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Effect of mono-vacant defects on the opto-electronic properties of ionic liquid functionalized hexagonal boron-nitride nanosheets

Shakourian Fard, M ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1016/j.molliq.2017.11.140
  3. Abstract:
  4. We compare and contrast the physisorption behavior of imidazolium and butyltrimethylammonium based ionic liquids (ILs) on mono-vacant nitrogen and boron defective hexagonal boron nitride nanoflakes (h-BNNF) using M06-2X/cc-pVDZ level of theory. The presence of defects on the nanoflakes results in an increase in IL binding energy by ~ 1–27 kcal/mol partly due to the lowering of the energy band in the defective nanoflakes. Imidazolium based ILs adsorb energetically more favorably on h-BNNF-VB than on h-BNNF-VN while butyltrimethylammonium based ILs prefer to adsorb on h-BNNF-VN. Upon adsorption of imidazolium ILs on the nanoflakes, an increase in both HOMO and LUMO orbital energies is observed - resulting in net increase in HOMO-LUMO energy gap (Eg) value and chemical hardness (η). On the other hand, the adsorption of butyltrimethylammonium ILs leads to an increase in HOMO energy and a decrease in LUMO energy of the h-BNNF-VB nanoflake thereby lowering the Eg and η values of defective nanoflakes. The absorption spectra of mono-vacant surfaces undergo shifts upon IL adsorption. The first absorption peak at 296 nm is red-shifted while the second absorption peak at 421 nm is blue-shifted. The magnitude of the first absorption peak for the h-BNNF-VB…IL complexes follow the order of h-BNNF-VB…[Btma][Y] > h-BNNF-VB…[Bmim][Y] (Y = BF4 −, PF6 −, Tf2N−) consistent with greater binding energies and energy gaps of imidazolium based complexes in comparison to their butyltrimethylammonium counterparts. Generally, it is concluded that the modulation of opto-electronic properties of IL-functionalized h-BNNF surfaces is largely provided by the defects and to a lesser extent by the choice of IL. © 2017 Elsevier B.V
  5. Keywords:
  6. Boron vacancy ; Ionic liquid ; Mono-vacant defects ; Nitrogen vacancy ; Adsorption ; Bins ; Boron nitride ; Complexation ; Defects ; Electronic properties ; Energy gap ; Ionic liquids ; Liquids ; Nitrides ; Nitrogen ; Chemical hardness ; Hexagonal boron nitride ; HOMO-LUMO energy gap ; Imidazolium-based ; Ionic liquid (ils) ; Nitrogen vacancies ; Non-covalent interaction ; Optoelectronic properties ; Binding energy
  7. Source: Journal of Molecular Liquids ; Volume 249 , 2018 , Pages 1172-1182 ; 01677322 (ISSN)
  8. URL: https://www.sciencedirect.com/science/article/pii/S0167732217334682