| 1. |
- Jovanović, Aleksandar Z., et al.
(författare)
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Reactivity of Stone-Wales defect in graphene lattice – DFT study
- 2023
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Ingår i: FlatChem. - : Elsevier. - 2452-2627. ; 42
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the reactivity of carbon surfaces is crucial for the development of advanced functional materials. The SW defect is commonly present in carbon materials, but a comprehensive understanding of its effects on the reactivity of carbons is missing. In this study, we systematically investigate the reactivity of graphene surfaces with the Stone-Wales (SW) defect using Density Functional Theory calculations. We explore the atomic adsorption of various elements, including rows 1–3 of the Periodic Table, potassium, calcium, and selected transition metals. Our results demonstrate that the SW defect enhances binding with the studied adsorbates when compared to pristine graphene, with carbon and silicon showing the most significant differences. Additionally, we examine the effects of mechanical deformation on the lattice by constraining the system with the SW defect to the pristine graphene cell. Interestingly, these constraints lead to even stronger binding interactions. Furthermore, for carbon, nitrogen, and oxygen adsorbates, we observe that mechanical deformation triggers the incorporation of adatoms into the carbon bond network, leading to the reorganization of the SW defect structure. This work establishes a foundation for future studies in the defect and strain engineering of graphene, opening avenues for developing advanced materials and catalysts with enhanced reactivity and performance.
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| 2. |
- Khaliha, Sara, et al.
(författare)
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Defective graphene nanosheets for drinking water purification : Adsorption mechanism, performance, and recovery
- 2021
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Ingår i: FlatChem. - : Elsevier. - 2452-2627. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- Defect-rich graphene oxide (dGO) was used as sorbent for organic contaminants of emerging concern in tap water, including drugs and dyes, and the performance compared to those of lower-defects graphene types. The role of holes and carbonyl- carboxylic groups on graphene nanosheets surface on the adsorption mechanism and efficiency was investigated. dGO showed enhanced adsorption capacity toward two fluoroquinolone antibiotics (ofloxacin, OFLOX, and ciprofloxacin, CIPRO) in tap water with a maximum capacity of 650 mg/g, compared to 204 mg/g for Hummers derived commercial GO (hGO) and 125 mg/g for less defected Brodie derived GO (bGO) for OFLOX. The role of defects on the selective adsorption of OFLOX was also modelled by MD simulations, highlighting a mechanism mainly driven by the shape complementarity between the graphene holes and the molecules. Adsorption isotherms revealed different adsorption model for dGO, with a Langmuir fitting for dGO and BET fitting for all the other investigated samples. The maximum adsorption capacity of dGO for OFLOX was about six times higher than that of Granular Activated Carbon (95 mg/g), the industrial adsorption standard technology. Finally, it was also demonstrated that dGO can be recovered from treated water by ultrafiltration, this preventing secondary contamination risks and enabling safe use of graphene nanosheets for water purification.
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| 3. |
- Kumari, Sangita, et al.
(författare)
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Octadecanethiol-grafted molybdenum disulfide nanosheets as oil-dispersible additive for reduction of friction and wear
- 2017
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Ingår i: FlatChem. - : Elsevier. - 2452-2627. ; 3, s. 16-25
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Tidskriftsartikel (refereegranskat)abstract
- Molybdenum disulfide (MoS2) easily shears at the contact interfaces because of weak interplaner interaction and exhibits high mechanical strength, which promises its potential for tribological applications. However, poor dispersibility of MoS2 in the lube oils has been a great challenge. Herein, a facile and scalable hydrothermal approach is presented to synthesize the MoS2 nanosheets and then chemically functionalized with octadecanethiol (ODT). The structural defects and vacant sulfur sites on the Mo-atoms of MoS2 nanosheets are targeted for grafting of ODT via Mo-S dative linkage. The chemical and structural features of MoS2-ODT are characterized by FTIR, XPS, XRD and HRTEM analyses. The dispersion stability of MoS2-ODT nanosheets in the polyol ester lube oil is examined by UV–Visible spectroscopy. The van der Waals interaction between the octadecyl chain of MoS2-ODT and oleate chains of polyol ester lube oil facilitates the dispersion of MoS2-ODT nanosheets. Tribological results revealed that minute dosing (0.05 mg.mL−1) of thoroughly dispersed MoS2-ODT nanosheets, as an additive to polyol lube oil, significantly reduced the friction and the wear of steel tribo-pair. The uninterrupted supply of MoS2-ODT nanosheets on the tribo-contacts, formation of MoS2 thin film on tribo-interfaces, ease of shearing driven by weak van der Waals interaction between MoS2 lamellae and high mechanical strength of MoS2, collectively enhanced the tribo-performance, when thoroughly dispersed MoS2-ODT was used as an additive to the polyol lube base oil.
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| 4. |
- Liang, L., et al.
(författare)
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Theoretical study on the interaction of nucleotides on two-dimensional atomically thin graphene and molybdenum disulfide
- 2017
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Ingår i: FlatChem. - : Elsevier B.V.. - 2452-2627. ; 2, s. 8-14
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the interaction between single nucleotide and polynucleotides composed of different nucleotides and two-dimensional (2D) materials (graphene and MoS2) were investigated through first principles calculations and molecular dynamics (MD) simulation. The binding energy strength between single nucleotide and graphene is G > C > A > T, and it is G > A > C > T between single nucleotide and MoS2, derived from density function density (DFT) calculations. The binding strength between polynucleotide and graphene is A6 > G6 > T6 > C6, and the order is G6 > A6 > C6 > T6 of binding strength between polynucleotide and MoS2, calculated from molecular dynamics simulation. The average binding free energy for different single nucleotide A, T, C, G (polynucleotides A6, T6, C6, G6) on graphene sheet is −4.17 kcal/mol (-10.04 kcal/mol), and it is about −2.29 kcal/mol (-2.24 kcal/mol) on MoS2 surface. The binding strength for different single nucleotide (polynucleotides) on graphene sheets is around 2 times (4 times) stronger than that between nucleotide (polynucleotides) and MoS2 surface. The different absorption strength of nucleotides on these two-dimensional materials may be utilized for different promising applications.
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| 5. |
- Méndez-Reséndiz, Abraham, et al.
(författare)
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Highly crystalline selectively oxidized graphene for supercapacitors
- 2023
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Ingår i: FlatChem. - : Elsevier BV. - 2452-2627. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- Graphene oxide (GO) is usually regarded as a graphene precursor for scalable synthesis, mainly due to its aqueous processability from introducing oxygen functionalities. Nevertheless, the precise control of graphene's oxidation degree to obtain a good balance between dispersion stability and crystallinity remains challenging. This study describes a simple and practical approach to synthesize a new graphene-based material called selectively oxidized graphene (SOG), which combines the advantages of graphene and GO. SOG shows water stability of −36.2 mV, a C/O ratio of 5.2, and most importantly, a very high crystallinity degree, with an ID/IG of 0.414. The synthesized SOG exhibits an ultra-low optical band gap of 0.04 eV, 75 times lower than GO. Moreover, the electrical resistance, 1.12 KΩ/sq is nine orders of magnitude smaller than GO. Additionally, it also shows promising 3-electrode capacitance with an improvement above 400 % compared to exfoliated graphene. A Swagelok-based supercapacitor was fabricated to analyze the feasibility of SOG for energy storage applications, which exhibited remarkable characteristics such as ∼ 93F g−1 capacitance and ∼ 99.8 % retention after 10,000 cycles. The characteristics of SOG ensure that this new material is promising for applications in organic electronics.
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| 6. |
- Mulone, Antonio, 1989, et al.
(författare)
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Electrodeposition of FeW-graphene composites: Effect of graphene oxide concentration on microstructure, hardness and corrosion properties
- 2023
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Ingår i: FlatChem. - 2452-2627. ; 40
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Tidskriftsartikel (refereegranskat)abstract
- Graphene has emerged as excellent reinforcement for electrodeposited metallic composites. The poor stability of graphene in electrochemical baths makes it challenging to obtain uniform composite coatings. In this work, we investigate the possibility to electrodeposit FeW-graphene coatings with organic stablizers. Polydiallyldimethylammonium chloride is selected to stabilize the graphene oxide which is added into the electrolyte in various concentrations. Scanning electron microscopy and Raman analysis confirmed the successful co-deposition of graphene in all the coatings. The composition of the FeW matrix remained unaffected by the addition of graphene, while an increase in the crystallinity of the structure of the composites was observed. Graphene was retained even after the coatings were heat treated at 400 °C for 1 h. The hardness and the corrosion resistance of the FeW-graphene composite were largely improved: a 22% increase in hardness and an 80% increase in corrosion resistance were measured compared to the graphene-free coating.
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| 7. |
- Panigrahi, Puspamitra, et al.
(författare)
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Stacked Si2BN monolayers as ultra-high-capacity anode material for divalent Mg-ion batteries
- 2022
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Ingår i: FlatChem. - : Elsevier. - 2452-2627. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- In pursuit of developing next-generation energy storage systems, there has been increasing effort in multivalent rechargeable batteries, such as magnesium-ion batteries (MgIBs). Non-toxicity, earth abundance, and high storage capacity due to their divalent nature make MgIBs an ideal alternative to the existing lithium-ion batteries (LIBs). However, exploring efficient electrode materials capable of storing large quantities of Mg ions is one of the biggest challenges in actualizing MgIBs. Here first-principles density functional theory (DFT) simulations are employed to explore the potential of Si2BN monolayers as a novel anode material for MgIBs. We find that under the maximum coverage effect, the stacked Si2BN could attain a specific capacity of 359.94 mAh g-1, which further enhances to 1418.45 mAh g-1 with a defect concentration of 12 %. The open-circuit voltages fall in the ranges of 0.42-0.46 V and 0.88-0.98 V for the pristine and defected Si2BN, respectively. Diffusion barrier calculations reveal that Mg ions diffuse 125 times faster on pristine Si2BN than the defected one. Our simulations determine that the electronic structures, binding mechanism, equilibrium cell voltages, ionic mobilities, and thermal stabilities of stacked Si2BN make it an excellent anode material for MgIBs.
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| 8. |
- Piñeiro-García, Alexis, et al.
(författare)
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Functionalization and soft photoreduction of graphene oxide triggered by the photoinitiator during thiol-ene radical addition
- 2022
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Ingår i: FlatChem. - : Elsevier. - 2452-2627. ; 33
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Tidskriftsartikel (refereegranskat)abstract
- Thiol-ene radical addition (TERA) is a powerful reaction for the chemical functionalization of the reactive alkenes of GO with thiols. To trigger TERA, a photoinitiator (PI) is added to ensure high yields associated with fast conversion rates. However, the inappropriate use of PIs might affect the GO functionalization leading to photoreduction as well as low conversion rates. Herein, we explored the GO functionalization with cysteamine (CA) by TERA and its reduction influenced by Irgacure® 369, a commercial PI. We focused to analyze the reaction conditions that promote an orthogonal GO functionalization finding the limits where the photoreduction began. UV-spectroscopy, Raman spectroscopy, fluorescence labeling and XPS were used to characterize the functionalized GO. The data indicate three possible scenarios depending on the PI/CA molar ratio: i) orthogonal GO functionalization by TERA, ii) side reactions between GO and the radicals formed upon the PI photocleavage, and iii) soft photoreduction of the GO with alcohols and carboxylic acids as the functional groups mainly affected. However, we found that the GO functionalization by TERA was still occurring, but in less favorable conditions despite the side reactions and by-products. Therefore, photo-initiated TERA was confirmed as a powerful reaction to functionalize the reactive alkenes of GO, and by tuning the PI/CA molar ratio an orthogonal GO functionalization can be achieved, limiting side reactions and particularly GO reduction.
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| 9. |
- Sernelius, Bo E., 1948-
(författare)
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Core-level spectra from bilayer graphene
- 2017
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Ingår i: FlatChem. - : Elsevier. - 2452-2627. ; 1, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- We derive core-level spectra for doped free-standing bilayer graphene. Numerical results are presented for all nine combinations of the doping concentrations 1012 cm-2; 1013 cm-2, and 1014 cm-2 in the two graphene sheets and we compare the results to the reference spectra for monolayer graphene. We furthermore discuss the spectrum of single-particle inter-band and intra-band excitations in the ωq-plane, and show how the dispersion curves of the collective modes are modified in the bilayer system.
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| 10. |
- Zomorodian Esfahani, Majid, et al.
(författare)
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Copper oxide/graphene-based composites: Synthesis methods, appliances and recent advancements
- 2024
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Ingår i: FlatChem. - : Elsevier BV. - 2452-2627. ; 47
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Forskningsöversikt (refereegranskat)abstract
- Nanomaterials adorned on graphene comprise an essential component of a wide range of devices wherein graphene-based copper oxide nanocomposites have garnered significant attention in recent years. Copper oxides (CuO and Cu2O) are semiconductors with distinctive optical, electrical, and magnetic properties. Their earth abundance, low cost, narrow bandgap, high absorption coefficient, and low toxicity of copper oxides are just a few key advantages. CuO is superior to Cu2O in optical switching applications because of its narrower bandgap. Therefore, integrating graphene with copper oxides renders the ensuing nanocomposites much more valuable for various applications. Not surprisingly, a wide range of promising synthesis and processing techniques have been considered, focusing on multiple appliances such as sensors, energy storage, harvesting, and electrocatalysis. Herein, the most recent synthesis techniques and applications of doped, undoped, and hierarchical structures of CuO/Cu2O-graphene-based nanocomposites are deliberated, including the potential future usages.
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