Evaluating the Efficiency of Boron Nitride Coating in Single-Walled Carbon-Nanotube-Based 1D Heterostructure Films by Optical Spectroscopy

Single-walled carbon nanotube (SWCNT) films exhibit exceptional optical and electrical properties, making them highly promising for scalable integrated devices. Previously, we employed SWCNT films as templates for the chemical vapor deposition (CVD) synthesis of one-dimensional heterostructure films where boron nitride nanotubes (BNNTs) and molybdenum disulfide nanotubes (MoS2NTs) were coaxially nested over the SWCNT networks. In this work, we have further refined the synthesis method to achieve precise control over the BNNT coating in SWCNT@BNNT heterostructure films. The resulting structure of the SWCNT@BNNT films was thoroughly characterized using a combination of electron microscopy, UV-vis-NIR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. Specifically, we investigated the pressure effect induced by BNNT wrapping on the SWCNTs in the SWCNT@BNNT heterostructure film and demonstrated that the shifts of the SWCNT's G and 2D (G') modes in Raman spectra can be used as a probe of the efficiency of BNNT coating. In addition, we studied the impact of vacuum annealing on the removal of the initial doping in SWCNTs, arising from exposure to ambient atmosphere, and examined the effect of MoO3 doping in SWCNT films by using UV-vis-NIR spectroscopy and Raman spectroscopy. We show that through correlation analysis of the G and 2D (G') modes in Raman spectra, it is possible to discern distinct types of doping effects as well as the influence of applied pressure on the SWCNTs within SWCNT@BNNT heterostructure films. This work contributes to a deeper understanding of the strain and doping effect in both SWCNTs and SWCNT@BNNTs, thereby providing valuable insights for future applications of carbon-nanotube-based one-dimensional heterostructures.

Form Factor-Free Boron Nitride Nanotube-Agarose Composites for Neutron Shielding

Boron nitride nanotubes (BNNTs) have remarkable mechanical and thermal properties and are suitable for neutron shielding due to boron. Because BNNTs exist in bundled and stiff shapes, limiting their practical applications, however, it is essential to improve their formability and processability. In this study, we demonstrate form-factor-free BNNTs and agarose composites for use in neutron shielding for the first time; they are fabricated by mixing hydrophilic agarose with noncovalently functionalized water-soluble BNNTs (p-BNNTs). The mechanical properties of the agarose/p-BNNT composite films surpass those of conventional commodity plastics. When the p-BNNT concentration increased, the neutron linear attenuation coefficient of the composite film increases from 0.574 ± 0.010 to 0.765 ± 0.062 mm-1, which is comparable to that of conventional rigid shielding materials. In particular, the addition of 10 wt % p-BNNTs to agarose results in excellent form-factor flexibility, neutron shielding, and mechanical properties, thus rendering it a promising candidate for the nuclear industry.

Ultrasound stimulated piezoelectric barium titanate and boron nitride nanotubes in nonconductive poly-ε-caprolactone nanofibrous scaffold for bone tissue engineering

Nanomaterials can provide unique solutions for the problems experienced in tissue engineering by improving a scaffold's physico-bio-chemical properties. With its piezoelectric property, bone is an active tissue with easy adaptation and remodeling through complicated mechanisms of electromechanical operations. Although poly(ε-caprolactone) (PCL) is an excellent polymer for bone tissue engineering, it is lack of conductivity. In this study, piezoelectric barium titanates (BaTiO3) and boron nitride nanotubes (BNNTs) are used as ultrasound (US) stimulated piezoelectric components in PCL to mimic piezoelectric nature of bone tissue. Electric-responsive Human Osteoblast cells on the scaffolds were stimulated by applying low-frequency US during cell growth. Biocompatibility, cell adhesion, alkaline phosphatase activities and mineralization of osteoblast cells on piezo-composite scaffolds were investigated. BaTiO3or BNNTs as reinforcement agents improved physical and mechanical properties of PCL scaffolds.In vitrostudies show that the use of BaTiO3or BNNTs as additives in non-conductive scaffolds significantly induces and increases the osteogenic activities even without US stimulation. Although BaTiO3is one of the best piezoelectric materials, the improvement is more dramatic in the case of BNNTs with the increased mineralization, and excellent chemical and mechanical properties.

A new strategy for making a sensitive sensor for aspirin drug: first-principles investigations by using pure and metal-doped BN nano-heterostructures

The present study used the DFT method to investigate aspirin's intermolecular interactions with boron nitride (BN) nanotubes modified with aluminum, gallium, and zinc. Our experiments obtained adsorption energy of -40.4 kJ/mol for aspirin on BN nanotubes. By doping each of the above metals on the surface of the BN nanotube, the aspirin adsorption energy increased dramatically. For BN nanotubes doped with Al, Ga, and Zn, this energy was -255, -251, and -250 kJ/mol. Thermodynamic analyses proved that all surface adsorptions are exothermic and spontaneous. Nanotubes' electronic structures and dipole moments have been examined following aspirin adsorption. In addition, AIM analysis has been performed for all systems in order to understand how the links were formed. According to the obtained results, BN nanotubes doped with metals, as mentioned previously, have a very high electron sensitivity to aspirin. These nanotubes can therefore be used to manufacture aspirin-sensitive electrochemical sensors.Communicated by Ramaswamy H. Sarma.

Extrusion-Based Bioprinted Boron Nitride Nanotubes Reinforced Alginate Scaffolds: Mechanical, Printability and Cell Viability Evaluation

Alginate (Alg) hydrogels are commonly used as bioinks in 3D bioprinting. However, one of the significant drawbacks of using Alg hydrogels is their unstable mechanical properties. In this study, a novel hydrogel-based ink composed of Alg reinforced with functionalised boron nitride nanotubes (f-BNNTs) was developed and systematic quantitative characterisation was conducted to validate its printability, physiochemical properties and biocompatibility. The printability, contact angle and mechanical test results indicated good structural stability of the scaffolds. The thermal stability of the scaffolds increased with the incorporation of f-BNNTs into Alg. Human embryonic kidney cells (HEK 293T) were seeded on the scaffolds and the cell viability was recorded for 24, 48 and 72 h. Quantitative studies showed a slight effect on toxicity with a higher concentration of BNNTs in scaffolds. The results suggest that the 3D printable f-BNNTs reinforced Alg could be used as bioink for tissue engineering applications with further studies on biocompatibility.

Boron nitride nanotube precursor formation during high-temperature synthesis: kinetic and thermodynamic modelling

We performed integrated modelling of the chemical pathways of formation for boron nitride nanotube (BNNT) precursors during high-temperature synthesis in a B/N₂mixture. Integrated modelling includes quantum chemistry, Quantum-classical molecular dynamics, thermodynamic modelling, and kinetic approaches. We demonstrate that BN compounds are formed via the interaction of molecular nitrogen with small boron clusters, rather than through interactions with less reactive liquid boron. (This process can also be described as N₂molecule fixation.) Liquid boron evaporates to produce these boron clusters (B_mwithm≤ 5), which are subsequently converted into B_mN_nchains. The production of such chains is crucial to the growth of BNNTs because these chains form the building blocks of bigger and longer BN chains and rings, which are in turn the building blocks of fullborenes and BNNTs. Additionally, kinetic modelling revealed that B₄N₄and B₅N₄species in particular play a major role in the N₂molecule fixation process. The formation of these species via reactions with B₄and B₅clusters is not adequately described under the assumption of thermodynamic equilibrium, as is demonstrated in our kinetic modelling. Thus, the accumulation of both B₄N₄and B₅N₄depends on the background gas pressure and the gas cooling rate. Long BN chains and rings, which are precursors of the fullborene and BNNT growth, form via self-assembly of components B₄N₄and B₅N₄. Our modelling results-particularly the increased densities of B₄N₄and B₅N₄species at higher gas pressures-explain the experimentally observed effect of gas pressure on the yield of high-quality BNNTs. The catalytic role of hydrogen was also studied; it is shown that HBNH molecules can be the main precursor of BNNT synthesis in the presence of hydrogen.

Dynamic Behavior of Rotation Transmission Nano-System in Helium Environment: A Molecular Dynamics Study

The molecular dynamics (MD) method is used to investigate the influence of the shielding gas on the dynamic behavior of the heterogeneous rotation transmission nano-system (RTS) built on carbon nanotubes (CNTs) and boron nitride nanotube (BNNT) in a helium environment. In the heterogeneous RTS, the inner CNT acts as a rotor, the middle BNNT serves as a motor, and the outer CNT functions as a stator. The rotor will be actuated to rotate by the motor due to the interlayer van der Waals effects and the end effects. The MD simulation results show that, when the gas density is lower than a critical range, a stable signal of the rotor will arise on the output and the rotation transmission ratio (RRT) of RTS can reach 1.0, but as the gas density is higher than the critical range, the output signal of the rotor cannot be stable due to the sharp drop of the RRT caused by the large friction between helium and the RTS. The greater the motor input signal of RTS, the lower the critical working helium density range. The results also show that the system temperature and gas density are the two main factors affecting the RTS transmission behavior regardless of the size of the simulation box. Our MD results clearly indicate that in the working temperature range of the RTS from 100 K to 600 K, the higher the temperature and the lower the motor input rotation frequency, the higher the critical working helium density range allows.

Synthesis of Boron Nitride Nanotubes Using Plasma-Assisted CVD Catalyzed by Cu Nanoparticles and Oxygen

We found that oxidized Cu nanoparticles can catalyze the growth of boron nitride nanotubes from borazine via plasma-assisted chemical vapor deposition. The Raman spectra suggest that the formation of thin-walled nanotubes show a radial breathing mode vibration. The presence of oxygen in the plasma environment was necessary for the growth of the nanotubes, and a part of the nanotubes had a core shell structure with a cupper species inside it. In atomic resolution transmission electron microscope (TEM) images, Cu2O was found at the interface between the Cu-core and turbostratic BN-shell. The growth mechanism seemed different from that of carbon nanotube core-shell structures. Therefore, we pointed out the important role of the dynamic morphological change in the Cu2O-Cu system.

Boron Nitride Nanotube as an Antimicrobial Peptide Carrier: A Theoretical Insight

INTRODUCTION

Nanotube-based drug delivery systems have received considerable attention because of their large internal volume to encapsulate the drug and the ability to penetrate tissues, cells, and bacteria. In this regard, understanding the interaction between the drug and the nanotube to evaluate the encapsulation behavior of the drug in the nanotube is of crucial importance.

METHODS

In this work, the encapsulation process of the cationic antimicrobial peptide named cRW3 in the biocompatible boron nitride nanotube (BNNT) was investigated under the Canonical ensemble (NVT) by molecular dynamics (MD) simulation.

RESULTS

The peptide was absorbed into the BNNT by van der Waals (vdW) interaction between cRW3 and the BNNT, in which the vdW interaction decreased during the simulation process and reached the value of -142.7 kcal·mol-1 at 4 ns.

DISCUSSION

The increase in the potential mean force profile of the encapsulated peptide during the pulling process of cRW3 out of the nanotube showed that its insertion into the BNNT occurred spontaneously and that the inserted peptide had the desired stability. The energy barrier at the entrance of the BNNT caused a pause of 0.45 ns when half of the peptide was inside the BNNT during the encapsulation process. Therefore, during this period, the peptide experienced the weakest movement and the smallest conformational changes.

Enhanced In-Plane Thermal Conductance of Thin Films Composed of Coaxially Combined Single-Walled Carbon Nanotubes and Boron Nitride Nanotubes

Carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) are one-dimensional materials with high thermal conductivity and similar crystal structures. Additionally, BNNTs feature higher thermal stability in air than CNTs. In this work, a single-walled carbon nanotube (SWCNT) film was used as a template to synthesize a BNNT coating by the chemical vapor deposition (CVD) method to form a coaxial heterostructure. Then, a contact-free steady-state infrared (IR) method was adopted to measure the in-plane sheet thermal conductance of the as-synthesized film. The heterostructured SWCNT-BNNT film demonstrates an enhanced sheet thermal conductance compared with the bare SWCNT film. The increase in sheet thermal conductance shows a reverse relationship with SWCNT film transparency. An enhancement of over 80% (from ∼3.6 to ∼6.4 μW·K^-1·sq^-1) is attained when the BNNT coating is applied to an SWCNT film with a transparency of 87%. This increase is achieved by BNNTs serving as an additional thermal conducting path. The relationship between the thermal conductance increase and transparency of the SWCNT film is studied by a structured modeling of the SWCNT film. We also discuss the effect of annealing on the thermal conductance of SWCNTs before BNNT growth. Along with the preservation of high electrical conductance, the enhanced thermal conductance of the heterostructured SWCNT-BNNT films makes them a promising building block for thermal and optoelectronic applications.

Purification of Boron Nitride Nanotubes Enhances Biological Application Properties

Commercially available boron nitride nanotubes (BNNTs) and their purified form (pBNNTs) were dispersed in aqueous solutions with various dispersants, and their cytotoxicity and drug encapsulation capacity were monitored. Our data suggest that pBNNTs showed an average increase in dispersibility of 37.3% in aqueous solution in the presence of 10 different dispersants. In addition, 100 μg of pBNNTs induced an average decrease in cytotoxicity of 27.4% compared to same amount of BNNTs in normal cell lines. The same amount of pBNNTs can encapsulate 10.4-fold more drug (camptothecin) compared to BNNTs. These data suggest that the purification of BNNTs improves several of their properties, which can be applied to biological experiments and are thus essential in the biological application of BNNTs.

Dispersion of Boron Nitride Nanotubes by Pluronic Triblock Copolymer in Aqueous Solution

Boron nitride nanotubes (BNNTs) have been of interest for their excellent thermal, electrical, and mechanical properties, and they have a broad spectrum of potential applications, such as in piezoelectric materials, reinforcement of materials, and electrothermal insulation materials. For practical use of BNNTs, it is desirable to disperse them in aqueous solution, which improves convenience of handling. However, it is still difficult to make a homogenous and stable BNNT dispersion in aqueous solution, due to their strong van der Waals interactions and hydrophobic surface. To solve these problems, we used Pluronic P85 and F127, which have both hydrophilic groups and hydrophobic groups. Here, we report the wrapped structure of a Pluronic polymer-BNNT dispersion by using small-angle neutron scattering, UV–Vis spectroscopy, thermogravimetric analysis, and atomic force microscopy.

Comparative prediction of binding affinity of Hydroxyurea anti-cancer to boron nitride and carbon nanotubes as smart targeted drug delivery vehicles

In this study, the adsorption of Hydroxyurea (HU) onto the inner and outer surfaces of boron nitride and carbon nanotubes (CNTs) was investigated using the density functional theory calculations and molecular dynamics (MDs) simulations in aqueous solution. The values of the adsorption energy show that HU molecule is preferentially adsorbed inside of boron nitride and CNTs with the molecular axis parallel to the tubes axis, which means that the cavity of nanotubes is favorable for encapsulation of this drug. Also, it was found that the HU/boron nitride nanotube (BNNT) system is more stable than the HU/CNT system. The stability of the complexes of HU/ BNNT attributed to the formation of the intermolecular hydrogen bonds between the H atoms of HU molecule and the N atoms of BNNT, which is confirmed by Bader's quantum theory of atoms in molecules. The natural bond orbital analysis shows the charge transfers occur from HU molecule to nanotubes in all complexes. Moreover, the adsorption of HU molecule on the surfaces of the nanotubes was investigated by explicit water models. Also, the adsorption behavior of HU on the functionalized boron nitride and CNTs is investigated to design and develop new nanocarriers for biomedical applications. Furthermore, MDs simulations are examined in the presence of one and two drug molecules. The obtained results illustrate that the lowest value of Lennard-Jones (L-J) energy between drug and nanotubes exist in the simulation system with two drug molecules.

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers

In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, G_IC, by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs) and boron nitride nanotubes (BNNTs) were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

Thermal Conductivity Enhancement of Coaxial Carbon@Boron Nitride Nanotube Arrays

We demonstrate the thermal conductivity enhancement of the vertically aligned carbon nanotube (CNT) arrays (from ∼15.5 to 29.5 W/mK, ∼90% increase) by encapsulating outer boron nitride nanotube (BNNT, 0.97 nm-thick with ∼3-4 walls). The heat transfer enhancement mechanism of the coaxial C@BNNT was further revealed by molecular dynamics simulations. Because of their highly coherent lattice structures, the outer BNNT serves as additional heat conducting path without impairing the thermal conductance of inner CNT. This work provides deep insights into tailoring the heat transfer of arbitrary CNT arrays and will enable their broader applications as thermal interface material.

Noncovalent Functionalization of Boron Nitride Nanotubes in Aqueous Media Opens Application Roads in Nanobiomedicine

Boron nitride nanotubes (BNNTs) are of intense scientific interest due to their unique physiochemical properties and prospective applications in various nanotechnologies, particularly nanobiomedicine. A critical problem hampering the application processing of BNNTs is the outer sidewall functionalization, which is primarily acquired to lead BNNTs dispersible in various solvents. Furthermore, the surface of BNNTs should be intelligently designed and precisely controlled to satisfy the specific demands of different applications. For these purposes, covalent and noncovalent approaches have been factually developed to help to extend the full potential of applications. Importantly, wrapping the outermost sidewall of BNNTs with either water-soluble polymers or biomolecules through weak noncovalent interactions has been proved to be efficient for giving BNNTs considerable dispersity in aqueous media, and endowing novel chemical functions to BNNTs with almost no change in their pristine physiochemical properties. This article summarizes recent progress in this field and addresses future perspectives on the noncovalent functionalization of BNNTs for promoting their application processing in various bio-related nanotechnologies.

Synthesis of boron nitride nanotubes from unprocessed colemanite

Colemanite (Ca2B6O11·5H2O) is a natural and new precursor material for the synthesis of boron nitride nanotubes (BNNTs). BNNTs have been synthesized from unprocessed colemanite for the first time. The reaction parameters such as time, catalyst type, catalyst amount and temperature were optimized. It was found that the BNNT formation follows the base growth mechanism, which was initiated with a complex of boron nitride (BN) and iron atoms. The obtained BNNTs were characterized by using SEM, TEM, and spectroscopic techniques such as UV-vis, Raman, FTIR and XRD. The BNNTs were randomly oriented and multi-walled with an outer diameter of 10-30 nm and a wall thickness of 5 nm. This novel BNNT synthesis method can be used to obtain high yield, low cost and pure BNNTs.

Mechanically activated catalyst mixing for high-yield boron nitride nanotube growth

Boron nitride nanotubes (BNNTs) have many fascinating properties and a wide range of applications. An improved ball milling method has been developed for high-yield BNNT synthesis, in which metal nitrate, such as Fe(NO3)3, and amorphous boron powder are milled together to prepare a more effective precursor. The heating of the precursor in nitrogen-containing gas produces a high density of BNNTs with controlled structures. The chemical bonding and structure of the synthesized BNNTs are precisely probed by near-edge X-ray absorption fine structure spectroscopy. The higher efficiency of the precursor containing milling-activated catalyst is revealed by thermogravimetric analyses. Detailed X-ray diffraction and X-ray photoelectron spectroscopy investigations disclose that during ball milling the Fe(NO3)3 decomposes to Fe which greatly accelerates the nitriding reaction and therefore increases the yield of BNNTs. This improved synthesis method brings the large-scale production and application of BNNTs one step closer.