Large-area Metrology of CVD-grown Graphene Layers on Copper Foil Substrates

ABSTRACTFluorescence Quenching Microscopy has been shown to be an effective means of characterizing graphene on the macroscale. Centimeter-scale CVD-grown pristine and doped graphene were manufactured in a high temperature (1000°C) furnace on pristine copper substrates. The copper was then etched away in a FeCl3solution and the graphene was coated with DCM-based fluorescent dye before being imaged in a fluorescence microscope. The fluorescence image was then image-processed using modified Matlab software. The resulting image showed clear contrast between the pristine graphene sheet and defects on the graphene surface, which revealed that fluorescence microscopy could determine the quality of a large region of graphene. Also, significant contrast was identified between single-layer and multi-layer regions, showing that this technique is also effective at determining the degree of uniformity within a graphene sample. Lastly, the fluorescence images showed contrast between doped and undoped regions of graphene.

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Low-Temperature Chemical Vapor Deposition Growth of Graphene Layers on Copper Substrate Using Camphor Precursor

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2020.18862 ◽

2020 ◽

Vol 20 (12) ◽

pp. 7698-7704

Author(s):

K. Kavitha ◽

Akanksha R. Urade ◽

Gurjinder Kaur ◽

Indranil Lahiri

Keyword(s):

Chemical Vapor Deposition ◽

Low Temperature ◽

Vapor Deposition ◽

Graphene Layer ◽

Copper Substrate ◽

Chemical Vapor ◽

Large Area ◽

Chemical Vapor Deposition Growth ◽

Graphene Layers ◽

Grown Graphene

A two-step, low-temperature thermal chemical vapor deposition (CVD) process, which uses camphor for synthesizing continuous graphene layer on Cu substrate is reported. The growth process was performed at lower temperature (800 °C) using camphor as the source of carbon. A threezone CVD system was used for controlled heating of precursor, in order to obtain uniform graphene layer. As-grown samples were characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). The results show the presence of 4–5 layers of graphene. As-grown graphene transferred onto a glass substrate through a polymer-free wet-etching process, demonstrated transmittance ~91% in visible spectra. This process of synthesizing large area, 4–5 layer graphene at reduced temperature represents an energy-efficient method of producing graphene for possible applications in opto-electronic industry.

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Effect of nitrogen doping of graphene nanoflakes on their efficiency in supercapacitor applications

Functional Materials Letters ◽

10.1142/s1793604718400052 ◽

2018 ◽

Vol 11 (06) ◽

pp. 1840005 ◽

Cited By ~ 17

Author(s):

Ekaterina A. Arkhipova ◽

Anton S. Ivanov ◽

Serguei V. Savilov ◽

Konstantin I. Maslakov ◽

Sergei A. Chernyak ◽

...

Keyword(s):

Electrode Material ◽

Nitrogen Doping ◽

Pristine Graphene ◽

Graphene Layers ◽

Nitrogen Doped ◽

Graphene Nanoflakes ◽

Nitrogen Doped Graphene ◽

Doped Graphene ◽

Electrochemical Double Layer ◽

Supercapacitor Applications

Pristine graphene nanoflakes (GNFs) and those doped with nitrogen up to a level of 10.9[Formula: see text]at.% were tested as an electrode material for electrochemical double-layer supercapacitor. Doping with nitrogen increased the specific capacitance of GNFs from 88 to 180[Formula: see text]F/g. The increase results from the enhanced interaction of nitrogen-doped graphene layers with electrolyte ions.

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Thermoresistive Properties of Graphite Platelet Films Supported by Different Substrates

Materials ◽

10.3390/ma12213638 ◽

2019 ◽

Vol 12 (21) ◽

pp. 3638 ◽

Cited By ~ 3

Author(s):

Mariano Palomba ◽

Gianfranco Carotenuto ◽

Angela Longo ◽

Andrea Sorrentino ◽

Antonio Di Bartolomeo ◽

...

Keyword(s):

Large Area ◽

Transmission Electron Microscopy Analysis ◽

Graphene Layers ◽

Glass Substrates ◽

Thermal Expansion Coefficients ◽

Transmission Electron ◽

Electron Microscopy Analysis ◽

Microscopy Analysis ◽

Interfacial Plane

Large-area graphitic films, produced by an advantageous technique based on spraying a graphite lacquer on glass and low-density polyethylene (LDPE) substrates were studied for their thermoresistive applications. The spray technique uniformly covered the surface of the substrate by graphite platelet (GP) unities, which have a tendency to align parallel to the interfacial plane. Transmission electron microscopy analysis showed that the deposited films were composed of overlapped graphite platelets of different thickness, ranging from a few tens to hundreds of graphene layers, and Raman measurements provided evidence for a good graphitic quality of the material. The GP films deposited on glass and LDPE substrates exhibited different thermoresistive properties during cooling–heating cycles in the −40 to +40 °C range. Indeed, negative values of the temperature coefficient of resistance, ranging from −4 × 10−4 to −7 × 10−4 °C−1 have been observed on glass substrates, while positive values varying between 4 × 10−3 and 8 × 10−3 °C−1 were measured when the films were supported by LDPE. These behaviors were attributed to the different thermal expansion coefficients of the substrates. The appreciable thermoresistive properties of the graphite platelet films on LDPE could be useful for plastic electronic applications.

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Convergent Beam Electron Diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070072 ◽

1978 ◽

Vol 36 (3) ◽

pp. 304-315

Author(s):

G. Lehmpfuhl

Keyword(s):

Electron Diffraction ◽

Diffraction Pattern ◽

Crystal Surface ◽

Diffraction Spot ◽

Crystal Thickness ◽

Large Area ◽

Electron Microscopic ◽

Additional Information ◽

Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

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Making Graphene-type Material via Polymerization of Porphyrin

10.26434/chemrxiv.13041785.v1 ◽

2020 ◽

Author(s):

SANJIB KAR ◽

Sruti Mondal ◽

Kasturi Sahu ◽

Dilruba Hasina ◽

Tapobrata Som ◽

...

Keyword(s):

Layer Thickness ◽

Polymeric Material ◽

Single Layer ◽

Type Material ◽

Synthetic Pathway ◽

Simple Chemical ◽

Doped Graphene ◽

Ring Nitrogen ◽

2D Structure ◽

Porphyrin Macrocycles

The synthesis of new graphene-type materials (via polymerization of porphyrin macrocycles) through a simple chemical synthetic pathway (at RT) has been demonstrated. This newly synthesized material can be dispersed in water with an average sheet size of few microns and with single layer thickness. As the porphyrin contains four inner ring nitrogen atoms thus the presented polymeric material will be close analogous of N-doped graphene. Porphyrin as the key component to synthesize layered graphene type continuous 2D structure has never been attempted before.

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N-doped graphene foam obtained by microwave-assisted exfoliation of graphite

Scientific Reports ◽

10.1038/s41598-021-81769-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Malgorzata Skorupska ◽

Anna Ilnicka ◽

Jerzy P. Lukaszewicz

Keyword(s):

Electron Microscopy ◽

Electrode Materials ◽

Elemental Content ◽

Research Approach ◽

Pristine Graphene ◽

Active Electrode ◽

Graphene Foam ◽

Practical Applications ◽

Microwave Reactor ◽

Doped Graphene

AbstractThe synthesis of metal-free but electrochemically active electrode materials, which could be an important contributor to environmental protection, is the key motivation for this research approach. The progress of graphene material science in recent decades has contributed to the further development of nanotechnology and material engineering. Due to the unique properties of graphene materials, they have found many practical applications: among others, as catalysts in metal-air batteries, supercapacitors, or fuel cells. In order to create an economical and efficient material for energy production and storage applications, researchers focused on the introduction of additional heteroatoms to the graphene structure. As solutions for functionalizing pristine graphene structures are very difficult to implement, this article presents a facile method of preparing nitrogen-doped graphene foam in a microwave reactor. The influence of solvent type and microwave reactor holding time was investigated. To characterize the elemental content and structural properties of the obtained N-doped graphene materials, methods such as elemental analysis, high-resolution transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy were used. Electrochemical activity in ORR of the obtained materials was tested using cyclic voltamperometry (CV) and linear sweep voltamperometry (LSV). The tests proved the materials’ high activity towards ORR, with the number of electrons reaching 3.46 for tested non-Pt materials, while the analogous value for the C-Pt (20 wt% loading) reference was 4.

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Mastering of NIL Stamps with Undercut T-Shaped Features from Single Layer to Multilayer Stamps

Nanomaterials ◽

10.3390/nano11040956 ◽

2021 ◽

Vol 11 (4) ◽

pp. 956

Author(s):

Philipp Taus ◽

Adrian Prinz ◽

Heinz D. Wanzenboeck ◽

Patrick Schuller ◽

Anton Tsenov ◽

...

Keyword(s):

Electron Beam Lithography ◽

Nanoimprint Lithography ◽

Silicon Oxide ◽

Three Dimensional ◽

Single Layer ◽

Fabrication Technology ◽

Large Area ◽

Structural Colors ◽

Biomimetic Structures ◽

Morpho Butterfly

Biomimetic structures such as structural colors demand a fabrication technology of complex three-dimensional nanostructures on large areas. Nanoimprint lithography (NIL) is capable of large area replication of three-dimensional structures, but the master stamp fabrication is often a bottleneck. We have demonstrated different approaches allowing for the generation of sophisticated undercut T-shaped masters for NIL replication. With a layer-stack of phase transition material (PTM) on poly-Si, we have demonstrated the successful fabrication of a single layer undercut T-shaped structure. With a multilayer-stack of silicon oxide on silicon, we have shown the successful fabrication of a multilayer undercut T-shaped structures. For patterning optical lithography, electron beam lithography and nanoimprint lithography have been compared and have yielded structures from 10 µm down to 300 nm. The multilayer undercut T-shaped structures closely resemble the geometry of the surface of a Morpho butterfly, and may be used in future to replicate structural colors on artificial surfaces.

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Chlorosulfuric acid-assisted production of functional 2D materials

npj 2D Materials and Applications ◽

10.1038/s41699-021-00215-2 ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Mohsen Moazzami Gudarzi ◽

Maryana Asaad ◽

Boyang Mao ◽

Gergo Pinter ◽

Jianqiang Guo ◽

...

Keyword(s):

Hexagonal Boron Nitride ◽

2D Materials ◽

Real Life ◽

Large Area ◽

Polar Solvents ◽

Aspect Ratios ◽

Two Dimensional Materials ◽

Liquid Phase Exfoliation

AbstractThe use of two-dimensional materials in bulk functional applications requires the ability to fabricate defect-free 2D sheets with large aspect ratios. Despite huge research efforts, current bulk exfoliation methods require a compromise between the quality of the final flakes and their lateral size, restricting the effectiveness of the product. In this work, we describe an intercalation-assisted exfoliation route, which allows the production of high-quality graphene, hexagonal boron nitride, and molybdenum disulfide 2D sheets with average aspect ratios 30 times larger than that obtained via conventional liquid-phase exfoliation. The combination of chlorosulfuric acid intercalation with in situ pyrene sulfonate functionalisation produces a suspension of thin large-area flakes, which are stable in various polar solvents. The described method is simple and requires no special laboratory conditions. We demonstrate that these suspensions can be used for fabrication of laminates and coatings with electrical properties suitable for a number of real-life applications.

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Multi-Task Optimization and Multi-Task Evolutionary Computation in the Past Five Years: A Brief Review

Mathematics ◽

10.3390/math9080864 ◽

2021 ◽

Vol 9 (8) ◽

pp. 864

Author(s):

Qingzheng Xu ◽

Na Wang ◽

Lei Wang ◽

Wei Li ◽

Qian Sun

Keyword(s):

Evolutionary Computation ◽

Explicit Knowledge ◽

Optimization Problems ◽

Effective Means ◽

Typical Application ◽

The Past ◽

Current State ◽

Evolution Algorithms ◽

Application Fields

Traditional evolution algorithms tend to start the search from scratch. However, real-world problems seldom exist in isolation and humans effectively manage and execute multiple tasks at the same time. Inspired by this concept, the paradigm of multi-task evolutionary computation (MTEC) has recently emerged as an effective means of facilitating implicit or explicit knowledge transfer across optimization tasks, thereby potentially accelerating convergence and improving the quality of solutions for multi-task optimization problems. An increasing number of works have thus been proposed since 2016. The authors collect the abundant specialized literature related to this novel optimization paradigm that was published in the past five years. The quantity of papers, the nationality of authors, and the important professional publications are analyzed by a statistical method. As a survey on state-of-the-art of research on this topic, this review article covers basic concepts, theoretical foundation, basic implementation approaches of MTEC, related extension issues of MTEC, and typical application fields in science and engineering. In particular, several approaches of chromosome encoding and decoding, intro-population reproduction, inter-population reproduction, and evaluation and selection are reviewed when developing an effective MTEC algorithm. A number of open challenges to date, along with promising directions that can be undertaken to help move it forward in the future, are also discussed according to the current state. The principal purpose is to provide a comprehensive review and examination of MTEC for researchers in this community, as well as promote more practitioners working in the related fields to be involved in this fascinating territory.

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Tuning the electrical properties of exfoliated graphene layers using deep ultraviolet irradiation

Journal of Materials Chemistry C ◽

10.1039/c4tc00522h ◽

2014 ◽

Vol 2 (27) ◽

pp. 5404-5410 ◽

Cited By ~ 30

Author(s):

M. Z. Iqbal ◽

M. F. Khan ◽

M. W. Iqbal ◽

Jonghwa Eom

Keyword(s):

Electrical Properties ◽

Ultraviolet Irradiation ◽

Single Layer ◽

Single Layer Graphene ◽

Graphene Bilayer ◽

Graphene Layers ◽

Exfoliated Graphene ◽

Deep Ultraviolet ◽

Trilayer Graphene ◽

Unique Band

Deep ultraviolet irradiation tunes the electronic properties of mechanically exfoliated single-layer graphene, bilayer graphene, and trilayer graphene while maintaining their unique band structure and electrical properties.

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