Microwave Synthesized 2D Gold and Its 2D-2D Hybrids

Synthesis of Ti4Au3C3 and its derivative trilayer goldene through chemical exfoliation

Achieving large two-dimensional (2D) sheets of any metal is challenging due to their tendency to coalescence or cluster into 3D shapes. Recently, single-atom-thick gold sheets, termed goldene, was reported. Here, we ask if goldene can be extended to include multiple layers. The answer is yes, and trilayer goldene is the magic number, for reasons of electronegativity. Experiments are made to synthesize the atomically laminated phase Ti4Au3C3 through substitutional intercalation of Si layers in Ti4SiC3 for Au. Density functional theory calculations suggest that it is energetically favorable to insert three layers of Au into Ti4SiC3, compared to inserting a monolayer, a bilayer, or more than three layers. Isolated trilayer goldene sheets, ~100 nanometers wide and 6.7 angstroms thick, were obtained by chemically etching the Ti4C3 layers from Ti4Au3C3 templates. Furthermore, trilayer goldene is found in both hcp and fcc forms, where the hcp is ~50 milli-electron volts per atom more stable at room temperature from ab initio molecular dynamic simulations.

Ultrafast Microwave-Synthesized 2D/1D MnO2/Carbon Nanotube Hybrid for Bilirubin Detection in Simulated Blood Serum

Hybridization of carbon nanotubes (CNTs) and manganese dioxide (MnO2) integrates the biocompatibility and outstanding electrocatalytic activity of MnO2 with the exceptional conductivity of CNTs, thus providing a superior synergistic sensing platform for the detection of biomolecules. However, the existing methods for synthesizing MnO2/CNT hybrids are complex and inefficient, resulting in low yields and limited surface functionalities. Hence, in this study, we present a low-cost and ultrafast solid-phase synthesis of the MnO2/CNT hybrid using a facile microwave technique to detect a crucial biomolecule bilirubin. The successful synthesis of the MnO2/CNT hybrid is confirmed through characteristic Raman and X-ray diffraction peaks, while morphology is analyzed by imaging techniques such as FESEM and HRTEM. The MnO2/CNT/nickel foam (NF) sensor is thereafter used for the electrochemical detection of bilirubin. The sensor demonstrates a wide linear detection range from 10 nM to 1 mM, with a sensitivity of 6.87 mA nM-1 cm-2 toward bilirubin, as determined through the differential pulse voltammetry technique. The lower limit of detection is noted at 3.3 nM (=3.3 S/m). Furthermore, the as-fabricated sensor showcases high selectivity against the interfering species. Real-time analysis conducted in simulated blood serum using the standard addition method reveals an outstanding recovery percentage of approximately 98%. The conductive MnO2/CNT hybrid interacts robustly with bilirubin, aided by the porous NF substrate for stability, catalytic activity, and rapid electron transfer, enabling sensitive bilirubin detection. The work provides an ultrafast, low-cost, and high-yield solid-phase microwave synthesis of MnO2/CNT hybrid material and broadens its application in the detection of biological specimens for clinical diagnosis and biomedical research.

Experimental Realization of Fluoroborophene

Borophene, an anisotropic metallic Dirac material exhibits superlative physical and chemical properties. While the lack of bandgap restricts its electronic chip applications, insufficient charge carrier density and electrochemical/catalytically active sites, restricts its energy storage and catalysis applications. Fluorination of borophene can induce bandgap and yield local electron injection within its crystallographic lattice. Herein, a facile synthesis of fluoroborophene with tunable fluorine content through potassium fluoride-assisted solvothermal-sonochemical combinatorial approach is reported. Fluoroborophene monolayers with lateral dimension 50 nm-5 µm are synthesized having controlled fluorine content (12-35%). Fluoroborophene exhibits inter-twinned crystallographic structure, with fluorination-tunable visible-range bandgap ≈1.5-2.5 eV, and density functional theory calculations also corroborate it. Fluoroborophene is explored for electrocatalytic oxygen evolution reaction in an alkaline medium and bestow a good stability. Tunable bandgap, electrophilicity and molecular anchoring capability of fluoroborophene will open opportunities for novel electronic/optoelectronic/spintronic chips, energy storage devices, and in numerous catalytic applications.

2D Materials for Potable Water Application: Basic Nanoarchitectonics and Recent Progresses

Water polluted by toxic chemicals due to waste from chemical/pharmaceuticals and harmful microbes such as E. Coli bacteria causes several fatal diseases; and therefore, water filtration is crucial for accessing clean and safe water necessary for good health. Conventional water filtration technologies include activated carbon filters, reverse osmosis, and ultrafiltration. However, they face several challenges, including high energy consumption, fouling, limited selectivity, inefficiencies in removing certain contaminants, dimensional control of pores, and structural/chemical changes at higher thermal conditions and upon prolonged usage of water filter. Recently, the advent of 2D materials such as graphene, BN, MoS2, MXenes, and so on opens new avenues for advanced water filtration systems. This review delves into the nanoarchitectonics of 2D materials for water filtration applications. The current state of water filtration technologies is explored, the inherent challenges they face are outlines, and the unique properties and advantages of 2D materials are highlighted. Furthermore, the scope of this review is discussed, which encompasses the synthesis, characterization, and application of various 2D materials in water filtration, providing insights into future research directions and potential industrial applications.

Graphene via Microwave Expansion of Graphite Followed by Cryo-Quenching and its Application in Electrostatic Droplet Switching

Monoelemental atomic sheets (Xenes) and other 2D materials offer record electronic mobility, high thermal conductivity, excellent Young's moduli, optical transparency, and flexural capability, revolutionizing ultrasensitive devices and enhancing performance. The ideal synthesis of these quantum materials should be facile, fast, scalable, reproducible, and green. Microwave expansion followed by cryoquenching (MECQ) leverages thermal stress in graphite to produce high-purity graphene within minutes. MECQ synthesis of graphene is reported at 640 and 800 W for 10 min, followed by liquid nitrogen quenching for 5 and 90 min of sonication. Microscopic and spectroscopic analyses confirmed the chemical identity and phase purity of monolayers and few-layered graphene sheets (200-12 µm). Higher microwave power yields thinner layers with enhanced purity. Molecular dynamics simulations and DFT calculations support the exfoliation under these conditions. Electrostatic droplet switching is demonstrated using MECQ-synthesized graphene, observing electrorolling of a mercury droplet on a BN/graphene interface at voltages above 20 V. This technique can inspire the synthesis of other 2D materials with high purity and enable new applications.

Microwave Doping of Sulfur and Iron in β12 Borophene

Borophene, a 2D material exhibiting unique crystallographic phases like the anisotropic atomic lattices of β12 and X3 phases, has attracted considerable attention due to its intriguing Dirac nature and metallic attributes. Despite surpassing graphene in electronic mobility, borophene's potential in energy storage and catalysis remains untapped due to its inherent electrochemical and catalytic limitations. Elemental doping emerges as a promising strategy to introduce charge carriers, enabling localized electrochemical and catalytic functionalities. However, effective doping of borophene has been a complex and underexplored challenge. Here, an innovative, one-pot microwave-assisted doping method, tailored for the β12 phase of borophene is introduced. By subjecting dispersed β12 borophene in dimethylformamide to controlled microwave exposure with sulfur powder and FeCl3 as doping precursors, S- and Fe doping in borophene can be controlled. Employing advanced techniques including high-resolution transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, confirm successful sulfur and iron dopant incorporation onto β12 borophene is confirmed, achieving doping levels of up to 11 % and 13 %, respectively. Remarkably, S- and Fe-doped borophene exhibit exceptional supercapacitive behavior, with specific capacitances of 202 and 120 F g-1, respectively, at a moderate current density of 0.25 A g-1.

The Rise of Xene Hybrids

Xenes, mono-elemental atomic sheets, exhibit Dirac/Dirac-like quantum behavior. When interfaced with other 2D materials such as boron nitride, transition metal dichalcogenides, and metal carbides/nitrides/carbonitrides, it enables them with unique physicochemical properties, including structural stability, desirable bandgap, efficient charge carrier injection, flexibility/breaking stress, thermal conductivity, chemical reactivity, catalytic efficiency, molecular adsorption, and wettability. For example, BN acts as an anti-oxidative shield, MoS2 injects electrons upon laser excitation, and MXene provides mechanical flexibility. Beyond precise compositional modulations, stacking sequences, and inter-layer coupling controlled by parameters, achieving scalability and reproducibility in hybridization is crucial for implementing these quantum materials in consumer applications. However, realizing the full potential of these hybrid materials faces challenges such as air gaps, uneven interfaces, and the formation of defects and functional groups. Advanced synthesis techniques, a deep understanding of quantum behaviors, precise control over interfacial interactions, and awareness of cross-correlations among these factors are essential. Xene-based hybrids show immense promise for groundbreaking applications in quantum computing, flexible electronics, energy storage, and catalysis. In this timely perspective, recent discoveries of novel Xenes and their hybrids are highlighted, emphasizing correlations among synthetic parameters, structure, properties, and applications. It is anticipated that these insights will revolutionize diverse industries and technologies.

Construction of Porphyrin-Based Bimetallic Nanomaterials with Photocatalytic Properties

The efficient synthesis of nanosheets containing two metal ions is currently a formidable challenge. Here, we attempted to dope lanthanide-based bimetals into porphyrin-based metal-organic skeleton materials (MOFs) by microwave-assisted heating. The results of the EDX, ICP, and XPS tests show that we have successfully synthesized porphyrin-based lanthanide bimetallic nanosheets (Tb-Eu-TCPP) using a household microwave oven. In addition, it is tested and experimentally evident that these nanosheets have a thinner thickness, a larger BET surface area, and higher photogenerated carrier separation efficiency than bulk porphyrin-based bimetallic materials, thus exhibiting enhanced photocatalytic activity and n-type semiconductor properties. Furthermore, the prepared Tb-Eu-TCPP nanomaterials are more efficient in generating single-linear state oxygen under visible light irradiation compared to pristine monometallic nanosheets due to the generation of bimetallic nodes. The significant increase in catalytic activity is attributed to the improved separation and transfer efficiency of photogenerated carriers. This study not only deepens our understanding of lanthanide bimetallic nanosheet materials but also introduces an innovative approach to improve the photocatalytic performance of MOFs.

Microwave synthesis of molybdenene from MoS2

Dirac materials are characterized by the emergence of massless quasiparticles in their low-energy excitation spectrum that obey the Dirac Hamiltonian. Known examples of Dirac materials are topological insulators, d-wave superconductors, graphene, and Weyl and Dirac semimetals, representing a striking range of fundamental properties with potential disruptive applications. However, none of the Dirac materials identified so far shows metallic character. Here, we present evidence for the formation of free-standing molybdenene, a two-dimensional material composed of only Mo atoms. Using MoS2 as a precursor, we induced electric-field-assisted molybdenene growth under microwave irradiation. We observe the formation of millimetre-long whiskers following screw-dislocation growth, consisting of weakly bonded molybdenene sheets, which, upon exfoliation, show metallic character, with an electrical conductivity of ~940 S m-1. Molybdenene when hybridized with two-dimensional h-BN or MoS2, fetch tunable optical and electronic properties. As a proof of principle, we also demonstrate applications of molybdenene as a surface-enhanced Raman spectroscopy platform for molecular sensing, as a substrate for electron imaging and as a scanning probe microscope cantilever.

Substrate-Selective Adhesion of Metal Nanoparticles to Graphene Devices

Nanostructured electronic devices, such as those based on graphene, are typically grown on top of the insulator SiO₂. Their exposure to a flux of small size-selected silver nanoparticles has revealed remarkably selective adhesion: the graphene channel can be made fully metallized, while the insulating substrate remains coverage-free. This conspicuous contrast derives from the low binding energy between the metal nanoparticles and a contaminant-free passivated silica surface. In addition to providing physical insight into nanoparticle adhesion, this effect may be of value in applications involving deposition of metallic layers on device working surfaces: it eliminates the need for masking the insulating region and the associated extensive and potentially deleterious pre- and postprocessing.

A Rising 2D Star: Novel MBenes with Excellent Performance in Energy Conversion and Storage

As a flourishing member of the two-dimensional (2D) nanomaterial family, MXenes have shown great potential in various research areas. In recent years, the continued growth of interest in MXene derivatives, 2D transition metal borides (MBenes), has contributed to the emergence of this 2D material as a latecomer. Due to the excellent electrical conductivity, mechanical properties and electrical properties, thus MBenes attract more researchers' interest. Extensive experimental and theoretical studies have shown that they have exciting energy conversion and electrochemical storage potential. However, a comprehensive and systematic review of MBenes applications has not been available so far. For this reason, we present a comprehensive summary of recent advances in MBenes research. We started by summarizing the latest fabrication routes and excellent properties of MBenes. The focus will then turn to their exciting potential for energy storage and conversion. Finally, a brief summary of the challenges and opportunities for MBenes in future practical applications is presented.