scholarly journals Structural Investigation of the Synthesized Few-Layer Graphene from Coal under Microwave

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 57
Author(s):  
Faridul Islam ◽  
Arash Tahmasebi ◽  
Behdad Moghtaderi ◽  
Jianglong Yu
Keyword(s):  
Potassium Hydroxide ◽  
Bituminous Coal ◽  
Structural Investigation ◽  
The Other ◽  
Activation Process ◽  
Thin Sheets ◽  
Layer Graphene ◽  
Wide Range ◽  
Few Layer Graphene ◽  
Microwave Heat

This study focused on the structural investigation of few-layer graphene (FLG) synthesis from bituminous coal through a catalytic process under microwave heat treatment (MW). The produced FLG has been examined by Raman spectroscopy, XRD, TEM, and AFM. Coal was activated using the potassium hydroxide activation process. The FLG synthesis processing duration was much faster requiring only 20 min under the microwave radiation. To analyse few-layer graphene samples, we considered the three bands, i.e., D, G, and 2D, of Raman spectra. At 1300 °C, the P10% Fe sample resulted in fewer defects than the other catalyst percentages sample. The catalyst percentages affected the structural change of the FLG composite materials. In addition, the Raman mapping showed that the catalyst loaded sample was homogeneously distributed and indicated a few-layer graphene sheet. In addition, the AFM technique measured the FLG thickness around 4.5 nm. Furthermore, the HRTEM images of the P10% Fe sample contained a unique morphology with 2–7 graphitic layers of graphene thin sheets. This research reported the structural revolution with latent feasibility of FLG synthesis from bituminous coal in a wide range.

Facile synthesis of few layer graphene from bituminous coal and its application towards electrochemical sensing of caffeine

2017 ◽  
Vol 8 (3) ◽  
pp. 239-245 ◽  
Author(s):  
E. Senthil Kumar ◽  
V. Sivasankar ◽  
R. Sureshbabu ◽  
S. Raghu ◽  
R. A. Kalaivani
Keyword(s):  
Bituminous Coal ◽  
Electrochemical Sensing ◽  
Facile Synthesis ◽  
Layer Graphene ◽  
Few Layer Graphene

scholarly journals Multi-Layer Graphene Oxide in Human Keratinocytes: Time-Dependent Cytotoxicity, Proliferation, and Gene Expression

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 414
Author(s):  
Beatriz Salesa ◽  
Ángel Serrano-Aroca
Keyword(s):  
Graphene Oxide ◽  
Human Keratinocytes ◽  
Control Group ◽  
Hacat Cells ◽  
Layer Graphene ◽  
Wide Range ◽  
Epidermal Growth ◽  
Biomedical Field ◽  
Few Layer Graphene ◽  
Median Effective Concentration

Few-layer graphene oxide (GO) has shown no or very weak cytotoxicity and anti-proliferative effects in a wide range of cell lines, such as glioma cells and human skin HaCaT cells at concentrations up to 100 µg/mL. However, as multi-layer GO has hardly been explored in the biomedical field, in this study, this other type of GO was examined in human keratinocyte HaCaT cells treated with different concentrations, ranging from 0.01 to 150 µg/mL, for different periods of time (3, 12, and 24 h). The results revealed a time–concentration dependence with two non-cytotoxic concentrations (0.01 and 0.05 µg/mL) and a median effective concentration value of 4.087 µg/mL at 24 h GO exposure. Contrary to what has previously been reported for few-layer GO, cell proliferation of the HaCaT cells in contact with the multi-layer GO at 0.01 μg/mL showed identical proliferative activity to an epidermal growth factor (1.6-fold greater than the control group) after 96 h. The effects of the multi-layer GO on the expression of 13 genes (SOD1, CAT, MMP1, TGFB1, GPX1, FN1, HAS2, LAMB1, LUM, CDH1, COL4A1, FBN, and VCAN) at non-cytotoxic concentrations of GO in the HaCaT cells were analyzed after 24 h. The lowest non-cytotoxic GO concentration was able to upregulate the CAT, TGFB1, FN1, and CDH1 genes, which confirms multi-layer GO’s great potential in the biomedical field.

One-step synthesis and deposition of few-layer graphene via facile, dry ball-free milling

MRS Advances ◽  
2017 ◽  
Vol 2 (15) ◽  
pp. 847-856 ◽  
Author(s):  
Abdul Hai Alami ◽  
Kamilia Aokal ◽  
Mhd Adel Assad ◽  
Di Zhang ◽  
Hussain Alawadhi ◽  
...  
Keyword(s):  
Low Cost ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Hydrophobic Surface ◽  
Graphite Powder ◽  
High Energy ◽  
Layer Graphene ◽  
Wide Range ◽  
One Step ◽  
Few Layer Graphene

ABSTRACTGraphene is a 2-D carbon material showing considerable prominence in a wide range of optoelectronics, energy storage, thermal and mechanical applications. However, due to its unique features which are typically associated with difficulty in handling (ultra-thin thickness and hydrophobic surface, to name a few), synthesis and subsequent deposition processes are thus critical to the material properties of the prepared graphene films. While existing synthesis approaches such as chemical vapor deposition and epitaxial growth can grow graphene with high degree of order, the costly high temperature and/or high vacuum process prohibit the widespread usage, and the subsequent graphene transfer from the growth substrates for deposition proves to be challenging. Herein, a low-cost one-step synthesis and deposition approach for preparing few-layer graphene (FLG) on flexible copper substrates based on dry ball-free milling of graphite powder is proposed. Different from previous reports, copper substrates are inserted into the milling crucible, thus accomplishing simultaneous synthesis and deposition of FLG and eliminating further deposition step. Furthermore, while all previously reported high energy milling processes involve using balls of various sizes, we adopt a ball-free milling process relying only on centrifugal forces, which significantly reduces the surface damage of the deposition substrates. Sample characterization indicates that the process yields FLG deposited uniformly across all tested specimens. Consequently, this work takes graphene synthesis and deposition a step closer to full automation with simple and low-cost process.

scholarly journals Structure of Coal-Derived Metal-Supported Few-Layer Graphene Composite Materials Synthesized Using a Microwave-Assisted Catalytic Graphitization Process

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1672
Author(s):  
Faridul Islam ◽  
Arash Tahmasebi ◽  
Rou Wang ◽  
Jianglong Yu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Bituminous Coal ◽  
Critical Role ◽  
Fabricated Metal ◽  
Catalytic Graphitization ◽  
Microwave Assisted ◽  
Layer Graphene ◽  
Transmission Electron ◽  
Few Layer Graphene

Metal-supported few-layer graphene (FLG) was synthesized via microwave-assisted catalytic graphitization owing to the increasing demand for it and its wide applications. In this study, we quickly converted earth-abundant and low-cost bituminous coal to FLG over Fe catalysts at a temperature of 1300 °C. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and N2 adsorption–desorption experiments were performed to analyze the fabricated metal-supported FLG. The results indicated that the microwave-irradiation temperature at a set holding-time played a critical role in the synthesis of metal-supported FLG. The highest degree of graphitization and a well-developed pore structure were fabricated at 1300 °C using a S10% Fe catalyst for 20 min. High-resolution transmission electron microscopy analysis confirmed that the metal-supported FLG fabricated via microwave-assisted catalytic graphitization consisted of 3–6 layers of graphene nanosheets. In addition, the 2D band at 2700 cm−1 in the Raman spectrum of the fabricated metal-supported FLG samples were observed, which indicated the presence of few-layer graphene structure. Furthermore, a mechanism was proposed for the microwave-assisted catalytic graphitization of bituminous coal. Here, we developed a cost-effective and environmental friendly metal-supported FLG method using a coal-based carbonaceous material.

scholarly journals Pell-Shear-Exfoliation of few-layer graphene nanoflakes as an electrode in supercapacitors

2018 ◽  
Vol 6 (1) ◽  
pp. 1-10
Author(s):  
Ibrahem Aziz Mohammed
Keyword(s):  
Thin Films ◽  
Low Cost ◽  
Spray Coating ◽  
High Specific Capacitance ◽  
Optical Transmittance ◽  
High Quality ◽  
Layer Graphene ◽  
Graphene Nanoflakes ◽  
Wide Range ◽  
Few Layer Graphene

Introduction: The graphene has received a great attention because of its extraordinary characteristics of high carrier mobility, excellent thermal conductivity, high optical transmittance, and superior mechanical strength. Developing a simple methods with the property of producing large quantities of high-quality graphene have become essential for electronics, optoelectronics, composite materials, and energy-storage applications. Materials and Methods: In this study, the simple one step and efficient method of grinding was used to produce few-layers graphene nanoflakes from graphite. Different microscopic (TEM, SEM, and AFM) and spectroscopics (XRD, XPS, and Raman) charactrization tools were used to test the quality of the resultant graphene nanoflakes. Results: The produced nanoflakes showed no traces of oxidation due to the grinding process. In addition, the applicability of the obtained nanoflakes as potential supercapacitor electrodes was investigated. For that purpose, thin films of the few-layer graphene nanoflakes were developed using spray coating technique. In terms of both transparency and conductivity, the prepared films showed equivalent properties compared to those prepared by more complex methods. The electrochemical properties of the prepared electrodes showed high specific capacitance of 86 F g_1 at 10 A g_1 with excellent stability. The electrodes sustained their original capacity for more than 7000 cycles and started reducing to 72 F g−1 after 10000 cycles. Conclussions: The method provides a simple, efficient, versatile, and eco-friendly approach to low-cost mass production of high-quality graphene few-layers. The electrochemical stability and flexibility of the developed thin films indicated that the films could be used as electrodes in a wide range of electronic applications.

scholarly journals Multi-Layer Graphene Oxide in Human Keratinocytes: Time-Dependent Cytotoxicity, Proliferation, and Gene Expression

2021 ◽  
Author(s):  
Beatriz Salesa ◽  
Ángel Serrano-Aroca
Keyword(s):  
Graphene Oxide ◽  
Human Keratinocytes ◽  
Control Group ◽  
Hacat Cells ◽  
Layer Graphene ◽  
Wide Range ◽  
Epidermal Growth ◽  
Biomedical Field ◽  
Few Layer Graphene ◽  
Median Effective Concentration

Few-layer graphene oxide (GO) has shown none or very weak cytotoxicity and anti-proliferative effects in a wide range of cell lines such as glyoma cells and human skin HaCaT cells, in concentrations up to 100 µg/mL However, multi-layer GO has been hardly explored in the biomedical field. Thus, multi-layer GO was examined here in human keratinocyte HaCaT cells treated with different concentrations ranging from 0.01 to 150 µg/mL during different periods of times (3, 12 and 24 hours). The results of this study showed a time-concentration dependence with two non-cytotoxic concentrations (0.01 and 0.05 µg/mL) and a median effective concentration value of 4.087 µg/mL at 24 hours of GO exposure. Contrary to what has been reported for few-layer GO, cell proliferation of the HaCaT cells in contact with the multi-layer GO at 0.01 μg/mL showed identical proliferative activity compared to an epidermal growth factor (1.6-fold greater than the control group) after 96 hours. The effects of the multi-layer GO on the expression of 13 genes (SOD1, CAT, MMP1, TGFB1, GPX1, FN1, HAS2, LAMB1, LUM, CDH1, COL4A1, FBN and VCAN) at the non-cytotoxic concentrations of GO in the HaCaT cells were analyzed after 24 hours. Thus, the lowest non-cytotoxic GO concentration was able to up-regulate the CAT, TGFB1, FN1 and CDH1 genes, which confirms the great potential of multi-layer GO in the biomedical field.

scholarly journals A few-layer graphene/chlorin e6 hybrid nanomaterial and its application in photodynamic therapy against Candida albicans

2020 ◽  
Vol 11 ◽  
pp. 1054-1061
Author(s):  
Selene Acosta ◽  
Carlos Moreno-Aguilar ◽  
Dania Hernández-Sánchez ◽  
Beatriz Morales-Cruzado ◽  
Erick Sarmiento-Gomez ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Fungal Infections ◽  
Chlorin E6 ◽  
Ros Generation ◽  
Photodynamic Treatment ◽  
Hybrid Nanomaterial ◽  
Layer Graphene ◽  
Wide Range ◽  
Red Led ◽  
Few Layer Graphene

The global emergence of multidrug resistance of fungal infections and the decline in the discovery of new antibiotics are increasingly prevalent causes of hospital-acquired infections, among other major challenges in the global health care sector. There is an urgent need to develop noninvasive, nontoxic, and new antinosocomial approaches that work more effectively and faster than current antibiotics. In this work, we report on a biocompatible hybrid nanomaterial composed of few-layer graphene and chlorin e6 (FLG-Ce6) for the photodynamic treatment (PDT) of Candida albicans. We show that the FLG-Ce6 hybrid nanomaterial displays enhanced reactive oxygen species (ROS) generation compared with Ce6. The enhancement is up to 5-fold when irradiated for 15 min at 632 nm with a red light-emitting diode (LED). The viability of C. albicans in the presence of FLG-Ce6 was measured 48 h after photoactivation. An antifungal effect was observed only when the culture/FLG-Ce6 hybrid was exposed to the light source. C. albicans is rendered completely unviable after exposure to ROS generated by the excited FLG-Ce6 hybrid nanomaterial. An increased PDT effect was observed with the FLG-Ce6 hybrid nanomaterial by a significant reduction in the viability of C. albicans, by up to 95%. This is a marked improvement compared to Ce6 without FLG, which reduces the viability of C. albicans to only 10%. The antifungal action of the hybrid nanomaterial can be activated by a synergistic mechanism of energy transfer of the absorbed light from Ce6 to FLG. The novel FLG-Ce6 hybrid nanomaterial in combination with the red LED light irradiation can be used in the development of a wide range of antinosocomial devices and coatings.

2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

2020 ◽  
pp. 1192-1198
Author(s):  
M.S. Mohammad ◽  
Tibebe Tesfaye ◽  
Kim Ki-Seong
Keyword(s):  
Cost Effective ◽  
The Other ◽  
Thickness Gauge ◽  
Color Intensity ◽  
Digital Readout ◽  
Flat Surfaces ◽  
Video Cameras ◽  
Wide Range ◽  
Cost Effective Alternative ◽  
Ultrasonic Thickness

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.

p-Sulfonic acid calix[n]arene catalyzed synthesis of bioactive heterocycles: A review

2020 ◽  
Vol 24 ◽  
Author(s):  
Bubun Banerjee ◽  
Gurpreet Kaur ◽  
Navdeep Kaur
Keyword(s):  
Supramolecular Chemistry ◽  
Sulfonic Acid ◽  
Catalytic Efficiency ◽  
The Other ◽  
Reaction Conditions ◽  
Metal Free ◽  
Bioactive Scaffolds ◽  
Wide Range ◽  
Efficient Alternative ◽  
Bioactive Heterocycles

: Metal-free organocatalysts are becoming an important tool for the sustainable developments of various bioactive heterocycles. On the other hand, during last two decades, calix[n]arenes have been gaining considerable attention due to their wide range of applicability in the field of supramolecular chemistry. Recently, sulfonic acid functionalized calix[n] arenes are being employed as an efficient alternative catalyst for the synthesis of various bioactive scaffolds. In this review we have summarized the catalytic efficiency of p-sulfonic acid calix[n]arenes for the synthesis of diverse biologically promising scaffolds under various reaction conditions. There is no such review available in the literature showing the catalytic applicability of p-sulfonic acid calix[n]arenes. Therefore, we strongly believe that this review will surely attract those researchers who are interested about this fascinating organocatalyst.

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