Controlled Synthesis Of Semiconducting Single-Wall Carbon Nanotubes By Floating Catalyst Chemical Vapor Deposition

Single-wall carbon nanotubes(SWCNTs)demonstrate to be one of the most promising materials with many excellent properties owing to their unique one dimensional nanostructure.However,the as-synthesized SWCNT sample are usually a mixture of semiconducting and metallic nanotubes,which hinders the practical application of SWCNTs in electric devices.Therefore,bulk controlled synthesis of SWCNTs with a uniform electrical type or even single chirality has been a key problem in the field of carbon nanotubes.Floating catalyst chemical vapor deposition(FCCVD)is an effective method to prepare bulk SWCNTs.An improved FCCVD was adopted to synthesize the high quality SWCNTs by an injection method offering the carbon source,the catalyst precursor and the promoter were fed by the pump in the liquid phase with precisely controlled rate.Enrichment of semiconducting SWCNTs was systematically studied by optimizing growth conditions of FCCVD technique.The main obtained results are as follows:Synthesis of high quality SWCNTs with uniform diameter distribution.We use an injection floating catalyst chemical vapor deposition methods(FCCVD)to synthesize SWCNTs with benzyl alcohol,ferrocene,and thiophene as the carbon source,catalyst precursor,and growth promoter,respectively.High purity,high quality SWCNTs with narrow diameter distribution were synthesized in bulk under optimized growth conditions.In situ synthesis of high quality semiconducting SWCNTs(s-SWCNTs).Because ethanol can be decomposed to hydroxyl radicals which will preferentially etch the metallic nanotubes due to the higher chemical activity of the metallic nanotubes,ethanol were introduced as the second type carbon source and etching agent to selectively remove metallic SWCNTs.Under optimized synthesis conditions,semiconducting enriched(-90%)SWCNTs with high quality and purity were obtained,which demonstrated a high oxidation resistance temperature of 790 ?.Collection of SWCNT films.SWCNT film are in-situ collected by installing a filter membrane collecting device on the FCCVD system.Uniform semiconducting or no-counductivity-selective SWCNT thin films with a controllable thickness were easily obtained which may find many potential applications in optoelectronic devices.