We describe the benign
wet chemical synthesis, characterization,
and third-order nonlinear optical properties of hydrogenated fluorographene,
namely, of a new 2D counterpart of hydrogenated graphene (graphane).
The presence of hydrogen in hydrogenated fluorographene was confirmed
using infrared spectroscopy, X-ray photoelectron spectroscopy, and
thermal gravimetric analysis coupled with evolved gas analysis. The
nonlinear optical properties of the derivative were investigated in
the visible and infrared using picosecond laser excitation and were
compared to those of graphene and fluorographene. All samples were
found to exhibit important nonlinear optical response, with hydrogenated
fluorographene exhibiting the largest response under visible excitation
(ca. 1 order of magnitude higher compared to graphene and fluorographene).
This is among the highest recorded effects ever observed for any graphene-based
materials, including graphene oxide presented elsewhere. The results
reveal the importance of the nature of the functional group and the
degree of functionalization (i.e., fluorination and hydrogenation)
on the nonlinear optical properties of graphenes. It is likely that
highly polarized donor-π electron-acceptor regions within a
layer result in such large optical nonlinearities.
The synthesis and characterization of two thiophenol‐modified fluorographene derivatives, namely methoxythiophenol‐and dimethylaminothiophenol‐modified fluorographenes, are reported, while their third‐order nonlinear optical response were thoroughly investigated under both visible (532 nm) and infrared (1064 nm) with 35 ps and 4 ns laser pulses. The graphene derivatives were obtained by partial nucleophilic substitution/reduction of fluorographene by the corresponding organic thiophenols, and were fully characterized by techniques including infrared/Raman spectroscopy, X‐ray photoelectron spectroscopy, atomic force spectroscopy, and high‐resolution transmission microscopy. This type of modification resulted in graphenic structures where the attached thiol groups, sp2 domains, and the residual fluorine groups act as donors, π bridges, and acceptors, respectively. Both derivatives exhibited large nonlinear optical response compared to fluorographene, and have potential applications in optical limiting as an alternative to fullerenes.
Graphene derivatives and defect-engineered
graphenes have attracted
the interest of researchers owing to the excellent and tunable properties
they exhibit. In this work the optical limiting performance of two
defect-engineered boron- and nitrogen-doped reduced graphene oxides
is investigated. Both graphenes are found to exhibit exceptional and
broadband optical limiting action ranging from 532 to 2200 nm. Their
optical limiting efficiency was found to be superior to that of all
the other graphene derivatives studied to date, exhibiting a gradually
decreasing optical limiting onset, reaching the record low value of
∼0.002 J cm–2 at 2200 nm. The results demonstrate
the potential of engineering the defects of such reduced graphene
oxides, resulting in very broadband and efficient optical limiting
graphene derivatives, showing a promising method to further tailor
their optical and optoelectronic properties.
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