Atomistic simulations of dopamine diffusion dynamics on a pristine graphene surface

The adsorption of methane (CH4) molecule on the pristine and Al-doped (4, 8) graphene was investigated via the first-principles calculations. The results demonstrated that, in comparison to the adsorption of a CH4molecule on the pristine graphene sheet, a relatively stronger adsorption was observed between the CH4molecule and Al-doped graphene with a shorter adsorption distance, larger binding energy and more charge-transfer from the graphene surface to the CH4molecule. Therefore, the Al-doped graphene can be expected to be a novel sensor for the detection of CH4molecules in future applications.

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Cleaning of graphene surfaces by low-pressure air plasma

Royal Society Open Science ◽

10.1098/rsos.172395 ◽

2018 ◽

Vol 5 (5) ◽

pp. 172395 ◽

Cited By ~ 7

Author(s):

Phuong Viet Pham

Keyword(s):

Photoelectron Spectroscopy ◽

Graphene Film ◽

Chemical Vapour ◽

Optical Microscope ◽

Pristine Graphene ◽

Air Plasma ◽

Graphene Surface ◽

Force Microscopy ◽

Atomic Force ◽

The One

The polymer residues still present on a chemical vapour-deposited graphene surface after its wet transfer by the poly(methyl methacrylate) method to the arbitrary substrates, tend to cause problems such as electrical degradation and unwanted intentional doping. In this study, by using an effective cleaning method for the graphene surface by air-assisted plasma, the graphene surface was cleaned significantly without damaging the graphene network, which resulted in the reduction (approx. 71.11%) of polymer residues on its surface. The analysis reveals that this approach reduced the D-band (impurities, polymer residues) formation while maintaining the π-bonding of the graphene, which affects conductivity. By characterizations of the optical microscope, Raman spectroscopy and atomic force microscopy, we obtained a significantly cleaner graphene surface (roughness of 4.1 nm) compared to pristine graphene (roughness of 1.2 nm) on a SiO 2 substrate. In addition, X-ray photoelectron spectroscopy data revealed that the C1s peak of the air-assisted graphene film was higher than the one of a pristine graphene film, indicating that a cleaner graphene surface was obtained.

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Accelerating Atomistic Simulations of Defect Dynamics: Hyperdynamics, Parallel Replica Dynamics, and Temperature-Accelerated Dynamics

MRS Proceedings ◽

10.1557/proc-538-427 ◽

1998 ◽

Vol 538 ◽

Cited By ~ 15

Author(s):

Arthur F. Voter ◽

Mads R. Sørensen

Keyword(s):

Molecular Dynamics ◽

State Theory ◽

Atomistic Simulations ◽

New Methods ◽

Diffusion Dynamics ◽

Daunting Task ◽

System Temperature ◽

Dynamics Simulations ◽

Dynamics Method ◽

Infrequent Event

AbstractObtaining a good atomistic description of diffusion dynamics in materials remains a daunting task due to the time-scale limitations of the molecular dynamics method. We discuss new methods, derived from transition state theory, for accelerating molecular dynamics simulations of these infrequent-event processes. Two of these methods (hyperdynamics and parallel replica dynamics) have been presented previously, and are briefly reviewed here. The third, temperature-accelerated dynamics (TAD), is presented in detail. In TAD, the system temperature is raised to stimulate more rapid escape out of each potential basin, but attempted transitions are filtered to allow only those that would have occurred at the normal temperature. The characteristics of the methods are compared.

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Reversible hydrogenation restores defected graphene to graphene

Science China Chemistry ◽

10.1007/s11426-020-9959-5 ◽

2021 ◽

Author(s):

Lin Jiang ◽

Pauline M. G. van Deursen ◽

Hadi Arjmandi-Tash ◽

Liubov A. Belyaeva ◽

Haoyuan Qi ◽

...

Keyword(s):

Carrier Mobility ◽

Protective Layer ◽

Monolayer Graphene ◽

Pristine Graphene ◽

Graphene Surface ◽

Hydrogenated Graphene ◽

Hydrocarbon Molecules ◽

Cleaning Protocol ◽

Hydrogenation Treatment

AbstractGraphene as a two-dimensional material is prone to hydrocarbon contaminations, which can significantly alter its intrinsic electrical properties. Herein, we implement a facile hydrogenation-dehydrogenation strategy to remove hydrocarbon contaminations and preserve the excellent transport properties of monolayer graphene. Using electron microscopy we quantitatively characterized the improved cleanness of hydrogenated graphene compared to untreated samples. In situ spectroscopic investigations revealed that the hydrogenation treatment promoted the adsorption ofytyt water at the graphene surface, resulting in a protective layer against the re-deposition of hydrocarbon molecules. Additionally, the further dehydrogenation of hydrogenated graphene rendered a more pristine-like basal plane with improved carrier mobility compared to untreated pristine graphene. Our findings provide a practical post-growth cleaning protocol for graphene with maintained surface cleanness and lattice integrity to systematically carry a range of surface chemistry in the form of a well-performing and reproducible transistor.

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The Catalysis Effect of Na and Point Defect on NO Heterogeneous Adsorption on Carbon during High-Sodium Zhundong Coal Reburning: Structures, Interactions and Thermodynamic Characteristics

Catalysts ◽

10.3390/catal11091046 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1046

Author(s):

Xuesen Kou ◽

Jing Jin ◽

Yongzhen Wang ◽

Yanhui Li ◽

Fengxiao Hou

Keyword(s):

Density Functional ◽

Heterogeneous Reaction ◽

Exothermic Reaction ◽

Thermodynamic Characteristics ◽

Interaction Force ◽

Pristine Graphene ◽

Covalent Bonds ◽

Graphene Surface ◽

High Sodium ◽

Zhundong Coal

The reburning process in a furnace, a key way to reduce NOx emissions, is a heterogeneous reaction during coal combustion, in which the heterogeneous adsorption is dominant. Zhundong coal with a high content of alkali metal can enhance the reburning process. In this paper, the influence of sodium and a defect on NO heterogeneous adsorption was studied by the density functional theory, and the thermodynamic characteristic was also analyzed. The results indicate that the binding energy for NO adsorption on the pristine graphene surface (graphene-NO), Na-decorated pristine graphene surface (graphene-Na-NO), defect graphene surface (gsv-NO) and Na-decorated defect graphene (gsv-Na-NO) is −5.86, −137.12, −48.94 and −74.85 kJ/mol, respectively, and that the heterogeneous adsorption is an exothermic reaction. Furthermore, except for covalent bonds of C and N, C and O for gsv-NO, other interactions are a closed-shell one, based on the analysis of AIM, ELF and IGM. The area of electron localization for NO is graphene-Na-NO > gsv-Na-NO > gsv-NO > graphene-NO. The dispersion interaction is the main interaction force between NO and the pristine graphene surface. The δg index for the atom pairs about N–C and O–C on the pristine graphene surface is also the smallest. The density of spikes at graphene-Na-NO is bigger than that at gsv-Na-NO. Moreover, the thermodynamics characteristic showed that the reaction equilibrium constant of graphene-NO is less than those on the other surfaces under the same temperature. Thus, NO on the pristine graphene surface is the most difficult to adsorb, but the presence of sodium and a defect structure can promote its adsorption.

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