Characterization of graphene oxide reduced through chemical and biological processes

Statistical analysis of the reduction process of graphene oxide probed by Raman spectroscopy mapping

We propose a method for monitoring the large-scale homogeneity of the reduction process of graphene oxide. For this purpose, a Raman mapping technique is employed to probe the evolution of the phonon properties of two different graphene oxide (GO) thin films upon controllable thermal reduction. The reduction of GO is reflected by the upshift of the statistical distribution of the relative intensity ratio of the G and D peaks (I _D/I _G) of the Raman spectra and is consistent with the ratio obtained for chemically reduced GO. In addition, the shifts of the position distributions of the main Raman modes ([Formula: see text], [Formula: see text]) and their cross-correlation with the I _D/I _G ratio provides evidence of a change of the doping level, demonstrating the influence of reduction processes on GO films.

Superior Catalytic Activity of Electrochemically Reduced Graphene Oxide Supported Iron Phthalocyanines toward Oxygen Reduction Reaction

Structure and surface properties of supporting materials are of great importance for the catalytic performance of the catalysts. Herein, we prepared the iron phthalocyanine (FePc) functionalized electrochemically reduced graphene oxide (ERGO) by the electrochemical reduction of FePc/GO. The resultant FePc/ERGO exhibits higher catalytic activity toward ORR than that of FePc/graphene. More importantly, the onset potential for ORR at FePc/ERGO positively shifts by 45 mV compared with commercial Pt/C in alkaline media. Besides, FePc/ERGO displays enhanced durability and selectivity toward ORR. The superior catalytic performance of FePc/ERGO for ORR are ascribed to the self-supported structure of ERGO, uniformly morphology and size of FePc nanoparticles.

Exoelectrogens Leading to Precise Reduction of Graphene Oxide by Flexibly Switching Their Environment during Respiration

Reduced graphene oxide (RGO) has been prepared by a simple, cost-effective, and green route. In this work, graphene oxide (GO) has been reduced using Gram-negative facultative anaerobe S. dysenteriae, having exogenic properties of electron transfer via electron shuttling. Apparently, different concentrations of GO were successfully reduced with almost complete mass recovery. An effective role of lipopolysaccharide has been observed while comparing RGO reduced by S. dysenteriae and S. aureus. It was observed that the absence of lipopolysaccharide in Gram-positive S. aureus leads to a disrupted cell wall and that S.aureus could not survive in the presence of GO, leading to poor and inefficient reduction of GO, as shown in our results. However, S. dysenteriae having an outer lipopolysaccharide layer on its cell membrane reduced GO efficiently and the reduction process was extracellular for it. RGO prepared in our work has been characterized by X-ray diffraction, ζ potential, X-ray photoelectron spectroscopy, and Raman spectroscopy techniques, and the results were found to be in good agreement with those of chemically reduced GO. As agglomeration of RGO is the major issue to overcome while chemically reducing GO, we observed that RGO prepared by a bacterial route in our work has ζ potential value of -26.62 mV, good enough to avoid restacking of RGO. The role of exoelectrogens in electron transfer in the extracellular space has been depicted. Toxin released extracellularly during the process paves the way for reduction of GO due to its affinity towards oxygen.