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J. Phys. Chem. C 2008, 112, 18412–18416
One-Dimensional Confinement of CdS Nanodots and Subsequent Formation of CdS Nanowires by Using a Glycolipid Nanotube as a Ship-in-Bottle Scaffold Yong Zhou,†,§ Qingmin Ji,‡,⊥ Yoshiki Shimizu,‡,| Naoto Koshizaki,‡,| and Toshimi Shimizu*,†,‡,¶ SORST, Japan Science and Technology Agency (JST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Nanoarchitectonics Research Center (NARC), National Institute of AdVanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan ReceiVed: August 23, 2008
This work reports one-dimensional (1-D) confinement of CdS nanodots (NDs) and the subsequent formation of CdS nanowires by employing a self-assembled lipid nanotube (LNT) from the synthetic glycolipid N-(11cis-octadecenoyl)-β-D-glucopyranosylamine as a scaffold. Two paths have been used to realize the 1-D arrangement of the CdS NDs in the LNT. One is that the LNT was dispersed into aqueous solutions of water-soluble CdS NDs, and then the fluidic NDs diffuse into the hollow cylinder of the LNT via capillary force. The other is that the solution of a CdS precursor diffuses into the LNT, followed by in situ formation of CdS NDs in the nanochannels of the LNT. The LNT and prepared CdS-NDs-encapsulated-LNT were characterized by using field-emission scanning electron microscopy (FE-SEM), scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), and fluorescence microscopy. Furthermore, calcination of the CdS-NDs-encapsulated LNT enabled us to obtain single-crystalline CdS nanowires. Introduction Benefiting from the specific properties of biomolecules with well-defined dimensions, there is increasing interest in utilizing linear self-assemblies of biomolecules to modulate the 1-D arrangement of a large variety of technologically important nanoparticles.1-11 The biomimetic construction of a linear array of the nanoparticles offers scientific opportunities to investigate the influence of the obtained nanoparticle size, shape, and dimensionality on their collective properties of electronic, photonic, and energy transfer.2 That procedure also contributes to exhibit significant potentials toward many practical applications in nanodevices. Many remarkable reviews have outlined the successful syntheses of such bioinspired 1-D arrangement of inorganic nanomaterials.1-9 Designed lipid molecules can organize in liquid media into open ended, hollow cylindrical structures through noncovalent self-assembly, which are composed of rolled-up bilayer membrane walls.1 The lipid headgroups can function as templates for the nucleation, growth, and deposition of inorganic substances on the external and internal surfaces, and the wall membranes of preformed LNTs, as reviewed by us recently.12 Modification of helical arrays of CdS nanoparticles on the external surface of a functionalized glycolipid nanotube has potential application as optical materials for microelectronic devices.13 In situ growth of CdS in the bilayer membrane walls of a peptidic LNT enables us to fabricate fluorescent nanotubes, which is applicable for biomolecule delivery.14 Tubular self* Corresponding author. Fax: +81-29-861-4545. E-mail:
[email protected]. † SORST, JST. ‡ NARC, AIST. § Current address: Department of Chemistry, National University of Singapore, Singapore ⊥ Current address: National Institute for Materials and Science (NIMS), Japan. | Current address: Nanotechnology Research Institute, AIST, Japan. ¶ Current address: Nanotube Research Center, AIST, Japan.
Figure 1. Schematic illustration for the confined 1-D arrangement of CdS NDs and the subsequent formation of CdS nanowires by using a LNT as a ship-in-bottle scaffold.
assembly of a glycolipid on metal oxide nanowires also allows us to produce aligned nanocables.15 The linear hollow cylinders and channels inside the LNTs are considerably useful nanospaces for one-dimensional (1-D) confinement of nanomaterials. The templating hollow spaces of the LNTs have a few unique properties that no other individual templates possess: (1) Such tubular structures are of interesting hydrophilic internal and external membrane surfaces, in sharp contrast to carbon nanotubes. (2) The diameters of the hollow channel characteristically span the region between 10 and 1000 nm, and most of the
10.1021/jp807537w CCC: $40.75 2008 American Chemical Society Published on Web 11/04/2008
One-Dimensional Confinement of CdS Nanodots
J. Phys. Chem. C, Vol. 112, No. 47, 2008 18413 encapsulation and 1-D arrangement of semiconductor NDs such as CdS in tubular biomolecules. Such an array can be used for the quantum confinement of light and electrons for applications such as molecular computing.2 In this work, we describe 1-D confinement of CdS NDs in the hollow cylinder of a LNT and the subsequent formation of CdS nanowires by employing the LNT as a “ship-in-bottle” scaffold. Size tunability of the performed CdS NDs may allow us to obtain different functionalities from these 1-D semiconductor arrays. The tubular structure may also act as a physical shield to protect such a nanoscaled semiconductor whose property is very sensitive to its surface state from potential environmental contamination. Experimental Section We used the LNT from a synthetic glycolipid N-(11-cisoctadecenoyl)-β-D-glucopyranosylamine (1), which can self-
Figure 2. (a) FE-SEM and (b) STEM images of the LNTs selfassembled from 1.
diameters fall in the 10-200 nm range. Neither top-down-type microfabrication procedures nor any fabrication methods for both carbon nanotubes (1-10 nm)16 and molecular hollow cylinders such as cyclodextrin17 and cyclic peptide nanotubes (
