12 results
Search Results
Now showing 1 - 10 of 12
- ItemIn Situ Fabrication of Freestanding Single-Atom-Thick 2D Metal/Metallene and 2D Metal/ Metallene Oxide Membranes: Recent Developments(Weinheim : Wiley-VCH, 2021) Ta, Huy Q.; Mendes, Rafael G.; Liu, Yu; Yang, Xiaoqin; Luo, Jingping; Bachmatiuk, Alicja; Gemming, Thomas; Zeng, Mengqi; Fu, Lei; Liu, Lijun; Rümmeli, Mark H.In recent years, two-dimensional (2D) materials have attracted a lot of research interest as they exhibit several fascinating properties. However, outside of 2D materials derived from van der Waals layered bulk materials only a few other such materials are realized, and it remains difficult to confirm their 2D freestanding structure. Despite that, many metals are predicted to exist as 2D systems. In this review, the authors summarize the recent progress made in the synthesis and characterization of these 2D metals, so called metallenes, and their oxide forms, metallene oxides as free standing 2D structures formed in situ through the use of transmission electron microscopy (TEM) and scanning TEM (STEM) to synthesize these materials. Two primary approaches for forming freestanding monoatomic metallic membranes are identified. In the first, graphene pores as a means to suspend the metallene or metallene oxide and in the second, electron-beam sputtering for the selective etching of metal alloys or thick complex initial materials is employed to obtain freestanding single-atom-thick 2D metal. The data show a growing number of 2D metals/metallenes and 2D metal/ metallene oxides having been confirmed and point to a bright future for further discoveries of these 2D materials.
- ItemAdvances and Trends in Chemically Doped Graphene(Weinheim : Wiley-VCH, 2020) Ullah, Sami; Shi, Qitao; Zhou, Junhua; Yang, Xiaoqin; Ta, Huy Q.; Hasan, Maria; Ahmad, Nasir Mahmood; Fu, Lei; Bachmatiuk, Alicja; Rümmeli, Mark H.Chemically doped graphene materials are fascinating because these have different desirable attributes with possible synergy. The inert and gapless nature of graphene can be changed by adding a small number of heteroatoms to substitute carbon in the lattice. The doped material may display superior catalytic activities; durable, fast, and selective sensing; improved magnetic moments; photoresponses; and activity in chemical reactions. In the current review, recent advances are covered in chemically doped graphene. First, the different types of heteroatoms, their bonding configurations, and briefly their properties are discussed. This is followed by the description of various synthesis and analytical methods essential for assessing the characteristics of heterographene with specific focus on the selected graphene materials of different dopants (particularly, single dopants, including N, B, S, P, first three halogens, Ge, and Ga, and codopants, such as N/O), and more importantly, up-to-date applications enabled by the intentional doping. Finally, outlook and perspectives section review the existing challenges, future opportunities, and possible ways to improve the graphitic materials. The goal is to update and inspire the readers to establish novel doped graphene with valuable properties and for current and futuristic applications. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemOn the Catalytic Activity of Sn Monomers and Dimers at Graphene Edges and the Synchronized Edge Dependence of Diffusing Atoms in Sn Dimers(Weinheim : Wiley-VCH, 2021) Yang, Xiaoqin; Ta, Huy Q.; Hu, Huimin; Liu, Shuyuan; Liu, Yu; Bachmatiuk, Alicja; Luo, Jinping; Liu, Lijun; Choi, Jin-Ho; Rummeli, Mark H.In this study, in situ transmission electron microscopy is performed to study the interaction between single (monomer) and paired (dimer) Sn atoms at graphene edges. The results reveal that a single Sn atom can catalyze both the growth and etching of graphene by the addition and removal of C atoms respectively. Additionally, the frequencies of the energetically favorable configurations of an Sn atom at a graphene edge, calculated using density functional theory calculations, are compared with experimental observations and are found to be in good agreement. The remarkable dynamic processes of binary atoms (dimers) are also investigated and is the first such study to the best of the knowledge. Dimer diffusion along the graphene edges depends on the graphene edge termination. Atom pairs (dimers) involving an armchair configuration tend to diffuse with a synchronized shuffling (step-wise shift) action, while dimer diffusion at zigzag edge terminations show a strong propensity to collapse the dimer with each atom diffusing in opposite directions (monomer formation). Moreover, the data reveals the role of C feedstock availability on the choice a single Sn atom makes in terms of graphene growth or etching. This study advances the understanding single atom catalytic activity at graphene edges. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH
- ItemGraphene-Like ZnO: A Mini Review(Basel : MDPI, 2016) Ta, Huy Q.; Zhao, Liang; Pohl, Darius; Pang, Jinbo; Trzebicka, Barbara; Rellinghaus, Bernd; Pribat, Didier; Gemming, Thomas; Liu, Zhongfan; Bachmatiuk, Alicja; Rümmeli, Mark H.The isolation of a single layer of graphite, known today as graphene, not only demonstrated amazing new properties but also paved the way for a new class of materials often referred to as two-dimensional (2D) materials. Beyond graphene, other 2D materials include h-BN, transition metal dichalcogenides (TMDs), silicene, and germanene, to name a few. All tend to have exciting physical and chemical properties which appear due to dimensionality effects and modulation of their band structure. A more recent member of the 2D family is graphene-like zinc oxide (g-ZnO) which also holds great promise as a future functional material. This review examines current progress in the synthesis and characterization of g-ZnO. In addition, an overview of works dealing with the properties of g-ZnO both in its pristine form and modified forms (e.g., nano-ribbon, doped material, etc.) is presented. Finally, discussions/studies on the potential applications of g-ZnO are reviewed and discussed.
- ItemGraphene transfer methods: A review(New York, NY [u.a.] : Springer, 2021) Ullah, Sami; Yang, Xiaoqin; Ta, Huy Q.; Hasan, Maria; Bachmatiuk, Alicja; Tokarska, Klaudia; Trzebicka, Barbara; Fu, Lei; Rummeli, Mark H.Graphene is a material with unique properties that can be exploited in electronics, catalysis, energy, and bio-related fields. Although, for maximal utilization of this material, high-quality graphene is required at both the growth process and after transfer of the graphene film to the application-compatible substrate. Chemical vapor deposition (CVD) is an important method for growing high-quality graphene on non-technological substrates (as, metal substrates, e.g., copper foil). Thus, there are also considerable efforts toward the efficient and non-damaging transfer of quality of graphene on to technologically relevant materials and systems. In this review article, a range of graphene current transfer techniques are reviewed from the standpoint of their impact on contamination control and structural integrity preservation of the as-produced graphene. In addition, their scalability, cost- and time-effectiveness are discussed. We summarize with a perspective on the transfer challenges, alternative options and future developments toward graphene technology.
- ItemIn Situ Room Temperature Electron-Beam Driven Graphene Growth from Hydrocarbon Contamination in a Transmission Electron Microscope(Basel : MDPI, 2018-5-26) Rummeli, Mark H.; Pan, Yumo; Zhao, Liang; Gao, Jing; Ta, Huy Q.; Martinez, Ignacio G.; Mendes, Rafael G.; Gemming, Thomas; Fu, Lei; Bachmatiuk, Alicja; Liu, ZhongfanThe excitement of graphene (as well as 2D materials in general) has generated numerous procedures for the fabrication of graphene. Here we present a mini-review on a rather less known, but attractive, in situ means to fabricate graphene inside a transmission electron microscope (TEM). This is achieved in a conventional TEM (viz. no sophisticated specimen holders or microscopes are required) and takes advantage of inherent hydrocarbon contamination as a carbon source. Both catalyst free and single atom catalyst approaches are reviewed. An advantage of this technique is that not only can the growth process be imaged in situ, but this can also be achieved with atomic resolution. Moreover, in the future, one can anticipate such approaches enabling the growth of nano-materials with atomic precision.
- ItemTailoring the stoichiometry of C3N4 nanosheets under electron beam irradiation(Cambridge : RSC Publ., 2021) Mendes, Rafael G.; Ta, Huy Q.; Yang, Xiaoqin; Bachmatiuk, Alicja; Praus, Petr; Mamakhel, Aref; Iversen, Bo B.; Su, Ren; Gemming, Thomas; Rümmeli, Mark H.Two-dimensional polymeric graphitic carbon nitride (g-C3N4) is a low-cost material with versatile properties that can be enhanced by the introduction of dopant atoms and by changing the degree of polymerization/stoichiometry, which offers significant benefits for numerous applications. Herein, we investigate the stability of g-C3N4 under electron beam irradiation inside a transmission electron microscope operating at different electron acceleration voltages. Our findings indicate that the degradation of g-C3N4 occurs with N species preferentially removed over C species. However, the precise nitrogen group from which N is removed from g-C3N4 (C–N–C, [double bond, length as m-dash]NH or –NH2) is unclear. Moreover, the rate of degradation increases with decreasing electron acceleration voltage, suggesting that inelastic scattering events (radiolysis) dominate over elastic events (knock-on damage). The rate of degradation by removing N atoms is also sensitive to the current density. Hence, we demonstrate that both the electron acceleration voltage and the current density are parameters with which one can use to control the stoichiometry. Moreover, as N species were preferentially removed, the d-spacing of the carbon nitride structure increased. These findings provide a deeper understanding of g-C3N4.
- ItemCrystal structure, synthesis and characterization of different chromium-based two-dimensional compounds(Riyadh : Saudi Chemical Soc., 2023) Hasan, Maria; Ta, Huy Q.; Ullah, Sami; Yang, Xiaoqin; Luo, Jingping; Bachmatiuk, Alicja; Gemming, Thomas; Trzebicka, Barbara; Mahmood, Azhar; Zeng, Mengqi; Fu, Lei; Liu, Lijun; Rümmeli, Mark H.The field of two dimensional (2D) materials experienced a surge of discoveries after the isolation of graphene. Among these, the transition metal compounds of Molybdenum and tungsten have been the most extensively studied materials after graphene. More recently, their group member chromium has only recently come to the limelight after the discovery of its exciting magnetic properties. As such the body of work surrounding 2D chromium-based materials is growing. Here, we present an up-to-date summary of the chromium 2D materials showing the latest advances in their experimental synthesis, characterization and the applications of 2D Chromium-based compounds. Finally, we conclude with a perspective on the future of 2D chromium-based materials. We believe that this study will be helpful to understand the field of chromium-based 2D compounds.
- ItemIn Situ Observations of Freestanding Single-Atom-Thick Gold Nanoribbons Suspended in Graphene(Weinheim : Wiley-VCH, 2020) Zhao, Liang; Ta, Huy Q.; Mendes, Rafael G.; Bachmatiuk, Alicja; Rummeli, Mark H.Bulk gold's attributes of relative chemical inertness, rarity, relatively low melting point and its beautiful sheen make it a prized material for humans. Recordings suggest it was the first metal employed by humans dating as far back to the late Paleolithic period ≈40 000 BC. However, at the nanoscale gold is expected to present new and exciting properties, not least in catalysis. Moreover, recent studies suggest a new family of single-atom-thick two-dimensional (2D) metals exist. This work shows single-atom-thick freestanding gold membranes and nanoribbons can form as suspended structures in graphene pores. Electron irradiation is shown to lead to changes to the graphene pores which lead to dynamic changes of the gold membranes which transition to a nanoribbon. The freestanding single-atom-thick 2D gold structures are relatively stable to electron irradiation for extended periods. The work should advance the development of 2D gold monolayers significantly. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemSynthesis of Doped Porous 3D Graphene Structures by Chemical Vapor Deposition and Its Applications(Weinheim : Wiley-VCH, 2019) Ullah, Sami; Hasan, Maria; Ta, Huy Q.; Zhao, Liang; Shi, Qitao; Fu, Lei; Choi, Jinho; Yang, Ruizhi; Liu, Zhongfan; Rümmeli, Mark H.Graphene doping principally commenced to compensate for its inert nature and create an appropriate bandgap. Doping of 3D graphene has emerged as a topic of interest because of attempts to combine its large available surface area—arising from its interconnected porous architecture—with superior catalytic, structural, chemical, and biocompatible characteristics that can be induced by doping. In light of the latest developments, this review provides an overview of the scalable chemical vapor deposition (CVD)-based growth of doped 3D graphene materials as well as their applications in various contexts, such as in devices used for energy generation and gas storage and biosensors. In particular, single- and multielement doping of 3D graphene by various dopants (such as nitrogen (N), boron (B), sulfur (S) and phosphorous (P)), the doping configurations of the resultant materials, an overview of recent developments in the field of CVD, and the influence of various parameters of CVD on graphene doping and 3D morphologies are focused in this paper. Finally, this report concludes the discussion by mentioning the existing challenges and future opportunities of these developing graphitic materials, intending to inspire the unveiling of more exciting functionalized 3D graphene morphologies and their potential properties, which can hopefully realize many possible applications. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim