Density Functional Theory Study of O 2 and NO Adsorption on Heteroatom-Doped Graphenes Including the van der Waals Interaction (original) (raw)
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The European Physical Journal B, 2010
In this paper we have investigated the adsorption of the gas molecules (NO2, NO) on graphene, using first-principles methods. For full geometric relaxation of the molecules in the vicinity of a graphene sheet, we obtain the adsorption geometry, adsorption energies, charge transfer and density of states (DOS). We can identify which of the adsorbate molecules is acting as donor or acceptor. We find that the conductance of graphene at the Fermi level decreases with adsorbing NO2 molecules and increases with adsorbing NO molecules.
APPLIED PHYSICS OF CONDENSED MATTER (APCOM 2019)
The paper reviews the state of the art of graphene employed as an active layer in chemiresistive gas sensors. Graphene properties such as high specific surface area, low noise, planar structure, flexibility, etc., are commonly highlighted as strengths in the sensors technology. However, the listed virtues are mostly related to the pristine graphene or even graphene monolayers, while majority of devices use chemically synthesized graphene derivatives. These vague statements may be induced by the high level of graphene hype and racing for the research grants. Moreover, graphene has no dangling bonds functioning as prime reaction agents. This led us to propose more adequate view onto a capacity of graphene in the area of gas sensors. In this study, we focused onto three aspects: (i) the substantiation of the low noise for sensing devices, (ii) the assumed versus actual surface area of the real graphene layers, and (iii) an integration of graphene sensors into silicon circuits.
Bilayer Graphene Application on NO2 Sensor Modelling
Journal of Nanomaterials, 2014
Graphene is one of the carbon allotropes which is a single atom thin layer with sp 2 hybridized and two-dimensional (2D) honeycomb structure of carbon. As an outstanding material exhibiting unique mechanical, electrical, and chemical characteristics including high strength, high conductivity, and high surface area, graphene has earned a remarkable position in today's experimental and theoretical studies as well as industrial applications. One such application incorporates the idea of using graphene to achieve accuracy and higher speed in detection devices utilized in cases where gas sensing is required. Although there are plenty of experimental studies in this field, the lack of analytical models is felt deeply. To start with modelling, the field effect transistor-(FET-) based structure has been chosen to serve as the platform and bilayer graphene density of state variation effect by NO 2 injection has been discussed. The chemical reaction between graphene and gas creates new carriers in graphene which cause density changes and eventually cause changes in the carrier velocity. In the presence of NO 2 gas, electrons are donated to the FET channel which is employed as a sensing mechanism. In order to evaluate the accuracy of the proposed models, the results obtained are compared with the existing experimental data and acceptable agreement is reported.
Ab initio study on gas sensing properties of group III (B, Al and Ga) doped graphene
Computational Condensed Matter, 2016
The adsorptions of small gas molecules (CO, NO and NO 2) on group III (B, Al and Ga) doped graphene are investigated using ab initio density functional theory calculations, to exploit the potential applications of graphene as toxic gas sensors. For enabling practical gas sensing applications, the effect of water vapour on the sensing properties of these doped graphenes are also studied. The most stable geometries of gas molecules on these doped graphenes are determined and the adsorption energies are calculated. Our results show that the structural and electronic properties of B-doped graphene are sensitive to NO and NO 2 , but not influenced by the adsorption of CO and H 2 O. The chemisorptions of CO, NO, NO 2 and H 2 O on Al-and Ga-doped graphene were evident from large adsorption energies, large charge transfers and were confirmed by analysis of band structures and density of states. Hence Al-and Ga-doped graphenes can be used as good sensors for detecting CO, NO and NO 2. The calculations also indicate that B-doped graphene can be used as an excellent gas sensing platform for detecting NO and NO 2 , whereas Al-and Ga-doped graphene may not be suitable choices for harmful gas detection, in the presence of water vapour.
Chemical Physics, 2012
The effect of SiO 2 substrate and van der Waals interactions on the adsorption of NO 2 molecule on graphene is studied using density functional theory. Contrary to physisorption on suspended graphene, both physisorption and chemisorption phenomena can be found, which are mainly caused by the covalent CO bonds, the broken symmetry, and the local corrugations induced by SiO 2. The electronic structures of the system are significantly influenced after NO 2 adsorption, enhancing the detection of NO 2. Interestingly, NO 2 induces magnetization into graphene, and the spin polarization locates mainly on carbon atoms of graphene. The barrier of the transition from physisorption to chemisorption is about 0.05 eV, and this ''pseudo barrier'' can be overcome by van der Waals interactions. This work explains the experiments of graphene as gas sensors with high sensitivity, and supports new applications for electronic, spintronic devices.
Recent Advances on Graphene-Based Gas Sensors
Russian Journal of Physical Chemistry A, 2020
Owing to its unprecedented structural, electronic and mechanical properties, graphene, a singleatomic sheet of carbon atoms, is effectively used to detect chemical species. In this work, adsorption of gaseous molecules, mainly toxic (NO 2 , NO, NH 3 , CO, CO 2 , HF, H 2 S, etc.) and volatile organic compounds (VOCs), on graphene and modified graphene (GO, rGO) has been reviewed. The gas sensing ability of graphene is enhanced by doping with heteroatoms, and functionalizing it with many groups, such as hydroxyl, epoxy, etc. Recent advances in detection of gaseous molecules by graphene and modified graphene, coupled with metal and metal oxide nanoparticles, which have high response and better sensitivity than metal and metal oxide NPs because of high surface area and increased electronic charge transfer, have also been reported.
Investigation of NO 2 adsorption on reduced graphene oxide
Chemical Physics Letters, 2015
The adsorption of NO 2 on reduced graphene oxide (RGO) is investigated using in situ infrared microspectroscopy and density functional theory (DFT) calculations. NO 2 /RGO differential absorption spectra show a broadband modulation and the appearance of several vibrational absorption bands, indicating several coexisting adsorbate species. We find that NO 2 molecules react with native epoxide groups to form nitrate species. Consequently, the effect of NO 2 is, partially, to remove epoxide groups and their distortion of the low-energy electronic structure of graphene, while simultaneously hole-doping the substrate. These results are discussed and related to recent reports on the gas-sensing behavior of RGO.
Detection of individual gas molecules adsorbed on graphene
Nature Materials, 2007
The ultimate aspiration of any detection method is to achieve such a level of sensitivity that individual quanta of a measured value can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity [1-4]. The fundamental reason limiting the resolution of such sensors is fluctuations due to thermal motion of charges and defects [5] which lead to intrinsic noise exceeding the sought-after signal from individual molecules, usually by many orders of magnitude. Here we show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphene's surface. The adsorbed molecules change the local carrier concentration in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chemical detectors but also for other applications where local probes sensitive to external charge, magnetic field or mechanical strain are required.
A first-principles study on gas sensing properties of graphene and Pd-doped graphene
Applied Surface Science, 2015
Sensitivity of pristine graphene (PG) and Pd-doped graphene (Pd-G) toward a series of small gas molecules (CO, NH 3 , O 2 and NO 2 ) has been investigated by first-principles based on density functional theory (DFT). The most stable adsorption configuration, adsorption energy, charge transfer, density of states and magnetic moment of these molecules on PG and Pd-G are thoroughly discussed. It is found that four gas molecules are weakly adsorbed on PG with low adsorption energy of 0.08-0.24 eV, and the electronic properties of PG are only sensitive to the presence of O 2 and NO 2 molecules. In contrast, doping graphene with Pd dopants significantly enhances the strength of interaction between adsorbed molecules and the modified substrate. The dramatically increased adsorption energy and charge transfer of these systems are expected to induce significant changes in the electrical conductivity of the Pd-G sheet. The results reveals that the sensitivity of graphene-based chemical gas sensors could be drastically improved by introducing the Pd dopants, so Pd-G is more suitable for gas molecules detection compared with PG.
Analytical Approach to Study Sensing Properties of Graphene Based Gas Sensor
Sensors, 2020
Over the past years, carbon-based materials and especially graphene, have always been known as one of the most famous and popular materials for sensing applications. Graphene poses outstanding electrical and physical properties that make it favorable to be used as a transducer in the gas sensors structure. Graphene experiences remarkable changes in its physical and electrical properties when exposed to various gas molecules. Therefore, in this study, a set of new analytical models are developed to investigate energy band structure, the density of states (DOS), the velocity of charged carriers and I-V characteristics of the graphene after molecular (CO, NO2, H2O) adsorption. The results show that gas adsorption modulates the energy band structure of the graphene that leads to the variation of the energy bandgap, thus the DOS changes. Consequently, graphene converts to semiconducting material, which affects the graphene conductivity and together with the DOS variation, modulate veloci...