Preparation Of 2D Materials Research Articles

Exploring advanced microwave strategy for the synthesis of two-dimensional energy materials

The rapid pace of technology and increasing energy demands underscore the urgent need for eco-friendly materials with exceptional energy conversion and storage capabilities. Two-dimensional (2D) energy materials, characterized by unique physicochemical properties, hold great promise in renewable energy conversion, catalysis, and electronics. Nevertheless, conventional synthesis methods often falter in balancing high quality, high yield, and cost-effectiveness, presenting substantial obstacles to their large-scale application. Microwave-assisted synthesis, characterized by its rapid and efficient process, emerges as a promising approach to surmount these limitations. This review meticulously examines the pivotal role of microwave-assisted synthesis in the preparation of 2D materials, highlighting its profound impact on enhancing material quality and production efficiency. By scrutinizing the unique physical properties of microwaves and their applications in material synthesis, the review elucidates the innovative contributions of microwave technology to materials science. Furthermore, it delves into the intricate influence of microwave parameter control on the synthesis process and resultant material properties, offering insight into the potential of microwave technology for the precise modulation of material structure and functionality. This comprehensive analysis underscores microwave-assisted synthesis as a viable solution for overcoming current challenges, thereby advancing the development of high-performance 2D energy materials.

Preparation of 2D Materials and Their Application in Oil–Water Separation

The problems of environmental pollution are increasingly severe. Among them, industrial wastewater is one of the primary sources of pollution, so it is essential to deal with wastewater, especially oil and water mixtures. At present, biomimetic materials with special wettability have been proven to be effective in oil-water separation. Compared with three-dimensional (3D) materials, two-dimensional (2D) materials show unique advantages in the preparation of special wettable materials due to their high specific surface area, high porosity, controlled structure, and rich functional group rich on the surface. In this review, we first introduce oil-water mixtures and the common oil-water separation mechanism. Then, the research progress of 2D materials in oil-water separation is presented, including but not limited to their structure, types, preparation principles, and methods. In addition, it is still impossible to prepare 2D materials with large sizes because they are powder-like, which greatly limits the application in oil-water separation. Therefore, we provide here a review of several ways to transform 2D materials into 3D materials. In the end, the challenges encountered by 2D materials in separating oil-water are also clarified to promote future applications.

Machine Learning-Assisted Synthesis of Two-Dimensional Materials.

Two-dimensional (2D) materials have intriguing physical and chemical properties, which exhibit promising applications in the fields of electronics, optoelectronics, as well as energy storage. However, the controllable synthesis of 2D materials is highly desirable but remains challenging. Machine learning (ML) facilitates the development of insights and discoveries from a large amount of data in a short time for the materials synthesis, which can significantly reduce the computational costs and shorten the development cycles. Based on this, taking the 2D material MoS2 as an example, the parameters of successfully synthesized materials by chemical vapor deposition (CVD) were explored through four ML algorithms: XGBoost, Support Vector Machine (SVM), Naïve Bayes (NB), and Multilayer Perceptron (MLP). Recall, specificity, accuracy, and other metrics were used to assess the performance of these four models. By comparison, XGBoost was the best performing model among all the models, with an average prediction accuracy of over 88% and a high area under the receiver operating characteristic (AUROC) reaching 0.91. And these findings showed that the reaction temperature (T) had a crucial influence on the growth of MoS2. Furthermore, the importance of the features in the growth mechanism of MoS2 was optimized, such as the reaction temperature (T), Ar gas flow rate (Rf), reaction time (t), and so on. The results demonstrated that ML assisted materials preparation can significantly minimize the time spent on exploration and trial-and-error, which provided perspectives in the preparation of 2D materials.

Can fluorophlogopite mica be used as an alkali metal ion source to boost the growth of two-dimensional molybdenum dioxide?

Everyone familiar with two-dimensional (2D) materials is aware of fluorophlogopite mica (FM), which has an atomic-level flat surface that provides an ideal platform for the growth of 2D materials. Since it has been demonstrated that the alkali metal ions (AMI) can aid in the growth of large-sized 2D materials by chemical vapor deposition (CVD) in recent years, it became a major mystery whether FM which contains AMI benefits from them in the preparation of 2D materials by CVD, too. In this article, we dispelled this ambiguity and discovered that temperature is the key for FM as an AMI source to boost the growth of large-sized 2D materials. We carried out variable temperature experiments and found that FM can indeed be incorporated into the growth of large-sized 2D materials as an AMI source at high temperatures and successfully obtained the highly crystalline MoO2 with a larger size compared to those without FM. This finding is of great importance to the understanding of the growth mechanism of FM for 2D materials by CVD and to better exploit its role in the growth of 2D materials.

Photoexfoliation Synthesis of 2D Materials

Quantum two-dimensional (2D) materials discovered in the early 21st century have outsmarted existing nanomaterials in various frontiers of applications. Among the preparation of 2D materials, molecular beam epitaxy, atomic layer deposition, and chemical vapor deposition are nonscalable costly methods, whereas sonochemical and Hummer’s exfoliation methods provide functionalized sheets. Conversely, ultrafast liquid-phase laser processing promises quick delivery of defect-free 2D quantum materials. We report photoexfoliation synthesis of atomic graphene layers, boron nitride (BN), and molybdenum disulfide (MoS2) by the intense KrF laser irradiation into aqueous dispersions of parent material powders in DMF taken in quartz beakers. The number of atomic layers and the lateral size of the sheets gradually decrease with an increase in the laser irradiation duration. Also, the laser fluence becomes the critical control parameter of the lateral size and the number of layers. The average lateral size shrinks from ∼400 nm at 1.5 J/cm2 to 20–30 nm at 4 J/cm2, which accompanies a surge in the ratio of sheets with fewer layers. We correlate the laser processing parameters with the sample size and analyze the molecule-atom-scale interactions. Simulation and DFT calculations suggest the mild out-of-plane thermal expansion of atomic layers followed by solvent intercalation stretches interlayer distance to ∼6.68 Å and thereby lowers the activation energy of exfoliation. The optimum photon fluence at the solvent-assisted condition reduces the activation barrier, enabling us to synthesize 2D crystals in the solution phase. Photoexfoliation synthesis of pure crystals of 2D materials can be promising for next-generation electronic devices.

Laser assisted synthesis of WS2 nanorods by pulsed laser ablation in liquid environment

Two dimensional (2D) materials are widely attracting the interest of researchers due to their unique crystal structure and diverse properties. In the present work, tungsten disulfide (WS[Formula: see text] nanorods were synthesized by a simple method of pulsed laser ablation in liquid (PLAL) environment. The prepared WS2 are analyzed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and Raman spectroscopy to confirm the surface morphology, phase and structure. A possible growth mechanism of WS2 is proposed. This study indicates new door for the preparation of 2D materials with specific morphology.

In Situ and Operando Characterizations of 2D Materials in Electrochemical Energy Storage Devices

In-Situ/Operando Characterization of 2D Materials The recent advances of in-situ and operando characterization of 2D materials for electrochemical energy storage devices are reviewed in the article number 2000076 by Qiang Fu, Klaus Müllen, Zhong-Shuai Wu, and co-workers to comprehensively understand the charge storage and degradation mechanisms. Preparation of 2D materials and the impact of preparation methods on the resulting electrode structure and electrochemical performance, and the mechanisms underlying the operation of supercapacitors and lithium batteries are discussed.

An In Situ Reflectance Spectroscopic Investigation to Monitor Two-Dimensional MoS2 Flakes on a Sapphire Substrate.

In this work, we demonstrate the application of differential reflectance spectroscopy (DRS) to monitor the growth of molybdenum disulfide (MoS2) using chemical vapor deposition (CVD). The growth process, optical properties, and structure evolution of MoS2 were recorded by in-situ DRS. Indeed, blue shifts of the characteristic peak B were discussed with the decrease of temperature. We also obtained the imaginary part of the MoS2 dielectric constant according to reflectance spectra. This method provides an approach for studying the change of two-dimensional (2D) materials’ dielectric constant with temperature. More importantly, our work emphasizes that the DRS technique is a non-destructive and effective method for in-situ monitoring the growth of 2D materials, which is helpful in guiding the preparation of 2D materials.