Reversibility of Graphene Photochlorination

Abstract

The reversibility of graphene photochemical chlorination was investigated. A high content of Cl is obtained through photochlorination, without changing C hybridization. To accommodate the incorporated Cl, graphene corrugation takes place. However, due to weak bonding, Cl atoms desorb during air exposure and long periods of storage. Chlorination also leads to graphene doping. When Cl is removed, doping decreases and graphene returns to its original morphology. Only a small amount of Cl (Cl/C ∼ 0.1) remains strongly bonded to graphene, most likely at grain edges and defects. Therefore, to maintain a precise doping level, Cl trapping methods are essential. Moreover, Cl removal using laser irradiation can be used to tune doping in micrometric areas, making it a promising technique to be used in applications where different doping levels are needed.

Azidated Graphene: Direct Azidation from Monolayers, Click Chemistry, and Bulk Production from Graphite

“…Gate-dependent measurement showed a substantial positive voltage shift for the conductance- V g transfer curve (Figure b), indicating enhanced p-doping, consistent with azido groups being electron-withdrawing. , A high conductance- V g slope was also noted (Figure b), indicative of high carrier mobility. Similar p-doping behavior with high conductivity and mobility has been noted before for highly chlorinated monolayer graphene. − As a pseudohalogen, the azido group is characterized by Hammett substituent constants comparable to that of halogens, and so it could affect graphene properties analogously. To this end, we found Raman spectroscopy of the azidated graphene (Figure S7) also behaved similarly as the highly chlorinated graphene, namely a significant decrease in the intensity ratio of the 2D peak over the G peak but little increase in the D peak signal. ,, It is thus possible that the azido group similarly p-doped graphene without inducing high levels of defects in the graphene lattice, − hence the measured high electrical conductivity.…”

“…Similar p-doping behavior with high conductivity and mobility has been noted before for highly chlorinated monolayer graphene. − As a pseudohalogen, the azido group is characterized by Hammett substituent constants comparable to that of halogens, and so it could affect graphene properties analogously. To this end, we found Raman spectroscopy of the azidated graphene (Figure S7) also behaved similarly as the highly chlorinated graphene, namely a significant decrease in the intensity ratio of the 2D peak over the G peak but little increase in the D peak signal. ,, It is thus possible that the azido group similarly p-doped graphene without inducing high levels of defects in the graphene lattice, − hence the measured high electrical conductivity. Cycloaddition of ADIBO–PEG 4 –biotin led to substantial n-doping while keeping the large conductance- V g slope (Figure b).…”

“…To this end, we found Raman spectroscopy of the azidated graphene (Figure S7) also behaved similarly as the highly chlorinated graphene, namely a significant decrease in the intensity ratio of the 2D peak over the G peak but little increase in the D peak signal. 43,45,46 It is thus possible that the azido group similarly p-doped graphene without inducing high levels of defects in the graphene lattice, 43−46 hence the measured high electrical conductivity. Cycloaddition of ADIBO−PEG 4 −biotin led to substantial ndoping while keeping the large conductance-V g slope (Figure 5b).…”

Advances and Trends in Chemically Doped Graphene

“…Such a laser‐based technique allows one to tune the doping level at the nanoscale, which can lead to interesting applications. [ 133 ]…”

Recent Developments in Graphene and Graphene Oxide: Properties, Synthesis, and Modifications: A Review

“…Therefore, ionic bonds between chlorine and carbon atoms occur when there are no D peaks in the Raman spectra. [173,174] Copetti et al, [175] showed that reversible ionic chlorination of graphene sheets could be achieved by photo-chlorination. Their results demonstrated that despite covalent halogenation, chlorination led to an increase in charge carrier density and a decrease in the resistance of the graphene sheets.…”