A method for measuring the particle size of single particles

Abstract

The present application relates to a kind of single particle particle size measurement method, belong to particle size measurement technical field.The single particle particle size measurement method provided by the present application, comprising the following steps: (1) the capillary glass tube after pretreatment is drawn into the micro-nano glass tube with micro-nano tip;(2) water phase solution is injected into the micro-nano glass tube obtained in step (1), and silver wire plated with AgCl is inserted into the micro-nano glass tube, to obtain working electrode;(3) Ag / AgCl electrode and the working electrode obtained in step (2) are inserted into electrolytic cell containing oil phase solution, then put into electrostatic shielding box, and measure steady-state current;(4) add the particle to be measured to the water phase solution, measure the steady-state current after collision, and the particle size of the particle to be measured is calculated according to formula.The measurement method of the present application overcomes the problems of traditional solid micro-nano electrode, such as greater difficulty in preparation, lower surface reproducibility and poorer controllability of collision.

Description

Technical Field

[0001] This invention belongs to the field of particle size measurement technology, and specifically relates to a method for measuring the size of a single particle. Background Technology

[0002] For the past few decades, electron microscopy methods (such as scanning electron microscopy and transmission electron microscopy) have been the primary means of measuring individual entities (e.g., cells, vesicles, nanoparticles, molecules, or atoms). Subsequently, high-resolution spectroscopic methods have emerged, such as surface-enhanced Raman spectroscopy, surface plasmon resonance imaging, infrared nanospectroscopy, and single-molecule fluorescence microscopy. While these methods offer impressive results, they place high demands on experimental equipment, research subjects, and even the instrument users, inevitably increasing the time and economic costs of research. Furthermore, spectroscopic methods are often limited to specific molecules; for example, single-molecule fluorescence microscopy requires the product (or reactant) to exhibit fluorescence; lasers can cause photobleaching and autofluorescence problems; and non-single-molecule fluorescence microscopy is limited by the diffraction limit. Therefore, there is a lack of efficient, inexpensive, and universally applicable characterization techniques for measuring individual entities.

[0003] Single-particle collision electrochemistry avoids the holistic, average effects of existing technologies, helping to isolate unique individuals from the whole. Understanding the performance of individual entities in industrial nanoparticle catalysts—that is, identifying champion or spectator nanoparticles—allows for precise modulation and promotion of the overall reaction, and can deepen our understanding of fundamental chemistry (or biology / physics / materials science). Single-particle collision electrochemistry has developed rapidly over the past two decades, and three main measurement modes are currently commonly used: "blocking," "electrocatalytic amplification," and "holistic electrolysis." These three measurement modes are constantly being improved and have been widely applied in the field of electroanalytical chemistry.

[0004] The "blocking" mode involves placing a solid micron or nanometer working electrode in a solution containing an electroactive material. Under constant potential, the steady-state current resulting from the diffusion-controlled oxidation or reduction reaction of the electroactive material can be observed. When extremely dilute concentrations of electrochemically inactive (or inert) particles, such as micro / nano-scale carboxyl rubber particles, are added, the particles randomly collide with the electrode surface due to Brownian motion and / or electric field attraction. This reduces the actual surface area of ​​the working electrode due to the adsorption and occupation of the inert particles, causing a significant drop in current that exhibits a stepped shape, with each step representing a collision event. Furthermore, researchers found that the time interval between collision events is inversely related to the solution concentration. By using the height of the current drop, the size of the inert particles can be calculated, and they found that the electrochemical measurements do not deviate significantly from the actual particle size. However, existing single-particle collisional electrochemistry in the "blocking" mode has significant drawbacks: ① The fabrication of submicron and nanoscale solid electrodes is difficult and cumbersome, requiring complex pretreatment steps such as polishing (e.g., FIB), and daily maintenance necessitates anti-static measures; measuring nanoscale single particles requires the use of submicron and nanoscale solid electrodes; ② The reproducibility of solid electrode surfaces is low, leading to errors in electrochemical measurement signals; ③ The controllability of particle-solid electrode collisions is poor, especially in the case of elastic collisions. The use of solid micro / nano working electrodes requires cumbersome electrode pretreatment such as polishing and cleaning, and the relatively poor reproducibility of electrode surfaces limits its practical application. Furthermore, if a single particle is small compared to the area of ​​the entire working electrode (commercially available gold, platinum, and carbon fiber ultramicroelectrodes with diameters of 10 or 25 micrometers), some minute electrical signals are masked by noise and cannot be identified, causing deviations in the results and resulting in a poor signal-to-noise ratio.

[0005] Therefore, it is of great significance to develop a single-particle size measurement method that is easy to prepare, has high surface reproducibility, and good collision controllability. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for measuring the particle size of a single particle.

[0007] This invention is achieved through the following technical solution:

[0008] This invention provides a method for measuring the size of a single particle, comprising the following steps:

[0009] (1) The pretreated capillary glass tube is drawn into a micro-nano glass tube with micro-nano tips;

[0010] (2) Inject an aqueous solution into the micro / nano glass tube obtained in step (1), and then insert a silver wire coated with AgCl into the micro / nano glass tube to obtain a working electrode; the aqueous solution includes a water-soluble redox couple;

[0011] (3) Insert the Ag / AgCl electrode and the working electrode obtained in step (2) together into an electrolytic cell containing an oil phase solution, and then place them in an electrostatic shielding box to measure the steady-state current; the oil phase solution includes an electron acceptor compound or an electron donor compound, and the electron acceptor compound includes at least one of 5,6,11,12-tetraphenylbenzotetraphenyl and 7,7,8,8-tetracyanobenzoquinone dimethyl ether;

[0012] (4) Add the test particles to the aqueous solution, measure the steady-state current after collision, and calculate the particle size of the test particles according to the formula:

[0013]

[0014] In the formula, r p Let r be the radius of the particle to be measured. pipet i is the inner radius of the micro / nano glass tube described in step (1). ss The steady-state current described in step (3), Δi ss The difference between the steady-state current after the collision described in step (4) and the steady-state current in step (3) is given.

[0015] This invention involves drawing capillary glass tubes to obtain micro / nano glass tubes. When filled with an aqueous solution, these tubes form a physically and mechanically stable working electrode—a micro / nano liquid / liquid interface—with an immiscible oil solution outside the tube. This micro / nano liquid / liquid interface is an oil / water molecular interface, a molecularly smooth soft interface, thus exhibiting excellent reproducibility of electron transfer signals. The micro / nano liquid / liquid interface is polarized by the ion distribution on both sides, forming a very strong electric field. By changing the polarity, the adsorption and desorption of charged particles at the interface can be easily controlled. When a single micro / nano-scale entity at an extremely low concentration collides with the micro / nano liquid / liquid interface, a transient change in the interfacial electron transfer current, such as a current step, occurs, enabling single-particle level measurement of the test particle. This technique records the transient current changes using a constant potential (it) image. This invention utilizes micro / nano glass tube electrodes to support the liquid / liquid molecular interface. A micro / nano liquid / liquid interface collision platform is employed to measure bimolecular heterogeneous electron transfer at the collision-blocking interface of a single particle. This reduces the interface area due to the inert particle's presence, resulting in a significant decrease in current and a discrete, stepped shape, with each step representing a collision event. By analyzing these stepped signals and using formulas, the size of the inert particle under test can be determined. Furthermore, because the analyte particle is suspended within the tube, and the electroactive substances undergoing electron exchange at the interface in the solution primarily diffuse linearly in a semi-infinite manner, the radial distribution of diffusion flux has minimal impact, thus weakening the "edge effect" and significantly improving the accuracy of micro / nano particle size measurement.

[0016] Preferably, the electron donor compound includes at least one of a metallocene compound, 5,6,11,12-tetraphenylbenzotetrabenzene, and 7,7,8,8-tetracyanobenzoquinone dimethylethane; the metallocene compound includes at least one of ferrocene or decamethylferrocene.

[0017] Preferably, in step (1), the pretreatment method is as follows: the capillary glass tube is soaked in piranha solution, washed with water until the washing solution is neutral, and dried to obtain the pretreated capillary glass tube.

[0018] Preferably, in step (2), the water-soluble redox couple is a hydrophilic and oleophobic redox couple.

[0019] In a preferred embodiment of the single-particle size measurement method of the present invention, in step (2), the water-soluble redox couple is Fe(CN)6. 3- / Fe(CN)6 4- .

[0020] In a preferred embodiment of the single-particle size measurement method of the present invention, in step (2), the Fe(CN)6 in the aqueous solution... 3- With the Fe(CN)64- The concentration ratio is (1-10):(1-10); preferably, the Fe(CN)6 3- With the Fe(CN)6 4- The concentration ratio is 1:10 or 10:1; more preferably, the Fe(CN)6 3- Or the Fe(CN)6 4- The concentration should not exceed 10 mmol / L. If the concentration is too high, it will cause particle aggregation, resulting in inaccurate measurement results.

[0021] In a preferred embodiment of the single particle size measurement method of the present invention, in step (2), the aqueous solution further includes an aqueous electrolyte, which is a soluble chloride salt.

[0022] Preferably, the soluble chloride salt includes at least one of NaCl, LiCl, and KCl.

[0023] In a preferred embodiment of the single-particle size measurement method of the present invention, in step (3), the concentration of the electron acceptor compound or electron donor compound in the oil phase solution is 0.1 mmol / L-2 mmol / L.

[0024] Preferably, the concentration of the electron acceptor compound or electron donor compound in the oil phase solution is 0.2 mmol / L.

[0025] Preferably, the electron acceptor compound or electron donor compound is 5,6,11,12-tetraphenyltetraphenyl.

[0026] In a preferred embodiment of the single-particle size measurement method of the present invention, in step (3), the oil phase solution further includes an oil phase electrolyte, which is ammonium bis(triphenylphosphine)tetra(pentafluorophenyl)borate (BATB) or ammonium tetra(dodecyl)tetra(pentafluorophenyl)borate (TDDATB). Adding an oil phase electrolyte can improve the conductivity of the oil phase and can also be used to polarize the liquid / liquid interface. Studies have shown that both of these oil phase electrolytes can ensure good conductivity of the oil phase solution and polarize the liquid / liquid interface.

[0027] In a preferred embodiment of the single particle size measurement method of the present invention, in step (3), the concentration of the oil phase electrolyte in the oil phase solution is 5 mmol / L-20 mmol / L.

[0028] Preferably, in step (3), the solvent of the oil phase solution is an organic solvent that is insoluble in water and has a different density.

[0029] Preferably, the solvent of the oil phase solution is 1,2-dichloroethane.

[0030] In step (3) of this invention, the assembled measurement system is placed in an electrostatic shielded box, and then the experimental parameters are set on the software of an electrochemical workstation (such as CHI760E). The steady-state current is measured, specifically by using cyclic voltammetry to determine the potential of the steady-state current plateau that achieves electron transfer; the chronoamperometry (i.e., the it curve) is measured at this potential; the chronoamperometry is measured before and after the addition of particles to determine the change in steady-state current, which is used to calculate the particle size.

[0031] In a preferred embodiment of the single particle size measurement method of the present invention, in step (4), the ratio of the inner diameter of the micro / nano glass tube to the diameter of the particle to be measured is (3-10):1.

[0032] The inventors discovered through research that the measurement results are better when the inner diameter of the micro / nano glass tube is 3-10 times the diameter of the particle to be measured.

[0033] In a preferred embodiment of the single particle size measurement method of the present invention, in step (4), the particle to be measured is an insulating particle or a semiconductor particle.

[0034] In a preferred embodiment of the single-particle size measurement method of the present invention, in step (4), the concentration of the particle to be measured in the aqueous solution is 10. -15 mmol / L-10 -12 mmol / L.

[0035] Preferably, the aqueous solution comprises sodium chloride, potassium ferricyanide, and potassium ferrocyanide, wherein the concentrations of NaCl, potassium ferricyanide, and potassium ferrocyanide are 10 mmol / L; or the concentrations of NaCl, potassium ferricyanide, and potassium ferrocyanide are 10 mmol / L.

[0036] Preferably, the oil phase solution is a 1,2-dichloroethane solution containing 5 mmol / L ammonium bis(triphenylphosphine)tetra(pentafluorophenyl)borate (BATB) and 0.2 mmol / L 5,6,11,12-tetraphenyltetraphenyl (RB).

[0037] When the above-mentioned aqueous and oil phase solutions are used, under a sufficiently negative potential, potassium ferrocyanide in the aqueous phase solution is oxidized and loses electrons, which are then transferred into the oil phase. The electron acceptor compound RB in the oil phase gains electrons and is reduced to the free radical anion RB. ·-When the test particles, such as 10 pM or 50 pM polystyrene microspheres, are added to the aqueous phase, the polystyrene microspheres are attracted and collide with the interface when a negative potential is applied to the aqueous phase. This hinders the transfer of electrons from the aqueous phase to the oil phase, resulting in a step-like signal with decreasing current on the it curve. Each step-like shielding signal represents a polystyrene microsphere collision event. The size of the polystyrene microspheres can be calculated using a formula. By statistically analyzing all the signals and comparing the results with the size distribution information of polystyrene microspheres measured by a laser particle size analyzer, the results are in good agreement, indicating that the measurement results obtained by this method are reliable and accurate.

[0038] This invention offers the following advantages: The measurement method utilizes micro / nano glass tube electrodes to support the liquid / liquid molecular interface, overcoming the challenges of traditional solid-state micro / nano electrodes, such as difficult fabrication, low surface reproducibility, and poor collision controllability. It also significantly reduces the interface charging current and the high ohmic drop of organic solvents. Since the analyte particles are suspended within the tube, and the electroactive substances undergoing electron exchange at the interface in the solution are primarily subject to semi-infinite linear diffusion, the radial distribution of diffusion flux has minimal impact, thus weakening the "edge effect" and greatly improving the accuracy of micro / nano particle size measurement. Furthermore, this method boasts advantages such as simple operation, low cost, and high throughput (e.g., forming micro / nano liquid / liquid interface arrays on chips), making it a promising new and universal method for measuring the size of non-conductive micro / nano particles. Attached Figure Description

[0039] Figure 1 This is a schematic diagram illustrating the principle of the measurement method of the present invention;

[0040] Figure 2 The image shows the current-time curve and its detailed magnification of the shielding effect at the water / 1,2-dichloroethane interface after adding 50 pM polystyrene nanoparticles to an aqueous solution in Example 1.

[0041] Figure 3 The bar chart shows the particle size distribution of 50 pM polystyrene microspheres measured in Example 1, as well as the dynamic light scattering (DLS) analysis results of the polystyrene microspheres in deionized water and the aqueous solution of Example 1.

[0042] Figure 4 Example 2 shows the current-time curve and its detailed magnified image of the shielding effect at the water / 1,2-dichloroethane interface after adding 50 pM polystyrene nanoparticles to the aqueous solution.

[0043] Figure 5 The bar chart shows the particle size distribution of 50 pM polystyrene microspheres obtained in Example 2, as well as the DLS analysis results of the polystyrene microspheres in deionized water and the aqueous solution of Example 2.

[0044] Figure 6 Example 3 shows the current-time curve and its detailed magnified image of the shielding effect at the water / 1,2-dichloroethane interface after adding 10 pM polystyrene nanoparticles to the aqueous solution.

[0045] Figure 7 The bar chart shows the particle size distribution of the 10 pM polystyrene microspheres obtained in Example 3, as well as the dynamic light scattering (DLS) analysis results of the polystyrene microspheres in deionized water and the aqueous solution of Example 3. Detailed Implementation

[0046] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0047] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0048] Example 1

[0049] A method for measuring the size of a single particle is as follows:

[0050] 1. Cleaning, drawing, and characterization of micro / nano glass tubes

[0051] Immerse the borosilicate glass capillary in a piranha solution for one hour. Then, place the capillary in a beaker filled with ultrapure water and continue immersing for at least twelve hours. After this process, remove the capillary and rinse the inner and outer walls of the glass tube with plenty of ultrapure water to ensure that any remaining solution is thoroughly removed. Next, place the capillary in a clean beaker and add ultrapure water until it is submerged. After standing for several minutes, remove a small portion of the ultrapure water from the beaker and measure its pH value using a pH meter. When the pH value is within the neutral range, it can be determined that the capillary has been cleaned. Finally, place the capillary in a vacuum drying oven to dry it for later use. Using a PC-100 programmable vertical glass tube drawing machine (PC-100 drawing machine for short), the pre-treated capillary glass tube is drawn according to the parameters set in the process. The pre-treated capillary glass tube is placed and fixed on the instrument. When the gravity drawing reaches the critical tolerance value of the glass, one glass tube will be drawn into two relatively consistent micro-nano glass tubes with micro-nano tips. The prepared micro-nano glass tubes are characterized using a metallographic microscope and a scanning electron microscope, and then placed in an electrode box for later use.

[0052] 2. Synthesis of the oil-phase electrolyte bis(triphenylphosphine)tetra(pentafluorophenyl)borate ammonium (BATB)

[0053] BATB was prepared according to the literature doi.org / 10.1002 / asia.202200731. The specific steps are as follows: Weigh 3.2674 g of lithium tetra(pentafluorophenyl)borate·diethyl ether complex (LiTB·2.5C4H) 10 O) and 2.1526 g of bis(triphenylphosphine)ammonium chloride (BACl) solid powder were dissolved in 75 mL of methanol / water solution (methanol to ultrapure water volume ratio of 2:1). The solution containing LiTB·2.5C4H 10 A methanol / water solution of O was added dropwise to a methanol / water solution containing BACl using a dropper to initiate a metathesis reaction, with continuous stirring using a glass rod. After the reaction was complete, the product was filtered using ultrapure water as the solvent to obtain a crude product. The crude product was then recrystallized from pure acetone at a temperature between 50 and 60°C. After crystals precipitated, the solution was sealed with a sealing film and cooled to room temperature, then placed in a refrigerator overnight. Finally, the solution was rinsed and filtered with a large amount of ultrapure water to obtain pure BATB oil-phase electrolyte, which was dried in a desiccator for about two days and then transferred to a sample vial for later use. TDDATB was prepared according to the literature doi.org / 10.1002 / celc.202200624.

[0054] 3. Preparation of aqueous and oil phase solutions

[0055] Preparation of the aqueous solution: Weigh 0.0058 g of lithium chloride solid powder, 0.0033 g of potassium ferricyanide solid, and 0.0422 g of potassium ferrocyanide solid into a sample bottle, add 10 mL of ultrapure water to dissolve, tighten the bottle cap, seal it with sealing film, and place it in a vortex mixer for vigorous vortexing for 30 seconds, then let it stand until use. In the aqueous solution, the concentrations of NaCl, potassium ferricyanide, and potassium ferrocyanide are 10 mmol / L.

[0056] Preparation of oil phase solution: Weigh 0.0304 g of ammonium bis(triphenylphosphine)tetra(pentafluorophenyl)borate and 0.005 g of 5,6,11,12-tetraphenyltetraphenyl into a sample bottle, add 5 mL of 1,2-dichloroethane to dissolve, tighten the cap and seal with sealing film, and place in a vortex mixer for vigorous vortexing for 30 seconds, then let stand until ready for use.

[0057] 4. Preparation of working and counter / reference electrodes

[0058] The electrochemical experiments conducted in this embodiment all use a two-electrode system. The 0.25 mm diameter Ag / AgCl electrode is the working electrode, while the 0.6 mm diameter Ag / AgCl electrode is the counter / reference electrode. Therefore, it is sufficient to plate a layer of AgCl onto two silver wires of different diameters.

[0059] Working electrode preparation method: Cut a 0.25 mm diameter silver wire and polish it using 2000-mesh polishing paper. Then, prepare a 0.1 M HCl solution and add it to the electrolytic cell. Select a 0.5 mm diameter platinum wire electrode as the counter electrode for preparing the Ag / AgCl electrode and immerse it in the electrolytic cell. Next, insert the 0.25 mm diameter silver wire as the working electrode into the electrolytic cell. Finally, perform constant potential (1.5 V) electrolysis for 5 minutes. Similarly, repeat the above steps for preparing the counter / reference electrode.

[0060] 5. Construction of liquid / liquid interfaces

[0061] The aqueous solution was added to a micro / nano glass tube using a syringe equipped with a micro-needle. A 0.25 mm diameter silver wire coated with AgCl was inserted into the tube to obtain the working electrode. The working electrode and the counter / reference electrode were then inserted together into an electrolytic cell containing an oil phase solution. The electrolytic cell was placed in a shielded box, and the ultra-low current analyzer was started, parameters were set, and cyclic voltammetry scanning was performed.

[0062] 6. Selection of collision potential

[0063] Cyclic voltammetry was performed with an aqueous phase consisting of 10 mM sodium chloride, 1 mM potassium ferricyanide, and 10 mM potassium ferrocyanide aqueous solution, and an oil phase consisting of a 1,2-dichloroethane solution containing 5 mM ammonium bis(triphenylphosphine)tetra(pentafluorophenyl)borate and 0.2 mM 5,6,11,12-tetraphenyltetraphenyl. The steady-state current plateau of -0.23 pA was selected as the current shielding region from the cyclic voltammogram, corresponding to a current of approximately -1000 pA. In the negative potential region of the potential window, electrons transfer from the aqueous phase to the oil phase. Negatively charged polystyrene microspheres were selected, and the particles moved towards the interface along the direction of the electric field of the double layer. Furthermore, the current-time curve and detailed magnified image of the shielding effect at the water / 1,2-dichloroethane interface after adding 50 pM polystyrene nanoparticles to the aqueous solution are shown below. Figure 2 As shown, a constant voltage of -0.25V is applied, and the inner diameter of the working electrode glass tube is 3300nm.

[0064] 7. Data Processing and Analysis

[0065] The magnitude of the current step caused by the blocking collision is inversely proportional to the square of the particle size and the size of the indicator electrode. A theoretical model and simple analytical expression have been developed to estimate the average value of the current step during the blocking collision. Therefore, the size of the analyte can now be directly correlated with the magnitude of the average current step without worrying about edge effects. The particle size is obtained from the following formula:

[0066]

[0067] Therefore, the inner radius (r) of the glass tube electrode is known. pipet ), the change in steady-state current before and after the collision (Δi) ss ) and the steady-state current value before the collision (i ss The particle size can then be calculated. This invention utilizes the shielding effect to calculate the particle size distribution of 50 pM polystyrene microspheres in a 10 mM sodium chloride + 1 mM potassium ferricyanide aqueous solution + 10 mM potassium ferrocyanide aqueous solution, such as... Figure 3 The bar chart is shown. The comparison results of DLS of this sample in deionized water and in 10 mM sodium chloride + 1 mM potassium ferricyanide + 10 mM potassium ferrocyanide aqueous solution are also shown. Figure 3 DLS measurements of polystyrene microspheres in deionized water showed that the particle size was mainly in the 250-500 nm range, with a dispersibility index (PDI) of 0.018, consistent with the parameters at the time of purchase. DLS results in a solution of 10 mM sodium chloride + 1 mM potassium ferricyanide + 10 mM potassium ferrocyanide also showed that the polystyrene microspheres were mainly distributed in the 200-500 nm range, with a PDI of 0.027, indicating that the polystyrene microspheres were very stable and showed little agglomeration even at high concentrations. Calculations using a single current step obtained from the shielding effect showed that the polystyrene microsphere particle size was mainly distributed between 200 and 400 nm, with relatively accurate and consistent results, demonstrating the effectiveness of using the liquid / liquid interface electron transfer shielding effect to measure the size of individual polystyrene microspheres.

[0068] Example 2

[0069] The difference between the single-particle size measurement method in this embodiment and that in Example 1 is that the concentration ratio of the redox couple in the aqueous solution is adjusted from 1 mM potassium ferricyanide + 10 mM potassium ferrocyanide to 10 mM potassium ferricyanide + 1 mM potassium ferrocyanide. All other aspects are the same as in Example 1.

[0070] Data processing and analysis are as follows: The current-time curve and its detailed magnified image of the shielding effect at the water / 1,2-dichloroethane interface after adding 50 pM polystyrene microspheres are shown below. Figure 4 As shown, a constant voltage of -0.25V was applied, and the inner diameter of the glass tube was 1600 nm. The particle size distribution of 50 pM polystyrene microspheres in a solution of 10 mM sodium chloride + 10 mM potassium ferricyanide + 1 mM potassium ferrocyanide was calculated using the shielding effect. Figure 5 The bar chart is shown. The comparison results of DLS of this sample in deionized water and in 10mM sodium chloride + 10mM potassium ferricyanide + 1mM potassium ferrocyanide aqueous solution are also shown. Figure 5The DLS results show that the polystyrene microspheres measured in pure deionized water are mainly distributed between 200-500 nm in size, with a PDI of approximately 0.018, consistent with the purchased parameters. DLS results in a solution of 10 mM sodium chloride + 10 mM potassium ferricyanide + 1 mM potassium ferrocyanide show that the particle size is also mainly distributed between 200-500 nm, with a PDI of 0.064, indicating that the polystyrene microspheres are very stable after the addition of this electrolyte and exhibit virtually no aggregation. The particle size of the polystyrene microspheres calculated using a single current step obtained through the shielding effect is mainly distributed between 200 and 600 nm. Although a small number of larger particles were observed, the results are still relatively accurate and consistent.

[0071] Example 3

[0072] The difference between the single-particle size measurement method in this embodiment and that in Example 2 is that the concentration of polystyrene microspheres is reduced from 50 pM to 10 pM; all other aspects are the same as in Example 2.

[0073] Data processing and analysis are as follows: At low concentrations, the aggregation of polystyrene microspheres can be more effectively prevented. The current-time curve and detailed magnified image of the shielding effect at the water / 1,2-dichloroethane interface after adding 10 pM polystyrene microspheres are shown below. Figure 6 As shown, a constant voltage of -0.25V was applied, and the inner diameter of the glass tube was 2000 nm. The particle size distribution of 10 pM polystyrene microspheres in a solution of 10 mM sodium chloride + 10 mM potassium ferricyanide + 1 mM potassium ferrocyanide was calculated using the shielding effect. Figure 7 The bar chart is shown. The comparison results of DLS of this sample in deionized water and in 10mM sodium chloride + 10mM potassium ferricyanide + 1mM potassium ferrocyanide aqueous solution are also shown. Figure 7 DLS results in a solution of 10 mM sodium chloride + 10 mM potassium ferricyanide + 1 mM potassium ferrocyanide showed that the particle size was mainly distributed between 200-500 nm, with a PDI of 0.064. This indicates that even at this concentration, 10 pM polystyrene microspheres are very stable after the addition of electrolyte, with virtually no aggregation effect. The particle size of the polystyrene microspheres calculated using the formula based on a single current step obtained through the shielding effect was mainly distributed between 250 and 450 nm, which is in excellent agreement with the DLS results, demonstrating the accuracy of this method.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for measuring the size of a single particle, characterized in that, Includes the following steps: (1) The pretreated capillary glass tube is drawn into a micro-nano glass tube with micro-nano tips; (2) Inject an aqueous solution into the micro / nano glass tube obtained in step (1), and then insert a silver wire coated with AgCl into the micro / nano glass tube to obtain a working electrode; the aqueous solution includes a water-soluble redox couple; (3) Insert the Ag / AgCl electrode and the working electrode obtained in step (2) together into an electrolytic cell containing an oil phase solution, and then place them in an electrostatic shielding box to measure the steady-state current; the oil phase solution includes an electron acceptor compound or an electron donor compound, and the electron acceptor compound includes at least one of 5,6,11,12-tetraphenylbenzotetraphenyl and 7,7,8,8-tetracyanobenzoquinone dimethyl ether; (4) Add the test particles to the aqueous solution, measure the steady-state current after collision, and calculate the particle size of the test particles according to the formula: In the formula, r p Let r be the radius of the particle to be measured. pipet i is the inner radius of the micro / nano glass tube described in step (1). ss The steady-state current described in step (3), Δi ss The difference between the steady-state current after the collision described in step (4) and the steady-state current in step (3) is given.

2. The single-particle size measurement method according to claim 1, characterized in that, In step (2), the water-soluble redox couple is Fe(CN)6. 3- / Fe(CN)6 4- .

3. The single-particle size measurement method according to claim 2, characterized in that, In step (2), the Fe(CN)6 in the aqueous solution 3- With the Fe(CN)6 4- The concentration ratio is (1-10):(1-10).

4. The single-particle size measurement method according to claim 1, characterized in that, In step (2), the aqueous solution further includes an aqueous electrolyte, which is a soluble chloride salt.

5. The single-particle size measurement method according to claim 1, characterized in that, In step (3), the concentration of the electron acceptor compound or electron donor compound in the oil phase solution is 0.1 mmol / L-2 mmol / L.

6. The single-particle size measurement method according to claim 1, characterized in that, In step (3), the oil phase solution further includes an oil phase electrolyte, which is ammonium bis(triphenylphosphine)tetra(pentafluorophenyl)borate or ammonium tetra(dodecyl)tetra(pentafluorophenyl)borate.

7. The single-particle size measurement method according to claim 6, characterized in that, In step (3), the concentration of the oil phase electrolyte in the oil phase solution is 5 mmol / L-20 mmol / L.

8. The single-particle size measurement method according to claim 1, characterized in that, In step (4), the ratio of the inner diameter of the micro / nano glass tube to the diameter of the particle to be tested is (3-10):

1.

9. The method for measuring the size of a single particle according to claim 1, characterized in that, In step (4), the concentration of the particles to be tested in the aqueous solution is 10. -15 mmol / L-10 -12 mmol / L.

10. The method for measuring the size of a single particle according to claim 1, characterized in that, In step (4), the particle to be tested is an insulating particle or a semiconductor particle.

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