Covalent functionalization
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Most air-stable 2D materials are relatively inert, which makes their chemical modification difficult. In particular, in the case of MoS2 , the semiconducting 2 H-MoS2 is much less reactive than its metallic counterpart, 1T-MoS2 . As a consequence, there are hardly any reliable methods for the covalent modification of 2 H-MoS2 . An ideal method for the chemical functionalization of such materials should be both mild, not requiring the introduction of a large number of defects, and versatile, allowing for the decoration with as many different functional groups as possible. Herein, a comprehensive study on the covalent functionalization of 2 H-MoS2 with maleimides is presented. The use of a base (Et3 N) leads to the in situ formation of a succinimide polymer layer, covalently connected to MoS2 . In contrast, in the absence of base, functionalization stops at the molecular level. Moreover, the functionalization protocol is mild (occurs at room temperature), fast (nearly complete in 1 h), and very flexible (11 different solvents and 10 different maleimides tested). In practical terms, the procedures described here allow for the chemist to manipulate 2 H-MoS2 in a very flexible way, decorating it with polymers or molecules, and with a wide range of functional groups for subsequent modification. Conceptually, the spurious formation of an organic polymer might be general to other methods of functionalization of 2D materials, where a large excess of molecular reagents is typically used.
- Klíčová slova
- 2D materials, MoS2, click chemistry, covalent functionalization, maleimide,
- Publikační typ
- časopisecké články MeSH
In the vast field of functionalization routes to carbon nanoforms, the fulfillment of such critical requirements as quick and nonharsh methods, good dispersibility, introduction of reactive groups, short reaction time, and low cost can be quite challenging. Traditional thermally induced diazonium chemistry on single-walled carbon nanotubes (SWCNTs) is revisited by using commercial anilines and providing useful insight into the versatility of this approach. Functionalized SWCNTs with multiple controllable features, such as degree (and ratio) of coverage, orthogonalization, doping, and high water dispersibility, are obtained by introducing benzenesulfonic acid and benzylamine moieties. The scenario opens up an avenue to address relevant applications in which most functionalization methods could not be applied in a straightforward way.
- Klíčová slova
- carbon nanotubes, covalent functionalization, diazonium reaction, solubility,
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Spatially resolved functionalization of 2D materials is highly demanded but very challenging to achieve. The chemical patterning is typically tackled by preventing contact between the reagent and material, which brings various accompanying challenges. Photochemical transformation on the other hand inherently provides remote high spatiotemporal resolution using the cleanest reagent-a photon. Herein, we combine two competing reactions on a graphene substrate to create functionalization patterns on a micrometer scale via the Mitsunobu reaction. The mild reaction conditions allow introduction of covalently dynamic linkages, which can serve as reversible labels for surface- or graphene-enhanced Raman spectroscopy characterization of the patterns prepared. The proposed methodology thus provides a pathway for local introduction of arbitrary functional groups on graphene.
- Klíčová slova
- Mitsunobu reaction, Raman spectroscopy, graphene, patterned functionalization, photochemistry,
- Publikační typ
- časopisecké články MeSH
Layered black phosphorus has been attracting great attention due to its interesting material properties which lead to a plethora of proposed applications. Several approaches are demonstrated here for covalent chemical modifications of layered black phosphorus in order to form P-C and P-O-C bonds. Nucleophilic reagents are highly effective for chemical modification of black phosphorus. Further derivatization approaches investigated were based on radical reactions. These reagents are not as effective as nucleophilic reagents for the surface covalent modification of black phosphorus. The influence of covalent modification on the electronic structure of black phosphorus was investigated using ab initio calculations. Covalent modification exerts a strong effect on the electronic structure including the change of band-gap width and spin polarization.
- Klíčová slova
- black phosphorus, covalent modifications, phosphorenes, surface analysis, surface chemistry,
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The combination of 2D materials opens a wide range of possibilities to create new-generation structures with multiple applications. Covalently cross-linked approaches are a ground-breaking strategy for the formation of homo or heterostructures made by design. However, the covalent assembly of transition metal dichalcogenides flakes is relatively underexplored. Here, a simple covalent cross-linking method to build 2H-MoS2 -MoS2 homostructures is described, using commercially available bismaleimides. These assemblies are mainly connected vertically, basal plane to basal plane, creating specific molecular sized spaces between MoS2 sheets. Therefore, this straightforward approach gives access to the controlled connection of sulfide-based 2D materials.
- Klíčová slova
- 2D materials, MoS2, covalent functionalization, covalent homostructure,
- Publikační typ
- časopisecké články MeSH
Few-layer and monolayer arsenic (arsenene) materials have been attracting great attention mainly from a theoretical perspective. Chemical modification of these materials would expand significantly the range of their applications. Here, we describe a chlorocarbene-mediated modification of exfoliated layered arsenic materials. Carbene-based species are highly reactive and offer further possibilities of functionalization. Our approach for modifying the arsenic surface by chlorocarbene generated from organolithium and dichloromethane resulted in a large surface coverage and a highly luminescent functionalized material, opening the door for its application in modern optoelectronic devices.
- Klíčová slova
- 2D materials, arsenic, carbene, layered materials, surface chemistry,
- Publikační typ
- časopisecké články MeSH
Manipulating nanoscopic objects by external stimuli is the cornerstone of nanoscience. Here, we report the implementation of dynamic covalent chemistry in the reversible binding and directional motion of fluorescent nanodiamond particles at a functionalized graphene surface via imine linkages. The dynamic connections allow for controlling the formation and rupture of these linkages by external stimuli. By introduction of pH gradients, the nanoparticles are driven to move along the gradient due to the different rates of the imine condensation and hydrolysis in the two environments. The multivalent nature of the particle-to-surface connection ensures that particles remain attached to the surface, whereas its dynamic character allows for exchange reaction, thus leading to displacement yet bound behavior in two-dimensional space. These results open a pathway for thermodynamically controlled manipulation of objects on the nanoscale.
- Klíčová slova
- 2D materials, directional nanoparticle motion, dynamic covalent chemistry, fluorescent nanodiamonds, graphene functionalization,
- Publikační typ
- časopisecké články MeSH
Monoelemental 2D-materials beyond graphene are attracting great attention. Although monolayer graphene or phosphorene can be prepared from its layered 3D form, graphite or black phosphorus, by exfoliation of a large van der Waals crystal, this route is not suitable for the preparation of 2D-germanene based materials due to the crystal structure and chemical properties of germanium. Unlike graphene or phosphorene, these materials are prepared by chemical exfoliation from bulk Zintl phases - here represented by calcium germanide. We describe the exfoliation and subsequent modification of calcium germanide, which yields layered germanium materials with alkyl or aryl groups. Different organic functional groups covalently attached to layered germanane exhibit a very intense fluorescence in the blue region, which makes them prospective materials for further application in optoelectronic devices. The described procedure for covalently functionalized germananes represents the way for the production of these materials.
- Publikační typ
- časopisecké články MeSH
Microcystins (MCs), produced by Microcystis sp, are the most commonly detected cyanotoxins in freshwater, and due to their toxicity, worldwide distribution, and persistence in water, an improvement in the monitoring programs for their early detection and removal from water is necessary. To this end, we investigate the performance of three covalent organic frameworks (COFs), TpBD-(CF3)2, TpBD-(NO2)2, and TpBD-(NH2)2, for the adsorption of the most common and/or toxic MC derivatives, MC-LR, MC-RR, MC-LA, and MC-YR, from water. While MC-LR and MC-YR can be efficiently adsorbed using all three COF derivatives, high adsorption efficiencies were found for the most lipophilic toxin, MC-LA, with TpBD-(NH2)2, and the most hydrophilic one, MC-RR, with TpBD-(NO2). Theoretical calculations revealed that MC-LA and MC-RR have a tendency to be located mainly on the COF surface, interacting through hydrogen bonds with the amino and nitro functional groups of TpBD-(NH2)2 and TpBD-(NO2)2, respectively. TpBD-(NO2)2 outperforms the adsorbent materials reported for the capture of MC-RR, resulting in an increase in the maximum adsorption capacity by one order of magnitude. TpBD-(NH2)2 is reported as the first efficient adsorbent material for the capture of MC-LA. Large differences in desorption efficiencies were observed for the MCs with different COFs, highlighting the importance of COF-adsorbate interactions in the material recovery. Herein we show that efficient capture of these toxins from water can be achieved through the proper selection of the COF material. More importantly, this study demonstrates that by careful choice of COF functionalities, specific compounds can be targeted or excluded from a group of analogues, providing insight into the design of more efficient and selective adsorbent materials.
- Klíčová slova
- adsorption, covalent organic frameworks, microcystin-LA, microcystin-LR, microcystin-RR, microcystin-YR, toxins,
- MeSH
- adsorpce MeSH
- chemické látky znečišťující vodu izolace a purifikace MeSH
- čištění vody metody MeSH
- Microcystis chemie MeSH
- mikrocystiny izolace a purifikace MeSH
- molekulární modely MeSH
- porézní koordinační polymery chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chemické látky znečišťující vodu MeSH
- mikrocystiny MeSH
- porézní koordinační polymery MeSH
Surface-confined synthesis is a promising approach to build complex molecular nanostructures including macrocycles. However, despite the recent advances in on-surface macrocyclization under ultrahigh vacuum, selective synthesis of monodisperse and multicomponent macrocycles remains a challenge. Here, we report on an on-surface formation of [6 + 6] Schiff-base macrocycles via dynamic covalent chemistry. The macrocycles form two-dimensional crystalline domains on the micrometer scale, enabled by dynamic conversion of open-chain oligomers into well-defined ∼3.0 nm hexagonal macrocycles. We further show that by tailoring the length of the alkyl substituents, it is possible to control which of three possible products-oligomers, macrocycles, or polymers-will form at the surface. In situ scanning tunneling microscopy imaging combined with density functional theory calculations and molecular dynamics simulations unravel the synergistic effect of surface confinement and solvent in leading to preferential on-surface macrocyclization.
