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In the current study, the density function theory (DFT) is used to investigate the chemical adsorption strength of NO2 gas molecule. The relaxation structure, molecular orbital energy, energy gap and adsorption energy are calculated at ground state. The time dependent DFT (TD-DFT) used to simulate excitation provides UV-Visible spectrum. There was a perpendicular geometrical orientation of the gas molecule around the surface and an adsorption distance of 2.58 Å. The adsorption distance shows the chemical reaction between the gas molecule and the surface. The result of adsorption energy indicates that the gas molecule that closed to the surface has high interaction and it decreases gradually when gas molecule goes further from the graphene nano-ribbon surface. The UV-Visible measurement indicates that the system interaction with gas molecule has red shifting in electromagnetic radiation. The final result concludes that graphene nano-ribbon has high reactivity for NO2 gas molecule. The theoretical calculations provide the ability to design optical sensor which has useful applications in an environmental monitoring.

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Current work deals with the structural and electronic properties of the cis-platin by employing the B3LYP density functional theory with SDD basis sets at the Gaussian 09 package of programs. We showed a good relax was obtained for the cis-platin. The great contribution for constructing the molecular orbitals is due to the outer electrons in the platinum metal with few contributions from the p-orbitals of the ligands, cis-platin has insulating behavior. Also, the cis-platin has low electronic softness and it needs high excitation energy to electron transfer or to accepting an electron from the surrounding species.

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.