Study On Selective Effect Of Conjugated Polymer To The Selective Chiral Enrichment Of Single-walled Nanotubes And Their Band Structure Regulation

As a one-dimensional carbon nanomaterial,carbon nanotube has excellent electronics and optical properties,and is a potential ideal material to replace traditional silicon-based semiconductors.Unfortunately,the commercial available carbon nanotubes are all a mixture of metallic and semiconductor types,whose band gap varies a lot.For the application of electronic devices,the presence of metallic carbon nanotubes will quench the excitons,thereby affecting the performance of the device.Meanwhile,the selective sorting of semiconducting singlewalled carbon nanotubes(SWCNT)of single chirality is essential for the construction of highperformance electronic nanodevices.However,there is often a trade-off between yield and chiral purity in conventional sorting process of SWCNTs.In addition,it is difficult to improve the performance of the device based on intrinsic carbon nanotubes with fixed band structure,which further restricts their application.Therefore,realizing the selective separation of carbon nanotubes and regulating their band structure,have both theoretical significance and practical value.Thus,the main work of this article is as follows:(1)Instead of using conventional single organic solvent,a mixture of toluene and chlorobenzene in a certain ratio was used for carbon nanotube dispersion.The sorting efficiency of(6,5)SWCNT was greatly improved by polymer extraction,while the chiral purity of sorted SWNT could be maintained.We further proved that the separation efficiency would not decrease even after multiple extractions,and the chiral selectivity of the obtained SWCNTs depended on the precise ratio between the two solvents.The polymer(or solvent molecule)-SWCNTs interaction controlled by solvent polarity is believed to be the reason for our results,which was later successfully verified by molecular dynamics simulations.(2)We aim to obtain polymer/single-chiral carbon nanotube composite since the ?-?interaction of polythiophenes including PBTTT-C12,PBTTT-C14 and P3 HT with carbon nanotubes is greater than the counterpart of PFO-BPy to carbon nanotubes.By replacing PFOBPy molecules in PFO-BPy/(6,5)SWCNT nanocomposite,we successfully formed a series of polythiophene-wrapped composites which contained only single chiral semiconducting carbon nanotubes(PBTTT-C12/(6,5)SWCNT,PBTTT-C14/(6,5)SWCNT,etc).Such results can further improve the selective enrichment of carbon nanotubes sorted by conjugated polymers.(3)Using in-situ fluorescence electrochemical spectroscopy measurement,the band structure of carbon nanotubes wrapped by different polymers including PBTTT-C12,PBTTTC14,P3 HT,and F8T2 was precisely determined.A significant change in the band gap of polymer-wrapped(6,5)SWCNTs was found compared to their intrinsic values.The molecular dynamical simulation indicates that the interaction between conjugated polymers and carbon nanotubes is the key factor affecting the band structure of carbon nanotubes: the larger polymercarbon nanotube interaction is,the more carbon nanotube's band gap changes.Therefore,a reasonable design of the conjugated polymer structure is expected to achieve fine control of the energy band of carbon nanotubes,thereby achieving the purpose of improving the performance of carbon nanotube devices.