The most efficient and cost-effective method for synthesizing single-walled carbon nanotubes SWCNTs with controlled diameters and chirality is the catalytic chemical vapor deposition CVD method, specifically using a floating catalyst CVD technique.In the catalytic CVD method, a carbon-containing gas such as methane, ethylene, or acetylene is decomposed at high temperatures 600-1200C in the presence of a catalyst, typically transition metal nanoparticles e.g., iron, cobalt, or nickel . The catalyst particles play a crucial role in controlling the diameter and chirality of the SWCNTs.The floating catalyst CVD technique involves introducing the catalyst and carbon source into a high-temperature reaction zone simultaneously. This method allows for better control over the catalyst particle size and, consequently, the diameter and chirality of the SWCNTs. Additionally, this technique enables continuous production of SWCNTs, which significantly reduces the cost of synthesis.To further improve the control of diameter and chirality, researchers have developed several strategies, such as:1. Precise control of catalyst particle size: By using size-selected catalyst nanoparticles, the diameter distribution of SWCNTs can be narrowed down, leading to better control over the chirality.2. Template-assisted growth: Using porous templates e.g., anodic aluminum oxide or mesoporous silica with well-defined pore sizes can help control the diameter and chirality of SWCNTs by confining the growth within the pores.3. Chiral-selective growth: By modifying the catalyst surface with specific organic molecules or by using specific gas-phase additives, researchers have achieved selective growth of certain chiralities of SWCNTs.Despite these advancements, achieving perfect control over the diameter and chirality of SWCNTs remains a challenge. Further research and development are needed to optimize the synthesis process and improve the selectivity of SWCNTs with desired properties.