Structural and electronic properties of SnS2 stacked nanosheets: An ab-initio study H.B. Mabiala-Poatya,b,∗, D.H. Doumaa,b, B. M'Passi-Mabialaa,b, R.E. Mapashac aGroupe de Simulations Numériques en Magnétisme et Catalyse (GSMC), Faculté des Sciences et Techniques, Université Marien Ngouabi, BP 69, Brazzaville, Congo bUnité de Recherche en Nanomatériaux et Nanotechnologies, Institut National de Recherche en Sciences Exactes et Naturelles (IRSEN), Brazzaville, Congo cDepartment of Physics, University of Pretoria, Pretoria, 0002, South Africa
A R T I C L E I N F O
Keywords: DFT Nanosheets VanderWaals exchangecorrelation functionals Electronic structure 2D materials SnS2
We present an ab-initio study of the structural and electronic properties of SnS2 stacked nanosheets using the standard LDA andGGAfunctionals aswell asthe newly developedvariants ofthe non-local vanderWaals(vdW) exchange correlation functionals, namely vdW-DF-revPBE and vdW-DF2-C09. We have examined diﬀerent stacking conﬁgurations of the two, three and four SnS2 layers. The GGA-PBE functional fails to describe the interlayer binding energies and interlayer spacing of SnS2 nanosheets, while a good agreement is observed between the calculated and available experimental values when the van der Waals corrected functionals are used, mostly the vdW-DF2-C09. It is found that the interlayer interactions in the SnS2 ﬁlms are not only vdW type but, the overlap of wave functions of neighboring layers have to be taken into account. We have observed a systematic reduction in the band gap with the increase in the number of stacked layers.
Augustin Aimé LEBONGUY 1, Joseph GOMA-TCHIMBAKALA 1, 2 * et Simon KELEKE 3
1 Institut National de Recherche en Sciences Exactes et Naturelles, Laboratoire de Microbiologie Appliquée et de Biologie Moléculaire, BP 2400 Brazzaville, Congo 2 Université Marien Ngouabi, Ecole Nationale Supérieur e d’Agronomie et de Foresterie, BP 69 Brazzaville, Congo 3 Institut National de Recherche en Sciences Exactes et Naturelles, URR Microbiologie, BP 1286 Pointe - Noire, Congo
Mots-clés : Pseudomonas aeruginosa , tolérance, multirésistance, polluants.
Abstract Metals, hydrocarbons, and antibiotics tolerance of two neutrophilic
aeruginosa strains isolated from diesel oil
The objective of this study is to evaluate the multi-resistance to hydrocarbons, metals and antibiotics of Pseudomonas aeruginosa G2 and G3 strains isolated from diesel oil. pH and NaCl concentration effect on growth of both strains in liquid medium was previously studied. Results show that both strains are neutrophils. P. aeruginosa G2 strain tolerates up to 40 g / L NaCl while G3 strain tolerates less than 20 g / L. Hydrocarbon tolerance study by spot and agar diffusion methods shows that both strains tolerate 100 % diesel and SAE 90 oil. However, gasoline, toluene and xylene inhibit the growth of P. aeruginosa G3 while only xylene inhibits the growth of P. aeruginosa G2. Both P. aeruginosa G2 and G3 strains are resistant to CuCl2, SnCl2, NiCl2, CoCl2, ZnSO4 and SnCl2, ZnSO4, FeSO4, respectively. Finally, antibiotic resistance study shows
159 Afrique SCIENCE 14(5) (2018) 158 - 170
Augustin Aimé LEBONGUY et al.
that both strains are resistant to ampicillin and spiramycin but sensitive to chloramphenicol at 0.5 ‰. Only P. aeruginosa G2 strain is resistant to kanamycin. Thus, this study shows that both strains of P. aeruginosa are multi-resistant to hydrocarbons, metals and antibiotics. These characteristics are very important in their potential use in bioremediation of co-contaminated sites by these pollutants.
Keywords : Pseudomonas aeruginosa, tolerance, multi - resistance, p ollutants.