A novel route for the synthesis of nanotubes and fullerene-like nanostructures of molybdenum disulfide Pravas Kumar Panigrahi, Amita Pathak * Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India 1. Introduction For the last few decades, there has been considerable interest in the transition metal chalcogenide layered compounds from both a theoretical and experimental point of view [1–4]. Molybdenum disulfide (MoS 2 ), one of the important layered transition metal chalcogenides, has drawn attention of many researchers because of its exciting structural and optical properties. MoS 2 has a sandwich- like layered structure, where each layer is constructed by covalently bonded groups of three planes; one Mo layer is placed between two sulfur layers [5]. This unique structure leads to a large number of dangling bonds on the periphery of the layers, rendering MoS 2 with excellent catalytic property for hydrogenation and hydrodesulfurization reactions [6,7]. MoS 2 can also be used as solid state lubricant [8–10] for tribological applications at high temperatures and vacuum environments, where the use of traditional liquid lubricants becomes ineffective or cannot be tolerated. In addition, it can be applied as electrode material in solid state lithium ion batteries [11,12] due to its ability to intercalate with lithium ions. These useful properties of MoS 2 led to the development of a wide range of methods, such as gas-phase reaction [4,13,14], thermal decomposition [15], hydrothermal reaction [16,17], soft solution based reaction [18] and sonochemical reaction [19] for its synthesis with different curved and one-dimensional nanostruc- tures (such as nanotubes, nanorods, nanowires, nanospheres, inorganic fullerene (IF)-like structures). However, it still remains a challenge to prepare nanostructured MoS 2 in a simple, rapid and cost effective manner by developing new methods or modifying the existing ones. In this context, microwave-assisted route has been considered as one of the leading synthesis approaches. In this method, heating is caused due to the direct interaction between microwaves and polar molecules, which makes it simple, fast and economic in comparison to conventional ones [20]. Hence, this method has found applications in various fields including the preparation of nanocrystalline particles of a wide range of metal chalcogenides [21–23] during the last decade. Despite this, not many reports are available on the synthesis of MoS 2 through microwave-assisted method. Previously, Vollath and Szabo [24,25] have reported the synthesis of MoS 2 and WS 2 in a microwave plasma through reactions of their respective metal carbonyls with H 2 S. Later, Ouerfelli et al. utilized solid state microwave-assisted synthetic method to prepare thin films of MoS 2 and WS 2 by using thin foils of the respective metals as metal source and sulfur powders as sulfur source [26]. As far as our literature survey is concerned, no report has been found for the synthesis of MoS 2 through solution-based microwave-assisted method till date. Therefore, in this work, a solution-based microwave-assisted method has been described for the synthesis of fullerene-like and nanotubes of MoS 2 . The method involved the use of ammonium molybdate as metal source and elemental sulfur dissolved in Materials Research Bulletin 46 (2011) 2240–2246 A R T I C L E I N F O Article history: Received 25 April 2011 Received in revised form 31 August 2011 Accepted 4 September 2011 Available online 10 September 2011 Keywords: A. Layered compounds B. Chemical synthesis C. X-ray diffraction C. Electron microscopy A B S T R A C T The paper described the synthesis of nanotubes and fullerene-like nanostructures of MoS 2 through a technically simple, rapid, and energy-efficient microwave-assisted synthesis technique, which involved the use of elemental sulfur dissolved in a mixture of monoethanolamine and hydrazine hydrate as the sulfide source. The microwave induced reaction between the molybdate with sulfide ions, in the presence of hydrazine hydrate in the reaction medium, resulted in the formation of gray colored powders of amorphous MoS 2 . The as-obtained powders were calcined at 600 8C for 2 h and characterized by different techniques. HRTEM analysis of the calcined samples indicated the formation of fullerene-like MoS 2 structures when the starting solution mixture was irradiated with microwave for a period of 200 s, while on 600 s of irradiation of the same revealed the formation of folded sheets like MoS 2 nanotubes. BET surface areas of the calcined samples have been measured and a plausible reaction mechanism for the formation of nanotubes and fullerene-like nanostructures of MoS 2 has been proposed. ß 2011 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +91 3222 283312; fax: +91 3222 255303. E-mail addresses: pravas.iit@gmail.com (P.K. Panigrahi), ami@chem.iitkgp.ernet.in (A. Pathak). Contents lists available at SciVerse ScienceDirect Materials Research Bulletin jo u rn al h om ep age: ww w.els evier.c o m/lo c ate/mat res b u 0025-5408/$ – see front matter ß 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2011.09.003