Article pubs.acs.org/JPCC
Tunable Electronic and Magnetic Properties of Transition MetalCyclopentadiene Sandwich Molecule Wires Functionalized Narrow Single Wall Carbon Nanotubes Xiuyun Zhang* and Yongjun Liu Department of Physics, Yangzhou University, Yangzhou 225009, China S Supporting Information *
ABSTRACT: The structural, electronic, and magnetic properties of 1D organometallic molecule wires functionalized narrow single wall carbon nanotube, [TMCp]∞/SWCNTs (TM = Sc, V, Mn, Fe, Co, SWCNTs, (n, m) = (7,7), (10,0), (11,0)), are first studied by density functional theory calculations. In the case of the 1D [TMCp]∞ wires encapsulated in SWCNTs, the reaction between 1D [TMCp]∞ and SWCNTs are endothermic or exothermic depending on the diameters of SWCNTs, while the dimension confinement effect disappears through placing the organometallic molecular wires outside the SWCNTs. Moreover, obvious ionic bonding nature is identified in the systems by putting the 1D [TMCp]∞ wire in or outside of the SWCNTs. In contrast, stronger covalent bonding nature is found for the derivatives by desorption of one raw of hydrogen atoms in the cyclopentadiene ligands. In particular, diverse electronic and magnetic properties are introduced by the choice of SWCNTs and the functionalized 1D [TMCp]∞ wires, which allows the 1D [TMCp]∞/SWCNTs wires to function as a basic building block for potential application in electronic- and spintronic-based devices.
I. INTRODUCTION Single-walled carbon nanotubes, SWCNT(n, m)s (n, m is chiral index), constructed by rolling up a honeycomb graphene sheet, have attracted great attention due to their excellent mechanical, electronic, thermal and optic properties, which display potential application in thermal conductions, nanosemiconducting devices, detectors, field emission tubes, and energy storage and conversions.1−4 For example, the internal plane Young’s modulus of SWCNTs is up to 1.06 Tpa due to the stable sp2 hybridized C−C bonds;1 and the axial thermal conductivity is 3500 W·m−1·K−1.2 On the other hand, the electronic properties of SWCNTs are strictly defined by their atomic structures, such as a particular SWCNT with n − m = 3l (l is an integer number) shows metallic property, and the ones having n − m ≠ 3l are semiconducting.3,4 What’s more, zero magnetic moments are found for the pristine SWCNTs, which largely hinder their use in modern spintronic field. To date, various strategies have been proposed for the properties fabrications of SWCNTs: substituting carbon atoms of SWCNTs by other atoms;4−7 loading different functional groups on the surface of SWCNTs by chemical and physical adsorption,4,8−10 and encapsulating different compounds in the inner cavity.4,11−26 Recently, the filling of organometallic compounds into SWCNTs has become the extensively studied carrier doping systems,11,16−26 which, on one hand, has the advantage of slightly perturbing of the structures of both SWCNTs and organometallic molecules, on the other hand, modulating the © XXXX American Chemical Society
electronic and magnetic properties of SWCNTs without significant changing the structures of nanotubes and the encapsulated entities. Experimental and theoretical researchers investigated that the cobaltocene favors to fill the SWCNTs of one specific diameter, ∼ 0.94 nm,16 also, the smallest diameter of SWCNTs for encapsulating FeCp2 (Cp = cyclopentadiene) is proposed around 0.9 nm.17−19,23,24 Theoretically, Cao et al. found that doping SWCNTs with metallocenes exhibit n-type characteristics.23 Garcia-Suarez et al. found that the charge transfer from TMCp2 TM = (V, Cr, Mn, Fe) to SWCNTs can effectively engineer the spintronic properties.24 Similarly, Zhang et al. found that the electron transfer from FeCp2/Fe2Cp3 to SWCNT influences the transport properties.26 Besides, different magnetic behaviors are found for the ferrocene filled SWCNTs.20−22 In addition to the finite molecules,27−32 onedimensional (1D) infinite organometallic sandwich molecular wires (IOSMWs) have also been extensively extended and exhibit excellent physical and chemical properties.32−38 So, one question rises, whether we can fabricate the electronic and magnetic properties of SWCNTs under the functionalization of 1D IOSMWs? Experimentally, multilayer organometallic complexes have been successfully synthesized by laser vaporizing organometallic ligands and transition metal atoms,31 Received: June 6, 2016 Revised: August 16, 2016
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DOI: 10.1021/acs.jpcc.6b05684 J. Phys. Chem. C XXXX, XXX, XXX−XXX
Article
The Journal of Physical Chemistry C
Figure 1. Schemes of 1D IOSMW/SWCNTs heteronanostructures: (a, d) IOSMW@SWCNT; (b, e) IOSMW&SWCNT; (c, f) ISOMW&SWCNT_DH.
between 1D IOSMWs and SWCNTs.46 Furthermore, the GGA +U scheme is used for applying the on-site correlation effects among 3d electrons of TM, where the parameter of U-J is set to be 3. According to the geometries of 1D IOSMWs, we only consider two kinds of chiral SWCNTs with simple geometries: the armchair SWCNT(n, n)s with lattice constant of 2.46 Å and zigzag SWCNT(n, 0)s having a lattice constant of 4.26 Å. Moreover, different from the metallocenes encapsulated SWCNTs,23,24 the mismatch of the lattice constants between 1D IOSMWs and SWCNTs require their combination satisfy the relation of χC1 = γC2, (χ, γ is integer, C1, C2 is the lattice constant of 1D IOSMWs and SWCNTs, respectively.) Considering the calculation consumption, we constructed tens of heteronanostructures combined by five 1D IOSMWs33 of [ScCp]∞, [VCp]∞, [MnCp]∞, [FeCp]∞, and [CoCp]∞ and three narrow SWCNTs, (n, m) = (7,7), (10,0), and (11,0), denoted as [TMχCpχ/γ(n, m)]∞. The mismatch degree of lattice parameters between such 1D [TMCp]∞ wires and SWCNTs are summarized in Table S1 in the Supporting Information (SI). Except 1D [Mn5Cp5/4(10,0)]∞/[Mn5Cp5/ 4(11,0)]∞ and [Mn3Cp3/4(7,7)]∞ have the lattice compressing/stretching factors of 2.6% and 1.2%, all the other 1D [TMχCpχ/γ(n, m)]∞s bear a negligible mismatch degree (
