Graphene oxide conversion into controllably carboxylated graphene layers via photoreduction process in the inert atmosphere

Abstract

The one-step method for graphene oxide (GO) simultaneous reduction and carboxylation via ultraviolet irradiation in the inert atmosphere has been reported. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) data revealed that the proposed approach allows to obtain reduced graphene oxide (rGO) films, containing up to 10 at.% of carboxyl groups. The carboxyl groups concentration can be tuned within the range of 3 to 10 at.% by controlling the oxidation degree of the irradiated GO via the preliminary low-temperature air heating. Furthermore, no carboxylation effect is observed in the case of irradiation of the completely reduced GO films. This coincides with our previous results, validating the proposed model of GO carboxylation based on photoinduced conversion of basal-plane hydroxyl groups and ketones into carboxyl ones. Despite a different degree of carboxylation, all the obtained samples demonstrate almost complete elimination of basal plane groups and restoration of the graphene flakes aromatic structure. This fact is emphasized by the sheet resistance measurements, demonstrating that the obtained C-xy graphene exhibits high electrical conductivity. As a net result, the material obtained by the presented method shows promising applications in the manufacturing of biosensor transducers owing to both its conductive nature and presence of carboxyl groups, playing the role of the anchoring points for biomolecules.     

Comparative Study of Conventional and Quasi-Freestanding Epitaxial Graphenes Grown on 4H-SiC Substrate

Semiconductors - The structural and some other characteristics of quasi-freestanding single-layer graphene obtained by annealing of the buffer layer in the flow of hydrogen are studied in...     

Uniform graphene oxide films fabrication via spray-coating for sensing application

Abstract

A spray-coating technique for deposition of thin uniform graphene oxide films with a thickness of several tens of nanometers was developed. Among distinctive features of the technique is the low substrate heating temperature, which allows preserving most oxygen-containing functional groups and coat a wide range of substrates. The morphology of the spray-coated graphene oxide films with flakes of different lateral sizes was investigated. The local laser-induced photo-thermal reduction of thin graphene oxide thin films was demonstrated. The sensitivity of reduced graphene oxide to water vapor was also measured. Spray-coating and laser reduction techniques can be further applied for humidity sensor fabrication.     

Reduced graphene oxide resistance in composites with polystyrene of different molecular masses

Abstract

Multi-layered reduced graphene oxide after UV-perforation (RGO_p) flakes of large areas, some of them up to 1?mm in diameter, have been produced on polystyrene surface during special precipitation method of RGO_p/polystyrene composites from benzene solution. For this, composites on the base of polystyrenes of different molecular masses: 4500?Da; 6000?Da; 9000?Da; and 45,000?Da were synthesized. Very low resistances at the room temperature for some RGO_p flakes deposited from benzene-petroleum ether solution of composite of 9000?Da molecular mass were obtained. The absolute values of measured resistances turned out to be almost 3 orders lower than copper resistance. This result can be related to formation a high conductive phase in the reduced graphene oxide bilayer inclusions. In the case of RGO_p flakes produced from our highest molecular mass polystyrene composite (45,000?Da) resistance was high and varying from semiconducting values to non-conductive state.     

Structure and Properties of Thin Graphite-Like Films Produced by Magnetron-Assisted Sputtering

The structural, electrical, and optical properties of thin graphite-like films produced by magnetron- assisted sputtering onto crystalline silicon and quartz at substrate temperatures in the range from 320 to 620°C are studied. From analysis of the Raman spectra, it is established that, as the substrate temperature is elevated, the crystallite size increases and the concentration of structural defects and the content of amorphous carbon in the phase composition of the films decrease. It is found that, as the substrate temperature is elevated, the maximum of the absorption intensity in the ultraviolet spectral region of the optical absorption spectra shifts to longer wavelengths and the absorption intensity in the visible and near-infrared spectral regions increases. As the deposition temperature is elevated, the conductivity of the films increases from 0.2 Ω^–1 cm^–1 at 320°C to 30 Ω^–1 cm^–1 at 620°C.     

Atomic Force Microscopy Study of Monodisperse Carbon Nanoparticles

Semiconductors - Monodisperse carbon nanodots and nanodiamond particles were studied by AFM method. Particle size distributions were calculated using AFM and DLS data. The results obtained...     

Adapter modification for a high-speed centrifuge rotor for use with standard medical polypropylene tubes

A rotor adapter for a Sartorius Sigma 3-30KS centrifuge (rotor 12158), which is used for centrifugal separation of detonation nanodiamond particles with different sizes at accelerations of 6 × 10⁴ g, was developed and tested. The developed adapter allows one to use common medical polypropylene test tubes after their simple modification instead of the expensive test tubes that are usually recommended by the manufacturer of the centrifuge. As a result, the use of the adapter significantly decreases expenses on experiments, where fractionation of various liquid dispersions is applied.     

A Carbon Nanostructure for a Thermoelectric Generator

Technical Physics Letters - We demonstrate that it is technologically possible to obtain graphite-like films which can be used for the creation of a thermoelectric generator. The proposed...