Pristine Boron Nitride Nanosheets Research Articles

Fundamental mechanisms of hexagonal boron nitride sensing of dopamine, tryptophan, ascorbic acid, and uric acid by first-principles study.

Selectivity of dopamine (DA), uric acid (UA), and ascorbic acid (AA) is an open challenge of electrochemical sensors in the field of biosensing. In this study, two selective mechanisms for detecting DA, UA, and AA biomolecules on the pristine boron nitride nanosheets (BNNS) and functionalized BNNS with tryptophan (Trp), i.e., Trp@BNNS have been illustrated through density functional density (DFT) calculation and charge population analysis. Our findings reveal that the adsorbed biomolecules on Trp@BNNS indicate the less sensitivity factor of biomolecule separation than the functionalized biomolecules with Trp (Trp@biomolecule) adsorbed on pristine BNNS. From the calculations, strong adsorption of Trp@biomolecule on the pristine substrate corresponds to enhancing of electron charge transfer and electrical dipole moment. Our analysis is in good agreement with the previous theoretical and experimental results and suggests new pathway for electrode modification for electrochemical biosensing.

Fermi level modulation of boron nitride nanosheets by vacancy driven compressive strain

In this Letter, the compressive strain-assisted reduction of work function (WF) of boron nitride nanosheets (BNNSs) has been presented. For this purpose, a 30 keV Au−1 ion beam was irradiated on a high-quality BNNS deposited on a Si substrate. Before ion irradiation, the pristine BNNSs were characterized by Raman spectroscopy and UV-Vis absorption spectroscopy for the estimation of its number of layers and bandgap. The scanning electron microscopic images confirm a layer-like structure in a pristine BNNS. An x-ray diffraction (XRD) peak corresponding to the (002) plane of BNNSs appears at an angle of 26°. Shifting of the XRD peak toward higher angle with increasing fluence indicates the presence of a compressive strain in BNNSs. Scanning kelvin probe microscopy was used to map the work function of the surface of BNNSs, and it turned out that the WF decreases with increasing the dose of ions. The possible explanation of compressive strain generation by Au−1 irradiation on BNNSs is discussed using the SRIM-2013 Monte Carlo simulation. The value of strain, calculated from the work function values, qualitatively agrees with the XRD result.

Boron-rich boron nitride nanomaterials as efficient metal-free catalysts for converting CO2 into valuable fuel

Searching for low-cost and metal free catalysts for efficient reduction of CO2 is urgent because metal free catalysts have many advantages, such as high stability and environmental friendly. Based on the comprehensive density functional theory (DFT) calculations of CO2 conversion on boron nitride nanomaterials, the results indicate that the pristine boron nitride nanosheet (BNNS) and boron nitride nanotube (BNNT) cannot efficiently activate CO2, while boron-rich BNNS and BNNT can efficiently convert CO2 to CH4 with very low limiting potentials of −0.27 V and −0.23 V, respectively. In addition, the studies of Mulliken charge analysis of these catalysts also indicate that the two boron-rich structures prefer to donating electrons to CO2 and result in the efficient activation of the C = O double bonds, which promote the activation of CO2 and the following conversion. Moreover, the better performance of CO2 reduction on the B-rich BNNT indicates that the curvature of the surface can further improve its catalytic activity.

Synthesis of Sandwich-Like Nanostructure Fillers and Their Use in Different Types of Thermal Composites.

Thermally conductive yet electrically insulating two-dimensional boron nitride nanosheets (BNNSs) have been an ideal choice for the enhanced fillers for improving thermal properties of polymer-based composites. As a nanofiller with an ultrahigh aspect ratio, BNNSs result in conspicuous stacking along the planar direction in the preparation of composites, which results in strong anisotropy of heat transfer and suppresses out-plane thermal dissipation. Thus, it is necessary to facilitate the out-plane heat transfer by building a favorable microstructure. Focusing on the structural design of the nanofiller itself here, we have fabricated a novel three-dimensional nanofiller with improved out-plane connections. Carbon nanotubes (CNTs) have been grown in situ on the surface of BNNSs using chemical vapor deposition. Utilizing these sandwich-like nanostructure BNNSs/CNTs as fillers in the composites, we have assembled diverse sorts of composites, such as flexible films, scleroid 3D mats, painted ink, and viscous grease. Simultaneously, their thermal and insulating properties have been evaluated. A nearly 330% enhancement of out-plane thermal conductivity from the control sample filled with pristine BNNS is achieved, and the composite also exhibits good electrical resistivity of above 7.5 × 1010 Ω mm. The results indicate that the BNNS/CNT filler has superior thermal performance over the original BNNS while maintaining a satisfactory electrical resistivity to avoid short-circuits in high-power electronics. Furthermore, the prepared grease used as a thermal interface material shows impressive heat dissipation performance when applied on a running computer.

The effect mechanism of functionalization on thermal conductivity of boron nitride nanosheets/paraffin composites

Functionalizations of boron nitride nanosheets (BNNS) are found to be useful for improving the thermal conductivity of materials. However, the mechanism responsible for the enhancement is still open. In this paper, classic molecular dynamic simulations and theoretical analysis model based on the effective medium theory were adopted to investigate the effect mechanism of three types of functionalizations, including C-doping, CH3-grafting and the single-vacancy, on the thermal conductivity of BNNS/paraffin composites. Research results showed that the functionalizations would produce the phonon impurity scattering, which deteriorated the thermal transport of BNNS. However, it could promote the phonon coupling between in-plane and out-of-plane of BNNS, which will boost the energy propagation between paraffin and BNNS and eventually enhance the interface thermal conductance. Under the interaction of the two opposite phenomena, the C-doping functionalization shows to be the most effective method to enhance the thermal conductivity of composites. Comparing with pristine BNNS (p-BNNS), there was a critical size for the thermal conductivity enhancement of functionalized BNNS/paraffin composites. The critical size of the C-doping could reach to 9.1 μm for the functionalized ratio of 2.5%. With the size of 2 μm of the C-doping BNNS, the thermal conductivity of composites could be enhanced by 30% compared with the p-BNNS/paraffin and 10 times compared with paraffin. The current research provides fundamental suggestions for the selections of fillers to enhance the thermal conductivity of matrix.

Adsorption of Phosphine on a BN Nanosurface

Electrical sensitivity of a Boron Nitride Nano Sheet (BNNS) to phosphine (PH3) molecule is studied using Density Functional Theory (DFT) calculations at the B3LYP/6-31G(d) level of theory. The adsorption energy (Ead) of phosphine on the surface of the pristine Nanosheet is about -678.96×1019eV. Pristine BNNS is a suitable adsorbent for phosphine and can be used in separation processes or adsorption of phosphine toxic gas from environmental systems. Consequently, BNNS is doped by Al atom and results show that the adsorption energy range is about - 28882.18×1019 to -52097.61×1019eV which means an increase in adsorption energy. Moreover, the HOMO/LUMO energy gap (Eg) reduces significantly. This reduction shows that the doped BNNS in the presence of phosphine is a suitable semiconductor and generates an electrical signal. Therefore, it can be used potentially as phosphine toxic gas detection sensors in environmental systems.

Formaldehyde adsorption on pristine, Al-doped and mono-vacancy defected boron nitride nanosheets: A first principles study

The interactions between formaldehyde (H2CO) and different kinds of boron nitride nanosheets, which are included pristine, aluminum doped or boron/nitrogen vacancy defected sheets, are investigated using density functional theory (DFT) method. It is shown that although H2CO molecule has no considerable interaction with pristine boron nitride nanosheet, it tends to be chemisorbed to Al-doped and N-vacancy defected boron nitride sheets with significant adsorption energies. The atoms in molecules theory (AIM) is also applied to analyze these interactions. Deformation and binding energy contributions of the adsorption energies are also evaluated separately. It is found from the obtained DOS spectra that the electronic properties of N-vacancy defected boron nitride sheet change considerably by the adsorption of formaldehyde on it; whereas no such variations are observed for the other considered sheets. Therefore it seems that N-vacancy defected boron nitride nanosheet could be a promising candidate for detecting H2CO molecule.