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    Home > Research group of Professor Su bin of Zhejiang University: electrochemiluminescence self interference spectroscopy with nano scale vertical spatial resolution

    Research group of Professor Su bin of Zhejiang University: electrochemiluminescence self interference spectroscopy with nano scale vertical spatial resolution

    • Last Update: 2020-02-14
    • Source: Internet
    • Author: User
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    Lead electrochemiluminescence (ECL) is a kind of light signal induced by electrochemical reaction It is widely used in clinical diagnosis and immunoassay, with the advantages of high sensitivity, high selectivity and low background signal Vertical spatial resolution is very important for the study of ECL mechanism and the development of immunoassay based on ECL At present, there are few researches on longitudinal spatial resolution ECL, and the resolution is low Recently, Professor Su Bin's research group of Zhejiang University reported an electrochemiluminescence self interference spectroscopy (eclis) This method has a nano scale vertical spatial resolution The results were published in J am Chem SOC (J am Chem SOC 2020, 142, 1222-1226 Doi: 10.1021/jacs.9b12833) Brief introduction of Professor Su Bin's research group main research topics of Professor Su Bin's research group include single cell / single particle electrochemiluminescence microscopic imaging, quantum dot electrochemiluminescence mechanism and its immuno / molecular diagnosis application, anti pollution electrochemistry interface design and its single cell / in vivo analysis application, nanopore (membrane) biomimetic sensing and measurement, etc Prof Su bin, Professor of the Department of chemistry, Zhejiang University, director of the Institute of analytical chemistry, Zhejiang University He graduated from the Department of chemistry of Jilin University with a master's degree from Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, and a doctor's degree from Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland 2006-2009 postdoctoral research in EPFL In June 2009, he served as te ure tracked and independent PI doctoral supervisor in the Department of chemistry of Zhejiang University, and was promoted to Professor of Zhejiang University in January 2013 It is mainly engaged in the basic and applied research of Interface Electrochemistry, electrochemiluminescence analysis method and technology, micro and nano scale molecular separation and analysis, fingerprint trace inspection and imaging analysis Up to now, he has published more than 130 papers and has been granted 9 Chinese invention patents There are more than 30 graduate students, 18 of whom have graduated Cutting edge scientific research achievements: the self interference spectrum of electroluminescence with nanometer longitudinal spatial resolution is composed of silicon wafer (SiO2 / Si, figure 1a) covered with silicon dioxide film (about 6.2 μ m thick) as electrode substrate, and titanium layer with thickness of about 4.6 nm and gold layer with thickness of 11.8 nm are deposited on the film by electron beam evaporation The prepared electrodes are gold layer, titanium layer, silicon dioxide film and silicon substrate (Au / SiO2 / Si, FIG 1b) from top to bottom When light is incident on the SiO2 / Si or Au / SiO2 / Si electrodes, optical interference occurs between the reflected light from different interfaces, resulting in interference spectrum (Fig 1c and D, hollow circle) Many regular interference peaks can be observed in the interference spectrum The transfer matrix method can be used to simplify the SiO2 / Si or Au / SiO2 / Si electrode into a single equivalent interface and calculate the theoretical interference spectrum In the calculation of theoretical spectrum, the thickness of silicon dioxide film is the only unknown variable Change the thickness of the silicon dioxide film in the theoretical calculation process, so that the difference between the theoretical spectrum and the experimental spectrum is the smallest At this time, the thickness value used is the actual thickness of the silicon dioxide film (Fig 1c and D, black line) Therefore, the thickness of the film can be calculated by optical interference Figure 1 Scanning electron microscope cross section of SiO2 / Si (a) and Au / SiO2 / Si electrode (b) Experimental (hollow circle) and theoretical (black line) white light interference spectra of SiO2 / Si (c) and Au / SiO2 / Si electrodes (d) in air The scales in figures a and B are 10 μ m and 100 nm, respectively (source: J am Chem SOC.) in the ECL process, there will be interference between the light directly emitted by the molecule and the light reflected on the Au / SiO2 / Si electrode, thus forming the ECL self interference spectrum (Fig 2a) The experimental device is shown in Fig 2B The self interference spectra of monolayer ECL molecules fixed on the surface of Au / SiO2 / Si electrode were studied The derivatives of Ru (bpy) 32 + were fixed to the electrode surface with 3-mercaptopropionic acid and double stranded DNA molecules containing 50 base pairs, respectively After the potential is applied, several obvious interference peaks can be seen in the interference spectrum, which verifies the correctness of ECL self interference principle (Fig 3) Similarly, the theoretical ECL self interference spectrum can be calculated by the transfer matrix method and the two beam interference method In the calculation of theoretical spectra, the distance between Ru (bpy) 32 + molecule and electrode is the only unknown variable Different self interference spectra can be obtained by changing the distance When the difference between the theoretical spectrum and the experimental spectrum is the smallest, the value of the distance used in the theoretical spectrum is the correct value The distance between ECL molecule and electrode was calculated by this method Using 3-mercaptopropionic acid or double stranded DNA as linker, the calculated distances are 1.5 nm and 8.7 nm, respectively The former is close to the distance (1.28 nm) between ruthenium and sulfur calculated by chembio 3D software The latter is slightly smaller than the value reported in the literature (10.5 nm) This may be due to the interaction between DNA skeleton with negative charge and gold electrode with positive potential The results further prove the correctness of eclis theory, and prove that eclis has nano scale vertical spatial resolution Figure 2 Schematic diagram of the principle (left) and experimental device (right) of eclis (source: J am Chem SOC.) Fig 3 Schematic diagram of ECL molecule fixed on Au / SiO 2 / Si electrode surface by 3-mercaptopropionic acid (a) and double stranded DNA (c) containing 50 base pairs; (B, d) normalized ECL self interference spectrum obtained by using 3-mercaptopropionic acid (b) and DNA (d) as connecting molecules The thickness of the luminescent layer of Ru (bpy) 32 + / tpra (tri-n-propylamine) system was also studied by eclis The principle is as follows: 1) divide the whole luminescent layer into several ECL monolayers with equal spacing in the direction perpendicular to the electrode, and the distance between each layer and the electrode is different; 2) assume that the ECL light intensity decreases linearly in the direction perpendicular to the electrode; 3) the total ECL self interference spectrum is the superposition of all ECL monolayer self interference spectra When the difference between the calculated spectrum and the measured spectrum is the smallest, the distance between the ECL monolayer and the electrode furthest away from the electrode is the thickness of the light-emitting layer As shown in Fig 4, when the concentration of Ru (bpy) 32 + increases, the interference spectrum has obvious red shift and broadening This is because when the concentration of Ru (bpy) 32 + is greater than 0.1 mm, ECL is mainly catalytic pathway At this time, the thickness of the luminescent layer mainly depends on the distribution of Ru (bpy) 33 + Because Ru (bpy) 33 + is more stable than tpra radical and diffuses further, the thickness of luminescent layer is larger Under the condition of low concentration (1 μ m) and high concentration (1 mm) Ru (bpy) 32 +, the thickness of the luminescent layer is about 350 ~ 450 nm and 800 ~ 950 nm, respectively, which is less than the value reported in the literature This may be due to the low sensitivity of the spectrometer, resulting in ECL far away from the electrode surface area being too weak to be detected Figure 4 Normalized ECL self interference spectrum measured by Au / SiO 2 / Si electrode in 1 μ m Ru (bpy) 32 + / 60 mm tpra (black line, spectral integration time 2 s) and 1 mm Ru (bpy) 32 + / 30 mm tpra (red line, spectral integration time 0.5 s) solution; 0.2 M phosphate buffer (pH 7.4) with applied potential of + 1.2 V (source: J am Chem SOC )To sum up, for the ECL monolayer fixed on the electrode surface, the distance between the monolayer and the electrode can be measured by eclis And the method has several nanometer vertical spatial resolution For the ECL of the solution phase, the thickness of the luminescent layer on the electrode surface can be measured by eclis This method can distinguish the different thickness of ECL luminescent layer in different reaction paths This work provides a new way for the study of longitudinal spatial resolution of ECL This work was recently published in J am Chem SOC (J am Chem SOC 2020, 142, 1222-1226 Doi: 10.1021/jacs.9b12833) under the title of "electrochemically self-interference spectrum with vertical nanoscale resolution" The first author is Dr Wang Yafeng, and the corresponding author is Professor Su bin, Qian Yang, and Bin Su )。 The preparation and characterization of Au / SiO2 / Si electrodes are supported and assisted by the shared service platform of the Department of optoelectronics, Zhejiang University, the micro nano processing center of Zhejiang University and the analytical and testing platform of the Department of chemistry, Zhejiang University The research work was supported by the National Natural Science Foundation of China (21874117, 21575126) and the natural science foundation of Zhejiang Province (lz18b050001) Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information website, chembeangoapp, chembeango official micro blog, CBG information wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the representative research groups in China, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit  
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