Chinese University of Science and Technology

[ Instrument Network Instrument R & D ] Recently, Dong Zhenchao's research team and Luo Yi's research team of the single molecule science team led by Hou Jianguo, an academician of the Chinese Academy of Sciences and a professor at the University of Science and Technology of China, have made new progress in the field of single molecule Raman imaging and achieved the E-class single Real-space imaging of various vibration modes in molecules resolved by chemical bonds, and a new molecular chemical structure reconstruction technology, Scanning Raman Picoscopy (SRP), is proposed. The results were published online in the National Science Review (NSR) on November 8, 2019, and were formally published recently.
Accurately determining the chemical structure of a molecule is of vital significance to any molecular related field and is the key to a deep understanding of the properties and functions of molecules such as chemistry, physics, and biology. Scanning tunneling microscopes and atomic force microscopes have the outstanding ability to image single-molecule backbones in real space, but these technologies often lack the chemical information necessary to accurately determine the structure of a single molecule. The Raman scattering spectrum contains a wealth of molecular vibrational structure information. The Raman spectra of different chemical groups have different shape characteristics. Therefore, Raman spectra can be used as a "fingerprint" identification tool for molecular chemical groups, but conventional Raman The imaging technology does not reach the ultra-high spatial resolution of scanning tip technology. Therefore, the tip-enhanced Raman spectroscopy (TERS) technology developed by combining the two can overcome the shortcomings of each technology and provide the possibility for determining the chemical structure of a single molecule.
In 2013, the single-molecule science team led by Hou Jianguo demonstrated the sub-nano-resolution single-molecule Raman imaging technology for the first time [Nature 498, 82 (2013)], improving the spatial resolution with chemical recognition capabilities to less than one nanometer (~ 5 Angstroms). Based on this, researchers have explored the limits of the spatial resolution of single-molecule Raman imaging technology on the one hand, and on the other hand, how to make full use of the unique advantages of this technology. The research results published by the team in the National Science Review have pushed the spatial resolution to a new limit and proposed an important new application for the latest technology. They improved the low-temperature (liquid helium) ultra-high vacuum tip enhanced Raman spectroscopy system and fine-tuned the localized plasmon field at the tip height to improve the spatial resolution to 1.5 Angstroms of single chemical bond recognition. In space, a complete spatial imaging pattern of various intrinsic vibration modes of the molecule was obtained, and significantly different interference effects in molecular symmetrical and antisymmetric vibration modes were found and observed. More importantly, they proposed a new method for visually constructing molecular structures based on the molecular imaging pattern of molecular resolution of Angstrom-class resolution and the new physical effects revealed by them, combined with the Raman fingerprint database of chemical groups: Mane resolution microscopy (SRP).
The SRP method fully demonstrates the ability of pinpoint scanning technology based on Raman signals to accurately determine the chemical structure of molecules in real space. Researchers use a single magnesium porphyrin molecule as a model system and use the "Lego-like" method to splice each chemical group together to achieve the construction of the entire molecular chemical structure. The ability to scan unknown Raman microscopy with the resolution of the A-class scanning Raman microscopy is expected to arouse the interest of scientific researchers in the fields of chemistry, physics, materials, and biology, and lead to related research. Through the combination of artificial intelligence and machine learning, SRP is expected to develop into a mature and universal technology, which provides new methods for determining the chemical structure of a single molecule on a single chemical bond scale, in-situ research of surface physical and chemical processes, and surface catalytic reactions. means.
This series of research work has been supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, the Chinese Academy of Sciences, the Ministry of Education, and Anhui Province.

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