This journal is c The Royal Society of Chemistry 2011 Chem. Commun., 2011, 47, 5223–5225 5223 Cite this: Chem. Commun., 2011, 47, 5223–5225 Steaming multiwalled carbon nanotubes via acid vapour for controllable nanoengineering and the fabrication of carbon nanoflutesw Jun Ming, abc Yingqiang Wu, abc Yancun Yu ab and Fengyu Zhao* ab Received 26th January 2011, Accepted 10th March 2011 DOI: 10.1039/c1cc10525f A new concept of steaming multiwalled carbon nanotubes (MWCNTs) via acid vapour was presented for controllable nanoengineering of the MWCNTs. This method is more simple, effective, precisely-controllable and environmentally-friendly compared to traditional ones. Moreover, novel porous carbon nanotubes, named carbon nanoflutes, were fabricated based on this strategy. The production of carbon nanotubes (CNTs) has already been done on an industrial scale, but their applications are strongly limited by a series of prerequisite treatments (e.g., impurity removal, surface functionalization, end-open and short-cut), which are difficult to implement on a large-scale by traditional techniques. To date, the oxidation of CNTs in a solution of acid or strong oxidant is the main and most adopted method, 1 and it has become a requisite starting step for the research and application of CNTs, such as the preparation of CNT-based composite materials, 2 catalyst support, 3 and biological medicine vehicles 4 etc. However, several inevitable, fatal disadvantages exist with such solution methods, if they only make the CNTs contact with the liquid. For example, (i) the inner surface of the CNTs is hard to purify and functionalize because the solution cannot penetrate the whole nanotube due to the strong capillary force of liquid; (ii) an excess amount of oxidant agent (e.g., HNO 3 ) is often required for immersing and refluxing the CNTs, which not only pollutes the environment but also burdens the post treatment; 5 (iii) the washing and separation of functionalized CNTs (f-CNTs) from oxidant solution, particularly short-cut ones, is very difficult due to the fact that f-CNTs disperse in solution as a result of increased functional groups on the f-CNTs surface. The oxidant solution that remained in the orifice was also difficult to remove through tedious washing. Moreover, manipulation such as refluxing the CNTs in a large amount of strong oxidant solution under a high temperature for a long time (several hours at least) 6 could not proceed safely and on a large scale in industrial applications. Alternatively, the gas-oxidation of CNTs in an oxidizing atmosphere (e.g., O 2 , 7 CO 2 , 8 Cl 2 +H 2 O+Ar 9 ) at a high temperature is a relatively simple method for removing impurities, end-open, short-cut; unfortunately, the suitable atmosphere and temperature are often difficult to select and control, and moreover the important surface functionalization could not be accomplished. Besides, the removal of impurities such as carbonaceous materials and metal catalysts is often hard to realize simultaneously in such gas-oxidation methods. Thus, the absence of a reliable, large-volume production capacity, simple and efficient method for treating CNTs has principally restricted the investigation and commercial applications of CNTs. Herein, we report a novel method of steaming MWCNTs via acid vapor in a self-designed steamer for effectively nanoengineering MWCNTs. With this strategy, not only could all the necessary nanoengineering of MWCNTs be achieved and precisely controlled , but also the disadvantages that exist in traditional methods are completely overcome. The necessary equipment and treatment procedures are provided in supplementary information (Fig. S1w). Fig. S1Aw is a self-designed glass steamer with a special SiO 2 porous griddle, on which the MWCNTs were loaded to completely avoid contact with the liquid. The glass steamer was then placed in a Teflon vessel (Fig. S1Bw), at the bottom of which a little amount of volatile acid was loaded, such as HNO 3 (65–68 wt%). Generally the Teflon vessel was sealed in an autoclave and then heated in an oven for steaming (Fig. S1C–Ew). At an elevated temperature, the HNO 3 was volatized to react with the MWCNTs quickly, including the inner surface of MWCNTs since gas penetration is much faster and easier compared to a liquid. After steaming treatment, the autoclave was cooled to room temperature and then the washing and separation could be performed in the steamer quickly and simply because the porous griddle further acts as an effective filter (Fig. S1Fw), enabling the separation of the functionalized MWCNTs (f-MWCNTs) more easily and completely without long-time/high-speed centrifugation 6 and any losses as in the traditional methods. After washing with distilled water and ethanol, the f-MWCNTs were dried in an oven and the formed f-MWCNTs cakes could be collected easily. a State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China b Laboratory of Green Chemistry and Process, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China. E-mail: zhaofy@ciac.jl.cn; Fax: +86-431-85262410; Tel: +86-431-85262410 c University of the Chinese Academy of Sciences, Beijing 100049, P. R. China w Electronic supplementary information (ESI) available: BET-analysis of p-CNTs and carbon nanoflutes. See DOI: 10.1039/c1cc10525f ChemComm Dynamic Article Links www.rsc.org/chemcomm COMMUNICATION Downloaded by Changchun Institute of Applied Chemistry, CAS on 24 May 2011 Published on 22 March 2011 on http://pubs.rsc.org | doi:10.1039/C1CC10525F View Online