Monitoring system and method for high-throughput imaging of electrochemical reaction of single nano individual

Abstract

The invention discloses a monitoring system and method for performing high-flux imaging on single nano individual electrochemical reaction, and the system is characterized in that a laser incident angle in an optical imaging module is above a total internal reflection angle, so that laser is irradiated on a working electrode through an imaging amplification device to generate an evanescent field; according to the system, an evanescent field is generated on the surface of the working electrode, only the nanometer individuals close to the surface of the electrode are illuminated, scattering interference of impurities in a solution is reduced, and the dynamic reaction process of the nanometer individuals is recorded. And the dynamic reaction process of the nano individual is recorded with high temporal-spatial resolution. The method has high resolution, high flux and real-time imaging capability, and can significantly improve the sensitivity and efficiency of nanoparticle electrochemical reaction analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical imaging, and in particular to a monitoring system and method for high-throughput imaging of electrochemical reactions of single nanoparticles. Background Art

[0002] Understanding the electrochemical behavior of nanomaterials at the individual level is critical to advancing the fields of catalysis, biosensing, and energy applications. However, the electron transfer process between nanomaterials and electrode surfaces, as well as the interactions between them, are complex, posing great challenges to studying their mechanisms. For example, single nanoparticle impact electrochemical (SNIE) measurements show that multiple current peaks occur during a single collision, indicating the presence of multiple motion modes and electrochemical activities. Although some theoretical models and machine learning methods have been developed to explain these complex current patterns, a fundamental challenge faced by these methods is the lack of imaging capabilities and spatial resolution, making it impossible to directly observe and correlate the electrochemical and motion behaviors of nanoparticles.

[0003] Imaging technology offers some solutions to this challenge, but some shortcomings remain: (1) Electrochemical scanning probe microscopy (SPM) can image the electrochemical properties of nanoscale samples with high spatial resolution, but due to its slow scanning speed, it is difficult to carry out large-scale and high-throughput detection.

[0004] (2) Optical techniques such as dark-field microscopy (DFM) provide sufficient spatial and temporal resolution by detecting scattered light from nano-objects, which is very useful for tracking their electrochemical reactions. However, since the scattering intensity decays with the sixth power of the particle diameter, its sensitivity decreases significantly for smaller nanoparticles.

[0005] CN108226095 A discloses an electrochemical impedance spectrum measurement device and method for a single nanoparticle, the device comprising: a monochromatic laser adjustment module, used to introduce monochromatic laser into dark field imaging and adjust the range of the single wavelength; a particle excitation module, connected to the monochromatic laser adjustment module, used to excite the scattering resonance of a single nanoparticle of a precious metal having a localized plasma resonance, comprising a plano-convex lens and an electrochemical cell; a voltage application module, connected to the particle excitation module, used to apply a periodic modulation voltage to the electrochemical cell; a particle scattering intensity detection module, connected to the voltage application module and the particle excitation module, comprising a phase-locked amplifier and a photomultiplier tube; the invention introduces monochromatic laser into dark field imaging, and in terms of the detector, the photomultiplier tube is equipped with a phase-locked amplifier, which makes it possible to obtain the electrochemical impedance spectrum of a single nanoparticle by directly detecting the change in the scattering intensity value of a single nanoparticle under voltage modulation.

[0006] CN111122552A discloses a method for monitoring cell secretion of copper ions using single-particle electrochemiluminescence imaging technology; an electrochemiluminescence microscopic imaging system is constructed, which can be used to observe the electrochemiluminescence of a single nanoparticle, achieving the spatial resolution of a single nanoparticle; at the same time, an electrochemiluminescence microscopic imaging sensor is constructed using graphite-like carbon nitride nanosheets, which can monitor the copper ions in the local micro-area of ​​the electrode; by monitoring the changes in the electrochemiluminescence intensity of a single graphite-like carbon nitride nanosheet around a single cell, the content of copper ions secreted by the cell is reflected in real time.

[0007] For nanomaterials with dynamic reactions and complex structures, it is more challenging to accurately analyze their electrochemical processes and movements because they have multiple reaction sites and more complex movements. Summary of the invention

[0008] The present invention aims to solve the problem that the electrochemical behavior of complex nano-individuals is difficult to characterize, and provides a high-throughput, high-precision single nano-individual real-time monitoring system. Based on the principle of total internal reflection interference scattering, the system can realize the real-time monitoring of the electrochemical behavior and microscopic motion of a single nano-individual on the electrode surface, and provide technical support for the mechanism research of complex electrochemical reactions at the nanoscale.

[0009] To achieve the above object, the technical solution adopted by the present invention is: A monitoring system for high-throughput imaging of electrochemical reactions of single nanoparticles, comprising an electrochemical module, an optical imaging module and a control module; The electrochemical module includes an electrochemical workstation and an electrochemical cell. The working electrode, reference electrode and counter electrode in the electrochemical cell are connected to the electrochemical workstation. The working electrode is a glass sheet with a conductive film. The optical imaging module includes a light source, a lens, a beam splitter, an imaging magnifying device, a light shielding sheet and an image acquisition device; The light source emits laser light, and the incident angle of the laser light is adjusted to be above the total internal reflection angle, so that the laser light is irradiated on the working electrode through the imaging amplification device to generate an evanescent field; the light shielding sheet is arranged at the rear focal plane of the imaging amplification device, and is used to block the reflected light and pass the scattered light, and the optical signal is collected by the image acquisition device; The control module is used to collect data signals from the image acquisition device and the electrochemical workstation, and to control the working parameters of the image acquisition device and the electrochemical workstation.

[0010] The system of the present invention generates an evanescent field on the surface of the working electrode, illuminating only the nano-individuals close to the electrode surface, reducing the scattering interference of impurities in the solution, and recording the dynamic reaction process of the nano-individuals (including nanoparticles and nanowires) with high temporal and spatial resolution. The light shield selectively blocks the strong reflected light, allowing only the scattered light of the nano-individuals to be Es and scattered light caused by the roughness of the electrode surface E b By using the principle of interference between the two, the imaging contrast and sensitivity are enhanced. Finally, according to the light signal (image) collected by the image acquisition device, the change of the intensity of the nano-individual in each frame of the image over time is analyzed, the reaction rate of the single body is calculated, and the corresponding current signal is derived according to the relationship between the image intensity and the particle size, thereby characterizing the dynamic behavior of the nano-individual in the electrochemical reaction.

[0011] This principle is based on E s and E b The interference that occurs, formula (3) is:

[0012] in I is the optical signal intensity of a single nano-entity collected by the image acquisition device, is the phase difference between the two scattered fields, It is the interference scattering term, which contributes the most to the signal and plays a dominant role.

[0013] The shading sheet includes a supporting frame and a blocking sheet fixed inside the frame, the blocking sheet is used to block reflected light, and a passage for scattered light is provided between the blocking sheet and the supporting light frame; the blocking sheet is made of low light transmittance material, such as metal plates (anodized aluminum, etc.), plastic plates (polyethylene, polypropylene, polyvinyl chloride, etc.), wooden boards, etc.; the material of the blocking sheet must have low light transmittance, and its surface is unlikely to scatter and reflect.

[0014] The method for preparing the shading sheet includes CNC machining. The shapes of the shading sheet and the blocking sheet are not limited to the shapes in this patent. Any shape that can be adapted to a microscope and can selectively block reflected light and allow scattered light to pass through can be applicable.

[0015] The reference electrode is one or more commonly used reference electrodes such as silver / silver chloride, saturated calomel electrode, etc., and the counter electrode is one or more electrodes such as platinum wire, carbon electrode, etc.; the working electrode is a glass sheet coated with ITO film or a glass sheet with other conductive coatings (such as gold, platinum, etc.); the three-electrode system can apply precise voltage to stimulate and control the electrochemical reaction of a single nano-individual.

[0016] The light source is laser or other monochromatic light source.

[0017] The depth of the evanescent field is within 300 nm; the illumination area is above 200 μm×200 μm, achieving total internal reflection illumination with a large field of view, and the electrochemical reaction processes of hundreds of nanoparticles can be monitored simultaneously.

[0018] The image acquisition device is one or more of a high frame rate CMOS camera and a CCD camera, ensuring that the movement trajectory of the nanoparticles and the change in interference scattering intensity during the reaction process can be accurately recorded.

[0019] The present invention also provides a monitoring method for high-throughput imaging of electrochemical reactions of single nanoparticles, which is performed using the monitoring system and comprises the following steps: Step S1, depositing nano-individuals on the working electrode, and adding a reaction solution into the electrochemical cell; Step S2, adjusting the incident angle of the light source so that the light source generates an evanescent field on the working electrode after passing through the imaging amplification device, using a light shielding sheet disposed on the rear focal plane of the imaging amplification device to block the reflected light in the electrochemical cell from passing through the scattered light, and collecting the optical signal of the nano-individual through the image acquisition device; starting the electrochemical workstation to apply a potential to the three electrodes to make the nano-individual react; Step S3, calculating the electrochemical signal of a single nano-individual according to the optical signal collected by the image acquisition device, so as to realize the dynamic behavior monitoring of the nano-individual in the electrochemical reaction.

[0020] The nano-entities include nanoparticles or nanowires, such as silver nanoparticles (AgNPs) or nanowires (AgNWs), or nanoparticles modified with chemical functional groups.

[0021] When the nano-individual is a nanoparticle, the optical signal in step S3 calculates the electrochemical signal of a single nano-individual according to formula (1), using the optical intensity of a single nanoparticle collected by the image acquisition device. I , calculate different t The current of a single nanoparticle at this moment i : (1) in is the density of nanoparticle x, is the mass of a single x nanoparticle, k is a constant of 2.6; When the nano-individual is a nanowire, the optical signal in step S3 calculates the electrochemical signal of a single nano-individual according to formula (2), using the optical intensity of a single nanowire collected by the image acquisition device: I , calculate different t Current of a single nanowire at a given moment i ; (2) When the nano-individual is a nanowire, the optical intensity of the entire nanowire or the optical intensity at any position on the nanowire may be collected, and the corresponding current may be the current of the entire nanowire or any position on the nanowire.

[0022] The optical signals collected include the time-varying signals of the interference scattering intensity of the nano-individuals and the time-varying motion signals of the spatial positions of the nano-individuals. The optical signals are the collected optical images. Therefore, the specific applications of the monitoring method described in the present invention include: (1) Dynamic electrochemical reaction monitoring of nanoparticles: The movement rate of nanoparticles is calculated through optical imaging, which is used to track the movement of individual nanoparticles on the electrode surface with high resolution. At the same time, the current generated during the electrochemical reaction is analyzed through its interference scattering intensity, and the correlation between movement and current is analyzed.

[0023] (2) Characterization of heterogeneous nanomaterial behavior: used to analyze the heterogeneous behavior of nanomaterials of different sizes, shapes or surface modifications during electrochemical reactions, revealing the differences in reaction characteristics caused by differences in movement patterns, adhesion strength and electrochemical activity of different particles.

[0024] (3) Nanowire dissolution reaction monitoring: used to track the reaction process of one-dimensional nanomaterials (such as nanowires) on the electrode surface, analyze their dissolution pattern and mechanism, and the impact of the interaction between nanowires on the reaction.

[0025] Compared with the prior art, the present invention has the following beneficial effects: The nano-individual electrochemical imaging system of the present invention has high resolution, high throughput and real-time imaging capabilities, which can significantly improve the sensitivity and efficiency of nanoparticle electrochemical reaction analysis. Moreover, while the nanoparticles are reacting, their microscopic motion can be tracked and analyzed to reveal the complex interaction between the nanoparticles and the electrode interface. Ultimately, the relationship between electrochemical reactions and microscopic motions is established, providing a powerful tool for the dynamic measurement of electrochemical behavior. This method can be applied to the study of the reactivity of nanomaterials in the fields of catalysis, energy storage and biosensing, and can be further expanded to more complex nanostructures and two-dimensional material systems.

[0026] The system and method of the present invention are suitable for monitoring the electrochemical reaction behavior of single nanoparticles and nanowires on the electrode surface, and can be used in the following fields: (1) Catalyst performance research: Analyze the changes in the electrochemical active area of ​​nanoparticles during the catalytic process to provide data support for improving catalyst activity; (2) Evaluation of the electrochemical properties of battery materials: used to study the dissolution, corrosion and deposition behavior of nanoparticles in battery materials, which helps to improve the stability and performance of battery materials; (3) Analysis of the mechanism of interaction between nanomaterials and surfaces: By tracking the movement path and dissolution rate of nanoparticles, we conduct in-depth research on their kinetic behavior of surface attachment, providing basic data for optimizing the application of nanomaterials in the fields of energy, sensing, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A is a schematic diagram of the system structure of the device of the present invention; Figure 1 B is a schematic diagram of the structure of the light shielding sheet 23 in the system; Figure 1 C in the figure is the optical field image acquired by the image acquisition device in Example 1. Each bright spot in the figure is a 30 nm AgNP, and the scale is 20 µm.

[0028] Among them, 11 is an electrochemical workstation, 12 is an electrochemical cell, 13 is a working electrode, 21 is a light source, 22 is an imaging amplification device, 23 is a shading sheet, 24 is an image acquisition device, and 31 is a control module; 1 is a blocking sheet, 2 is a scattered light path, and 3 is a supporting frame.

[0029] Figure 2 A in the middle shows four representative images of an AgNP from falling to the surface until oxidative dissolution in Example 1 (scale bar 0.5 µm); Figure 2 B is Figure 2 The optical intensity of the AgNP reaction process in A ( I ) over time ( t )’s changing image; Figure 2 C is composed of Figure 2 Where B is converted into the current-time of AgNP by formula (1) i - t )image; Figure 2 D in the middle is the position image of AgNP at each moment obtained by tracking; Figure 2 Where E is the AgNP movement rate - current ( vi ) Relationship images; Figure 2 Where F is current-time ( i - t )The speed statistics of the four stages in the figure; Figure 2 (G) is the velocity statistics of 20 random AgNPs in four current stages.

[0030] Figure 3 A is a statistical diagram of the ratio of the unmodified AgNPs and the AgNPs with different groups functionalized on the surface reacting on ITO in Example 2; Figure 3 Middle B is four snapshots of the collision and oxidation process of a surface amino-functionalized AgNP (AgNP-NH2) onto the ITO surface (scale bar is 1 µm); Figure 3 C is Figure 3 The optical intensity change diagram of AgNP-NH2 from approaching to contacting ITO until the reaction is completed in B; Figure 3 D in the middle is the position image of AgNP-NH2 at each moment obtained by tracking; Figure 3The E in the Figure 3 Where C is the current-time calculated by formula (1) i - t )image; Figure 3 F is Figure 3 AgNP-NH2 movement rate-current ( vi ) Relationship images; Figure 3 G is the movement rate of unmodified AgNP, AgNP functionalized with streptavidin (AgNP-SA), and AgNP-NH2 ( v ) and the peak current when the reaction occurs ( i p )、Current peak width( i w ) and current peak area ( i A ) comparison statistics.

[0031] Figure 4 A is an optical imaging image of a uniformly reacted silver nanowire (AgNW) in Example 3 at different times; Figure 4 B is Figure 4 Three different parts of AgNW in Figure A (in Figure 4 1-3 marked in A), and the intensity change diagram of the entire AgNW during the reaction process; Figure 4 C is composed of Figure 4 The current-time of different parts of AgNW obtained by converting B into formula (2) i - t )picture.

[0032] Figure 5 A is an optical image of an AgNW in Example 3 in which one end reacts before the other end; Figure 5 B is Figure 5 Current-time of different parts during the reaction of AgNW in A ( i - t )picture; Figure 5 Center C is an optical imaging image of an AgNW whose two ends react before the center; Figure 5 D is Figure 5 Current-time of different parts of AgNW during the reaction process in C ( i - t )picture.

[0033] Figure 6 This is an optical imaging diagram of an AgNW in motion accompanied by reaction in Example 3 and a schematic diagram of the reaction principle.

[0034] Figure 7 A in the middle is the optical imaging picture of AgNW where five reactions and interactions are carried out together; Figure 7B is Figure 7 Current-time during the reaction of 5 AgNWs in A ( i - t )picture. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0036] like Figure 1 As shown in A, a system for performing high-throughput imaging of electrochemical reactions of single nanoparticles or nanowires includes an electrochemical module, an optical imaging module, and a control module; The electrochemical module includes an electrochemical workstation 11 and an electrochemical cell 12. The working electrode 13, the silver / silver chloride reference electrode and the platinum wire counter electrode in the electrochemical cell 12 are connected to the electrochemical workstation 11. The working electrode 13 is an ITO glass sheet and is disposed at the bottom of the electrochemical cell 12. The optical imaging module includes a light source 21, a lens, a beam splitter, an imaging magnifier 22, a shading sheet 23 and an image acquisition device 24; the light source 21 emits a laser, and the incident angle is adjusted by adjusting the position of the light source relative to the lens, so that the laser is irradiated on the working electrode 13 through the imaging magnifier (objective lens) 22 to generate an evanescent field, and the field of view of the evanescent field can reach 200μm×200μm.

[0037] The structural schematic diagram of the light shielding sheet 23 is as follows Figure 1 As shown in B, it is arranged at the rear focal plane of the imaging magnifying device 22, and is used to block the reflected light in the electrochemical cell 12, while allowing most of the scattered light to pass through, and the scattered light signal is collected by the image acquisition device 24; The light source is a laser or other monochromatic light source with a light intensity of 5 mW. The image acquisition device 24 is a high frame rate CMOS camera with a frame rate of at least 100 frames per second, and the positioning accuracy of the center of mass of the nanoparticles reaches 2.4 nm; The control module 31 is used to collect data signals from the image acquisition device 24 and the electrochemical workstation 11 , and to control the working parameters of the image acquisition device and the electrochemical workstation.

[0038] The method for preparing the light shielding sheet is as follows: Figure 1The drawing shown in B is drawn and produced by CNC machining. The material of the blocking sheet is anodized aluminum. The shape of the blocking sheet is not limited to the shape in the specific embodiment of the present invention. Any shape that can adapt to the microscope and can selectively block reflected light and allow scattered light to pass through can be applicable. The material of the blocking sheet is not limited to anodized aluminum. Any material that can effectively block light from passing through can be applicable.

[0039] During the experiment, the optical image of the nanoparticles or nanowires is collected by the image acquisition device 24 to obtain an image sequence of the electrochemical reaction process. The electrochemical signal (current) is obtained by measuring and analyzing the scattering intensity of each nanoparticle or nanowire through the FIJI software, and converting the optical signal into a current signal quantitatively through formula (1) or formula (2); the nanoparticle motion signal (i.e., position change) is obtained by locating the center of mass of each frame of the image through the TrackMate plug-in in the FIJI software, thereby obtaining the speed information.

[0040] Example 1 Use Figure 1 The system shown in Figure A is used to image and analyze the electrochemical reactions of individual silver nanoparticles (AgNPs). Specifically, it includes: A glass sheet with an ITO coating was used as the working electrode and 1 M KSCN was used as the reaction solution in an electrochemical cell. Under the condition of applying 0.1 V (relative to Ag / AgCl reference) on the electrochemical workstation, 5 μL of 0.1 mg / mL aqueous solution of AgNP with a diameter of 30 nm was added to the KSCN solution. AgNPs continued to diffuse and collide with the ITO surface, and an oxidative dissolution reaction occurred: During this process, the scattering intensity of the AgNPs that fall onto the surface gradually weakens due to dissolution, and their position also shifts at the nanometer level due to interaction with the surface. The image acquisition device records the optical image of the entire process and synchronizes the optical signal and the electrical signal of the electrochemical workstation to the control module.

[0041] When the field of view of the system is 200 μm × 200 μm, the image captured by the image acquisition device is as follows: Figure 1 As shown in C, each bright spot is an AgNP. It can be seen that the system can image hundreds of single nanoparticles in each frame, achieve the measurement of about 1,000 single-particle reactions per second, and has the ability of high-throughput nanoparticle imaging.

[0042] like Figure 2 Figure A shows the dissolution process of a randomly selected single AgNP, including four representative optical images from the time it falls onto the ITO surface until the oxidative dissolution is completed. It can be seen that the AgNP undergoes an electrochemical dissolution reaction.

[0043] like Figure 2 B shows Figure 2 The optical intensity measured from the image sequence of a single AgNP in A during the process from approaching to contacting ITO until it is completely dissolved I The change over time ( It Curve). It can be seen that the interference scattering intensity of the AgNP increases when it approaches the ITO surface. After contact, the reaction begins, resulting in a continuous reduction in size, which leads to a corresponding decrease in intensity until the dissolution is completely restored to the baseline level.

[0044] According to the following formula from It The curve calculates the current at different times i :

[0045] in, is the density of Ag, is the mass of an Ag nanoparticle, is a constant, which is 2.6 in this patent. The calculation result is as follows Figure 2 The current-time ( i - t )picture.

[0046] According to the shape of the current peak, it can be divided into four stages: Figure 2 C in the middle is marked with different colors): (i) the pre-reaction stage, when the particles have not yet landed on the surface and the current is approximately zero; (ii) the current increase stage, when the reaction begins and continues until the maximum current is reached; (iii) the current decrease stage, when the current begins to decrease; (iv) the end stage, when the current drops to zero.

[0047] The optical images recorded by the image acquisition device can also extract the position change (i.e., speed) information of the AgNP reaction process, such as Figure 2 As shown in D. The center of mass of each frame of the image is located by using the TrackMate plug-in in the FIJI software to obtain the coordinates of the imaging plane [ x ( t ), y ( t )]. The equivalent rate can be calculated by the change of coordinates of the previous and next two frames. As shown in formula (4):

[0048] in is the difference between the horizontal coordinate position of AgNP in the next frame and the previous frame in the acquired image sequence. is the difference between the vertical coordinate position of AgNP in the next frame and the previous frame in the acquired image sequence. It is the time difference between the next frame image and the previous frame image.

[0049] Will Figure 2 The rate calculated by D is the same as that of Figure 2 Combined with the current data in C, we get Figure 2 Figure 5. The relationship between the movement rate of a single AgNP and the current shown in Figure 5 (E).

[0050] Will Figure 2 The data of E are statistically analyzed according to the above four stages, and the Figure 2 F. It can be seen that the four stages form different clusters, indicating that the current and speed are related differently in each stage. In particular, the rate is low in the current rising stage. This result indicates that low speed (i.e., when there is a strong interaction with the surface) is conducive to charge transfer.

[0051] The above conclusions are only drawn from a single AgNP. In order to further verify the universality of the conclusions, 20 random AgNPs were selected to calculate the average movement rate of the nanoparticles at each stage. The results are as follows: Figure 2 As shown in G. The results once again confirm that the charge transfer rate is fast when the movement rate is low.

[0052] Example 2 The same method as in Example 1 was used. Figure 1 The system shown in Figure A is used to image and analyze the electrochemical reactions of AgNPs modified with different molecules to further explore the effects of surface group modification on the electrochemical reactions, including: AgNPs functionalized with different groups were used, including amino-functionalized AgNPs with a diameter of 30 nm (AgNP-NH2), carboxyl-functionalized AgNPs with a diameter of 30 nm (AgNP-COOH), and streptavidin-functionalized AgNPs with a diameter of 60 nm (AgNP-SA).

[0053] Among them, the modification method of AgNP-NH2 and AgNP-COOH is as follows: take 500 μL of 0.1 mg / mL AgNPs solution, centrifuge at 16000 g for 2 minutes, and remove the supernatant. After washing with deionized water and centrifuging, add 1 mM HS-PEG-COOH or HS-PEG-NH2 aqueous solution to the centrifuge tube and incubate at room temperature overnight. After incubation, centrifuge at 16000 g and remove the supernatant. Rinse the particles with deionized water three times to remove unbound thiol molecules, and then dissolve in 500 μL water to obtain AgNP-COOH and AgNP-NH2. AgNP-SA was purchased from Nanjing Jicang Nanotechnology Co., Ltd.

[0054] Using ITO as the working electrode, 5 μL of surface functionalized 0.1 mg / mL AgNP solution was added to 1 MKSCN solution under an oxidation potential of 0.1 V (relative to Ag / AgCl reference). The image acquisition device recorded the image sequence during the reaction process.

[0055] The results are as follows Figure 3 As shown in Figure A, according to the collected images, it can be seen that the reaction activity of AgNPs with different modifications has decreased, because the modified molecular layer blocks the electron transfer. For unmodified AgNPs, 3786 out of 3928 AgNPs underwent electrochemical reactions (reaction ratio of 96.38%); while only 10 out of 1021 AgNP-NH2 particles underwent reactions (reaction ratio of 0.98%); the reaction ratios of AgNP-SA and AgNP-COOH were 1.45% and 0.00%, respectively.

[0056] Although most of the modified AgNPs did not react, those that did react (possibly due to incomplete blocking by the modified molecules) often exhibited different properties from those of the bare AgNPs. It curve. Figure 3 Figure B shows four images of the collision and reaction process of an AgNP-NH2.

[0057] Figure 3 Middle C shows Figure 3 The AgNP-NH2 in B moves from approaching to contacting ITO until the reaction is completed. It Figure 2. Changes of AgNPs compared with unmodified AgNPs. It picture( Figure 2 A comparison of (B) in the figure shows that their reaction modes are different. The reaction of AgNP-NH2 is a staged rapid reaction, while that of AgNP is a continuous slow reaction. This is because the presence of amino groups strengthens the interaction between particles and ITO, increasing the electron transfer rate.

[0058] Figure 3 D in the figure tracks the position of AgNP-NH2 at different times. According to formula (4), the movement rate of AgNP-NH2 at different stages can be calculated ( v ).

[0059] According to formula (1), Figure 3 Middle C It Curve transformation, we get Figure 3 As shown in E it Figure 2 shows the changes in current of a single AgNP-NH2 in four stages. Figure 3 F in the middle shows the current i with the velocity extracted from the particle motion vFrom the relationship between , it can be seen that the area with high electron transfer rate appears in the low-speed domain.

[0060] Figure 3 The statistical results of G show the movement rates of bare AgNP, AgNP-NH2 and AgNP-SA v There are significant differences, which is due to the different strengths of interaction with the ITO surface caused by different modifications. In addition, the height of the current peak ( i p ), current peak area ( i w ) and the current peak ( i A These results further demonstrate the important influence of the surface properties of nanoparticles on their electrochemical behavior and surface interactions.

[0061] Example 3 Use Figure 1 The system shown in Figure 1 is a high-resolution and high-throughput detection method for the electrochemical reaction of AgNWs. The specific steps include: after AgNWs are deposited on the ITO surface and 1M KSCN solution is added, a 0.5 V potential (relative to Ag / AgCl reference) is applied to trigger the reaction, and the optical image of AgNWs is recorded.

[0062] Figure 4 A in the figure shows the optical images of an AgNW at different times, reflecting its dissolution process. Figure 4 Figure B shows different parts of this AgNW. Figure 4 The optical intensity changes of three parts (numbered 1-3) are marked in A. The intensity changes of the three parts are synchronized with time, indicating that the AgNW has good contact with the surface during the reaction and is evenly dissolved.

[0063] Figure 4 C shows the corresponding current changes of different parts of the AgNW. The current ( i ) is calculated as:

[0064] in I is the optical signal intensity of AgNW in the image, t For time. Figure 4 Center C shows that the three partial currents are synchronized in time, again demonstrating that the AgNW reacts uniformly.

[0065] Figure 5 Figure A shows the reaction process of another AgNW. Figure 4 Different from A in the figure, the reaction of this AgNW is faster at one end than the other (as marked in the figure, the green end is faster than the red end). Figure 5Figure B shows the current signals at both ends changing with time (calculated by formula (2)), and it can be seen that their changes are not synchronous.

[0066] Figure 5 Figure C provides another reaction situation, where the two ends of the AgNW (marked in red and blue) react before the middle (marked in green). Figure 5 Figure D shows the change of the current signals of these three parts over time (calculated by formula (2)), which again shows the inconsistency of the response of different regions of a single AgNW. Figure 5 The two examples in the figure show that even in the same AgNW, there are still differences in reaction sites and reaction times. This cannot be reflected in traditional electrochemical measurements based on AgNW clusters, highlighting the advantages of this patented method.

[0067] Figure 4 and Figure 5 The AgNWs in the reaction were all adsorbed on the ITO surface as a whole, and there was no movement of the AgNWs during the entire reaction process. Figure 6 A reaction case of incompletely adsorbed AgNW is shown. One end of this AgNW is adsorbed on the surface of the ITO electrode, and the other end can swing freely. After applying a potential of 0.5 V (relative to the Ag / AgCl reference), the swinging free end is the first to dissolve. Since the free end is less likely to contact the electrode, it is inferred that this observation is due to directional electron transport in the nanowire: electrons are transported from the free far end through the nanowire to the fixed end, and then to the ITO electrode, completing the electron transfer and dissolution reaction.

[0068] Figure 7 A more complex example is shown: multiple AgNWs interact with each other during movement and trigger new dissolution reactions through the interactions. Figure 7 Figure A shows that by increasing the deposition density of AgNWs on ITO, an intertwined and overlapping AgNW situation is created (5 AgNWs are marked in the figure, numbered 1-5). After applying a potential of 0.5 V (relative to the Ag / AgCl reference), it is observed that AgNWs 1 and 2 react first, followed by AgNW 3. AgNW 4 is pressed under AgNW 3. When AgNW 3 dissolves, AgNW 4 moves violently, flipping from the left to the right (indicated by the arrow in the figure), and pressing on AgNW 5. Due to the force, AgNW 5 interacts more closely with the surface and dissolves rapidly. Finally, AgNW 4 is also dissolved. Figure 7 Figure B shows the current change of each AgNW reaction during the whole process. These results once again illustrate the unique advantages of this method in studying the interaction and electrochemical behavior of individual bodies in complex systems.

[0069] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A monitoring system for high-throughput imaging of electrochemical reactions of single nanoparticles, characterized in that: It includes an electrochemical module, an optical imaging module and a control module; The electrochemical module includes an electrochemical workstation and an electrochemical cell. The working electrode, reference electrode and counter electrode in the electrochemical cell are connected to the electrochemical workstation. The working electrode is a glass sheet with a conductive film. The optical imaging module includes a light source, a lens, a beam splitter, an imaging magnifying device, a light shielding sheet and an image acquisition device; The light source emits laser light, and the incident angle of the laser light is adjusted to be above the total internal reflection angle, so that the laser light is irradiated on the working electrode through the imaging amplification device to generate an evanescent field; the light shielding sheet is arranged at the rear focal plane of the imaging amplification device, and is used to block the reflected light and pass the scattered light, and the optical signal is collected by the image acquisition device; The control module is used to collect data signals from the image acquisition device and the electrochemical workstation, and to control the working parameters of the image acquisition device and the electrochemical workstation.

2. The monitoring system for high-throughput imaging of electrochemical reactions of single nanoparticles according to claim 1, characterized in that: The light shielding sheet comprises a supporting frame and a blocking sheet fixed in the frame, the blocking sheet is used to block reflected light, and a passage for scattered light is provided between the blocking sheet and the supporting light frame; the blocking sheet is made of a low light transmittance material.

3. The monitoring system for high-throughput imaging of electrochemical reactions of single nanoparticles according to claim 1, characterized in that: The reference electrode is one or more of silver / silver chloride and saturated calomel electrode; the counter electrode is one or more of platinum wire and carbon electrode; The working electrode is a glass sheet coated with an ITO film or a glass sheet containing a conductive coating.

4. The monitoring system for high-throughput imaging of electrochemical reactions of single nanoparticles according to claim 1, characterized in that: The light source is laser or other monochromatic light source.

5. The monitoring system for high-throughput imaging of electrochemical reactions of single nanoparticles according to claim 1, characterized in that: The depth of the evanescent field is within 300 nm; the illumination area is above 200 μm×200 μm.

6. The monitoring system for high-throughput imaging of electrochemical reactions of single nanoparticles according to claim 1, characterized in that: The image acquisition device is one or more of a high frame rate CMOS camera and a CCD camera.

7. A monitoring method for high-throughput imaging of electrochemical reactions of single nanoparticles, characterized in that: The method is carried out using the monitoring system according to any one of claims 1 to 6, comprising the steps of: Step S1, depositing nano-individuals on the working electrode, and adding a reaction solution into the electrochemical cell; Step S2, adjusting the incident angle of the light source so that the light source generates an evanescent field on the working electrode after passing through the imaging amplification device, using a light shielding sheet disposed on the rear focal plane of the imaging amplification device to block the reflected light in the electrochemical cell from passing through the scattered light, and collecting the optical signal of the nano-individual through the image acquisition device; Start the electrochemical workstation and apply potential to the three electrodes to make the nano-individuals react; Step S3, calculating the electrochemical signal of a single nano-individual according to the optical signal collected by the image acquisition device, so as to realize the dynamic behavior monitoring of the nano-individual in the electrochemical reaction.

8. The method for monitoring the electrochemical reaction of a single nanoparticle by high-throughput imaging according to claim 7, characterized in that: The nano-entities include nanoparticles or nanowires.

9. The method for monitoring the electrochemical reaction of a single nanoparticle by high-throughput imaging according to claim 8, characterized in that: When the nano-individual is a nanoparticle, the optical signal in step S3 calculates the electrochemical signal of a single nano-individual according to formula (1), using the optical intensity of a single nanoparticle collected by the image acquisition device. I , calculate different t The current of a single nanoparticle at this moment i : （1） in is the density of nanoparticle x, is the mass of a single x nanoparticle, k is a constant of 2.

6.

10. The method for monitoring the electrochemical reaction of a single nanoparticle by high-throughput imaging according to claim 8, characterized in that: When the nano-individual is a nanowire, the optical signal in step S3 calculates the electrochemical signal of a single nano-individual according to formula (2), using the optical intensity of a single nanowire collected by the image acquisition device: I , calculate different t Current of a single nanowire at a given moment i ; （2）。

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