The
physical properties of ultrathin transition metal dichalcogenides
(2D-TMDCs) make them promising candidates as active nanomaterials
for catalysis, optoelectronics, and biomedical applications. Chemical
modification of TMDCs is expected to be key in modifying/adding new
functions that will help make such promise a reality. We present a
mild method for the modification of the basal planes of 2H-MoS2 and WS2. We exploit the soft nucleophilicity of
sulfur to react it with maleimide derivatives, achieving covalent
functionalization of 2H-TMDCs under very mild conditions. Extensive
characterization proves that the reaction occurs through Michael addition.
The orthogonality and versatility of the thiol–ene “click”
chemistry is expected to allow the à la carte chemical manipulation of TMDCs.
One of the most attractive applications of carbon nanomaterials is as catalysts, due to their extreme surface-to-volume ratio. The substitution of C with heteroatoms (typically B and N as p- and n-dopants) has been explored to enhance their catalytic activity. Here we show that encapsulation within weakly doping macrocycles can be used to modify the catalytic properties of the nanotubes towards the reduction of nitroarenes, either enhancing it (n-doping) or slowing it down (p-doping). This artificial regulation strategy presents a unique combination of features found in the natural regulation of enzymes: binding of the effectors (the macrocycles) is noncovalent, yet stable thanks to the mechanical link, and their effect is remote, but not allosteric, since it does not affect the structure of the active site. By careful design of the macrocycles’ structure, we expect that this strategy will contribute to overcome the major hurdles in SWNT-based catalysts: activity, aggregation, and specificity.
Mechanically interlocking
redox-active anthraquinone onto single-walled
carbon nanotubes (AQ-MINT) gives a new and advanced example of a noncovalent
architecture for an electrochemical platform. Electrochemical studies
of AQ-MINT as an electrode reveal enhanced electrochemical stability
in both aqueous and organic solvents compared to physisorbed AQ-based
electrodes. While maintaining the electrochemical properties of the
parent anthraquinone molecules, we observe a stable oxygen reduction
reaction to hydrogen peroxide (H
2
O
2
). Using
such AQ-MINT electrodes, 7 and 2 μmol of H
2
O
2
are produced over 8 h under basic and neutral conditions,
while the control system of SWCNTs produces 2.2 and 0.5 μmol,
respectively. These results reveal the potential of this rotaxane-type
immobilization approach for heterogenized electrocatalysis.
Most air-stable 2D materials are relativelyi nert, which makes their chemicalm odification difficult. In particular,i nt he case of MoS 2 ,t he semiconducting 2H-MoS 2 is much less reactive than itsm etallicc ounterpart, 1T-MoS 2 .A s ac onsequence, there are hardly any reliable methods for the covalent modification of 2H-MoS 2 .A ni deal method for the chemical functionalization of such materials should be both mild, not requiring the introductiono falarge number of defects, and versatile, allowing for the decoration with as many different functional groups as possible. Herein, ac omprehensive study on the covalentf unctionalization of 2H-MoS 2 with maleimidesi sp resented. The use of ab ase (Et 3 N) leads to the in situ formationo fasuccinimide polymer layer, covalently connected to MoS 2 .I nc ontrast, in the absence of base, functionalization stops at the molecular level.M oreover,t he functionalization protocol is mild (occursa tr oom temperature), fast (nearlyc omplete in 1h), and very flexible (11different solvents and 10 different maleimides tested). In practical terms, the procedures described here allow for the chemistt om anipulate 2H-MoS 2 in av ery flexible way,d ecorating it with polymers or molecules, and with aw ide range of functional groups fors ubsequent modification. Conceptually,t he spurious formationo fa no rganic polymerm ight be general to other methods of functionalization of 2D materials, where al arge excesso fm olecular reagents is typically used.
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