Boron nitride nanotubes and nanosheets

Nano-enabled gas separation membranes: Advancing sustainability in the energy-environment Nexus

Gas separation membranes serve as crucial to numerous industrial processes, including gas purification, energy production, and environmental protection. Recent advancements in nanomaterials have drastically revolutionized the process of developing tailored gas separation membranes, providing unreachable levels of control over the performance and characteristics of the membrane. The incorporation of cutting-edge nanomaterials into the composition of traditional polymer-based membranes has provided novel opportunities. This review critically analyses recent advancements, exploring the diverse types of nanomaterials employed, their synthesis techniques, and their integration into membrane matrices. The impact of nanomaterial incorporation on separation efficiency, selectivity, and structural integrity is evaluated across various gas separation scenarios. Furthermore, the underlying mechanisms behind nanomaterial-enhanced gas transport are examined, shedding light on the intricate interactions between nanoscale components and gas molecules. The review also discusses potential drawbacks and considerations associated with nanomaterial utilization in membrane development, including scalability and long-term stability. This review article highlights nanomaterials' significant impact in revolutionizing the field of selective gas separation membranes, offering the potential for innovation and future directions in this ever-evolving sector.

Thermal Rectification in Graphene-Boron Nitride Nanotube Hybrid Structures: An Independent Control Mechanism for Forward and Backward Heat Flux

The weak van der Waals interactions in the out-of-plane direction result in markedly low thermal conductivity in one-dimensional (1D) and two-dimensional (2D) materials, which substantially restricts their applications. Developing three-dimensional (3D) columnar hybrid structures, featuring high thermal conductivity both within and beyond the plane, effectively addresses this challenge. This study investigated a 3D hybrid structure composed of graphene and boron nitride nanotubes (GR-BNNTs) using non-equilibrium molecular dynamics simulations. This approach allowed the examination of the formation mechanisms and key factors influencing thermal rectification (TR) in these materials. Our findings reveal a novel mechanism for independently regulating forward and backward heat fluxes in GR-BNNTs. By manipulating the thermal properties of the BNNTs and the graphene layer, the TR ratio can be controlled flexibly. Additionally, we identify specific strategies for independently adjusting the heat flux, such as altering the intercolumn distance of BNNTs, which impacts the backward flux merely, while applying strain to affect the forward flux merely. This research introduces a novel concept of independent regulation of forward and backward heat fluxes, providing significant insights into phonon thermal transport in 3D hybrid structures.

Water molecules in boron nitride interlayer space: ice and hydrolysis in super confinement

Development of nano-sized channels and filters in the recent years has made the role of water immensely important as water molecules affect their performance and durability. Here, we take advantage of molecular dynamics and density functional theory methods to demonstrate the shift in behavior of water molecules confined between hexagonal boron nitride (HBN) sheets spaced at 3.0 to 6.5 Å. Our results demonstrate that lower interlayer spaces cause higher amounts of charge transferred between the species, while at extreme degrees of confinement, these interactions cause the disintegration of trapped water molecules. Consequently, the inner face of the HBN sheets is functionalized with hydroxyl groups, releasing hydrogens in the form of protons that travel the interlayer space by Grotthuss mechanism. This is the first-hand evidence of a mechanical form of hydrolysis that corresponds with a nucleophilic attack (on boron atoms) to relieve water from extreme confined conditions. This process unveils a previously unknown behavior of water within extremely confined spaces and reveals new considerations concerning nanofilters and nanochannels.

Assessment of the drug delivery potential of graphene, boron nitride and their in-plane doped structures for hydroxyurea anti-cancer drug via DFT study

Globally, cancer is the most common cause of mortality among all deadly diseases. As a result, a nanotechnology-based drug delivery system is used to improve the efficacy of cancer treatment, which provides an improved therapeutic index and delivers multiple drugs directly to the tumor site. In the present work, DFT calculations were employed to investigate the surface adsorption of a hydroxyurea (HU) anticancer drug on pristine graphene (GP), boron nitride (B24N24), and doped GP by replacing some of its carbon atoms with boron (B) and nitrogen (N) atoms to form C30B9N9, C16B16N16, and C6B21N21 nanosheets. In gas media, HU is adsorbed on these C30B9N9, C16B16N16, C6B21N21, and B24N24 nanosheets with adsorption energies of -0.70, -3.03, -2.47, and -1.96 eV, respectively. Alternatively, in water solvent media, the adsorption energies of C30B9N9, C16B16N16, C6B21N21, and B24N24 are -0.82, -0.29, -0.15, and -0.26 eV, respectively. The energy gaps of the nanosheets were found to be 0.288, 0.174, 0.14, and 4.562 eV before adsorption, respectively. After the adsorption of HU on the proposed nanosheets, the energy gap was reduced to 0.15 eV for C16B16N16. According to the DOS spectra, noticeable peaks appeared in the Fermi level after the adsorption of HU on the nanosheets, which indicates the reduction of the energy gap. Quantum molecular analysis predicted that the chemical potential, electrophilicity index, and nucleophilicity index of C16B16N16 increased, whereas global hardness decreased, indicating high reactivity. Therefore, it can be concluded that among the proposed nanosheets, C16B16N16 would be an appropriate carrier for the HU drug.

Unidirectional hyperbolic whispering-gallery phonon-polariton excitation in boron nitride nanotubes

In two-dimensional (2D) hyperbolic materials, energy is directed into their deep subwavelength polaritonic modes through four narrow beams. Hyperbolic whispering-gallery mode nanocavity-confined phonon polaritons (PhPs) display a strongly enhanced light-matter interaction in the infrared regime. Particularly, the unidirectional phonon-polarization excitation in nanocavities has a potential application value in an on-chip integrated optical circuit design, efficient optical sensors, and enhanced spectral technology. Here, we explore the hyperbolic whispering-gallery mode PhPs on the cross section of a hexagonal BN nanotube (BNNT) and demonstrate that efficient unidirectional excitation can be achieved using a circularly polarized electric dipole, combining with optical spin-orbit coupling. Our results demonstrated that the undirectionality of the hyperbolic polariton propagation in a nanocavity can be conveniently achieved, independent of the structure symmetry of the nanocavity, providing potential applications in nanoscale light propagation, on-chip optical devices, and communication.

Polymeric Nanocomposites of Boron Nitride Nanosheets for Enhanced Directional or Isotropic Thermal Transport Performance

Polymeric composites with boron nitride nanosheets (BNNs), which are thermally conductive yet electrically insulating, have been pursued for a variety of technological applications, especially those for thermal management in electronic devices and systems. Highlighted in this review are recent advances in the effort to improve in-plane thermal transport performance in polymer/BNNs composites and also the growing research activities aimed at composites of enhanced cross-plane or isotropic thermal conductivity, for which various filler alignment strategies during composite fabrication have been explored. Also highlighted and discussed are some significant challenges and major opportunities for further advances in the development of thermally conductive composite materials and their mechanistic understandings.

Facile covalent functionalization of boron nitride nanotubes via coupling reaction

A broad range of functionalized boron nitride nanotubes has been synthesized using a facile method based on the coupling reaction between BNNT and arenediazonium tetrafluoroborate derivatives. The formation of covalent bonds between nanotubes and organic moieties results in homogeneous dispersions in organic solvents, such as N,N'-dimethylformamide, acetone, isopropanol, and tetrahydrofuran. Digital images demonstrated improved and stabilized dispersions lasting for several days, while TEM analysis indicated no breakdown of nanotubes due to the mild reaction conditions employed. The functionalization process was further confirmed through additional characterization, employing FTIR, XPS, and TGA. Surface-functionalized materials exhibited a significant weight percentage of functionality, reaching up to 21.8% according to TGA.

Hazard assessment of hexagonal boron nitride and hexagonal boron nitride reinforced thermoplastic polyurethane composites using human skin and lung cells

Hexagonal boron nitride (hBN) is an emerging two-dimensional material attracting considerable attention in the industrial sector given its innovative physicochemical properties. Potential risks are associated mainly with occupational exposure where inhalation and skin contact are the most relevant exposure routes for workers. Here we aimed at characterizing the effects induced by composites of thermoplastic polyurethane (TPU) and hBN, using immortalized HaCaT skin keratinocytes and BEAS-2B bronchial epithelial cells. The composite was abraded using a Taber® rotary abraser and abraded TPU and TPU-hBN were also subjected to photo-Fenton-mediated degradation mimicking potential weathering across the product life cycle. Cells were exposed to the materials for 24 h (acute exposure) or twice per week for 4 weeks (chronic exposure) and evaluated with respect to material internalization, cytotoxicity, and proinflammatory cytokine secretion. Additionally, comprehensive mass spectrometry-based proteomics and metabolomics (secretomics) analyses were performed. Overall, despite evidence of cellular uptake of the material, no significant cellular and/or protein expression profiles alterations were observed after acute or chronic exposure of HaCaT or BEAS-2B cells, identifying only few pro-inflammatory proteins. Similar results were obtained for the degraded materials. These results support the determination of hazard profiles associated with cutaneous and pulmonary hBN-reinforced polymer composites exposure.

High-yield synthesis of hydroxylated boron nitride nanosheets and their utilization in thermally conductive polymeric nanocomposites

Hexagonal boron nitride nanosheets (BNNSs) possess remarkable potential for various applications due to their unprecedented properties. However, the scalable production of BNNSs with both expansive surface and high solubility continues to present a significant challenge. Herein, we propose an innovative and efficient two-step method for manufacturing hydroxyl-functionalized BNNSs (OH-BNNSs). Initially, hydroxyl groups are covalently attached to bulk hexagonal boron nitride (h-BN) surfaces through H2O2 treatment. Then, the hydroxyl-functionalized h-BN undergoes exfoliation on account of a sudden increase in interlayer gas pressure generated by the vigorous decomposition of H2O2 in alkali solutions, resulting in the creation of OH-BNNSs. This approach produces relatively large flakes with an average dimension of 1.65 μm and a high yield of 45.2%. The resultant OH-BNNSs exhibit remarkable stability and dispersibility in a range of solvents. Their integration into thermoplastic polyurethane (TPU) significantly enhances both thermal conductivity and stability, attributed to the excellent compatibility with the resin matrix. This study represents a significant advancement in the functionalization and exfoliation of h-BN, opening new avenues for its promising applications in polymer composites.

Zigzag boron nitride nanoribbon doped with carbon atom for giant magnetoresistance and rectification behavior based nanodevices

Using the principles of density functional theory (DFT) and nonequilibrium Green's function (NEGF), We thoroughly researched carbon-doped zigzag boron nitride nanoribbons (ZBNNRs) to understand their electronic behavior and transport properties. Intriguingly, we discovered that careful doping can transform carbon-doped ZBNNRs into a spintronic nanodevice with distinct transport features. Our model showed a giant magnetoresistance (GMR) up to a whopping 105 under mild bias conditions. Plus, we spotted a spin rectifier having a significant rectification ratio (RR) of 104 . Our calculated transmission spectra have nicely explained why there's a GMR up to 105 for spin-up current at biases of - 1.2 V, - 1.1 V, and - 1.0 V, and also accounted for a GMR up to 103 -105 for spin-down current at biases of 1.0 V, 1.1 V, and 1.2 V. Similarly, the transmission spectra elucidate that at biases of 1.0 V, 1.1 V, and 1.2 V for spin-up, and at biases of 1.1 V and 1.2 V for spin-down in APMO, the RRs reach 104 . Our research shines a light on a promising route to push forward the high-performance spintronics technology of ZBNNRs using carbon atom doping. These insights hint that our models could be game-changers in the sphere of nanoscale spintronic devices.

Thermal Transport Phenomena in PEGDA-Based Nanocomposite Hydrogels Using Atomistic and Experimental Techniques

Poly(ethylene glycol) diacrylate (PEGDA) hydrogel is a very peculiar, fascinating material with good chemical stability and biocompatibility. However, the poor thermal transport phenomenon in PEGDA, limits its performance in cartilage replacement and developing therapies for treating burns. In this article, a combined experimental and atomistic approach was adopted to investigate the thermal transport phenomena in PEGDA hydrogel with different weight concentrations of boron nitride nanoplatelets as a function of water content. The incorporation of boron nitride nanofillers helps in enhancing the thermal conductivity of PEGDA hydrogels, and the reinforcement effect was more dominating at lower water content. Experimental investigation was complemented with molecular dynamics-based studies to capture the effect of defective (bicrystalline) boron nitride nanosheets on the interfacial thermal conductance in PEGDA hydrogels. It can be concluded from the simulations that defective nanosheets are superior reinforcement for enhancing the thermal transport in PEGDA hydrogels, and this is independent of the water content. These biocompatible boron nitride nanoparticle (BNNP)-incorporated PEGDA hydrogels with enhanced thermal conductivity are promising materials in addressing locally overheating tissues such as cartilage replacement. They may have comprehensive utility for biomedical applications such as tissue engineering, drug delivery, biosensors, and burn therapy.

On the Determination of Elastic Properties of Single-Walled Nitride Nanotubes Using Numerical Simulation

In recent years, tubular nanostructures have been related to immense advances in various fields of science and technology. Considerable research efforts have been centred on the theoretical prediction and manufacturing of non-carbon nanotubes (NTs), which meet modern requirements for the development of novel devices and systems. In this context, diatomic inorganic nanotubes formed by atoms of elements from the 13th group of the periodic table (B, Al, Ga, In, Tl) and nitrogen (N) have received much research attention. In this study, the elastic properties of single-walled boron nitride, aluminium nitride, gallium nitride, indium nitride, and thallium nitride nanotubes were assessed numerically using the nanoscale continuum modelling approach (also called molecular structural mechanics). The elastic properties (rigidities, surface Young's and shear moduli, and Poisson's ratio) of nitride nanotubes are discussed with respect to the bond length of the corresponding diatomic hexagonal lattice. The results obtained contribute to a better understanding of the mechanical response of nitride compound-based nanotubes, covering a broad range, from the well-studied boron nitride NTs to the hypothetical thallium nitride NTs.

Eco-Friendly Production of Boron Nitride Nanosheets via Deep Eutectic Solvents and Their Application in Enhancing Thermal Conductivity of PVDF Composites

Boron nitride nanosheets (BNNS) are expected to be ideal fillers because of their high thermal conductivity and excellent electrical insulation. However, it is still an open challenge to produce BNNS on a large scale using ecofriendly solvents. Here, first, we demonstrate an effective liquid exfoliation method for producing BNNS via utilizing deep eutectic solvents (DES) composed of D,L-menthol and various acids with the assistance of ultrasonication. The results show that the BNNSs with sizes of 1-2 μm in width and 6-8 nm in thickness were successfully exfoliated with a DES formulation of D,L-menthol and decanoic acid. Second, the obtained BNNSs were used for fabricating 1,6-hexanediol diacrylate@polydopamine functionalized BNNS (HDDA@BNNSs-PDA) core-shell microspheres via a Pickering emulsion method. Furthermore, these microspheres were incorporated into a polyvinylidene fluoride (PVDF) matrix to construct 3D thermally conductive networks, leading to a substantial enhancement in the thermal conductivity of the resulting composites. Impressively, the composites with only 25 wt % of BNNS loading reach a high thermal conductivity of 3.20 W/m K, which is a 1500% increase over the pure polymer matrix. This work not only provides a significant way for producing BNNSs ecofriendly but also demonstrates a tactic for constructing 3D thermally conductive networks.

Harnessing halogen bond donors for enhanced nitrogen reduction: a case study on metal-free boron nitride single-atom catalysts

Developing efficient catalysts for ammonia synthesis is increasingly crucial but remains a formidable challenge due to the lack of robust design criteria, particularly in addressing the activity and selectivity issues, especially in electrochemical nitrogen reduction reactions (NRR). In this study, we systematically investigated the catalytic potential of hexagonal boron nitride (BN) embedded with non-metal (C, Si, P and S) atoms as an electrocatalyst for the nitrogen reduction reaction using density functional theory (DFT) computations. The preference for non-metal-doped BN nanomaterials stems from their ability to suppress hydrogen evolution and their environmentally friendly nature, in contrast to transition metals. Among the designed single-atom catalysts (SACs), Si-doped boron nitride (SiBBN) exhibits a favorable inclination toward activating nitrogen, which is determined by the combination of advantageous molecular orbital coupling and formation of a covalent bond with the N2 molecule. Under thermal conditions, the first protonation step emerges as the rate-determining step (22.66 kcal mol-1) for SiBBN. Conversely, under electrochemical conditions, the final elementary step becomes the potential-determining step (PDS) with 2.38 eV. We explored the impact of the exogenous addition of Lewis acids (alkali metal ions, neutral boron Lewis acids, and halogen bond donors) on modulating the electrochemical NRR activity. Our results highlight the pivotal role of halogen bond donors as catalytic promoters in facilitating electron density transfer through activated N2, establishing a push-pull charge transfer mechanism that populates the distal nitrogen more than the proximal nitrogen. This facilitates the potential requirements for the first reduction step. The synergistic effect of both halogen bonding and hydrogen bonding interactions in the final reduction step was proven to be the main determinant for a significant reduction in the PDS from 2.38 to 0.10 V. Notably, this study unveils the pioneering role of halogen bond donors as promoters for NRR, providing valuable insights into the development of robust metal-free catalysts and promoters in experimental research.

Reversible actuation of α-borophene nanoscrolls

In this work, we proposed and investigated the structural and electronic properties of boron-based nanoscrolls (armchair and zigzag) using the DFTB+ method. We also investigated the electroactuation process (injecting and removing charges). A giant electroactuation was observed, but the results show relevant differences between the borophene and carbon nanoscrolls. The molecular dynamics simulations showed that the scrolls are thermally and structurally stable for a large range of temperatures (up to 600 K), and the electroactuation process can be easily tuned and can be entirely reversible for some configurations.

Sonochemically synthesized black phosphorus nanoparticles: a promising candidate for piezocatalytic antibacterial activity with enhanced dielectric properties

The drawbacks inherent to traditional antibacterial therapies, coupled with the escalating prevalence of multi-drug resistant (MDR) microorganisms, have prompted the imperative need for novel antibacterial strategies. Accordingly, the emerging field of piezocatalysis in semiconductors harnesses mechanical stress to drive chemical reactions by utilizing piezo-generated free charge carriers, presenting a promising technology. To the best of our knowledge, this study is the first to provide a comprehensive overview of the eradication of pathogenic S. aureus bacteria using few-layer black phosphorus (SCBP) piezo catalyst under mechanical stimuli, along with the exploration of temperature dependent dielectric properties. The synthesis of the piezo catalysts involved a one-step cost-effective sonochemical method, and its structural, morphological, elemental, optical, and overall polarization properties were thoroughly characterized and compared with the traditional method-derived product (TABP). The synthesis-introduced defects, reduced crystalline diameters, modified bandgap (1.76 eV), nanoparticle aggregation, photoluminescence quenching, along with interfacial polarization, synergistically contribute to SCBP's exceptional dielectric response (4.596 × 107 @40 Hz), which in turn enhanced the piezocatalytic activity. When subjected to soft ultrasound stimulation at 15 kHz, the piezo catalyst SCBP demonstrated significant ROS-mediated antibacterial activity, resulting in a ∼94.7% mortality rate within 40 minutes. The impact of this study extends to cost-effective energy storage devices and advances in antibacterial therapy, opening new dimensions in both fields.

Adhesion Energy-Assisted Low Contact Thermal Resistance Epoxy Resin-Based Composite

Although intense efforts have been devoted to the development of thermally conductive epoxy resin composites, most previous works ignore the importance of the contact thermal resistance between epoxy resin composites and mating surfaces. Here, we report on epoxy resin/hexagonal boron nitride (h-BN) composites, which show low contact thermal resistance with the contacting surface by tuning adhesion energy. We found that adhesion energy increases with increasing the ratio of soybean-based epoxy resin/amino silicone oil and h-BN contents. The adhesion energy has a negative correlation with the contact thermal resistance; that is, enhancing the adhesion energy will lead to reduced contact thermal resistance. The contact thermal conductance increases with the h-BN contents and is low to 0.025 mm2·K/W for the epoxy resin/60 wt % h-BN composites, which is consistent with the theoretically calculated value. By investigating the wettability and chain dynamics of the epoxy resin/h-BN composites, we confirm that the low contact thermal resistance stems from the increased intermolecular interaction between the epoxy resin chains. The present study provides a practical approach for the development of epoxy resin composites with enhanced thermal conductivity and reduced contact thermal resistance, aiming for effective thermal management of electronics.

Highly Thermally Conductive Flexible Biomimetic APTES-BNNS/BC Nanocomposite Paper by Sol-Gel-Film Technology

Owing to the evolution of 5G technology, new energy vehicles, flexible electronics, miniaturization and integration of microelectronic devices, high-frequency and high-power devices, and thermal management of materials must consider additional limitations such as electrical insulation, excellent transverse heat transfer, flexibility, and weight. Boron nitride nanosheets (BNNSs) are ideal insulating materials with high thermal conductivity. However, the problem of the 3D thermal conductivity pathway and toughness strength of nanocomposite paper loaded with inorganic thermal conductivity fillers remains a huge challenge. In this study, we propose a new method for preparing ultrathin, large, and uniformly thick BNNS for quantitative production. Bulk hexagonal boron nitride (hBN) layers were exfoliated using a simple and low-cost hydrothermal reaction, and large-scale fewer-layered BNNSs were efficiently prepared by ball milling with a high yield (up to 80%). Based on the aforementioned step, a flexible insulating composite film with high thermal conductivity and a natural "brick-mud" shell structure was constructed via the sol-gel-film conversion method. After prestretching and hot-pressing treatment, the hydrogels became denser, and the modified BNNS formed a three-dimensional (3D) network structure with an ordered orientation and interconnections in the bacterial cellulose (BC) matrix. After 100 folding cycles, the tensile strength of the nanofiber composite film reached 53 MPa, and the strength retention rate exceeded 42%. By optimizing the modified BNNS content, the thermal conductivity reached 24 W/(m·K). This simple approach has wide application potential in the next-generation electronic devices, providing options for designing thermal interface materials with excellent electrical insulation, high thermal stability, and flexibility.

Synthesis Landscapes for Ammonia Borane Chemical Vapor Deposition of h-BN and BNNT: Unraveling Reactions and Intermediates from First-Principles

Planar hexagonal boron nitride (h-BN) and tubular BN nanotube (BNNT), known for their superior mechanical and thermal properties, as well as wide electronic band gap, hold great potential for nanoelectronic and optoelectronic devices. Chemical vapor deposition has demonstrated the best way to scalable synthesis of high-quality BN nanomaterials. Yet, the atomistic understanding of reactions from precursors to product-material remains elusive, posing challenges for experimental design. Here, performing first-principles calculations and ab initio molecular simulations, we explore pyrolytic decomposition pathways of the most used precursor ammonia borane (H3BNH3, AB) to BN, in gas-phase and on Ni(111) or amorphous boron (for BNNT growth) surfaces, for comparison. It reveals that in the gas phase, a pair of AB molecules cooperate to form intermediate NH3 and ammonia diborane, which further dissociates into H2BNH2, accompanied by critical BH4- and NH4+ ions. These ions act as H scavengers facilitating H2BNH2 dehydrogenation into HBNH. The consequent HBNH directly feeds BN flake growth by reacting with the crystal edge, while the addition of H2BNH2 to the edge is prohibited at 1500 K. In contrast, on Ni and boron surfaces, AB monomer dehydrogenates stepwise, deeper, yielding BNH and BN dimer as the primary building unit. Our study maps out three typical experimental conditions regarding the dissociation of AB-precursor, providing insights into the underlying reaction mechanisms of gas-phase precursors, to help as guidelines for the experimental growth of BN nanomaterials.

Himalayan lichen biomass for green synthesis of silver nanocolloids: growth kinetics, effect of pH and metal sensing

Lichen is one of the most abundant non-vascular biomasses; however, a systematic study on the application of biomass in nanomaterial synthesis is very limited. In this study, an aqueous lichen extract was obtained from Hypotrachyna cirrhata, one of the most abundant Himalayan lichen biomasses, using a simple cold percolation method. The effects of extract-to-silver nitrate mixing ratio, pH and waiting time on the growth and stability of nanoparticles were systematically explored. The rate constant for bio-reduction was found to be 5.3 × 10-3 min-1. Transmission electron microscopy showed a narrow particle size distribution with a mean particle size of 11.1 ± 3.6 nm (n = 200). The X-ray diffraction and selected area electron diffraction techniques confirmed the formation of cubic crystals. The synthesized colloidal solution showed excellent response to Hg2+ and Cu2+ ions in spiked water samples. The limit of detection and calibration sensitivity for Hg2+ and Cu2+ ions were found to be 1 and 5 mg l-1 and 2.9 × 10-3 and 1.6 × 10-3 units ppm-1, respectively. These findings suggested that spherical silver nanoparticles with a narrow particle size distribution can be synthesized on a laboratory scale using an aqueous H. cirrhata lichen extract, and the colloidal solution can be used for the detection of selected heavy metals in water samples.

Environmental and Health Impacts of Graphene and Other Two-Dimensional Materials: A Graphene Flagship Perspective

Two-dimensional (2D) materials have attracted tremendous interest ever since the isolation of atomically thin sheets of graphene in 2004 due to the specific and versatile properties of these materials. However, the increasing production and use of 2D materials necessitate a thorough evaluation of the potential impact on human health and the environment. Furthermore, harmonized test protocols are needed with which to assess the safety of 2D materials. The Graphene Flagship project (2013-2023), funded by the European Commission, addressed the identification of the possible hazard of graphene-based materials as well as emerging 2D materials including transition metal dichalcogenides, hexagonal boron nitride, and others. Additionally, so-called green chemistry approaches were explored to achieve the goal of a safe and sustainable production and use of this fascinating family of nanomaterials. The present review provides a compact survey of the findings and the lessons learned in the Graphene Flagship.

Growth methodologies of boron nitride nanotubes and their neutron shielding applications: a review

This review provides a comprehensive overview of the growth methodologies and neutron shielding applications of Boron Nitride Nanotubes (BNNTs). BNNTs have garnered significant attention because of their unique combination of high thermal stability, mechanical strength, and exceptional neutron absorption properties. Synthesis methods for BNNTs, including laser ablation, thermal plasma treatment, chemical vapour deposition (CVD), and ball milling have been thoroughly examined, highlighting their mechanisms, advantages, and challenges. Each method contributes uniquely to the quality and applicability of BNNTs in terms of scalability and production efficiency. This study focused on the applications of BNNTs in neutron absorption, particularly in aerospace engineering. BNNTs have shown promising potential in enhancing the safety and longevity of space missions by providing effective radiation protection. Furthermore, their potential in medical applications, particularly in Boron Neutron Capture Therapy (BNCT) for cancer treatment, has been explored. BNCT offers a targeted approach to cancer therapy by utilizing the high boron-10 content of BNNTs for precise and localized treatment. This review also provides an outlook on the future of BNNT research, emphasizing the need for more efficient growth methods to facilitate wider adoption and commercialization. The versatility of BNNTs across various fields, from space exploration to medical science, underscores their potential as materials of significant scientific and technological importance. As research progresses, BNNTs are expected to play a pivotal role in advancing materials science and offer innovative solutions to complex challenges.

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.

WSe2/BN heterostructure as saturable absorber for a diode-pumped passively Q-switched 2 µm solid-state laser

We have successfully achieved the synthesis of heterojunction consisting of WSe2 and BN, by using a liquid phase exfoliation method, and characterization of the prepared materials under the microstructure. The WSe2/BN heterojunction was used as a saturable absorber in the Tm:YAP laser for passively Q-switched operation, and a pulsed laser with an output wavelength around 2 µm range was successfully obtained. After comparing the effects of resonators composed of different cavity mirrors, it is concluded that when the curvature radius of the input mirror is 250 mm and the transmittance of the output coupler is 2.5%, the best output performance was obtained. The maximum average output power of 834 mW was achieved, with a pulsed repetition frequency of 43.51 kHz and a minimum pulse duration of 1.28 µs, corresponding to a peak power of 14.97 W and a maximum single pulse energy of 19.17 µJ.

Structural, Electronic and Vibrational Properties of B24N24 Nanocapsules: Novel Anodes for Magnesium Batteries

We report on DFT-TDDFT studies of the structural, electronic and vibrational properties of B24N24 nanocapsules and the effect of encapsulation of homonuclear diatomic halogens (Cl2, Br2 and I2) and chalcogens (S2 and Se2) on the interaction of the B24N24 nanocapsules with the divalent magnesium cation. In particular, to foretell whether these BN nanostructures could be proper negative electrodes for magnesium-ion batteries, the structural, vibrational and electronic properties, as well as the interaction energy and the cell voltage, which is important for applications, have been computed for each system, highlighting their differences and similarities. The encapsulation of halogen and chalcogen diatomic molecules increases the cell voltage, with an effect enhanced down groups 16 and 17 of the periodic table, leading to better performing anodes and fulfilling a remarkable cell voltage of 3.61 V for the iodine-encapsulated system.

Brownian Diffusion of Hexagonal Boron Nitride Nanosheets and Graphene in Two Dimensions

Two-dimensional (2D) nanomaterials have numerous interesting chemical and physical properties that make them desirable building blocks for the manufacture of macroscopic materials. Liquid-phase processing is a common method for forming macroscopic materials from these building blocks including wet-spinning and vacuum filtration. As such, assembling 2D nanomaterials into ordered functional materials requires an understanding of their solution dynamics. Yet, there are few experimental studies investigating the hydrodynamics of disk-like materials. Herein, we report the lateral diffusion of hexagonal boron nitride nanosheets (h-BN and graphene) in aqueous solution when confined in 2-dimensions. This was done by imaging fluorescent surfactant-tagged nanosheets and visualizing them by using fluorescence microscopy. Spectroscopic studies were conducted to characterize the interactions between h-BN and the fluorescent surfactant, and atomic force microscopy (AFM) was conducted to characterize the quality of the dispersion. The diffusion data under different gap sizes and viscosities displayed a good correlation with Kramers' theory. We propose that the yielded activation energies by Kramers' equation express the magnitude of the interaction between fluorescent surfactant tagged h-BN and glass because the energies remain constant with changing viscosity and decrease with increasing confinement size. The diffusion of graphene presented a similar trend with similar activation energy as the h-BN. This relationship suggests that Kramers' theory can also be applied to simulate the diffusion of other 2D nanomaterials.

Carbon doped hexagonal boron nitride as an efficient metal-free catalyst for NO capture and reduction

The electrochemical NO reduction reaction (NORR) towards NH3 is considered a promising strategy to cope with both NO removal and NH3 production. Currently, the research on NORR electrocatalysts mainly focuses on metal-based catalysts, while metal-free catalysts are quite scarce. In this work, we have systematically investigated the properties of pristine and C/O doped h-BN for efficient NO capture and reduction. Our results reveal that the basal plane of pristine h-BN is inert to the adsorption of NO, while doping C or O can significantly enhance the NO capture abilities of h-BN. Then, we highlight that C-doped h-BN exhibits excellent NORR catalytic performance with a relatively low limiting potential of -0.28 V. Further analysis shows that the suitable adsorption strength of NO on the C-doped h-BN surface is the prime reason for its excellent NO reduction activity, which is shown to be due to appropriate electronic interactions between the active site and NO. Last but not least, the catalytic selectivity of h-BN towards the NORR is confirmed by inhibiting the competing hydrogen evolution reaction. Our findings not only provide deeper insight into the essential effect of element doping on the catalytic activities of h-BN, but also propose general design principles for high-performance metal-free NORR electrocatalysts.

Advances in boron nitride-based nanomaterials for environmental remediation and water splitting: a review

Boron nitride has gained wide-spread attention globally owing to its outstanding characteristics, such as a large surface area, high thermal resistivity, great mechanical strength, low density, and corrosion resistance. This review compiles state-of-the-art synthesis techniques, including mechanical exfoliation, chemical exfoliation, chemical vapour deposition (CVD), and green synthesis for the fabrication of hexagonal boron nitride and its composites, their structural and chemical properties, and their applications in hydrogen production and environmental remediation. Additionally, the adsorptive and photocatalytic properties of boron nitride-based nanocomposites for the removal of heavy metals, dyes, and pharmaceuticals from contaminated waters are discussed. Lastly, the scope of future research, including the facile synthesis and large-scale applicability of boron nitride-based nanomaterials for wastewater treatment, is presented. This review is expected to deliver preliminary knowledge of the present state and properties of boron nitride-based nanomaterials, encouraging the future study and development of these materials for their applications in various fields.

Exfoliable Transition Metal Chalcogenide Semiconductor NbSe2I2

As the field of exfoliated van der Waals electronics grows to include complex heterostructures, the variety of available in-plane symmetries and geometries becomes increasingly valuable. In this work, we present an efficient chemical vapor transport synthesis of NbSe2I2 with the triclinic space group P1̅. This material contains Nb-Nb dimers and an in-plane crystallographic angle γ = 61.3°. We show that NbSe2I2 can be exfoliated down to few-layer and monolayer structures and use Raman spectroscopy to test the preservation of the crystal structure of exfoliated thin films. The crystal structure was verified by single-crystal and powder X-ray diffraction methods. Density functional theory calculations show triclinic NbSe2I2 to be a semiconductor with a band gap of around 1 eV, with similar band structure features for bulk and monolayer crystals. The physical properties of NbSe2I2 have been characterized by transport, thermal, optical, and magnetic measurements, demonstrating triclinic NbSe2I2 to be a diamagnetic semiconductor that does not exhibit any phase transformation below room temperature.

Unraveling the Photoluminescence Properties of a Boron Nitride Nanosheet Dispersed in Different Solvents and Its Application to Generate White Light

Hexagonal boron nitride (h-BN) is an influential 2D nanomaterial; however, its practical optoelectronic applications rely primarily on controlling the structural defects. The photoluminescence depends explicitly on the developed vacancies and substitutional defects. The present work utilizes the concept of facile liquid-phase exfoliation of hexagonal (h) boron nitride (BN) powder in common organic solvents and cosolvent mixtures to obtain a layered boron nitride nanosheet (BNNS). Although the literature concerning the layered structure of BNNS obtained by different methods is substantial, what is lacking is a detailed photoluminescence study of the layered structure obtained by changing the solvent and cosolvent mixtures, and here lies the novelty of our work. The obtained layered structure was subjected to a detailed photoluminescence study by varying the temperature. We tried to correlate how the defects originating upon changing the solvent and cosolvent affected the photoluminescence of the layered BNNS. The obtained layered structure is suitably supported by optical and electron microscopy images. High-resolution transmission electron microscopy confirm the presence of a few layers, and X-ray photoelectron spectroscopy studies give an idea of the atomic composition of the obtained BNNS. The photoluminescence properties of the obtained BNNS in water were modulated by the addition of two different classes of block copolymers, e.g., Pluronic (F-68, P-407, and P-123) and Tetronic (T-904, T-908, and T-90R4) copolymers. As an application, we were successful in constructing a nanocomposite material made up of a BNNS-copolymer-organic fluorophore to check the possibilities of generating white light.

Plasma Processing and Treatment of 2D Transition Metal Dichalcogenides: Tuning Properties and Defect Engineering

Two-dimensional transition metal dichalcogenides (TMDs) offer fascinating opportunities for fundamental nanoscale science and various technological applications. They are a promising platform for next generation optoelectronics and energy harvesting devices due to their exceptional characteristics at the nanoscale, such as tunable bandgap and strong light-matter interactions. The performance of TMD-based devices is mainly governed by the structure, composition, size, defects, and the state of their interfaces. Many properties of TMDs are influenced by the method of synthesis so numerous studies have focused on processing high-quality TMDs with controlled physicochemical properties. Plasma-based methods are cost-effective, well controllable, and scalable techniques that have recently attracted researchers' interest in the synthesis and modification of 2D TMDs. TMDs' reactivity toward plasma offers numerous opportunities to modify the surface of TMDs, including functionalization, defect engineering, doping, oxidation, phase engineering, etching, healing, morphological changes, and altering the surface energy. Here we comprehensively review all roles of plasma in the realm of TMDs. The fundamental science behind plasma processing and modification of TMDs and their applications in different fields are presented and discussed. Future perspectives and challenges are highlighted to demonstrate the prominence of TMDs and the importance of surface engineering in next-generation optoelectronic applications.

Transition metals anchored on two-dimensional p-BN support with center-coordination scaling relationship descriptor for spontaneous visible-light-driven photocatalytic nitrogen reduction

Solar energy has the potential to revolutionize the production of ammonia, as it could provide a reliable and uninterrupted source of energy for the chemical reaction involved. However, improving the catalytic performance of catalysts often leads to a reduction in their band gaps, which results in insufficient photogenerated electron potential to realize the nitrogen reduction reaction (NRR), and thus the development of NRR efficient photocatalysts remains a great challenge. Herein, based on the density functional theory (DFT), a series of single-atom photocatalysts with transition metals (TMs) doped on porous boron nitride (p-BN) nanosheet are proposed for NRR. Among them, Re-B3@p-BN could effectively catalyze gas-phase N2 through the corresponding pathways with limiting potentials of 0.31 V. Meanwhile, it exhibits excellent light absorption efficiency under illumination and could spontaneously catalyse nitrogen fixation reactions due to the suitable forbidden band and high photogenerated electron potential. Moreover, a linear relationship descriptor based on the intrinsic properties has been established, using a machine learning approach by considering the combined effects of the central metal atom and the coordination atoms. This descriptor could help accelerate the development of rational and improved 2D NRR photocatalysts with high catalytic activity and high selectivity.

Condensation-assembly synthesis of three-dimensionally porous boron nitride for effective oil removal

A template-free pyrolysis route has been developed using condensation-assembly precursors made of trimethoxyboroxane (TMB) and melamine (M) to cater the requirements of an industrial real-world environment. The precursors contain abundant B-N bonds and exhibit a high level of interconnectivity, resulting in 3D-PBN with enhanced mechanical properties and the ability to be easily customized in terms of shape. Moreover, 3D-PBN demonstrates rapid adsorption kinetics and excellent reusability, efficiently removing up to 270% of its own weight of fuel within 30 s and being readily regenerated through simple calcination. Even after undergoing 50 cycles, the mechanical properties remain at a remarkable 80%, while the adsorption performance exceed 95%. Furthermore, a comprehensive analysis of thermal behavior from precursor to 3D-PBN has been conducted, leading to the proposal of a molecular-scale evolution process comprising four major steps. This understanding enables us to control the phase reaction and regulate the composition of the products, which is crucial for determining the characteristics of the final product.

Dispersing boron nitride nanosheets with carboxymethylated cellulose nanofibrils for strong and thermally conductive nanocomposite films with improved water-resistance

BNNS (boron nitride nanosheets)-CNF (cellulose nanofibrils) nanocomposite films have attracted increasing attention for advanced thermal management applications. However, the nanocomposite films reported so far generally suffer from unsatisfactory overall performance, especially for thermal conductivity and tensile strength. In this work, a nanocomposite film with excellent overall performance was prepared by using CCNF1.2 (carboxymethylated CNF with 1.2 mmol·g-1 carboxyl content) simultaneously as effective dispersant and reinforcement matrix for BNNS. The high aspect ratio of CCNF1.2 is primarily responsible for its excellent dispersion capability for BNNS, which provides strong steric hindrance repulsion force. Meanwhile, CCNF1.2 manifests the strongest hydrophobic-hydrophobic interactions with BNNS, and its carboxyl groups completely interact with the -OH of BNNS by hydrogen bonding. As a result, the BNNS-CCNF1.2 film (50 wt% BNNS) exhibits compacted aligned structure and superior comprehensive performance (125.0 MPa tensile strength, 17.3 W·m-1·K-1 in-plane thermal conductivity, and improved water resistance). This work demonstrates the effectiveness of CCNF in improving the overall performance of BNNS-CNF films and paves the way for their practical application in the advanced thermal management of next-generation electronic devices.

In vivo investigation of boron-rich nanodrugs for treating triple-negative breast cancers via boron neutron capture therapy

Triple-negative breast cancer (TNBC) is characterized by highly proliferative cancer cells and is the only subtype of breast cancer that lacks a targeted therapy. Boron neutron capture therapy (BNCT) is an approach that combines chemotherapy with radiotherapy and can potentially offer beneficial targeted treatment for TNBC patients owing to its unique ability to eradicate cancer cells selectively while minimizing damage to the surrounding healthy cells. Since BNCT relies on specific delivery of a high loading of B10 to the tumor site, there is growing research interest to develop more potent boron-based drugs for BNCT that can overcome the limitations of small-molecule boron compounds. In this study, polyethylene-glycol-coated boron carbon oxynitride nanoparticles (PEG@BCNO) of size 134.2±23.6nm were prepared as a promising drug for BNCT owing to their high boron content and enhanced biocompatibility. The therapeutic efficiency of PEG@BCNO was compared with a state-of-the-art 10BPA boron drug in mice bearing MDA-MB-231 tumor. In the orthotopic mouse model, PEG@BCNO showed higher B10 accumulation in the tumor tissues (6 μg 10B/g tissue compared to 3 μg 10B/g tissue in mice administered B10-enriched 10BPA drug) despite using the naturally occurring 11B/10B boron precursor in the preparation of the BCNO nanoparticles. The in vivo biodistribution of PEG@BCNO in mice bearing MDA-MB-231 showed a tumor/blood ratio of ~3.5, which is comparable to that of the state-of-the-art 10BPA-fructose drug. We further demonstrated that upon neutron irradiation, the mice bearing MDA-MB-231 tumor cells treated with PEG@BCNO and 10BPA showed tumor growth delay times of 9 days and 1 day, respectively, compared to mice in the control group after BNCT. The doubling times (DTs) for mice treated with PEG@BCNO and 10BPA as well as mice in the control group were calculated to be 31.5, 19.8, and 17.7 days, respectively. Immunohistochemical staining for the p53 and caspase-3 antibodies revealed that mice treated with PEG@BCNO showed lower probability of cancer recurrence and greater level of cellular apoptosis than mice treated with 10BPA and mice in the control group. Our study thus demonstrates the potential of pegylated BCNO nanoparticles in effectively inhibiting the growth of TNBC tumors compared to the state-of-the-art boron drug 10BPA.

Coaxial Wet Spinning of Boron Nitride Nanosheet-Based Composite Fibers with Enhanced Thermal Conductivity and Mechanical Strength

Hexagonal boron nitride nanosheets (BNNSs) exhibit remarkable thermal and dielectric properties. However, their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron nitride, thereby limiting their performance in applications such as thermal management. In this study, we present a coaxial wet spinning approach for the fabrication of BNNSs/polymer composite fibers with high nanosheet orientation. The composite fibers were prepared using a superacid-based solvent system and showed a layered structure comprising an aramid core and an aramid/BNNSs sheath. Notably, the coaxial fibers exhibited significantly higher BNNSs alignment compared to uniaxial aramid/BNNSs fibers, primarily due to the additional compressive forces exerted at the core-sheath interface during the hot drawing process. With a BNNSs loading of 60 wt%, the resulting coaxial fibers showed exceptional properties, including an ultrahigh Herman orientation parameter of 0.81, thermal conductivity of 17.2 W m-1 K-1, and tensile strength of 192.5 MPa. These results surpassed those of uniaxial fibers and previously reported BNNSs composite fibers, making them highly suitable for applications such as wearable thermal management textiles. Our findings present a promising strategy for fabricating high-performance composite fibers based on BNNSs.

Multifunctional carbon nitride nanoarchitectures for catalysis

Catalysis is at the heart of modern-day chemical and pharmaceutical industries, and there is an urgent demand to develop metal-free, high surface area, and efficient catalysts in a scalable, reproducible and economic manner. Amongst the ever-expanding two-dimensional materials family, carbon nitride (CN) has emerged as the most researched material for catalytic applications due to its unique molecular structure with tunable visible range band gap, surface defects, basic sites, and nitrogen functionalities. These properties also endow it with anchoring capability with a large number of catalytically active sites and provide opportunities for doping, hybridization, sensitization, etc. To make considerable progress in the use of CN as a highly effective catalyst for various applications, it is critical to have an in-depth understanding of its synthesis, structure and surface sites. The present review provides an overview of the recent advances in synthetic approaches of CN, its physicochemical properties, and band gap engineering, with a focus on its exclusive usage in a variety of catalytic reactions, including hydrogen evolution reactions, overall water splitting, water oxidation, CO2 reduction, nitrogen reduction reactions, pollutant degradation, and organocatalysis. While the structural design and band gap engineering of catalysts are elaborated, the surface chemistry is dealt with in detail to demonstrate efficient catalytic performances. Burning challenges in catalytic design and future outlook are elucidated.

Ductile amorphous boron nitride microribbons

The broad applications of ceramic materials in functional devices are often limited by their intrinsic brittleness. Amorphous boron nitride (a-BN), as a promising ceramic has shown high thermal stability and excellent dielectric properties that can be applied to microfabricated aerogel and nano dielectric layers, while its mechanical properties at small scales are yet to be studied. Here we report synthesized a-BN microribbons can have a uniform elongation at a breaking strain of more than 50% upon tension, exhibiting outstanding ductility. Such a-BN microribbons with lengths ranging from tens to hundreds of micro-meters were prepared via the small molecule precursors sol-gel method. Through in situ uniaxial tensile measurements, we demonstrated that a-BN microribbons also display a surprising flaw-tolerance behaviour. Combining high-resolution atomic characterization with molecular dynamics simulations, we reveal that the large tensile plasticity of a-BN originates from the topological deformation induced multiple energy-dissipation mechanisms including unfolding and reorientation of local curly h-BN layers and their interlayer debonding, slippage as well as the intralayer tearing. Our findings provide new insights to develop ductile amorphous covalent-bonded materials for emerging applications.

Prospective utilization of boron nitride and beryllium oxide nanotubes for Na, Li, and K-ion batteries: a DFT-based analysis

CONTEXT

In the present work, we investigated the adsorption mechanism of natural sodium (Na), potassium (K), and lithium (Li) atoms and their respective ion on two nanostructures: boron-nitride nanotubes (BNNTs) and beryllium-oxide nanotubes (BeONTs). The main goal of this research is to calculate the gain voltage for Na, K, and Li ionic batteries. Density function theory (DFT) calculations indicated that the adsorption energy between Na + is higher than that of the other cations, and this is particularly clear in the BeONT. Furthermore, gain voltage calculations showed that BNNTs generate a higher potential than BeONTs, with the most significant difference observed in BNNT/Na + . This research provides theoretical insights into the potential uses of these nanostructures as anodes in Na, K, and Li-ion batteries.

METHOD

Density function theory used to compute the ground state properties for BeONT and BNNT with and without selected atoms and their ions (Li, K, and Na). B3LYP used for exchange correlation between electrons and ions, and 6-31G* basis set used for all atoms and ions. Gauss Sum 2.2 software used for estimate the density of state (DOS) for all structure under investigation.

Curvature induced structural changes of the chicken villin headpiece subdomain by single walled carbon nanotubes

Carbon nanotubes (CNTs) are identified as potential candidates for drug and biomolecular loading and delivery. CNTs of different chiralities have different diameters, which may significantly affect their abilities to interact with different types of biomolecules. Herein, we employ classical molecular dynamics simulation to provide insight into the curvature-dependent interactions between a model protein, chicken villin headpiece subdomain (HP36), with CNTs having chiralities (8,8), (12,12), and (20,20). It is revealed that, with increasing radii, the protein encounters more aromatic carbon atoms on the surface of the CNT, leading to its increasing strength of adsorption. However, the extent of adsorption has a limiting magnitude, after which an increase in the radius of the nanotube has practically no effect on the extent of adsorption. Spontaneous encapsulation of the protein was demonstrated using a (28,28) CNT, where the protein is found to undergo insignificant structural perturbation. Finally, steered molecular dynamics simulations have been performed to mimic the force-induced release of the protein from within the nanotube cavity. It has been identified that a minimum force of ∼300 pN and a minimum velocity of 4 Å ns-1 are required to release the protein from the CNT at 300 K. Any external force below the critical magnitude and inducing velocity less than 4 Å ns-1 allows the translocation of the protein through the inner surface of the CNT; however, before being released, the protein undergoes unfolding, thereby losing the secondary structure and biological activity.

On the CO[Formula: see text] adsorption in a boron nitride analog for the recently synthesized biphenylene network: a DFT study

CONTEXT

Recent advances in nanomaterial synthesis and characterization have led to exploring novel 2D materials. The biphenylene network (BPN) is a notable achievement in current fabrication efforts. Numerical studies have indicated the stability of its boron nitride counterpart, known as BN-BPN. In this study, we employ computational simulations to investigate the electronic and structural properties of pristine and doped BN-BPN monolayers upon CO[Formula: see text] adsorption. Our findings demonstrate that pristine BN-BPN layers exhibit moderate adsorption energies for CO[Formula: see text] molecules, approximately [Formula: see text]0.16 eV, indicating physisorption. However, introducing one-atom doping with silver, germanium, nickel, palladium, platinum, or silicon significantly enhances CO[Formula: see text] adsorption, leading to adsorption energies ranging from [Formula: see text]0.13 to [Formula: see text]0.65 eV. This enhancement indicates the presence of both physisorption and chemisorption mechanisms. BN-BPN does not show precise CO[Formula: see text] sensing and selectivity. Furthermore, our investigation of the recovery time for adsorbed CO[Formula: see text] molecules suggests that the interaction between BN-BPN and CO[Formula: see text] cannot modify the electronic properties of BN-BPN before the CO[Formula: see text] molecules escape.

METHODS

We performed density functional theory (DFT) simulations using the DMol3 code in the Biovia Materials Studio software. We incorporated Van der Waals corrections (DFT-D) within the Grimme scheme for an accurate representation. The exchange and correlation functions were treated using the Perdew-Burke-Ernzerhof (PBE) functional within the generalized gradient approximation (GGA). We used a double-zeta plus polarization (DZP) basis set to describe the electronic structure. Additionally, we accounted for the basis set superposition error (BSSE) through the counterpoise method. We included semicore DFT pseudopotentials to accurately model the interactions between the nuclei and valence electrons.

Tuning the electron-phonon interaction via exploring the interrelation between Urbach energy and fano-type asymmetric raman line shape in GO-hBN nanocomposites

Hexagonal boron nitride (hBN), having an in-plane hexagonal structure in the sp2arrangement of atoms, proclaims structural similarity with graphene with only a small lattice mismatch. Despite having nearly identical atomic arrangements and exhibiting almost identical properties, the electronic structures of the two materials are fundamentally different. Considering the aforementioned condition, a new hybrid material with enhanced properties can be evolved by combining both materials. This experiment involves liquid phase exfoliation of hBN and two-dimensional nanocomposites of GO-hBN with varying hBN and graphene oxide (GO) ratios. The optical and vibrational studies conducted using UV-vis absorption and Raman spectroscopic analysis report the tuning of electron-phonon interaction (EPI) in the GO-hBN nanocomposite as a function of GO content (%). This interaction depends on disorder-induced electronic and vibrational modifications addressed by Urbach energy (Eu) and asymmetry parameter (q), respectively. The EPI contribution to the induced disorders estimated from UV-vis absorption spectra is represented as EPI strength (Ee-p) and its impact observed in Raman phonon modes is quantified as an asymmetry parameter (q). The inverse of the asymmetry parameter is related toEe-p, asEe-p∼ 1/|q|. Here in this article, a linear relationship has been established betweenEuand the proportional parameter (k), wherekis determined as the ratio of the intensity of specific Raman mode (I) andq2, explaining the disorders' effect on Raman line shape. Thus a correlation between Urbach energy and the asymmetry parameter of Raman mode confirms the tuning of EPI with GO content (%) in GO-hBN nanocomposite.

Electrochemical nitrogen fixation on single metal atom catalysts

The electrochemical reduction of nitrogen (eNRR) offers a promising alternative to the Haber-Bosch (H-B) process for producing ammonia under moderate conditions. However, the inertness of dinitrogen and the competing hydrogen evolution reaction pose significant challenges for eNRR. Thus, developing more efficient electrocatalysts requires a deeper understanding of the underlying mechanistic reactions and electrocatalytic activity. Single atom catalysts, which offer tunable catalytic properties and increased selectivity, have emerged as a promising avenue for eNRR. Carbon and metal-based substrates have proven effective for dispersing highly active single atoms that can enhance eNRR activity. In this review, we explore the use of atomically dispersed single atoms on different substrates for eNRR from both conceptual and experimental perspectives. The review is divided into four sections: the first section describes eNRR mechanistic pathways, the second section focuses on single metal atom catalysts (SMACs) with metal atoms dispersed on carbon substrates for eNRR, the third section covers SMACs with metal atoms dispersed on non-carbon substrates for eNRR, and the final section summarizes the remaining challenges and future scope of eNRR for green ammonia production.

Tumor Eradication by Boron Neutron Capture Therapy with 10 B-enriched Hexagonal Boron Nitride Nanoparticles Grafted with Poly(Glycerol)

Boron neutron capture therapy (BNCT) has emerged as a treatment modality with high precision and efficacy of intractable tumors. At the core of effective tumor BNCT are 10 B carriers with facile preparation as well as advantageous pharmacokinetic and therapeutic profiles. Herein, the design and preparation of sub-10 nm 10 B-enriched hexagonal boron nitride nanoparticles grafted with poly(glycerol) (h-10 BN-PG), and their application to cancer treatment by BNCT are reported. By virtue of their small particle size and outstanding stealth property, h-10 BN-PG nanoparticles accumulate efficiently in murine CT26 colon tumors with a high intratumor 10 B concentration of 8.8%ID g-1 or 102.1 µg g-1 at 12 h post-injection. Moreover, h-10 BN-PG nanoparticles penetrate into the inside of the tumor parenchyma and then are taken up by the tumor cells. BNCT comprising a single bolus injection of h-10 BN-PG nanoparticles and subsequent one-time neutron irradiation results in significant shrinkage of subcutaneous CT26 tumors. h-10 BN-PG-mediated BNCT not only causes direct DNA damage to the tumor cells, but also triggers pronounced inflammatory immune response in the tumor tissues, which contributes to long-lasting tumor suppression after the neutron irradiation. Thus, the h-10 BN-PG nanoparticles are promising BNCT agents to eradicate tumor through highly efficient 10 B accumulation.

Growth mechanisms of monolayer hexagonal boron nitride (h-BN) on metal surfaces: theoretical perspectives

Two-dimensional hexagonal boron nitride (h-BN) has appeared as a promising material in diverse areas of applications, including as an excellent substrate for graphene devices, deep-ultraviolet emitters, and tunneling barriers, thanks to its outstanding stability, flat surface, and wide-bandgap. However, for achieving such exciting applications, controllable mass synthesis of high-quality and large-scale h-BN is a precondition. The synthesis of h-BN on metal surfaces using chemical vapor deposition (CVD) has been extensively studied, aiming to obtain large-scale and high-quality materials. The atomic-scale growth process, which is a prerequisite for rationally optimizing growth circumstances, is a key topic in these investigations. Although theoretical investigations on h-BN growth mechanisms are expected to reveal numerous new insights and understandings, different growth methods have completely dissimilar mechanisms, making theoretical research extremely challenging. In this article, we have summarized the recent cutting-edge theoretical research on the growth mechanisms of h-BN on different metal substrates. On the frequently utilized Cu substrate, h-BN development was shown to be more challenging than a simple adsorption-dehydrogenation-growth scenario. Controlling the number of surface layers is also an important challenge. Growth on the Ni surface is controlled by precipitation. An unusual reaction-limited aggregation growth behavior has been seen on interfaces having a significant lattice mismatch to h-BN. With intensive theoretical investigations employing advanced simulation approaches, further progress in understanding h-BN growth processes is predicted, paving the way for guided growth protocol design.

A comprehensive review on monitoring and purification of water through tunable 2D nanomaterials

Instead of typical household trash, the heavy metal complexes, organic chemicals, and other poisons produced by huge enterprises threaten water systems across the world. In order to protect our drinking water from pollution, we must keep a close eye on the situation. Nanotechnology, specifically two-dimensional (2D) nanomaterials, is used in certain wastewater treatment systems. Graphene, g-C3N4, MoS2, and MXene are just a few examples of emerging 2D nanomaterials that exhibit an extraordinary ratio of surface (m3), providing material consumption, time consumption, and treatment technique for cleaning and observing water. In this post, we'll talk about the ways in which 2D nanomaterials may be tuned to perform certain functions, namely how they can be used for water management. The following is a quick overview of nanostructured materials and its possible use in water management: Also discussed in length are the applications of 2D nanomaterials in water purification, including pollutant adsorption, filtration, disinfection, and photocatalysis. Fluorescence sensors, colorimetric, electrochemical, and field-effect transistors are only some of the devices being studied for their potential use in monitoring water quality using 2D nanomaterials. Utilizing 2D content has its benefits and pitfalls when used to water management. New developments in this fast-expanding business will boost water treatment quality and accessibility in response to rising awareness of the need of clean, fresh water among future generations.

Boron Nitride Nanosheets Functionalized with Fe3O4 and CoFe2O4 Magnetic Nanoparticles for Nanofiltration Applications

Nanofiltration (NF) is one of the emerging technologies that is very promising for water purification among many other applications. 2D boron nitride (BN) based nanomaterials are excellent building blocks for NF membranes. In our work, BN nanosheets (BNNS) have been functionalized with magnetic nanoparticles (MNPs) to form BNNS-MNP nanocomposites. It was found that the nanocomposites are stable with the MNPs giving very good coverage with both magnetite and cobalt ferrite MNPs and showing good attachment and stability to sonication. These nanocomposites have been tested for removal of methylene blue (MB) dye and MNPs from water. BNNS-magnetite nanocomposites showed higher removal efficiency of the MB from water than the corresponding pure BNNS, while the BNNS-cobalt ferrite removal efficiency was slightly less than the pure BNNS. The BNNS-cobalt ferrite material was regenerated by burning off the MB and recycled to show the recyclability of this material. The BNNS membranes were tested for filtration of 14 ± 4 nm magnetite MNPs and were found to capture 100% of the nanoparticles with no MNPs left in the filtrate. Thus, we have developed magnetic nanocomposite membranes, which have demonstrated great potential for water remediation. We believe that this research opens up promising ways for production of 2D nanocomposite materials with multiple applications.

The Structure of Boron Monoxide

Boron monoxide (BO), prepared by the thermal condensation of tetrahydroxydiboron, was first reported in 1955; however, its structure could not be determined. With the recent attention on boron-based two-dimensional materials, such as borophene and hexagonal boron nitride, there is renewed interest in BO. A large number of stable BO structures have been computationally identified, but none are supported by experiments. The consensus is that the material likely forms a boroxine-based two-dimensional material. Herein, we apply advanced 11B NMR experiments to determine the relative orientations of B(B)O2 centers in BO. We find that the material is composed of D2h-symmetric O2B-BO2 units that organize to form larger B4O2 rings. Further, powder diffraction experiments additionally reveal that these units organize to form two-dimensional layers with a random stacking pattern. This observation is in agreement with earlier density functional theory (DFT) studies that showed B4O2-based structures to be the most stable.

Direct Synthesis of Vertical Self-Assembly Oriented Hexagonal Boron Nitride on Gallium Nitride and Ultrahigh Photoresponse Ultraviolet Photodetectors

The applications of three-dimensional materials combined with two-dimensional materials are attractive for constructing high-performance electronic and photoelectronic devices because of their remarkable electronic and optical properties. However, traditional preparation methods usually involve mechanical transfer, which has a complicated process and cannot avoid contamination. In this work, chemical vapor deposition was proposed to vertically synthesize self-assembly oriented hexagonal boron nitride on gallium nitride directly. The material composition, crystalline quality and orientation were investigated using multiple characterization methods. Thermal conductivity was found to be enhanced twofold in the h-BN incorporated sample by using the optothermal Raman technique. A vertical-ordered (VO)h-BN/GaN heterojunction photodetector was produced based on the synthesis. The photodetector exhibited a high ultraviolet photoresponsivity of up to 1970.7 mA/W, and detectivity up to 2.6 × 10¹³ Jones, and was stable in harsh high temperature conditions. Our work provides a new synthesis method to prepare h-BN on GaN-based materials directly, and a novel vertically oriented structure of VO-h-BN/GaN heterojunction, which has great application potential in optoelectronic devices.

The Influence of the Size of BN NSs on Silkworm Development and Tissue Microstructure

Boron nitride nanosheets (BN NSs) have emerged as promising materials in a wide range of biomedical applications. Despite the extensive studies on these bio-nano interfacial systems, one critical concern is their toxicity, which is affected by a variety of factors, including size. This study aimed at assessing the relationship between BN NSs size and toxicity. Two silkworm strains (qiufeng × baiyu and Nistari 7019) were used as model organisms to investigate the effect of different sizes of BN NSs (BN NSs-1, thickness of 41.5 nm and diameter of 270.7 nm; BN NSs-2, thickness of 48.2 nm and diameter of 562.2 nm) on silkworm mortality, growth, cocoon weight, and tissue microstructure. The findings show that exposure to BN NSs in this work has no lethal adverse effects on silkworm growth or tissue microstructure. BN NSs have a higher effect on the growth rate of qiufeng × baiyu compared to Nistari 7019, demonstrating that the same treatment does not favorably affect the Nistari 7019 strain, as there is no significant increase in cocoon weight. Overall, the study suggests that the sizes of BN NSs employed in this study are relatively safe and have less negative impact on silkworms. This offers significant insights into the effect of BN NSs size, a crucial factor to consider for their safe use in biomedical applications.