Directly Synthesized Strong, Highly Conducting, Transparent Single-Walled Carbon Nanotube Films

Abstract

We report the direct synthesis of strong, highly conducting, and transparent single-walled carbon nanotube (SWNT) films. Systematically, tests reveal that the directly synthesized films have superior electrical and mechanical properties compared with the films made from a solution-based filtration process: the electrical conductivity is over 2000 S/cm and the strength can reach 360 MPa. These values are both enhanced by more than 1 order. We attribute these intriguing properties to the good and long interbundle connections. Moreover, by the help of an extrapolated Weibull theory, we verify the feasibility of reducing the interbundle slip by utilizing the long-range intertube friction and estimate the ultimate strength of macroscale SWNTs without binding agent.Because of their optical transparency and unique electric properties together with mechanical flexibility, film-like single-walled carbon nanotubes (SWNTs) are attractive not only for fundamental researches but also potential applications. For example, large optical nonlinearity, 1 subpicosecond optical response 2,3 and bolometric infrared photoresponse 4 have been observed in SWNT films, and the feasibilities of using SWNT films or networks as sensors, 5,6 diodes, 7 and field effect transistors 8 have already been demonstrated. Recently, highly conducting transparent SWNT films (tSWNTs) have also been fabricated by a kind of controlled filtration-deposition process, 9 which could be used as transparent electrodes for GaN/InGaN or flexible organic lightemitting diodes. 10,11 However, almost all of the above reports focused on the post-treated SWNT films, which are obtained through solution-based filtration processes. As known, to obtain high conductivity, SWNTs must be well purified and dispersed from sootlike morphology, which usually costs several days and leaves unrecyclable chemical residues. Besides, the comparative low strength of these films is one of the challenges for their applications, especially in the field of high-strength enforcement sheets.Here we report the direct synthesis of strong, highly conducting, and transparent films through a further developed floating catalyst CVD (FCCVD) technique that is based on the methods of producing large-scale nonwoven SWNTs. 12 As catalyst source, ferrocene/sulfur powder is heated to 65-85°C and flowed into a reaction zone by the mixture of 1000 sccm argon and 1-8 sccm methane. The growth rates of the films are mainly determined by the sublimation rate of the catalysts. Under typical conditions, after 30 min growth, thin films with a thickness of 100 nm will form in the high-temperature zone (over 600°C) of the quartz tube and can be easily peeled off. This type of large-area freestanding film can be easily handled for further researches. Raman scattering and HRTEM images show that most CNTs in the films are single-walled carbon nanotubes. In this paper, we systematically investigated the properties of the directly

Continuous production of flexible carbon nanotube-based transparent conductive films

“…We are encouraged by this as at this stage the CNT synthesis process has not yet been optimized for the combination of optical transparency and electrical conductivity, nor have any post-processing treatments been Conductance against transparency for different nanotube films. Our own results (solid circles for free-standing, squares for polymer-backed) are compared against the results of Budhadipta et al [7] (upright triangles), Geng et al [6] (inverted triangles), Zhou et al [5] (diamonds), Ma et al [8] (left-pointing triangles), Kaempgen et al [15] (stars), Green and Hersam [16] (right-pointing triangles) and Yu et al [17] (empty circles).…”

“…Popular methods for this deposition include inkjet printing [5] and air spraying [6]; recently a draw-down rod coating method has been reported [7] with impressive conductivity. Direct synthesis procedures reported to date have required the nanotube film to be peeled off a quartz substrate [8], a factor that would limit the transparency of the films produced (as the films will need a certain amount of thickness to provide mechanical integrity) and has questionable scalability. It would be advantageous to be able to produce functional transparent nanotube films in a single step, allowing greater control over tube alignment in the film, faster production and easy scalability.…”

Flexible Supercapacitors – Development of Bendable Carbon Architectures

“…[14][15] Such films are different from conventional SWCNT films prepared by other post-deposition methods that produce short and randomly-oriented structures. A continuous reticulate architecture endows directly synthesized films superior electrical conductivity (about 2000 S/cm) and better mechanical properties than that of post-deposited SWCNT films.…”

Nanomaterial-based stretchable and transparent electrodes

“…Besides the aligned CNT structure, random network structures of CNTs have also been investigated to realize stretchable transparent electrodes via solution-based coating [85,86], floating catalyst CVD (FCCVD) [87][88][89], and electrospinning [90]. The stretchability of the random network differs from that of the aligned network of CNTs, and the random network can be biaxially stretched.…”

“…By flowing a catalyst source and reaction gas into a chamber at the same time, free-standing SWCNTs can be directly synthesized onto a substrate, as shown in Figure 4(e) [87]. Xie et al reported an FCCVD-synthesized SWCNT random network as a stretchable transparent electrode.…”