scholarly journals Interactions between Reduced Graphene Oxide with Monomers of (Calcium) Silicate Hydrates: A First-Principles Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2248
Author(s):  
Mohammadreza Izadifar ◽  
Jorge S. Dolado ◽  
Peter Thissen ◽  
Andres Ayuela
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Calcium Ions ◽  
Calcium Silicate ◽  
Density Functional ◽  
Pristine Graphene ◽  
Chemical Compositions ◽  
Hydroxyl Groups ◽  
Condensation Reactions ◽  
Reduced Graphene

Graphene is a two-dimensional material, with exceptional mechanical, electrical, and thermal properties. Graphene-based materials are, therefore, excellent candidates for use in nanocomposites. We investigated reduced graphene oxide (rGO), which is produced easily by oxidizing and exfoliating graphite in calcium silicate hydrate (CSHs) composites, for use in cementitious materials. The density functional theory was used to study the binding of moieties, on the rGO surface (e.g., hydroxyl-OH/rGO and epoxide/rGO groups), to CSH units, such as silicate tetrahedra, calcium ions, and OH groups. The simulations indicate complex interactions between OH/rGO and silicate tetrahedra, involving condensation reactions and selective repairing of the rGO lattice to reform pristine graphene. The condensation reactions even occurred in the presence of calcium ions and hydroxyl groups. In contrast, rGO/CSH interactions remained close to the initial structural models of the epoxy rGO surface. The simulations indicate that specific CSHs, containing rGO with different interfacial topologies, can be manufactured using coatings of either epoxide or hydroxyl groups. The results fill a knowledge gap, by establishing a connection between the chemical compositions of CSH units and rGO, and confirm that a wet chemical method can be used to produce pristine graphene by removing hydroxyl defects from rGO.

scholarly journals Chemical and structural properties of reduced graphene oxide—dependence on the reducing agent

2020 ◽  
Vol 56 (5) ◽  
pp. 3738-3754
Author(s):  
B. Lesiak ◽  
G. Trykowski ◽  
J. Tóth ◽  
S. Biniak ◽  
L. Kövér ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Sodium Borohydride ◽  
Reduction Rate ◽  
Graphite Powder ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Vacancy Defects ◽  
Group Reduction ◽  
Reduced Graphene

AbstractGraphene oxide (GO) prepared from graphite powder using a modified Hummers method and reduced graphene oxide (rGO) obtained from GO using different reductants, i.e., sodium borohydride, hydrazine, formaldehyde, sodium hydroxide and L-ascorbic acid, were investigated using transmission electron microscopy, X-ray diffraction, Raman, infrared and electron spectroscopic methods. The GO and rGOs’ stacking nanostructure (flake) size (height x diameter), interlayer distance, average number of layers, distance between defects, elementary composition, content of oxygen groups, C sp3 and vacancy defects were determined. Different reductants applied to GO led to modification of carbon to oxygen ratio, carbon lattice (vacancy) and C sp3 defects with various in-depth distribution of C sp3 due to oxygen group reduction proceeding as competing processes at different rates between interstitial layers and in planes. The reduction using sodium borohydride and hydrazine in contrary to other reductants results in a larger content of vacancy defects than in GO. The thinnest flakes rGO obtained using sodium borohydride reductant exhibits the largest content of vacancy, C sp3 defects and hydroxyl group accompanied by the smallest content of epoxy, carboxyl and carbonyl groups due to a mechanism of carbonyl and carboxyl group reduction to hydroxyl groups. This rGO similar diameter to GO seems to result from a predominant reduction rate between the interstitial layers. The thicker flakes of a smaller diameter than in GO are obtained in rGOs prepared using remaining reductants and result from a higher rate of reduction of in plane defects.

Synthesis, Mechanical Properties, and in Vitro Biocompatibility with Osteoblasts of Calcium Silicate–Reduced Graphene Oxide Composites

2014 ◽  
Vol 6 (6) ◽  
pp. 3947-3962 ◽  
Author(s):  
Mehdi Mehrali ◽  
Ehsan Moghaddam ◽  
Seyed Farid Seyed Shirazi ◽  
Saeid Baradaran ◽  
Mohammad Mehrali ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Calcium Silicate ◽  
In Vitro Biocompatibility ◽  
Reduced Graphene ◽  
Oxide Composites

Can reduced graphene oxide look like few-layer pristine graphene?

2021 ◽  
pp. 108616
Author(s):  
Danilo Argentoni Nagaoka ◽  
Daniel Grasseschi ◽  
Sergio Humberto Domingues
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Pristine Graphene ◽  
Reduced Graphene

Electrical current stimulated desorption of carbon dioxide adsorbed on graphene based structures

RSC Advances ◽  
2016 ◽  
Vol 6 (49) ◽  
pp. 43401-43407 ◽  
Author(s):  
Ritesh Sevanthi ◽  
Fahmida Irin ◽  
Dorsa Parviz ◽  
W. Andrew Jackson ◽  
Micah J. Green
Keyword(s):  
Carbon Dioxide ◽  
Graphene Oxide ◽  
Adsorption Capacity ◽  
Reduced Graphene Oxide ◽  
Joule Heating ◽  
Electrical Current ◽  
Pristine Graphene ◽  
Graphene Films ◽  
Reduced Graphene

The objective of this study was to investigate Joule heating/electric swing adsorption (ESA) as a mode of regeneration and to compare the carbon dioxide (CO2) adsorption capacity of pristine graphene films and reduced graphene oxide (rGO) aerogels.

scholarly journals Gum Kondagogu/Reduced Graphene Oxide Framed Platinum Nanoparticles and Their Catalytic Role

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3643 ◽  
Author(s):  
Venkateshaiah ◽  
Silvestri ◽  
Ramakrishnan ◽  
Wacławek ◽  
Padil ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Platinum Nanoparticles ◽  
Environmentally Benign ◽  
Hydroxyl Groups ◽  
Average Particle ◽  
Face Centered Cubic ◽  
Reduced Graphene ◽  
Gum Kondagogu

This study investigates an environmentally benign approach to generate platinum nanoparticles (Pt NP) supported on the reduced graphene oxide (RGO) by non-edible gum waste of gum kondagogu (GK). The reaction adheres to the green chemistry approach by using an aqueous medium and a nontoxic natural reductant—GK—whose abundant hydroxyl groups facilitate in the reduction process of platinum salt and helps as well in the homogenous distribution of ensued Pt NP on RGO sheets. Scanning Electron Microscopy (SEM) confirmed the formation of kondagogu gum/reduced graphene oxide framed spherical platinum nanoparticles (RGO-Pt) with an average particle size of 3.3 ± 0.6 nm, as affirmed by Transmission Electron Microscopy (TEM). X-ray Diffraction (XRD) results indicated that the Pt NPs formed are crystalline with a face-centered cubic structure, while morphological analysis by XRD and Raman spectroscopy revealed a simultaneous reduction of GO and Pt. The hydrogenation of 4-nitrophenol could be accomplished in the superior catalytic performance of RGO-Pt. The current strategy emphasizes a simple, fast and environmentally benign technique to generate low-cost gum waste supported nanoparticles with a commendable catalytic activity that can be exploited in environmental applications.

Electrophoretic deposition of calcium silicate–reduced graphene oxide composites on titanium substrate

2016 ◽  
Vol 36 (2) ◽  
pp. 319-332 ◽  
Author(s):  
Mehdi Mehrali ◽  
Amir Reza Akhiani ◽  
Sepehr Talebian ◽  
Mohammad Mehrali ◽  
Sara Tahan Latibari ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Electrophoretic Deposition ◽  
Calcium Silicate ◽  
Titanium Substrate ◽  
Reduced Graphene ◽  
Oxide Composites

scholarly journals Adsorption Characteristics of Phenolic Compounds on Graphene Oxide and Reduced Graphene Oxide: A Batch Experiment Combined Theory Calculation

2018 ◽  
Vol 8 (10) ◽  
pp. 1950 ◽  
Author(s):  
Xiaobo Wang ◽  
Yanhui Hu ◽  
Jianhua Min ◽  
Sijie Li ◽  
Xiangyi Deng ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Phenolic Compounds ◽  
Reduced Graphene Oxide ◽  
Electron Density ◽  
Density Functional ◽  
Influence Factors ◽  
Thermodynamic Characteristics ◽  
Major Influence ◽  
Chemical Structures ◽  
Reduced Graphene

A series of phenolic compounds containing 2-phenylphenol (PPE), bisphenol A (BPA), 4-isopropylphenol (IPE), 4-methylphenol (ME) and phenol (PE) were selected to investigate their major influence factors for their adsorption on graphene oxide (GO) and reduced graphene oxide (RGO) by studying their adsorption isotherms and kinetics. It was found that the adsorption of all tested phenols fitted well with the Freundlich model. In comparison, the adsorption ability of RGO with a stronger π-π interaction was superior to GO, which was confirmed by using naphthalene probe measurements. The thermodynamic characteristics, by studying the effect of the adsorption temperatures (298, 313 and 333 K), demonstrated that the adsorption process was spontaneous, exothermic and entropy-decreasing. The chemical structures of the phenols also affected their adsorption on GO and RGO. It was found that the adsorption capacities of phenols were, in order, PE (0.271 mmol g−1 on GO and 0.483 mmol g−1 on RGO) < ME (0.356 and 0.841 mmol g−1) < IPE (0.454 and 1.117 mmol g−1) < BPA (0.4 and 1.56 mmol g−1) < PPE (0.7 and 2.054 mmol g−1), which depended on the π-electron density of the benzene ring by means of a density functional theory (DFT) calculation. Undoubtedly, the reduction of GO and an increase in π-electron density on the chemical structures of phenols facilitated the adsorption.

Functionalization and Chemical Linking of Reduced Graphene Oxide or Graphite onto Polyurethane and the Impact on the Tensile Strength and Sheet Resistance of Polymer Composites

2018 ◽  
Vol 26 (2) ◽  
pp. 141-153
Author(s):  
Yong-Chan Chung ◽  
Ho-Sung Kim ◽  
Byoung Chul Chun
Keyword(s):  
Tensile Strength ◽  
Graphene Oxide ◽  
Shape Memory ◽  
Reduced Graphene Oxide ◽  
Sheet Resistance ◽  
Sharp Decrease ◽  
Hydroxyl Groups ◽  
Functionalized Graphene Oxide ◽  
Reduced Graphene ◽  
The Impact

Reduced graphene oxide (RGO) or graphite is functionalized with hydroxyl groups for linking to the sides of polyurethane (PU) chains. Blended PU with RGO or graphite is prepared as a control for comparison. The PU composites are compared with respect to their spectroscopic, thermal, mechanical, shape memory, and sheet resistance properties. Scanning electron microscopy images demonstrate the good distribution of functionalized graphene oxide (FGO) or functionalized graphite (FG) particles on the inner surface of the PU. The linking of FGO or FG onto PU does not significantly affect the thermal behavior or shape memory properties but sharply improves the tensile strength of the PU composites without a noticeable decrease in tensile strain. The shape recovery of PU composites remains at approximately 90%, regardless of the FGO or FG content. The FG-linked PU composites exhibit a sharp decrease in sheet resistance as the FG content increases, whereas the sheet resistance of the FGO-linked PU composites does not decrease with increasing FGO content. The control PU composites with blended RGO or graphite show significant reductions in their sheet resistance. Considering the ease of functionalization of the graphite surface and the significant improvement in tensile strength, linking FG onto PU is advantageous for the development of PU composites with low sheet resistance.

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