Scalable enhancement of graphene oxide properties by thermally driven phase transformation

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Chemical functionalization of graphene is promising for a variety of next-generation technologies. Although graphene oxide (GO) is a versatile material in this direction, its use is limited by the production of metastable, chemically inhomogeneous and spatially disordered GO structures under current synthetic protocols, which results in poor optoelectronic properties. Here, we present a mild thermal annealing procedure, with no chemical treatments involved, to manipulate as-synthesized GO on a large scale to enhance sheet properties with the oxygen content preserved. Using experiments supported by atomistic calculations, we demonstrate that GO structures undergo a phase transformation into prominent oxidized and graphitic domains by temperature-driven oxygen diffusion. Consequently, as-synthesized GO that absorbs mainly in the ultraviolet region becomes strongly absorbing in the visible region, photoluminescence is blue shifted and electronic conductivity increases by up to four orders of magnitude. Our thermal processing method offers a suitable way to tune and enhance the properties of GO, which creates opportunities for various applications.

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Figure 1: Improvement in the optical properties of annealed GO structures.
Figure 2: Enhanced electrical properties of annealed GO thin films.
Figure 3: TGA, FTIR and PL spectra of annealed GO structures.
Figure 4: Direct evidence of phase separation in annealed GO structures.
Figure 5: Favourable energetics of phase separation predicted by atomistic modelling.


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The authors dedicate this paper to the memory of S. Collier for his caring service to the Massachusetts Institute of Technology (MIT) community and for his sacrifice in defending the MIT campus in the line of duty. P.V.K. is grateful to Eni for financial support via the Solar Frontiers Program at MIT. P.V.K. and J.C.G. thank the Texas Advanced Computer Sector Stampede system for computational resources. This study was supported in part by the Institute for Collaborative Biotechnologies through grant W911NF-09-0001 from the US Army Research Office. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231. N.M.B. and P.V.K. are grateful for the use of the Materials Analysis Shared Experimental Facilities at the Center for Materials Science and Engineering at MIT, and thank T. McClure, E. Shaw, T. Kucharski, J. Qi, G. Zhang, J. Ohmura and A. Maurano for assistance with experiments.

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P.V.K., N.M.B., A.M.B. and J.C.G. conceived and designed the experiments, P.V.K. and N.M.B. performed the experiments, calculations and co-wrote the manuscript with input from J.C.G. and A.M.B., and S.T. and J.W. performed AES, and contributed to Raman and PL mapping.

Correspondence to Angela M. Belcher or Jeffrey C. Grossman.

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Kumar, P., Bardhan, N., Tongay, S. et al. Scalable enhancement of graphene oxide properties by thermally driven phase transformation. Nature Chem 6, 151–158 (2014) doi:10.1038/nchem.1820

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