Surface Of Hexagonal Boron Nitride Research Articles

Probing structural superlubricity of two-dimensional water transport with atomic resolution.

Low-dimensional water transport can be drastically enhanced under atomic-scale confinement. However, its microscopic origin is still under debate. In this work, we directly imaged the atomic structure and transport of two-dimensional water islands on graphene and hexagonal boron nitride surfaces using qPlus-based atomic force microscopy. The lattice of the water island was incommensurate with the graphene surface but commensurate with the boron nitride surface owing to different surface electrostatics. The area-normalized static friction on the graphene diminished as the island area was increased by a power of ~-0.58, suggesting superlubricity behavior. By contrast, the friction on the boron nitride appeared insensitive to the area. Molecular dynamic simulations further showed that the friction coefficient of the water islands on the graphene could reduce to <0.01.

Sharp zero-phonon lines of single organic molecules on a hexagonal boron-nitride surface

Single fluorescent molecules embedded in the bulk of host crystals have proven to be sensitive probes of the dynamics in their nano environment, thanks to their narrow (about 30–50 MHz or 0.1–0.2 μeV) optical linewidth of the 0-0 zero-phonon line (0-0 ZPL) at cryogenic temperatures. However, the optical linewidths of the 0-0 ZPL have been found to increase dramatically as the single molecules are located closer to a surface or interface, while no 0-0 ZPL has been detected for single molecules on any surface. Here we study single terrylene molecules adsorbed on the surface of hexagonal boron-nitride (hBN) substrates. Our low-temperature results show that it is possible to observe the 0-0 ZPL of fluorescent molecules on a surface. We compare our results for molecules deposited on the surfaces of annealed and non-annealed hBN flakes and we see a marked improvement in the spectral stability of the emitters after annealing.

Liquid-activated quantum emission from pristine hexagonal boron nitride for nanofluidic sensing.

Liquids confined down to the atomic scale can show radically new properties. However, only indirect and ensemble measurements operate in such extreme confinement, calling for novel optical approaches that enable direct imaging at the molecular level. Here we harness fluorescence originating from single-photon emitters at the surface of hexagonal boron nitride for molecular imaging and sensing in nanometrically confined liquids. The emission originates from the chemisorption of organic solvent molecules onto native surface defects, revealing single-molecule dynamics at the interface through the spatially correlated activation of neighbouring defects. Emitter spectra further offer a direct readout of the local dielectric properties, unveiling increasing dielectric order under nanometre-scale confinement. Liquid-activated native hexagonal boron nitride defects bridge the gap between solid-state nanophotonics and nanofluidics, opening new avenues for nanoscale sensing and optofluidics.

Performance of Common Density Functionals for Excited States of Tetraphenyldibenzoperiflanthene.

Time-dependent density functional theory is the method of choice to efficiently calculate excitation spectra with the functional and basis set choice allowing one to compromise between accuracy and computational cost. In this work, the performance of different functionals as well as the second-order approximate coupled cluster singles and doubles model CC2 is evaluated by comparing the results to experimental results of the example molecule tetraphenyldibenzoperiflanthene (DBP). The choice of the functional has a significant impact on the calculated spectrum of DBP. The performance of a number of different functionals was evaluated, quantified, and, where possible, discussed. The best functional, tuned-CAM-B3LYP, is used to investigate DBP on a surface of hexagonal boron nitride (h-BN). The resulting spectrum shows excellent agreement with experimental results for a monolayer of DBP on h-BN.

The Temperature Dependence of the Hexagonal Boron Nitride Oxidation Resistance, Insights from First-Principle Computations.

In this work, we studied the oxidation stability of h-BN by investigating different variants of its modification by -OH, -O- and -O-O- groups using an atomistic thermodynamics approach. We showed that up to temperatures of ~1700 K, oxygen is deposited on the surface of hexagonal boron nitride without dissociation, in the form of peroxide. Only at higher temperatures, oxygen tends to be incorporated into the lattice of hexagonal boron nitride, except in the presence of defects Nv, when the embedding occurs at all temperatures. Finally, the electronic and magnetic properties of the oxidized h-BN were studied.

Antibacterial, UV-Protective, Hydrophobic, Washable, and Heat-Resistant BN-Based Nanoparticle-Coated Textile Fabrics: Experimental and Theoretical Insight.

The use of nanoparticles (NPs) to modify the surface of cotton fabric is a promising approach to endowing the material with a set of desirable characteristics that can significantly expand the functionality, wear comfort, and service life of textile products. Herein, two approaches to modifying the surface of hexagonal boron nitride (h-BN) NPs with a hollow core and a smooth surface by treatment with maleic anhydride (MA) and diethylene triamine (DETA) were studied. The DETA and MA absorption on the surface of h-BN and the interaction of surface-modified h-NPs with cellulose as the main component of cotton were modeled using density functional theory with the extended Perdew-Burke-Ernzerhof functional. Theoretical modeling showed that the use of DETA as a binder agent can increase the adhesion strength of BN NPs to textile fabric due to the simultaneous hydrogen bonds with cellulose and BN. Due to the difference in zeta potentials (-38.4 vs -25.8 eV), MA-modified h-BN NPs form a stable suspension, while DETA-modified BN NPs tend to agglomerate. Cotton fabric coated with surface-modified NPs exhibits an excellent wash resistance and high hydrophobicity with a water contact angle of 135° (BN-MA) and 146° (BN-DETA). Compared to the original textile material, treatment with MA- and DETA-modified h-BN NPs increases heat resistance by 10% (BN-MA fabric) and 15% (BN-DETA fabric). Cotton fabrics coated with DETA- and MA-modified BN NPs show enhanced antibacterial activity against Escherichia coli U20 and Staphylococcus aureus strains and completely prevent the formation of an E. coli biofilm. The obtained results are important for the further development of fabrics for sports and medical clothing as well as wound dressings.

Selective adsorption desulfurization by single Al atom anchoring on the surface of hexagonal boron nitride through S[sbnd]Al coordination

A concept of single atom adsorbents (SAAs) is proposed to the fields of highly selective adsorption desulfurization from diesel. Here, SAAs with the Al atom anchoring on the surface of hexagonal boron nitride have been systematically explored by density functional theory. Firstly, all the possible doping sites have been considered and their stabilities have been discussed by the doped energy. Additionally, the activity and selectivity for the adsorptive desulfurization of these Al-based SAAs have been predicted. Results show that all the Al-based SAAs can enhance the activity and selectivity of adsorptive desulfurization due to the newly formed S-Al coordination bond. We hope this work can provide a reliable theoretical foundation for the design of SAAs with higher adsorptive activity and superior selectivity.

Chitosan functionalized hexagonal boron nitride nanomaterial to enhance the anticorrosive performance of epoxy resin

A simple method was used to load theγ-Aminopropyl triethoxysilane (KH550) modified chitosan (CS) on the surface of hexagonal boron nitride(HBN) modified with polydopamine (PDA). The prepared material (HP-CS) was added into epoxy resin to fabricate high-efficiency anti-corrosion coating. Various characterization methods were used to study the dispersion and interfacial interaction of HP-CS in epoxy resin. In addition, electrochemical impedance spectroscopy (EIS) test results demonstrated that HP-CS/EP coating had good corrosion resistance, and the impedance modulus reached 8.83 × 109 Ω cm2. Furthermore, the impedance modulus of HP-CS/EP coating was about 2 orders of magnitude higher than the pure EP coating after 30 days of immersion.

Electronic Structure of Graphene on the Hexagonal Boron Nitride Surface: A Density Functional Theory Study

Poor electron-related cutting current in graphene-based field-effect transistors (FETs) can be solved by placing a graphene layer over a hexagonal boron nitride (BN) substrate, as established by Giovannetti et al. and other researchers. In order to produce high-quality results, this investigation uses 2 × 2 cells (~2.27% mismatch), given that larger cells lead to more favourable considerations regarding interactions on cell edges. In this case, the substrate-induced band gap is close to 138 meV. In addition, we propose a new material based on graphene on BN in order to take advantage of the wonderful physical properties of both graphene and BN. In this new material, graphene is rotated with respect to BN, and it exhibits a better mismatch, only ~1.34%, than the 1 × 1-graphene/1 × 1-BN; furthermore, it has a very small bandgap, which is almost zero. Therefore, in the bands, there are electronic states in cone form that are like the Dirac cones, which maintain the same characteristics as isolated graphene. In the first case (2 × 2-graphene/2 × 2-BN), for example, the resulting band gap of 138 meV is greater than Giovannetti’s value by a factor of ~2.6. The 2 × 2-graphene/2 × 2-BN cell is better than the 1 × 1-graphene/BN one because a greater bandgap is an improvement in the cutting current of graphene-based FETs, since the barrier created by the bandgap is larger. The calculations in this investigation are performed within the density functional theory (DFT) theory framework, by using 2 × 2-graphene/2 × 2-BN and 13 × 13-graphene/23 × 23-(0001) BN cells. Pseudopotentials and the generalized gradient approximation (GGA), combined with the Perdew–Burke–Ernzerhof parametrization, were used. Relaxation is allowed for all atoms, except for the last layer of the BN substrate, which serves as a reference for all movements and simulates the bulk BN.

Registry-Dependent Peeling of Layered Material Interfaces: The Case of Graphene Nanoribbons on Hexagonal Boron Nitride

Peeling of layered materials from supporting substrates, which is central for exfoliation and transfer processes, is found to be dominated by lattice commensurability effects in both low and high velocity limits. For a graphene nanoribbon atop a hexagonal boron nitride surface, the microscopic peeling behavior ranges from stick-slip, through smooth-sliding, to pure peeling regimes, depending on the relative orientation of the contacting surfaces and the peeling angle. The underlying mechanisms stem from the intimate relation between interfacial registry, interlayer interactions, and friction. This, in turn, allows for devising simple models for extracting the interfacial adhesion energy from the peeling force traces.

Investigation of Interaction of Noble Metals (Cu, Ag, Au, Pt and Ir) with Nanosheets.

Two-dimensional nanomaterials, such as graphene and hexagonal boron nitride nanosheets, have attracted tremendous interest in the research community and as a starting point for the development of nanotechnology. Using classical applied mathematical modeling, we derive explicit analytical expressions to determine the binding energies of noble metals, including copper, silver, gold, platinum and iridium (Cu, Ag, Au, Pt and Ir) atoms, on graphene and hexagonal boron nitride nanosheets. We adopt the 6–12 Lennard–Jones potential function, together with the continuous approach, to determine the preferred minimum energy position of an offset metal atom above the surface of the graphene and hexagonal boron nitride nanosheets. The main results of this study are analytical expressions of the interaction energies, which we then utilize to report the mechanism of adsorption of the metal atoms on graphene and hexagonal boron nitride surfaces. The results show that the minimum binding energy occured when Cu, Ag, Au, Pt and Ir were set at perpendicular distances in the region from 3.302 Å to 3.683 Å above the nanosheet surface, which correspond to adsorption energies in the region ranging from 0.842 to 2.978 (kcal/mol). Our results might assist in providing information on the interaction energies between the metal atoms and the two-dimensional nanomaterials.

Atomic layer deposited boron nitride nanoscale films act as high temperature hydrogen barriers

Hydrogen environmental barrier coatings reduce hydrogen diffusion and concomitant hydrogen embrittlement of materials such as those used in nuclear and fuel cell applications where hydrogen is used as a fuel source. In this work, atomic layer deposition (ALD) was used to coat substrates with boron nitride (BN) films of approximately 6, 8, and 15 nm thicknesses. Differential thermal analysis of the coated samples in hydrogen gas showed resistance to reaction with hydrogen to at least 1713 K. Diffusion of atomic hydrogen into the hexagonal BN (001) surface and between sheets as well as material stability were computationally studied using density functional theory. A high activation energy of 3.25 eV was calculated for atomic hydrogen diffusion into the (001) hexagonal BN surface through a sheet. However, lower activation energies of 1.35 eV, 1.11 eV, and 0.12 eV were computed for unique hydrogen diffusion pathways between sheets, suggesting that sheet orientation parallel to the substrate surface is vital for attaining desirable barrier film properties. A predicted positive nitrogen vacancy formation energy of 4.3 eV at 2773 K suggests that hexagonal BN is stable at nuclear thermal propulsion operating temperatures, and stability was confirmed experimentally up to 1773 K.

Simultaneous exfoliation and functionalization of hexagonal boron nitride in the aqueous phase for the synthesis of high-performance wastewater treatment membrane

A highly permselective membrane is needed for environmental applications due to current industrialization and environmental constraints. However, membrane fouling and firmness problems are encountered during operation in harsh working environments. Hexagonal boron nitride is an encouraging material due to its solidity under various working conditions, but exfoliation using environmentally friendly techniques is challenging. In this study, aqueous-phase exfoliation using tannic acid was demonstrated to be an easy, novel, and green method for preparing functionalized two-dimensional hexagonal boron nitride nanosheets. Microscopic and spectroscopic techniques were used to characterize the exfoliated nanosheets and the synthesized membrane. Tannic acid is adsorbed on the hexagonal boron nitride surface and gradually exfoliates the hexagonal boron nitride to release a few layers of functionalized boron nitride nanosheets; it behaves as a green surfactant by weakening the interlayer interactions. Ultimately, the functionalized exfoliated nanosheets are used to prepare a membrane for environmental applications. Fascinatingly, the prepared membrane is exceedingly stable in water and organic solvents and manifests adequate efficiency in transporting solvents with excellent screening of solutes and long-term antifouling performance. The synthesized membrane's rapid transport of solvents and ample separation efficiency of solutes may be due to the robust nanochannel and thin laminar networks of the nanosheets, which endow the membrane with favorable properties for separation and decontamination developments.

Catalytic Effect of Ti or Pt in a Hexagonal Boron Nitride Surface for Capturing CO2

We investigated the effect of doping a hexagonal boron nitride surface (hBN) with Ti or Pt on the adsorption of CO2. We performed first-principles molecular dynamics simulations (FPMD) at atmospheric pressure, and 300 K. Pristine hBN shows no interaction with the CO2 molecule. We allowed the Ti and Pt atoms to interact separately, with either a B-vacancy or an N-vacancy. Both Ti and Pt ended chemisorbed on the surface. The system hBN + Ti always chemisorbed the CO2 molecule. This chemisorption happens in two possible ways. One is without dissociation, and in the other, the molecule breaks in CO and O. However, in the case of the Pt atom as dopant, the resulting system repels the CO2 molecule.

Self-regulated catalysis for the selective synthesis of primary amines from carbonyl compounds

An Ru catalyst supported on the edge surface of hexagonal boron nitride (Ru/BN-e) demonstrates self-acceleration kinetics in the reductive amination reactions of carbonyl compounds under a low ammonia-to-substrate ratio.

Synthesis of PDA-BN@f-Al2O3 hybrid for nanocomposite epoxy coating with superior corrosion protective properties

A novel PDA-BN@f-Al2O3 nanohybrid was synthesized by depositing Al2O3 nanoparticles modified with γ -Aminopropyltriethoxysilane (KH550) on the surface of hexagonal boron-nitride (h-BN) sheets covered with polydopamine (PDA). Then, PDA-BN@f-Al2O3 hybrids was dispersed in epoxy resin to prepare composite coating samples. Many characterizations revealed that the functionalized Al2O3 successfully deposited on the surface of PDA-BN platelets and PDA-BN@f-Al2O3 hybrids showed good dispersibility in the epoxy resin, and the interfacial adhesion between hybrids and epoxy matrix was improved. Furthermore, the effects of Al2O3, h-BN and various mixtures of PDA-BN@f-Al2O3 hybrids at a low weight fraction of 1 % on the corrosion resistance of epoxy coating were studied by electrochemical measurement and salt spray test. The potentiodynamic polarization test revealed that PDA-BN@f-Al2O3 hybrids have a corrosion inhibitive performance. Moreover, the coating resistance of PDA-BN@f-Al2O3 (3:1)/epoxy was enhanced by three orders of magnitude compared with neat epoxy after 5 d immersion. This study provides a promising application prospect for the development of superior metal protective organic coatings.

Wettability of nanostructured hexagonal boron nitride surfaces: molecular dynamics insights on the effect of wetting anisotropy.

Nanostructured van der Waals (vdW) layered materials hold great potential for achieving smart surfaces with controllable wettability. Inspired by this possibility, we conduct Molecular Dynamics (MD) simulations of the wetting of nanostructured hexagonal boron nitride (hBN) surfaces. The nanostructure consists of periodically placed nanopillars made of hBN nanoribbons. We demonstrate that the polarity effect of the nanoribbon edges triggers wetting anisotropy of the nanoribbons: the vertical edges of the nanoribbons demonstrate a different wetting behavior as compared to the flat surfaces of the nanoribbons. Depending on the nature of the edge of the nanoribbon (armchair or zigzag), these vertical edges can be more hydrophilic for the zigzag edges or more hydrophobic for the armchair edges than the flat part. Such differences ensure that the nanostructured hBN surfaces become more hydrophilic (hydrophobic) as compared to the flat non-nanostructured hBN surfaces for cases where the edges of the nanoribbon are more hydrophilic (hydrophobic) than the flat part. Overall, the present study develops a most remarkable design space where by introducing nanopillars/nanoribbons on hBN and by merely changing the nature of the edges of these nanopillars, one can ensure atomistically thin coating of hBN with a wide range of wettability.

Preparation of deep eutectic solvent-based hexagonal boron nitride-molecularly imprinted polymer nanoparticles for solid phase extraction of flavonoids.

Hexagonal boron nitride (h-BN) is introduced as a 2D scaffold during the preparation of molecularly imprinted polymers (MIPs). The MIPs were prepared from deep eutectic solvents (DES) or fromDES containing h-BN, crosslinking agent (ethylene glycoldimethacrylate), initiator (AIBN), porogen (methanol), and template (quercetin). The recognition site of the monomer is protected by the hydrogen bond of the DES before the MIP is polymerized. The formation of the final MIP was analyzed theoretically using density-functional theory. The nanoparticles were characterized by scanning electron microscopy, nitrogen sorption analysis, thermogravimetry and Fourier transform infrared spectroscopy. The introduction of h-BN resulted in an increase in the surface area of the nanoparticles. They were applied as a solid phase extraction sorbent for the extraction of flavonoids (specifically of quercetin, isorhamnetin and kaempferol) from Ginkgo biloba leaves. Following extraction with ethanol, they were quantified by HPLC. The new sorbent has distinctly improved recognition capability for flavonoids compared to conventional MIP nanoparticles. Graphical abstractDeep eutectic solvent (DES)-based molecularly imprinted polymer (MIP) was polymerized on the surface of hexagonal boron nitride (h-BN). The h-BN-MIP nanoparticles were applied as a solid phase extraction sorbent for the specific recognition of flavonoids.

High-Q Localized Phonon Polaritons in Thin hBN Discs with Omnidirectional Strong Light Absorptions

Based on numerical calculations, we have found that thin hexagonal boron nitride nanodiscs support high-quality localized phonon polariton modes in the upper Reststrahlen band. Near the resonances, single disc can be phenomenologically considered as an electric dipole. By arranging discs into a square lattice, strong light absorptions can be achieved. Modeling such periodic systems as dipole lattices, simple reflecting substrates can be designed which lead to omnidirectional strong, even nearly perfect, light absorptions. Under the condition of nearly total absorption, the electric fields at the hexagonal boron nitride surfaces are largely enhanced due to low-loss localized phonon polaritons. Our investigations might be useful for phonon polariton–based nanophotonic devices, such as sensors.

Preparation of pineapple leaf micro crystalline cellulose loaded boron nitride powder in presence of polydopamine

The surface of hexagonal boron nitride (h-BN) was modified by polydopamine (PDA) where water being used as the dispersion medium. The interaction between h-BN and pineapple leaf micro crystalline cellulose (PLMCC) was improved resulting in a PDA@h-BN-PLMCC composite powder. This facilitates interactions between h-BN and PLMCC, aligns the h-BN layers along the direction of the cellulose, and eliminates anisotropy. This novel composite powder has potential application for areas such as new thermal interface materials and protection materials for wearable devices.