Abstract
In floating catalyst chemical vapor deposition (FC-CVD), tuning chirality distribution and obtaining narrow chirality distribution of single-walled carbon nanotubes (SWCNTs) is challenging. Herein, by introducing various amount of CO2 in FC-CVD using CO as a carbon source, we have succeeded in directly synthesizing SWCNT films with tunable chirality distribution as well as tunable colors. In particular, with 0.25 and 0.37 volume percent of CO2, the SWCNT films display green and brown colors, respectively. We ascribed various colors to suitable diameter and narrow chirality distribution of SWCNTs. Additionally, by optimizing reactor temperature, we achieved much narrower (n,m) distribution clustered around (11,9) with extremely narrow diameter range (>98% between 1.2 and 1.5 nm). We propose that CO2 may affect CO disproportionation and nucleation modes of SWCNTs, resulting in SWCNTs’ various diameter ranges. Our work could provide a new route for high-yield and direct synthesis of SWCNTs with narrow chirality distribution and offer potential applications in electronics, such as touch sensors or transistors.
Highlights
In floating catalyst chemical vapor deposition (FC-CVD), tuning chirality distribution and obtaining narrow chirality distribution of single-walled carbon nanotubes (SWCNTs) is challenging
Single-walled carbon nanotubes (SWCNTs) have attracted massive attention owing to their exceptional structural and electronic properties.[1−4] Because the electronic and optical properties of SWCNTs critically depend on their chirality, it is important to achieve SWCNTs with narrow chirality distributions
The postsynthesis purification method is primarily based on a solution process, such as ion-exchange chromatography separation (IEX) of DNA-wrapped SWCNTs,[5] density gradient ultracentrifugation (DGU),[6] gel chromatography[7] and aqueous two-phase separation techniques.[8]
Summary
To further understand the chiral structure distributions of SWCNTs in the produced samples, electron diffraction analysis of both the individual and bundled nanotubes was carried out using a TEM. Communication distribution for SWCNTs with 0.25 vol % CO2, a dominant and sharp absorption peak is observed in the visible region (∼610 nm), leading to the green color (Figure 1). With a broader chirality distribution in SWCNTs with 0 or 0.50 vol % CO2, only weak peaks are observed in the visible region, resulting in the normal gray color. The colors of the SWCNT thin films are attributed to nanotube diameter distributions in particular ranges that give rise to absorption peaks in the visible region.
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