Selective modification of two-dimensional MoS2 nanosheets by polymer grafting

Surface functionalization of two-dimensional nanomaterials beyond graphene: Applications and ecotoxicity

Two dimensional (2D) nanomaterials have emerged as promising candidates in nanotechnology due to their excellent physical, chemical, and electronic properties. However, they also pose challenges such as environmental instability and low biosafety. To address these issues, researchers have been exploring various surface functionalization methods to enhance the performance of 2D nanomaterials in practical applications. Moreover, when released into the environment, these 2D nanomaterials may interact with natural organic matter (NOM). Both intentional surface modification and unintentional environmental corona formation can alter the structure and physicochemical properties of 2D nanomaterials, potentially affecting their ecological toxicity. This review provides a comprehensive overview of covalent functionalization strategies and non-covalent interactions of 2D nanomaterials beyond graphene with organic substances, examining the resultant changes in material properties after modification. Covalent functionalization methods discussed include nucleophilic substitution reactions, addition reactions, condensation, and coordination. Non-covalent interactions are classified by substance type, covering interactions with NOM, in vivo biomolecules, and synthetic compounds. In addition, the review delves into the effects of surface functionalization on the toxicity of 2D nanomaterials to bacteria and algae. This discussion contributes to a foundational understanding for assessing the potential ecological risks associated with 2D nanomaterials.

Polymer Brush-Functionalized MoS2 as a Water-Based Lubricant Additive

Water-based lubricants have the advantages of low cost, easy cleaning, and environmental friendliness, and are suitable for various lubrication applications. However, the limited tribological properties of pure water-based lubricants restrict their use. To improve these properties, water-based lubrication additives can be employed. Molybdenum disulfide (MoS2) is widely used in tribology because of its stability, corrosion resistance, and wear resistance, but it has poor dispersion in water. To address this, MoS2 functionalized with poly(3-sulfopropyl methacrylate potassium salt) (MoS2+PSPMA) is successfully prepared by grafting polymer brushes onto MoS2 using ultraviolet light. The results show that MoS2+PSPMA exhibits significantly better dispersion stability in water compared to unmodified MoS2. Additionally, MoS2+PSPMA demonstrates superior tribological properties as a water-based lubrication additive. During reciprocating friction, MoS2+PSPMA disperses effectively in water, forming a protective film on the wear surface that reduces friction. As an additive, MoS2+PSPMA indicates good dispersion and a low friction coefficient in water, positioning it as a promising candidate for future water-based lubricants.

Polymer Brushes and Surface Nanostructures: Molecular Design, Precise Synthesis, and Self-Assembly

For over two decades, polymer brushes have found wide applications in industry and scientific research. Now, polymer brush research has been a significant research focus in the community of polymer science. In this review paper, we give an introduction to the synthesis, self-assembly, and applications of one-dimensional (1D) polymer brushes on polymer backbones, two-dimensional (2D) polymer brushes on flat surfaces, and three-dimensional (3D) polymer brushes on spherical particles. Examples of the synthesis of polymer brushes on different substrates are provided. Studies on the formation of the surface nanostructures on solid surfaces are also reviewed in this article. Multicomponent polymer brushes on solid surfaces are able to self-assemble into surface micelles (s-micelles). If the s-micelles are linked to the substrates through cleavable linkages, the s-micelles can be cleaved from the substrates, and the cleaved s-micelles are able to self-assemble into hierarchical structures. The formation of the surface nanostructures by coassembly of polymer brushes and "free" polymer chains (coassembly approach) or polymerization-induced surface self-assembly approach, is discussed. The applications of the polymer brushes in colloid and biomedical science are summarized. Finally, perspectives on the development of polymer brushes are offered in this article.

Sheet-Isolated MoS2 Used for Dispersing Pt Nanoparticles and its Application in Methanol Fuel Cells

It is highly challenging to activate the basal plane and minimize the π-π stacking of MoS2 sheets, thus enhancing its catalytic performance. Here, we display an approach for making well-dispersed MoS2 . By using the N-doped multi-walled carbon nanotubes (NMWCNTs) as an isolation unit, the aggregation of MoS2 sheets was effectively reduced, favoring the dispersion of Pt nanoparticles (noted as Pt/NMWCNTs-isolated-MoS2 ). Excellent bifunctional catalytic performance for methanol oxidation and oxygen reduction reaction (MOR/ORR) were demonstrated by the produced Pt/NMWCNTs-isolated-MoS2 . In comparison to Pt nanoparticles supported on MoS2 (Pt/MoS2 ), the MOR activity (2314.14 mA mgpt -1 ) and stability (317.69 mA mgpt -1 after 2 h of operation) on Pt/NMWCNTs-isolatedMoS2 were 24 and 232 times higher, respectively. As for ORR, Pt/NMWCNTs-isolated-MoS2 holds large half-wave potential (0.88 V) and high stability (92.71 % after 22 h of operation). This work presents a tactic for activating the basal planes and reducing the π-π stacking of 2D materials to satisfy their applications in electrocatalysis. In addition, the proposed sheet-isolation method can be used for fabricating other 2D materials to promote the dispersion of nanoparticles, which assist its application in other fields of energy as well as the environment.

Poly(2-isopropenyl-2-oxazoline) as a reactive polymer for materials development

Poly(2-isopropenyl-2-oxazoline) has attracted growing interest as a reactive polymer that can be used as a starting material for the construction of more complex structures.

Brush-like polymers: design, synthesis and applications

With the development of controlled polymerisation, almost all polymerisation strategies have been successfully transplanted to surface-initiated polymerisation. The resulting polymer brushes have emerged as an effective tool for surface functionalization and modulation of the surface properties of materials. To meet various demands it is possible to tailor a material surface with polymer brushes that have diverse dimensionalities, morphologies and compositions. The crowded environment within polymer brushes as well as the stretched conformation of polymer chains sometimes provide unique physicochemical properties, which lead to the delicate creation of inorganic-organic hybridised nanostructures, anti-fouling coatings, biomedical carriers, and materials for use in lubrication, photonics and energy storage. So far, challenges remain in the high-precision synthesis and topological control needed to realize extended applications of polymer brushes. In this Feature Article, we highlight the topology, potential application prospects and various synthetic protocols, particularly for recently established methods, for the efficient synthesis of polymer brushes, as well as their benefits and limitations.

Polymer Brushes on Hexagonal Boron Nitride

Direct covalent functionalization of large-area single-layer hexagonal boron nitride (hBN) with various polymer brushes under mild conditions is presented. The photopolymerization of vinyl monomers results in the formation of thick and homogeneous (micropatterned, gradient) polymer brushes covalently bound to hBN. The brush layer mechanically and chemically stabilizes the material and allows facile handling as well as long-term use in water splitting hydrogen evolution reactions.