Carbon Nanotube Webs: A Novel Material for Sensor Applications

Abstract

and drying. CNT webs mainly comprise highly pure and wellaligned CNT, with some occasional cross fi bers (mean diameter ≈ 10 nm), and they are electrically conductive. [ 24 , 25 ] In this communication we report a new and simple method that has potential for the mass production of highly electroactive sensors using CNT webs without the need for binders. These electrodes show very good electrical conductivities comparable to other forms of CNT-based electrodes, such as CNT networks, [ 26 ] with improved chemical and mechanical properties. The properties of the CNT-web-based electrodes were characterized and tested for their suitability for some analytical applications.The high degree of fl exibility of CNT webs enables the design of electrodes with different geometries such as planar, yarn, ring, and ribbon, as shown in Figure 1 . The simplest confi guration is the planar or disc electrode. This design can be readily adapted for the mass production of electrodes using the setup shown in Figure S1A (Supporting Information) and was used throughout this study. The amount of CNT can be controlled either by controlling the number of CNT web layers or by the electrode electroactive surface area. It is clear from Figure 1 A,B that CNT webs maintain a high degree of alignment with occasional cross CNT fi bers in between. Each single CNT within the web is made of an average of seven inner walls (multiwalled) (Figure 1 B, inset), about 450-μ m-long and around 10-nm in diameter . The second possible design using CNT webs is the yarn, which is prepared by twisting the CNT web during the spinning process as shown in Figure 1 C. CNT web yarns or fi bers are highly electrically conductive ( ≈ 300 S cm − 1 for 10-μ m-diameter) with strengths greater than 460 MPa. Yarns with different diameters can be prepared by adjusting the width of the CNT web and by combining more fi bers together to form larger bundles. CNT web yarns are very useful in fabricating nano-and microelectrodes. The third geometry is the ring electrode (Figure 1 D) that is prepared by wrapping the CNT web continuously around a cylindrical support such as a glass or Tefl on rod. This kind of design is very useful for preparing a multielectrode system confi guration, for electrode miniaturization, and for applications involving rotating ring electrodes. CNT web ring electrodes are very useful for energy storage applications due to their high fl exibility, mechanical stability, and electrical conductivity. The fourth possible geometry for CNT webs is the ribbon design (Figure 1 E). This can be described as a free-standing CNT web that comprises a large number of CNT web layers (usually > 50 layers) to maintain the needed mechanical stability in order to remain intact. Preparation of the CNT web ribbon is similar to the procedure for planar electrodes and is followed by the removal of the thick CNT web layers from the support. The CNT web ribbon is very

Focused Ion Beam Milling of Carbon Nanotube Yarns and Bucky-Papers: Correlating Their Internal Structure with Their Macro-Properties

“…This technique generates very thin, semialigned bucky-papers and can be applied to any type of CNT forest, regardless of its CNT surface density, diameter or length or spinnability. The second route involves drawing webs from spinnable CNT forests [ 49 ]. Multiple layers can be overlapped and densifi ed to form well-aligned bucky-papers, referred to as buckyribbons.…”

Direct spun aligned carbon nanotube web-reinforced proton exchange membranes for fuel cells

“…16 In addition to the high thermal and electrical conductivity, and mechanical and chemical robustness of CNTs, the interconnectivity and excellent alignment in the direction of draw make the dsCNT webs attractive materials alone and as additives to other materials. 16 We herein introduce a novel method for producing a stable, thin and highly conductive composite PEM containing a model ionomer, sulfonated poly(ether ether ketone) (SPEEK), and dsCNT webs drawn from CNT forests. In this method, as the CNTs are drawn directly from CNT forests and each layer is placed in a controlled position in the membrane, the dsCNT webs do not undergo dispersion and wet-processing allowing alignment.…”

Distinguishing Field Effects from Charge Effects in the Optoelectronic Properties of Carbon Nanotube Films

“…While much attention has been given to precise optical measurements on individual single-wall carbon nanotubes (SWNTs) or monodispersed populations of SWNTs, devices made from heterogeneous mixtures of nanotubes continue to be of interest for use as field emitters, actuators and transducers, chemical sensors, transparent conductive films, and field-effect transistors [1][2][3][4][5][6]. Electroabsorption (EA) is a powerful tool for understanding the nature of excited states in materials, and the technique has been applied to various types of nanotube samples over the course of the last decade.…”