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Journal Name
ChemComm
DOI: 10.1039/C4CC07936A
PFPA. The method applies to pristine graphene prepared by solvent
exfoliation, mechanical exfoliation and CVD. By using pre-prepared
nanoparticles, the size, shape, and morphology of nanoparticles can
be controlled in advance. The type of nanoparticles is not limited to
SNPs and AuNPs in this study so long as they are functionalized
with PFPA. We have prepared a variety of PFPA-functionalized
nanoparticles including iron oxide (Fe3O4),36 quantum dots,37
titanium dioxide nanoparticles, silver nanoparticles, and polymer
nanoparticles. The method developed here could be readily used to
synthesize graphene hybrid nanomaterials with these nanoparticles.
The new method should pave the way for the fabrication of high
performance graphene-based hybrid nanomaterials that can be
utilized in applications including catalysis, nanoelectronics, sensing
devices, and therapeutics.
Fig. 3 XPS spectra of FLG conjugated with SNPs (a-d) and AuNPs
(e-h).
X-ray photoelectron spectroscopy (XPS) was performed to further
study the covalent bond formation between the nanoparticles and Acknowledgment
graphene. Figure 3 shows the survey and high resolution spectra of This work was supported by NSF (CHE-1112436) and a startup fund
FLG flakes conjugated with SNPs (SNP-FLG, a-d) and AuNPs from the University of Massachusetts Lowell.
(AuNP-FLG, e-h). The XPS system is a Vacuum Generators Escalab
MK II x-ray photoelectron spectrometer equipped with a dual Mg/Al
Notes and references
x-ray source and with a 150 degree spherical sector electron energy
a Department of Chemistry, University of Massachusetts Lowell, Lowell,
analyzer operated in constant analyzer energy mode. The vacuum
level during XPS analysis was at 1 x 10-9 torr. Survey and core level
Massachusetts 01854, United States, Fax: +1-978-334-33013; Tel: +1-
spectra were collected at pass energy of 100 eV and 50 eV,
respectively. All spectra were referenced to the C1s binding energy
bMaterials Characterization Laboratory, University of Massachusetts
Lowell, Lowell, Massachusetts 01854, United States
position of adventitious carbon taken at 285.0 eV. The XPS spectra
showed the anticipated F 1s and N 1s peaks, as well as the Si 2p
peak in the SNP-FLG sample (Figure 3a, 3d) and the Au 4f peak in
the AuNP-FLG sample (Figure 3e, 3h). The XPS of PFPA-
functionalized surfaces has two N 1s peaks at 402.1 eV and 405.6 eV
with the intensity ratio of 2:1, corresponding to the two outer and the
one inner N of the azide.30 After PFPA-functionalized NPs were
conjugated to FLG, the XPS spectra of SNP-FLG (Figure 3b) and
AuNP-FLG (Figure 3f) showed two N 1 s at 400.2 eV and 401.4 eV,
repectively. The disappearance of the peak at 406.5 eV was a result
from the loss of nitrogen when the azide decomposed upon
photolysis. When PFPA-SNPs or PFPA-AuNPs were irradiated in
the presence of FLG, only those PFPAs that were in contact with
FLG would be involved in the covalent bond formation with FLG.
The majority of PFPA on the nanoparticles, upon UV irradiation,
gave singlet perfluorophenyl nitrene that could either react with the
solvent DCB to give CH insertion products (i.e., aniline derivatives)
or undergo intersystem crossing to triplet nitrene which then yields
an aniline product.31 Based on this, we assign the larger peak at
400.2 eV to the N in the various aniline products.32 The N of the
amide bond in PFPA-silane (Scheme 1) also shows up in the same
region, thus contributing to the larger peak in Figure 3b.33 The
†
Electronic Supplementary Information (ESI) available: Experimental
details on the synthesis of nanoparticles and graphene-nanoparticle
gonjugates, Raman spectra of graphene samples, and electron microscopy
images of control samples are presented in supporting information. See
DOI: 10.1039/c000000x/
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35
structure formed between graphene and PFPA.34,
The peaks at
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285.0, 286.4, and 288.1 eV in the C 1s spectra are consistent with
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Taken together, the XPS results demonstrated that the nanoparticles
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Conclusions
In summary, we have successfully developed a general method to
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C=C bonds in graphene whereby PFPA-functionalized nanoparticles
can be readily conjugated to graphene by a simple photoactivation of
Zhang, Nanoscale, 2011, 3, 1446-1450.
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