The Influence of the Size and Oxidation Degree of Graphene Flakes on the Process of Creating 3D Structures during Its Cross-Linking

Abstract

This article presents the results of the cross-linking of oxidized flake graphene (GO) using hydrazine at room temperature. Conducting the process at temperatures up to 30 °C allowed to eliminate the phenomenon of thermal GO reduction to its non-oxidized form. In addition, based on the Infrared and Raman spectroscopy as well as X-ray photoelectron spectroscopy (XPS) analysis, the cross-linking ability of GO was observed depending on its size and degree of oxidation. These parameters were associated with selected physicochemical and electrical properties of obtained 3D structures. Three GO flakes sizes were tested in three different oxidation degrees. It was shown that, regardless of the size of GO, it is crucial to achieve a specific oxidation degree threshold which for the conducted tests was a >20% share of oxygen atoms in the whole structure. This value determines the ability to cross-link with hydrazine thanks to which it is possible to synthesize the spatial structure in which the π–π interactions among individual flakes are significantly reduced. This directly translates into the fact that the 3D structure shows an electrical resistance value in the range of 4–103 Ω, depending on the size and oxidation degree of the used material. The explanation of this phenomenon related to the electrical conductivity of 3D structures was confirmed based on the molecular modeling of the chemical structures.

Impact of a Graphene Oxide Reducing Agent on a Semi-Permeable Graphene/Reduced Graphene Oxide Forward Osmosis Membrane Filtration Efficiency

“…This means that hydrazine centrifugation is necessary to clean the surface of the reduced GO to get rid of the toxic residues of the reducer used. Nitrogen-containing compounds allow not only for the reduction of GO but also the formation of bridges between carbon atoms in different rGO flakes [ 21 , 22 ]. On the other hand, following reduction with vitamin C, a wide band belonging to the vibrations of hydroxyl groups (constituting a component of the -COOH group) disappears, while a weaker maximum appears, which shifts towards the range corresponding to free hydroxyl groups.…”

“…In the next step, rGO sediment was extensively vortexed and mixed using an ultrasonic cleaner for 15 min. The washing procedure was repeated six times [ 21 ].…”

“…As effective chemical reducers hydrazine, metal hydrates (e.g., NaBH 4 ), ascorbic acid, hydroiodic acid, or hot strong alkaline solutions can be listed [ 20 ]. Besides reduction, hydrazine allows the creation of 3D structures based on cross-linked graphene or graphene oxide [ 21 , 22 ]. rGO may have different hydrophobicity, number of oxygen-containing groups, and better dispersion which may change the way of covering defects in graphene and, as a result, the performance of the membrane.…”

Al2O3 + Graphene Low-Friction Composite Coatings Prepared By Sol–Gel Method

“…FTIR spectra of G1 and G2 graphene, demonstrated in Figure 4a, were found to exhibit several absorption bands of carbon and oxygen-containing groups characteristic for graphene oxide: the absorption band around 1000 cm −1 for C-O stretching vibration bonds, band around 1200 cm −1 for C-OH stretching, and band around 1600 cm −1 for carbon-carbon bonds conjugated with carbon-oxygen bonds [56,57]. The broad peak at 3400 cm −1 was characteristic for stretching vibrations of -OH groups.…”

Spatial Graphene Structures with Potential for Hydrogen Storage

“…Mesoporous graphene structures were also obtained through the introduction of long-chain polyamide for the sake of separation of the graphene planes [20]. Among chemical compounds that can act as pillars leading to three-dimensional structures are also polyethyleneimine [21], poly(vinyl alcohol) [22], and hydrazine [23]. Pillared nanostructures are also achieved by combining carbon nanotubes (CNT) and graphene [24].…”