Comparative Study on Magnetism of Reduced Graphene Oxide (rGO) Prepared from Coconut Shells and the Commercial Product

Abstract

Magnetism of reduced graphene oxide/rGO prepared by a green synthesis method from coconut shells (rGO-s) and the commercial product (rGO-c, ®Graphenea) have been investigated. Similar magnetic feature of a weak ferromagnetism concomitant with diamagnetic nature was observed in both samples. At 300 K, the saturation magnetization (MS) of rGO-s is approximately 14×10-3 emu/g, which is about 3 times of that observed in rGO-c (~5×10-3 emu/g). The noticeable difference in the MS is suggested due to the different concentration of oxygen-functional groups and other defects presented in the rGO sheets. The samples have similar structure and contains similar functional groups, yet rGO-s contains higher concentration of oxygen-functional groups and defects than rGO-c. A paramagnetic behavior was also indicated at low temperature. This study supports an indication of the defect-induced-magnetism in rGO and confirms that various magnetic features, such as ferromagnetic, diamagnetic and paramagnetic, can coexist in rGO.

Physical Properties Comparison of rGO-like phase prepared from Coconut Shell and the Commercial Product

“…Spectra of Fourier Transform Infrared (FTIR) also confirmed that both samples have similar functional groups of C=C, C=O, C-O, C-H, and O-H. However, qualitative analysis of the spectra suggested that rGO-s has a higher percentage of oxygen functionality, which is twice as large as that of rGO-c [23].…”

“…Analyses on phase and functional groups presented in the samples have been reported in [22,23]. Two broad peaks at 2θ of about 24 • and 43 • were observed in XRD patterns of the samples, indicating the presence of the rGO-like phase.…”

“…The physical features of the samples influence their electrical and magnetic properties. Our previous studies reported that magnetization of the rGO-like phase synthesized from coconut shell strongly depends on defects [22,23]. The magnetization enhances when the concentration of defect increases, and this can be tuned by controlling temperature applied in the thermal reduction process [22].…”

“…The magnetization enhances when the concentration of defect increases, and this can be tuned by controlling temperature applied in the thermal reduction process [22]. The saturation magnetization of rGO-s is larger than that in rGO-c as rGO-s has more defects compared with rGO-c [23]. In this case, a contribution from magnetic impurities has been subtracted.…”

“…Chemical and thermal reduction processes were applied to form rGO from graphite oxide [2,3]. The synthesized rGO (rGO-c), on the other hand, was prepared from biomass of coconut shell by the carbonization method [21,23]. The old coconut shell was cleaned by removing husks adhered on its surface.…”