Electrical dan magnetic properties of graphene-derivatives materials are strongly influenced by their physical properties. Here we report a study on physical properties of reduced graphene oxide (rGO) prepared from two different raw materials, namely coconut shell (rGO-s) and graphite mineral (rGO-c, produced by Graphenea Inc.). rGO-s was prepared by carbonization method followed by mechanical exfoliation. While both samples have the same density of about 1.9 g/cm 3 , rGO-c has more porous compared to rGO-s. Specific surface area in rGO-c was also obtained much larger than that of rGO-s. Examinations on particle size and surface morphology show that rGO-c has homogenous particles which consist of transparent thin sheets, while rGO-s has rather heterogenous particles that look like dens stacked sheets. The presence of C and O was confirmed at the observed morphology. The difference in physical features was found to influence the obtained electrical conductivity of the samples. rGO-c has higher conductivity than rGO-s. Estimation on gap energy (Eg) indicates that rGO-c and rGO-s have Eg in the range of semiconducting materials. The study provides a better understanding on physical properties of coconut shell-derived rGO to further revise synthesis method to improve quality of the obtained rGO.
Graphene has become an exciting material to be studied because of its unique properties. One of the interesting phenomena is the change of its electronic and magnetic properties due to impurities adsorption. By using the spin-polarized density functional theory (DFT) method, we simulate single vacancy graphene with the adsorption of hydrogen atoms around the dangling bond to determine the electronic and magnetic properties of the material. In this study, we use a 4×4×1 supercell of single-layered graphene. We have four models, i.e., single vacancy graphene, and graphene with hydrogen adsorption in the dangling bond site with the atom’s variation number (H = 1, 2, 3 atoms). Our results show that the modifications of graphene in the form of single vacancy and hydrogen adsorptions makes the graphene material metal, except for the SV+2H model which shows a semiconductor characteristic. The presence of a single vacancy affects the magnetic moment of the modeled graphene layer. A single vacancy on the modeled graphene layer results in a total magnetic moment of 0.69 µB/cell. In the single vacancy graphene with three hydrogen atoms adsorption, we acquire the total magnetic moment of 0.15 µB/cell. This study shows that defects in the forms of vacancies and adsorption of hydrogen atoms can initiate magnetism on graphene. These results open a way of using graphene to create nanomagnetic devices.
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