Reactive Graphene Research Articles

Deep analysis of adsorption isotherm for rapid sorption of Acid Blue 93 and Reactive Red 195 on reactive graphene.

Graphene-based adsorbent was prepared by adopting a green synthetic route via the chemical exfoliation of graphite and low-temperature thermal activation. Prepared reactive graphene (RG) was characterized through various techniques, and its adsorption capabilities for textile dye removal were investigated for Acid Blue-93 (AB) and Reactive Red-195 (RR) under different operational conditions. The dye sorption equilibrium and mechanism were comprehensively studied using isotherm and kinetic models and compared statistically to explain the sorption behavior. Results show AB and RR adsorption by RG attains equilibrium in 60min and 70min, with a high sorption quantity of 397mgg-1 and 262mgg-1 (initial dye concentration of 100mg L-1), respectively. The dye sorption anticipates that the high surface area (104.52 m2 gm-1) and constructed meso-macroporous features of RG facilitated the interaction between the dye molecules and graphitic skeleton. The R-P isotherm fitted the best of equilibrium data, having the least variance in residuals for both dyes (AB = 0.00031 and RR = 0.00047). The pseudo-second order model best fitted the kinetics of sorption on RG, with chemisorption being the predominant process delimiting step. The overall results promise the dye removal capability of RG to be an efficient adsorbent for azo-based dyes from textile effluents.

Revealing the Improved Catalytic Properties of Modified Graphene-like Structures

The surface morphology and electronic structure of hexagonal graphene onion rings (HGORs), a modified graphene structure, were investigated to confirm the possibility as an efficient catalyst when compared to graphene. After confirming the formation of HGORs with a smaller width (~4.2 μm) from scanning electron microscopy (SEM) and optical microscopy images, we compared the catalytic activities of HGORs and graphene by measuring the rate of oxidation of thiophenol using high-resolution photoemission spectroscopy (HRPES). In addition, we also assessed in 4-chlorophenol degradation and the OH radical formation with a benzoic acid to confirm the possibility for photocatalytic activities of HGORs. As a result, we confirmed that HGORs, which has an increased active site due to its three-dimensional structure formed by the reaction of graphene with hydrogen, can act as an effective catalyst. In addition, we could also realize the possibility of optical applicability by observing the 0.13 eV of band gap opening of HGORs.

Insight into the reaction mechanism of graphene oxide with oxidative free radical

Graphene oxide(GO), as an important derivative of graphene, could be considered as a super aromatic molecule decorated with a range of reactive oxygen-containing groups on its surface, which endows graphene high reactivity with other molecules. In our previous work, we demonstrated that GO sheets were cut into small pieces(graphene quantum dots, GQDs) by oxidative free radicals(hydroxyl radical HO• or oxygen radical [O]) under UV irradiation. It is notable that reactions involving free radicals are influenced by reaction conditions pronouncedly. However, researches on details about reactions of GO with free radicals have not been reported thus far. In this work, the effects of different factors on the photo-Fenton reaction of GO were studied. It is demonstrated that the reaction rate is closely related to the concentration of free radicals. It is speculated that through the optimization of reaction conditions, the reaction of graphene with free radicals could carry out efficiently for further applications.

Fluorinated graphenes as advanced biosensors - effect of fluorine coverage on electron transfer properties and adsorption of biomolecules.

Graphene derivatives are promising materials for the electrochemical sensing of diverse biomolecules and development of new biosensors owing to their improved electron transfer kinetics compared to pristine graphene. Here, we report complex electrochemical behavior and electrocatalytic performance of variously fluorinated graphene derivatives prepared by reaction of graphene with a nitrogen-fluorine mixture at 2 bars pressure. The fluorine content was simply controlled by varying the reaction time and temperature. The studies revealed that electron transfer kinetics and electrocatalytic activity of CFx strongly depend on the degree of fluorination. The versatility of fluorinated graphene as a biosensor platform was demonstrated by cyclic voltammetry for different biomolecules essential in physiological processes, i.e. NADH, ascorbic acid and dopamine. Importantly, the highest electrochemical performance, even higher than pristine graphene, was obtained for fluorinated graphene with the lowest fluorine content (CF0.084) due to its high conductivity and enhanced adsorption properties combining π-π stacking interaction with graphene regions with hydrogen-bonding interaction with fluorine atoms.

Wet-transfer of CVD-grown graphene onto sulfur-protected W(110)

Abstract Graphene, grown by chemical vapor deposition, is transferred onto W(110) surface with a protective sulfur layer. Sulfur was adsorbed on the W(110) surface in ultrahigh vacuum (UHV) by reaction with H2S at 1 × 10− 8 Torr at 800 °C. Low-energy electron diffraction and scanning tunneling microscopy (STM) measurements show that an ordered sulfur adsorbate layer is formed on W(110) with a 1 × 5 superstructure. The monolayer of sulfur subsequently protects the W(110) surface from oxidation during wet-transfer of CVD-grown graphene. After the graphene transfer, the sample is re-introduced to UHV and characterized by STM, Auger electron spectroscopy, x-ray and ultraviolet photoemission spectroscopy. The adsorbed sulfur layer prevents carbide formation, by reaction of graphene with tungsten, to annealing temperatures of at least ~ 750 °C in vacuum. Finally, photoemission measurements of the graphene/S/W(110) interface indicates p-type doping of graphene due to charge transfer at the interface as a consequence of the high work function of the W(110)-S substrate.

Chemistry at the Dirac Point of Graphene: Diels-Alder Approach to Reversible Band Gap Engineering and High Mobility Graphene Devices

ABSTRACTThe Diels-Alder (DA) pericyclic chemistry is one of the most powerful reactions in synthetic chemistry. We have recently shown that the unique zero-band-gap electronic structure of graphene at the Dirac point facilitates the band-gap-dependent DA reaction of graphene, although graphene is the thermochemical reference for carbon. We have shown that in the DA reactions, graphene can function either as a diene or a dienophile (dual nature). Such DA functionalization of graphene when applied to graphene-FET devices allows balanced functionalization (creation of a pair of new sp3 centers or divacancies) at both A and B graphene sublattices, allowing the fabrication of high mobility DA-functionalized single-layer graphene devices (DA-SLG) with acceptable on/off ratio. The chemistry is thermally reversible via retro-DA chemistry, thus allowing reversible engineering of graphene devices.

Nuclear spin Hall and Klein tunneling effects during oxidation with electric and magnetic field inductions in graphene

The recent observation of the explosive oxidation of graphene with enhancement for decreasing temperature and the requirements for synchronizing oxidants for collective oxidation-reduction (redox) reactions presented a chemical scenario for the thermal harvesting by the magnetic spin Hall Effect. More experimental data are presented to demonstrate such spin Hall Effect by determining the influence of spins of so-called spectator fermionic cations. Furthermore, the so-called spectator bosonic cations are discovered to cause a Klein tunneling effect during the redox reaction of graphene. The Na(+) and K(+), fermionic cations and the Mg(2+) and Ca(2+), bosonic cations were observed and compared under a variety of experimental conditions: adiabatic reactions with initial temperatures (18-22 °C); reactions toward infinite dilution; isothermal reactions under nonadiabatic conditions at low temperature of 18 °C; reactions under paramagnetic O(2) or diamagnetic N(2) atmospheres of different permeabilities; reactions in applied and no applied external magnetic field; and reactions toward excess concentrations of common and uncommon Na(+) and Mg(2+) cations. The observed reaction kinetics and dynamics under these various, diverse conditions are consistent with the spin Hall mechanism, energy harvesting and short time violation of Second Law of Thermodynamics for redox reactions of graphene by the Na(+)K(+) mixture and are consistent with the Klein tunnel mechanism for the redox reactions of graphene by the Mg(2+)Ca(2+) mixture. Mixed spin Hall and Klein tunnel mechanisms are discovered to slow and modulate explosive redox reactions. Such spin Hall Effect also gives explanation of recent tunneling of electrons through boron nitride.