Angelw. Chem. Int. ed.: the longest precise synthetic graphene nanobelt in history

The discovery of fullerenes, nanotubes and graphene stimulated the synthesis of low dimensional carbon nanostructures Among them, the quasi one dimensional atomic precise substructure of graphene is called graphene nanoribbons (NRS) NR has unique electronic, optical and mechanical properties, and is considered to be a candidate for the development of new technologies such as electronics, photonics and energy conversion The properties of NRs are highly dependent on several structural variables, such as width, length, edge structure and heteroatom doping Therefore, the atomic precision control of these variables is necessary to establish their basic properties and explore their potential applications The edge structures of NRs affect their metallicity and photon properties The gap size of NRs is strongly affected by the width Length is also an important variable in NRs, because the size of energy gap decreases with the increase of length until saturation NR with length > 5 nm has great potential Even if there is a great progress in the synthesis of NRs, the existing methods can not control the atomic precision of NRs whose length is more than 5nm in width, length and edge structure at the same time Top-down methods, such as cutting graphene by lithography or compressing carbon nanotubes, have been used to prepare NRs, but they can not control the structure of atomic precision The bottom-up surface synthesis and solvent polymerization can control the edge and width of NRs, but not the length The promising way to control the atomic precision in edge, width and length simultaneously is to synthesize organically in solution At present, several monodisperse NR families with a length of more than 2 nm have been reported, most of which are synthesized by some aromatic derivatives So far, NR with a length of nearly 5nm has been obtained by this method From the perspective of organic chemistry, the synthesis of NRs with length greater than 5nm is very challenging, because a large number of different synthesis and purification steps must be optimized separately, which makes the synthesis, purification, characterization and other processes difficult or even hindered Iterative synthesis of NR-10, nr-20, and nr-30 (source: angel Chem Int ed.) now, a team led by Aurelio Mateo Alonso of POLYMAT in Spain has developed a method for the preparation of monodisperse nitrogen doped nanoribbons Using two different molecular structural units, a series of nanoribbons formed by 10,20 and 30 linear fused aromatic rings were precisely synthesized through a series of iterative deprotection and condensation reactions The nanoribbons are 2.9nm, 5.3nm and 7.7nm in length, respectively 7.7nm is the longest monodisperse NR reported so far The NMR spectra of NR-10, nr-20 and nr-30 (source: angel Chem Int ed.) show that the whole NR series is soluble in chlorinated solvent and can be purified by fast chromatography The characterization and performance of the NR series are studied by NMR, HRMS, absorption spectrum and cyclic voltammetry In addition to clarifying the molecular structure, these studies also describe their structure-activity relationship in detail Moreover, these NRS also reveal some properties that have little correlation with length, such as light gap, photoluminescence spectrum and pseudo photoconductivity In general, this method can not only prepare the longest atom level precise control NR structure reported so far, but also provide a method for the synthesis of longer monodisperse NR to verify the theoretical properties of prediction and explore the development of new transistors, photodetectors, solar cells, etc The limitation of this iterative synthesis method remains to be seen Paper link: http://onlinelibrary.wiley.com/doi/10.1002/anie.201710467/abstract