New type of chemical microscope: Knock on the door to the observation of single-molecule chemical reactions

Chemistry creates the ever-changing material world, in which individual molecules play a fundamental role
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Recently, a scientific research team led by researcher Feng Jiandong from the Department of Chemistry of Zhejiang University invented a microscope technology that can directly image single-molecule chemical reactions in solution, achieving ultra-high spatial-temporal resolution imaging, and knocking on the door to observe single-molecule chemical reactions

Research object: electrochemiluminescence reaction

　Research object: electrochemiluminescence reaction　research object: electrochemiluminescence reaction

The objects of traditional chemistry and biology research are reactions and changes involving a large number of molecules
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In textbooks of chemistry-related disciplines, chemical reactions are all conceptually described in the form of single molecules, but the results obtained in traditional experiments are the average results of a large number of molecules

Feng Jiandong's research team is committed to the development of interdisciplinary single-molecule measurement methods and instruments, to achieve multi-dimensional single-molecule physical and chemical process observations, new phenomena research and application establishment in solution systems
.

They invented a microscopy technique that can directly image single-molecule chemical reactions in solution, using electrochemiluminescence reactions as the research object to achieve ultra-high spatial and temporal resolution imaging

Electrochemiluminescence is a form of using a series of chemical reactions that occur on the surface of an electrode to achieve luminescence
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Compared with traditional fluorescence imaging technology, because it does not require light excitation, electrochemiluminescence has almost no background.

At present, there are two important scientific problems in electrochemiluminescence.
One is the measurement and imaging of electrochemiluminescence signals at the weak or even single-molecule level.
The other is in the field of electrochemiluminescence imaging to achieve ultra-high space-time breakthroughs in the optical diffraction limit.
Resolution imaging, that is, super-resolution electrochemiluminescence imaging
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Scientific problem 1: Direct wide-field imaging of single molecules

　Scientific question 1: Direct wide-field imaging of　single molecules 　 Scientific question 1: Direct wide-field imaging of single molecules

　　For 3 years, Feng Jiandong's team has been devoted to the research of these two major problems
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To solve the first problem, the team used a self-made electrochemical measurement system with picoamp level current detection capability and a wide-field super-resolution optical microscope to build a set of efficient electrochemiluminescence control, measurement and imaging System

　　"It is difficult to capture single-molecule signals in the electrochemiluminescence process, mainly because single-molecule reactions are difficult to control, track, and detect
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The light, electrical, and magnetic signal changes accompanying single-molecule chemical reactions are very weak, and chemical reactions The process and location are random and difficult to control and track

　　In this way, they achieved direct wide-field imaging of single-molecule electrochemiluminescence reactions for the first time
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"Because it does not require light source excitation, the characteristic of this imaging is that the background is almost zero.

　　Scientific question 2: Breaking the limit of optical diffraction

　Scientific question 2: Breaking through the optical diffraction limit　Scientific question 2: Breaking through the optical diffraction limit

　　The first problem was solved, and they set out to solve the second problem
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Traditional optical microscopes work at scales of hundreds of nanometers or more, while high-resolution electron microscopes and scanning probe microscopes can reveal atomic scales

　　Inspired by fluorescence super-resolution microscopy, the research team used the optical reconstruction method of spatial molecular reaction positioning for imaging
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This is like when people look up at the stars at night, they can distinguish two stars that are very close by the "flicker" of the stars
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"The randomness of the chemical reaction is based on the positioning of the luminous position in space, and then the position information of the isolated molecular reaction in each frame is superimposed to construct
a'constellation ' of chemical reaction sites .
" Feng Jiandong said, in order to verify the imaging method For the feasibility and accuracy of the positioning algorithm, the team used micro-nano processing to create a stripe pattern on the electrode surface as a known imaging template, and compared it to imaging
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The results of single-molecule electrochemiluminescence imaging are structurally highly consistent with the results of electron microscopy imaging of the structure, which proves the feasibility of the imaging method
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Single-molecule electrochemiluminescence imaging has increased the spatial resolution of traditional electrochemiluminescence microscopy imaging of hundreds of nanometers to an unprecedented 24 nanometers, and the second scientific problem has also been solved
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　　The research team then applied the technology to microscopic imaging of biological cells
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Electrochemiluminescence imaging does not need to mark the cell structure, nor does it affect the cell state, so it is potentially friendly to cells
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The team used single-molecule electrochemiluminescence imaging on the cell's matrix adhesion to observe its dynamic changes over time
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The imaging results are compared with the fluorescence super-resolution imaging, which quantitatively shows a spatial resolution comparable to that of the fluorescence super-resolution microscope
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