Identifying the Molecular Edge Termination of Exfoliated Hexagonal Boron Nitride Nanosheets with Solid-State NMR Spectroscopy and Plane-Wave DFT Calculations

Abstract

Hexagonal boron nitride nanosheets (h-BNNS), the isoelectric analog to graphene, have received much attention over the past decade due to their high thermal oxidative resistance, high bandgap, catalytic activity and low cost. The molecular functional groups that terminate boron and nitrogen zigzag and/or armchair edges directly affect their chemical, physical and electronic properties. However, an understanding of the exact molecular edge termination present in h-BNNS is lacking. Here, high-resolution magic-angle spinning (MAS) solid-state NMR (SSNMR) spectroscopy and plane-wave density-functional theory (DFT) calculations are used to determine the exact molecular edge termination in exfoliated h-BNNS. 1H→11B cross-polarization MAS (CPMAS) SSNMR spectra of h-BNNS revealed multiple hydroxyl/oxygen coordinate boron edge sites that were not detectable in direct excitation experiments. A dynamic nuclear polarization (DNP)-enhanced 1H→15N CPMAS spectrum of h-BNNS displayed four distinct 15N resonances while a 2D 1H{14N} dipolar-HMQC spectrum revealed three distinct 14N environments. Plane-wave DFT calculations were used to construct model edge structures and predict the corresponding 11B, 14N and 15N SSNMR spectra. Comparison of the experimental and predicted SSNMR spectra confirms that zigzag and armchair edges with both amine and boron hydroxide/oxide termination are present. The detailed characterization of h-BNNS molecular edge termination will provide usefulness for many material science applications and the techniques outlined here should be applicable to comprehensively understand the molecular edge terminations in other 2D materials.

Elucidating the Location of Cd2+ in Post-synthetically Treated InP Quantum Dots Using Dynamic Nuclear Polarization 31P and 113Cd Solid-State NMR Spectroscopy

“…The structural model put forwards on the basis of the sold-state NMR experiments is consistent with previous characterization of Cd-InP QDs by cadmium EXAFS which demonstrated Cd-O and Cd-P coordination 10. More generally this study highlights the utility of DNP SENS for the characterization of QDs and other nanomaterials [19][20][21][22][23][24][25][26][27][28][29][46][47][48][49][50][51][52].…”

“…The sensitivity of solid-state NMR experiments on QD and other nanomaterials can be improved by using DNP surface enhanced NMR spectroscopy (SENS). [19][20][21][22][23][24][25][26][27][28][29] To prepare QD samples for a DNP SENS experiment a colloidal solution of QD is dispersed on a support material, either mesoporous silica 24 or hexagonal boron nitride (h-BN) 27 and then a PA solution is added. Alternatively, to further increase NMR sensitivity the QD can be precipitated from solution, physically mixed with h-BN, then impregnated with a minimal volume of PA solution.…”

Enhanced and stabilized hydrogen production from methanol by ultrasmall Ni nanoclusters immobilized on defect-rich h-BN nanosheets

“…Such edges form step-like structures in the BN nanoflakes, hereafter referred to as “pits.” However, the nanocluster adsorption site preference is size dependent. Larger Ni clusters (Ni 38 ) have a stronger interaction with the pristine surface than with the defected surface (0.44 V BN3 :O/nm 2 ), with adsorption energies of −4.25 and −3.53 eV, respectively, which further increase to −4.98 eV when nearby N-H–terminated edges are present ( 65 ), as in the pit structures (see Fig. 1 and SI Appendix , Fig.…”

Computational Study on the Adsorption of H2SiCl2 by Pristine, Al-, and Ga-Doped Boron Nitride Nanosheets: A DFT Study

“…BNNS is also a very successful nanosorbent and has been studied in many theoretical studies to detect H2O [35] NO [36], CO [37], CH2O [38], COCl2 [39], C2H4 [40], and N2O [41]. This nanosheet and metal decorated BNNS have also been used in the manufacture of many electronic devices [42][43][44][45][46][47][48]. It can also be used as a valuable material in the coating industry and metal protection because it is impermeable to gases and liquids and is also an electrical insulator [49][50][51][52].…”