A Review on Reducing Graphene Oxide for Band Gap Engineering

Abstract

Exfoliation, i.e. individual separation of carbon sheets, is of great interest to produce single-layered graphene nanosheets. Chemical or thermal treatments are popular approaches to exfoliate graphite chunks. In general, these conventional methods are assisted with intercalation via covalent or non-covalent functionalization, expansion, and swelling, adsorption of organic molecules in gas phase, solid nanoparticle insertion or direct molecular exfoliation. However, direct covalent modification of graphene is challenging and the zero-band gap of graphene limits its use in field-effect transistors in nanoelectronics. Therefore, the use of a band-gap tunable p-type semiconducting reduced graphene oxide (rGO) is an alternative route. There are several approaches to tune its band gap, including tailoring the chemistry. Critical parameters include the control of oxygen amount determined by the degree and time of oxidation and reduction conditions (e. g. temperature), often leading to nonstoichiometry. This short review therefore highlights the production of rGO focusing primarily on the effect of thermal treatmenton the nature and the role of oxygen during thermal exfoliation of GO. The impact of oxygen functionalization on the modulation of the band gap is also reviewed for chemically and thermally reduced GO, as well as chemically treated rGO followed by a thermal exfoliation.

Electrical conductivity, thermal conductivity, and rheological properties of graphene oxide-based nanofluids

“…Therefore, different band gap energies were reported for GO in the literature. In general, for non-stoichiometric and hygroscopic compounds like GO, a linear increase of the band gap with an increase in oxygen to carbon ratio has been established (Acik and Chabal 2012;Boukhvalov and Katsnelson 2008;Jung et al 2009). Figure 2a shows a typical TEM of GO.…”

Origin of the Chemical and Kinetic Stability of Graphene Oxide

“…Most of the efforts to control GO rely today on post-synthesis chemical and thermal treatments2425262728293031, favoring the occurrence of reduction mechanisms, loss of oxygen content, and thus partial restoration of graphene-like properties. Thermal reduction of GO, in particular, initiates at temperatures larger than 70°C30, it leads to the desorption of H 2 O and O 2 , but also CO and CO 2 3032, and consequently it is detrimental to the structural integrity of the graphene sheets and the physical properties of the reduced material.…”

Graphene oxide hole injection layer for high-efficiency polymer light-emitting diodes by using electrophoretic deposition and electrical reduction

“…Recently, studies on RGO properties, in particular, the band-gap difference between GO and RGO has been shown significant interest. It has been well demonstrated that the transformation of GO to RGO is associated with the decrease of its band-gap [5]. With band-gap engineering, GO has emerged as very important candidate in the field of materials.…”