Abstract
Fluorographene has been recently shown to be a suitable platform for synthesizing numerous graphene derivatives with desired properties. In that respect, N-octylamine-modified fluorographenes with variable degrees of functionalization are studied and their nonlinear optical properties are assessed using 4 ns pulses. A very strong enhancement of the nonlinear optical response and a very efficient optical limiting action are observed, being strongly dependent on the degree of functionalization of fluorographene. The observed enhanced response is attributed to the increasing number of defects because of the incorporation of N-heteroatoms in the graphitic network upon functionalization with N-octylamine. The present work paves the way for the controlled covalent functionalization of graphene enabling a scalable access to a wide portfolio of graphene derivatives with custom-tailored properties.
Highlights
In recent years, fluorographene [1,2] (FG) has become a template for the synthesis of new members of the graphene family [3,4,5], with controllable chemical and optical properties, suitable for a plethora of applications such as biosensing [6], gas sensing on surfaces [7] and solar cell technologies [8]
All the FG derivatives were found to exhibit reverse saturable absorption (RSA) behavior, under all the experimental conditions used, in both the visible and infrared excitation regimes. In principle, such an RSA response can be due to two-photon absorption (2PA) or excited state absorption (ESA) [24]
The nonlinear optical (NLO) responses of the FG and the FG-OAx derivatives were investigated by means of the Z-scan technique, along with their optical limiting (OL) action, under various excitation wavelengths ranging from visible (450 nm) to NIR (1750 nm)
Summary
Fluorographene [1,2] (FG) has become a template for the synthesis of new members of the graphene family [3,4,5], with controllable chemical and optical properties, suitable for a plethora of applications such as biosensing [6], gas sensing on surfaces [7] and solar cell technologies [8]. Graphene, FG possesses great chemical activity because of the electronegative fluorine that attaches to carbon atoms along with the formation of various structural defects, placing FG among the suitable carbon precursors for the tunable and scalable synthesis of new graphene derivatives with desired properties [9,10]. Doping FG with heteroatoms, such as nitrogen, can significantly alter its electronic structure due to tailored defect-induced states, leading to novel 2D materials whose optical and electronic properties can be controlled by modifying the amount of nitrogen (%N) incorporated into the graphenic lattice. Four FG derivatives, namely FG-OAx, with different F and N contents (ranging from 55% down to 2.3%, and from 2.9% up to 8.1%, respectively), were synthesized in order to demonstrate and quantify the effects of such functionalization on the NLO properties and OL action of the aforementioned derivatives. The further exploitation of these defect-engineered FGs can lead to materials suitable for various photonic and optoelectronic applications
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