Controlled Covalent Functionalization of 2 H-MoS2 with Molecular or Polymeric Adlayers

Article abstract of DOI:10.1002/chem.202000068

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 (Et₃N) 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.

Full text of DOI:10.1002/chem.202000068

A Journal of
Accepted Article
Title: Controlled Covalent Functionalization of 2H-MoS2 with Molecular
or Polymeric Adlayers.
Authors: Ramiro Quirós-Ovies, Manuel Vázquez Sulleiro, Mariano
Vera-Hidalgo, Javier Prieto, I. Jénnifer Gómez, Víctor
Sebastián, Jesús Santamaría, and Emilio M. Pérez
This manuscript has been accepted after peer review and appears as an
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of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
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to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.202000068
Link to VoR: http://dx.doi.org/10.1002/chem.202000068
Supported by

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Controlled Covalent Functionalization of 2H-MoS
or Polymeric Adlayers.
2
with Molecular
Ramiro Quirós-Ovies,[a], # Manuel Vázquez Sulleiro,[a], # Mariano Vera-Hidalgo,[a] Javier Prieto,[a] I.
Jénnifer Gómez,[b] Víctor Sebastián,[c],[d] Jesús Santamaría,*[c],[d],[e], Emilio M. Pérez*[a]
[
a]
R. Quirós-Ovies, Dr. M. V. Sulleiro, M. Vera-Hidalgo, J. Prieto, Prof. E. M. Pérez
IMDEA Nanociencia
C/Faraday 9 Ciudad Universitaria de Cantoblanco, 28049 Madrid, Spain
E-mail: emilio.perez@imdea.org
[
[
b]
c]
Dr. I. J. Gómez
CEITEC Masaryk University
Kamenice 5, 625 00 Brno, Czech Republic
Dr. V. Sebastián, Prof. J. Santamaría
Institute of Nanoscience of Aragon (INA) and Department of Chemical and Environmental Engineering
Campus Rio Ebro, 50018 Zaragoza, Spain
E-mail: jesus.santamaria@unizar.es
[
d]
Dr. V. Sebastián, Prof. J. Santamaría
Instituto de Ciencia de Materiales de Aragon (ICMA), Consejo Superior de Investigaciones Científicas (CSIC-Universidad de Zaragoza)
Zaragoza, Spain
[
e]
Prof. J. Santamaría
Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN)
2
8029 Madrid, Spain
Supporting information for this article is given via a link at the end of the document.
Abstract: Most air-stable 2D materials are relatively inert, which
span the whole range of band-gaps from hexagonal boron nitride
(h-BN), an insulator (band-gap ca. 5-6 eV),[4] transition metal
dichalcogenides (TMDCs), which are semiconductors with band-
gaps in the Vis-NIR region (1-2 eV),[5] to black phosphorus (band-
gap 0.3-2 eV).[6, 7]
makes their chemical modification difficult. In particular, in the case of
MoS
metallic counterpart, 1T-MoS
any reliable methods for the covalent modification of 2H-MoS
2
, the semiconducting 2H-MoS
. As a consequence, there are hardly
. An
2
is much less reactive than its
2
2
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
Within this toolbox of new materials, TMDCs show well defined
bandgaps that make them particularly suitable for semiconductor
technology.[8-10] The development of reliable tools for the chemical
modification of TMDCs is crucial to achieve their full technological
potential.[11-17] Decoration of TMDCs materials with molecular
fragments via noncovalent approaches, mostly based on
dispersion/solvophobic interactions, is relatively easy and has
consequently led the way towards potential applications. For
example, selective chemical sensors[18, 19] and enhanced
photodetectors[20, 21] have already been described using this
strategy. Methods for the covalent modification of TMDCs are
much more scarce and nearly exclusively limited to the metallic
1T phase.[22-26]
study on the covalent functionalization of 2H-MoS
presented. The use of a base (Et N) leads to the in situ formation of a
succinimide polymer layer, covalently connected to MoS . In contrast,
2
with maleimides is
3
2
in the absence of base, functionalization stops at the molecular level.
Moreover, functionalization protocol is mild (occurs at room
temperature), fast (nearly complete in 1h), and very flexible (11
different solvents and 10 different maleimides tested). In practical
terms, the procedures described here allow for the chemist to
manipulate 2H-MoS in a very flexible way, decorating it with polymers
2
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.
We have recently described a “click” chemistry protocol for the
covalent modification of colloidal semiconducting 2H-MoS
2
and
WS , obtained through liquid phase exfoliation (LPE) from the
2
bulk.[27-30] In our strategy, inspired by the many examples of thiol-
ene chemistry in polymer chemistry and biochemistry,[31-33] we
exploited the soft nucleophilicity of sulfur to make it react with the
prototypical soft electrophile, maleimides (Figure 1).[34]
Here, we present a comprehensive study of the covalent
Introduction
functionalization of 2H-MoS
changes to the different variables in the reaction conditions, we
describe a reliable protocol for the molecular modification of MoS
2
with maleimides. Via systematic
The ever-expanding toolbox of bidimensional materials and
properties offers the promise of a technological revolution.[1] Since
the discovery of graphene,[2] many other bidimensional materials
have been isolated and characterized.[3] Prominent examples now
2
with maleimides featuring a wide range of chemical functionalities.
Our experiments reveal the formation of a covalently connected
1
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organic polymer adlayer when using increased amounts of
molecular reagent in combination with a base.
Figure 1. (a) General scheme of the two routes for the functionalization of MoS
2
with maleimides. b) TGA (Air, 10 ºC min-1) of exfoliated MoS
and Bn-mal (same colour code). d-e) XPS spectra of C core levels for
. f-g) XPS spectra of S core levels for exfoliated MoS and Bn-polysucc-MoS
2 (black), Bn-polysucc-
MoS
2
(orange) and Bn-mal (blue). c) ATR-FTIR of exfoliated MoS
and Bn-polysucc-MoS
2, Bn-polysucc-MoS2
exfoliated MoS
2
2
2
2.
This unexpected formation of a polymer in-situ can be useful in
certain circumstances and might be common to other
functionalization protocols.[35, 36] By removing the base from the
reaction protocol, we obtain pure molecular functionalization.
centrifugation conditions), a higher degree of functionalization
was obtained. We also investigated the influence of reaction time,
temperature, and the relative concentration of reagents on the
degree of functionalization (Table S1). The main observations
stemming from these studies can be summarized as follows: The
reaction is fast, nearly complete after 1 h (52% functionalization
by TGA, see Figure S7) and only increases to 66% after 16 h.
Temperature studies were carried out from room temperature
until reflux (Figure S8). However, the functionalization degree was
reduced with increasing temperature, a result consistent with the
Results and Discussion
Few-layers MoS colloids were obtained through LPE in N-
2
methyl-2-pyrrolidone, NMP, using an ultrasonic probe. In this
case, we resorted to NMP instead of 2-propanol (i-PrOH)-water
mixtures[34] to increase the concentration of the colloids and
stability of the dispersed MoS
temperatures. The use of different concentrations of MoS
significant effect on the surface functionalization, following the
expected tendency, that is, the more the MoS solution is diluted
i.e. the larger the excess of Bn-mal) the higher the degree of
2, which is less stable at higher
2
had a
facilitate characterization. Exfoliated MoS
non-exfoliated material using centrifugation. The formation of few-
layer 2H-MoS was proved, after redispersion in acetonitrile
ACN), by UV-Vis extinction, Raman spectroscopy, X-ray Powder
2
was separated from
2
(
2
functionalization (Figure S9). Furthermore, similar variations were
observed by reducing the concentration of Bn-mal (Figure S10).
Decreasing the amount of Bn-mal results in a lower degree of
functionalization. However, due to the small difference between 1
and 5 mmol of Bn-mal, we conclude that we are employing a large
excess of Bn-mal. In fact, a quick calculation reveals that, even
under the milder conditions used (entry 26, Table S1), we are
using at the very least ca. 100 equivalents of Bn-mal with respect
to S, assuming that all flakes are monolayer (our sample is mostly
(
Diffraction (XRD) and transmission electron microscopy (TEM,
see Figures S1-4). The flakes showed layers with their larger
dimension of 374±125 nm on average, as determined by TEM
measurements.
The transfer to ACN of the exfoliated MoS
protocol described previously,[37] then N-benzylmaleimide (Bn-
mal) and triethylamine (Et N) were added and the mixture was
2
was done following a
3
stirred overnight (Figure 1). The mixture was washed with ACN
and i-PrOH to remove all physisorbed Bn-mal, which was
confirmed by UV-Vis of the residues (Figure S5). Moreover, the
TGA profiles of the mixture without any washing could clearly
differentiate physisorbed (weight loss at 170 ºC) from covalently
attached maleimide (weight loss at 390º C, Figure S6). We first
analysed the degree of functionalization varying degree of
exfoliation, by fine-tuning the sonication conditions and
centrifugation procedure, using TGA (Table S1). Unsurprisingly,
we observed that, for materials with a higher degree of exfoliation
5
-10 layers) and that one out of six sulphur atoms can be reactive,
to account for the steric hindrance of the organic addend. In
agreement with this, we note that the degree of functionalization
observed by TGA is too large to be compatible with the decoration
of MoS
2
with molecular Bn-succ, which should be < 40% even
assuming all flakes to be monolayer (see Table S2).
(those obtained with longer sonication times and/or more intense
2
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a)
b)
of a S-C bond.[39] The N 1s peak from the succinimide core, which
is absent in the control MoS , is clearly visible at 400.7 eV upon
2
S1
functionalization (Figure S12). The presence of new bands in the
carbon region is in good agreement with new components for
C=O (288.7 eV) and C-S/C-N, (286.0-287,0 eV). XRD and Raman
spectroscopy do not present a significant shift on the signals after
functionalization (Figure S13-14). This is consistent with a picture
in which only some of the surface S atoms are functionalized while
the majority of the sample remains in the bulk (see Table S2), and
where the functionalization does not significantly affect the
S2
1
000nm
200nm
electronic and structural properties of the MoS lattice (i.e. no
changes in crystalline polytype, significant doping, noticeable
changes in the number of defects, etc.).[34]
2
c)
d)
C
1
0 1/nm
.27 nm
Some examples of high functionalization of MoS are reported in
2
0
.7 nm
0
the literature.[26, 40, 41] In this work, the large degree of
functionalization indicated by TGA experiments (up to 76%)
differs markedly from that determined by XPS (12.8% of the S-C
new component, that would correspond to a 23% weight loss in
TGA, see Eq. S1, which is also in very good agreement with a
very high yielding modification for 3-10 layers, see Table S2).
Some studies pointed out the possibility of the
homopolymerization and copolymerization of N-functionalized
maleimides in the presence of bases.[42-44] To investigate if the
formation of polysuccinimides of this type was feasible under our
reaction conditions, we prepared a mixture of Bn-mal (5 mmol)
0
.5 nm
Spectrum 1- S1
Spectrum 2- S2
C
S
Cu
MoMo
0
2
4
6
8
10 12 14 16 18 20 1nm
Energy, keV
Figure 2. a-b) High-angle annular-dark-field scanning transmission electron
microscopy (HAADF-STEM) images at different magnifications of polysucc-
MoS
observed. c) Energy Dispersive X-Ray Spectroscopy analysis of dashed-red
line areas in b). d) HR-HAADF-STEM image of polysucc-MoS shows the
2 flakes. An organic layer with a less bright contrast than MoS2 flakes was
2
and Et N and stirred it overnight in ACN. After separation of
3
interlayer arrangement. Insets, Fourier transform (FFT) pattern and atomic
resolution image with interplanar spacing. Maleimide scope used for the
covalent functionalization of MoS2.
unreacted Bn-mal, 1.5% of the initial weight was isolated as
insoluble pink powder. MALDI-TOF analysis confirmed the
formation of a polymer with a periodic repetition of 187 Da, which
corresponds perfectly to the succinimide fragments of polysucc
(
Figure 1a). The formation of a Gaussian envelope from 2 to 10
kDa with a maximum peak at 4890 corresponds to 26 units of
homopolymer (see Figure S15). Furthermore, H NMR (400 MHz)
To gain further insight on the functionalization process we decided
to fully characterize a sample which presented a 76% TGA weight
1
loss (entry 27 in Table S1), comparing it with reference MoS ,
2
experiments confirmed the disappearance of the alkene signals,
and the appearance of signals at 4.61 and 4.40 ppm, that can be
attributed to the new aliphatic protons. Moreover, all signals
appear broadened, which is characteristic of the formation of high-
molecular weight species (see Figure S16).[45]
The strong evidence of formation of a S-C bond (ATR-FTIR and
XPS) presented above indicates that MoS
covalently with polysucc, rather than by physisorption of the
polymer after formation in solution. A functionalization with
polysucc would also be consistent with the large weight loss
observed by TGA. AFM and STEM micrographs also support this
which was subjected to identical reaction and purification
conditions in the absence of Bn-mal (Figure 1b). The slow
decomposition of reference MoS
2
(black trace), observed
between approximately 370 and 550 ºC from the derivative,
amounts to a total of 14% weight, and corresponds to the
oxidation of MoS
By comparing to the experiments in N
2
due to the presence of air in the experiment;[38]
atmosphere (Figure S6),
2
is functionalized
2
air, and the unfunctionalized reference, TGA suggests (Figure 1c),
that the first weight loss of the functionalized sample (orange
trace) at 390 ºC can be attributed to defunctionalization of the
attached molecule, the second at 450 °C to degradation of
hypothesis. In AFM we observe that the polysucc-MoS flakes
2
defective MoS
remaining MoS
pronounced in the functionalized material compared to the
pristine MoS . ATR-FTIR of the functionalized sample (Figure 1c)
2
and the third one at 720 °C to degradation of all
present roughness of a height of 15 nm, very similar to that of the
pure polysucc (Figure S17). With the element-sensitive resolution
of STEM, we confirm that we do not find self-standing polymer
particles, but rather MoS
organic matter (Figure 2 a-b). EDS analysis also indicates that
polysucc is grafted to MoS flakes since the only presence of C
was obtained at the less bright areas of the polysucc-MoS
HAADF-STEM image (Figure 2-c). Finally, the high resolution
HAADF-STEM image of a representative MoS flake reveals the
periodic atomic arrangement of the MoS layers, with an interlayer
distance of 0.7±0.2 nm (Figure 2-d). On the other hand, the
interplanar spacing was measured to be 0.27 nm according to the
periodic pattern in the atomic resolution image, matching up with
that of the (100) facet of MoS
transform (FFT) pattern (Figure 2d).
2. The second weight loss is much more
2
2
flakes surrounded by amorphous
showed conclusive evidence of functionalization, like the
presence of the main vibrational modes of Bn-mal like the
carbonyl stretch (1714 cm-1) and the disappearance of the alkene
C-H bending mode (840 cm-1 in Bn-mal), and the emergence of a
S-C stretching mode (728 cm-1) that confirms the covalent
functionalization of the material through a new S-C covalent
bond.[34] X-ray photoemission spectroscopy (XPS) further
confirmed the covalent attachment of the organic polymer (Figure
2
2
2
2
1
d-g, Figure S11-12, Table S3). As a reference, the core level of
C is centered at adventitious carbon (284.8 eV). We find clear
differences with the control sample experiment (cs-MoS ). The S
p (162.7 eV) peak becomes broader, and a new component is
required for spectrum fitting that corresponds well to the formation
2
(2.736 Å)[46] and the fast Fourier
2
2
3
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left stirring for one month under otherwise identical conditions, we
obtained a very similar degree of functionalization (6% wt
comparing it with its pristine MoS , see Figure S21).
2
Figure 4. Maleimide scope used for the covalent functionalization of MoS2.
Figure 3. a) TGA (air, 10 ºC.min-1) of exfoliated MoS
2
(black) and Bn-succ-MoS
(green) and Bn-
mal (blue). c-d) XPS spectra of S and C core levels Bn-succ-MoS
2
(green). b) ATR-FTIR of exfoliated MoS2 (black), Bn-succ-MoS2
2.
The influence of different solvents was also investigated by
performing the reaction in 10 more solvents, besides ACN, from
the very polar methanol to the very unpolar hexane (see Table S4,
Figure S22-23), including some that presented unstable
dispersions (i.e. dioxane). A low degree of functionalization (<
We note that grafting polymers onto the surface of 2D materials
can be useful to decorate them with multiple functional groups, for
instance to enhance binding to biomolecules for biosensing
purposes,[47-49] but is typically not the desired outcome when
reacting molecules with nanomaterials.[35] We therefore also
studied how to control/prevent polymerization to obtain
exclusively molecular functionalization. In this case, we tested
experimentally that the polymerization of maleimide is not
observable under our experimental conditions if a base is not
2%) was found in polar protic solvents like methanol, ethanol or i-
PrOH. This observation, together with the fact that the reaction
works well in the absence of a base, points towards a radical
mechanism for the 2H-MoS -maleimide reaction, instead of an
2
anionic Michael-type addition.[31, 32] Dichloromethane (8%) and
chloroform (6%) both showed higher functionalization by TGA
compared to ACN. However, the slope of the loss is not as well
defined as in ACN (Figure S22), which might indicate that some
physisorbed Bn-mal is still present, even after the washings.
When the reaction was carried out in DMF we found 7% of organic
material, comparable with ACN, but a more tedious cleaning of
the material was required. Remarkably, ATR-FTIR confirmed the
presence of the C-S stretching in all solvents, except dioxane (see
Figure S23).
With the optimal reaction and purification conditions already
determined, we tested the scope of the reaction using 10 different
maleimides (Figure 4), some of which were intentionally selected
to be used as chemical handles for further modification (5-10).
Within experimental error, and considering the different molecular
weights, we observe degrees of functionalization within the same
order of magnitude (see Table 1 and Figures S24-25) for all the
maleimides, except 6, which shows a much larger loading of
organic material (16%). We explain this result noting that 6
features an aniline that probably acts as a base catalyst in the
formation of a homopolymer, as shown above.
present. Figure 3 shows the characterization of Bn-succ-MoS
2.
The weight loss of Bn-succ-MoS observed by TGA dropped
2
considerably, to 6% wt (Figure 3a). This is more in line with what
can be expected for a rather effective surface reaction considering
our degree of exfoliation (see Table S2). Again, we do not observe
any weight loss before 300 ºC meaning physisorbed Bn-mal was
successfully removed during the washing step. In accordance
with the lower amount of organic material, ATR-FTIR showed less
intense signals of the material. However, the new C-S stretching
mode (728 cm-1) and carbonyl stretch (1714 cm-1) are clearly
observed (Figure 3b). XPS of Bn-succ-MoS presents a broad
2
band at the S 2p peak requiring a new component (6.8%) for the
fitting that can correspond to S-C bond (orange, Figure 3c).
Analysis of the C region is particularly informative: components
for C=O (288.7 eV), C-S/C-N, (286.0-287,0 eV) are again needed
for the correct fitting, but in this case, the relative intensity of the
components are much smaller in accordance with molecular
functionalization (Figure 3d). Finally, a N 1s peak that is not visible
in the control sample is observed in the surface of the Bn-succ-
MoS
samples, with and without Et
Figure S18). HR-HAADF-STEM images of pristine MoS
succ-MoS , showed how the crystallinity of the material was not
modified with the functionalization (see Figure S19).
2
material (Table S3). The TGA is identical for both control
N, and the pristine material (see
, Bn-
3
2
2
Lastly, we decided to test the scope and flexibility of these
reaction conditions. First, we performed the reaction at different
concentrations of Bn-mal (0.1 to 5 mmol). The functionalized
MoS showed a significant variation of the functionalization by
2
TGA, from 2% to 6% (see Figure S20). This seems to be the upper
limit for molecular functionalization. In fact, when the reaction was
4
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Chemistry - A European Journal
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dispersion process was repeated three times with 60 mL of acetonitrile
Table 1. Summary of the characterization of the covalent functionalization of
(ACN) and three times with 60 mL of 2-propanol (i-PrOH).
MoS
2
with different maleimides
n-MoS Weight loss
2
ν C=O
ν C-S
General procedure for 2D-MoS functionalization
2
[
%]
[cm-1
]
[cm-1]
The general procedure for the MoS
2 functionalization was performed by
Bn-succ-MoS
2
dispersing 6 mg of exfoliated MoS in 10 mL of ACN with a brief sonication
2
6
± 1
1714
728
in a 20 mL vial. Then, the maleimide derivative was added and dissolved
with vigorous stirring. The vial was closed with a lid and parafilm and
allowed to react at room temperature for 16 h.
After that, the dispersion was filtered with Omnipore 0.45 µm PTFE
membrane filters, 25 mm in diameter. In order to wash the sample, the
filter with the material was redispersed in 20 mL of ACN, placed again in
the filtration system and then the dispersion was filtered adding 40 mL
more of the solvent. This process was repeated three times with ACN and
three times with i-PrOH.
2
3
4
5
6
7
8
9
-MoS
-MoS
-MoS
-MoS
-MoS
-MoS
-MoS
-MoS
2
2
2
6 ± 2
1.0 ± 0.3
2 ± 1
1714
1702
1698
1704
1714
1714
1694
1714
1698
728
728
728
731
731
-
2
2
2
8 ± 1
16 ± 1
2 ± 3
Acknowledgements
2
2
7 ± 3
728
731
728
The European Research Council (ERC-StG-307609; ERC-PoC-
13 ± 4
9 ± 3
ERC-AdG-742684),
MINECO
(CTQ2017-86060-P
and
CTQ2016-79419-R) the Comunidad de Madrid (MAD2D-CM
S2013/ MIT-3007) are gratefully acknowledged. IMDEA
Nanociencia acknowledges support from the “Severo Ochoa”
Programme for Centres of Excellence in R&D (MINECO, Grant
SEV- 2016-0686). Part of the work was carried out with the
support of CEITEC Nano Research Infrastructure (ID LM2015041,
MEYS CR, 2016–2019), CEITEC Brno University of Technology.
1
0-MoS2
Conclusion
In summary, after disclosing that maleimides react with
semiconducting MoS and WS 34 we now present a thorough
study of the covalent functionalization of 2H-MoS with
maleimides. We report that the maleimide-MoS click reaction is
2
2,
2
R.Q.O and M.V.S contributed equally to this work.
2
shown to be mild, fast, and extremely versatile. To achieve these
conclusions, we explore changes in reagents, stoichiometries,
concentrations, solvents, and temperature and expose that the
Keywords: 2D materials • MoS
maleimide • “click” chemistry.
2
• covalent functionalization •
use of a base (Et
adlayer, which is covalentely attached to MoS
3
N) promotes formation of a polymeric maleimide
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a base, the functionalization stops at the molecular level. In both
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the scope of the reaction, showing a wide tolerance for different
solvents and a broad range of functional groups. The fact that the
reation proceeds without a base, and particularly well in polar
aprotic solvents, but is inhibited in protic solvents, suggests that it
occurs through a radical mechanism.[41]
Experimental Section
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[
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mg/mL dispersion of MoS in N-Methyl-2-pyrrolidone (NMP) was
2
[4]
[5]
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Entry for the Table of Contents
A comprehensive study of the reaction between 2H-MoS
2
and maleimides is presented. The use of a base leads to the formation of a
succinimide polymer layer covalently connected to MoS . In the absence of base, functionalization stops at the molecular monolayer.
2
The functionalization protocol is mild, fast, and very flexible.
Twitter usernames: @IMDEA_Nano, @emiliomperezlab, @MSulleiro
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