System and method for analysis of neutral cluster size distribution and chemical composition below 3 nanometers

Abstract

This invention provides a system for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers. This invention further provides a method for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers. The system and method provided by this invention, based on central sample flow sampling, achieves efficient sampling of nanoparticles. Utilizing the high charging efficiency of a unipolar charging device for nanoparticles, the nanoparticles are charged and efficiently transported to the inlet of a nanoparticle size sieving device. Through a special aerodynamic design, the nanoparticles are efficiently transported through the electric field between the electrode plates to the particle number concentration and chemical composition detectors, demonstrating excellent application prospects.

Description

Technical Field

[0001] This invention belongs to the technical field of analytical testing, and relates to a system and method for analyzing the particle size distribution and chemical composition of neutral clusters below 3 nanometers. Specifically, it relates to a synchronous measurement system and method for molecular clusters below 3 nm in size and chemical composition, which can be applied to environmental monitoring, atmospheric science research, nanomaterial characterization, bioaerosol analysis, and monitoring of ultrafine particles in industrial processes. Background Technology

[0002] The particle size, chemical composition, and spatial configuration of particles smaller than 3 nanometers (3 nm) have a decisive influence on their physical stability, chemical reactivity, and environmental behavior. However, due to their extremely small size, experimental measurement of these properties still faces many technical challenges. Currently, measurements of particle size distribution and chemical composition of particles smaller than 3 nm are mostly separate measurements, and each measurement step (including sampling, transfer, charging, sieving, number concentration, and chemical composition analysis) has significant uncertainties, making it difficult to comprehensively and accurately characterize their properties.

[0003] First, during particulate matter sampling and transport, particles smaller than 3 nanometers face an extremely high risk of diffusion loss. Due to their small size, their diffusion rate is extremely fast, making it very easy for particles near the pipe wall to accumulate and be lost.

[0004] Secondly, during the charging process, particles achieve charge equilibrium through collisions with ions via random thermal motion. However, as the particle size decreases, the probability of collisions between particles and ions decreases, leading to a significant drop in the charge ratio. Traditional bipolar chargers have limited charging capabilities for nanoparticles and are not suitable for measuring low concentrations of particles smaller than 3 nanometers.

[0005] In particle size distribution, differential electromobility particle size analyzers (DMA) have been widely used for measuring the electromobility and sieving of particles larger than 3 nanometers. The basic principle is that under a certain electric and flow field, charged particles are separated according to their electromobility (related to equivalent particle size), and only particles with a specific electromobility can pass through the DMA. However, existing DMAs face problems such as decreased resolution, reduced sieving accuracy, and insufficient particle throughput when sieving particles smaller than 3 nanometers, making it difficult to meet the precise sieving requirements of ultrafine particles.

[0006] Furthermore, in number concentration measurements, condensed particle counters (CPCs) are one of the most commonly used methods, relying on the growth of particles to optically detectable sizes in supersaturated vapor. However, due to the Kelvin effect, particles smaller than 3 nanometers are difficult to activate and grow effectively, leading to a significant reduction in measurement sensitivity and accuracy. On the other hand, particles smaller than 3 nanometers are typically composed of only a few to a few dozen molecules, have extremely low mixing ratios in the atmosphere (usually below the ppb level), and are highly susceptible to physical or chemical changes during sampling and measurement, further exacerbating measurement uncertainties.

[0007] Chinese authorized patent ZL202311442677.6 discloses a system and method for analyzing particle size distribution and chemical composition of particles smaller than 3 nanometers. It has the ability to analyze particle size and chemical composition in combination. However, the system has technical limitations in the design of the monopolar charge and the coupling between its subsystems. Therefore, it affects the efficient transmission and analysis of 3-nanometer particles by the entire analysis system, thereby affecting the response efficiency and accuracy of the entire analysis system for particles smaller than 3 nanometers.

[0008] In summary, existing technologies have significant limitations in measuring particles smaller than 3 nanometers, particularly in achieving efficient particle size separation and chemical composition analysis simultaneously at low concentrations. Most current research remains focused on the separation and measurement of particle size and composition, lacking integrated, highly sensitive, and low-loss coupled analytical systems. This restricts in-depth research on nanoaerosols and the assessment of their environmental effects. Therefore, there is an urgent need to further optimize systems and methods for analyzing the particle size distribution and chemical composition of particles smaller than 3 nanometers to improve their sensitivity, resolution, and measurement accuracy at low concentrations, thereby promoting the development of related research and applications. Summary of the Invention

[0009] In view of the above-mentioned shortcomings of existing methods for detecting particles smaller than 3 nanometers, the purpose of this invention is to provide a system and method for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers.

[0010] To achieve the above and other related objectives, the first aspect of the present invention provides a system for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers, comprising a sampling device, a unipolar charging device, a first coupling transmission device, a nanoparticle size sieving device, a second coupling transmission device, a mass spectrometry device, an aerosol number concentration measuring device, and a system control device. The sampling device, unipolar charging device, first coupling transmission device, nanoparticle size sieving device, second coupling transmission device, and mass spectrometry device are sequentially connected along the particle input direction. The second coupling transmission device is also connected to the aerosol number concentration measuring device. The system control device is signal-connected to the sampling device, unipolar charging device, nanoparticle size sieving device, mass spectrometry device, and aerosol number concentration measuring device, respectively.

[0011] A second aspect of this invention provides a method for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers, employing the aforementioned system for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers, comprising the following steps:

[0012] 1) Set the transmission flow rate and the central sampling flow rate in the sampling device. After the nanoparticles are introduced into the sampling main tube of the sampling device through the transmission flow rate, they are collected in the central sampling tube by maintaining laminar flow through the central sampling flow rate and then transported to the unipolar charging device through the central sampling flow rate.

[0013] 2) Set the discharge gas flow rate, the first power supply voltage, and the second power supply voltage in the unipolar charging device. The discharge gas flow rate is used to make the plasma generated by the discharge gas form a unipolar ion flow under the action of the first power supply voltage. Then, under the action of the second power supply voltage, the ion flow is mixed and collided with the nanoparticles in the central sampling flow to obtain charged nanoparticles, which are then transported to the first coupling transmission device.

[0014] 3) Reduce the electrostatic loss of charged nanoparticles through the first coupling transmission device, and then transport the charged nanoparticles to the nanoparticle size sieving device.

[0015] 4) In the nanoparticle size sieving device, the sheath flow rate and the third power supply voltage are set. Under the action of the electric field formed by the fixed flow field and the third power supply voltage, the charged nanoparticles are sieved along the electrode sieving area between the upper electrode plate and the lower electrode plate. The nanoparticles corresponding to the target electromigration are transported to the second coupling transmission device.

[0016] 5) The nanoparticles sieved in the second coupling and transmission device are transported to the mass spectrometry device and the aerosol number concentration device for simultaneous measurement. The chemical composition of the nanoparticles is determined in the mass spectrometry device at a fixed mass spectrometry sampling flow rate. The number concentration of the nanoparticles is determined in the aerosol number concentration device by setting the aerosol sampling flow rate.

[0017] 6) The particle size, number concentration, and chemical composition information of nanoparticles are matched by the system control device to obtain the concentration distribution and chemical composition information of nanoparticles with different particle sizes.

[0018] As described above, the present invention provides a system and method for analyzing the size distribution and chemical composition of neutral clusters smaller than 3 nanometers. A sampling device efficiently collects nanoparticles; a unipolar charging device generates high-concentration ions through dielectric barrier discharge, causing the nanoparticles to become unipolarly charged; a first coupling and transmission device suppresses electrostatic losses and efficiently transmits the charged particles; a nanoparticle size sieving device provides a fixed flow field and electric field for sieving the charged nanoparticles. By optimizing the internal geometry of the particle size sieving device, the sheath flow velocity through the electrode plate is increased, and the particle size sieving region maintains laminar flow even when the Reynolds number of the sheath flow is greater than 10,000, thereby improving the particle size resolution and reducing diffusion losses; a second coupling and transmission device efficiently transmits the sieved particles to a mass spectrometer and an aerosol analyzer; the number concentration and chemical composition of the particles are measured by the mass spectrometer and aerosol analyzer. This system has broad application prospects in atmospheric science and materials science.

[0019] This invention provides a system and method for analyzing the size distribution and chemical composition of neutral clusters smaller than 3 nanometers. The proposed unipolar charge structure is suitable for high aerosol flow conditions, achieving high charging efficiency for nanoparticles and significantly improving the particle transport efficiency within the system. Furthermore, this invention, for the first time, adds high-efficiency transport interfaces at the inlet and outlet of the nanoparticle size sieving device, further optimizing the particle transport path throughout the measurement system, thereby improving the system's measurement stability and response sensitivity.

[0020] This system utilizes a central sample flow sampling method combined with a high-efficiency unipolar charging device to charge nanoparticles and stably guide them to the inlet of the particle size separation device. Through optimized electrode structure and aerodynamic design, charged particles are sieved at high resolution under the influence of an electric field and efficiently transported to the particle number concentration and chemical composition detection modules, demonstrating good adaptability and promising practical application prospects. Attached Figure Description

[0021] Figure 1 The diagram shows the working principle of the neutral cluster particle size distribution and chemical composition analysis system below 3 nanometers of the present invention.

[0022] Figure 2 The diagram shown is a schematic representation of the sampling device of the present invention.

[0023] Figure 3The diagram shown illustrates the working principle of the unipolar charging device of the present invention.

[0024] Figure 4 The diagram shown is a transmission structure diagram of the first coupling transmission device of the present invention.

[0025] Figure 5 The diagram shows the structure and operation process of the nanoparticle size sieving device of the present invention.

[0026] Figure 6 The diagram shows the transmission structure of the second coupling transmission device of the present invention.

[0027] Figure 7a The diagram shows the particle size distribution results of the present invention.

[0028] Figure 7b The image shows the mass spectrometry results at different electromobilities according to the present invention.

[0029] Figure 8 The graph shows a comparison of the signal response of this invention and Chinese patent ZL202311442677.6 for measuring particles of different sizes.

[0030] Figure Labels

[0031] 1. Sampling device

[0032] 2. Monopole charging device

[0033] 3 First coupling transmission device

[0034] 4. Nanoparticle size sieving device

[0035] 5 Second Coupling Transmission Device

[0036] 6. Aerosol Number Concentration Measurement Apparatus

[0037] 7. Mass spectrometry apparatus

[0038] 8 System Control Device

[0039] 201 Sampling Supervisor

[0040] 202 Reducing Tee

[0041] 203 Central Sampling Tube

[0042] 204 First Particulate Filter

[0043] 205 Bypass Fan

[0044] 301 imported pipe

[0045] 302 Sealed Joint

[0046] 303 pipe body

[0047] 304 Dielectric Barrier Discharge Electrode

[0048] 305 Ion Trapping Electrode

[0049] 306 Export Pipe

[0050] 307 internal tube

[0051] 308 First Power Supply

[0052] 309 Second Power Supply

[0053] 310 Discharge Gas Inlet

[0054] 401 First Transmission Inlet Pipe

[0055] 402 First transmission outlet pipe

[0056] 403 Integrated Circuit Experiment Board

[0057] 404 Insulated Connection Module

[0058] 405 metal electrode

[0059] 501 Aerosol Import

[0060] 502 Third Power Supply

[0061] 503 Upper Electrode Plate

[0062] 504 Sheath gas inlet

[0063] 505 Second Particulate Filter

[0064] 506 Temperature and Humidity Sensor

[0065] 507 Sheath Gas Cooling Device

[0066] 508 Circulating Fan

[0067] 509 Aerosol Export

[0068] 510 Lower-level electrode plate

[0069] 601 Insulating Coupler

[0070] 602 stainless steel coupler

[0071] 603 Ion Flight Chamber

[0072] 604 Count Concentration Sampling Port Detailed Implementation

[0073] Please see Figures 1 to 8It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0074] The first aspect of this invention provides a system for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers, such as... Figure 1 As shown, the system includes a sampling device, a unipolar charging device, a first coupling transmission device, a nanoparticle size sieving device, a second coupling transmission device, a mass spectrometry device, an aerosol number concentration measuring device, and a system control device. The sampling device, unipolar charging device, first coupling transmission device, nanoparticle size sieving device, second coupling transmission device, and mass spectrometry device are connected sequentially along the particle input direction. The second coupling transmission device is also connected to the aerosol number concentration measuring device. The system control device is connected to the sampling device, unipolar charging device, nanoparticle size sieving device, mass spectrometry device, and aerosol number concentration measuring device via signal connections.

[0075] In the above system, such as Figure 2 As shown, the sampling device includes a sampling main pipe and a central sampling pipe connected sequentially along the particulate matter input direction. A reducing tee is provided between the sampling main pipe and the central sampling pipe. The reducing tee is also connected to a first particulate matter filter. A bypass fan is connected to the first particulate matter filter.

[0076] In one specific embodiment, the ratio of the total transmission flow rate in the sampling main pipe to the central sampling flow rate in the central sampling tube is not less than 5, preferably 5-10. By using the sample flow center sampling method, the airflow under the total sampling flow rate is controlled to maintain laminar flow in the pipe, that is, the airflow in both the sampling main pipe and the central sampling tube is in a laminar flow state, and the particulate matter to be measured located at the axial center of the sampling main pipe is introduced into the unipolar charging device by the central sampling tube.

[0077] In one specific embodiment, the dimensionless diffusion coefficient μ (dimensionless diffusion loss number) of the total transmission flow rate in the main sampling tube and the central sampling flow rate in the central sampling tube is kept less than 0.1. Since the particles in the main sampling tube do not contact the tube wall, the number concentration of nanoparticles in the central sampling section of the entire sampling pipeline remains close to 100%, reducing the contact between particles in the axial center of the pipeline and the tube wall, improving the transmission efficiency of particles, and achieving efficient sampling of nanoparticles.

[0078] The aforementioned sampling device is a high-efficiency sampling device used for the efficient transport of particles smaller than 3 nanometers. The first particulate filter is a conventionally used high-efficiency particulate filter (HEPA) capable of filtering particulate matter from the remaining gas. The bypass fan is a conventionally used fan; the bypass gas flow rate is controlled by adjusting the operating voltage, and the remaining gas is discharged as bypass gas through the bypass fan. The flow rate of the central sampling tube is jointly detected and determined by a mass spectrometer and an aerosol number concentration analyzer.

[0079] In the above system, such as Figure 3 As shown, the unipolar charging device includes a tube body with sealed joints at both ends. The tube body has an inlet pipe at its input end, serving as a particulate matter inlet, which extends into the tube body after passing through the sealed joint. The tube body also has an outlet pipe at its output end, serving as a particulate matter outlet, which extends into the tube body after passing through the sealed joint. The tube body is connected to a sampling device via the inlet pipe and to a first coupling transmission device via the outlet pipe. An inner tube is located within the tube body, sleeved around the portion of the inlet pipe extending into the tube body and maintaining a distance from the end of the outlet pipe extending into the tube body. A discharge gas inlet and a dielectric barrier discharge electrode are sequentially arranged on the outer wall of the tube body along the particulate matter input direction. The dielectric barrier discharge electrode is arranged in a circular ring around the outer wall of the tube body. The discharge gas inlet communicates with the interior of the tube body. An ion trapping electrode is located on the inner wall of the tube body outside the portion of the outlet pipe extending into the tube body, also arranged in a circular ring around the inner wall of the tube body.

[0080] In one specific embodiment, the tube body is cylindrical in shape.

[0081] In one specific embodiment, the tube body and the inner tube are made of quartz.

[0082] In one specific embodiment, the sealing joint is made of Teflon.

[0083] In one specific embodiment, the inlet pipe and outlet pipe are made of stainless steel.

[0084] In one specific embodiment, the airflow in the inlet pipe is the central sample flow of the sampling device, and its flow rate is jointly detected and determined by the mass spectrometer and the aerosol number concentration measuring device.

[0085] In one specific embodiment, the inlet pipe is connected to the central sampling pipe.

[0086] In one specific implementation, such as Figure 3 As shown, the axial length of the inner tube is greater than the axial length of the portion of the inlet tube that extends into the tube body.

[0087] In one specific embodiment, the axial distance between the end of the inner tube near the outlet tube and the end of the outlet tube extending into the tube body is 9-11 mm, preferably 10 mm.

[0088] In one specific embodiment, the vertical distance between the end of the inner tube near the outlet tube and the dielectric barrier discharge electrode is 9-11 mm, preferably 10 mm.

[0089] In one specific embodiment, the vertical distance between the ion trapping electrode and the end of the outlet tube that extends into the tube body is 9-11 mm, preferably 10 mm.

[0090] In one specific embodiment, an inert gas is introduced into the discharge gas inlet. The inert gas is helium.

[0091] In one specific implementation, such as Figure 3 As shown, the dielectric barrier discharge electrode is externally connected to a first power source. This first power source is an AC high-voltage power source. The first power source acts on the dielectric barrier discharge electrode, discharging the discharge gas entering from both sides of the quartz body to generate plasma. The discharge intensity can be controlled by adjusting the voltage and frequency of the first power source.

[0092] In one specific implementation, such as Figure 3 As shown, the ion-collecting electrode is externally connected to a second power supply. The second power supply is a DC high-voltage power supply. Under the action of the second power supply, the ion-collecting electrode captures ions from the plasma generated by the discharge. By changing the ion-collecting voltage to adjust the unipolar ion concentration, the generated unipolar ion gas flow mixes with the gas flow in the sample injection tube, and the ions rapidly collide with the particles to complete the charging process.

[0093] The aforementioned unipolar charging device is a high-efficiency unipolar charging device used to efficiently charge particles smaller than 3 nanometers. It has a simple structure, low cost, and stable operation. It does not produce byproducts such as ozone or particulate matter during use. It is suitable for charging particles under high flow rate conditions and can significantly improve the transmission efficiency of nanoparticles.

[0094] The aforementioned unipolar charging device generates plasma through dielectric barrier discharge, and under the action of a trapping voltage, produces plasma with extremely high concentrations (number concentration range of 10). 7 -10 9cm -3 The process involves the use of unipolar charged ions with extremely small particle sizes (e.g., 0.5-1.5 nm). These charged ions collide with neutral nanoparticles entering through the inlet pipe, bringing the particles to a state of charge equilibrium. The charged nanoparticles are then discharged through the outlet pipe. This soft ionization method minimizes the breakage and complex compositional changes of the nanoparticles, while increasing their charge ratio, resulting in a high concentration of unipolar charged ions.

[0095] Specifically, when the dielectric barrier discharge electrode and the ion trapping electrode are closed, naturally charged particles (some particles already partially charged before being charged) pass through the unipolar charging device. When the dielectric barrier discharge electrode and the ion trapping electrode are open, a very high concentration of unipolar ions is generated through dielectric barrier discharge, which then charges the nanoparticles. By changing the dielectric barrier discharge frequency and the ion trapping electrode voltage, the number concentration of ions generated by the dielectric barrier discharge device is altered. This soft ionization method of unipolar ions minimizes the breakage and complex compositional changes of the nanoparticles and increases their charge ratio.

[0096] In the above system, such as Figure 4 As shown, the first coupling transmission device includes a stacked region, which includes a first stacked segment and a second stacked segment. The first stacked segment and the second stacked segment are spaced apart to form a passage. Several metal electrodes are respectively provided in the first stacked segment and the second stacked segment. An insulating connection module is provided between adjacent metal electrodes. An integrated circuit experimental board is connected to the metal electrodes. A first transmission inlet pipe and a first transmission outlet pipe are respectively provided at both ends of the stacked region. The input end of the first transmission inlet pipe is connected to the outlet end of the unipolar charging device, and the output end of the first transmission outlet pipe is connected to the inlet end of the nanoparticle size sieving device.

[0097] The aforementioned stacked area is designed to reduce electrostatic loss of particles at the inlet due to the high-intensity electric field when they enter the nanoparticle sieving device. The stacked area employs an ion drift tube structure. The ion drift tube is constructed by stacking insulating connecting modules, such as electrostatic dissipative materials, and metal electrodes, with adjacent metal electrodes connected in series with a 5-10 MΩ resistor.

[0098] In one specific embodiment, the input end of the first transmission inlet pipe is connected to the outlet pipe of the unipolar charging device, and the output end of the first transmission outlet pipe is connected to the aerosol inlet of the nanoparticle size sieving device.

[0099] In one specific embodiment, the first transmission inlet pipe and the first transmission outlet pipe are made of stainless steel.

[0100] In one specific embodiment, the metal electrode and the insulating connection module are sealed with an O-ring to achieve good electrical insulation and airtightness.

[0101] In one specific embodiment, the metal electrode is a conventionally used metal electrode, such as a stainless steel electrode.

[0102] In one specific embodiment, the insulating connection module is an electrostatic dissipative material. This electrostatic dissipative material is prepared by adding a special antistatic agent to a copolymeric polyoxymethylene-based material, which effectively improves its electrostatic release performance, prevents electrostatic accumulation, and thus improves the transmission efficiency of charged particles in the reverse electric field.

[0103] In one specific embodiment, the stacked area is secured with four threaded rods made of insulating material and nuts to ensure the overall sealing performance of the device.

[0104] In a preferred embodiment, the threaded rod is made of high-temperature and corrosion-resistant polyether ether ketone (PEEK) material, and both ends are provided with external threads to facilitate detachable connection with corresponding connectors.

[0105] In one specific embodiment, the integrated circuit experimental board includes several resistors connected in series. Each resistor corresponds one-to-one with a metal electrode and is connected to its corresponding metal electrode. One end of the integrated circuit experimental board is connected in series with a nanoparticle sieving device, and the other end is connected in series with a unipolar charging device and grounded. This establishes a stable and uniform reverse electric field within the first coupling and transmission device, effectively reducing electrostatic losses of charged particles during their entry into the nanoparticle sieving device and improving the overall transmission efficiency of the particles.

[0106] In a preferred embodiment, the resistance value of the resistor is 5-10 MΩ.

[0107] In a preferred embodiment, one end of the integrated circuit experimental board is electrically connected to the upper electrode plate of the nanoparticle sieving device, and the other end of the integrated circuit experimental board is grounded.

[0108] The aforementioned first coupling transmission device is an intermediate coupling transmission device between the monopolar charging device and the nanoparticle size screening device. It connects the outlet of the monopolar charging device to the inlet of the nanoparticle size screening device, aiming to solve the problem in existing nanoparticle size screening devices where a non-uniform reverse electric field exists at the aerosol inlet due to the high voltage applied to the upper electrode plate, resulting in significant electrostatic losses of charged particles during transmission. By constructing a suitable reverse uniform electric field, the interference caused by the local high-intensity electric field at the inlet of the nanoparticle size screening device on charged particles is effectively suppressed, achieving efficient transmission of charged particles and significantly improving its transmission efficiency.

[0109] In the above system, such as Figure 5 As shown, the nanoparticle size sieving device includes a fixed electric field and a fixed flow field. The fixed electric field has an upper electrode plate and a lower electrode plate arranged sequentially along the particle input direction. The upper electrode plate and the lower electrode plate are parallel and spaced apart to form a sheath gas channel as the electrode sieving area. The upper electrode plate and the lower electrode plate are respectively provided with slits. The slit of the upper electrode plate is connected to an aerosol inlet, and the slit of the lower electrode plate is an aerosol outlet. The upper electrode plate is connected to a third power source. The fixed flow field includes a sheath flow closed loop passing through the sheath gas channel. The inlet of the sheath gas channel is provided with a sheath gas inlet. On the sheath flow closed loop located outside the sheath gas channel, a second particle filter, a temperature and humidity sensor, a sheath gas cooling device, and a circulating fan are arranged sequentially along the direction away from the sheath gas inlet.

[0110] In one specific embodiment, the aerosol inlet is connected to the first coupling transmission device, and the aerosol outlet is connected to the second coupling transmission device.

[0111] In a preferred embodiment, the aerosol inlet is connected to the first transmission outlet pipe.

[0112] In one specific embodiment, the thickness of the upper electrode plate and the lower electrode plate is 0.1-1cm, preferably 0.5cm.

[0113] In one specific embodiment, the length of the upper electrode plate and the lower electrode plate along the parallel sheath gas channel is 20-30cm, preferably 24cm; the width of the upper electrode plate and the lower electrode plate along the perpendicular sheath gas channel is 3-5cm, preferably 4cm.

[0114] In one specific embodiment, the horizontal distance between the slit of the upper electrode plate and the slit of the lower electrode plate is 3-5 cm, preferably 4 cm.

[0115] In one specific embodiment, the slit width for aerosol injection on the upper electrode plate is 0.5-0.7 mm, preferably 0.6 mm; the slit width for aerosol outlet on the lower electrode plate is 0.1-0.2 mm, preferably 0.15 mm.

[0116] By reducing the length and spacing of the upper and lower electrode plates, the diffusion loss of particles during the particle size sieving process is reduced.

[0117] In one specific embodiment, a fixed voltage of -10kV to 10kV is applied between the upper electrode plate and the lower electrode plate to form a uniform electric field between the upper electrode plate and the lower electrode plate, thereby achieving the sieving of particles with different electromobility.

[0118] The slits in the upper and lower electrode plates are the inlet and outlet of the particles to be tested before and after particle size sieving, respectively. When charged particles flow into the sieving area, due to the different electromobilities of particles of different sizes under the electric field conditions, they have different movement paths. Only nanoparticles with specific electromobilities can pass through the sieving electric field and flow out from the outlet, thus achieving particle size sieving of nanoparticles through this structure. Specifically, the aerosol particles to be tested flow in from the inlet slit on the upper electrode plate and flow out from the outlet slit at the bottom of the lower electrode plate. The inlet slit for the particles to enter the sieving electric field is designed based on fluid dynamics to reduce the radial velocity of the airflow between the electrode plates, greatly improving the particle size resolution of the sieving. The flow field conditions between the upper and lower electrode plates have a significant impact on the efficient and accurate sieving of nanoparticles. This device minimizes the impact of turbulence on the nanoparticle sieving process by improving the processing precision of the electrode plate surface, shortening the length of the parallel electrode plates, and designing a tapering opening before the sheath flow enters the flow field.

[0119] In one specific embodiment, the flow velocity of the sheath flow between the upper electrode plate and the lower electrode plate is 300-1500 L / min.

[0120] In one specific embodiment, the inlet of the sheath gas channel in the electrode screening area is a truncated pyramidal opening, and the angle between the inlet wall of the sheath gas channel and the central axis of the sheath gas channel is 25-35°, preferably 30°; the outlet of the sheath gas channel in the electrode screening area is a truncated pyramidal opening, and the angle between the outlet wall of the sheath gas channel and the central axis of the sheath gas channel is 25-35°, preferably 30°.

[0121] In one specific embodiment, in the sheath gas channel, the inner walls of the upper electrode plate and the lower electrode plate are mirror polished, and the machining accuracy is less than or equal to 0.02 mm.

[0122] By optimizing the internal geometry and processing precision, the particle size sieving area between the two electrode plates can still maintain laminar flow when the Reynolds number of the sheath flow is greater than 10,000.

[0123] The above-mentioned nanoparticle size sieving device is a nanoparticle size sieving instrument, which is used to construct stable flow field and electric field conditions to form a fixed flow field and electric field, and to perform particle size sieving according to the electromobility of charged particles to obtain monodisperse standard aerosols.

[0124] The aforementioned circulating fan is a conventional brushless fan used to control the sheath gas flow rate during the screening process. The aforementioned sheath gas cooling device is an all-aluminum water-cooled intercooler equipped with a low-temperature thermostatic bath for controlling the sheath gas temperature. The aforementioned temperature and humidity sensor is a conventionally used sensor capable of effectively monitoring the temperature and humidity of the sheath gas. The aforementioned second particulate filter is a conventionally used high-efficiency particulate filter (HEPA) for filtering particulate matter from the sheath gas flow.

[0125] The aforementioned third power source is a high-voltage DC power supply, used to provide screening voltage to the upper electrode plate. This voltage can be switched between positive and negative terminals. The aforementioned lower electrode plate is grounded. Since the upper electrode plate carries high voltage, failure to isolate it would severely compromise operational safety. Therefore, the embodiment includes a design for isolating the electrode plate, made of polyetheretherketone (PEEK), ensuring electrical insulation between the electrode plate and the system cavity wall and detection device. This prevents the high voltage on the electrode plate from being conducted to the system cavity wall and detection device, thus guaranteeing the safety of using the detection system.

[0126] The working modes of the above-mentioned nanoparticle size sieving device and the unipolar charging device need to be consistent. When the unipolar charging device uses positive ions to charge nanoparticles, the working mode of sieving positively charged particles should be switched accordingly in the nanoparticle size sieving device.

[0127] In the above system, such as Figure 6 As shown, the second coupling and transmission device includes an ion flight chamber. An insulating coupler and a stainless steel coupler are provided outside the ion flight chamber from the inside to the outside. The ion flight chamber and the insulating coupler are fixed to the lower electrode plate of the nanoparticle size sieving device, and the inlet of the ion flight chamber is coaxial with the outlet of the nanoparticle size sieving device. The stainless steel coupler is connected to the inlet end of the mass spectrometry measuring device, and the outlet of the ion flight chamber is coaxial with the inlet of the mass spectrometry measuring device. The ion flight chamber is also provided with a number concentration sampling port, which is connected to the aerosol number concentration measuring device.

[0128] In one specific embodiment, the ion flight chamber is fixed to the lower electrode plate of the nanoparticle size sieving device by screws.

[0129] In one specific embodiment, the insulating coupler is made of polyetheretherketone (PEEK).

[0130] In one specific embodiment, the insulating coupler has a hollow flat plate structure. This serves to form an electrical insulation structure between the lower-stage electrode plate of the nanoparticle size separation device and the stainless steel coupler.

[0131] In one specific embodiment, the stainless steel coupler is made of stainless steel.

[0132] In one specific embodiment, the stainless steel coupler is a hollow stainless steel plate. The stainless steel coupler ensures that it maintains the same potential as the mass spectrometry measuring device, avoiding interference from particulate matter transport caused by potential differences.

[0133] In one specific embodiment, the inlet of the ion flight chamber is coaxial with the aerosol outlet of the nanoparticle size sieving device, and the inlet of the ion flight chamber and the aerosol outlet of the nanoparticle size sieving device are connected and have the same inner diameter. This can effectively reduce particle loss caused by changes in pipe diameter or flow field disturbances.

[0134] In one specific embodiment, the ion flight chamber is a particulate matter transport tube, the inner diameter of the ion flight chamber is 0.5-2mm, preferably 1mm; the processing accuracy of the ion flight chamber is less than or equal to 0.05mm.

[0135] In one specific embodiment, the distance between the outlet of the ion flight chamber and the inlet of the mass spectrometry measuring device is 0.5-1.0 cm, preferably 1 cm.

[0136] In one specific embodiment, the number concentration sampling port is located radially within the ion flight cavity.

[0137] In one specific embodiment, the outlet of the ion flight chamber is electrically connected to the flow-limiting inlet of the mass spectrometer. The potential between the outlet of the ion flight chamber and the inlet of the mass spectrometer is kept consistent.

[0138] In one specific embodiment, each component of the second coupling transmission device is sealed with O-rings to ensure overall airtightness.

[0139] The aforementioned second coupling transmission device is a coupling transmission device between the nanoparticle size sieving device and the mass spectrometry device. It is used to connect the outlet of the nanoparticle size sieving device to the particle number concentration detector of the aerosol number concentration measuring device and the chemical component detector of the mass spectrometry device. It aims to solve the problem of large particle transmission loss caused by the mismatch of pipeline size between the outlet of the existing nanoparticle size sieving device and the particle size-chemical component detector. It mainly improves particle transmission efficiency by keeping the inner diameter of the ion flight chamber of the second coupling transmission device consistent with the outlet of the nanoparticle sieving device, maintaining the same transmission pipeline size, reducing dead volume and shortening the time for particle transmission to the detector, thereby realizing efficient transmission of monodisperse aerosols from the sieving device to the aerosol number concentration measuring device and the mass spectrometry device.

[0140] In the above system, such as Figure 1As shown, the mass spectrometry device is a conventionally used mass spectrometer with a detector, specifically an atmospheric pressure interface time-of-flight mass spectrometer. It can directly measure the chemical composition of charged nanoparticles and match this measurement with the particle size and number concentration information of the nanoparticles from the aerosol number concentration measurement device.

[0141] In one specific embodiment, in the number concentration detection, charged particles, after being filtered through a quartz filter membrane in a Faraday cup, generate a weak current during transmission between the filter membrane and the wire. This current is measured using an electrometer, and the concentration of charged particles is calculated by combining this current with the aerosol flow rate. The formula for calculating the concentration of charged particles (C) is:

[0142]

[0143] In the formula, I is the weak current measured by the electrometer, n is the number of particles carrying charge, e is the elementary charge, Q is the flow rate of the carrier gas, and η is the detection efficiency of the aerosol electrometer.

[0144] In the above system, such as Figure 1 As shown, the aerosol number concentration measuring device is a conventionally used aerosol number concentration measuring device, specifically an aerosol electrometer. It is used to measure the concentration of charged particles, primarily focusing on the measurement of charged particles, calculating the particle concentration by measuring the weak current generated by the particles. Its key advantage is that it is not limited by the Kelvin effect, therefore theoretically there is no lower limit to particle size detection.

[0145] In the above system, such as Figure 1 As shown, the system control device includes a first data acquisition card, a second data acquisition card, and a controller. The first data acquisition card is used to acquire chemical composition information data measured by the mass spectrometry device. The second data acquisition card is used to acquire the particle size information and number concentration data of nanoparticles measured by the nanoparticle size sieving device. The controller obtains the number concentration distribution and chemical composition information of nanoparticles of different sizes through time matching technology.

[0146] In one specific embodiment, the second data acquisition card also acquires data from other signal-connected devices besides the particle size information obtained by the nanoparticle size sieving device, and controls the operation of other signal-connected devices besides the mass spectrometry device.

[0147] The first data acquisition card can control the instrument operating conditions of the mass spectrometry device.

[0148] The second data acquisition card enables real-time reading and control of temperature, pressure, flow rate, and voltage sensor signals throughout the system. It can also read the current signal output by the aerosol measuring device and convert the current into particulate matter concentration based on the set flow rate conditions. The instrument parameters that the second data acquisition card can control include: bypass gas flow rate and central sample flow rate of the sampling device; sampling flow rate, discharge gas flow rate, dielectric barrier discharge voltage intensity and frequency, and electrostatic trapping electrode voltage intensity of the unipolar charging device; sheath gas flow rate, cooling temperature, and sieving voltage of the nanoparticle size sieving device; and carrier gas flow rate of the aerosol device.

[0149] The time-matching technique refers to the use of standard clusters to calibrate and standardize the response times of nanoparticle size, number concentration, and chemical composition measurements under different conditions, since the response times of cluster particle size and chemical composition detectors differ. The time-matching technique and the calibration experiments using standard clusters can be used to calibrate time differences.

[0150] The aforementioned system control device is a system control module that can control the operation of each device connected to it by signal, coordinate the operation of the sampling device, the monopolar charging device, the nanoparticle size sieving device, the mass spectrometry device, and the aerosol measurement device, and complete data acquisition and visualization. The input and output signals of all hardware in the system are calibrated and processed in real time to realize the automatic control of the system and the matching of data from multiple devices. The acquired particle size distribution, number concentration, and chemical composition data are preliminarily processed and displayed.

[0151] The first data acquisition card, the second data acquisition card, and the controller mentioned above are all conventionally used controllers. Those skilled in the art will understand that the controller's calculation, comparison, judgment, and instruction output processes can all be implemented using existing integrated circuit modules, programmable logic devices, other hardware, or by installing corresponding software modules.

[0152] The above system obtains nanoparticles of a single size after particle size sieving. These nanoparticles are then transported via a second coupling and transmission device. The number concentration of the nanoparticles is measured using an aerosol analyzer, and the corresponding chemical composition is measured using a mass spectrometer. To accurately correlate the particle size, concentration, and chemical composition, the response time corresponding to changes in the concentration and chemical composition of the nanoparticles under different measurement conditions needs to be calibrated and adjusted.

[0153] A second aspect of this invention provides a method for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers, employing the aforementioned system for analyzing the particle size distribution and chemical composition of neutral clusters smaller than 3 nanometers, comprising the following steps:

[0154] 1) Set the total transmission flow rate and the central sampling flow rate in the sampling device. After the nanoparticles are introduced into the sampling main tube of the sampling device through the total transmission flow rate, they are collected in the central sampling tube by maintaining laminar flow through the central sampling flow rate and then transported to the unipolar charging device through the central sampling flow rate.

[0155] 2) Set the discharge gas flow rate, the first power supply voltage, and the second power supply voltage in the unipolar charging device. The discharge gas flow rate is used to make the plasma generated by the discharge gas form a unipolar ion flow under the action of the first power supply voltage. Then, under the action of the second power supply voltage, the ion flow is mixed and collided with the nanoparticles in the central sampling flow to obtain charged nanoparticles, which are then transported to the first coupling transmission device.

[0156] 3) Reduce the electrostatic loss of charged nanoparticles through the first coupling transmission device, and then transport the charged nanoparticles to the nanoparticle size sieving device.

[0157] 4) In the nanoparticle size sieving device, the sheath flow rate and the third power supply voltage are set. Under the action of the electric field formed by the fixed flow field and the third power supply voltage, the charged nanoparticles are sieved along the electrode sieving area between the upper electrode plate and the lower electrode plate. The nanoparticles corresponding to the target electromigration are transported to the second coupling transmission device.

[0158] 5) The nanoparticles sieved in the second coupling and transmission device are transported to the mass spectrometry device and the aerosol number concentration device for simultaneous measurement. The chemical composition of the nanoparticles is determined in the mass spectrometry device at a fixed mass spectrometry sampling flow rate. The number concentration of the nanoparticles is determined in the aerosol number concentration device by setting the aerosol sampling flow rate.

[0159] 6) The particle size, number concentration, and chemical composition information of nanoparticles are matched by the system control device to obtain the concentration distribution and chemical composition information of nanoparticles with different particle sizes.

[0160] In step 1) above, the ratio of the total transmission flow to the central sampling flow is not less than 5, preferably 5-10.

[0161] In step 1) above, the dimensionless diffusion coefficient μ (dimensionless diffusion loss number) of the total transmission flow and the central sampling flow is less than 0.1.

[0162] In step 1) above, the central sampling flow rate is 5-10 L / min, preferably 8 L / min.

[0163] In step 2) above, the discharge gas flow rate is 0.5-1.0 L / min, preferably 1 L / min.

[0164] In step 2) above, the first power supply voltage is 2.0-3.5KV.

[0165] In step 2) above, the second power supply voltage is 1000-1300V, preferably 1200V.

[0166] In step 2) above, the frequency in the unipolar charging device is also set to 9-13KHz, preferably 10KHz.

[0167] In step 2) above, when the charged nanoparticles are transported to the first coupling transmission device, the bypass gas flow rate at the outlet of the unipolar charging device is 3-5 L / min, preferably 5 L / min.

[0168] In step 3) above, the input flow rate of charged nanoparticles in the first coupling transmission device is 3.0-5.0 L / min, preferably 3.0 L / min.

[0169] In step 3) above, the inner diameter of the passage of the first coupling transmission device is 3-5 mm, preferably 3 mm; the length of the passage of the first coupling transmission device is 11-13 cm, preferably 12 cm.

[0170] In step 4) above, the sheath flow rate is 300-1500 L / min, preferably 1200 L / min.

[0171] In step 4) above, the third power supply voltage is -10kV to 10kV.

[0172] In step 4) above, the sieving has a particle size resolution of 80 for 1.47nm particles, preferably greater than 100.

[0173] In step 5) above, the mass spectrometry sampling flow rate is 0.8 L / min.

[0174] In step 5) above, the aerosol sampling flow rate is 1-2.2 L / min.

[0175] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0176] Example 1

[0177] A neutral cluster particle size distribution and chemical composition analysis system with a diameter of less than 3 nanometers was adopted. The ratio of total transmission flow rate to central sampling flow rate was set to 5 in the sampling device. The central sampling flow rate was controlled by the back-end instrument and bypass to 8 L / min. After the nanoparticles were introduced into the sampling main tube of the sampling device through the transmission flow rate, they were collected in the central sampling tube by maintaining laminar flow through the central sampling flow rate and then transported to the unipolar charging device through the central sampling flow rate.

[0178] In the unipolar charging device, the discharge gas flow rate is set to 1 L / min, the first power supply voltage is 2 KV, the frequency is 10 KHz, and the second power supply voltage is -1200 V. The discharge gas flow rate is adjusted to make the plasma generated by the discharge gas form a unipolar ion flow under the action of the first power supply voltage. Then, under the action of the second power supply voltage, the unipolar ion flow is mixed and collided with the nanoparticles in the central sampling flow to obtain charged nanoparticles. The bypass gas flow rate at the outlet of the unipolar charging device is 5 L / min, and the input flow rate of charged nanoparticles is 3.0 L / min, which is then transported to the first coupling and transmission device.

[0179] The electrostatic loss of charged nanoparticles is reduced by a first coupling and transmission device, and then the charged nanoparticles are transported to a nanoparticle size sieving device. The inner diameter of the passage of the first coupling and transmission device is 3 mm and the length is 12 cm.

[0180] In the nanoparticle size sieving device, the sheath flow rate is set to 1200 L / min and the adjustable range of the third power supply voltage is 0-10 kV. Under the action of the electric field formed by the fixed flow field and the third power supply voltage, the charged nanoparticles are sieved along the electrode sieving area between the upper and lower electrode plates. The particle size resolution of 1.47 nm particles is greater than 100. The nanoparticles corresponding to the target electromigration are transported to the second coupling and transmission device.

[0181] The nanoparticles sieved in the second coupling and transmission device were transported to an atmospheric pressure interface time-of-flight mass spectrometer and an aerosol electrometer for simultaneous measurement. In the atmospheric pressure interface time-of-flight mass spectrometer, the mass spectrometry sampling flow rate was set to 0.8 L / min to introduce nanoparticles for chemical composition determination. In the aerosol electrometer, the aerosol sampling flow rate was set to 2.2 L / min to introduce nanoparticles for number concentration determination.

[0182] By matching the particle size, number concentration, and chemical composition information of nanoparticles through a system control device, the concentration distribution and chemical composition information of nanoparticles with different particle sizes can be obtained.

[0183] Example 2

[0184] A particle size distribution and chemical composition analysis system for particles smaller than 3 nanometers is used. The ratio of total transmission flow rate to central sampling flow rate is set to 6 in the sampling device. The central sampling flow rate is controlled by the back-end instrument and bypass at 9 L / min. After the nanoparticles are introduced into the sampling main tube of the sampling device through the transmission flow rate, they are collected in the central sampling tube under laminar flow through the central sampling flow rate and then transported to the unipolar charging device through the central sampling flow rate.

[0185] In the unipolar charging device, the discharge gas flow rate is set to 0.8 L / min, the first power supply voltage is 3 KV, the frequency is 12 KHz, and the second power supply voltage is 1100 V. The discharge gas flow rate is adjusted to make the plasma generated by the discharge gas form a unipolar ion flow under the action of the first power supply voltage. Then, under the action of the second power supply voltage, the unipolar ion flow is mixed and collided with the nanoparticles in the central sampling flow to obtain charged nanoparticles. The bypass gas flow rate at the outlet of the unipolar charging device is 4 L / min, and the input flow rate of charged nanoparticles is 4.0 L / min, which is then transported to the first coupling and transmission device.

[0186] The electrostatic loss of charged nanoparticles is reduced by a first coupling and transmission device, and then the charged nanoparticles are transported to a nanoparticle size sieving device. The inner diameter of the passage of the first coupling and transmission device is 4 mm and the length is 11 cm.

[0187] In the nanoparticle size sieving device, the sheath flow rate is set to 1000 L / min and the adjustable range of the third power supply voltage is -10 kV to 10 kV. Under the action of the electric field formed by the fixed flow field and the third power supply voltage, the charged nanoparticles are sieved along the electrode sieving area between the upper and lower electrode plates. The particle size resolution of 1.47 nm particles is greater than 90. The nanoparticles corresponding to the target electromigration are transported to the second coupling transmission device.

[0188] The nanoparticles sieved in the second coupling and transmission device are transported to an atmospheric pressure interface time-of-flight mass spectrometer and an aerosol electrometer for simultaneous measurement. In the atmospheric pressure interface time-of-flight mass spectrometer, the mass spectrometry sampling flow rate is set to 0.8 L / min to introduce nanoparticles for chemical composition determination. In the aerosol electrometer, the aerosol sampling flow rate is set to 2 L / min to introduce nanoparticles for number concentration determination.

[0189] By matching the particle size, number concentration, and chemical composition information of nanoparticles through a system control device, the concentration distribution and chemical composition information of nanoparticles with different particle sizes can be obtained.

[0190] Test Example 1

[0191] A group of nanoparticles generated by electrospray scattering were analyzed using the method described in Example 1. Based on the particle number concentration information measured by an aerosol electrometer under different particle size sieving conditions and the mass spectrometry information measured by atmospheric pressure interface time-of-flight mass spectrometry, the particle size distribution and chemical composition information of the nanoparticles obtained by the electrospray method were obtained. The results are as follows: Figure 7a , Figure 7b As shown. Electrospraying sulfuric acid solution was used to obtain information on the electromobility, particle size, and mass-to-charge ratio of each sulfuric acid cluster. The particle size distribution results are presented in the data. Figure 7a ) and mass spectrometry results at different electromobilities ( Figure 7b It can be found that nanoclusters of different particle sizes generated by electrospray can be effectively screened and measured by this system.

[0192] Test Example 2

[0193] Nanoparticles generated by electrospraying were measured using the analytical method of Example 1 of this invention and the method disclosed in Chinese Patent ZL202311442677.6. Under the same electrospraying operating conditions, by adjusting the particle size sieving voltage, and combining the particle number concentration information obtained from the aerosol electrometer and the mass spectrometry information obtained from the atmospheric pressure interface time-of-flight mass spectrometry, the responses of the two methods to different particle sizes were compared. The results are as follows. Figure 8 As shown in the figure. Measurement results indicate that the analytical system described in this invention achieves high signal response for particulate matter measurements of different sizes, reflecting its high transmission efficiency and detection sensitivity. Therefore, the system and analytical method provided by this invention are applicable to a wider range of nanoparticle analysis applications, such as environmental monitoring, atmospheric science research, nanomaterial characterization, bioaerosol analysis, and ultrafine particle monitoring in industrial processes.

[0194] In summary, the present invention provides a system and method for analyzing the size distribution and chemical composition of neutral clusters smaller than 3 nanometers. Based on central sample flow sampling, it achieves efficient sampling of nanoparticles. Utilizing the high charging efficiency of a unipolar charging device, the nanoparticles are charged and efficiently transported to the inlet of a nanoparticle size sieving device. Through a special aerodynamic design, the nanoparticles are efficiently transported through the electric field between the electrode plates to the particle number concentration and chemical composition detectors, demonstrating excellent application prospects. Therefore, the present invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0195] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A system for analysis of neutral cluster size distribution and chemical composition below 3 nanometers, characterized by, The system comprises a sampling device, a single-pole charging device, a first coupling transmission device, a nanoparticle size screening device, a second coupling transmission device, a mass spectrometry device, an aerosol number concentration measuring device, and a system control device. The first coupling transmission device comprises a stacking area, which comprises a first stacking section and a second stacking section. The second coupling transmission device comprises an ion flight chamber, which is provided with an insulating coupler and a stainless steel coupler from the inside to the outside.

2. The sub-3 nanometer neutral cluster size distribution and chemical composition analysis system of claim 1, wherein, The sampling device comprises a sampling main pipe and a central sampling pipe, which are connected in sequence along the particle input direction.

3. The sub-3 nanometer neutral cluster size distribution and chemical composition analysis system of claim 2, wherein, The monopole charging device comprises a tube body, the tube body is provided with sealed joints at both ends, the input end of the tube body is provided with an inlet pipe as a particle inlet, the inlet pipe extends into the tube body after penetrating through the sealed joint, the output end of the tube body is provided with an outlet pipe as a particle outlet, the outlet pipe extends into the tube body after penetrating through the sealed joint, the tube body is communicated with a sampling device through the inlet pipe, the tube body is communicated with a first coupling transmission device through the outlet pipe, an internal tube is arranged in the tube body, the internal tube is sleeved on the part of the inlet pipe extending into the tube body and keeps a distance from the end of the outlet pipe extending into the tube body, a discharge gas inlet and a dielectric barrier discharge electrode are sequentially arranged on the outer wall of the tube body along the input direction of the particles, the dielectric barrier discharge electrode is arranged in a circular ring shape along the circumference of the outer wall of the tube body, the discharge gas inlet is communicated with the inside of the tube body, an ion trapping electrode is arranged on the inner wall of the tube body outside the part of the outlet pipe extending into the tube body, and the ion trapping electrode is arranged in a circular ring shape along the circumference of the inner wall of the tube body.

4. The sub-3 nanometer neutral cluster size distribution and chemical composition analysis system of claim 3, wherein, The nanoparticle size screening device comprises a fixed electric field and a fixed flow field, the fixed electric field is sequentially provided with upper and lower electrode plates along the input direction of the particles, the upper and lower electrode plates are parallel and keep a distance between the upper and lower electrode plates to form a sheath gas channel as an electrode screening area, the upper and lower electrode plates are respectively provided with slits, the slits of the upper electrode plate are connected with an aerosol inlet outside, the slits of the lower electrode plate are aerosol outlets, and the upper electrode plate is connected with a third power supply; the fixed flow field comprises a sheath flow closed loop passing through the sheath gas channel, the inlet of the sheath gas channel is provided with a sheath gas inlet, the sheath flow closed loop outside the sheath gas channel is sequentially provided with a second particle filter, a temperature and humidity sensor, a sheath gas cooling device and a circulating fan along the direction away from the sheath gas inlet.

5. The sub-3 nanometer neutral cluster size distribution and chemical composition analysis system of claim 1, wherein, The system control device comprises a first data acquisition card, a second data acquisition card and a controller, the first data acquisition card is used for acquiring chemical component information data measured by a mass spectrum measuring device, the second data acquisition card is used for acquiring particle size information and number concentration data of the nanoparticle measured by a nanoparticle size screening device, and the controller obtains the number concentration distribution and chemical component information of the nanoparticles with different particle sizes through time matching technology.

6. The sub-3 nanometer neutral cluster size distribution and chemical composition analysis system of claim 4, wherein, Any one or more of the following conditions is included: A11) In the monopole charging device, the inlet pipe is communicated with a central sampling pipe; A12) In the monopole charging device, the length of the internal tube along the axial direction is greater than the length of the part of the inlet pipe extending into the tube body along the axial direction; A13) In the monopole charging device, the axial distance between the end of the internal tube close to the outlet pipe and the end of the outlet pipe extending into the tube body is 9-11 mm; A14) In the monopole charging device, the vertical distance between the end of the internal tube close to the outlet pipe and the dielectric barrier discharge electrode is 9-11 mm; A15) In the monopole charging device, the vertical distance between the ion trapping electrode and the end of the outlet pipe extending into the tube body is 9-11 mm; A16) In the unipolar charging device, the discharge gas inlet introduces inert gas; A17) In the unipolar charging device, the dielectric barrier discharge electrode is connected with a first power supply; A18) In the unipolar charging device, the ion trapping electrode is connected with a second power supply; A21) In the first coupling transmission device, the input end of the first transmission inlet pipe is connected with the outlet pipe of the unipolar charging device, and the output end of the first transmission outlet pipe is connected with the aerosol inlet of the nanoparticle size screening device; A22) In the first coupling transmission device, a plurality of resistors are arranged in series in the integrated circuit experimental board, the resistors correspond to the number of metal electrodes and are connected with the corresponding metal electrodes, one end of the integrated circuit experimental board is connected with the nanoparticle screening device in series, and the other end of the integrated circuit experimental board is connected with the unipolar charging device in series and grounded; A31) In the nanoparticle size screening device, the aerosol inlet is connected with the first coupling transmission device, and the aerosol outlet is connected with the second coupling transmission device; A32) In the nanoparticle size screening device, the thickness of the upper electrode plate and the lower electrode plate is 0.1-1 cm; A33) In the nanoparticle size screening device, the length of the upper electrode plate and the lower electrode plate along the parallel sheath gas channel is 20-30 cm, and the width of the upper electrode plate and the lower electrode plate along the vertical sheath gas channel is 3-5 cm; A34) In the nanoparticle size screening device, the horizontal distance between the slits of the upper electrode plate and the slits of the lower electrode plate is 3-5 cm; A35) In the nanoparticle size screening device, the width of the slit on the upper electrode plate for aerosol sampling is 0.5-0.7 mm, and the width of the slit on the lower electrode plate for the aerosol outlet is 0.1-0.2 mm; A36) In the nanoparticle size screening device, the inlet of the sheath gas channel in the sheath gas inflow electrode screening area is a prismatic tapered mouth, the angle between the wall of the inlet of the sheath gas channel and the central axis of the sheath gas channel is 25-35°, the outlet of the sheath gas channel in the sheath gas outflow electrode screening area is a prismatic tapered mouth, and the angle between the wall of the outlet of the sheath gas channel and the central axis of the sheath gas channel is 25-35°; A41) In the second coupling transmission device, the inlet of the ion flight chamber is coaxial with the aerosol outlet of the nanoparticle size screening device, and the inlet of the ion flight chamber is connected with the aerosol outlet of the nanoparticle size screening device and has the same inner diameter; A42) In the second coupling transmission device, the ion flight chamber is a particle transmission pipe, and the inner diameter of the ion flight chamber is 0.5-2 mm; A43) In the second coupling transmission device, the distance between the outlet of the ion flight chamber and the inlet of the mass spectrometry device is 0.5-1.0 cm; A44) In the second coupling transmission device, the number concentration sampling port is located in the radial direction of the ion flight chamber.

7. The sub-3 nanometer neutral cluster size distribution and chemical composition analysis system of claim 6, wherein, Any one or more of the following conditions is included: A161) In A16), the inert gas is helium. A311) In A31), the aerosol inlet is in communication with the first transmission outlet.

8. A method for analyzing the size distribution and chemical composition of neutral clusters below 3 nanometers, using the system for analyzing the size distribution and chemical composition of neutral clusters below 3 nanometers according to any one of claims 1-7, comprising the following steps: 1) In the sampling device, set the total transmission flow rate and the central sampling flow rate, introduce the nanoparticles into the sampling main pipe of the sampling device through the total transmission flow rate, keep the layer flow in the central sampling pipe through the central sampling flow rate, and then transport the nanoparticles to the single-pole charging device through the central sampling flow rate; 2) In the single-pole charging device, set the discharge gas flow rate, the first power supply voltage, and the second power supply voltage, pass the discharge gas through the discharge gas flow rate to generate plasma, form a single-pole ion flow under the action of the first power supply voltage, and then make the ion flow collide with the nanoparticles in the central sampling flow rate under the action of the second power supply voltage to obtain charged nanoparticles, and then transport the charged nanoparticles to the first coupling transmission device; 3) Reduce the electrostatic loss of the charged nanoparticles through the first coupling transmission device, and then transport the charged nanoparticles to the nanoparticle size screening device; 4) In the nanoparticle size screening device, set the sheath flow rate and the third power supply voltage, and under the action of the fixed flow field and the electric field formed by the third power supply voltage, the charged nanoparticles are screened along the electrode screening area between the upper electrode plate and the lower electrode plate, and the nanoparticles corresponding to the required target electric migration are transported to the second coupling transmission device; 5) The screened nanoparticles in the second coupling transmission device are transported to the mass spectrometry device and the aerosol number concentration measuring device for synchronous measurement, the chemical composition of the nanoparticles is measured in the mass spectrometry device under the fixed mass spectrometry sampling flow rate, and the aerosol sampling flow rate is set in the aerosol number concentration measuring device to introduce the nanoparticles to measure the number concentration of the nanoparticles; 6) Match the particle size, number concentration, and chemical composition information of the nanoparticles through the system control device to obtain the concentration distribution and chemical composition information of nanoparticles of different particle sizes.

9. The method of claim 8, wherein the neutral cluster size distribution and chemical composition analysis is performed at a sub-3 nanometer scale. Any one or more of the following conditions: B1) In step 1), the ratio of the total transmission flow rate to the central sampling flow rate is not less than 5; B2) In step 1), the central sampling flow rate is 5-10 L / min; B3) In step 2), the discharge gas flow rate is 0.5-1.0 L / min; B4) In step 2), the first power supply voltage is 2.0-3.5 KV; B5) In step 2), the second power supply voltage is 1000-1300 V; B6) In step 2), the frequency in the single-pole charging device is 9-13 KHz; B7) In step 2), when the charged nanoparticles are transported to the first coupling transmission device, the bypass gas flow rate at the outlet of the single-pole charging device is 3-5 L / min; B8) In step 3), in the first coupling transmission device, the input flow rate of the charged nanoparticles is 3.0-5.0 L / min; B9) In step 4), the sheath flow rate is 300-1500 L / min; B10) in step 4), the third power supply voltage is -10 kV ~ 10 kV; B11) in step 4), the particle size resolution of the sieving to 1.47 nm particulate matter is greater than 80; B12) in step 5), the mass spectrometric sampling flow rate is 0.8 L / min; B13) in step 5), the aerosol sampling flow rate is 1-2.2 L / min.

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