Pan et al. Nanoscale Research Letters 2011, 6:97 http://www.nanoscalereslett.com/content/6/1/97 N A N O E X P R E S S Open Access Metal-functionalized single-walled graphitic carbon nitride nanotubes: a first-principles study on magnetic property Hui Pan1*, Yong-Wei Zhang1, Vivek B Shenoy2, Huajian Gao2 Abstract The magnetic properties of metal-functionalized graphitic carbon nitride nanotubes were investigated based on first-principles calculations. The graphitic carbon nitride nanotube can be either ferromagnetic or antiferromagnetic by functionalizing with different metal atoms. The W- and Ti-functionalized nanotubes are ferromagnetic, which are attributed to carrier-mediated interactions because of the coupling between the spin-polarized d and p electrons and the formation of the impurity bands close to the band edges. However, Cr-, Mn-, Co-, and Ni-functionalized nanotubes are antiferromagnetic because of the anti-alignment of the magnetic moments between neighboring metal atoms. The functionalized nanotubes may be used in spintronics and hydrogen storage. Introduction Applications of spin-based devices are so far limited to information storage, and most of the spin-related mate- rials and devices still rely primarily on the spontaneous ordering of spins in the form of different types of mag- netic materials. This situation is expected to change with successful development of spin-based electronics, or spintronics, the new kind of electronics that seeks to exploit, in addition to the charge degree of freedom, the spin of the carriers [1]. The primary requirement for spintronics is to have a system that can generate a cur- rent of spin-polarized electrons. To enable a host of new device applications, it is necessary to develop mate- rials which should have (a) high Curie temperature, (b) controllable carrier density and mobility, and (c) easily magnetic doping [2]. Ideally, a semiconductor can be made magnetic by including ions that have a net spin into a semiconductor [3]. The doped semiconductors are referred as dilute magnetic semiconductors (DMSs) because only a small amount of magnetic ions is required to make the semiconductor magnetic. In recent years, considerable efforts have been devoted to the study of DMS materials. The search for DMSs has been focused on cation substitution of semiconductors with * Correspondence: panh@ihpc.a-star.edu.sg 1Institute of High Performance Computing, 1 Fusionopolis Way, 138632, Singapore Full list of author information is available at the end of the article transition metal (TM) elements, where the Curie tem- perature of the doped semiconductor can be below or above room temperature, depending on the host materi- als, carrier concentration, and doping elements [4-11]. However, the clustering of transition metal and the for- mation of secondary phases in DMSs are obstacles to their practical applications in spintronics [12]. Although the cation substitution with two different elements and anion substitution may overcome the clustering issue [7,13-15], the observation of ferromagnetism in undoped semiconductor nanoparticles suggested that doping- induced defects also contributed to the magnetic moment [16-19]. Therefore, for the practical application of DMSs, a crucial prerequisite is to overcome the clus- tering of TM in DMS and control the magnetic prop- erty, which may be solved by cation-anion codoping method [20]. Carbon nitride has attracted considerable interest and has been widely used in electronic devices, thermolumi- nescence dosimeter, humidity sensor, coatings, and cata- lyst because of their interesting electronic, chemical, mechanical, and tribological properties [21-26]. Carbon nitride can exist in various phases not only depending on the C to N ratio, but also on atomic arrangements [21]. Among these phases, the graphitic carbon nitride (g-C3N4), a heptazine-based form, is regarded to be the most stable structure, and can be realized by thermo- condensation of C/N/H-containing precursors [22]. © 2011 Pan et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.