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Silicene has recently been revisited as a 2D material with potential thermoelectric applications. Here, the thermal properties of supported silicene are determined by optothermal Raman spectroscopy. Single and multilayer silicene is grown either directly on silver (Ag) substrates or on an intermediate tin (Sn) monolayer, introduced to reduce the influence of the substrate on the physical properties of silicene. Experimental values of an effective cross‐plane thermal conductivity of 0.5 W/mK are obtained for silicene on Ag and 0.3 W/mK for silicene on stanene‐Ag. The values of the interfacial thermal conductance, on the other hand, are 0.3 and 0.5 GW/m2K, respectively. Heterostack engineering is confirmed as a versatile strategy for extracting relevant physical parameters in silicene and for modulating the thermal response in the 2D limit. [ABSTRACT FROM AUTHOR]

Hydrogen is rapidly emerging as a clean and versatile energy carrier addressing challenges of climate change and energy sustainability. With increasing energy demand and rising application of hydrogen energy, safety while harnessing hydrogen energy is a primary concern. To enhance safety, it is critical to detect hydrogen gas during its leakage which is otherwise challenging due to its colourless, odourless and inflammable nature. Hence, there is an urgent need for the development of hydrogen sensors for rapid response, maximum absorption/desorption, high selectivity, a wide dynamic range, and a low detection limit. This review provides a comprehensive analysis of emerging nanomaterials and their composites spanning from 0D to 3D for hydrogen sensing, emphasizing the underlying mechanisms. It also deliberates on the advantages and disadvantages of a wider range of advanced materials including noble metals, metal oxide semiconductors (MOS), transition metal dichalcogenides (TMD), metal organic frameworks (MOF), Xenes and MXenes pondering over hysteresis phenomenon, commonly observed as a limitation of noble metal-based hydrogen sensors. Among these emerging materials, two dimensional nanomaterials stand out as the optimal choice for hydrogen sensing due to their large surface area, exceptional electrical properties, low operating temperatures, and ease of chemical modification. Carbon-based materials, TMDs, MOFs, and MXenes have higher gas absorption capability and excellent mechanical properties, making them suitable for low/room temperature sensing and wearable sensing platforms. The review underscores the need for reliable sensing materials and presents challenges in quantitative detection of hydrogen offering future directions for research in this field. [Display omitted] • The review features the urge to develop hydrogen sensors. • It spans a wide range of new materials used for hydrogen sensing over the last two decades. • The mechanism of hydrogen adsorption & desorption is elaborated. • The article highlights challenges & prospects of materials for hydrogen sensing. • This article is useful to researchers, scientists, and engineers working in this field. [ABSTRACT FROM AUTHOR]

Wet‐chemical synthesis refers to the bottom‐up chemical synthesis in solution, which is among the most popular synthetic approaches towards functional two‐dimensional (2D) materials. It offers several advantages, including cost‐effectiveness, high yields,, precious control over the production process. As an emerging family of 2D materials, elemental 2D materials (Xenes) have shown great potential in various applications such as electronics, catalysts, biochemistry,, sensing technologies due to their exceptional/exotic properties such as large surface area, tunable band gap,, high carrier mobility. In this review, we provide a comprehensive overview of the current state‐of‐the‐art in wet‐chemical synthesis of Xenes including tellurene, bismuthene, antimonene, phosphorene,, arsenene. The current solvent compositions, process parameters utilized in wet‐chemical synthesis, their effects on the thickness, stability of the resulting Xenes are also presented. Key factors considered involves ligands, precursors, surfactants, reaction time, temperature. Finally, we highlight recent advances, existing challenges in the current application of wet‐chemical synthesis for Xenes production, provide perspectives on future improvement. [ABSTRACT FROM AUTHOR]

Heterostructures offer an exceptional possibility of combining individual 2D materials into a new material having altered properties compared to the parent materials. Germanane (GeH) is a 2D material with many favorable properties for energy storage and catalysis, however, its performance is hindered by its low electrical conductivity. To address the low electrochemical performance of GeH, a heterostructure of GeH and Ti3C2Tx is fabricated. The Ti3C2TX is a layered material belonging to the family of MXenes. The resulting heterostructure (GeMXene) at a defined mass ratio of GeH and Ti3C2Tx shows superior capacitive performance that surpasses that of both pristine materials. The effect of the size of cations and anions for intercalation into GeMXene in different aqueous salt solutions is studied. GeMXene allows only cation intercalation, which is evidenced by the gravimetric electrochemical quartz crystal microbalance (EQCM) technique. The capacitive performance of the GeMXene is compared in neutral, acidic, and alkaline electrolytes to determine the best electrochemical performance. This unleashes the potential use of GeMXene heterostructure in different electrolytes for supercapacitors and batteries. This work will pave the way to explore the heterostructures of other 2D materials such as novel MXenes and functionalized germanane for highly energy‐storage efficient systems, and beyond. [ABSTRACT FROM AUTHOR]

2D materials exhibit a variety of characteristics that make them appealing platforms for cancer treatment such as high drug loading capacity and photothermal and photodynamic properties. A key advantage of 2D material platforms for oncological applications is the ability to harness multiple modalities including drug delivery, photothermal therapy, photodynamic therapy, chemodynamic therapy, gene delivery, and immunotherapy approaches for improved efficacy. In this review, a comparison of the unique properties of different classes of 2D materials that enable their usage as platforms for multimodal therapy is provided. Further, the benefits and drawbacks of different platforms are also highlighted. Finally, current challenges and emerging opportunities for future development of 2D materials to further enable combination therapy and translation from the bench to clinical oncology applications are discussed. [ABSTRACT FROM AUTHOR]

To support sustainability, advanced, affordable, and applicable systems of desired and controlled performance are needed for efficient biomedical, environmental, energy, and agricultural applications. In this direction, two-dimensional materials (2D) can be the best choice to explore because of a better understanding and control of their systems and properties. A number of excellent reviews demonstrating the role of graphene-based nanomaterials for biomedical applications are reported in the literature. However, beyond graphene, emerging 2D materials are not yet well explored to employ them to achieve next-generation biomedical application systems. To cover these gaps, this comprehensive review carefully and critically discusses the 2D materials beyond graphene which includes transition metal dichalcogenides (TMDs), transition metal oxides (TMOs), Xenes, MXenes, and metal organic framework (MOF) for biomedical applications. These 2D materials have been widely employed for biomedical and healthcare applications, including drug delivery, cancer therapy, tissue engineering, biosensing etc., and are continuously supporting other scientific fields but their better understanding in terms of controlling shape, size, and properties (optical, electrical, magnetic, and molecular) is still the focus of state-of-the-art research, and focus of this review. Many researchers have nicely discussed the methods of synthesis, characterization, categorization, and of course the diverse applications of different 2D materials in their articles; however, the literature still lacks a complete and collective work emphasizing on extensive analysis of some emerging 2D materials such as TMDs, TMOs, MXenes, Xenes, and MOFs in biomedical contexts. Keeping this is mind, this review is a modest attempt to summarize, and illustrate the role and applications of 2D materials in this field. The outcomes will serve as key findings that should be known to the scholars who are planning to explore and research in the field of 2D materials for advanced applications with high and adaptable performance.

Currently, numerous monoelemental two-dimensional (2D) materials, called Xenes, have been discovered, including graphyne (GD), silicene, germanene, arsenene, and borophene. Their structures, fabrication methods, as well as properties have been extensively explored. Based on their single-element composition, high optical response capability, excellent electrical-optical properties, large specific surface area (SSA) and easy modification, Xenes have been widely used in photoelectric applications (detection, modulation, light processing) and biomedicine (biological sensing, drug loading, bioimaging, etc.). Especially in the field of biomedicine, Xenes are expected to induce a great breakthrough. In this review, we introduce the structural characteristics, synthesis and modification methods of several common Xenes respectively. The general properties including optical, electronic, physical and chemical properties of Xenes are summarized. Their diverse utilization as biosensors for nucleic acid sequencing, bioactive detection, and cancer diagnosis, etc. are also explicitly explored. Finally, the challenges and future perspectives of Xenes in biosensor are discussed. [ABSTRACT FROM AUTHOR]

Germanene, as an artificial graphene-like near room temperature topological insulator, compatible with ubiquitous silicon technology, is potentially the most promising artificial Xene for ultra-scale nanoelectronics. Here, we follow its emergence and development when prepared in situ under ultra-high vacuum in clean and controlled conditions by dry epitaxy on prominent metal surfaces (e.g., aluminum, silver, gold). We describe its predicted electronic properties and its birth in 2014, even if it was just a renaissance, as it was only understood after 51 years after an undeciphered birth certificate lost in oblivion. We emphasize the lifting of germanene flakes from an aluminum template with the tip of a scanning tunneling microscope, and their repositioning to form bilayer germanene with Bernal stacking. Finally, we discuss the growth of monolayer germanene in a single phase harboring Dirac fermions, following a bottom-up synthesis strategy by segregation on a gold thin film in epitaxy on a germanium support. [ABSTRACT FROM AUTHOR]

The quantum effects confined in the ultimate two-dimensional limit are able to address the challenges and provide advances in high-performance spintronic devices. In the paper we show a successful strategy to enrich the electronic properties of thallene, a new honeycomb analogue of graphene, through the interface engineering, which opens a great potential of thallene as an advanced spintronics material. While the thallene has been experimentally realized recently on NiSi2/Si(111) substrate, there remains a lack of attractive electronic properties due to the strong thallene-substrate coupling. This challenge is addressed here through the decoration of thallene/NiSi2 interface by Sn interlayer, which allows to eliminate the thallene-substrate coupling and produce a high-quality large-scale thallene monolayer with exotic electron bands demonstrating colossal spin-polarization just above the Fermi level. It is demonstrated that appropriate electron doping or external electric field are enable the spin-transport regime. The discovered band structure regulation boosts the functionality of the 2D-Tl Xene and makes it a highly attractive material for spintronics applications.

Driven by new two-dimensional materials, great changes and progress have taken place in the field of ultrafast photonics in recent years. Among them, the emerging single element two-dimensional materials (Xenes) have also received much attention due to their special physical and photoelectric properties including tunable broadband nonlinear saturable absorption, ultrafast carrier recovery rate, and ultrashort recovery time. In this review, the preparation methods of Xenes and various integration strategies are detailedly introduced at first. Then, we summarize the outcomes achieved by Xenes-based (beyond graphene) fiber lasers and make classifications based on the characteristics of output pulses according to the materials characterization and nonlinear optical absorption properties. Finally, an outlook of the future opportunities and challenges of ultrafast photonics devices based on Xenes and other 2D materials are highlighted, and we hope this review will promote their extensive applications in ultrafast photonics technology.

In the realm of two-dimensional (2D) materials, besides the ones initially peeled from lamellar crystals, the artificial emerging elemental ones, called Xenes, appear as strong contenders to graphene in a booming new field. The very first synthetic Xene was silicene, created in 2012. On the occasion of its tenth anniversary, this concise review, describes the birth of silicene, in situ, under ultra-high vacuum, and surveys its most tantalizing properties: its Dirac features, its 2D topological insulator character, its easy functionalization, its insertion as atom-thin channel in Field Effect Transistors operating at room temperature. Silicene has striking variants and amazing doubles in the quantum world; these lookalikes are briefly described and their origins discussed. We owe to silicene the legacy of all its descendants from borophene to tellurene, and fascinating prospects for spintronics, the emergence and control of Majorana fermions, possibly for quantum computing.

Xenes, mono-elemental atomic sheets, exhibit Dirac/Dirac-like quantum behavior. When interfaced with other 2D materials such as boron nitride, transition metal dichalcogenides, and metal carbides/nitrides/carbonitrides, it enables them with unique physicochemical properties, including structural stability, desirable bandgap, efficient charge carrier injection, flexibility/breaking stress, thermal conductivity, chemical reactivity, catalytic efficiency, molecular adsorption, and wettability. For example, BN acts as an anti-oxidative shield, MoS 2 injects electrons upon laser excitation, and MXene provides mechanical flexibility. Beyond precise compositional modulations, stacking sequences, and inter-layer coupling controlled by parameters, achieving scalability and reproducibility in hybridization is crucial for implementing these quantum materials in consumer applications. However, realizing the full potential of these hybrid materials faces challenges such as air gaps, uneven interfaces, and the formation of defects and functional groups. Advanced synthesis techniques, a deep understanding of quantum behaviors, precise control over interfacial interactions, and awareness of cross-correlations among these factors are essential. Xene-based hybrids show immense promise for groundbreaking applications in quantum computing, flexible electronics, energy storage, and catalysis. In this timely perspective, recent discoveries of novel Xenes and their hybrids are highlighted, emphasizing correlations among synthetic parameters, structure, properties, and applications. It is anticipated that these insights will revolutionize diverse industries and technologies., (© 2024 Wiley‐VCH GmbH.)

To meet the escalated global energy requirements while preserving the intrinsic environmental integrity, it is highly important to develop renewable and clean energy sources as the replacement of traditional fossil fuels. Hydrogen is an appealing green energy source due to huge energy density, carbon free by products, renewable and storable nature. Water splitting is an exceedingly important technology for sustainable hydrogen generation. However, the process needs high-performance, stable, and low-cost catalyst for efficient hydrogen evolution reaction (HER). This review article aims to summarize the theoretical understanding of foundations for various H 2 development technologies along with their merits and de-merits. The essence of nanosciences for the development of nanoengineered stable and cost-effective catalysts has been comprehensively showcased by enlightening the outstanding performance of newly emergent nanocatalyst for H 2 production via water splitting. Particular consideration has been devoted to prevalent approaches that can improve the catalytic properties of the categorized nanocatalyst and provide insight towards atomic assembly related mechanism. Future consideration for catalytic enhancement is also discussed. In short, this critical review comes up with the insight essence of hybridized catalyst that are noteworthy for researchers and industrialists to sort out the best class of materials in accordance with hydrogen production techniques. [Display omitted] • Underlying mechanisms for Hydrogen production via existing water splitting techniques have been summarized. • Describes the fundamental insight of material requirements as water splitting catalyst. • Unveils the pros and cons of traditional Nanocatalyst. • Introduce features of emerging MXenes, Nano Encapsulated, Nanocurved, Janus Nanoparticles, and Single Atomic Catalyst. • The new pathways are highlighted to overcome the most encountered challenges in water splitting hydrogen generation. [ABSTRACT FROM AUTHOR]

With black phosphorus being a promising two-dimensional layered semiconductor for application to electronics and optoelectronics, an issue remains as to how heat diffusion is managed when black phosphorus is interfaced with metals, namely in a typical device heterojunction. We use Raman spectroscopy to investigate how the laser-induced heat affects the phonon modes at the interface by comparing the experimental data with a finite element simulation based on a localized heat diffusion. The best convergence is found taking into account an effective interface thermal conductance, thus indicating that heat dissipation at the Au-supported black phosphorus nanosheets is limited by interface effect. [ABSTRACT FROM AUTHOR]

Abstract Emerging Xenes, mostly group IVA and VA elemental two‐dimensional (2D) materials, have small and tunable band gaps between graphene and transition metal dichalcogenides, giving versatile electrical properties. While their microelectronic or optoelectronic properties are being extensively explored, there remains a lack of study on Xenes' uniquely advantageous thermoelectric performance. This review highlights state‐of‐the‐art experimental and theoretical progress in the thermoelectric effect and devices of IVA and VA Xenes. Vertically displaced, a.k.a. “buckled” or “puckered,” atomic arrays result in exotic and tunable electrical or thermal transport behaviors. Different from chemical doping strategies usually employed in bulk thermoelectric materials, 2D Xenes can be tuned by physical means, such as atomic layer control and quantum confinement effects. A precise and compatible platform for 2D thermoelectric effect and devices study is available via the engagement between micro/nanofabrication of 2D Xene transistors and thermal property measurement techniques. This review also reveals potential thermoelectric applications of Xenes and their compounds (Bi2Te3, Bi2Se3, etc.), such as accurate stretchable temperature sensors, fast terahertz photodetectors, and so on.

Among ultrathin monoelemental two-dimensional (2D) materials, bismuthene, the single layer of heavier group-VÎ' element bismuth (Bi), has been predicted to have large non trivial gap. Here, we demonstrate the growth of Bi films by molecular beam epitaxy on 2D-HfTe2 template. At the initial stage of Bi deposition (1â€"2 bilayers, BL), both the pseudocubic Bi(110) and the hexagonal Bi(111) phases are formed. When reaching 3 BL Bi, a transformation to pure hexagonal Bi(111) occurs. The electronic band structure of 3 BL Bi(111) films was measured by angle-resolved photoemission spectroscopy showing very good matching with the density functional theory band structure calculations of 3 BL free standing Bi(111). The grown Bi(111) thin film was capped with a protective Al2O3 layer and its stability under ambient conditions, necessary for practical applications and device fabrication, was confirmed by x-ray photoelectron spectroscopy and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) mono-elemental materials (Xenes) show remarkable potential in the fields of fundamental science and technology, have been regarded as a wide range of building blocks for electronic technologies due to their unique chemical, physical, electrical, and optical properties. Here, 2D tellurene/black phosphorus (Te/BP) heterojunctions are successfully fabricated through liquid-phase exfoliation (LPE) method. Their nonlinear optical absorption properties at 1.0, 2.0, and 2.8 μm have been studied by an open-aperture Z-scan method. The results revealed the excellent broadband saturable absorption responses of the prepared BP/Te heterojunctions, which are further confirmed by using them as saturable absorbers (SAs) for passively Q-switched all-solid-state lasers operating at 1.0, 2.0, and 2.8 μm, respectively. In particular, 1.04 μm continuous-wave (CW) mode-locked lasers with a pulse width of 404 fs is realized for the first time, to our best knowledge. Our work indicates that 2D Xenes especially 2D Xenes based heterojunctions have great potential in the fields of pulsed laser generation/modulation and other optoelectronic and photonic devices.

Germanene, as an artificial graphene-like near room temperature topological insulator, compatible with ubiquitous silicon technology, is potentially the most promising artificial Xene for ultra-scale nanoelectronics. Here, we follow its emergence and development when prepared in situ under ultra-high vacuum in clean and controlled conditions by dry epitaxy on prominent metal surfaces (e.g., aluminum, silver, gold). We describe its predicted electronic properties and its birth in 2014, even if it was just a renaissance, as it was only understood after 51 years after an undeciphered birth certificate lost in oblivion. We emphasize the lifting of germanene flakes from an aluminum template with the tip of a scanning tunneling microscope, and their repositioning to form bilayer germanene with Bernal stacking. Finally, we discuss the growth of monolayer germanene in a single phase harboring Dirac fermions, following a bottom-up synthesis strategy by segregation on a gold thin film in epitaxy on a germanium support.

Two-dimensional (2D) materials like transition metal dichalcogenides and Xenes are expected to bring exciting advancements in many fields of nanotechnology. The wealth of their electronic properties makes them appealing for a broad range of applications. In particular, in the framework of optics and photonics, three emerging routes where the key role of 2D materials will push forward the current state-of-the-art will be here outlined and discussed. Exerting control over the light-driven generation of spin-polarized dissipationless currents, enhancing the photon harvesting, and engineering the light-matter interaction are three challenges for 2D materials-based optics and photonics.

The urgent quest to introduce the Xenes, a new family of graphene‐like materials, into everyday technological devices furthers demands for a specific understanding of their reactivity to different environments. Herein, the role of oxygen on blue phosphorene fragments alloyed with the Au(111) substrate, the so‐called BlueP–Au alloy, is investigated both on a microscopic scale and at the interface with Al2O3, commonly used to protect Xenes in ambient conditions. Although molecular oxygen does not affect the BlueP–Au alloy or intercalate below it, the role of oxygen is fundamental to relieve the charging effects at the very interface between Al2O3 and the BlueP–Au alloy when exposed to air. These findings highlight the importance of combining different tools, including microscopy and spectroscopy, to ascertain the stability of 2D materials in device‐ready configurations. [ABSTRACT FROM AUTHOR]

The synthesis of new Xenes and their potential applications prototypes have achieved significant milestones so far. However, to date the realization of Xene heterostructures in analogy with the well known van der Waals heterostructures remains an unresolved issue. Here, a Xene heterostructure concept based on the epitaxial combination of silicene and stanene on Ag(111) is introduced, and how one Xene layer enables another Xene layer of a different nature to grow on top is demonstrated. Single‐phase (4 × 4) silicene is synthesized using stanene as a template, and stanene is grown on top of silicene on the other way around. In both heterostructures, in situ and ex situ probes confirm layer‐by‐layer growth without intercalations and intermixing. Modeling via density functional theory shows that the atomic layers in the heterostructures are strongly interacting, and hexagonal symmetry conservation in each individual layer is sequence selective. The results provide a substantial step toward currently missing Xene heterostructures and may inspire new paths for atomic‐scale materials engineering. [ABSTRACT FROM AUTHOR]

Stanene is one of the most intriguing two-dimensional (2D) materials because of its nontrivial topological properties. Here, the optical properties from THz to UV of molecular beam deposited tin nanosheets on Al2O3(0001) are reported. The experimental absorption coefficient cannot be described in terms of metallic tin or tin oxides. Nonetheless, a similar optical behavior was predicted by theory for freestanding stanene, thus suggesting the formation of the 2D tin nanosheets with stanene-like properties. These findings show that 2D tin bears appealing optical properties in a broad range of the electromagnetic spectrum, thus paving the way to Xenes-based nanophotonics. [ABSTRACT FROM AUTHOR]

Emerging Xenes, mostly group IVA and VA elemental two‐dimensional (2D) materials, have small and tunable band gaps between graphene and transition metal dichalcogenides, giving versatile electrical properties. While their microelectronic or optoelectronic properties are being extensively explored, there remains a lack of study on Xenes' uniquely advantageous thermoelectric performance. This review highlights state‐of‐the‐art experimental and theoretical progress in the thermoelectric effect and devices of IVA and VA Xenes. Vertically displaced, a.k.a. "buckled" or "puckered," atomic arrays result in exotic and tunable electrical or thermal transport behaviors. Different from chemical doping strategies usually employed in bulk thermoelectric materials, 2D Xenes can be tuned by physical means, such as atomic layer control and quantum confinement effects. A precise and compatible platform for 2D thermoelectric effect and devices study is available via the engagement between micro/nanofabrication of 2D Xene transistors and thermal property measurement techniques. This review also reveals potential thermoelectric applications of Xenes and their compounds (Bi2Te3, Bi2Se3, etc.), such as accurate stretchable temperature sensors, fast terahertz photodetectors, and so on. [ABSTRACT FROM AUTHOR]

2D monoelemental nanomaterials (Xenes) have shown tremendous potential for versatile biomedical applications. Bismuth, as a heavy element in pnictogens, has acquired massive research interest due to its unique optical performance, high biocompatibility, stability, and relatively low cost. However, the utilization of 2D bismuthene in nanomedicine has not been achieved because of the difficulty in engineering bismuthene with crucial structural/compositional characteristics for satisfying strict biomedical requirements. Herein, to address this Gordian knot, a facile strategy to intercalate and delaminate Bi bulk for generating mass few‐layered 2D bismuthene with high yield by employing a water molecule mediated freezing–thawing process and sodium borohydride‐triggered reduction treatment is proposed. The resulting 2D bismuthene displays good optical performance in the near‐infrared (NIR) biowindow and can be excited via red light for reactive oxygen species generation, enabling applications in multiple photonic cancer nanomedicine settings, including photothermal hyperthermia and photodynamic therapy. Utilizing the intrinsic desirable optical absorbance and strong X‐ray attenuation of bismuthene, dual photonic therapy can be conducted under the supervision of photoacoustic/computed tomography guided multimodal imaging. This research not only offers a potential mass‐production ready, cost‐effective, and eco‐efficient methodology for engineering 2D Xenes, but also exploits an innovative 2D bismuthene based photonic cancer nanomedicine. [ABSTRACT FROM AUTHOR]

With black phosphorus being a promising two-dimensional layered semiconductor for application to electronics and optoelectronics, an issue remains as to how heat diffusion is managed when black phosphorus is interfaced with metals, namely in a typical device heterojunction. We use Raman spectroscopy to investigate how the laser-induced heat affects the phonon modes at the interface by comparing the experimental data with a finite element simulation based on a localized heat diffusion. The best convergence is found taking into account an effective interface thermal conductance, thus indicating that heat dissipation at the Au-supported black phosphorus nanosheets is limited by interface effect.

The 2D graphene (G) nanosheets (NSs) discovery is amound the foremost revolutionary incidents in materials science history. This discovery has stimulated huge attention in the study of other novel 2D materials (2DMs). This trend might be called modern day "alchemy," where the basic aim is to convert most of periodic table elements into G like 2D structures. Monoelemental, atomically thin 2DMs, called "Xenes" ("X" = group (III–VI)A elements, "ene" suffix that indicates one atom thick 2D layer of atoms) which are a newly invented family among nanomaterials. The number of predicted and experimentally synthesized 2D Xene materials of group IVA, i.e., G's siblings, has gained attention in nanosize devices. Such materials involve buckle structures that have recently been experimentally fabricated. The 2D Xene materials analog to G offer exciting potential for novel sensing applications. The group IVA Xenes, in cooperation with their ligand‐functionalized derivatives, arrange in a honeycomb lattice analogous to G but through a changeable degree of buckling. Their electronic structure ranges from trivial insulators passing via semiconductors with tunable gaps, to semimetallic, depending on substrate, chemical functionalization, and strain. In this review, different potential synthesis methods for group IVA 2D Xenes are briefly presented. A brief overview of their properties obtained theoretically and experimentally is presented, and finally their potential sensing applications are discussed. [ABSTRACT FROM AUTHOR]

Elemental 2D materials (E2DMs) have been attracting considerable attention owing to their chemical simplicity and excellent/exotic properties. However, the lack of robust chemical synthetic methods seriously limits their potential. Here, a surfactant-free liquid-phase synthesis of high-quality 2D tellurium is reported based on ultrasonication-assisted exfoliation of metastable 1T'-MoTe 2 . The as-grown 2D tellurium nanosheets exhibit excellent single crystallinity, ideal 2D morphology, surfactant-free surface, and negligible 1D by-products. Furthermore, a unique growth mechanism based on the atomic escape of Te atoms from metastable transition metal dichalcogenides and guided 2D growth in the liquid phase is proposed and verified. 2D tellurium-based field-effect transistors show ultrahigh hole mobility exceeding 1000 cm 2  V -1  s -1 at room temperature attributing to the high crystallinity and surfactant-free surface, and exceptional chemical and operational stability using both solid-state dielectric and liquid-state electrical double layer. The facile ultrasonication-assisted synthesis of high-quality 2D tellurium paves the way for further exploration of E2DMs and expands the scope of liquid-phase exfoliation (LPE) methodology toward the controlled wet-chemical synthesis of functional nanomaterials., (© 2023 Wiley‐VCH GmbH.)

Heterostacks formed by combining two-dimensional materials show novel properties which are of great interest for new applications in electronics, photonics and even twistronics, the new emerging field born after the outstanding discoveries on twisted graphene. Here, we report the direct growth of tin nanosheets at the two-dimensional limit via molecular beam epitaxy on chemical vapor deposited graphene on Al 2 O 3 (0001). The mutual interaction between the tin nanosheets and graphene is evidenced by structural and chemical investigations. On the one hand, Raman spectroscopy indicates that graphene undergoes compressive strain after the tin growth, while no charge transfer is observed. On the other hand, chemical analysis shows that tin nanosheets interaction with sapphire is mediated by graphene avoiding the tin oxidation occurring in the direct growth on this substrate. Remarkably, optical measurements show that the absorption of tin nanosheets exhibits a graphene-like behavior with a strong absorption in the ultraviolet photon energy range, therein resulting in a different optical response compared to tin nanosheets on bare sapphire. The optical properties of ultra-thin tin films therefore represent an open and flexible playground for the absorption of light in a broad range of the electromagnetic spectrum and technologically relevant applications for photon harvesting and sensors., (Creative Commons Attribution license.)

Here, two novel approaches for disassembling epitaxial silicene from the native substrate and transferring onto arbitrary target substrates are presented. From the processing perspective, the two methodologies open up a new route for handling silicene, and in general any epitaxial Xene, in view of establishing reliable process flows for the development of a Xene‐based nanotechnology. Integration of silicene in a back‐gated controlled device architecture is demonstrated and the built up of unique multi‐stack heterostructures between silicene, but potentially every Xene, and other technological relevant materials, like transparent conductive oxides and transition metal dichalcogenides is shown. [ABSTRACT FROM AUTHOR]

As an emerging subclass of 2D materials, Xenes (e.g., borophene, silicene, germanene, stanene, phosphorene, arsenene, antimonene, and bismuthene) consist of one single element and have opened the door for various important applications. Benefiting from their impressive characteristics, including ultrathin folded structure, ultrahigh surface–volume ratio, excellent mechanical strength and flexibility, Xenes are considered as promising electrode materials in the field of electrochemical energy with large capacity, high rate, and high safety. This review provides a comprehensive summary of selected properties, synthetic challenges, and the latest theoretical and experimental advances in the energy‐related applications of Xenes, including Li/Na ion batteries, Li–S batteries, electrocatalysis, and supercapacitors. Finally, the challenges and outlook of this emerging field are discussed. [ABSTRACT FROM AUTHOR]

The race to scale down electronic circuits has resulted in the novel two-dimensional (2D) materials. Graphene, after its discovery in 2004, topped the list on account of its superior electronic, optical, mechanical and transport properties. Since, graphene possesses zero band gap, it could not be used in digital circuits; so other potential 2D materials have been studied. Materials like transition metal dichalcogenides (TMDs), 2D oxides, hexagonal boron nitride and 2D Xenes (silicene, borophene, stanene, phosphorene and borophene) belong to the plethora of materials following the discovery of graphene. They apparently show potential in quantum computing and superfast electronics. They display ballistic transport and relativistic properties due to the mass-less fermions. Quantum spin Hall effect too is observed along with quantum Hall effect in many of them, which advocates their use in spintronics. Owing to these superior properties, they appear to be promising candidates for a paradigm shift from microelectronics to nanoelectronics. The 2D structural analogues of graphene, i.e. silicene, borophene, stanene, phosphorene and germanene are fast emerging alternative 2D materials compared to 2D oxides and TMDs, since they have a better degree of integration with the existing silicon-based technology. This article surveys the emerging 2D materials which hold promise in the future. [ABSTRACT FROM AUTHOR]

The recent outcomes related to the Xenes, the two-dimensional (2D) monoelemental graphene-like materials, in three interdisciplinary fields such as electronics, photonics and processing are here reviewed by focusing on peculiar growth and device integration aspects. In contrast with forerunner 2D materials such as graphene and transition metal dichalcogenides, the Xenes pose new and intriguing challenges for their synthesis and exploitation because of their artificial nature and stabilization issues. This effort is however rewarded by a fascinating and versatile scenario where the manipulation of the matter properties at the atomic scale paves the way to potential applications never reported to date. The current state-of-the-art about electronic integration of the Xenes, their optical and photonics properties, and the developed processing methodologies are summarized, whereas future challenges and critical aspects are tentatively outlined.

In the realm of 2D layered materials, the monoelemental group 14 Xene, germanene, as the germanium analog of graphene, has emerged as the next prospective candidate. Preceded by silicon, germanium is widely used in the semiconductor industry; thus, germanene is deemed compatible with existing semiconductor technologies. Germanene consists of mixed sp 2 -sp 3 -hybridized networks in a buckled hexagonal honeycomb structure. Chemical exfoliation of Zintl phases, such as CaGe 2 , specifically the topotactical deintercalation in acidic media, removes the alkaline earth metal ions Ca 2+ , giving rise to layered germanane (germanene with the Ge centers covalently saturated with terminal hydrogen atoms). Diverse variants of functionalized germananes (with covalent group(s) termination) can be obtained by varying the topotactical deintercalation precursors, elevating the game with limitless functionalization possibilities for customizable properties or new functionalities. The preparation of Zintl phases to the details of functionalized and modified germananes and their properties, and the additional exfoliation step to achieve mono- or few-layer germananes, are comprehensively covered. The progress and challenges of 2D functionalized germananes in optoelectronics, catalysis, energy conversion and storage, sensors, and biomedical areas are reviewed. This review provides insight into designing and exploring this class of atomically thin semiconductors in realizing future nanoarchitectonics., (© 2022 Wiley-VCH GmbH.)

The recent outcomes related to the Xenes, the two-dimensional (2D) monoelemental graphene-like materials, in three interdisciplinary fields such as electronics, photonics and processing are here reviewed by focusing on peculiar growth and device integration aspects. In contrast with forerunner 2D materials such as graphene and transition metal dichalcogenides, the Xenes pose new and intriguing challenges for their synthesis and exploitation because of their artificial nature and stabilization issues. This effort is however rewarded by a fascinating and versatile scenario where the manipulation of the matter properties at the atomic scale paves the way to potential applications never reported to date. The current state-of-the-art about electronic integration of the Xenes, their optical and photonics properties, and the developed processing methodologies are summarized, whereas future challenges and critical aspects are tentatively outlined. [ABSTRACT FROM AUTHOR]

Among ultrathin monoelemental two-dimensional (2D) materials, bismuthene, the single layer of heavier group-VΑ element bismuth (Bi), has been predicted to have large non trivial gap. Here, we demonstrate the growth of Bi films by molecular beam epitaxy on 2D-HfTe 2 template. At the initial stage of Bi deposition (1-2 bilayers, BL), both the pseudocubic Bi(110) and the hexagonal Bi(111) phases are formed. When reaching 3 BL Bi, a transformation to pure hexagonal Bi(111) occurs. The electronic band structure of 3 BL Bi(111) films was measured by angle-resolved photoemission spectroscopy showing very good matching with the density functional theory band structure calculations of 3 BL free standing Bi(111). The grown Bi(111) thin film was capped with a protective Al 2 O 3 layer and its stability under ambient conditions, necessary for practical applications and device fabrication, was confirmed by x-ray photoelectron spectroscopy and Raman spectroscopy., (© 2021 IOP Publishing Ltd.)

• β -phase allotrope of Sb is synthetized by a new method based on MOCVD. • Thin Sb epitaxial nanocrystals are grown on Ge substrates by a Au-catalysed process. • Raman measurements and simulations indicate antimonene-like properties. • The new method can pave the way to large-area antimonene layers for novel devices. Synthetic two-dimensional (2D) mono-elemental crystals, namely X-enes, have recently emerged as a new frontier for atomically thin nanomaterials with on-demand properties. Among X-enes, antimonene, the β -phase allotrope of antimony, is formed by atoms arranged in buckled hexagonal rings bearing a comparatively higher environmental stability with respect to other players of this kind. However, the exploitation of monolayer or few-layer antimonene and other 2D materials in novel opto-electronic devices is still hurdled by the lack of scalable processes. Here, we demonstrated the viability of a bottom-up process for the epitaxial growth of antimonene-like nanocrystals (ANCs), based on a Metal-Organic Chemical Vapor Deposition (MOCVD) process, assisted by gold nanoparticles (Au NPs) on commensurate (1 1 1)-terminated Ge surfaces. The growth mechanism was investigated by large- and local-area microstructural analysis, revealing that the etching of germanium, catalyzed by the Au NPs, led to the ANCs growth on the exposed Ge (1 1 1) planes. As a supportive picture, ab-initio calculations rationalized this epitaxial relationship in terms of compressively strained β -phase ANCs. Our process could pave the way to the realization of large-area antimonene layers by a deposition process compatible with the current semiconductor manufacturing technology. [ABSTRACT FROM AUTHOR]

Isolation of graphene is today a milestone in condensed matter physics that paves the way to a new entire class of 2D synthetic materials referred to as Xenes with no analogous bulk layered allotropes. The booming rush to discover first novel and unprecedented materials flows into two generations of Xenes: the first one strictly relates to carbon being made of elements of the IV/14 column/group of the periodic table, and the second one includes elements of the adjacent columns. From borophene to tellurene, with rare exceptions, the physics and chemistry of the elements are rewritten and herein reviewed in terms of their fundamental and peculiar properties. Particular attention is paid to the epitaxial methodologies and configurational details, aiming at determining key points for nanotechnology applications of the Xenes afforded by scalability, quality, and stability aspects. Finally, the ongoing efforts to devise and realize applications based on the Xenes are summarized. [ABSTRACT FROM AUTHOR]