Intercalated Graphene Oxide Research Articles

Reduced graphene oxide–cuprous oxide composite via facial deposition for photocatalytic dye-degradation

Cubic Cu2O nanoparticles have been successfully synthesized on n-propylamine (PA) intercalated graphene oxide (GO) with uniform distribution followed with a subsequent hydrazine hydrate reduction process to generate Cu2O/PA/rGO composite. For comparison, Cu2O conjugated reduced graphene oxide (Cu2O/rGO) composite was also synthesized using the same method. The as-prepared Cu2O/PA/rGO and Cu2O/rGO nanocomposites are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis, and Electrochemical impedance spectra (EIS) measurements. UV/vis diffuse reflectance spectroscopy was employed to estimate band gap energies of cuprous oxide composites. The results show that the intercalation of PA into the layered GO increases the surface area of the composites and provides an efficient strategy to load Cu2O due to the large and uniform distribution of active sites for anchoring copper ions. The surface area of the Cu2O/PA/rGO (123m2/g) nanocomposite was found to be almost 2.5 times higher than that of Cu2O/rGO (55.7m2/g). The as-prepared Cu2O/PA/rGO show significant improvement on both adsorption capacity and photocatalytic activity towards organic pigment pollution compared with Cu2O/rGO under identical performance conditions.

P-Xylylenediamine intercalation of graphene oxide for the production of stitched nanostructures with a tailored interlayer spacing

The p-xylylenediamine intercalation reaction of graphene oxide (GO) has been investigated as a convenient and simple approach to the preparation of pillared-type graphene-based materials with a tailored interlayer spacing. Powder X-ray diffraction studies in combination with thermo-gravimetric analyses and swelling tests have demonstrated the generation of a constrained system (covalently “stitched”) along the c-axis exhibiting a considerably increased interlayer distance compared to the starting, pristine GO. X-ray photoelectron spectroscopy measurements were consistent with a cross-linking process involving oxygen functional groups (basically epoxides) typically present at the GO basal plane. Finally, nitrogen adsorption–desorption isotherms (BET plots), transmission electron microscopy and scanning electron microscopy micrographs have been used to underline the increased specific surface area and porosity of the amine intercalated material, as well as to emphasize the morphological differences between the two samples (pristine GO and intercalated material). The production of tailored GO-based nanostructures with improved chemico-physical properties paves the way towards the multigram synthesis of porous carbon-based nanomaterials.

Stacking of water molecules in hydrophilic graphene oxides characterized by Kelvin probe force microscopy

We directly measured local surface potentials of graphene oxide and poly (sodium 4-styrenesulfonate) intercalated graphene oxide (PSSGO) films, as a function of humidity, using Kelvin probe force microscopy. Our results showed a decrease in the work function of the graphene oxide (GO) film as the humidity increased. This behavior was explained using the first-principle calculation in which water molecules stacked onto the GO film, resulting in a lower local work function and ripples of the surface potential. The ripples directly measured by Kelvin Probe Force microscopy were consistent with the calculation. While the PSSGO film did not show the ripples as the humidity increased. Our results directly showed that absorbed water molecules on the films change the local surface potential and the work function such that its performance in many applications will be affected.

Formation and Decomposition of CO2 Intercalated Graphene Oxide

The formation, stability, and decomposition of CO2 intercalated graphene oxide was analyzed by FTIR, TGA-MS, TGA-IR, AFM, and SEM for the first time. We found that the formation starts at 50 °C and develops up to 120 °C. The formation process can be best observed by FTIR spectroscopy, and the product is stable at ambient conditions. At higher temperatures, the decomposition of CO2 intercalated graphene oxide occurs due to the release of water, CO2, and CO that can be monitored by TGA-MS and TGA-IR analysis. AFM and SEM images can visualize the formation of blisters in GO films that become instable at 210 °C. We further prepared graphene oxide with a low water-content and found that the formation of CO2 was significantly suppressed and CO became the major species responsible for the weight loss. In addition we prepared 18OH2 treated graphene oxide to elucidate the formation process of CO2 and found C16O18O by TGA-MS analysis that proves the crucial role of water during CO2 formation. From these experiments we propose that hydrate species are key-intermediates for the formation of CO2. Hence, it seems likely that rearrangement reactions that can proceed via hydrate intermediates, known from organic chemistry, are probably responsible for the formation of carboxylic acids at the edges of graphene oxide sheets after sonication of graphite oxide. Further, our investigations prove that graphene oxide is less stable than shown by TGA measurements. This has a high impact on the electronic properties of reduced graphene oxide, especially for all those using it for electronic applications.

Emerging photoluminescence in azo-pyridine intercalated graphene oxide layers

Inspite of being a potential material for electronic applications graphene possesses very poor optical properties, which need to be modified to make it suitable for optoelectronic devices. To achieve superior optical properties, graphene oxide (GO) sheets are functionalized with azo-pyridine to form a new intercalated structure with an interlayer separation of 0.9 nm. These azo-pyridine intercalated GO sheets show superior optical properties with bright blue emission via excited state intra-molecular proton transfer (ESIPT) which have potential applications in graphene based optoelectronic devices.

Surfactant-intercalated, chemically reduced graphene oxide for high performance supercapacitor electrodes

A series of surfactant-stabilized graphene materials were prepared by intercalation of graphene oxide (GO) with different surfactants, tetrabutylammonium hydroxide (TBAOH), cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzene sulfonate (SDBS), followed by reduction using hydrazine. The materials were fully characterized, and the surfactants were found to be successfully intercalated in both GO and the reduced graphene oxide. As well as stabilizing the morphology of single layer or few-layer structure of graphene sheets during reduction, the presence of surfactants in graphene materials can also enhance the wettability of the graphene surface and thus improve its performance as a supercapacitor electrode. When the graphene materials were used as an electrode for a supercapacitor, the highest specific capacitance of 194 F g−1 was obtained from the TBAOH stabilized graphene at a specific current density of 1 A g−1 in 2 M H2SO4 electrolyte.