Dimensional Hexagonal Boron Nitride Research Articles

Optimization of ternary composite @PANI/MoO3/h-BN and its electrochemical evaluation as an electrode material for supercapacitor application

The rapid charge-discharge process, high power density and longer cycle life which supercapacitor possess paves way as an important energy storage device in the electronic technology sector. Fast expanding applications in electric vehicles and portable electronics demand high energy storage electrodes. The expansive applications of two dimensional hexagonal boron nitride (h-BN) nanostructures accelerate usage in energy storage systems. Synthesis of Ternary composite consisting of polyaniline (PANI), h-BN (hexagonal boron nitride), molybdenum trioxide (MoO3) is reported with highest capacitance 518 F/g for PMB-135 composite at current density of 1 A/g. The highest energy density among all the composites was PMB-135 observed as 10.34 Wh/kg. This study with controlled size and uniformity may provide extensive self-attaining property for high performance energy storage materials.

Investigation on the influence of ball milling on the microstructural properties of 2D-hexagonal boron nitride towards electroadhesive applications

A light weight low power operated fabric based electroadhesive actuators were made with two dimensional hexagonal boron nitride (hBN) in PVdF-HFP polymer matrix as a dielectric and Cu/Ni fabric tape as electrodes for applications in robotics and exosuits. The properties of the dielectric layer were tuned for high load bearing capacity by inducing dangling joints in 2D hBN by the atmospheric ball milling as a factor of time. The electroadhesive actuator was optimized for a maximum load of 700 g for a DC voltage of 250 V, by changing the micro structures of 2D hBN with ball milling for different hours. The optimized load bearing capacity of the electroadhesive actuators obtained with 1 h ball milled 2D hBN incorporated PVdF-HFP matrix has been evidenced through structural and morphological studies.

Enhanced catalysis through structurally modified hybrid 2-D boron nitride nanosheets comprising of complexed 2-hydroxy-4-methoxybenzophenone motif

Tuning the structural architecture of the pristine two dimensional hexagonal boron nitride (h-BN) nanosheets through rational surface engineering have proven advantageous in the fabrication of competent catalytic materials. Inspired by the performance of h-BN based nanomaterials in expediting key organic transformations, we channelized our research efforts towards engineering the inherent surface properties of the exclusively stacked h-BN nanosheets through the incorporation of a novel competent copper complex of a bidentate chelating ligand 2-hydroxy-4-methoxybenzophenone (BP). Delightfully, this hybrid nanomaterial worked exceptionally well in boosting the [3 + 2] cycloaddition reaction of azide and nitriles, providing a facile access to a diverse variety of highly bioactive tetrazole motifs. A deep insight into the morphology of the covalently crafted h-BN signified the structural integrity of the exfoliated h-BN@OH nanosheets that exhibited lamellar like structures possessing smooth edges and flat surface. This interesting morphology could also be envisioned to augment the catalysis by allowing the desired surface area for the reactants and thus tailoring their activity. The work paves the way towards rational design of h-BN based nanomaterials and adjusting their catalytic potential by the use of suitable complexes for promoting sustainable catalysis, especially in view of the fact that till date only a very few h-BN nanosheets based catalysts have been devised.

Shape evolution of two dimensional hexagonal boron nitride single domains on Cu/Ni alloy and its applications in ultraviolet detection

Two dimensional (2D) hexagonal boron nitride (h-BN) has attracted extensive attention due to its high thermal and chemical stability, excellent dielectric characteristic, and unique optical properties. However, the chemical vapor deposition synthesis of 2D h-BN is not fully explored, such as morphology regulation and size control. Here we demonstrate the growth of 2D h-BN single domains on Cu/Ni alloy via atmospheric chemical vapor deposition (APCVD). We discover that the shape of the as-grown h-BN single domains can be controlled from triangles, hexagons, to circles by adjusting the Ni content of the Cu/Ni substrates. Moreover, we find out that increasing the nickel content can suppress the nucleation density while the average domain size is accordingly improved. The grown single-crystalline h-BN demonstrates ultralow dark current about 0.9 pA and outstanding ultraviolet response with the responsivity up to 5.45 mAW−1. The response time are 376 and 198 ms. Our work sheds light on the controllable synthesis of 2D h-BN and promotes its applications in high ultraviolet detection.

An ultrasensitive Fano resonance biosensor using two dimensional hexagonal boron nitride nanosheets: theoretical analysis.

This study proposed a novel Fano resonance (FR) biosensor with ultrahigh detection sensitivity by integrating two dimensional (2D) hexagonal boron nitride (h-BN) nanosheets with a plasmonic silver film–silicon hybrid nanostructure. Owing to its ultralow-loss in surface plasmon polaritons (SPPs), 2D h-BN nanosheets can act as a planar photon waveguide (PWG) for generating energy level splitting. Notably, both asymmetric FR sharp lines and plasmon induced transparency (PIT) can be produced by modulating the coupling strength between the planar PWG mode provided by h-BN nanosheets and the surface plasmon polariton (SPP) mode in the silver film–silicon hybrid nanostructure. Compared with conventional phase-modulation SPR biosensors, our proposed configuration based on Fano resonance can produce ultrahigh reflectivity of 0.934 and overcome the limitation of quasi-darkness reflectivity which is difficult for further phase extraction. More importantly, our proposed FR configuration can provide a promising phase detection sensitivity as high as 3.13 × 106 degree per RIU (refractive index unit, RIU), which is enhanced by almost 100 times compared with conventional phase-modulation SPR biosensors. In addition, our proposed configuration has also shown the characteristics of multiple-order Fano resonances, largely depending on the partial coupling between the SPP mode and the different-order PWG mode. Our proposed FR biosensor can provide a highly promising candidate for designing a multiple-order FR platform for performing ultrasensitive detection.

Three dimensional hexagonal boron nitride nanosheet/carbon nanotube composites with light weight and enhanced microwave absorption performance

Three dimensional hexagonal boron nitride nanosheet decorated carbon nanotube composites (3D h-BNNS/CNTs) have been fabricated through a facile thermal treatment process. h-BNNSs randomly distribute among CNTs to form 3D network structure. The microwave absorption properties of these 3D h-BNNS/CNTs are obviously improved comparing with those of CNTs. And the minimum reflection loss (RL) can reach up to −36.5 dB when the absorber thickness is 2.5 mm for 3D h-BNNS/CNTs1 derived from the precursor with boric acid, urea and CNTs molar ratio of 2:4:1. Besides, the maximum absorption bandwidth (RL ≤ −10 dB) is as large as 4.0 GHz when the absorber thickness drops to 2.0 mm. More important, h-BNNS/CNTs1 has a low density of 112.6 ± 3.6 mg/cm3, which is beneficial for practical applications. The significant enhancement in MA performance of h-BNNS/CNTs is mainly attributed to the improvement of impedance matching, interfacial polarization and multiple scattering after introduction of h-BNNSs.

Kapitza conductance of symmetric tilt grain boundaries of monolayer boron nitride

We use reverse nonequilibrium molecular dynamics simulations to study thermal conductivity of two–dimensional hexagonal boron nitride (h–BN) nanoribbons containing symmetric tilt grain boundaries. The simulations are conducted on periodic h–BN nanoribbons with zigzag and armchair chirality. The effective thermal conductivity of ribbons and Kapitza conductance of grain boundaries are calculated by inducing a constant heat flux along the longitudinal direction of ribbons. The steady state temperature profiles of nanoribbons display jumps at the location of grain boundaries. The temperature jumps monolithically increases with the misorientation angle of grain boundaries indicating that grain boundaries with higher misorientation angle have lower Kapitza conductance. The lower Kapitza conductance is due to higher phonon scattering at grain boundaries which is a result of a higher mismatch between the phonon spectra of grain boundary and grain atoms. Our modeling results also predict that by increasing the length, both Kapitza conductance of grain boundaries and effective thermal conductivity of ribbons increases. Although temperature does not have a significant impact on Kapitza conductance, but by increasing temperature effective thermal conductivity of ribbons decreases.

Quantum Light in Curved Low Dimensional Hexagonal Boron Nitride Systems

Low-dimensional wide bandgap semiconductors open a new playing field in quantum optics using sub-bandgap excitation. In this field, hexagonal boron nitride (h-BN) has been reported to host single quantum emitters (QEs), linking QE density to perimeters. Furthermore, curvature/perimeters in transition metal dichalcogenides (TMDCs) have demonstrated a key role in QE formation. We investigate a curvature-abundant BN system – quasi one-dimensional BN nanotubes (BNNTs) fabricated via a catalyst-free method. We find that non-treated BNNT is an abundant source of stable QEs and analyze their emission features down to single nanotubes, comparing dispersed/suspended material. Combining high spatial resolution of a scanning electron microscope, we categorize and pin-point emission origin to a scale of less than 20 nm, giving us a one-to-one validation of emission source with dimensions smaller than the laser excitation wavelength, elucidating nano-antenna effects. Two emission origins emerge: hybrid/entwined BNNT. By artificially curving h-BN flakes, similar QE spectral features are observed. The impact on emission of solvents used in commercial products and curved regions is also demonstrated. The ‘out of the box’ availability of QEs in BNNT, lacking processing contamination, is a milestone for unraveling their atomic features. These findings open possibilities for precision engineering of QEs, puts h-BN under a similar ‘umbrella’ of TMDC’s QEs and provides a model explaining QEs spatial localization/formation using electron/ion irradiation and chemical etching.

Structural stability and electronic properties of an octagonal allotrope of two dimensional boron nitride.

An octagonal allotrope of two dimensional boron nitride is explored through first principles calculations. Calculations show that two dimensional octagonal boron nitride can be formed with a binding energy comparable to two dimensional hexagonal boron nitride. In addition, two dimensional octagonal boron nitride is found to have a band gap smaller than two dimensional hexagonal boron nitride, suggesting the possibility of semiconductive attributes. Two dimensional octagonal boron nitride also has the ability to layer through physisorption. Defects present within two dimensional octagonal boron nitride also lead toward the introduction of a magnetic moment through the absence of boron atoms. The presence of defects is also found to render both hexagonal and octagonal boron nitrides reactive against hydrogen, where greater reactivity is seen in the presence of nitrogen. Thus, two dimensional octagonal boron nitride is confirmed with potential to tailor properties and reactivity through lattice shape and purposeful introduction of defects.

Two dimensional hexagonal boron nitride (2D-hBN): synthesis, properties and applications

Comprehensive summary of the progress including crystal structures, fabrication methods, applications (especially for electronics) and functionalization of 2D-hBN from its discovery.

Thermal transport across few-layer boron nitride encased by silica

Two dimensional hexagonal boron nitride (h-BN) attracted attention for use in applications. Using equilibrium molecular dynamics, we examine the phonon transport in few-layer h-BN encased by silica (SiO2). We report large interfacial thermal resistances, of about 2.2 × 10−8 m2 K W−1, which are not sensitive to the number of h-BN layers or the SiO2 crystallinity. The h-BN/SiO2 superlattices exhibit ultra-low thermal conductivities across layers, as low as 0.3 W/m K. They are structurally stable up to 2000 K while retaining the low-thermal conductivity attributes. Our simulations indicate that incorporation of h-BN layers and nanoparticles in silica could establish thermal barriers and heat spreading paths, useful for high performance coatings and electronic device applications.

Growth and spectroscopic characterization of monolayer and few-layer hexagonal boron nitride on metal substrates.

Atomically thin two dimensional hexagonal boron nitride (2D h-BN) is one of the key materials in the development of new van der Waals heterostructures due to its outstanding properties including an atomically smooth surface, high thermal conductivity, high mechanical strength, chemical inertness and high electrical resistance. The development of 2D h-BN growth is still in the early stages and largely depends on rapid and accurate characterization of the grown monolayer or few layers h-BN films. This paper demonstrates a new approach to characterizing monolayer h-BN films directly on metal substrates by grazing-incidence infrared reflection absorption spectroscopy (IRRAS). Using h-BN films grown by atmospheric-pressure chemical vapor deposition on Cu and Ni substrates, two new sub-bands are found for the A2u out-of-plane stretching mode. It is shown, using both experimental and computational methods, that the lower-energy sub-band is related to 2D h-BN coupled with substrate, while the higher energy sub-band is related to decoupled (or free-standing) 2D h-BN. It is further shown that this newly-observed fine structure in the A2u mode can be used to assess, quickly and easily, the homogeneity of the h-BN-metal interface and the effects of metal surface contamination on adhesion of the layer.