Surface Of Boron Nitride Nanotubes Research Articles

Potential of Ge-adopted Boron Nitride Nanotube as Catalyst for Sulfur Dioxide Oxidation

In recent years, the discovery of efficient catalyst with low price to sulfur dioxide (SO2) oxidation in normal temperature is a major concern in the industry. In present study, in first step the boron nitride nanotube (BNNT) with Ge were adopted and the surface of Ge-adopted BNNT via O2 molecule were activated. In second step the SO2 oxidation on activated Ge-BNNT surface via Langmuir Hinshelwood (LH) and Eley Rideal (ER) mechanisms was investigated. Results show that O2 activated Ge-BNNT surface can oxide the SO2 molecule via Ge-BNNT-O-O* + SO2 → Ge-BNNT-O-O*-SO2 → Ge-BNNT-O* + SO3 and Ge-BNNT-O* + SO2 → Ge-BNNT + SO3 reactions. Results show that SO2 oxidation on activated Ge-BNNT surface via the LH mechanism has lower energy barrier than ER mechanism. Finally, calculated parameters reveal that activated Ge-BNNT is acceptable catalyst with low price and high performance for SO2 oxidation in normal temperature.

The Boron Nitride Nanotube, an Ideal Host Structure for Efficient Immobilization and Delivery of RNA Aptamer: Classical Molecular Dynamics Simulation

Boron nitride nanotubes (BNNTs) are nontoxic to health and environment due to their chemical inertness and structural stability. The BNNTs are more suitable for medical applications such as drug delivery. The adsorption and immobilization of RNA aptamer was studied using the molecular dynamics simulation at the temperature of 310 K. We have selected free (mobile) and fixed (12,12) and (40,40) bio-compatible BNNTs for this propose. After minimization, heating, equilibration and 60 ns production molecular dynamics simulation, it was found that the considered RNA aptamer was adsorbed and immobilized onto and inside of the BNNT surfaces. The structural parameters, including root-mean-square deviation and fluctuation, and the normalized number of hydrogen bonds between adsorbed aptamer and surrounded water molecules before and after adsorption, were measured and discussed. Besides, the ability of BNNT to carry the aptamer inside it was investigated. It was observed that the mobile BNNT can deliver RNA aptamer with no structural deformation. All the collected data are very promising, suggesting the enabling of BNNT exploitation in nano-medicine as nano-transducers and nano-carriers.

Carbon and boron nanotubes as a template material for adsorption of 6-Thioguanine chemotherapeutic: a molecular dynamics and density functional approach

The interaction of 6-Thioguanine molecule, an antitumor drug with carbon nanotube and boron nitride nanotube (BNNT) is investigated using molecular dynamics simulations. Based on the obtained results, the strongest negative van der Waals interaction is found between 6-TG and BNNT among the studied nanotubes, which indicated BNNT is a better nanocarrier of the 6-TG drug than CNT within biological systems. Moreover, the adsorption and electronic properties of the 6-Thioguanine interacted with boron-nitride nanotube has been studied within the framework of density functional theory calculations. The negative binding energy values denote that there is the favorable interaction between 6-TG drug and BNNT at the studied 6-TG/BNNT complexes. Also, the amounts of the binding energies indicated that the 6-Thioguanine molecule physically interacts with the surface of BNNT. The values of electron densities and their Laplacian have been analyzed using the Bader's theory of atoms in molecules to characterize the nature of the intermolecular interactions through the topological parameters. We hope that the results of this work may provide useful information about the nature of the nanotube–drug molecule interactions and highlight the ability of these materials to be used as an adsorbent enhancing delivery of drug to cancer cells. Communicated by Ramaswamy H. Sarma

PH‐Switchable Water‐Soluble Boron Nitride Nanotubes

AbstractThe first example of aqueous solutions of boron nitride nanotubes (BNNTs) with switchable stability and without use of surfactants is demonstrated. The as‐produced boron nitride nanotubes are both purified and solubilized through an environmentally friendly and scalable approach using water extraction and liquid bromine treatment. This treatment effectively removes elemental boron particles and excess bromine reacts with BNNTs, inducing B−N bond cleavage on the BNNT surface to yield hydroxyl (OH) and amino (NH2) functionalized BNNTs. The resulting functionalized BNNTs form stable aqueous solutions around neutral pH (4 < pH < 8), but readily precipitate in other pH ranges. This switchable solubility is explained in terms of the capability of the functional groups (OH and NH2) to form hydrogen‐bonding networks in water. Further, the solubility differences in selected polar organic solvents have been utilized to prepare functionalized BNNTs with higher purity.

Ab initio study of adsorption of CO on BNNTs: For gas nanosensor applications

In this study, the adsorption of carbon monoxide (CO) gas, on the surface of boron nitride nanotubes in pure form, as well as doped with Al and Ga, based on the density functional theory has been studied. The electron and structural properties of pristine and doped nanotubes have been investigated. By calculating the adsorption energy, the most stable positions and the equilibrium distance are obtained, and charge transferred and electron properties have been calculated. The most stable molecule adsorption position for pure nanotube is obtained at the center of the hexagon and for doped nanotube above the impurity. Adsorption of the molecule that is perpendicular to the nanotube axis is more stable than that with the horizontal position to the nanotube axis, and the adsorption from C atoms side is stronger than O atoms. According to the results, zigzag boron nitride nanotube is more sensitive to the adsorption of CO molecules than armchair type. The results show that gas molecule adsorption has a very slight effect on the electrical properties of pure nanotubes, which can indicate a physical adsorption. After doping, the amount of adsorption energy has changed for the most stable positions and shifted to the range of chemical adsorptions.

Adsorption of cyanogen chloride on the surface of boron nitride nanotubes for CNCl sensing

The adsorption of CNCl gas, on the surface of boron nitride nanotubes in pure form, as well as doped with Al and Ga, based on the density functional theory (DFT) has been studied. The electron and structural properties of pristine and doped nanotubes have been investigated. By calculating the adsorption energy, the most stable positions and the equilibrium distance are obtained, and charge transferred and electronic properties have been calculated. The most stable molecule adsorption position for pure nanotube is obtained at the center of the hexagon and for doped nanotube above the impurity atom from N side.

Interaction of Boron Nitride Nanotubes with Aluminium: A Computational Study.

The interaction of boron nitride nanotubes (BNNTs) with Al has been investigated by means of quantum chemical calculations. Two model structures were used: a BNNT adsorbing a four atom Al4 cluster, and a BNNT adsorbed on Al surfaces of different crystallographic orientations. The BNNTs were modeled as: (i) pristine, and (ii) having a boron (B-) or a nitrogen (N-) vacancy defect. The results indicated that the trends in binding energy for Al4 clusters were, similar to those of the adsorption on Al surfaces, while the Al surface orientation has a limited effect. In all cases, the calculations reveal that Al binding to a BNNT was strongly enhanced at a defect site on the BNNT surface. This higher binding was accompanied by a significant distortion of the Al cluster or the Al lattice near the respective vacancy. In case of a B-vacancy, insertion of an Al atom into the defect of the BNNT lattice, was observed. The calculations suggest that in the Al/BNNT metal matrix composites, a defect-free BNNT experiences a weak binding interaction with the Al matrix and tthe commonly observed formation of AlN and AlB2 was due to N- or B-vacancy defects within the BNNTs.

Covalent Surface Functionalization of Boron Nitride Nanotubes Fabricated with Diazonium Salt

The chemical inertness and poor wetting properties of boron nitride nanotubes (BNNTs) hindered their applications. In this work, BNNTs have been functionalized with aniline groups by reacting with diazonium salt and the graft content of aniline component was calculated as high as 71.4 wt.%. The chemical structure, composition, and morphology of functionalized BNNTs were carefully characterized to illustrate the modification. The anilinocarbocation generated by decomposition of diazonium salt reacted not only with NH2 sites, but also with B-OH sites on the surface of BNNTs. Meanwhile, the reaction applied a hot strong acid environment, which would help to open parts of B-N bonds to produce more reactive sites and enrich the functional groups grafted on the surface of BNNTs. Consequently, the functionalized BNNTs exhibited significantly improved dispersion stability in chloroform compared with pristine BNNTs. Amino surface functionalization of BNNTs offered more possibilities for surface chemical design of boron nitride and its practical application.

HPLC Characterization of the Association Mechanism of Organic Compounds with β Cyclodextrin Using a Novel Boron Nitride Nanotube Particulate Stationary Phase

In this paper, a simple homogeneous coating of silica spherical particles with pristine boron nitride nanotubes (BNNTs) was described. BNNTs dissolved in dimethylacetamide (DMAc) were mixed with amino-functionalized silica particles having a 5 μm diameter. Favorable interaction between the amino group and the BNNT surfaces induces the absorption of the BNNTs on the silica. The BNNT-coated silica particles were used as stationary phase for HPLC. For the first time, it was demonstrated that this new particulate BNNT stationary phase can be used for the study of the complexation of solute molecules (terpene molecules used as test drugs in this work) with β cyclodextrin (βCD). The apparent formation constants Kf of terpene derivative/βCD were in the same magnitude as those reported in the literature. The plot of Kf versus the water fraction in the methanol/water mobile phase showed that the BNNT surface played an active role in the complex formation due to terpene/BNNT-specific polar interactions. This work demonstrated that our novel particulate BNNT HPLC stationary phase was an efficient tool to study molecular recognition mechanism and more specifically the association between a drug substance and a target molecule with the aim of reaching biopharmaceutic and clinical applications.

Boron nitride nanotubes for delivery of 5-fluorouracil as anticancer drug: a theoretical study

Abstract The electronic structure and properties of the armchair boron nitride nanotubes (BNNTs) interacted with the 5-FU drug, as an anticancer drug, are studied at the B3LYP/6-31G(d,p) level of theory. D3-Corrections were carried out for the treatment of intermolecular interactions in the hybrid complexes and encapsulated nanotubes, exactly. Results have shown that the encapsulation and adsorption of 5-FU molecule on the studied BNNTs surface are favorable processes, with a few exceptions. Also, it is found that the encapsulated nanotubes are stable than the hybrid complexes. Furthermore, we estimated the strengths of the intermolecular bonds of the benchmark systems by energetic, geometric, topological and molecular orbital descriptors. Some analyses have been made to explore any changes in the binding characteristics of the drug molecule after its attachment to the nanotubes. According to the NBO results, the charge transfer phenomenon is observed from the bonding or nonbonding orbitals of drug to the antibonding orbitals of BNNTs. Moreover, HOMO–LUMO analysis indicated that, after the adsorption process, the HOMO value slightly increased, while the LUMO value in these systems significantly reduced in the both of Drug@BNNTs groups. So, the energy gaps between HOMO and LUMO (Eg) are reduced, which emphasis on the greater intermolecular bond strength. Finally, the stability and reactivity of the Drug@BNNTs complexes have been examined from the magnitudes of the chemical reactivity descriptors such as chemical potential, global hardness, and electrophilicity index. As a consequence, BNNTs can be considered as a drug delivery vehicle for the transportation of 5-FU as anticancer drug within the biological systems.

Non-covalent green functionalization of boron nitride nanotubes with tunable aryl alkyl ionic liquids: A quantum chemical approach

The quantum mechanical treatments of the non-covalent interactions of the (8,0) zigzag single-walled boron nitride nanotube (BNNT) with the five types tunable aryl alkyl ionic liquids (TAAILs) as well as corresponding cations were carried out at the M06-2X/6–31+G(d):PM6 level of theory to better understand the trends in interaction between BNNT and ILs. Two different complexes (A|| and B⊥) were found in non-covalent interaction between BNNT surface and [X-PhMIM][BF4] (XNH2, CH3, H, CHO and NO2) TAAILs. Comparison of interaction energies indicates that the B⊥ complexes are more stable than A|| ones. A detailed analysis of the geometric and electronic properties, charge transfer, electron density properties, global reactivity descriptors, work function, dipole moment and electron density of the states for pure BNNT and different configurations of the modified BNNT were carried out. It is predicted that the π-π stacking of BNNT with the TAAILs is accompanied by a decrease in the energy gap. ChelpG analysis reveals that the interaction of ILs with BNNT induces the charge transfer from anion to cation. Inspection of the results shows that the charge in the A|| complexes is transferred from IL to BNNT for electron donating substituents and from BNNT to IL for H and electron accepting ones. The results also show that the charge in the B⊥ complexes is transferred from IL to BNNT with the exception of IL containing the NO2 substituent. To understand the behavior of non-covalent interactions (NCI) between BNNT sidewalls and Z1–5 TAAILs and the corresponding Z′1–5 cations, the NCI index (RDG) is utilized.

Ab initio investigation of pristine and doped single-walled boron nitride nanotubes as acetone sensor

The sensor properties of single-walled boron nitride nanotubes (BNNTs) towards acetone are studied by investigating the intermolecular interactions of acetone with a serials of pristine and doped BNNTs. Density-functional theory (DFT) with empirical dispersion corrected is adopted to explore the adsorption properties of acetone on the surface of BNNT. Results show that acetone binds strong to the surface of pristine BNNTs with small diameter and the adsorption energy decreases significantly as the tube diameter increases. The adsorption of acetone on serials of doped BNNTs (Al, Si, Cu, Co, Ni, Ga, and Ge) shows that the adsorption of acetone on BNNT can be strengthened by the doped impurity. With the analysis of charge density, density of states, molecular orbitals, and the noncovalent interaction index (NCI), the study shows that the sensitivity of BNNT-based chemical gas sensor towards acetone can be remarkable improved by introducing appropriate dopant. The study also reveals the potential application of BNNT as sensor for the detection of acetone molecule.

Surface-charge effects on the electro-orientation of insulating boron-nitride nanotubes in aqueous suspension

The alignment of hexagonal boron-nitride nanotubes (BNNTs) in aqueous KCl solutions under spatially uniform electric fields was examined experimentally, using direct optical visualization to probe the orientation dynamics of individual BNNTs for different electric-field frequencies. Different from most previously studied nanowires and nanotubes, BNNTs are wide-bandgap materials which are essentially insulating at room temperature. We analyze the electro-orientation of BNNTs in the general context of polarizable cylindrical particles in liquid suspensions, whose behavior can fall into different regimes, including alignment due to Maxwell-Wagner induced dipoles at high frequencies, and alignment due to fluid motion of the electrical double layer around the particles at lower frequencies. For BNNTs, the variation of the crossover frequencies in the electro-orientation spectra was studied in electrolytes of different conductivity. The effect of BNNT surface charge on electro-orientation was further studied by changing the pH of the aqueous solution. We find that the electric-field alignment of the BNNTs in the low-frequency regime is associated with the charging and motion of the electrical double layer around the particle. However, as BNNTs are non-conducting particles, the reasons for the formation of the electrical double layer are likely to be different than that of conducting particles. We discuss two possible mechanisms for the double-layer formation and alignment of 1D dielectric particles, and make comparison to those for the more commonly studied conducting particles.

Ga-doped and antisite double defects enhance the sensitivity of boron nitride nanotubes towards Soman and Chlorosoman

Adsorption of Soman and Chlorosoman over the outer surface of boron nitride nanotube (BNNT) was studied using density functional theory (DFT) calculations to consider its sensitivity toward mentioned nerve agents. Then, we studied the sensitivity of Ga-doped BNNT and double-antisite defective BNNT (d-BNNT) effects towards adsorbed molecule resulting in eye-catching sensitivity of defected adsorbents representing strong chemical adsorption on the Ga-doped BNNT, while they are mainly physisorbed on the pure BNNT with negligible electronic properties. Density of states (DOSs) was analyzed for further understanding of electronic properties of the applied configurations. Charges were moved from BNNT to the single molecules while in case of Ga-doped and d-BNNT; the charges were transferred from single molecules to the defected adsorbents. These along with outcomes of quantum molecular descriptors, difference in energy gap (Eg), and dipole moments clearly reveal that the d-BNNT is a promising sensor material for the detection of these nerve agents.

Enhanced Thermal Conductivity of Individual Polymeric Nanofiber Incorporated with Boron Nitride Nanotubes

Thermal conductivity of individual polyvinylpyrrolidone (PVP) nanofibers embedding boron nitride nanotube (BNNT) fillers has been measured. The PVP nanofibers were electrospun on suspended microdevices in order to better understand the effect of BNNT fillers on the thermal conductivity of polymeric nanofibers. Various material characterization methods provided evidence that ketone group in the PVP interacted with the surface of BNNTs via strong intermolecular forces, thereby resulting in an effective heat transfer between the polymer matrix and BNNTs. The individual PVP nanofiber containing 30 wt % of BNNTs exhibited approximately 2-fold higher thermal conductivity than that of the bulk PVP.

Improved tensile and buckling behavior of defected carbon nanotubes utilizing boron nitride coating – A molecular dynamic study

Synthesizing inorganic nanostructures such as boron nitride nanotubes (BNNTs) have led to immense studies due to their many interesting functional features such as piezoelectricity, high temperature resistance to oxygen, electrical insulation, high thermal conductivity and very long lengths as physical features. In order to utilize the superior properties of pristine and defected carbon nanotubes (CNTs), a hybrid nanotube is proposed in this study by forming BNNTs surface coating on the CNTs. The benefits of such coating on the tensile and buckling behavior of single-walled CNTs (SWCNTs) are illustrated through molecular dynamics (MD) simulations of the resulted nanostructures during the deformation. The AIREBO and Tersoff-Brenner potentials are employed to model the interatomic forces between the carbon and boron nitride atoms, respectively. The effects of chiral indices, aspect ratio, presence of mono-vacancy defects and coating dimension on coated/non-coated CNTs are examined. It is demonstrated that the coated defective CNTs exhibit remarkably enhanced ultimate strength, buckling load capacity and Young's modulus. The proposed coating not only enhances the mechanical properties of the resulted nanostructure, but also conceals it from few external factors impacting the behavior of the CNT such as humidity and high temperature.

Development of a simple technique for the coating of monolithic silica with pristine boron nitride nanotubes (BNNTs): HPLC chromatographic applications

In this paper, a novel and very simple homogeneous coating of a monolithic silica HPLC support using pristine boron nitride nanotubes (BNNTs) was d0.escribed. The chromatographic support was coated with BNNTs in a non covalent way to preserve the nanotube structure. A solution of BNNTs dispersed in dimethylacetamide (DMAc) was pumped through the column at a flow-rate of 0.3mL/min for 24h at room temperature. Strong interaction between amino groups and the BNNT surfaces induces the adsorption of the BNNTs on the silica, while the stable solvation in DMAc hampers further adsorption of the tubes. The excellent stability of the non covalent BNNT-coating on the monolithic silica in view of application for HPLC was also demonstrated. It was shown that this novel stationary phase was efficient for the HPLC isocratic or gradient mode separation of molecules of different structure such as phenol derivatives, alkylbenzene or doping agents (steroids). As well, this simple technique of BNNT immobilization offers new perspectives for the BNNT-coating on the surfaces of a wide range of solid substrates.

α-d-Glucopyranose Adsorption on a Pd30 Cluster Supported on Boron Nitride Nanotube

Boron nitride nanotube (BNNT) as an innovative support for carbohydrate transformation processes was evaluated, using density functional theory. The α-d-glucopyranose adsorption on a Pd30 cluster, supported on BNNT, was used to check both the local activity of topologically different metallic sites and the effects of the proximity of the BNNT surface to the same metallic sites. Detailed geometrical and electronic analyses performed on Pd30/BNNT and α-d-glucopyranose/Pd30/BNNT systems were discussed. It was observed that the deposition of the Pd30 cluster onto the BNNT support gives rise to an electronic rearrangement, determining a charge transfer from the support to the adsorbed metal cluster. The charge transfer, as shown by the analysis of molecular electrostatic potential, seems to generate electron-rich and electron-poor zones in the Pd30 cluster. The α-d-glucopyranose species, regardless the interaction geometry experienced, acts as an electron donor and preferentially adsorbs close to the electron-poor metal/support interface.

Development of high thermal conductivity via BNNTs/epoxy/organic-Si hybrid composite systems

Epoxy as a type of matrix material has been extensively applied for printed circuit boards (PCBs) and electronic packaging industry. In this work, polymer matrix composites, based on epoxy modified by organosilicon resin and filled with boron nitride nanotube (BNNT) were successfully prepared. Effects of the content of BNNT and organosilicon resin respectively on the thermal conductivity (TC) of the composites were investigated. The structure of the composites was analyzed by DSC, SEM and Raman. With the increase of the BNNT content, the TC of the composites enhanced. When the BNNT content rose to 5.0 wt%, the TC value of the composite was 0.45 W/m K, about three times higher than that of neat epoxy (0.1 W/m K). Also, the addition of organosilicon resin to the former epoxy filled with BNNT (5.0 wt% filling content) benefited the improvement of the TC value of the composites, which soared to 0.79 W/m K, almost seven times greater than that of the original epoxy. The TC value of composite was 0.21 W/m K whilst the filing content of AlN reached 10 wt%. The experimental result indicated that the Tg of the composites increases, and their damping decreased. It owed to the forceful interaction between the BNNT and epoxy matrix, restraining the mobility of the epoxy chain characterized by Raman. Raman analysis showed red-shifting in the epoxy/organosilicon/BNNT composite, which evidenced good wetting around the BNNT surface by the polymer due to the effect that the organosilicon resin improved the interface interaction between the BNNT powder and the epoxy resin matrix. This resulted in an increase of the crosslinking density with the filling of BNNT powder, so heat flow network of composite system would be more easily formed. Accomplished the above great improvement, the composites are promising for use as PCB substrates.

Scattering-type scanning near-field optical microscopy with reconstruction of vertical interaction.

Scattering-type scanning near-field optical microscopy provides access to super-resolution spectroscopic imaging of the surfaces of a variety of materials and nanostructures. In addition to chemical identification, it enables observations of nano-optical phenomena, such as mid-infrared plasmons in graphene and phonon polaritons in boron nitride. Despite the high lateral spatial resolution, scattering-type near-field optical microscopy is not able to provide characteristics of near-field responses in the vertical dimension, normal to the sample surface. Here, we present an accurate and fast reconstruction method to obtain vertical characteristics of near-field interactions. For its first application, we investigated the bound electromagnetic field component of surface phonon polaritons on the surface of boron nitride nanotubes and found that it decays within 20 nm with a considerable phase change in the near-field signal. The method is expected to provide characterization of the vertical field distribution of a wide range of nano-optical materials and structures.