Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices

Sensitive electrochemical detection of glycated hemoglobin (HbA1c) using cobalt metal-organic framework/two-dimensional molybdenum diselenide nanocomposite-based immunosensors amplified by polyoxometalate/DNA aptamer

Clinical diagnosis and long-term diabetes management are advanced by monitoring glycated hemoglobin A1c (HbA1c) levels. New sensitive sandwich-like immunosensors for the diagnosis of early diabetes toward detecting HbA1c and hemoglobin (Hb) are demonstrated for the first time. DNA aptamers are used for signal amplification in the sensors for the detection of HbA1c and Hb. The immunosensors are constructed by coating with a cobalt-based metal-organic framework (Co-MOF)/two-dimensional molybdenum diselenide (2D MoSe2) composite onto a working electrode of an ItalSens screen-printed electrode (SPE) inserted into a Sensit/Smart Potentiostat affixed to a smartphone. After the immobilization of the antibodies, the detection is obtained by incubating the resultant SPEs in target solutions and then detecting the response of Keggin-type polyoxometalate (POM) bound on the DNA aptamer chains. In the selected potential window, the POM (silicotungstic acid, H4[α-SiW12O40]) used in this study exhibits the electron-transfer processes I and II ([α-SiW12O40]4-/5- and [α-SiW12O40]5-/6-, respectively) in the acidic buffer electrolyte. Our proposed device demonstrates exceptional performance in the recovery test of %HbA1c in healthy human plasma samples. The sensitivity, selectivity, and stability of this immunosensor are exceedingly outstanding, which makes it one of the potential analytical devices for diagnosing early diabetes by a %HbA1c assay.

Borophene: The Frontier of Next-Generation Sensor Applications

Two-dimensional (2D) materials have captivated scientific imagination, and among this proliferating cadre of 2D compounds, borophene; a single layer of boron atoms emerges as a nonpareil substance owing to its distinctive structural, electronic, and mechanical properties. This review investigates the extraordinary properties that borophene possesses, notably in its χ3 and β12 phases, which add directional metallic behavior, along with quite a lot of mechanical plasticity and high carrier mobility. The synthesis of borophene has made significant strides thanks to cutting-edge techniques like molecular beam epitaxy (MBE), atomic layer deposition (ALD), and chemical vapor deposition (CVD) and physical vapor deposition (PVD), with recent innovations breaking through the scalability no-go areas that, in the past, hindered the material's widespread use. Borophene's superior electronic, thermal, and mechanical properties, in contrast to other 2D materials like graphene, accentuate its potential for diverse applications, particularly in the realm of next-generation sensors. It places particular emphasis on borophene's appositeness for sensor technology, detailing the structural intricacies and unique topological characteristics that make borophene an exceptional candidate. By focusing on the mechanisms that enable its high sensitivity and flexibility, the discussion brings to light the transformative potential of this interesting 2D material while concurrently addressing the state-of-the-art advancements in borophene research, thereby providing a forward-looking perspective on future opportunities and challenges. Ultimately, this work pinpoints how borophene, with its unprecedented properties and technological promise, is poised to reshape sensor technology and opens new avenues for exploration in the broader field of advanced functional materials.

Structure, stability and electronic properties of two-dimensional monolayer noble metals with triangular lattices: Cu, Ag, and Au

First-principles calculations were performed to investigate the structure, stability, and electronic properties of two-dimensional noble metal monolayers, including Cu, Ag, and Au, inspired by the recent synthesis of a two-dimensional gold monolayer. All 2D noble metals exhibit great stability with almost standard equilateral triangular lattice structures. These monolayers can survive 10 ps MD annealing simulations under 300 K. Phonon spectra do not exhibit negative frequencies. The independent elastic constants, Young's modulus, and Poisson's ratio were obtained, indicating that these monolayers are mechanically stable and slightly anisotropic. Additionally, the results of band structures and density of states (DOS) calculations reveal typical metallic electronic properties. The dumbbell-like Fermi surfaces suggest anisotropic electron transport properties. These findings highlight the immense application potential of 2D noble metal monolayers in diverse fields.

Altermagnetism: A Chemical Perspective

Altermagnets have been recently introduced as a classification of collinear, spin compensated magnetic materials that host net-zero magnetization yet display some electronic behaviors typically associated with noncompensated magnetic materials like ferromagnets. The emergence of such properties are a consequence of spin-split bands that arise under specific symmetry conditions in the limit of zero spin-orbit coupling. In this Perspective, we summarize the fundamental criteria for realizing an altermagnetic phase and present a qualitative electronic band structure derivation and symmetry analysis through chemical principles. We then discuss the properties that make altermagnets distinctive candidates for charge-to-spin conversion elements in spintronic devices and provide a brief review of some altermagnetic candidate materials. Finally, we discuss future directions for altermagnetism and highlight opportunities for chemists to advance this emerging field.

Two-Dimensional Organic-Inorganic van der Waals Hybrids

Two-dimensional organic-inorganic (2DOI) van der Waals hybrids (vdWhs) have emerged as a groundbreaking subclass of layer-stacked (opto-)electronic materials. The development of 2DOI-vdWhs via systematically integrating inorganic 2D layers with organic 2D crystals at the molecular/atomic scale extends the capabilities of traditional 2D inorganic vdWhs, thanks to their high synthetic flexibility and structural tunability. Constructing an organic-inorganic hybrid interface with atomic precision will unlock new opportunities for generating unique interfacial (opto-)electronic transport properties by combining the strengths of organic and inorganic layers, thus allowing us to satisfy the growing demand for multifunctional applications. Here, this review provides a comprehensive overview of the latest advancements in the chemical synthesis, structural characterization, and numerous applications of 2DOI-vdWhs. Firstly, we introduce the chemistry and the physical properties of the recently rising organic 2D crystals (O2DCs), which feature crystalline 2D nanostructures comprising carbon-rich repeated units linked by covalent/noncovalent bonds and exhibit strong in-plane extended π-conjugation and weak interlayer vdWs interaction. Simultaneously, representative inorganic 2D crystals (I2DCs) are briefly summarized. After that, the synthetic strategies will be systematically summarized, including synthesizing single-component O2DCs with dimensional control and their vdWhs with I2DCs. With these synthetic approaches, the control in the dimension, the stacking modes, and the composition of the 2DOI-vdWhs will be highlighted. Subsequently, a special focus will be given on the discussion of the optical and electronic properties of the single-component 2D materials and their vdWhs, which will be closely relevant to their structures, so that we can establish a general structure-property relationship of 2DOI-vdWhs. In addition to these physical properties, the (opto-)electronic devices such as transistors, photodetectors, sensors, spintronics, and neuromorphic devices as well as energy devices will be discussed. Finally, we provide an outlook to discuss the key challenges for the 2DOI-vdWhs and their future development. This review aims to provide a foundational understanding and inspire further innovation in the development of next-generation 2DOI-vdWhs with transformative technological potential.

Graphene-Based Materials for Bone Regeneration in Dentistry: A Systematic Review of In Vitro Applications and Material Comparisons

INTRODUCTION

Graphene, a two-dimensional arrangement of carbon atoms, has drawn significant interest in medical research due to its unique properties. In the context of bone regeneration, graphene has shown several promising applications. Its robust structure, electrical conductivity, and biocompatibility make it an ideal candidate for enhancing bone tissue regeneration and repair processes. Studies have revealed that the presence of graphene can stimulate the proliferation and differentiation of bone cells, thereby promoting the formation of new bone tissue. Additionally, its ability to act as an effective carrier for growth factors and drugs allows controlled release, facilitating the engineering of specific tissues for bone regeneration.

AIM

To assess the efficacy of graphene in enhancing bone regeneration through in vitro studies, identify key safety concerns, and propose directions for future research to optimize its clinical applicability.

MATERIALS AND METHODS

The present systematic review was carried out using the PRISMA 2020 guideline. A first search was carried out on 20 November 2023 and was later updated on 14 February and 15 April 2024 in the databases of PubMed, Scopus, and Web of Science. Those in vitro studies published in English that evaluated the potential for bone regeneration with graphene in dentistry and also those which met the search terms were selected. Furthermore, the quality of the studies was assessed following the modified CONSORT checklist of in vitro studies on dental materials.

RESULTS

A total of 17 in vitro studies met the inclusion criteria. Among these, 12 showed increased osteoblast adhesion, proliferation, and differentiation, along with notable enhancements in mineralized matrix formation. Additionally, they exhibited a significant upregulation of osteogenic markers such as RUNX and COL1 (p < 0.05). However, the variability in methodologies and a lack of long-term assessments were noted as critical gaps.

CONCLUSIONS

The evaluation of the efficacy and safety of graphene in bone regeneration in dentistry revealed significant potential. However, it is recognized that clinical implementation should be approached with caution, considering identified areas of improvement and suggestions for future research. Future studies should focus on standardized experimental designs, including in vivo studies to evaluate long-term safety, immune responses, and vascularization processes in realistic biological environments.

First Principles Study of p-Type Transition and Enhanced Optoelectronic Properties of g-ZnO Based on Diverse Doping Strategies

By utilizing first principles calculations, p-type transition in graphene-like zinc oxide (g-ZnO) through elemental doping was achieved, and the influence of different doping strategies on the electronic structure, energy band structure, and optoelectronic properties of g-ZnO was investigated. This research study delves into the effects of strategies such as single-acceptor doping, double-acceptor co-doping, and donor-acceptor co-doping on the properties of g-ZnO. This study found that single-acceptor doping with Li and Ag elements can form shallow acceptor levels, thereby facilitating p-type conductivity. Furthermore, the introduction of the donor element F can compensate for the deep acceptor levels formed by double-acceptor co-doping, transforming them into shallow acceptor levels and modulating the energy band structure. The co-doping strategy involving double-acceptor elements and a donor element further optimizes the properties of g-ZnO, such as reducing the bandgap and enhancing carrier mobility. Additionally, in terms of optical properties, g-Zn14Li2FO15 demonstrates outstanding performance in the visible-light region compared with other doping systems, especially generating a higher absorption peak around the wavelength of 520 nm. These findings provide a theoretical foundation for the application of g-ZnO in optoelectronic devices.

Atomistic insights into the nucleation and growth of hexagonal boron nitride and graphene heterostructures

Graphene and hexagonal boron nitride (hBN) are two-dimensional (2D) materials with a similar atomic structure but drastically different although complementary electronic properties. The large-scale synthesis of h-BN/graphene heterostructures with high crystallographic quality is required to fully benefit of the graphene electronic properties. In this study, we examine numerically the interaction of graphene precursors on hBN and of hBN precursors on graphene to gain deep insight of the CVD and MBE growth mechanism of graphene/hBN heterostructures. Density functional theory (DFT) calculations reveal the adsorption and diffusion behaviors for B, N, and C atoms on these surfaces. In particular, the adsorption energy is found to be similar to the diffusion barriers, except for the nearly free diffusion of B atoms on both graphene and hBN. We have also investigated the transition from individual atoms to graphene or h-BN seeds by considering the stability of linear chains as well as branched and ring seeds. Furthermore, for larger clusters, the triangular h-BN domains are found to be equally thermodynamically stable on graphene regardless of their orientation. These findings provide preliminary hints for the ability of graphene to grow on hBN layers and hBN layer on graphene.

Gentle tension stabilizes atomically thin metallenes

Metallenes are atomically thin two-dimensional (2D) materials lacking a layered structure in the bulk form. They can be stabilized by nanoscale constrictions like pores in 2D covalent templates, but the isotropic metallic bonding makes stabilization difficult. A few metallenes have been stabilized but comparison with theory predictions has not always been clear. Here, we use density-functional theory calculations to explore the energetics and dynamic stabilities of 45 metallenes at six lattices (honeycomb, square, hexagonal, and their buckled counterparts) and varying atomic densities. We found that of the 270 different crystalline lattices, 128 were dynamically stable at sporadic densities, mostly under tensile strain. At the energy minima, lattices were often dynamically unstable against amorphization and the breaking down of metallene planarity. Consequently, the results imply that crystalline metallenes should be seen through a novel paradigm: they should be considered not as membranes with fixed structures and lattice constants but as yielding membranes that can be stabilized better under tensile strain and low atomic density. Following this paradigm, we rank the most promising metallenes for 2D stability and hope that the paradigm will help develop new strategies to synthesize larger and more stable metallene samples for plasmonic, optical, and catalytic applications.

Tutorial on Describing, Classifying, and Visualizing Common Crystal Structures in Nanoscale Materials Systems

Crystal structures underpin many aspects of nanoscience and technology, from the arrangements of atoms in nanoscale materials to the ways in which nanoscale materials form and grow to the structures formed when nanoscale materials interact with each other and assemble. The impacts of crystal structures and their relationships to one another in nanoscale materials systems are vast. This Tutorial provides nanoscience researchers with highlights of many crystal structures that are commonly observed in nanoscale materials systems, as well as an overview of the tools and concepts that help to derive, describe, visualize, and rationalize key structural features. The scope of materials focuses on the elements and their compounds that are most frequently encountered as nanoscale materials, including both close-packed and nonclose-packed structures. Examples include three-dimensionally and two-dimensionally bonded compounds related to the rocksalt, nickel arsenide, fluorite, zincblende, wurtzite, cesium chloride, and perovskite structures, as well as layered perovskites, intergrowth compounds, MXenes, transition metal dichalcogenides, and other layered materials. Ordered versus disordered structures, high entropy materials, and instructive examples of more complex structures, including copper sulfides, are also discussed to demonstrate how structural visualization tools can be applied. The overall emphasis of this Tutorial is on the ways in which complex structures are derived from simpler building blocks, as well as the similarities and interrelationships among certain classes of structures that, at first glance, may be interpreted as being very different. Identifying and appreciating these structural relationships is useful to nanoscience researchers, as it allows them to deconstruct complex structures into simpler components, which is important for designing, understanding, and using nanoscale materials.

Advances in borophene based photodetectors for a sustainable tomorrow: a comprehensive review

Borophene, with its unique properties such as excellent conductivity, high thermal stability, and tunable electronic band structure, holds immense promise for advancing photodetector technology. These qualities make it an attractive material for enhancing the efficiency and performance of photodetectors across various wavelengths. Research so far has highlighted borophene's potential in improving sensitivity, response time, and overall functionality in optoelectronic devices. However, to fully realize the potential of borophene-based photodetectors, several challenges must be addressed. A major hurdle is the reproducibility and scalability of borophene synthesis, which is essential for its widespread use in practical applications. Furthermore, understanding the underlying physics of borophene and optimizing the device architecture are critical for achieving consistent performance under different operating conditions. These challenges must be overcome to enable the effective integration of borophene into commercial photodetector devices. A thorough evaluation of borophene-based photodetectors is necessary to guide future research and development in this field. This review will provide a detailed account of the current synthesis methods, discuss the experimental results, and identify the challenges that need to be addressed. Additionally, the review will explore potential strategies to overcome these obstacles, paving the way for significant advancements in solar cells, light-based sensors, and environmental monitoring systems. By addressing these issues, the development of borophene-based photodetectors could lead to substantial improvements in optoelectronic technology, benefiting various applications and industries.

Efficient Electron Injection into Graphullerene Enables Reversible NaC2 Sodium Storage

Sodium-ion batteries are emerging as promising alternatives to conventional lithium-based technology, offering solutions to challenges in large-scale grid storage. However, the capacity of conventional graphite-based anodes for storing Na-ions is inherently limited by suboptimal thermodynamic interactions and irreversible structural changes that occur in the anode during charge-discharge cycles. Herein, we present a computational design that explores the potential of graphullerene, a two-dimensional framework with interconnected fullerene moieties, for the reversible storage of Na-ions. A unique aspect of this design is the electron injection capacity into the graphullerene anode, reaching 15 electrons per fullerene moiety, which is the highest limit to date. This advancement enables large-scale Na-ion storage up to the stoichiometry of NaC2, exhibiting specific capacity of 551 mAhg-1 and averaged open circuit voltage of 0.18 V vs Na/Na+. In addition, the multilayered arrangement of stored Na-ions enhances the Na-ion diffusivity on the graphullerene surface, leading to rapid insertion and extraction kinetics. Thus, raising the electron injection limit offers a promising strategy to transform carbon-based anodes into suitable candidates for reversible Na-ion storage, without relying on artificial defect introduction or doping.

Vanadium Single Atoms Embedded in MoS2 Enabled Gut-Brain Axis Neurotransmitter Detection at pM Levels

The detection of monoamine neurotransmitters is of paramount importance as the neurotransmitters are the chemical messengers regulating the gut-brain axis (GBA). It requires real-time, ultrasensitive, and selective sensing of the neurotransmitters in the gastric/intestinal fluid. However, multi-components present in the gastric/intestinal fluid make sensing challenging to achieve in terms of ultra-high sensitivity and selectivity. Herein, an approach is introduced to utilize vanadium single atom catalytic (SAC) centers in van der Waals MoS2 (V-MoS2) to selectively detect real-time serotonin (5-HT) in artificial gastric/intestinal fluid. The synergetic effect of V-SACs and the surface S-bonds on the MoS2 surface, enables an extremely wide range of 5-HT detection (from 1 pM to 100 µM), with optimum selectivity and interference resistance. By combining density functional theory calculations and scanning transmission electron microscopy, it is concluded that the V-SACs embedded in the MoS2 network create active sites that greatly facilitate the charge exchange between the material and the 5-HT molecules. This result allows the 5-HT detection in GBA studies to be more reliable, and the material tunability provides a general platform to achieve real-time and multi-component detection of other monoamine neurotransmitters in GBA such as dopamine and norepinephrine.

Optical Properties of Graphene Nanoplatelets on Amorphous Germanium Substrates

In this work, the integration of graphene nanoplatelets (GNPs) with amorphous germanium (Ge) substrates is explored. The optical properties were characterized using Variable-Angle Spectroscopic Ellipsometry (VASE). The findings of this study reveal a strong interaction between GNPs and amorphous germanium, indicated by a significant optical absorption. This interaction suggests a change in the electronic structure of the GNPs, implying that amorphous germanium could enhance their effectiveness in devices such as optical sensors, photodetectors, and solar cells. Herein, the use of amorphous germanium as a substrate for GNPs, which notably increases their refractive index and extinction coefficient, is introduced for the first time. By exploring this unique material combination, this study provides new insights into the interaction between GNPs and amorphous substrates, paving the way for the develop of high-performance, scalable optoelectronic devices with enhanced efficiency.

Encapsulation of crystalline and amorphous Sb2S3 within carbon and boron nitride nanotubes

The recent rediscovery of 1D and quasi-1D (q-1D) van der Waals (vdW) crystals has laid foundation for the realization of emergent electronic, optical, and quantum-confined physical phenomena in both bulk and at the nanoscale. Of these, the highly anisotropic q-1D vdW crystal structure and the visible-light optical/optoelectronic properties of antimony trisulfide (Sb2S3) have led to its widespread consideration as a promising building block for photovoltaic and non-volatile phase change devices. However, while these applications will greatly benefit from well-defined and sub-nanometer-thick q-1D structures, little has been known about feasible synthetic routes that can access single covalent chains of Sb2S3. In this work, we explore how encapsulation in single or multi-walled carbon nanotubes (SWCNTs or MWCNTs) and visible-range transparent boron nitride nanotubes (BNNTs) influences the growth and phase of Sb2S3 nanostructures. We demonstrate that nanotubes with smaller diameters had a more pronounced effect in the crystallographic growth direction and orientation of Sb2S3 nanostructures, promoting the crystallization of the guest structures along the long-axis [010]-direction. As such, we were able to reliably access well-ordered few to single covalent chains of Sb2S3 when synthesized within defect-free SWCNTs with sub-2 nm inner diameters. Intriguingly, we found that the degree of crystalline order of Sb2S3 nanostructures was strongly influenced by the presence of defects and discontinuities along the Sb2S3-nanotube interface. We show that amorphous nanowire domains of Sb2S3 form around defect sites in larger, multi-walled nanotubes that manifest inner wall defects and discontinuities, suggesting a means to manipulate the crystallization dynamics of confined sub-10 nm-thick Sb2S3 nanostructures within nanotubes. Lastly, we show that ultranarrow amorphous Sb2S3 can impart functionality onto isolable BNNTs with photocurrent generation in the pA range which, alongside the dispersibility of the Sb2S3@BNNTs, could be leveraged to easily fabricate photoresistors only a few nm in width. Altogether, our results serve to solidify the understanding of how q-1D vdW pnictogen chalcogenides crystallize within confined synthetic platforms and are a step towards realizing functional materials from ensembles of encapsulated heterostructures.

Boosting Monolayer Transition Metal Dichalcogenides Growth by Hydrogen-Free Ramping during Chemical Vapor Deposition

The controlled vapor-phase synthesis of two-dimensional (2D) transition metal dichalcogenides (TMDs) is essential for functional applications. While chemical vapor deposition (CVD) techniques have been successful for transition metal sulfides, extending these methods to selenides and tellurides often faces challenges due to uncertain roles of hydrogen (H2) in their synthesis. Using CVD growth of MoSe2 as an example, this study illustrates the role of a H2-free environment during temperature ramping in suppressing the reduction of MoO3, which promotes effective vaporization and selenization of the Mo precursor to form MoSe2 monolayers with excellent crystal quality. As-synthesized MoSe2 monolayer-based field-effect transistors show excellent carrier mobility of up to 20.9 cm2/(V·s) with an on-off ratio of 7 × 107. This approach can be extended to other TMDs, such as WSe2, MoTe2, and MoSe2/WSe2 in-plane heterostructures. Our work provides a rational and facile approach to reproducibly synthesize high-quality TMD monolayers, facilitating their translation from laboratory to manufacturing.

Recent progress in on-surface synthesis of nanoporous graphene materials

Nanoporous graphene (NPG) materials are generated by removing internal degree-3 vertices from graphene and introducing nanopores with specific topological structures, which have been widely explored and exploited for applications in electronic devices, membranes, and energy storage. The inherent properties of NPGs, such as the band structures, field effect mobilities and topological properties, are crucially determined by the geometric structure of nanopores. On-surface synthesis is an emerging strategy to fabricate low-dimensional carbon nanostructures with atomic precision. In this review, we introduce the progress of on-surface synthesis of atomically precise NPGs, and classify NPGs from the aspects of element types, topological structures, pore shapes, and synthesis strategies. We aim to provide a comprehensive overview of the recent advancements, promoting interdisciplinary collaboration to further advance the synthesis and applications of NPGs.

Nanoscale Adhesion and Material Transfer at 2D MoS2-MoS2 Interfaces Elucidated by In Situ Transmission Electron Microscopy and Atomistic Simulations

Low-dimensional materials, such as MoS2, hold promise for use in a host of emerging applications, including flexible, wearable sensors due to their unique electrical, thermal, optical, mechanical, and tribological properties. The implementation of such devices requires an understanding of adhesive phenomena at the interfaces between these materials. Here, we describe combined nanoscale in situ transmission electron microscopy (TEM)/atomic force microscopy (AFM) experiments and simulations measuring the work of adhesion (Wadh) between self-mated contacts of ultrathin nominally amorphous and nanocrystalline MoS2 films deposited on Si scanning probe tips. A customized TEM/AFM nanoindenter permitted high-resolution imaging and force measurements in situ. The Wadh values for nanocrystalline and nominally amorphous MoS2 were 604 ± 323 mJ/m2 and 932 ± 647 mJ/m2, respectively, significantly higher than previously reported values for mechanically exfoliated MoS2 single crystals. Closely matched molecular dynamics (MD) simulations show that these high values can be explained by bonding between the opposing surfaces at defects such as grain boundaries. Simulations show that as grain size decreases, the number of bonds formed, the Wadh and its variability all increase, further supporting that interfacial covalent bond formation causes high adhesion. In some cases, sliding between delaminated MoS2 flakes during separation is observed, which further increases the Wadh and the range of adhesive interaction. These results indicate that for low adhesion, the MoS2 grains should be large relative to the contact area to limit the opportunity for bonding, whereas small grains may be beneficial, where high adhesion is needed to prevent device delamination in flexible systems.

Wetting and strain engineering of 2D materials on nanopatterned substrates

The fascinating realm of strain engineering and wetting transitions in two-dimensional (2D) materials takes place when placed on a two-dimensional array of nanopillars or one-dimensional rectangular grated substrates. Our investigation encompasses a diverse set of atomically thin 2D materials, including transition metal dichalcogenides, hexagonal boron nitride, and graphene, with a keen focus on the impact of van der Waals adhesion energies to the substrate on the wetting/dewetting behavior on nanopatterned substrates. We find a critical aspect ratio of the nanopillar or grating heights to the period of the pattern when the wetting/dewetting transition occurs. Furthermore, energy hysteresis analysis reveals dynamic detachment and re-engagement events during height adjustments, shedding light on energy barriers of 2D monolayer transferred on patterned substrates. Our findings offer avenues for strain engineering in 2D materials, leading to promising prospects for future technological applications.

Photodynamic impact of curcumin enhanced silver functionalized graphene nanocomposites on Candida virulence

Candida species are escalating resistance to conventional antifungal treatments, intensifying their virulence, and obstructing the effectiveness of antifungal medications. Addressing this challenge is essential for effectively managing Candida infections. The overarching objective is to advance the development of more efficient and precise therapies tailored to counter Candida infections. This study focuses on developing antifungal combined drugs using curcumin-enhanced silver-functionalized graphene nanocomposites (Cur-AgrGO) to effectively target key virulence factors of C. albicans, C. tropicalis, and C. glabrata (Candida spp.). The green reduction of graphene oxide (GO) using bioentities and active molecules makes this approach cost-effective and environmentally friendly. The nanocomposites were characterized using various techniques. Combining Cur-AgrGO with photodynamic therapy (PDT) demonstrated effective antifungal and antibiofilm activity with delayed growth and metabolism. The nanocomposites effectively suppressed hyphal transition and reduced key virulence factors, including proteinases, phospholipases, ergosterol levels, and cell membrane integrity. The findings suggest that Cur-AgrGO + PDT has potential as a treatment option for Candida infections. This innovative approach holds promise for treating Candida infections.

A substitutional quantum defect in WS2 discovered by high-throughput computational screening and fabricated by site-selective STM manipulation

Point defects in two-dimensional materials are of key interest for quantum information science. However, the parameter space of possible defects is immense, making the identification of high-performance quantum defects very challenging. Here, we perform high-throughput (HT) first-principles computational screening to search for promising quantum defects within WS2, which present localized levels in the band gap that can lead to bright optical transitions in the visible or telecom regime. Our computed database spans more than 700 charged defects formed through substitution on the tungsten or sulfur site. We found that sulfur substitutions enable the most promising quantum defects. We computationally identify the neutral cobalt substitution to sulfur (CoS 0 ) and fabricate it with scanning tunneling microscopy (STM). The CoS 0 electronic structure measured by STM agrees with first principles and showcases an attractive quantum defect. Our work shows how HT computational screening and nanoscale synthesis routes can be combined to design promising quantum defects.

Air-Stable, Large-Area 2D Metals and Semiconductors

Two-dimensional (2D) materials are popular for fundamental physics study and technological applications in next-generation electronics, spintronics, and optoelectronic devices due to a wide range of intriguing physical and chemical properties. Recently, the family of 2D metals and 2D semiconductors has been expanding rapidly because they offer properties once unknown to us. One of the challenges to fully access their properties is poor stability in ambient conditions. In the first half of this Review, we briefly summarize common methods of preparing 2D metals and highlight some recent approaches for making air-stable 2D metals. Additionally, we introduce the physicochemical properties of some air-stable 2D metals recently explored. The second half discusses the air stability and oxidation mechanisms of 2D transition metal dichalcogenides and some elemental 2D semiconductors. Their air stability can be enhanced by optimizing growth temperature, substrates, and precursors during 2D material growth to improve material quality, which will be discussed. Other methods, including doping, postgrowth annealing, and encapsulation of insulators that can suppress defects and isolate the encapsulated samples from the ambient environment, will be reviewed.

Two-Dimensional Semiconductors and Transistors for Future Integrated Circuits

Silicon transistors are approaching their physical limit, calling for the emergence of a technological revolution. As the acknowledged ultimate version of transistor channels, 2D semiconductors are of interest for the development of post-Moore electronics due to their useful properties and all-in-one potentials. Here, the promise and current status of 2D semiconductors and transistors are reviewed, from materials and devices to integrated applications. First, we outline the evolution and challenges of silicon-based integrated circuits, followed by a detailed discussion on the properties and preparation strategies of 2D semiconductors and van der Waals heterostructures. Subsequently, the significant progress of 2D transistors, including device optimization, large-scale integration, and unconventional devices, are presented. We also examine 2D semiconductors for advanced heterogeneous and multifunctional integration beyond CMOS. Finally, the key technical challenges and potential strategies for 2D transistors and integrated circuits are also discussed. We envision that the field of 2D semiconductors and transistors could yield substantial progress in the upcoming years and hope this review will trigger the interest of scientists planning their next experiment.

Physically Exfoliating 2D Materials: A Versatile Combination of Different Materials into a Layered Structure

Improving the properties of the existing two-dimensional (2D) materials is a major concern for many researchers today. Synergistic coupling of single-phase 2D material species with secondary functional materials has resulted in 2D nanohybrids with significantly enhanced properties beyond the sum of their individual components. In particular, nanohybrids created by alternatingly integrating different material species in the confined 2D nanometer regime have the potential to meet the needs of a wide variety of applications, particularly the many important energy-related applications that are of interest. However, scaling up production of 2D nanohybrids is still challenging, which is a major barrier to their practical application. Delamination and exfoliation by physical means separate the weakly bound 2D nanosheets into kinetically stable single- or few-layers. Herein, we provide a concise overview of recent achievements in the physical exfoliation-based fabrication of 2D nanohybrids featuring controlled heterolayered structures. Several strategies to efficiently produce heterolayered 2D nanohybrids in large quantities are described, such as (i) coexfoliation of different 2D species, (ii) aqueous-phase synthesis, and (iii) gas-phase synthesis. The versatility of the 2D nanohybrids was also illustrated by remarkable research examples, especially in energy-related applications.

Theoretical study of protein adsorption on graphene/h-BN heterostructures

The biological characteristics of planar heterojunction nanomaterials and their interactions with biomolecules are crucial for the potential application of these materials in the biomedical field. This study employed molecular dynamics (MD) simulations to investigate the interactions between proteins with distinct secondary structures (a single α-helix representing the minimal oligomeric domain protein, a single β-sheet representing the WW structural domain of the Yap65 protein, and a mixed α/β structure representing the BBA protein) and a planar two-dimensional heterojunction (a GRA/h-BN heterojunction consisting of a graphene nanoplate (GRA) and a hexagonal boron nitride nanoplate (h-BN)). The results indicate that all three kinds of protein can be quickly and stably adsorbed on the GRA/h-BN heterojunction due to the strong van der Waals interaction, regardless of their respective types, structures and initial orientations. Moreover, the proteins exhibit a pronounced binding preference for the hBN region of the GRA/h-BN heterojunction. Upon adsorption, the α-helix structure of the minimal oligomeric domain protein experiences partial or complete denaturation. Conversely, while the secondary structure of the single β-sheet and mixed α/β structure (BBA protein) undergoes slight changes (focus on the coil and turn regions), the main α-helix and β-sheet structures remain intact. The initial orientation significantly impacts the degree of protein adsorption and its position on the GRA/h-BN heterojunction. However, regardless of the initial orientation, proteins can ultimately be adsorbed onto the GRA/h-BN heterojunction. Furthermore, the initial orientation has a minor influence on the structural changes of proteins. Significantly, the combination of different secondary structures helps mitigate the denaturation of a single α-helix structure to some extent. Overall, the adsorption of proteins on GRA/h-BN is primarily driven by van der Waals and hydrophobic interactions. Proteins with β-sheet or mixed structures exhibit stronger biocompatibility on the GRA/h-BN heterojunction. Our research elucidated the biological characteristics of GRA/h-BN heterojunction nanomaterials and their interactions with proteins possessing diverse secondary structures. It offers a theoretical foundation for considering heterojunction nanomaterials as promising candidates for biomedical applications.

Application of Graphene Oxide in Oral Surgery: A Systematic Review

The current review aims to provide an overview of the most recent research in the last 10 years on the potentials of graphene in the dental surgery field, focusing on the potential of graphene oxide (GO) applied to implant surfaces and prosthetic abutment surfaces, as well as to the membranes and scaffolds used in Guided Bone Regeneration (GBR) procedures. "Graphene oxide" and "dental surgery" and "dentistry" were the search terms utilized on the databases Scopus, Web of Science, and Pubmed, with the Boolean operator "AND" and "OR". Reviewers worked in pairs to select studies based on specific inclusion and exclusion criteria. They included animal studies, clinical studies, or case reports, and in vitro and in vivo studies. However, they excluded systematic reviews, narrative reviews, and meta-analyses. Results: Of these 293 studies, 19 publications were included in this review. The field of graphene-based engineered nanomaterials in dentistry is expanding. Aside from its superior mechanical properties, electrical conductivity, and thermal stability, graphene and its derivatives may be functionalized with a variety of bioactive compounds, allowing them to be introduced into and improved upon various scaffolds used in regenerative dentistry. This review presents state-of-the-art graphene-based dental surgery applications. Even if further studies and investigations are still needed, the GO coating could improve clinical results in the examined dental surgery fields. Better osseointegration, as well as increased antibacterial and cytocompatible qualities, can benefit GO-coated implant surgery. On bacterially contaminated implant abutment surfaces, the CO coating may provide the optimum prospects for soft tissue sealing to occur. GBR proves to be a safe and stable material, improving both bone regeneration when using GO-enhanced graft materials as well as biocompatibility and mechanical properties of GO-incorporated membranes.

Probing the Electronic and Opto-Electronic Properties of Multilayer MoS2 Field-Effect Transistors at Low Temperatures

Transition metal dichalcogenides (TMDs)-based field-effect transistors (FETs) are being investigated vigorously for their promising applications in optoelectronics. Despite the high optical response reported in the literature, most of them are studied at room temperature. To extend the application of these materials in a photodetector, particularly at a low temperature, detailed understanding of the photo response behavior of these materials at low temperatures is crucial. Here we present a systematic investigation of temperature-dependent electronic and optoelectronic properties of few-layers MoS2 FETs, synthesized using the mechanical exfoliation of bulk MoS2 crystal, on the Si/SiO2 substrate. Our MoS2 FET show a room-temperature field-effect mobility μFE ~40 cm2·V-1·s-1, which increases with decreasing temperature, stabilizing at 80 cm2·V-1·s-1 below 100 K. The temperature-dependent (50 K < T < 300 K) photoconductivity measurements were investigated using a continuous laser source λ = 658 nm (E = 1.88 eV) over a broad range of effective illuminating laser intensity, Peff (0.02 μW < Peff < 0.6 μW). Photoconductivity measurements indicate a fractional power dependence of the steady-state photocurrent. The room-temperature photoresponsivity (R) obtained in these samples was found to be ~2 AW-1, and it increases as a function of decreasing temperature, reaching a maximum at T = 75 K. The optoelectronic properties of MoS2 at a low temperature give an insight into photocurrent generation mechanisms, which will help in altering/improving the performance of TMD-based devices for various applications.

Intensity-Dependent Optical Response of 2D LTMDs Suspensions: From Thermal to Electronic Nonlinearities

The nonlinear optical (NLO) response of photonic materials plays an important role in the understanding of light-matter interaction as well as pointing out a diversity of photonic and optoelectronic applications. Among the recently studied materials, 2D-LTMDs (bi-dimensional layered transition metal dichalcogenides) have appeared as a beyond-graphene nanomaterial with semiconducting and metallic optical properties. In this article, we review most of our work in studies of the NLO response of a series of 2D-LTMDs nanomaterials in suspension, using six different NLO techniques, namely hyper Rayleigh scattering, Z-scan, photoacoustic Z-scan, optical Kerr gate, and spatial self-phase modulation, besides the Fourier transform nonlinear optics technique, to infer the nonlinear optical response of semiconducting MoS2, MoSe2, MoTe2, WS2, semimetallic WTe2, ZrTe2, and metallic NbS2 and NbSe2. The nonlinear optical response from a thermal to non-thermal origin was studied, and the nonlinear refraction index and nonlinear absorption coefficient, where present, were measured. Theoretical support was given to explain the origin of the nonlinear responses, which is very dependent on the spectro-temporal regime of the optical source employed in the studies.

Recent Advances in 2D Material Theory, Synthesis, Properties, and Applications

Two-dimensional (2D) material research is rapidly evolving to broaden the spectrum of emergent 2D systems. Here, we review recent advances in the theory, synthesis, characterization, device, and quantum physics of 2D materials and their heterostructures. First, we shed insight into modeling of defects and intercalants, focusing on their formation pathways and strategic functionalities. We also review machine learning for synthesis and sensing applications of 2D materials. In addition, we highlight important development in the synthesis, processing, and characterization of various 2D materials (e.g., MXnenes, magnetic compounds, epitaxial layers, low-symmetry crystals, etc.) and discuss oxidation and strain gradient engineering in 2D materials. Next, we discuss the optical and phonon properties of 2D materials controlled by material inhomogeneity and give examples of multidimensional imaging and biosensing equipped with machine learning analysis based on 2D platforms. We then provide updates on mix-dimensional heterostructures using 2D building blocks for next-generation logic/memory devices and the quantum anomalous Hall devices of high-quality magnetic topological insulators, followed by advances in small twist-angle homojunctions and their exciting quantum transport. Finally, we provide the perspectives and future work on several topics mentioned in this review.

Recent advances and mechanism of antimicrobial efficacy of graphene-based materials: a review

Graphene-based materials have undergone substantial investigation in recent years owing to their wide array of physicochemical characteristics. Employment of these materials in the current state, where infectious illnesses caused by microbes have severely damaged human life, has found widespread application in combating fatal infectious diseases. These materials interact with the physicochemical characteristics of the microbial cell and alter or damage them. The current review is dedicated to molecular mechanisms underlying the antimicrobial property of graphene-based materials. Various physical and chemical mechanisms leading to cell membrane stress, mechanical wrapping, photo-thermal ablation as well as oxidative stress exerting antimicrobial effect have also been thoroughly discussed. Furthermore, an overview of the interactions of these materials with membrane lipids, proteins, and nucleic acids has been provided. A thorough understanding of discussed mechanisms and interactions is essential to develop extremely effective antimicrobial nanomaterial for application as an antimicrobial agent.

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Transferability of interatomic potentials for silicene

The ability of various interatomic potentials to reproduce the properties of silicene, that is, 2D single-layer silicon, polymorphs was examined. Structural and mechanical properties of flat, low-buckled, trigonal dumbbell, honeycomb dumbbell, and large honeycomb dumbbell silicene phases, were obtained using density functional theory and molecular statics calculations with Tersoff, MEAM, Stillinger-Weber, EDIP, ReaxFF, COMB, and machine-learning-based interatomic potentials. A quantitative systematic comparison and a discussion of the results obtained are reported.