Chemical functionalization of graphene

Experimental and theoretical results on chemical functionalization of graphene are reviewed. Using hydrogenated graphene as a model system, general principles of the chemical functionalization are formulated and discussed. It is shown that, as a rule, 100% coverage of graphene by complex functional groups (in contrast with hydrogen and fluorine) is unreachable. A possible destruction of graphene nanoribbons by fluorine is considered. The functionalization of infinite graphene and graphene nanoribbons by oxygen and by hydrofluoric acid is simulated step by step.Comment: 13 pages, 11 figures. Invited paper for J. Phys. Cond. Mater. "Graphene" special issue. References added, typos correcte

Towards electron transport measurements in chemically modified graphene: The effect of a solvent

Chemical functionalization of graphene modifies the local electron density of the carbon atoms and hence electron transport. Measuring these changes allows for a closer understanding of the chemical interaction and the influence of functionalization on the graphene lattice. However, not only chemistry, in this case diazonium chemistry, has an effect on the electron transport. Latter is also influenced by defects and dopants resulting from different processing steps. Here, we show that solvents used in the chemical reaction process change the transport properties. In more detail, the investigated combination of isopropanol and heating treatment reduces the doping concentration and significantly increases the mobility of graphene. Furthermore, the isopropanol treatment alone increases the concentration of dopants and introduces an asymmetry between electron and hole transport which might be difficult to distinguish from the effect of functionalization. The results shown in this work demand a closer look on the influence of solvents used for chemical modification in order to understand their influence

Development of covalent triazine frameworks as heterogeneous catalytic supports

Covalent triazine frameworks (CTFs) are established as an emerging class of porous organic polymers with remarkable features such as large surface area and permanent porosity, high thermal and chemical stability, and convenient functionalization that promotes great potential in heterogeneous catalysis. In this article, we systematically present the structural design of CTFs as a versatile scaffold to develop heterogeneous catalysts for a variety of chemical reactions. We mainly focus on the functionalization of CTFs, including their use for incorporating and stabilization of nanoparticles and immobilization of molecular complexes onto the frameworks

Regio-selective substitution at the 1,3- and 6,8-positions of pyrene for the construction of small dipolar molecules

© 2015 American Chemical Society. This article presents a novel asymmetrical functionalization strategy for the construction of dipolar molecules via efficient regioselective functionalization along the Z-axis of pyrene at both the 1,3- and 6,8-positions. Three asymmetrical ly substituted 1,3-diphenyl-6,8-R-disubsituted pyrenes were fully characterized by X-ray crystallography, photophysical properties, electrochemistry, and density functional theory calculations

Functionalization of two-dimensional tungsten diselenide and MXene for tunable optical property

Since the discover of graphene in 2004, two-dimensional (2D) materials have gained tremendous attention because of their distinctive properties relative to their bulk form. Particularly, transition metal dichalcogenides (TMDs) and 2D transition metal carbides and nitrides (MXenes) have shown promising applications in flexible electrical and optoelectronic devices. Due to the atomically thin nature, the electronic band structures of these materials are very sensitive to the small changes in the lattice and the surface functionalization, offering a dimension to tune the properties of the materials. In this thesis, approaches to functionalize monolayer WSe2 and MXene were explored. The as-grown chemical vapor deposition (CVD) monolayer WSe2 flakes were treated by plasma assisted doping method. Specifically, Methane plasma was used as carbon dopant source to introduce p-type lattice doping into monolayer WSe2. In addition, chemical reactions between perfluorophenylazides (PFPA) organic molecules and WSe2 flakes were conducted where the PFPA molecules may covalently bonded to the WSe2 surface. Similarly, the PFPA functionalization was applied to MXene, an emerging 2D material with high conductivity. Shifts and intensity change were observed in Raman spectra after the functionalization, indicating structural and electric structure changes might be introduced. Further characterizations of the structures and electric properties will be taken in the near future

A new route towards uniformly functionalized single-layer graphene

It is shown, by DFT calculations, that the uniform functionalization of upper layer of graphite by hydrogen or fluorine does not change essentially its bonding energy with the underlying layers, whereas the functionalization by phenyl groups decreases the bonding energy by a factor of approximately ten. This means that the functionalized monolayer in the latter case can be easily separated by mild sonication. According to our computational results, such layers can be cleaned up to pure graphene, as well as functionalized further up to 25% coverage, without essential difficulties. The energy gap within the interval from 0.5 to 3 eV can be obtained by such one-side funtionalization using different chemical species.Comment: 15 pages, 3 figures, to appear in J. Phys. D: Applied Physic

Vapor phase surface functionalization under ultra violet activation of parylene thin films grown by chemical vapor deposition

Various reactive gas phase treatments have been investigated as surface functionalization dry processes with the goal to improve the wettability of parylene C films, keeping good optical properties in the visible range. The films were grown on different substrates by chemical vapor deposition with thicknesses ranging from 300 to 1630 nm. The polymer surface was treated under ultra violet (UV) irradiation at 254 nm in reactive atmospheres including He, H2O, H2O2, O2 and ambient air. The UV/O2 treatment is the most efficient since the water contact angle decreases from 100° to 6° while the transmittance is maintained at 90% in the visible wavelengths. Furthermore it exhibits long life stability. The functionalization mechanism is discussed in relation with previous reports