Editorial pubs.acs.org/cm
Layer-by-Layer Growth of Graphene Oxide-Based Films for Electronics Applications in 1999: Early Leaders Tom Mallouk and Nina Kovtyukhova: Chemistry of Materials’ 1k Club e are pleased to start the first issue of 2015 with the next addition to our 1k Club series, which highlights Chemistry of Materials publications that have been cited 1000 times or more. In 1999, Tom Mallouk and Nina Kovtyukhova (Figure 1) published a piece of original research that was
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CM: At what stage of your academic career were you when submitted these manuscripts to Chemistry of Materials? Who were the other authors on the papers, and at what stages were they? Where are they now? M&K: Both of us were mid-career at the time this paper was published. Nina Kovtyukhova had recently moved from the National Academy of Sciences of the Ukraine to Penn State. Tom Mallouk had been in academics for 14 years. Co-authors Patti Ollivier and Ben Martin were graduate students who are now at DuPont and Texas State University, respectively. Sergey Chizhik is now First Deputy Chairman of National Academy of Sciences of Belarus. Eugenia Buzaneva was a professor of semiconductor physics (now retired),and Alexandr Gorchiskiy was a professor of physics (deceased). CM: Given the high citation record of this article, a significant amount of research has been impacted by your work over the years. Where did you think the field was headed when you wrote the paper? In your opinion, how has this particular research field evolved ever since? M&K: We were (and still are) interested in the multifunctional properties of layered inorganic materials and in developing them as building blocks for composite materials. At the time we did not foresee the importance of graphene as an electronic material, but we did have a good idea (from our concurrent work on fuel cell catalysis) that it would be an interesting material for electrochemical energy conversion. Since then, research on layered materials has grown in ways we could not have predicted. The fantastic work of Geim, Novoselov,3 and others on the physical properties of graphene sheets of course sparked a lot of interest in the field. In fact, our paper was hardly cited at all until they showed what an interesting material you could make by peeling apart graphite. Many groups have since used our method to make single-sheet colloids of graphite oxide (GO), which can be reduced to sheets of reduced graphene oxide (rGO). rGO resembles graphene structurally and electronically, although it has a higher concentration of defects. The important difference is that it can be made in bulk quantities. It is now being very extensively researched for its applications in electronics, catalysis, separations, composites, and energy storage. CM: If you had to put your finger on it, what made this paper special? What are you most happy about when you reread this work? M&K: The chemistry of graphite oxide goes back to the French chemist Brodie, who first synthesized it in 1855. The structure, chemistry, and applications of this unique compound have been unfolding ever since. We are happy to have played a part in the development of something so interesting and useful. We were not the first group to exfoliate GO,but, thanks to
Figure 1. Newest members of the Chemistry of Materials’ 1k Club.
remarkably prescient and far ahead of its time.1 Today in 2015, we live in an era where many scientists believe that research in graphene and its derivatives, including graphene oxide (GO), is brand new, and took off with an enormous explosion of work sometime after 2000. This assumption is not entirely true, as there were important contributions that laid the groundwork for the “graphene age”. The Mallouk and Kovtyukhova publication, entitled “Layer-by-Layer Assembly of Ultrathin Composite Films from Micron-Sized Graphite Oxide Sheets and Polycations”, was submitted to Chemistry of Materials in 1998, published in 1999, and has been since cited 1512 times per Google Scholar and 1305 times per Web of Science.2 Mallouk and Kovtyukhova began their abstract with the following line: Unilamellar colloids of graphite oxide (GO) were prepared f rom natural graphite and were grown as monolayer and multilayer thin f ilms on cationic surfaces by electrostatic selfassembly. By unilamellar, they were referring to single sheets of GO, which were prepared and subsequently manipulated in a variety of ways. They incorporated the GO sheets into functional layers of materials via layer-by-layer assembly (LbL), using the net negative charge of the GO sheets to interact in an attractive fashion with positively charged polymers. Not only does this paper represent an early landmark in the graphene roadmap, but it also embodies an important advance in the area of controlled LbL growth of films. A few images from the manuscript are shown in Figure 2. We (CM) asked Mallouk and Kovtyukhova (M&K) a few questions about this paper, to get insight into what made this paper special and what attracted them to these materials, from the beginning. © 2015 American Chemical Society
Published: January 13, 2015 1
dx.doi.org/10.1021/cm504539p | Chem. Mater. 2015, 27, 1−2
Chemistry of Materials
Editorial
Figure 2. Ahead of their time. Three images taken from ref 1, “Layer-by-Layer Assembly of Ultrathin Composite Films from Micron-Sized Graphite Oxide Sheets and Polycations”. Top left: AFM image of sheets of graphene oxide (GO). Top right: Current−voltage plot of GO/polycation layers on an indium tin oxide (ITO) electrode. Bottom right: Ellipsometry data showing control over the LbL process to form layers of GO and polycations of desired thicknesses. Reproduced with permission. Copyright 1999 American Chemical Society.
advances in microscopy techniques, we could show that it was possible to manipulate individual graphene oxide monolayers. CM: What’s your advice to young scientists trying to discover the next breakthrough in material science? M&K: Do not be a pack follower; work on a material that you think is interesting, and do good science with it. It is even better if it is a material that nobody else particularly cares about at the time. Someday, somebody somewhere will figure out why your work was really important.
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Jillian M. Buriak, Editor-in-Chief Carlos Toro, Managing Editor AUTHOR INFORMATION
Notes
Views expressed in this editorial are those of the author and not necessarily the views of the ACS.
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REFERENCES
(1) Kovtyukhova, N. I.; Olivier, P. J.; Martin, B. R.; Mallouk, T. E.; Chizhik, S. A.; Buzaneva, E. V.; Gorchinskiy, A. D. Chem. Mater. 1999, 11, 771−778. (2) Data generated December 9, 2014. (3) Winners of the Nobel Prize in Physics, 2010.
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dx.doi.org/10.1021/cm504539p | Chem. Mater. 2015, 27, 1−2
