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.

In the present work, the nonlinear optical properties of some single- and few-layered graphene dispersions under femtosecond laser excitation were studied using the Z-scan technique and are compared in order to evaluate the effect of the number of graphenic layers and the influence of the laser excitation conditions on the measurements. The experimental evidences obtained indicate that the nonlinear optical response of these graphenes’ dispersions under low repetition rate laser excitation conditions (i.e., 10 Hz) is several orders of magnitude lower than that reported using higher repetition rate laser excitation conditions (as e.g., kHz, MHz). To further investigate these experimental findings, Z-scan combined with a thermal lensing measurement technique was used to study the presence and the building of thermal/cumulative effects occurring under high repetition rate conditions. It was shown that thermal/cumulative effects were dominant, obscuring entirely the observation of the electronic origin nonlinear optical response. The contributions of both mechanisms were evaluated and unambiguously distinguished. To the best of our knowledge, this is the first work, investigating the nonlinear optical properties of single- and few-layered graphene, under low and high repetition rate laser excitation, providing a more accurate insight about the nonlinear optical response of graphene.

In this work, the nonlinear optical (NLO) response of some graphene dispersions is investigated under low (i.e., 10 Hz) and high (i.e., 80 MHz) repetition rate femtosecond (fs) laser excitation conditions, using Z -scan, optical Kerr effect (OKE), and a combination of Z -scan and thermal lensing techniques. It is shown, that the NLO response of graphene dispersions is negligible under low repetition rate fs laser excitation, while it becomes very large under high repetition rate laser excitation. In the latter case, it is shown that the observed very large NLO response arises entirely from thermal cumulative effects.

The preparation of the first soluble quaterrylene derivative featuring peripheral tert‐butyl substituents and sterically hindering, core‐anchored triflate groups has been achieved. This involves a facile synthetic route based on an oxidative coupling of perylene precursors in the presence of H2O2 as oxidant. The steric hindrance between the TfO substituents at the central bay position of the quaterrylene board triggers a strong deformation of the central perylene planarity, which forces the quaterrylene platform to adopt a twisted geometry as shown by X‐ray analysis. Exceptionally, photophysical investigations show that the core‐twisted quaterrylene phosphoresces in the NIR spectral region at 1716 nm. Moreover, third‐order nonlinear optical measurements on solutions and thin film containing the relevant molecule showed very large second hyperpolarizability values, as predicted by theoretical calculations at the CAM‐B3LYP/6‐31G** level of theory, making this material very appealing for photonic applications.

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