materials are realized, and it remains difficult to confirm their 2D freestanding structure. Despite that, many metals are predicted to exist as 2D systems. In this review, the authors summarize the recent progress made in the synthesis and characterization of these 2D metals, so called metallenes, and their oxide forms, metallene oxides as free standing 2D structures formed in situ through the use of transmission electron microscopy (TEM) and scanning TEM (STEM) to synthesize these materials. Two primary approaches for forming freestanding monoatomic metallic membranes are identified. In the first, graphene pores as a means to suspend the metallene or metallene oxide and in the second, electron-beam sputtering for the selective etching of metal alloys or thick complex initial materials is employed to obtain freestanding single-atom-thick 2D metal. The data show a growing number of 2D metals/metallenes and 2D metal/ metallene oxides having been confirmed and point to a bright future for further discoveries of these 2D materials.

• Klíčová slova
• 2D metals/metallenes, freestanding single-atom-thick membrane, in situ TEM, single-element 2D materials,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

The design and fabrication of active nanomaterials exhibiting multifunctional properties is a must in the so-called global "Fourth Industrial Revolution". In this sense, molecular engineering is a powerful tool to implant original capabilities on a macroscopic scale. Herein, different bioinspired 2D-MXenes have been developed via a versatile and straightforward synthetic approach. As a proof of concept, Ti3C2Tx MXene has been exploited as a highly sensitive transducing platform for the covalent assembly of active biomolecular architectures (i.e., amino acids). All pivotal properties originated from the anchored targets were proved to be successfully transferred to the resulting bioinspired 2D-MXenes. Appealing applications have been devised for these 2D-MXene prototypes showing (i) chiroptical activity, (ii) fluorescence capabilities, (iii) supramolecular π-π interactions, and (iv) stimuli-responsive molecular switchability. Overall, this work demonstrates the fabrication of programmable 2D-MXenes, taking advantage of the inherent characteristics of the implanted (bio)molecular components. Thus, the current bottleneck in the field of 2D-MXenes can be overcome after the significant findings reported here.

• Klíčová slova
• 2D materials, chiral MXene, electronic devices, fluorescence, molecular switches, supramolecular recognition, surface engineering,
• MeSH
• nanostruktury * MeSH
• titan * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• titan * MeSH