Testing Graphene Films Produced Through Electrochemical Exfoliation Using Sulfate Electrolytes

Graphene is one of the most commonly researched materials in nanoscience and finding a cheap and efficient method to manufacture it is highly desirable because of its incredible properties. Electrochemical exfoliation involves splitting graphite into graphene by soaking the foil in an electrolyte solution and then providing an electric current. This paper evaluates the extent to which the sulphate electrolyte used in the electrochemical exfoliation process affects the electrical resistance of films created using flakes generated from the reaction. Using the method and conducting an ANOVA test with Tukey HSD Post-Hoc test on the resultant data provides significant and varied results when concerning the electrolyte variety. This implies that changing the quality and speed of the electrolyte reaction has a definitive effect on the resistance of composite films created out of graphene flakes produced from the reaction.

Influence of C=O groups on the optical extinction coefficient of graphene exfoliated in liquid phase

LiLiquid phase exfoliation of graphite is currently one of the most promising graphene production methods at large scale. For this reason, an accurate calculation of the concentration in graphene dispersions is important for standardization and commercialization. Here, graphene dispersions, at high concentrations, were produced by electrochemical exfoliation. Furthermore, a cleaner methodology to obtain graphene oxide by electrochemical exfoliation at high acid concentrations was implemented. The absorption coefficient for graphene and graphene oxide was determined in the optical range ($\alpha_{660nm}=$ 1414 ($\pm$3\%) mL mg$^{-1}$ m$^{-1}$ and $\alpha_{660nm}=$ 648 ($\pm$ 7\%) mL mg$^{-1}$ m$^{-1}$, respectively) with an exponential dependence with the wavelength. The difference in $\alpha$ for both materials is attributed to an increased presence of C=O groups as evidenced by FTIR, UV-vis and Raman spectroscopy, as well as, in the calculation of the opical extinction coefficient and optical band-gap via Tauc-plots.

The scalable production of high-quality nanographite by organic radical-assisted electrochemical exfoliation.

One of the promising ways to produce graphene is the technology of graphite splitting or exfoliation, both by physical or mechanical and chemical, including electrochemical methods. The product of electro exfoliation is nanographite, which is transformed into multigraphene at the subsequent stage of liquid-phase mechanical and ultrasonic disintegration. This approach demonstrates a successful method of obtaining multigraphene from available graphite raw materials. Since, already at a potential of 1.23V, during the electrolysis of water on a graphite anode, the hydroxyl anion is discharged with the formation of a very active hydroxyl radical oxidizer, it is not surprising that when the graphite electro exfoliation process is overvolted at 10V, graphite oxidation products are formed. In order to control the defectiveness of the graphene lattice by oxidation products, we carried out processes of graphite exfoliation in the presence of both a number of reducing agents ascorbic acid, sodium borohydride, hydrazine hydrate, and in the presence of industrial antioxidants radical traps (2,2,6,6-tetramethylpiperidine-1-il)oxyl (TEMPO), (2,2,6,6-tetramethyl-4 oxo-piperidine-1-yl)oxyl (IPON), a mixture of 5,8,9-bis isomers[(2,2,6,6-tetramethyl - 4 oxo-piperidine-1-yl)]-{5,8,9-[1,1’- bi(cyclopentylidene)]-2,2’,4,4’- tetraene}(YARSIM-0215). It should be noted, that the best result of preventing the oxidation of nanographite in electro exfoliation technology in our studies is the ratio of carbon to oxygen (C/O) about 69.

Improvement of Porous GaN-Based UV Photodetector with Graphene Cladding

This work presents the role of graphene in improving the performance of a porous GaN-based UV photodetector. The porous GaN-based photodetector, with a mean pore diameter of 35 nm, possessed higher UV sensitivity, about 95% better compared to that of the as-received (non-porous) photodetector. In addition, it exhibits a lower magnitude of leakage current at dark ambient, about 70.9 μA, compared to that of the as-received photodetector with 13.7 mA. However, it is also highly resistive in nature due to the corresponding electrochemical process selectively dissolute doped regions. Herein, two types of graphene, derived from CVD and the electrochemical exfoliation (EC) process, were cladded onto the porous GaN region. The formation of a graphene/porous GaN interface, as evident from the decrease in average distance between defects as determined from Raman spectroscopy, infers better charge accumulation and conductance, which significantly improved UV sensing. While the leakage current shows little improvement, the UV sensitivity was greatly enhanced, by about 460% and 420% for CVD and EC cladded samples. The slight difference between types of graphene was attributed to the coverage area on porous GaN, where CVD-grown graphene tends to be continuous while EC-graphene relies on aggregation to form films.