Recent advances in graphene and other 2D materials

TH-graphyne: a new porous bidimensional carbon allotrope

Graphyne and two-dimensional porous carbon-based materials have garnered significant attention due to their interesting structural characteristics and essential properties for new technological applications. Within this scope, this work investigates the structural, thermal, electronic, optical, and mechanical properties of a novel two-dimensional allotrope that combines triangular (T) and hexagonal (H) rings, connected by acetylenic linkages (graphyne-like), thus named TH-graphyne (TH-GY). This study comprehensively characterizes the proposed system's behavior using density functional theory, ab initio molecular dynamics, and classical reactive molecular dynamics simulations. Our results confirm the structural stability of TH-GY. AIMD simulations demonstrate the material's thermal stability at elevated temperatures, while phonon dispersions indicate its dynamical stability. Electronic band structure calculations show that the system is metallic. The analysis of optical properties reveals intense activity in the visible and UV regions, with pronounced anisotropy. A machine learning interatomic potentials model was developed for TH-GY and used to determine the mechanical behavior of the system, which exhibits Young's modulus ranging from 263 to 356 GPa, highlighting its flexibility. Classical reactive MD simulations elucidate the fracture behavior of TH-GY, revealing distinct fracture patterns and mechanical anisotropy.

Two-dimensional Be2P4 as a promising thermoelectric material and anode for Na/K-ion batteries

Incredibly effective and flexible energy conversion and storage systems hold great promise for portable self-powered electronic devices. Owing to their large surface area, exceptional atomic structures, superior electrical conductivity and good mechanical flexibility, two-dimensional (2D) materials are recognized as an attractive option for energy conversion and storage application. In this work, we examined the stability, electronic, thermoelectric and electrochemical aspects of a novel 2D Be2P4 monolayer by adopting density functional theory (DFT). The Be2P4 monolayer exhibits a direct semiconductor gap of 0.9 eV (HSE06), large Young's modulus (∼198 GPa), high carrier mobility (∼104 cm2 V-1 s-1) and a low excitonic binding energy of 0.11 eV. Our calculated findings suggest that Be2P4 shows a lattice thermal conductivity of 1.02 W m K-1 at 700 K, resulting in moderate thermoelectric performance (ZT ∼ 0.7), encouraging its use in thermoelectric materials. In addition, a higher adsorption energy of -2.28 eV (-2.52 eV) and less diffusion barrier of 0.22 eV (0.17 eV) for Na(K)-ion batteries promote fast ion transport in the Be2P4 monolayer. This material also shows a high specific capacity and superior energy density of 8460 W h kg-1 (8883 W h kg-1) for Na(K)-ion batteries. Thus, our results offer insightful information for investigating potential thermoelectric and flexible anode materials based on the Be2P4 monolayer.

Electron Localization and Mobility in Monolayer Fullerene Networks

The novel 2D quasi-hexagonal phase of covalently bonded fullerene molecules (qHP C60), the so-called graphullerene, has displayed far superior electron mobilities, if compared to the parent van der Waals three-dimensional crystal (vdW C60). Herein, we present a comparative study of the electronic properties of vdW and qHP C60 using state-of-the-art electronic-structure calculations and a full quantum-mechanical treatment of electron transfer. We show that both materials entail polaronic localization of electrons with similar binding energies (≈0.1 eV) and, therefore, they share the same charge transport via polaron hopping. In fact, we quantitatively reproduce the sizable increment of the electron mobility measured for qHP C60 and identify its origin in the increased electronic coupling between C60 units.

The progress of research on vacancies in HMF electrooxidation

5-Hydroxymethylfurfural (HMF), serving as a versatile platform compound bridging biomass resource and the fine chemicals industry, holds significant importance in biomass conversion processes. The electrooxidation of HMF plays a crucial role in yielding the valuable product (2,5-furandicarboxylic acid), which finds important applications in antimicrobial agents, pharmaceutical intermediates, polyester synthesis, and so on. Defect engineering stands as one of the most effective strategies for precisely synthesizing electrocatalytic materials, which could tune the electronic structure and coordination environment, and further altering the adsorption energy of HMF intermediate species, consequently increasing the kinetics of HMF electrooxidation. Thereinto, the most routine and effective defect are the anionic vacancies and cationic vacancies. In this concise review, the catalytic reaction mechanism for selective HMF oxidation is first elucidated, with a focus on the synthesis strategies involving both anionic and cationic vacancies. Recent advancements in various catalytic oxidation systems for HMF are summarized and synthesized from this perspective. Finally, the future research prospects for selective HMF oxidation are discussed.

A first-principles prediction of the structural, electronic, transport and photocatalytic properties of GaGeX3 (X = S, Se, Te) monolayers

The discovery of new 2D materials with superior properties motivates scientists to make breakthroughs in various applications. In this study, using calculations based on density functional theory (DFT), we have comprehensively investigated the geometrical characteristics and stability of GaGeX3 monolayers (X = S, Se, or Te), determining their electronic and transport properties, and some essential optical and photocatalytic properties. AIMD simulations show that these materials are highly structurally and thermodynamically stable. Notably, the GaGeSe3 monolayer is a semiconductor with a band gap of 1.9 eV and has a high photon absorption coefficient of up to 1.1 × 105 cm-1 in the visible region. The calculated solar-to-hydrogen conversion efficiency of the GaGeSe3 monolayer is 11.33%, which is relatively high compared to some published 2D materials. Furthermore, the electronic conductivity of the GaGeSe3 monolayer is 790.65 cm2 V-1 s-1. Our findings suggest that the GaGeSe3 monolayer is a new promising catalyst for the solar water-splitting reaction to give hydrogen and a potential new 2D material for electrical devices with high electron mobility.

Ti3AlC2 MAX Phase Modified Screen-Printed Electrode for the Fabrication of Hydrazine Sensor

Hydrazine is considered a powerful reducing agent and catalyst, showing diverse applications in agricultural industries, toxic degradation research, and wastewater management. Additionally, hydrazine can trigger some specific reactions when combined with suitable oxidants. Due to its highly polar nature, hydrazine can easily dissolve in alcohol, water, and various other polar solvents. Therefore, it can be extensively utilized in different areas of application and industries such as rocketry and various chemical applications. Despite its beneficial properties, hydrazine is unstable, posing significant risk due to its highly toxic nature. It is extremely hazardous to both human health and the environment. It can cause various illnesses and symptoms such as dizziness, temporary blindness, damage to the central nervous system, and even death when inhaled in sufficient quantities. Therefore, it is highly important to monitor the level of hydrazine to prevent its toxic and hazardous effects on human beings and the environment. In the present study, we discuss the simple fabrication of a disposable cost-effective and eco-friendly hydrazine sensor. We used a screen-printed carbon electrode, i.e., SPCE, as a base for the construction of a hydrazine sensor. The Ti3AlC2 MAX has been used as a suitable and efficient electrode material for the fabrication of disposable hydrazine sensors. We modified the active surface of the SPCE using a drop-casting approach. The resulting Ti3AlC2 MAX modified SPCE (Ti3AlC2@SPCE) has been utilized as an efficient and low-cost hydrazine sensor. Cyclic voltammetry, i.e., CV, and linear sweep voltammetry, viz., LSV, was employed as a sensing technique in this study. The optimization of pH and electrode material loading was conducted. The Ti3AlC2@SPCE exhibited excellent sensing performance toward hydrazine oxidation. A reasonable detection limit (0.01 µM) was achieved for hydrazine sensing. The fabricated sensor also demonstrated a reasonable linear range of 1-50 µM. This work provides the design and fabrication of simple disposable Ti3AlC2@SPCE as a suitable electrode for the determination of hydrazine using LSV technology.

Sonochemical synthesis of bioinspired graphene oxide-zinc oxide hydrogel for antibacterial painting on biodegradable polylactide film

Graphene oxide nanosheet (GO) is a multifunctional platform for binding with nanoparticles and stacking with two dimensional substrates. In this study, GO nanosheets were sonochemically decorated with zinc oxide nanoparticles (ZnO) and self-assembled into a hydrogel of GO-ZnO nanocomposite. The GO-ZnO hydrogel structure is a bioinspired approach for preserving graphene-based nanosheets from van der Waals stacking. X-ray diffraction analysis (XRD) showed that the sonochemical synthesis led to the formation of ZnO crystals on GO platforms. High water content (97.2%) of GO-ZnO hydrogel provided good property of ultrasonic dispersibility in water. Ultraviolet-visible spectroscopic analysis (UV-vis) revealed that optical band gap energy of ZnO nanoparticles (∼3.2 eV) GO-ZnO nanosheets (∼2.83 eV). Agar well diffusion tests presented effective antibacterial activities of GO-ZnO hydrogel against gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus). Especially, GO-ZnO hydrogel was directly used for brush painting on biodegradable polylactide (PLA) thin films. Graphene-based nanosheets with large surface area are key to van der Waals stacking and adhesion of GO-ZnO coating to the PLA substrate. The GO-ZnO/PLA films were characterized using photography, light transmittance spectroscopy, coating stability, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopic mapping (EDS), antibacterial test and mechanical tensile measurement. Specifically, GO-ZnO coating on PLA substrate exhibited stability in aqueous food simulants for packaging application. GO-ZnO coating inhibited the infectious growth ofE. colibiofilm. GO-ZnO/PLA films had strong tensile strength and elastic modulus. As a result, the investigation of antibacterial GO-ZnO hydrogel and GO-ZnO coating on PLA film is fundamental for sustainable development of packaging and biomedical applications.

Water-Triggered Self-Healing of Ti3C2Tx MXene Standalone Electrodes: Systematic Examination of Factors Affecting the Healing Process

MXenes, with their remarkable attributes, stand at the forefront of diverse applications. However, the challenge remains in sustaining their performance, especially concerning Ti3C2Tx MXene electrodes. Current self-healing techniques, although promising, often rely heavily on adjacent organic materials. This study illuminates a pioneering water-initiated self-healing mechanism tailored specifically for standalone MXene electrodes. Here, both water and select organic solvents seamlessly mend impaired regions. Comprehensive evaluations around solvent types, thermal conditions, and substrate nuances underline water's unmatched healing efficacy, attributed to its innate ability to forge enduring hydrogen bonds with MXenes. Optimal healing environments range from ambient conditions to a modest 50 °C. Notably, on substrates rich in hydroxyl groups, the healing efficiency remains consistently high. The proposed healing mechanism encompasses hydrogen bonding formation, capillary action-induced expansion of interlayer spacing, solvent lubrication, Gibbs free energy minimizing MXene nanosheet rearrangement, and solvent evaporation-triggered MXene layer recombination. MXenes' resilience is further showcased by their electrical revival from profound damages, culminating in the crafting of Joule-heated circuits and heaters.

Enhanced Electron Transfer Efficiency of Fructose Dehydrogenase onto Roll-to-Roll Thermal Stamped Laser-Patterned Reduced Graphene Oxide Films

Herein, a strategy to stamp laser-produced reduced graphene oxide (rGO) onto flexible polymers using only office-grade tools, namely, roll-to-roll thermal stamping, is proposed, proving for the first time its effectiveness for direct bioelectrocatalysis. This straightforward, scalable, and low-cost approach allows us to overcome the limits of the integration of laser-induced rGO-films in bioanalytical devices. Laser-produced rGO has been thermally stamped (TS) onto different polymeric substrates (PET, PVC, and EVA) using a simple roll-laminator; the obtained TS-rGO films have been compared with the native rGO (untransferred) via morphochemical and electrochemical characterization. Particularly, the direct electron transfer (DET) reaction between fructose dehydrogenase (FDH) and TS-rGO transducers has been investigated, with respect to the influence of the amount of enzyme on the catalytic process. Remarkable differences have been observed among TS-rGO transducers; PET proved to be the elective substrate to support the transfer of the laser-induced rGO, allowing the preservation of the morphochemical features of the native material and returning a reduced capacitive current. Noteworthily, TS-rGOs ensure superior electrocatalysis using a very low amount of FDH units (15 mU). Eventually, TS-rGO-based third-generation complete enzymatic biosensors were fabricated via low-cost benchtop technologies. TS-rGOPET exhibited bioanalytical performances superior to the native rGO, allowing a sensitive (0.0289 μA cm-2 μM-1) and reproducible (RSD = 3%, n = 3) d-fructose determination at the nanomolar level (LOD = 0.2 μM). TS-rGO exploitability as a point-of-need device was proved via the monitoring of d-fructose during banana (Musa acuminata) postharvest ripening, returning accurate (recoveries 110-90%; relative error -13/+1%) and reproducible (RSD ≤ 7%; n = 3) data.

Experimental and Theoretical Insights into Interfacial Properties of 2D Materials for Selective Water Transport Membranes: A Critical Review

Interfacial properties, such as wettability and friction, play critical roles in nanofluidics and desalination. Understanding the interfacial properties of two-dimensional (2D) materials is crucial in these applications due to the close interaction between liquids and the solid surface. The most important interfacial properties of a solid surface include the water contact angle, which quantifies the extent of interactions between the surface and water, and the water slip length, which determines how much faster water can flow on the surface beyond the predictions of continuum fluid mechanics. This Review seeks to elucidate the mechanism that governs the interfacial properties of diverse 2D materials, including transition metal dichalcogenides (e.g., MoS2), graphene, and hexagonal boron nitride (hBN). Our work consolidates existing experimental and computational insights into 2D material synthesis and modeling and explores their interfacial properties for desalination. We investigated the capabilities of density functional theory and molecular dynamics simulations in analyzing the interfacial properties of 2D materials. Specifically, we highlight how MD simulations have revolutionized our understanding of these properties, paving the way for their effective application in desalination. This Review of the synthesis and interfacial properties of 2D materials unlocks opportunities for further advancement and optimization in desalination.

Electroreduction of CO2 on Cu, Fe, or Ni-doped Diamane Sheets: A DFT Study

Poor mass transfer behavior and inherent activity limit the efficiency of traditional catalysts in electrocatalyzing carbon dioxide reduction reactions. However, the development of novel nanomaterials provides new strategies to solve the above problems. Herein, we propose novel single-metal atom catalysts, namely diamane-based electrocatalysts doped with Cu, Fe, and Ni, explored through density functional theory (DFT) calculations. We thoroughly investigated the doping pattern and energetics for different dopants. Furthermore, we systematically investigated the conversion process of CO2 to C1 or C2+ products, utilizing the free energy analysis of reaction pathways. Our results reveal that dopants could only be introduced into diamane following a specific pattern. Dopants significantly enhance the CO2 adsorption ability of diamane, with Fe and Ni proving notably more effective than Cu. After CO2 adsorption, Cu- and Fe-doped diamane prefer to catalyze CO2RR, while Ni-doped diamane favors hydrogen evolution reaction (HER). The C-C coupling reaction on Cu-hollow diamane, Cu-bridge diamane, and Fe-hollow diamane tends to be from C2+ products. Among all examined catalysts, Cu-hollow diamane shows better electro-catalytic performance. Our study demonstrates the feasibility of and contributes to the development of diamane-based electro-catalysts for CO2RR.

Single-fiber probes for combined sensing and imaging in biological tissue: recent developments and prospects

Single-fiber-based sensing and imaging probes enable the co-located and simultaneous observation and measurement (i.e., 'sense' and 'see') of intricate biological processes within deep anatomical structures. This innovation opens new opportunities for investigating complex physiological phenomena and potentially allows more accurate diagnosis and monitoring of disease. This prospective review starts with presenting recent studies of single-fiber-based probes for concurrent and co-located fluorescence-based sensing and imaging. Notwithstanding the successful initial demonstration of integrated sensing and imaging within single-fiber-based miniaturized devices, the realization of these devices with enhanced sensing sensitivity and imaging resolution poses notable challenges. These challenges, in turn, present opportunities for future research, including the design and fabrication of complex lens systems and fiber architectures, the integration of novel materials and other sensing and imaging techniques.

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.

Fe3O4/carbon-decorated graphene boosts photothermal conversion and storage of phase change materials

Pristine organic phase change materials (PCMs) are difficult to complete photothermal conversion and storage. To upgrade their photothermal conversion and storage capacity, we developed Fe-MOF (metal-organic framework) derived Fe3O4/C-decorated graphene (GP) based composite PCMs toward solar energy harvesting. Graphene is an excellent phonon conductor, and Fe3O4/C-GP as a photon capturer exhibits strong full-spectrum absorption. Additionally, Fe-MOF derived Fe3O4 nanoparticles are anchored on graphene nanosheets to reduce interfacial thermal resistance, shorten thermal diffusion path, and accelerate phonon transport. After the encapsulation of octadecanol (ODA) in Fe3O4/C-GP, ODA@Fe3O4/C-GP composite PCMs yield a high photothermal conversion efficiency of 88.18 % under 0.12 W/cm2 benefiting from the synergistic effect of 3D interconnected graphene framework and Fe3O4 nanoparticles with localized surface plasmon resonance effect. Moreover, ODA@Fe3O4/C-GP composite PCMs exhibit excellent latent heat storage stability, photothermal conversion stability and durable reliability after undergoing multiple cycle evaluation, boosting high-efficiency utilization of solar energy.

The Physical Mechanism of Linear and Nonlinear Optical Properties of Nanographene-Induced Chiral Inversion

Based on density functional theory (DFT) and wave function analysis, the ultraviolet and visible spectrophotometry (UV-Vis) spectra and Raman spectra of 1-meso and 1-rac obtained by the chiral separation of chiral nanographenes are theoretically investigated. The electron excitation properties of 1-meso and 1-rac are studied by means of transition density matrix (TDM) and charge density difference (CDD) diagrams. The intermolecular interaction is discussed based on an independent gradient model based on Hirshfeld partition (IGMH). The interaction of 1-meso and 1-rac with the external environment is studied using the electrostatic potential (ESP), and the electron delocalization degree of 1-meso and 1-rac is studied based on the magnetically induced current under the external magnetic field. Through the chiral separation of 1-rac, two enantiomers, 1-(P, P) and 1-(M, M), were obtained. The electrical-magnetic interaction of the molecule is revealed by analyzing the electron circular dichroism (ECD) spectra of 1-meso, 1-(P, P) and 1-(M, M), the transition electric dipole moment (TEDM) and the transition magnetic dipole moment (TMDM). It is found that 1-(P, P) and 1-(M, M) have opposite chiral properties due to the inversion of the structure.

Electronic Structure of Metalloporphenes, Antiaromatic Analogues of Graphene

Zinc porphene is a two-dimensional material made of fully fused zinc porphyrins in a tetragonal lattice. It has a fully conjugated π-system, making it similar to graphene. Zinc porphene has recently been synthesized, and a combination of rough conductivity measurements and infrared and Raman spectroscopies all suggested that it is a semiconductor (Magnera, T.F. et al. Porphene and Porphite as Porphyrin Analogs of Graphene and Graphite, Nat. Commun.2023, 14, 6308). This is in contrast with all previous predictions of its electronic structure, which indicated metallic conductivity. We show that the gap-opening in zinc porphene is caused by a Peierls distortion of its unit cell from square to rectangular, thus giving the first account of its electronic structure in agreement with the experiment. Accounting for this distortion requires proper treatment of electron delocalization, which can be done using hybrid functionals with a substantial amount of exact exchange. Such a functional, PBE38, is then applied to predict the properties of many first transition row metalloporphenes, some of which have already been prepared. We find that changing the metal strongly affects the electronic structure of metalloporphenes, resulting in a rich variety of both metallic conductors and semiconductors, which may be of great interest to molecular electronics and spintronics. Properties of these materials are mostly governed by the extent of the Peierls distortion and the number of electrons in their π-system, analogous to changes in aromaticity observed in cyclic conjugated molecules upon oxidation or reduction. These results give an account of how the concept of antiaromaticity can be extended to periodic systems.

Laser-Induced photothermal activation of multilayer MoS2 with spatially controlled catalytic activity

This study investigates the effects of high-power laser irradiation on multilayer MoS2, a promising material for catalysis, optoelectronics, and energy applications. In addition to previously reported sculpting of MoS2 layers, we discovered a novel effect of laser-induced photothermal heating that drives the chemical activation of MoS2. The photothermal effect was confirmed by temperature-dependent experiments, in situ temperature measurements with nanolocalized probes, and simulations. Remarkably, we observed the reduction of Ag+ ions on laser-irradiated MoS2 layers, forming plasmonic nanostructures without external stimuli such as photons or chemical reducing agents. We attribute this phenomenon to the significant defect density within the laser-carved region and the surrounding area induced by photothermal effects. Further functionalization of the laser-modified MoS2 with 4-nitrobenzenethiol self-assembled monolayers demonstrated a significant increase in photocatalytic activity, close to 100% yield compared to the negligible activity of pristine material. Our findings contribute to a deeper understanding of the light-induced modification of MoS2 properties and introduce a novel method for spatially controlling the chemical activation of MoS2. This advancement holds significant potential in developing high-performance 2D semiconductors as nano-engineered catalytic materials.

Exfoliable Transition Metal Chalcogenide Semiconductor NbSe2I2

As the field of exfoliated van der Waals electronics grows to include complex heterostructures, the variety of available in-plane symmetries and geometries becomes increasingly valuable. In this work, we present an efficient chemical vapor transport synthesis of NbSe2I2 with the triclinic space group P1̅. This material contains Nb-Nb dimers and an in-plane crystallographic angle γ = 61.3°. We show that NbSe2I2 can be exfoliated down to few-layer and monolayer structures and use Raman spectroscopy to test the preservation of the crystal structure of exfoliated thin films. The crystal structure was verified by single-crystal and powder X-ray diffraction methods. Density functional theory calculations show triclinic NbSe2I2 to be a semiconductor with a band gap of around 1 eV, with similar band structure features for bulk and monolayer crystals. The physical properties of NbSe2I2 have been characterized by transport, thermal, optical, and magnetic measurements, demonstrating triclinic NbSe2I2 to be a diamagnetic semiconductor that does not exhibit any phase transformation below room temperature.

2D nanostructures: Potential in diagnosis and treatment of Alzheimer's disease

Two-dimensional (2D) nanomaterials have garnered enormous attention seemingly due to their unusual architecture and properties. Graphene and graphene oxide based 2D nanomaterials remained the most sought after for several years but the quest to design superior 2D nanomaterials which can find wider application gave rise to development of non-graphene 2D materials as well. Consequently, in addition to graphene based 2D nanomaterials, 2D nanostructures designed using macromolecules (such as DNAs, proteins, peptides and peptoids), transition metal dichalcogenides, transition-metal carbides and/or nitrides (MXene), black phosphorous, chitosan, hexagonal boron nitrides, and graphitic carbon nitride, and covalent organic frameworks have been developed. Interestingly, these 2D nanomaterials have found applications in diagnosis and treatment of various diseases including Alzheimer's disease (AD). Although AD is one of the most debilitating neurodegenerative conditions across the globe; unfortunately, there remains a paucity of effective diagnostic and/or therapeutic intervention for it till date. In this scenario, nanomaterial-based biosensors, or therapeutics especially 2D nanostructures are emerging to be promising in this regard. This review summarizes the diagnostic and therapeutic platforms developed for AD using 2D nanostructures. Collectively, it is worth mentioning that these 2D nanomaterials would seemingly provide an alternative and intriguing platform for biomedical interventions.

Fast and high-resolution mapping of van der Waals forces of 2D materials interfaces with bimodal AFM

High-spatial resolution mapping of van der Waals forces is relevant in several fields ranging from nanotechnology to colloidal science. The emergence of two-dimensional heterostructures assembled by van der Waals interactions has enhanced the interest of those measurements. Several AFM methods have been developed to measure the adhesion force between an AFM probe and the material of interest. However, a reliable and high-resolution method to measure the Hamaker constant remains elusive. We demonstrate that an atomic force microscope operated in a bimodal configuration enables fast, quantitative, and high-resolution mapping of the Hamaker constant of interfaces. The method is applied to map the Hamaker constant of monolayer, bilayer and multilayer MoS2 surfaces. Those interfaces are characterized with Hamaker constant and spatial resolutions of, respectively, 0.1 eV and 50 nm.

IOX1 epigenetically enhanced photothermal therapy of 3D-printing silicene scaffolds against osteosarcoma with favorable bone regeneration

Osteosarcoma (OS) is the third most common malignancy in adolescence. Currently, the treatments of OS confront great obstacles of tumor recurrence and critical bone defects after surgery, severely affecting the survival rates and living qualities of patients. Hence, it is urged to develop distinct biomaterials with both efficient tumor therapeutic and osteogenic functions. Although photothermal therapy (PTT) has aroused expanding interest, characterizing negligible invasiveness and high spatiotemporal adjustment, few studies discussed its drawbacks, such as thermal injury to adjacent normal tissue and exceeded laser power density, implying that focusing on sensitizing OS to PTT instead of simply elevating the laser power density may be a fresh way to enhance the PTT efficacy and attenuate the side/adverse effects. Herein, we successfully constructed 3D-printing silicene bioactive glass scaffolds with preferable PTT efficacy at the second near-infrared (NIR-II) biowindow and outstanding osteogenic biofunctions owing to the release of bioactive elements during degradation. Impressively, a histone demethylase inhibitor, IOX1, was introduced before PTT to sensitize OS to thermal therapy and minimize the side/adverse effects. This work offered a distinctive paradigm for optimizing the PTT efficacy of osteogenic scaffolds against OS with epigenetic modulation agents.

Probing charge traps at the 2D semiconductor/dielectric interface

The family of 2-dimensional (2D) semiconductors is a subject of intensive scientific research due to their potential in next-generation electronics. While offering many unique properties like atomic thickness and chemically inert surfaces, the integration of 2D semiconductors with conventional dielectric materials is challenging. The charge traps at the semiconductor/dielectric interface are among many issues to be addressed before these materials can be of industrial relevance. Conventional electrical characterization methods remain inadequate to quantify the traps at the 2D semiconductor/dielectric interface since the estimations of the density of interface traps, Dit, by different techniques may yield more than an order-of-magnitude discrepancy, even when extracted from the same device. Therefore, the challenge to quantify Dit at the 2D semiconductor/dielectric interface is about finding an accurate and reliable measurement method. In this review, we discuss characterization techniques which have been used to study the 2D semiconductor/dielectric interface. Specifically, we discuss the methods based on small-signal AC measurements, subthreshold slope measurements and low-frequency noise measurements. While these approaches were developed for silicon-based technology, 2D semiconductor devices possess a set of unique challenges requiring a careful re-evaluation when using these characterization techniques. We examine the conventional methods based on their efficacy and accuracy in differentiating various types of trap states and provide guidance to find an appropriate method for charge trap analysis and estimation of Dit at 2D semiconductor/dielectric interfaces.

Porphene and porphite as porphyrin analogs of graphene and graphite

Two-dimensional materials have unusual properties and promise applications in nanoelectronics, spintronics, photonics, (electro)catalysis, separations, and elsewhere. Most are inorganic and their properties are difficult to tune. Here we report the preparation of Zn porphene, a member of the previously only hypothetical organic metalloporphene family. Similar to graphene, these also are fully conjugated two-dimensional polymers, but are composed of fused metalloporphyrin rings. Zn porphene is synthesized on water surface by two-dimensional oxidative polymerization of a Langmuir layer of Zn porphyrin with K2IrCl6, reminiscent of known one-dimensional polymerization of pyrroles. It is transferable to other substrates and bridges μm-sized pits. Contrary to previous theoretical predictions of metallic conductivity, it is a p-type semiconductor due to a predicted Peierls distortion of its unit cell from square to rectangular, analogous to the appearance of bond-length alternation in antiaromatic molecules. The observed reversible insertion of various metal ions, possibly carrying a fifth or sixth ligand, promises tunability and even patterning of circuits on an atomic canvas without removing any π centers from conjugation.

Computational simulation-driven discovery of novel zeolite-like carbon materials as seawater desalination membranes

Freshwater is a scarce and vulnerable resource that has never encountered such an extensive focus on a nearly worldwide scale as it does today. Recently, it has been found that desalination powered by two-dimensional (2D) carbon materials as separation membranes has significantly reduced the operational costs and complexity but presents heavy requirements for the structural stability and separation properties of the membrane materials. Here, we combined carbon materials with promising adsorption properties and zeolites characterized by a regular pore structure to obtain a zeolite-like structured carbon membrane Zeo-C and investigated the suitability of the Zeo-C membrane for seawater desalination based on the computational-simulation-driven approach. The results of molecular dynamics (MD) simulations and density functional theory (DFT) calculations revealed that the periodic pore distribution conferred favorable structural stability and mechanical strength to the Zeo-C desalination membrane. The rejection rate of Na⁺ and Cl^- is ensured at 100% under a pressure of 40-70 MPa, and that of Na⁺ could reach 97.85% even though the pressure increases to 80 MPa, exhibiting superior desalination properties. The porous nature of the zeolite-like structure and the low free energy potential barrier are conducive for reliable adsorption and homogeneous diffusion of salt ions, which facilitates the acquisition of desirable water molecule permeability and salt ion selectivity. In particular, the interlinked delocalized π-network imparts inherent metallicity to Zeo-C for self-cleaning in response to electrical stimulation, thereby extending the lifetime of the desalination membrane. These studies have greatly encouraged theoretical innovations and serve as a guiding reference for desalination materials.

Theoretical prediction on net boroxene as a promising Li/Na-ion batteries anode

Novel two-dimensional (2D) electrode materials have become a new frontier for mining electrode materials for Li-ion batteries (LIBs) and Na-ion batteries (NIBs). Herein, based on first-principles calculations, we present a systematic study on the Li and Na storage behaviors in Calypso-predicted completely flat 2D boron oxide (l-B₂O) with large mesh pores. We start our calculations from geometrical optimization, followed by a performance evaluation of Li/Na adsorption and migration processes. Finally, the specific capacity and average open-circuit voltage are evaluated. Our study reveals that l-B₂O has good electrical conductivity before and after Li/Na adsorption and the Li/Na diffusion barrier height and average open-circuit voltage are both low, which is beneficial to the rate performance and full-cell operation voltage, respectively. Furthermore, it suffers a small lattice change (<1.7%), ensuring good cycling performance. In particular, we find that the Li and Na theoretical specific capacities of l-B₂O can reach up to 1068.5 mA h g^-1 and 712.3 mA h g^-1, respectively, which are almost 2-3 times higher than graphite (372 mA h g^-1). All the above outcomes indicate that 2D l-B₂O is a promising anode material for LIBs and NIBs.

On the Road to the Frontiers of Lithium-Ion Batteries: A Review and Outlook of Graphene Anodes

Graphene has long been recognized as a potential anode for next-generation lithium-ion batteries (LIBs). The past decade has witnessed the rapid advancement of graphene anodes, and considerable breakthroughs are achieved so far. In this review, the aim is to provide a research roadmap of graphene anodes toward practical LIBs. The Li storage mechanism of graphene is started with and then the approaches to improve its electrochemical performance are comprehensively summarized. First, morphologically engineered graphene anodes with porous, spheric, ribboned, defective and holey structures display improved capacity and rate performance owing to their highly accessible surface area, interconnected diffusion channels, and sufficient active sites. Surface-modified graphene anodes with less aggregation, fast electrons/ions transportation, and optimal solid electrolyte interphase are discussed, demonstrating the close connection between the surface structure and electrochemical activity of graphene. Second, graphene derivatives anodes prepared by heteroatom doping and covalent functionalization are outlined, which show great advantages in boosting the Li storage performances because of the additionally introduced defect/active sites for further Li accommodation. Furthermore, binder-free and free-standing graphene electrodes are presented, exhibiting great prospects for high-energy-density and flexible LIBs. Finally, the remaining challenges and future opportunities of practically available graphene anodes for advanced LIBs are highlighted.

Polarization Control in Integrated Graphene-Silicon Quantum Photonics Waveguides

We numerically investigated the use of graphene nanoribbons placed on top of silicon-on-insulator (SOI) strip waveguides for light polarization control in silicon photonic-integrated waveguides. We found that two factors mainly affected the polarization control: the graphene chemical potential and the geometrical parameters of the waveguide, such as the waveguide and nanoribbon widths and distance. We show that the graphene chemical potential influences both TE and TM polarizations almost in the same way, while the waveguide width tapering enables both TE-pass and TM-pass polarizing functionalities. Overall, by increasing the oxide spacer thickness between the silicon waveguide and the top graphene layer, the device insertion losses can be reduced, while preserving a high polarization extinction ratio.

Steroid hormone-inducible biosensor based on EGFP-tagged and environmental application

Steroid hormones as a class of emerging organic pollutant and high concern, due to their potential risks for human and environmental. Accurate analytical methods of steroid hormones are necessary in quantifying and monitoring. Biosensor is a promising technique. In this study, though part of 3α-HSD DNA to construct a regulatory plasmid and with the EGFP reporter gene to generate a reporter plasmid. Separately transformed into Escherichia coli strain BL21 and extracted the cell lysates as novel biosensor reagents. Analyzed the total amounts of steroid hormones in water, sediment, and soil samples using biosensor reagents, and compared these results with those obtained by HPLC. In summary, detection method using an EGFP reporter that can detect trace amounts of steroid hormones to reached fg/L. The optimal reaction time range and temperature were 30 min and 30 °C, respectively, while the most suitable organic solvent for the steroid hormone was 100% ethanol, up to 96-well plate format. This method is very suitable for high-throughput detection of environmental steroid hormone pollutants.

Self-Bending Behavior and Varying Bending Stiffness of Black Phosphorus/Molybdenum Disulfide (BP/MoS2) Heterostructure

Vertically-stacked black phosphorus/molybdenum disulfide (BP/MoS₂) heterostructures have broad prospects in flexible electronics. Bending is a common and highly concerned deformation for these flexible devices. However, the discrepancy in structures and properties among the components of 2D heterostructures often induces complex bending deformations. Here, the bending behaviors of BP, MoS₂ and BP/MoS₂ are investigated based on a molecular dynamics simulation. Compared with the constant bending stiffness of individual BP and MoS₂, that of BP/MoS₂ varies with the bending angle. Notably, a self-bending configuration induced by the lattice mismatch and size difference is found in BP/MoS₂. The corresponding self-bending amplitude depends on the degree of size difference of each component and the "soft/hard" competition between them. Moreover, the size difference leads to a weakened bending stiffness, which is ascribed to the reduction in interlayer interaction. A prediction formula is proposed to evaluate the bending stiffness of BP/MoS₂ with the size difference. This finding reveals novel ways for regulating the bending properties of 2D heterostructures, including the bending angle, characteristic size and stacking order. It offers an effective strategy for designing flexible devices with tunable bending performance.

Biomimetically Inspired Highly Homogeneous Hydrophilization of Graphene with Poly(l-DOPA): Toward Electroconductive Coatings from Water-Processable Paints

Water-based processing of graphene-typically considered as physicochemically incompatible with water in the macroscale-emerges as the key challenge among the central postulates of green nanotechnology. These problematic concerns are derived from the complex nature of graphene in the family of sp2-carbon nanoallotropes. Indeed, nanomaterials hidden under the common "graphene" signboard are very rich in morphological and physicochemical variants. In this work, inspired by the adhesion chemistry of mussel biomaterials, we have synthesized novel, water-processable graphene-polylevodopa (PDOPA) hybrids. Graphene and PDOPA were covalently amalgamated via the "growth-from" polymerization of l-DOPA (l-3,4-dihydroxyphenylalanine) monomer in air, yielding homogeneously PDOPA-coated (23 wt %) (of thickness 10-20 nm) hydrophilic flakes. The hybrids formed >1 year stable and water-processable aqueous dispersions and further conveniently processable paints of viscosity 0.4 Pa·s at 20 s-1 and a low yield stress τ0 up to 0.12 Pa, hence exhibiting long shelf-life stability and lacking sagging after application. Demonstrating their applicability, we have found them as surfactant-like nanoparticles stabilizing the larger, pristine graphene agglomerates in water in the optimized graphene/graphene-PDOPA weight ratio of 9:1. These characteristics enabled the manufacture of conveniently paintable coatings of low surface resistivity of 1.9 kΩ sq-1 (0.21 Ω·m) which, in turn, emerge as potentially applicable in textronics, radar-absorbing materials, or electromagnetic interference shielding.

Ultrasensitive electrochemical sensor for detection of rutin antioxidant by layered Ti3Al0.5Cu0.5C2 MAX phase

MAX phases have attracted great attention due to unique features such as thermal and electrical conductivity, easy fabrication, heat resistant, and lightweight. In this study, an easy and green method was employed to successfully develop a Ti₃Al_0.5Cu_0.5C₂ MAX phase structure, and a Ti₃Al_0.5Cu_0.5C₂ based glassy carbon electrode (GCE) was applied for the electrochemical determination of rutin antioxidants in mandarin and kiwi samples. The developed Ti₃Al_0.5Cu_0.5C₂ MAX phase was characterized by different techniques such as X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to obtain information on the structural and morphological properties. Electrochemical methods such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed for the determination of rutin using Ti₃Al_0.5Cu_0.5C₂/GCE. The GCE modified with Ti₃Al_0.5Cu_0.5C₂ demonstrated amplified electrochemical response (ca. 4.25 times) in comparison to the bare GCE towards rutin, and exhibited ultra-sensitivity and selectivity in the presence of other interfering antioxidants. Under the optimum conditions, good linearity in the range of 0.02-50.00 μmol L^-1 was obtained for rutin analysis by the Ti₃Al_0.5Cu_0.5C₂-based sensor with a limit of detection (LOD, 3σ/K) as low as 0.015 μmol L^-1. The fabricated Ti₃Al_0.5Cu_0.5C₂ MAX phase was applied to determine trace levels of rutin in mandarin and kiwi samples with validation by high-performance liquid chromatography (HPLC), thus highlighting its potential for the electrochemical determination of small molecules in the agricultural field.

Graphene and Other 2D Layered Nanomaterials and Hybrid Structures: Synthesis, Properties and Applications

The field of two-dimensional (2D) layered nanomaterials, their hybrid structures, and composite materials has been suddenly increasing since 2004, when graphene-almost certainly the most known 2D material-was successfully obtained from graphite via mechanical exfoliation [...].