Carbon Nanotubes Sensors for Gases Detection in Oil Industry

One of the most important uses of carbon nanotubes (CNTs) as a nanosensor for variouspolluted gases resulting from the burning of petroleum derivatives containing sulfur compoundsor extracted from the gases associated with petroleum, which are isolated by heat.In this investigation, we tested the adhesion of gas molecules connected with oil: we examinedthe adhesion of gas molecules connected with oil: sulfur dioxide (SO2) and hydrogen sulphide(H2S) on the surface of ((5,0) zigzag and length (100 nm)) CNTs using DFT calculations toexplore the high sensitivity to nanosensor for these molecules, which have gotten awesomeconsideration because of environmental and industrial considerations.From the results obtained in this study geometry optimization (structural properties) fornanosensor for useful assention with trial information. While the electronic properties includedcalculate total energy, HOMO energies, LUMO energies, ionization potential, electron affinity,potential electronic chemical, electronegativity, electrochemical hardness and electronic softness,also, the energy gap of the sensors under study has been calculated and the energy gap varies asstated by the type of gases to be detected. Moreover, we used orbital analysis counting the DOSto finding out the possible orbital hybridization between molecules and CNTs. From theseresults, we can say that the CNTs under study ((5,0) zigzag and the length (100 nm)) has a highsusceptibility to being an effective nanosensor for the gas molecules connected with the oil. Thistype of sensor(CNTs/SO2 or H2S) is standout amongst those a large portion essentialpersonalprotective equipment that is to warn the person of the presence of gases associated with oil,especially in areas of normal gas extraction.

adsorption and capacity. In this way, gas sensors in light of nanomaterials, for example CNTs, nanowires, nanofibers, and nanoparticles, have been examined widely [7,8].
Carbon nanotubes, since been initially found by Iijima in 1991 [8], have drawn the most research intrigues due to their novel geometry, morphology, and properties. Their planning, properties, (for example, electronic, mechanical, warm, and optical properties), and applications on different fields are altogether examined seriously. Theoretical and simulation works have additionally been directed to comprehend this nanoscaled material and related wonder [9].
Carbon nanotubes have a place with the group of fullerene structures. There are two kinds of nanotubes: (SWCNTs) and (MWCNTs). A SWCNT can be considered as a one-molecule thick layer of graphite moved up into a consistent barrel with a measurement of a few nanometers, and length on the request of 1-100 microns [10]. MWCNTs comprise of various layers of graphite wrapped up together to frame a tube shape, having a similar focal hub. The structure of carbon nanotubes gives them naturally one of a kind electrical, physical, and chemical properties.
Mechanically, CNTs are the most grounded and stiffest strands that are known right now due to the C-C bond. Thermally, CNTs have high warm solidness in both vacuum and air. As far as electrical properties, CNTs can be either metallic or semiconducting, contingent on the tube breadth and the chirality (the bearing in which the graphite sheet is moved to shape the tube) [8,10]. The chirality is normally spoken to by a whole number combine (n,m). Nanotubes with (n-m=3j (j being a nonzero whole number) are metallic while all the others are semiconducting. The dielectric property of nanotubes is very anisotropic because of their about one-dimensional structures, which may empower nanotubes to convey high streams with immaterial warming impact [12,13]. The point of this work was to study the adsorption of associated petroleum gas molecules including H2S and SO 2 molecules on (0.5) zigzag SWCNT system. In order to explore the feasibility of using SWCNT as selective gas nanosensor, the energetic and electronic properties of the CNT with the gas molecules was investigated based on a first-principles of the DFT calculations.
For deeply understand the changes of electronic properties of SWCNT with above gas molecules, the DOS analysis was used test the impact of the associated petroleum gas molecules on electronic properties of CNT -based gas nanosensor. Figure 1 shows the structural relation between a graphene paper and a nanotube [13].

Theoretical Methods
Herein, we select the (5,0) CNT system as a model nanosensor, which consists 50 carbon atom, , 4.214 Å the diameter of the tube, 10 Å length of tube, and 1.42 Å the average length of the C-C bond.
The molecular properties of the compounds have been computed by DFT using the standard 6-31 G(d) basis set. In the DFT counts the Lee, Yang and Parr connection functional [15] is utilized together with Becke's three parameters [16] exchange practical B3LYP. Conformational investigation of the particles has been performed to have a thought regarding the most reduced vitality structures of the species. The geometry advancement was performed at the B3LYP DFT with a similar basis set [14,17].
Harmonic vibration frequencies were registered at a similar level of hypothesis. The cross breed practical B3LYP has appeared to be profoundly effective for count the electronic properties, for example, ionization possibilities, electronic states and vitality holes [18][19][20]. The DFT allotments the electronic vitality as E=E T + E V + E J + E XC , where E T , E V , and E J are the electronic active vitality, the electron atomic fascination and the electron-electron repugnance terms separately. makes DFT predominant over the regular HF system [14].
In this examination, the more relevant electronic potential (IP), electron affinities (EA), chemical potential (μ) it is the negative of electro negativity (χ), hardness (η) and softness (S) were calculated. The HOMO and LUMO vitality was also utilized to valuation the IP and EA in the scope of Koopmans' hypothesis [21,22]: Inside the scope of the DFT, one of the universal quantities is chemical potential (μ), which will   in(eV). Also, the calculations are included the DOS of CNTs.

Table (1) Electronic Properties of CNTs.
The total vitality E T of CNTs under stydy is very small as we see in Figure ( The above results are correspond to the S and η of the structures, the results showed that the CNT has large value of ƞ and small value of S, but, when sensing gases, the values are close and are indicative of the success of gas exploration work for the type of gases utilized as a part of this examination as we see in Figures (6 and 7). The calculated X refer to that the CNTs can interacts with other species in the medium, and means large escaping tendency as we see in The outcomes demonstrate an decline in the E g values when sensing the gases. This is an

Conclusions:
we have utilize DFT in this contemplate should acquire the geometry optimization and calculate some electronic properties of CNTs Sensors using B3LYP hybrid functional. The calculated electronic properties such as ionization potential, electron affinity, electro negativity, hardness, softness by using orbital-vertical method, the important conclusions are: 1-Geometry optimization for molecule has been found to a great assention with test data, while for other studied molecules SO 2 /CNT and H 2 S/CNT it has not been found a reference data.
2-The total vitality E T of CNTs under stydy is very small, this result is a reflection of the binding energy of each structure.

3-
The electronic properties (IP, EA, χ, η, S, ω) was calculated by using orbital-vertical system would a great concurred upon with test effect.