Reversible Formation of Ammonium Persulfate/Sulfuric Acid Graphite Intercalation Compounds and Their Peculiar Raman Spectra
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- 作者：Ayrat M. Dimiev ; Sergei M. Bachilo ; Riichiro Saito ; James M. Tour
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：September 25, 2012
- 年：2012
- 卷：6
- 期：9
- 页码：7842-7849
- 全文大小：522K
- 年卷期：v.6,no.9(September 25, 2012)
- ISSN：1936-086X
文摘
Graphite intercalation compounds (GICs) can be considered stacks of individual doped graphene layers. Here we demonstrate a reversible formation of sulfuric acid-based GICs using ammonium persulfate as the chemical oxidizing agent. No covalent chemical oxidation leading to the formation of graphite oxide occurs, which inevitably happens when other compounds such as potassium permanganate are used to charge carbon layers. The resulting acid/persulfate-induced stage-1 and stage-2 GICs are characterized by suppression of the 2D band in the Raman spectra and by unusually strong enhancement of the G band. The G band is selectively enhanced at different doping levels with different excitations. These observations are in line with recent reports for chemically doped and gate-modulated graphene and support newly proposed theories of Raman processes. At the same time GICs have some advantageous differences over graphene, which are demonstrated in this report. Our experimental observations, along with earlier reported data, suggest that at high doping levels the G band cannot be used as the reference peak for normalizing Raman spectra, which is a commonly used practice today. A Fermi energy shift of 1.20鈥?.25 eV and 1.0 eV was estimated for the stage-1 and stage-2 GICs, respectively, from the Raman and optical spectroscopy data.