Superhydrophobic hBN-Regulated Sponges with Excellent Absorbency Fabricated Using a Green and Facile Method

Hexagonal Boron Nitride as a Two-Dimensional Surfactant: Low-Density Flame-Resistant Composites Based on Boron Nitride Exfoliated by an Interface Trapping Technique

Hexagonal boron nitride (hBN) is a two-dimensional material isoelectric to graphene. It has a hexagonal structure with alternating boron and nitrogen atoms and is electrically insulating, thermally conductive, and chemically inert. However, like graphene, its use as a functional nanofiller requires exfoliation. Here, we present a method for exfoliating and dispersing hexagonal boron nitride (hBN) sheets within a polymer matrix. This is achieved by a solvent interface trapping method (SITM), where hBN exfoliates and spreads at a high-energy oil/water interface, separating the two phases and lowering the system's free energy. hBN thus acts as a surfactant, allowing us to form stable water-in-oil emulsions stabilized by films of overlapping hBN sheets. Polymerizing the continuous oil phase results in polymerized high internal phase emulsions (polyHIPE), with the foam cells lined with hBN. In the investigation presented here, we use acoustic spectroscopy, optical and electron microscopy, and image analysis to study the emulsion and polyHIPE formation mechanisms. We find that the amount of hBN used, the flake size of the hBN, the mixing time, the type of initiator used, and the oil-to-water ratio all play a role in the morphology of the final polyHIPE. Lastly, we demonstrate the flame-retardant properties of the hBN polyHIPEs and show that, at 1% loadings, the presence of hBN prevents dripping and relighting of the composites, even when the material is heated to a red glow.

Antifungal Hybrid Graphene-Transition-Metal Dichalcogenides Aerogels with an Ionic Liquid Additive as Innovative Absorbers for Preventive Conservation of Cultural Heritage

The use and integration of novel materials are increasingly becoming vital tools in the field of preventive conservation of cultural heritage. Chemical factors, such as volatile organic compounds (VOCs), but also environmental factors such as high relative humidity, can lead to degradation, oxidation, yellowing, and fading of the works of art. To prevent these phenomena, highly porous materials have been developed for the absorption of VOCs and for controlling the relative humidity. In this work, graphene and transition-metal dichalcogenides (TMDs) were combined to create three-dimensional aerogels that absorb certain harmful substances. More specifically, the addition of the TMDs molybdenum disulfide and tungsten disulfide in such macrostructures led to the selective absorption of ammonia. Moreover, the addition of the ionic liquid 1-hexadecyl-3-methylimidazolium chloride promoted higher rates of VOCs absorption and anti-fungal activity against the fungus Aspergillus niger. These two-dimensional materials outperform benchmark porous absorbers in the absorption of all the examined VOCs, such as ammonia, formic acid, acetic acid, formaldehyde, and acetaldehyde. Consequently, they can be used by museums, galleries, or even storage places for the perpetual protection of works of art.

Understanding the Intrinsic Water Wettability of Hexagonal Boron Nitride

The water wettability of hexagonal boron nitride (hBN) has attracted a lot of research interest in the past 15 years. Experimentally, the static water contact angle (WCA) has been widely utilized to characterize the intrinsic water wettability of hBN. In the current study, we have investigated the effect of airborne hydrocarbons and defects on both static and dynamic WCAs of hBN. Our results showed that the static WCA is impacted by defects, which suggests that previously reported static WCAs do not characterize the intrinsic water wettability of hBN since the state-of-the-art hBN samples always have relatively high defect density. Instead, we found that the advancing WCA of freshly exfoliated hBN is not affected by the defects and airborne hydrocarbons. As a result, the advancing WCA on freshly exfoliated hBN, determined to be 79 ± 3°, best represents the intrinsic water wettability of hBN. A qualitative model has been proposed to describe the effect of airborne hydrocarbons and defects on the static and dynamic WCA of hBN, which is well supported by the experimental results. The finding here has important implications for the water wettability of 2D materials.

Multi-functional 2D hybrid aerogels for gas absorption applications

Aerogels have attracted significant attention recently due to their ultra-light weight porous structure, mechanical robustness, high electrical conductivity, facile scalability and their use as gas and oil absorbers. Herein, we examine the multi-functional properties of hybrid aerogels consisting of reduced graphene oxide (rGO) integrated with hexagonal boron nitride (hBN) platelets. Using a freeze-drying approach, hybrid aerogels are fabricated by simple mixing with various volume fractions of hBN and rGO up to 0.5/0.5 ratio. The fabrication method is simple, cost effective, scalable and can be extended to other 2D materials combinations. The hybrid rGO/hBN aerogels (HAs) are mechanically robust and highly compressible with mechanical properties similar to those of the pure rGO aerogel. We show that the presence of hBN in the HAs enhances the gas absorption capacities of formaldehyde and water vapour up to ~ 7 and > 8 times, respectively, as compared to pure rGO aerogel. Moreover, the samples show good recoverability, making them highly efficient materials for gas absorption applications and for the protection of artefacts such as paintings in storage facilities. Finally, even in the presence of large quantity of insulating hBN, the HAs are electrically conductive, extending the potential application spectrum of the proposed hybrids to the field of electro-thermal actuators. The work proposed here paves the way for the design and production of novel 2D materials combinations with tailored multi-functionalities suited for a large variety of modern applications.

Novel Superhydrophobic Sand and Polyurethane Sponge Coated with Silica/Modified Asphaltene Nanoparticles for Rapid Oil Spill Cleanup

Superhydrophobic nanomaterials are promising in the important pursuit to alleviate the environmental pollution caused by the petroleum crude oil industry, especially to clean-up oil spills. In this work, asphaltenes isolated from crude oil were modified to act as capping agents during the synthesis of hydrophobic silica nanoparticles (HSNPs). The chemical structure, surface morphology, particle size, and surfaces charge of HSNPs were investigated. The contact angles of water droplets on HSNP film surfaces were measured to investigate their wetting properties. Finally, superhydrophobic sand and polyurethane sponge were prepared by coating them with HSNPs and applied in the cleanup of oil spills of viscous heavy Arabian crude oil.

Fast adsorption of methylene blue, basic fuchsin, and malachite green by a novel sulfonic-grafted triptycene-based porous organic polymer

In this study, a novel triptycene-based porous polymer grafted with sulfonic acid (TPP-SO3H) was successfully synthesized by the post-synthetic modification of the non-functionalized polymer TPP. The polymer TPP-SO3H was well-characterized and was found to be a fast and effective absorbent for the cationic dyes methylene blue (MEB), basic fuchsin (BF), and malachite green (MG), with over 95% removal being observed within 10 min from initial concentrations of 100 mg L-1, 100 mg L-1, and 300 mg L-1, respectively. The adsorption process for MEB, BF, and MG was pH-dependent. The adsorption behaviours for MEB, BF, and MG follow pseudo-second-order kinetics and fit the Langmuir model. Moreover, the maximum adsorption capacities of MEB, BF, and MG at room temperature were 981.8 mg g-1, 586.2 mg g-1, and 1942.5 mg g-1, respectively. It is worth noting that the values of the MEB, BF, and MG adsorption capacities on TPP-SO3H were 5.5, 3, and 1.8 times that of the non-functionalized polymer TPP based on the same adsorbent weight. It is suggested that (i) there are strong electrostatic attractions between the sulfonic groups of the TPP-SO3H and cationic dyes and (ii) the higher surface area and good porosity may contribute to the high dye adsorption capacity. Furthermore, TPP-SO3H exhibited good cyclic stability, which can be regenerated at least five times without a significant loss of adsorption capacity. Therefore, the facile strategy synthesis, as well as the excellent adsorption capacity and reusability, make polymer TPP-SO3H an attractive adsorbent for wastewater treatment.

Amine functionalized 3D porous organic polymer as an effective adsorbent for removing organic dyes and solvents

We report the application of an amine functionalized triptycene-based 3D polymer (TPP-NH₂) as a novel adsorbent for the fast removal of organic dyes in aqueous solution and organic solvents.