Search Results (72)

Hexagonal boron nitride (h-BN) and boron nitride nanotubes (BNNTs) are emerging advanced nanomaterials with analogous structures to graphene and carbon nanotubes, respectively. However, little is known about what effect replacing carbon atoms with boron and nitrogen will have on the materials’ safety profile. This study’s aim was to first identify if multi-walled nanotubes of BN could produce a hazard profile similar to that evidenced already for multi-walled carbon nanotubes (MWCNTs) and secondly if the material when present in a sheet-like structure increases or decreases the hazard profile. Fish are aquatic organisms sensitive to boron compounds; however, the potential hazard following exposure to BN and especially when present in such nanostructures has not yet been investigated. An in vitro testing platform consisting of multiple cell lines of the rainbow trout, Oncorhynchus mykiss (RTH-149, RTG-2, RTL-W1 and RTgill-W1), was used in a first-hazard screening approach for cytotoxicity and to gain information on material–cellular interaction. Clear differences were evidenced in material uptake, leading to plasma membrane disruption accompanied with a loss in metabolic activity for BNNTs at lower exposure concentrations compared to h-BN. As in the case of carbon nanotubes, close attention must be given to potential interferences with assays based on optical readouts. Full article

Comparing electroanalysis and chromatography, this study highlights that electroanalysis, specifically using a glassy carbon sensor (GCS), is the most appropriate choice for quantifying recalcitrant organic compounds. Octocrylene (OC), an organic compound commonly found in sunscreens, is of particular concern in swimming pool water monitoring, as its presence above legal limits poses health risks. OC quantification was performed using both high performance liquid chromatography (HPLC) and electroanalysis in sunscreen formulations and water matrices. The limits of detection (LODs) and quantification (LOQ) for OC were approximately 0.11 ± 0.01 mg L⁻¹ and 0.86 ± 0.04 mg L⁻¹ by electroanalysis, and 0.35 ± 0.02 mg L⁻¹ and 2.86 ± 0.12 mg L⁻¹ by HPLC. Electroanalysis successfully quantified OC in real sunscreen samples, and the results were comparable to those obtained by HPLC. The matrices tested—swimming pool water and distilled water (containing 0.002 M Cl⁻) contaminated with 0.4 ± 0.2 g L⁻¹ of sunscreen (based on a maximum concentration in sunscreen and cosmetic formulations of 10%)—showed OC concentrations below 10% in the formulation, with no significant differences observed between the two techniques. GCS was further utilized to monitor OC degradation via anodic oxidation at current densities of 5 and 10 mA cm⁻², using a boron-doped diamond (BDD) anode. The combined approach demonstrated high efficacy in both detecting and eliminating OC from various water matrices, making it a reliable and efficient alternative for environmental and water quality monitoring. Full article

Nanotubes (NTs) are nanosized tube-like structured materials made from various substances such as carbon, boron, or silicon. Carbon nanomaterials (CNMs), including carbon nanotubes (CNTs), graphene/graphene oxide (G/GO), and fullerenes, have good interatomic interactions and possess special characteristics, exploitable in several applications because of the presence of sp2 and sp3 bonds. Among NTs, CNTs are the most studied compounds due to their nonpareil electrical, mechanical, optical, and biomedical properties. Moreover, single-walled carbon nanotubes (SWNTs) have, in particular, demonstrated high ability as drug delivery systems and in transporting a wide range of chemicals across membranes and into living cells. Therefore, SWNTs, more than other NT structures, have generated interest in medicinal applications, such as target delivery, improved imaging, tissue regeneration, medication, and gene delivery, which provide nanosized devices with higher efficacy and fewer side effects. SWNTs and multi-walled CNTs (MWCNTs) have recently gained a great deal of attention for their antibacterial effects. Unfortunately, numerous recent studies have revealed unanticipated toxicities caused by CNTs. However, contradictory opinions exist regarding these findings. Moreover, the problem of controlling CNT-based products has become particularly evident, especially in relation to their large-scale production and the nanosized forms of the carbon that constitute them. Important directive rules have been approved over the years, but further research and regulatory measures should be introduced for a safer production and utilization of CNTs. Against this background, and after an overview of CNMs and CNTs, the antimicrobial properties of pristine and modified SWNTs and MWCNTs as well as the most relevant in vitro and in vivo studies on their possible toxicity, have been reported. Strategies and preventive behaviour to limit CNT risks have been provided. Finally, a debate on regulatory issues has also been included. Full article

Boron Neutron Capture Therapy (BNCT) is a therapeutic approach used to treat malignancies that are difficult to localise and typically inoperable. This therapy involves two stages: the administration of the boron (¹⁰B) isotope, which selectively enters cancer cells without affecting healthy tissue, followed by irradiation of the tumour with a neutron beam. In this study, boron carbide (B₄C), a ceramic material with exceptional physical and chemical properties, was used as a nanoparticle platform for BNCT. The surface of the boron carbide nanoparticles was optimised by modifying them with compounds such as dextrin, dextran T70, sorbitol, lysine, and arginine. Boron carbide was synthesised directly from boron and carbon and then subjected to grinding, washing, and centrifugation. The unmodified and modified samples were analysed for their particle size, zeta potential, and toxicity against glioblastoma T98G cells. Additionally, FTIR spectroscopy confirmed the successful surface modifications. The results demonstrate that boron carbide, as a ceramic material, can be effectively functionalised with biocompatible compounds. Among the tested modifications, B₄C-dextrin and B₄C-dextran T70 exhibited the highest toxicity towards cancer cells, demonstrating the potential of ceramic platforms in biomedical applications. Full article

Boron-doped diamond electrodes (BDDEs) offer a highly efficient pathway to mineralize recalcitrant compounds due to their reduced energy requirements, fewer chemical inputs, and mechanical stability. In this work, the electrochemical degradation of paraquat (PQ) and diquat (DQ) was studied using an undivided cell (Condiacell^®-type) at circumneutral pH, and under galvanostatic control. The roles of applied current density, volumetric flow rate, and herbicide concentration were systematically studied through a central composite design (CCD) using a closed-flow reaction setup. Under the best operating conditions (i.e., for PQ: 1.6 mA/cm², 80 mL/min, and 70 mL/min, and 70 mg/L; and for DQ: 1.5 mA/cm², 80 mL/min, and 73 mg/L), a spectrophotometric analysis evidenced that the herbicides were satisfactorily removed (ca. 100%) while mineralization degrees were above 90%. Furthermore, the produced effluents yielded significant increases in seed germination and root length, which suggest a reduction in toxicity. Energy consumptions of 0.13 and 0.18 kWh/g of TOC are reported with the electrochemical cells for the PQ and DQ treatments, respectively. The PQ and DQ treatments by electrooxidation are estimated to emit nearly 2.7 and 38.9 kg CO₂/m³ of water treated, with a cost around USD 250/m³. Carbon emissions could be greatly decreased for PQ (0.28 kg CO₂/m³) and DQ (0.40 kg CO₂/m³) if electricity were generated from renewable resources. Although this study suggests that the use of BDDE can be considered as a green alternative for agrochemical removal due to lower carbon emissions, the environmental profile of the process is determined by the degree of renewability of the electrical grid of each country or region. Full article

Fused deposition modeling (FDM) 3D printing has the advantages of a simple molding principle, convenient operation, and low cost, making it suitable for the production and fabrication of complex structural parts. Moving forward to mass production using 3D printing, the major hurdle to overcome is the achievement of high dimensional stability and adequate mechanical properties. In particular, engineering plastics require precise dimensional accuracy. In this study, we overcame the issues of FDM 3D printing in terms of ternary material compounds for polyamides with gradient structures. Using multi-walled carbon nanotubes (MWCNTs) and boron nitride (BN) as fillers, polyamide 6 (PA6)-based 3D-printed parts with high dimensional stability were prepared using a single-nozzle, two-component composite fused deposition modeling (FDM) 3D printing technology to construct a gradient structure. The ternary composites were characterized via DSC and XRD to determine the optimal crystallinity. The warpage and shrinkage of the printed samples were measured to ensure the dimensional properties. The mechanical properties were analyzed to determine the influence of the gradient structures on the composites. The experimental results show that the warpage of pure polymer 3D-printed parts is as high as 72.64%, and the introduction of a gradient structure can reduce the warpage to 3.40% by offsetting the shrinkage internal stress between layers. In addition, the tensile strength of the gradient material reaches up to 42.91 MPa, and the increasing filler content improves the interlayer bonding of the composites, with the bending strength reaching up to 60.91 MPa and the interlayer shear strength reaching up to 10.23 MPa. Therefore, gradient structure design can be used to produce PA6 3D-printed composites with high dimensional stability without sacrificing the mechanical properties of PA6 composites. Full article

Despite urgent calls for decarbonization, the continued increasing demand for electricity, primarily from coals, has presented challenges in managing coal-derived wastes such as coal fly ash (CFA), which are enriched with environmentally hazardous substances like boron. This study explores a low-temperature heating process to remove boron from coal, aimed at preventing its condensation and enrichment into CFA during combustion. Initial boron concentrations in coals varied widely from 50 to 500 ppm by weight and were found to correlate with fixed carbon content (FC) through the following polynomial equation: [B]_o = 0.0929(FC)² − 14.388(FC) + 601.85; R² = 0.9173. This relationship suggests that as coal undergoes coalification, boron-containing compounds are decomposed and released, resulting in a decline in boron levels as the coal matures. Boron-removal efficiency was investigated by drying coal samples at 110 °C, 160 °C, and 210 °C under natural air convection, and nuclear magnetic resonance (NMR) spectroscopy was used to assess changes in boron speciation during heating. Our results demonstrate that boron removal ranged from 5% to 82%, with minimal improvements observed beyond 110 °C. In addition, the ¹¹B MAS-NMR spectra of the coal samples showed four peaks at isotropic chemical shift values of −1.0, 2.0, 8.0, and 14.0 ppm and suggested that the species of boron volatilized at low temperatures is the inorganic BO₄ assigned to peak no. 0 at −1.0 ppm. The association of boron with inorganic components in coal suggests potential for efficient removal, particularly in coals with higher fixed carbon content. These findings highlight the viability of low-temperature thermal treatment as a cost-effective method for boron removal, which is crucial in mitigating the risks associated with coal combustion by-products. Full article

Boronic acids form diester bonds with cis-hydroxyl groups in carbohydrates. The formation of these adducts could impair the physical and chemical properties of precursors, even their biological activity. Two carbohydrate derivatives from d-fructose and d-arabinose and phenylboronic acid were synthesized in a straightforward one-step procedure and chemically characterized via spectroscopy and X-ray diffraction crystallography. Additionally, an acute toxicity test was performed to determine their lethal dose 50 (LD₅₀) values by using Lorke’s method. Analytical chemistry assays confirmed the formation of adducts by the generation of diester bonds with the β-d-pyranose of carbohydrates, including signals corresponding to the formation of new bonds, such as the stretching of B–O bonds. NMR spectra yielded information about the stereoselectivity in the synthesis reaction: Just one signal was found in the range for the anomeric carbon in the ¹³C NMR spectra of both adducts. The acute toxicity tests showed that the LD₅₀ value for both compounds was 1265 mg/kg, while the effective dose 50 (ED₅₀) for sedation was 531 mg/kg. However, differences were found in the onset and lapse of sedation. For example, the arabinose derivative induced sedation for more than 48 h at 600 mg/kg, while the fructose derivative induced sedation for less than 6 h at the same dose without the death of the mice. Thus, we report for the first time two boron-containing carbohydrate derivatives inducing sedation after intraperitoneal administration. They are bioactive and highly safe agents. Further biological evaluation is desirable to explore their medical applications. Full article

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. Full article

In this research, we developed boron-rich nanoparticles that can be used for boron neutron capture therapy as potential carriers for boron delivery to cancerous tissues. Functionalized carbonated boron nitride nanostructures (CBNs) were successfully synthesized in self-propagating combustion waves in mixtures of high-nitrogen explosives and boron compounds. The products’ composition, morphology, and structural features were investigated using Fourier transform infrared spectroscopy, powder X-ray diffraction, low-temperature nitrogen sorption analysis, thermogravimetric analysis, high-resolution scanning electron microscopy, and high-resolution transmission electron microscopy. The extreme conditions prevailing in combustion waves favor the formation of nanosized CBN hollow grains with highly disordered structures that are properly functionalized on the surface and inside the particles. Therefore, they are characterized by high porosity and good dispersibility in water, which are necessary for medical applications. During biological tests, a concentration-dependent effect of the obtained boron nitride preparations on the viability of normal and neoplastic cells was demonstrated. Moreover, the assessment of the degree of binding of fluorescently labeled nanoparticles to selected cells confirmed the relationships between the cell types and the concentration of the preparation at different incubation time points. Full article

Boronate esters are a class of compounds containing a boron atom bonded to two oxygen atoms in an ester group, often being used as precursors in the synthesis of other materials. The characterization of the structure and properties of esters is usually carried out by UV-visible, infrared, and nuclear magnetic resonance (NMR) spectroscopic techniques. With the aim to better understand our experimental data, in this article, the density functional theory (DFT) is used to analyze the UV-visible and infrared spectra, as well as the isotropic shielding and chemical shifts of the hydrogen atoms ¹H, carbon ¹³C and boron ¹¹B in the compound 4-(4,4,5,5-tetramethyl-1,3,2-dioxoborolan-2-yl)benzaldehyde. Furthermore, this study considers the change in its electronic and spectroscopic properties of this particular ester, when its boron atom is coordinated with a fluoride anion. The calculations were carried out using the LSDA and B3LYP functionals in Gaussian-16, and PBE in CASTEP. The results show that the B3LYP functional gives the best approximation to the experimental data. The formation of a coordinated covalent B–F bond highlights the remarkable sensitivity of the NMR chemical shifts of carbon, oxygen, and boron atoms and their surroundings. Furthermore, this bond also highlights the changes in the electron transitions bands n → π* and π → π* during the absorption and emission of a photon in the UV-vis, and in the stretching bands of the C=C bonds, and bending of BO₂ in the infrared spectrum. This study not only contributes to the understanding of the properties of boronate esters but also provides important information on the interactions and responses optoelectronic of the compound when is bonded to a fluorine atom. Full article

Sewage sludge should primarily find use in agriculture, reducing the quantity directed towards alternative disposal methods like incineration or deposition in municipal landfills. This study evaluated the agronomic value and the risk of soil and plant tissue contamination with heavy metals in sewage sludge obtained from two wastewater treatment plants (WWTP). The experiment was arranged as a 2 × 5 factorial (two sewage sludges, five sanitation treatments), involving lettuce cultivation in pots over two growing cycles. The two sewage sludges were sourced from the WWTPs of Gelfa and Viana do Castelo and underwent five sanitation and stabilization treatments (40% and 20% calcium oxide, 40% and 20% calcium hydroxide, and untreated sewage sludge). The Gelfa sewage sludge, characterized by a higher initial nitrogen (N) concentration, resulted in greater dry-matter yield (DMY) (12.4 and 8.6 g plant⁻¹ for the first and second growing cycles, respectively) compared to that from Viana do Castelo (11.0 and 8.1 g plant⁻¹), with N release likely being a major factor influencing crop productivity. The high N concentration and the low carbon (C)/N ratio of sewage sludge led to rapid mineralization of the organic substrate, which additionally led to a higher release of other important nutrients, such as phosphorus (P) and boron (B), making them available for plant uptake. Alkalizing treatments further stimulated sewage sludge mineralization, increasing soil pH and exchangeable calcium (Ca), thereby enhancing Ca availability for plants, and indicating a preference for use in acidic soils. Cationic micronutrients were minimally affected by the sewage sludge and their treatments. The concentrations of heavy metals in the sewage sludge, soils, and lettuce tissues were all below internationally established threshold limits. This study highlighted the high fertilizing value of these sewage sludges, supplying N, P, and B to plants, while demonstrating a low risk of environmental contamination with heavy metals. Nevertheless, the safe use of sewage sludge by farmers depends on monitoring other risks, such as toxic organic compounds, which were not evaluated in this study. Full article

Mesophase pitch is usually prepared by radical polymerization or catalytic polymerization from coal tar, petroleum, and aromatic compounds, and the catalytic synthesis of mesophase pitch from pure aromatic compounds is more controllable in the preparation of high-quality mesophase pitch. However, the corrosive and highly toxic nature of the catalyst has limited the further development of this method. In this study, mesophase pitch was synthetized using ethylene tar and naphthalene as raw materials and boron trifluoride diethyl etherate as a catalyst. The effect of the catalytic reaction on the structure and properties of the mesophase pitch was investigated. The results show that naphthalene plays an important role in the mesophase content and reaction pressure (from above 6 MPa to 2.35 MPa). Mesophase pitch with fine-flow texture can be prepared by introducing more methylene groups, naphthenic structures, and aliphatic hydrocarbons during synthesis. Carbon fibers prepared from mesophase pitch show a split structure, and the thermal conductivity is 730 W/(m·K). This work provides theoretical support for lower toxicity and causticity and for reaction-controlled technology for the synthesis of high-purity mesophase pitch. Full article

Benzene is the typical volatile organic compound (VOC) of indoor and outdoor air pollution, which harms human health and the environment. Due to the stability of their aromatic structure, the catalytic oxidation of benzene rings in an environment without an external energy input is difficult. In this study, the efficient degradation of benzene at room temperature was achieved by constructing Ag and Ni bimetallic active site catalysts (AgNi/BCN) supported on boron–carbon–nitrogen aerogel. The atomic-scale Ag and Ni are uniformly dispersed on the catalyst surface and form Ag/Ni-C/N bonds with C and N, which were conducive to the catalytic oxidation of benzene at room temperature. Further catalytic reaction mechanisms indicate that benzene reacted with ·OH to produce R·, which reacted with O₂ to regenerate ·OH. Under the strong oxidation of ·OH, benzene was oxidized to form alcohols, carboxylic acids, and eventually CO₂ and H₂O. This study not only significantly reduces the energy consumption of VOC catalytic oxidation, but also improves the safety of VOC treatment, providing new ideas for the low energy consumption and green development of VOC treatment. Full article

Boron carbide (B₄C) powders with defined stoichiometry, high crystallinity, minimal impurity content, and a fine particle size are imperative for realizing the exceptional properties of this compound in advanced high-technology applications. Nevertheless, achieving the desired stoichiometry and particle size using traditional synthesis methods, which rely on prolonged high-temperature processes, can be challenging. The primary objective of this study is to synthesize fine B₄C powders characterized by high crystallinity and a sub-micron particle size, employing a fast and energy-efficient method. B₄C powders are synthesized from elemental boron and carbon in a high-frequency induction heating furnace using the electromagnetic induction synthesis (EMIS) method. The rapid heating rate achieved through contactless heating promotes the ignition and propagation of the exothermic chemical reaction between boron and carbon. Additionally, electromagnetic effects accelerate atomic diffusion, allowing the reaction to be completed in an exceptionally short timeframe. The grain size and crystallinity of B₄C can be finely tuned by adjusting various process parameters, including the post-ignition holding temperature and the duration of heating. As a result, fine B₄C powders can be synthesized in under 10 min. Moreover, these synthesized B₄C powders exhibit oxidation onset temperatures higher than 500 °C when exposed to air. Full article