Defluorination of Fluorographene Oxide via Solvent Interactions

Abstract

CommuniCation(1 of 7) 1600346 F in FG cannot stabilize the FG-ammonia structure. [4] Hence, it is important to develop a method for the large-scale controlled fluorination/defluorination of graphene/FG. [15,16] Conventional F doping level control in graphene relies on the tuning the amount of reagents or flow and time of the fluorination gases and process. [11,17] Mechanical exfoliation of graphite fluoride is the first method reported for FG synthesis while chemical exfoliation of various types of fluorographites resulting to FGO is pursued for its large-scale synthesis. [1,[18][19][20] Pumera and co-workers also reported the synthesis of dichlorocarbenefunctionalized fluorographene by the addition of dichlorocarbene to fluorographite and followed by its exfoliation. [21] Further, the concentration of F in FG/FGO can be decreased by the postsynthesis routes such as electron beam irradiation, [22,23] hydrothermal, [24] and ultrasonic treatments. [25] Recently, it has shown that the CF bonds can be removed (defluorination) by exposing fluorinated graphene to ultraviolet irradiation for long time in aromatic solvents such as toluene and benzene. [26] Further, another recent report explores the possibilities of defluorination by the solvent-based treatment of fluorinated graphene, where the semiionic CF bonds were removed from fluorinated graphene upon its treatment with dipolar solvents such as N-methyl-2-pyrolidinone via ultrasonication. [27] Here a simple defluorination technique for FGO using moderately polar solvents such as tetrahydrofuran (THF, which was not observed by Wang et al.), [27] a versatile water miscible solvent and a favorite carrier fluid for graphene-based paints, [28] is demonstrated and DFT studies are conducted to probe the interactions between solvents and FG/graphene. [29] The selective interaction of solvent with the CF bonds preserves almost all the other oxygen functionalities, and this in turn helps for the development of good quality functional coatings of FGO. The change in the visible light absorption by FGO upon defluorination is confirmed by its color change from white to dark, and the effect of defluorination in heterogeneous electron transport (HET) kinetics [30,31] is studied using inner and outer redox probes such as K 3 [Fe(CN) 6 ] and Ru(NH 3 ) 6 Cl 3 in 1 M KCl solution. This study has extended to the oxidation of biologically relevant molecules such as ascorbic acid (AA) and dopamine (DA) in phosphate buffered saline (PBS) solution using various F containing FGOs, and sensing of ammonia gas molecules by monitoring the changes in the electronic conductivity upon gas exposure is demonstrated.In order to understand the interactions between FG and various solvents, interactions of THF, toluene, isopropyl alcohol (IPA), carbon tetrachloride (CCl 4 ), and acetic acid (not shown here in the calculations) with FG were studied using DFT. The energy gaps (E g ) of the complexes were determined from the

Fluorographene: Synthesis and sensing applications

“…23 Recently, the authors have demonstrated that the interactions between polar solvents and C-F bond in FG are highly crucial for the solvent assisted defluorination, and even moderately polar solvents such as tetrahydrofuran (THF) can interact with FGO to remove C-F bonds in a day or two without any extensive sonication. 40 This method also proves that other oxygen functionalities are kept intact even after 30 days of THF treatment indicating that the reaction is quite selective. Hence this can be considered as an important step toward the development of controllably fluorinated graphene/graphene oxide based devices and sensors.…”

“…8). 40 It is found that the solvent assisted interactions can reduce the F content in FGO, and this has a significant role in the response of the FG based conductometric sensor. Low F containing sample (30 days treated FGO) has the highest response indicating that changes in the conductivity (along with adsorption properties as observed from the DFT studies) of FGO upon defluorination and its effects in the sensing response.…”

“…[37][38][39][40] It is also shown that the defluorination can be achieved by exposing FG to ultraviolet irradiation for long time in aromatic solvents like toluene and benzene. 23,41 On a different report, the possibilities of defluorination by the solvent based treatment of fluorinated graphene is also discussed, where the semi-ionic C-F bonds were removed from fluorinated graphene upon its treatment with dipolar solvents such as N-methyl-2-pyrrolidinone (NMP) via ultra-sonication.…”

“…HOMO-LUMO gaps for various solvents with FG and graphene, calculated using density functional theory 40. …”

Synthesis of Ni/Co/Al-layered triple hydroxide@brominated graphene hybrid on nickel foam as electrode material for high-performance supercapacitors

“…The G band (in the region of 1500-1600 cm À1 ) arises from the rst order scattering of the E 2g phonon at the Brillouin zone center, resulting from the bond stretching of sp 2 carbon lattice pairs in both rings and chains. 44,45 A strong peak located at 531 cm À1 is typically assigned to NCA-LTH. 9 It is known that the integrated intensity ratio of the bands (I D /I G ) is used to qualitatively analyze the structural defects and disorder of graphite materials.…”