Al-doped Graphene Research Articles

Adsorption of ethylene and 1-methylcyclopropene (1-MCP) on Al-doped graphene structure: A DFT study for gas sensing application

Ethylene is the ripening hormone of fruits and vegetables. 1-Methylcyclopropene (1-MCP) is used as the inhibitor of the ethylene actions for extending the postharvest shelf life of the plants. To control the ripening and extending the shelf life of the plants, the adsorption characteristics of ethylene and 1-MCP on Al-doped graphene structure (AlG) were investigated as a gas sensing application by density functional theory (DFT) calculations. The geometric structures were optimized, HOMO and LUMO, energy gap, adsorption energies, the density of states (DOS), electrostatic potential (ESP) and the global reactivities were calculated for different distances between the adsorbed ethylene or 1-MCP and the adsorbent AlG. Chemisorption and physisorption interactions were analyzed. For the chemisorption process of ethylene and 1-MCP on AlG, the adsorption energies were 19.34 kJ/mol and 56.53 kJ/mol, respectively. Whereas for the physisorption process, the adsorption energies of ethylene and 1-MCP were -60.16 kJ/mol and -7.32 kJ/mol, respectively. As a result, it was presented that the AlG structure has sufficient characteristics to be a good adsorbent and a gas sensor of ethylene and 1-MCP.

Coexistence of doping and strain to tune electronic and optical properties of monolayer graphene

We performed first-principles calculations to study the structural, electronic and optical properties of monolayers graphene through strain and Al atoms doping with different concentrations. The results show that band gap of pristine graphene and graphene doped with 3.at% of Al consistently increases with strain, whereas the band gap of graphene doped with 6 at%, 9 at%, and 12 at% of Al initially increases and subsequently decreases as strain is introduced, and the band gap characteristics change from direct to indirect.Notably, a flat band phenomenon was found when the strain of 6.at%Al doped graphene reached 10 %. Furthermore, the study of optical properties reveals that the increase of Al doping concentration leads to a redshift of the peak in the imaginary part of the dielectric constant of graphene. This not only reduces reflectance to ultraviolet light but also enhances absorption of visible light while decreasing transmittance within the infrared and visible light ranges. Additionally, strain further induces a redshift in the imaginary part of the dielectric constant of Al-doped graphene.

Nitrogen and aluminum-nitrogen doped graphene for non-volatile resistive memory applications

Doping is a key strategy used to tune the electronic properties of graphene. Calculations have shown that graphene doped with Al has potential applications in the sensing of toxic gases. However, the realization of Al-doped graphene in experiments has proven to be a challenge. In this study, we successfully doped graphene with both N and a combination of Al and N using a microwave process suitable for large-scale production. Several characterization methods such as Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and energy dispersive x-ray spectroscopy (EDX) were used to confirm the composition, and therefore the successful doping, of the graphene. Doping and co-doping are found to increase the conductivity of graphene. It is also demonstrated that the doped graphene shows well-defined resistive memory properties when included in a sandwich structure consisting of polystyrene/doped graphene/polystyrene. The on-and-off voltage is found to be 2 V, making the Al-N co-doped graphene suitable for applications in resistive memory devices.

The co-adsorption of sulfate and metal ions on Al-doped graphene: a first principles study.

The co-adsorption of sulfate and metal ions on intrinsic and Al-doped graphene is investigated through first principles calculations. When SO42- ions exist only, both of intrinsic and Al-doped graphene can form stable adsorption configurations with SO42-. However, the presence of Cu2+/Ca2+/Zn2+/Mg2+ ions attenuates the interaction between intrinsic graphene and SO42-, resulting in weak physical adsorption between them, while Al-doped graphene can still constitute co-adsorption chemically with both SO42- and Cu2+/Ca2+/Zn2+/Mg2+ ions simultaneously. The sensitivity of Al-doped graphene towards co-adsorbed ions is in the order of SO42--Cu2+ > SO42--Zn2+ > SO42--Ca2+ > SO42--Mg2+. The research indicates Al-doped graphene could be a promising material for sensing sulfate ions under the presence of various metal ions. All of the calculations were carried out by using a first principles method based on density functional theory (DFT). The generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional was selected to describe electron exchange-correlation energy. The double numerical plus polarization (DNP) was employed as the basis set. The conductor-like screening model (COSMO) was implemented to simulate the aqueous solvent effect.

Adsorption of SO2 air pollutant gas molecule on the pure and Al-doped graphene nano sheet: A DFT study

The interaction of pure graphene nano sheet and Al-doped graphene nano sheet with SO2 pollutant gas molecules was examined by density functional theory (DFT). Adsorption energies and the transferred Mulliken charge were calculated. Doping Al on the graphene improved adsorption and electronic properties of graphene. Dos plots and HOMO-LUMO band gaps showed that pure graphene and Al-doped were semiconductor materials. The results revealed that sensitivity of graphene-based materials was enhanced by doping Al on the surface of pure graphene. Thus, Al-doped graphene was found to be a better detector of SO2 gas molecules.

Investigation the ability of pure and Al-doped graphene nano materials to detect toxic gases using first principle study

In the present study, the density function theory (DFT) method was used to compute structural, electronic and spectroscopic properties for pure and aluminum (Al) doped graphene materials, 6-13G basis set and hybrid function B3LYP were used in the present study. The structural properties show that pure and Al-doped graphene materials have a plane surface, also all bond lengths are in agreement with experimental results. Energy gap calculation shows that pure and Al-doped graphene materials have having semiconductor nature. When hydro cyanide gas molecule will have interacted on the surface of pure and Al-doped graphene materials, properties belonging to the systems under study will change. The result shows that interaction of HCN gas molecule with Al-doped graphene material the surface will rise up, but in the pure system, the surface remains plane. Adsorption calculation shows that HCN gas molecule can interact with the surface of a system under study. high chemical adsorption appears at a distance 1 Å between the gas molecule and pure and Al-doped graphene materials. Increasing adsorption distance interaction strength will be decreased until reached 0.002 eV. Positive adsorption energy refers to the repulsion force between the gas molecule and the surface. Fourier transformation infrared radiation (FT-IR) spectroscopy has been used to point-free radicals for interacted systems. It is pointed to carbon groups such as C-C, C-H, C-N and C-Al, also results show that all wave numbers results are in agreement with previous reports. Appear cyanide radical is a sign of chemical adsorption between gas molecules and the surface of pure and Al-doped graphene materials.

Adsorption and Sensing Properties of Formaldehyde on Chemically Modified Graphene Surfaces

Chemically modifying graphene (such as chemical doping) is a commonly used method to improve its formaldehyde sensing properties, but the microscopic mechanisms of heteroatoms in the adsorption and sensing process are still unclear. In this paper, the adsorption and sensing properties of formaldehyde on graphene surfaces modified by X doping (X = B, N, O, P, S, Mg and Al) were systematically investigated by first-principles calculations. The adsorption geometries, adsorption energies, charge transfers, and electronic structures were obtained and analyzed. The adsorption strengths of HCHO molecule on the Mg- and Al-doped graphene surfaces were stronger than those of non-metal (B, N, O, P and S)-doped cases. These results showed that the Mg- or Al-doped graphene was better for HCHO detecting than the non-metal-doped graphene systems. The sensing properties were simulated by theNEGF method for the two-probe nano-sensors constructed from Al- and Mg-doped graphene. The maximum sensing responses of nano-sensors based on Al- and Mg-doped graphene were obtained to be 107% and 60%, respectively. The present study supplies a theoretical basis for designing superior graphene-based HCHO gas sensors.

Direct synthesis of large-area Al-doped graphene by chemical vapor deposition: Advancing the substitutionally doped graphene family

Direct synthesis of large-area Al-doped graphene by chemical vapor deposition: Advancing the substitutionally doped graphene family

A DFT-based analysis of adsorption properties of fluoride anion on intrinsic, B-doped, and Al-doped graphene.

Fluorine emission from domestic wastewater is a major cause of severe environmental issues. In this paper, the density functional theory has been used to reveal the adsorption properties of F- ions and HF molecules on intrinsic graphene, B-doped graphene, and Al-doped graphene. Throughout the analysis of band structure, geometric structure, adsorption energy, charge transfer, charge density, density of states, and frontier orbital, we can find that the adsorption of F- ions and HF molecules on intrinsic graphene and HF molecules on B-doped graphene is weak, and it is only physical adsorption. When F- ions and HF molecules are adsorbed on Al-doped graphene and F- ions adsorbed on B-doped graphene, the adsorption energy, charge transfer, and charge density greatly increase, and the adsorption distance significantly decreases, and there exist obvious hybridizations by analyzing the charge density and density of states. We can also find that Al-doped graphene is more sensitive to F- ions after comparing the variation of band gap. The work conducted in this research provides a theoretical guidance for the application of fluorine sensors based on graphene.

First-principles investigation of the structure and electronic properties of graphene toward Li adsorption

ABSTRACT The first-principles calculation is performed to investigate the possibility of applying pristine, defected, N-doped, Al-doped and N-Al co-doped graphene in the feasible materials of lithium ion battery. Defected, monoatomic doped and diatomic doped graphene have different effects for Li adsorption. For monoatomic doped graphene, the adsorption energy of Al-doped graphene is the lowest, and its final adsorption distance is the shortest. Among the three types of diatomic doped graphene, N–Al para co-doped graphene is more suitable for the lithium ion battery anode material. Furthermore, the band structures of graphene absorbed with Li are analysed in detail, which indicates that pristine graphene adsorbed with Li belongs to physical adsorption while defected and doped graphene adsorbed with Li belongs to chemical adsorption. What’s more, Mulliken population analysis is applied to investigate the interaction between graphene and Li. According to the calculation results, it will provide a theoretical basis for the future application of graphene in lithium ion battery.

Quantum dynamics for Al-doped graphene composite sheet under hydrogen atom impact

From a micro view, the graphene composite exhibits the quantum dynamical behaviors in experiments. This paper aims to show the theoretical analysis on the quantum dynamics of Al-doped graphene composite sheet impacted by hydrogen using force analysis technique. As the main novelty of this study, the generalized Casimir function and power are proposed to analytically explore the key factors governing the quantum dynamics and energy exchange of Al-doped graphene composite sheet. The quantum system of Al-doped graphene composite sheet is converted into a Kolmogorov-like system, owning four types of force: inertial, internal, dissipative and external force. Numerical examples show the rich quantum dynamical phenomenon with different key parameters. It is found that the hydrogen excitation and initial conditions can effectively influence the quantum dynamical behaviors. Both theoretical predictions and numerical results attest to the quantum dynamics of the Al-doped graphene composite sheet under the impact from hydrogen atoms.

Molecular and dissociative adsorption of tetrachlorodibenzodioxin on M-doped graphenes (M = B, Al, N, P): pure DFT and DFT + VdW calculations.

Tetrachlorodibenzodioxin (TCDD) is one of the most famous dioxin families that is hazardous to humans and the environment. Designing cheap and novel catalysts for its detecting and removing is an essential need for the environment. In this work, DFT + VdW is used to investigate the potentiality of proposed catalysts in adsorbing and dissociating TCDD. P-type and N-type charge carrier effects on the adsorption process are modeled by doping of B/Al and N/P atoms in the graphene. Al-doped graphene, with - 1.27eV adsorption energy, has the highest possibility to adsorb TCDD. P-type dopants have higher interactions with TCDD in comparing with N-type dopants. Introducing positive and negative charges on the studied complexes shows that in all complexes, the driving force of complexation is π-π stacking except for the Al-doped graphene. Dissociative adsorption studies show that unlike literature data, chlorine atoms on the surface of studied catalysts are not dissociated from TCDD, and instead, C-O bonds in TCDD are dissociated symmetrically and asymmetrically. Data show that Al-doped graphene is the best catalyst for symmetrical dissociation, and pure graphene is the best one for asymmetrical dissociation of TCDD.

The adsorption enhancement of graphene for fluorine and chlorine from water

A high concentration of F (Cl) element in drinking water threatens people’s health. Hence, in this work, we systematically investigated the F and Cl atoms adsorption on pristine graphene (PG) or defective graphene (vacancy and Al, B, Si-doped) by using density functional theory calculations to explore materials with stronger adsorption performance for F and Cl elements removal from water. Based on the analysis of adsorption energy, PDOS and charge population, results indicate that F/Cl atom preferentially adsorbed on the Top site of graphene. We also find that the vacant graphene and doped graphene are good candidates for the adsorbents for F and Cl atom because the single F or Cl atom can be strongly trapped in the positions of defects. The negative adsorption energy and the diffusion barrier suggest that the F/Cl-AlG system has the most thermodynamic stability among our considered systems. In the H2O environment, the adsorption energy for the co-adsorption of F(Cl) atom and H2O molecule on Al-doped graphene is −4.2 eV(−3.77 eV), suggesting that the strong adsorption performance still presents between F(Cl) atom and Al-doped graphene in a background of H2O molecule.

Acetaldehyde adsorption and detection: A density functional theory study on Al-doped graphene

In this study, the Al-doped graphene structure was investigated as a sensor for the detection of acetaldehyde molecules at room temperature using density functional theory (DFT). The hybrid B3LYP method with 6-31G (d, p) basis set was used for all structural elements in the calculations. All structural and electronic properties were investigated. Among the properties studied, the charge distribution after adsorption has been determined to be the charge transfer from the acetaldehyde molecule to the cluster, and the electron acceptor in the system is an Al-doped graphene structure. However, it was found that the HOMO-LUMO gap decreased significantly after acetaldehyde molecule adsorption to the cluster. The results show that the acetaldehyde molecule with significant charge transfer and high adsorption energy can be adsorbed on the Al-doped graphene structure. As a conclusion, the electrical conductivity of Al-doped graphene structure increased with acetaldehyde adsorption. All these results show that the Al-doped graphene structure has the potential to be a sensor for the determination of acetaldehyde molecule at room temperature.

Single atom catalytic oxidation mechanism of formaldehyde on Al doped graphene at room temperature

Formaldehyde (HCHO) is one kind of common indoor toxic pollutant, the catalytic oxidation degradation of formaldehyde at room temperature is desired. In this work, a new single atomic catalyst (SAC), Al doped graphene, for the catalytic oxidation of HCHO molecules was proposed through density function theory (DFT) calculations. It is found that Al atoms can be adsorbed on graphene stably without aggression. Then HCHO can be effectively oxidized into CO2 and H2O in the presence of O2 molecules on Al doped graphene with a low energy barrier of 0.82 eV and releasing energy of 2.29 eV with the pathway of HCHO → HCOOH → CO → CO2. The oxidation reaction can happen promptly with reaction time τ = 56.9 s at the speed control step at room temperature. Therefore, this work proposed a high-performance catalyst Al-doped graphene without any noble metal for HCHO oxidation at ambient temperature, and corresponding oxidation pathway and mechanism are also deeply understood.

Hydrochlorofluorocarbons Adsorption on Undoped and Al-Doped Graphene Nanoflakes by Using Density Functional Theory (DFT) Study

Graphene nanoflakes used for detecting air pollutants are extremely needed for the sake of environmental protection. We investigated the Freon gas, R22, belonging to the group of Hydrochlorofluorocarbons considered to be very dangerous, due to their role in destructing of layer, and discussed the adsorption of R22 on the surface of pristine, one Al-atom and two Al-atoms doped Graphene Nanoflakes (GNFs). Besides, we have studied theoretically the geometrical optimization, electronic properties and adsorption of undoped and doped Graphene Nanoflakes. All calculations are based on the density functional theory (DFT). Results show that adding one atom or two atoms of aluminum to GNFs causes a big decrease in the energy gap; at the adsorption of Freon R22 molecules by two Al-atoms doped GNFs, the structure becomes less gas-sensitive than one Al-atom doped GNFs. The band gaps, density of states (DOS), dipole moments, total energies, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies have been calculated for undoped and doped with Al GNFs either with or without the Freon R22 gas molecules.

DFT study of small gas molecules adsorbed on undoped and N-, Si-, B-, and Al-doped graphene quantum dots

A theoretical study about the interaction between small gas molecules (H2O, CO, CO2, NH3, and CH4) with graphene quantum dots (GQDs) was performed. To develop gas sensors with ultralow detection levels, the nature of the bonds between the gas molecules and the GQDs should be understood and controlled. It was found that the binding energy (Eb) of the gas molecules with the GQDs can be controlled if the GQDs are doped. In the first part of the investigation, a choice of appropriated exchange/correlation functionals and basis sets was achieved. After this, the pure generalized gradient approximation (GGA) functionals, including the non-local (NL) density-dependent dispersion correction and the atom-pairwise dispersion correction (D3), were employed and found that they described accurately the Eb for the adsorption of water on GQDs. The use of NL and D3 corrected GGA functionals revealed that the Eb for the adsorption of H2O, CO, and NH3 on Si- and Al-doped GQDs can be improved, which indicates that the detection limit for the detection of these gases can be enhanced. To understand the nature of the bonds involved in the adsorption, different approaches were used, such as the quantum theory of atom in molecules and the electron localization function.

Theoretical investigation of the sensing mechanism of the pure graphene and AL,B,N,P doped mono-vacancy graphene-based methane

The interaction of CH4 gas molecule on pure graphene and Al, B, N, P doped mono-vacancy graphene by using the density functional theory (DFT) to explore their potential applications as gas sensors. The results demonstrate that the system of Al doped mono-vacancy graphene is the most stable, and Al-doped mono-vacancy graphene performs the largest adsorption energies upon CH4 with the most appreciable effects on the electronic structures. In addition, the adsorption of CH4 can largely enhance the conductivity of these graphene. In summary, we believe that the Al-doped mono-vacancy graphene could be a promising candidate material for the CH4 gas sensors.

Enhanced Photocatalytic Performance of Al-Doped ZnO NPs-Reduced Graphene Oxide Nanocomposite for Removing of Methyl Orange Dye from Water Under Visible-Light Irradiation

In this work, a series of Al-doped ZnO nanoparticles-reduced graphene oxide (AZO–RGO) nanocomposites were successfully synthesized by loading AZO nanoparticles (AZO NPs) on the graphene oxide sheets via in situ and low temperature solvothermal method. Several techniques were utilized to characterize the resultant nanocomposites including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and FT-Infra Red (FT-IR) analyses. SEM and TEM studies showed that AZO NPs have been formed on RGO surface, confirming the formation of AZO–RGO nanocomposites. XPS, FT-IR, and XRD analyses revealed that the oxygen-containing functional groups can prepare as anchoring sites for capturing AZO NPs on RGO surface. Moreover, it was observed that these nanoparticles have wurtzite structure. The photo-catalysis results showed that the 5% AZO–RGO nanocomposite has a higher efficiency than that of pure ZnO and ZnO–RGO samples for removing methyl orange dye from water under visible light irradiation. The enhancement in the photocatalytic activity can be attributed to the increase of surface area of AZO–RGO nanocomposites in comparison with pure ZnO. Furthermore, the existing of Al dopants and RGO sheets in the prepared samples can effectively decrease the charge recombination process in the AZO–RGO nanocomposites.

DFT study on the electronic structure and optical properties of N, Al, and N-Al doped graphene

The electronic structures and optical properties of pure, N-doped, Al-doped, and N-Al co-doped graphenes were studied by the first-principle calculation. The pure graphene is a zero bandgap semiconductor. The energy gaps were opened after N, Al, and N-Al doping. The gap value of N-Al co-doped graphene is the largest, 0.47 eV, then Al-doped graphene, 0.40 eV, and N-doped graphene, 0.21 eV. For N-doped graphene, carbon atom loses electrons, nitrogen atom gains electrons, while carbon gains electrons, aluminum atom loses electrons for Al-doped graphene. For N-Al co-doped graphene, aluminum atom loses a bit more electrons (2.31 e) than that in Al-doped graphene (2.27 e), while nitrogen atom gains a lot more electrons (−0.76 e) than that in N-doped graphene (−0.27 e). After N, Al, N-Al doping, the absorption peaks of graphene become weak, especially low frequency peaks of N and Al doping. The absorption curve of N-Al doped graphene is similar with that of pure graphene. However, the absorption peak of low frequency for N-Al doped graphene shifts to low energy relative to pure graphene, showing that it is easier for the transitions between π and π∗, and lead to the opened gap.