Carbon Nanotube-Nanoparticle Hybrid Structures

Abstract

The discovery of carbon nanotubes (CNTs) (Iijima 1991; Iijima & Ichihashi 1993) has inspired extensive research activities unprecedented in nanoscience and nanotechnology. CNTs are very versatile due to their small diameter, high aspect ratio (Zheng et al. 2004), great structural integrity (Hinds et al. 2004; Jung et al. 2006), high electrical (Kang et al. 2007) and thermal conductivity (Berber et al. 2000), remarkable thermal (Kim et al. 2004) and chemical stability (Liu et al. 1999), and exceptional strength and resilience (Treacy et al. 1996; Saito 1998; Yu et al. 2000). Nanoparticles (NP) with sizes between 1 and 100 nm have attracted considerable interest because of their unique electronic, optical, magnetic, mechanical, and chemical properties that differ from those of both their constituent atoms/molecules and their corresponding bulk materials. CNTs decorated with NPs form a new class of hybrid nanomaterials that could potentially display not only the unique properties of NPs (Fissan et al. 2003; Scher et al. 2003) and nanotubes (Dresselhaus et al. 2001; de Heer 2004; Dresselhaus 2004), but also additional novel physical and chemical properties due to the interaction between CNTs and attached NPs. These hybrid nanomaterials have recently been shown as promising building blocks for various applications, including gas sensors (Kong et al. 2001; Sun & Wang 2007; Lu et al. 2009), fuel cells (Mu et al. 2005; Kongkanand et al. 2006; Robel et al. 2006), solar cells (Landi et al. 2005; Guldi et al. 2006; Kongkanand et al. 2007; Lee et al. 2007), Li-ion batteries (Zhang et al. 2006), hydrogen storage (Yildirim & Ciraci 2005; Anson et al. 2006), and transparent conductive electrodes (Kong et al. 2007). This chapter begins by outlining the significance of CNT-NP hybrid structures in terms of materials advantages and potential applications. Then, we introduce the assembly of various metallic and semiconducting NPs onto the external surfaces of CNTs via the electrostatic force directed assembly (ESFDA) process that we have recently developed. Single-walled CNTs (SWCNTs), multiwalled CNTs (MWCNTs), randomly dispersed CNTs, and well-aligned CNT arrays can be decorated with a broad range of NPs (including both aerosol and colloidal NPs) through the ESFDA process for the generation of CNT-NP hybrid