Carbon has a variety of isotropes, such as diamond, graphene, carbon nanotubes, fullerene, carbon chains and so on. Among them, two-dimensional graphene, one-dimensional carbon nanotubes and carbon chains are the key materials that scientists are currently focusing on. Carbon nanotubes have entered a bottleneck period due to their wide variety of chiral properties and the difficulty of synthesizing one-handed semiconductor carbon nanotubes. Graphene has an extremely high charge mobility and is a strong competitor for silicon replacement in the semiconductor industry in the future. However, graphene is a semi-metallic material that has no band gap itself, greatly limiting its application in the semiconductor field. The transformation of graphene from a two-dimensional planar structure to a one-dimensional nanostrip structure can intrinsically introduce band gaps, so graphene nanostrips have become a research hotspot in recent years. The one-dimensional carbon chain itself is a semiconductor material, so it has received more and more attention.
After joining the School of Materials Science and Engineering, Associate Professor Shi Lei of Sun Yat-sen University founded the "One-dimensional Nano-Carbon" research group in Professor Yang Guowei's team, aiming to promote and develop the research of one-dimensional nano-carbon materials at home and abroad. The research direction of the research group focuses on the preparation, performance and application of fully one-dimensional carbon chains and quasi-one-dimensional carbon nanotubes and graphene nanostrips. Since joining the company, Associate Professor Lei Shi has been the corresponding author in Angw. Chem. Int. Ed., Nano Lett., Carbon and other journals have published more than ten research papers. Recently, the research group has made a series of important progress, which is summarized and reported as follows.
1. Exciton kinetics of one-dimensional carbon chains
Near-field Raman spectroscopy (Shi L., et al. 1000, 2017). Nature Materials, 15, 634-639, 2016), Resonant Raman Spectroscopy (Shi L., et al. Nano Letters, 21, 1096–1101, 2021), anti-Stokes Raman spectroscopy (Tschannen C. D., et al. ACS Nano, 15, 7, 12249–12255 2021) and Raman scattering cross-section (Tschannen C. D., et al. Nano Letters; 20, 6750−6755, 2020)) was studied in detail. Recently, in collaboration with researchers at the University of Cologne and others, we have used time-resolved Raman spectroscopy to explore the relaxation dynamics of excitons in one-dimensional carbon chains.
After the one-dimensional carbon chain is excited by the picosecond laser, the relaxation time of the Raman spectral signal is much longer than that of the quasi-one-dimensional carbon nanotube, which illustrates the specificity of the one-dimensional structure. We found that the Raman signal of the carbon chain cannot be observed by using a steady-state laser far from the resonance region to excite the carbon chain, while a picosecond laser with the same energy can be used to excite the carbon chain, and a strong Raman spectrum of the one-dimensional carbon chain can be observed. Based on this, we propose the hypothesis that there is a strong energy transfer between carbon nanotubes and carbon chains, which affects the exciton dynamic behavior of the two. To test this hypothesis, we confirmed the existence of energy transfer by comparing the phonon relaxation kinetics of carbon nanotubes and carbon chains. In addition, through the study of the phonon relaxation kinetics at low temperatures, we found that exciton recombination is affected by defective or optical bronchon-assisted processes, rather than direct exciton-exciton recombination. Our research has improved understanding of the interactions between allotropes of carbon in different dimensions, and this method is also applicable to most exciton dynamics studies of one- and two-dimensional materials.
The research results were published in Laser & , the top academic journal of optics , Under the title "Unraveling the excitonic transition and associated dynamics in confined long linear carbon-chains with time-resolved resonance Raman scattering" Photonics Reviews (Impact Factor 13.138). Dr. Zhu Jingyi of the University of Cologne is the first author and co-corresponding author, Associate Professor Shi Lei is the final corresponding author, Professor Van Loosdrecht Paul H.M. of the University of Cologne and Researcher Wu Kaifeng of the Dalian Institute of Chemical Physics are co-corresponding authors, and collaborators of the University of Vienna and the University of Chinese of Hong Kong are co-authors of the paper. This research work is partially supported by the National Natural Science Foundation of China and the Guangdong Provincial Foundation of Basic and Applied Basic Research.
Thesis Link:
https://doi.org/10.1002/lpor.202100259
2. Laser in situ heating synthesis performance can control one-dimensional carbon chain
The structure of the one-dimensional carbon chain is extremely unstable, it is difficult to exist at room temperature and pressure, and it is easy to cross-link reactions between each other, so the research on carbon chains is slow and difficult to carry out. In order to solve the problem of the stability of the one-dimensional carbon chain, we previously synthesized a stable one-dimensional carbon chain with a world record length of carbon nanotubes (Shi L., et al. Nature Materials, 15, 634-639, 2016）。 On this basis, we synthesized a one-dimensional carbon chain with controllable performance (Shi L., et al. Nano Letters, 21, 1096–1101, 2021）。 However, since there are no fully controllable diameter carbon nanotubes, there are still challenges for the control synthesis of one-dimensional carbon chains.
Previously, we tried to synthesize inner carbon nanotubes in single-walled carbon nanotubes using laser in situ heating (Chimborazo L., et al. Applied Physics Letters 115, 103102, 2019）。 On this basis, we will disperse the double-walled carbon nanotubes scattered on the micrograting under the Raman spectrometer lens with a laser wavelength of 568 nm to heat the sample, through the Raman spectroscopy can monitor the growth of the carbon chain in situ, and since the microgrid is position-marked, the heated sample location can also be easily found in the electron microscope test, so the carbon chain growing after laser heating can be observed in electron microscopy.
The relevant research results were published in Carbon, an internationally renowned academic journal on carbon materials, under the title of "Photothermal Synthesis of Confined Carbyne", and were selected for the cover of 183 volumes. Associate Professor Shi Lei is the first author and co-corresponding author of the paper, school of materials science and engineering of Sun Yat-sen University is the first unit of the paper, Professor Thomas Pichler is the co-corresponding author, and collaborators of the University of Vienna and the Institute of Integrated Industrial Technology are co-authors. This research work is partially supported by the National Natural Science Foundation of China, the Guangdong Provincial Foundation of Basic and Applied Basic Research, the basic scientific research business fees of central universities, and the start-up fund of the "Hundred Talents Program" of Sun Yat-sen University.
https://doi.org/10.1016/j.carbon.2021.05.058
3. Limited-area growth of graphene nanostrips
Graphene nanostrips have unique electrical properties, which are more suitable for the development of a new generation of electronic devices than two-dimensional planar graphene with zero band gap, and have received widespread attention from the academic community in recent years. The band gap of graphene nanostrips is regulated by their width and edge structure, so the controllable preparation of graphene nanostrips with specific edges and widths is an important topic in this field. The confined space provided by single-walled carbon nanotubes of different diameters regulates the reaction of small molecule precursors for nanoreactors to synthesize specific graphene nanostrips with a unique reaction mechanism, which is worth further research and development.
Using ferrocene as a precursor molecule, the research group used a series of single-walled carbon nanotubes with different diameter distributions as nanoreactors to study the relationship between the growth of different graphene nanoscales and single-walled carbon nanotubes. It was found that the width of graphene nanoscale is regulated by the diameter of single-wall carbon nanotubes by Raman spectroscopy and transmission electron microscopy, especially a large number of 6 and 7-armchair-type graphene nanostrips can be prepared by using single-wall carbon nanotubes with an average diameter of 1.3 nm. In addition, the single-walled carbon nanotubes separated by the semiconductor type and the metal type also have a certain impact on the yield of graphene nanostrips. At the same time, it is pointed out that the van der Waals force between graphene nanostrips and single-walled carbon nanotubes is a key factor regulating the growth of graphene nanostrips.
The relevant research results were published in the famous domestic academic journal Nano Research under the title of "Carbon nanotube-dependent synthesis of armchair graphene nanoribbons". Dr. Zhang Yifan of the research group is the first author of the paper, the School of Materials Science and Engineering of Sun Yat-sen University is the first unit of the paper, Associate Professor Shi Lei is the last corresponding author, Professor Yang Guowei is the co-corresponding author, and collaborators of the University of Vienna, the Institute of Integrated Industrial Technology, the University of Ulm, and the Shanghai University of Science and Technology are the co-authors. This research work is partially supported by the National Natural Science Foundation of China and the Guangdong Provincial Foundation of Basic and Applied Basic Research.
http://www.thenanoresearch.com/upload/justPDF/3819.pdf
4. Anti-Stokes Raman spectroscopy of carbon chains
Previously, our collaboration with the Lukas Novotny group at the Swiss Federal Institute of Technology in Zurich has yielded several landmark results. For example, a world record length carbon chain (Shi L., et al. was successfully discovered using near-field Raman spectroscopy. Nature Materials, 15, 634-639, 2016), and the discovery that the properties of carbon chains can be regulated by carbon nanotubes, first validated the carbon chain as carbyne, ending the decades-old controversy over whether carbyne existed (Heeg S., et al. Nano Letters, 18, 5426-5431, 2018）。 We also found that the Raman spectra of a single carbon chain can be easily detected thanks to the fact that it has the largest Raman scattering cross-section of all known materials (Tschannen C. D., et al. Nano Letters, 20, 6750−6755, 2020）。
Recently, a new collaborative study has conducted in-depth research on the anti-Stokes Raman spectroscopy of a single carbon chain, and proposed a local temperature measurement method by comparing the Stokes/anti-Stokes intensity ratio of the carbon chain under different laser power, which is expected to be applied to the field of temperature measurement demand at the nanoscale. The paper was published in ACS Nano.
In this study, the research group provided the carbon chain samples required for the study and the Raman spectra of the samples. Tschannen C. D. of ETH Zurich is the first author and corresponding author, and Associate Professor Lei Shi is the co-author. This research work is partially supported by the National Natural Science Foundation of China and the Guangdong Provincial Foundation of Basic and Applied Basic Research.
https://doi.org/10.1021/acsnano.1c03893
Source: Sun Yat-sen University