Structure Separation Of Carbon Nanotubes Based On Gel Chromatography

As a one-dimensional tubular carbon nanomaterial,carbon nanotubes(CNTs)have excellent optical,electrical,thermal and mechanical properties,and have broad application prospects in the fields of optoelectronic devices,information,energy,and biomedicine.At the same time,CNTs have diverse atomic helical structures,showing the rich and unique optoelectronic and physical properties of one-dimensional materials,and providing a material basis for the study of novel photon phenomena and physical properties.Controlling the atomic structure of CNTs and preparing single structure CNT materials with uniform properties are very meaningful for in-depth clarification of the intrinsic properties of CNTs,which are also very important not only for realization of their property modulation and functional design,but also for development of advanced applications in different fields.At present,the main ways to control the atomic structure of CNTs include structure-selective growth and separation.The growth CNT products are usually a mixture containing different structures,limiting the property and application researches.Therefore,a subsequent purification process called structure separation is required.In this paper,a commercialized sodium hyodeoxycholate(SHC)surfactant is applied for dispersing and separating CNTs for the first time.After establishing gel chromatography based on a newly developed mixed surfactant,the structure separation of CNTs is achieved,which lays an important foundation for their property researches and functional applications.The detailed results are shown in the following:A mixed surfactant system of sodium dodecyl sulfate(SDS)+SHC+sodium deoxycholate(DOC)was established to explore the structure separation of small-diameter CNTs with an average diameter of less than 1 nm.The results show that under the condition of 0.5%SDS+0.05%SHC,CNTs can be perfectly adsorbed on the gel column for Co Mo CAT(SG65i)material.Subsequently,stepwise elution chromatography was performed using the mixed surfactant solution of 0.5%SDS+0.05%SHC+X%DOC to elute the adsorbed CNTs.As a result,high-purity single-chirality(6,5)CNTs were separated successfully.Here,the concentration of SHC(0.05%)is only one-tenth of sodium cholate(SC)(0.5%)used in the traditional method,which greatly reduces the cost of structure separation of CNTS.After that,we used the same conditions to separate other five CNT materials,including Hi Pco,Co Mo CAT(CG100),Co Mo CAT(CG300),Co Mo CAT(SG76),and GNH-1200 with wide diameter distribution.We find that single-chirality(6,5)CNTs can be separated at the same DOC concentration,indicating that this separation method is not limited by raw CNT materials and has universal applicability.We also explored the structure separation of large-diameter CNTs with an average diameter of larger than 1 nm.Firstly,the dispersion capability of SHC surfactant is several times higher than that of SC surfactant,indicating that SHC is more suitable for dispersing the high-concentration CNT solution.This is of great significance for the macroscopic separation and applications of CNTs.From the results of the structure separation of large-diameter CNTs based on the mixed surfactant of SDS+SHC+DOC,it can be seen that the present mixed surfactant has obvious diameter selectivity for large-diameter CNTs,which can separate high-purity semiconducting CNTs with different diameters.At the end of this work,we used the separated large-diameter high-purity semiconducting CNTs to fabricate thin-film transistors and measured their electrical properties.The on/off ratio was about 10~6,and the device performance is good.