An apparatus for detecting the hygroscopic growth of single aerosol nanoparticles based on a planar chip by dark-field microscopy

Abstract

The present invention discloses a device for detecting the hygroscopic growth of single aerosol nanoparticles based on a planar chip, comprising: an image plane detector (1), an imaging tube lens (2), an air objective lens (3), a control chamber (4), a planar chip (5), a 750 nm filter (6), and a 750 nm LED light source (7). The planar chip (5) is composed of a cover glass (8), a top multilayer dielectric film (9), a scattering layer (10), and a bottom multilayer dielectric film (11). After the collimated light beam emitted by the LED light source is incident on the planar chip, the light beam exits as a hollow conical light and irradiates the aerosol particles deposited on the planar chip. The scattered light of the aerosol particles is received by the imaging system to form dark field imaging. When the nano-aerosol undergoes hygroscopic growth due to the increase in the surrounding environmental humidity, the scattering signal of the nano-aerosol will change significantly. By detecting the scattering intensity of the nano-aerosol on the detector, the hygroscopicity of the particles can be measured in real time.

Description

Technical Field

[0001] The present invention relates to real-time detection of the hygroscopic growth process of single nanometer aerosol particles, and in particular to high signal-to-noise ratio, high sensitivity, and label-free detection using a dark-field microscope based on a planar chip. Specifically, the invention relates to a device for detecting the hygroscopic growth of single aerosol nanoparticles using a dark-field microscope based on a planar chip, and belongs to the technical field of nanometer aerosol particle detection in the atmospheric environment. Background Art

[0002] The hygroscopic growth of atmospheric aerosols as they absorb water from the atmosphere changes the size and chemical composition of the aerosols, significantly affecting their size distribution, deposition characteristics, and chemical reactivity. Changes in the size and chemical composition of aerosols seriously affect the optical properties, thereby affecting atmospheric visibility and regional or global climate. In addition, aerosols also have a serious impact on human health. Especially nanoaerosols, which are the main precursors of larger particles. Traditional means of studying aerosol hygroscopicity include hygroscopic tandem differential mobility analyzers, environmental scanning electron microscopes, etc. The hygroscopic tandem differential mobility analyzer studies the average effect of particle hygroscopicity and cannot study single particles. The scanning electron microscope, due to its high-energy electron beam, will destroy aerosol particles during the measurement process. The above-mentioned main microscopy techniques have great limitations in practical applications, and the problems they have are:

[0003] 1. Unable to detect single particles. The moisture absorption series differential analyzer can only detect the average effect of the size change of a large number of particles after passing through the humidification tube, and cannot analyze the actual changes of a single particle in a specific environment.

[0004] 2. Non-destructive testing of single particles. Environmental scanning electron microscopes (ESEMs) offer high-resolution imaging capabilities, but their high-energy electron beams are extremely destructive to single particles, especially smaller ones. Furthermore, because they operate in a high vacuum environment, they can only simulate relative humidity and cannot operate in real atmospheric humidity.

[0005] 3. It is impossible to directly observe particulate matter. The moisture absorption series differential analyzer cannot detect the dynamic process of particulate matter in a changing environment in real time.

[0006] 4. Large size. Traditional optical detection technologies, such as surface wave detection technology, require a large optical path and complex equipment components.

[0007] 5. Complex operation. Traditional aerosol moisture absorption detection technology requires complex and expensive equipment and requires operators to undergo professional training before they can operate it. Summary of the Invention

[0008] The object of the present invention is to overcome the drawbacks of traditional atmospheric aerosol detection methods, that is, traditional detection techniques cannot perform label-free, non-invasive, real-time detection of single particles and are complicated to operate. A device for detecting the hygroscopic growth of single aerosol nanoparticles based on a planar chip by dark-field microscopy is proposed. By means of the underlying multi-layer dielectric film to improve the light energy utilization rate, the uniform scattering of the scattering layer and the angular selection of the top multi-layer dielectric film for the outgoing light beam, as well as the selection of the numerical aperture of the imaging system for collecting the scattered light, real-time monitoring of the hygroscopic growth of single nano-aerosol particles by on-chip dark-field microscopy is achieved. This method has the characteristics of high signal-to-noise ratio, high sensitivity, label-free, and non-invasive detection of single nano-aerosol particles.

[0009] The present invention realizes the above technical solution as follows: [[ID=Z4]]

[0010] A device for detecting the hygroscopic growth of single aerosol nanoparticles based on a planar chip by dark-field microscopy, comprising an image plane detector, an imaging tube lens, an air objective lens, a control chamber, a planar chip, a 750 nm filter and a 750 nm LED light source. The planar chip is composed of a cover glass, a top multi-layer dielectric film, a scattering layer and an underlying multi-layer dielectric film which are stacked in sequence from top to bottom. Among them, the 750 nm LED light source (7) emits a collimated 750 nm light beam which is incident on the underlying multi-layer dielectric film (11) in the planar chip (5) through the 750 nm filter (6); since the energy band of the underlying multi-layer dielectric film is fully transparent when the numerical aperture of the light beam is less than 0.2, the collimated 750 nm light beam directly transmits and hits the scattering layer (10) and is uniformly scattered, generating propagation wave vectors at various angles and incident on the top multi-layer dielectric film (9); the scattered 750 nm light beam is screened by the energy band of the top multi-layer dielectric film (9); the light beam with a numerical aperture less than 0.7 in the scattered light is reflected back to the scattering layer (10) by the top multi-layer dielectric film (9), and under the limitation of the underlying multi-layer dielectric film (11), part of the scattered light beam is incident on the top multi-layer dielectric film (9) again; while the light beam with a numerical aperture greater than 0.7 in the scattered light directly exits as a hollow conical light beam and irradiates the nano-aerosol deposited on the cover glass (8); the environmental humidity of the irradiated nano-aerosol is controlled by the control chamber (4); the control chamber (4) can change the relative humidity of the chamber environment (the regulated relative humidity range is 60%-95%), thereby changing the physical and chemical properties of the aerosol and causing its optical properties to change; the change in the scattered light of the irradiated nano-aerosol is collected by the air objective lens (3), and since the collection numerical aperture of the air objective lens is less than the outgoing numerical aperture of the light beam of the planar chip, the air objective lens only collects the pure scattered light of the particles, and the scattered light passes through the imaging tube lens (2) and finally forms a dark-field image of the nano-aerosol on the image plane detector (1).

[0011] Furthermore, the top multi-layer dielectric film is composed of a SiO2 dielectric film with a refractive index of 1.45 to 1.5 and a thickness of 95 to 100 nm, and a first SiN dielectric film with a refractive index of 2.36 to 2.5 and a thickness of 80 to 88 nm, which are alternately deposited by chemical vapor deposition on a cover glass with a thickness of 0.17 to 0.2 mm. For example, the top multi-layer dielectric film is composed of a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 100 nm, and a first SiN dielectric film with a refractive index of 2.36 and a thickness of 88 nm, which are alternately (for example, a total of 10 pairs) deposited by plasma enhanced chemical vapor deposition on a 0.17 mm thick cover glass. For example, the number of layers of the top multi-layer dielectric film is 18 to 20 layers. x The dielectric film is alternately deposited by chemical vapor deposition on a cover glass with a thickness of 0.17 to 0.2 mm. For example, the top multi-layer dielectric film is composed of a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 100 nm, and a first SiN dielectric film with a refractive index of 2.36 and a thickness of 88 nm, which are alternately (for example, a total of 10 pairs) deposited by plasma enhanced chemical vapor deposition on a 0.17 mm thick cover glass. For example, the number of layers of the top multi-layer dielectric film is 18 to 20 layers. x For example, the top multi-layer dielectric film is composed of a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 100 nm, and a first SiN dielectric film with a refractive index of 2.36 and a thickness of 88 nm, which are alternately (for example, a total of 10 pairs) deposited by plasma enhanced chemical vapor deposition on a 0.17 mm thick cover glass. For example, the number of layers of the top multi-layer dielectric film is 18 to 20 layers.

[0012] The bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.2 to 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.9 to 2.0 and a thickness of 90 nm, which are alternately (for example, a total of 18 pairs) deposited by plasma enhanced chemical vapor deposition on a cover glass with a thickness of 0.17 to 0.2 mm. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.45 to 1.5 and a thickness of 139 to 150 nm and a first SiN dielectric film with a refractive index of 2.36 to 2.5 and a thickness of 100 to 110 nm are alternately deposited. x For example, the bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.2 to 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.9 to 2.0 and a thickness of 90 nm, which are alternately (for example, a total of 18 pairs) deposited by plasma enhanced chemical vapor deposition on a cover glass with a thickness of 0.17 to 0.2 mm. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.45 to 1.5 and a thickness of 139 to 150 nm and a first SiN dielectric film with a refractive index of 2.36 to 2.5 and a thickness of 100 to 110 nm are alternately deposited. x For example, the bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.2 to 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.9 to 2.0 and a thickness of 90 nm, which are alternately (for example, a total of 18 pairs) deposited by plasma enhanced chemical vapor deposition on a cover glass with a thickness of 0.17 to 0.2 mm. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.45 to 1.5 and a thickness of 139 to 150 nm and a first SiN dielectric film with a refractive index of 2.36 to 2.5 and a thickness of 100 to 110 nm are alternately deposited. x For example, the bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.2 to 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.9 to 2.0 and a thickness of 90 nm, which are alternately (for example, a total of 18 pairs) deposited by plasma enhanced chemical vapor deposition on a cover glass with a thickness of 0.17 to 0.2 mm. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.45 to 1.5 and a thickness of 139 to 150 nm and a first SiN dielectric film with a refractive index of 2.36 to 2.5 and a thickness of 100 to 110 nm are alternately deposited.

[0013] For example, the bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.92 and a thickness of 90 nm, which are alternately (a total of 18 pairs) deposited by chemical vapor deposition on a 0.17 mm thick cover glass. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 139 nm and a first SiN dielectric film with a refractive index of 2.36 and a thickness of 100 nm are alternately deposited. x For example, the bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.92 and a thickness of 90 nm, which are alternately (a total of 18 pairs) deposited by chemical vapor deposition on a 0.17 mm thick cover glass. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 139 nm and a first SiN dielectric film with a refractive index of 2.36 and a thickness of 100 nm are alternately deposited. x For example, the bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.92 and a thickness of 90 nm, which are alternately (a total of 18 pairs) deposited by chemical vapor deposition on a 0.17 mm thick cover glass. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 139 nm and a first SiN dielectric film with a refractive index of 2.36 and a thickness of 100 nm are alternately deposited. x For example, the bottom multi-layer dielectric film 11 is composed of a second SiN dielectric film with a refractive index of 2.32 and a thickness of 73 nm, and a third SiN dielectric film with a refractive index of 1.92 and a thickness of 90 nm, which are alternately (a total of 18 pairs) deposited by chemical vapor deposition on a 0.17 mm thick cover glass. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 139 nm and a first SiN dielectric film with a refractive index of 2.36 and a thickness of 100 nm are alternately deposited.

[0014] Among them, the top multi-layer dielectric film and the scattering layer are adhered together with a refractive index matching oil (refractive index of 1.51).

[0015] Among them, the planar chip is composed of a cover glass for carrying the sample, a top multi-layer dielectric film for controlling the light flow, a scattering layer for providing various propagation wave vectors, and a bottom multi-layer dielectric film for improving the light energy utilization efficiency.

[0016] Among them, the 750nm LED light source emits broadband light with a central wavelength of 750nm. After passing through a 750nm filter with a bandwidth of 10nm, it is incident on the bottom multi-layer dielectric film of the planar chip.

[0017] Among them, due to the energy band design of the bottom multi-layer dielectric film, the light beam directly transmits through the bottom multi-layer dielectric film and is incident on the scattering layer. The scattering layer scatters the light beam into wave vectors in various propagation directions and is incident on the top multi-layer dielectric film.

[0018] Among them, the top multi-layer dielectric film performs transmission selection on the incident scattered light beam. The light with a numerical aperture less than 0.7 will be reflected back to the scattering layer and reflected back to the top through the bottom multi-layer dielectric film; while the light beam with a numerical aperture greater than 0.7 will pass through the top multi-layer dielectric film, making the light beam exit as a hollow conical light beam.

[0019] Specifically, a device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip by dark field microscopy, the device includes: an image plane detector (1), an imaging tube lens (2), an air objective lens (3), a control cavity (4), a planar chip (5), a 750nm filter (6) and a 750nm LED light source (7); wherein the planar chip (5) is composed of a cover glass (8) for carrying a sample, a top multi-layer dielectric film (9) for controlling the light flow, a scattering layer (10) for providing wave vectors propagating in various angles, and a bottom multi-layer dielectric film (11) for improving the light energy utilization efficiency, which are stacked from top to bottom in sequence;

[0020] Among them, the 750nm LED light source emits a collimated 750nm light beam that passes through a 750nm filter (6) and is incident on the bottom multi-layer dielectric film (11) in the planar chip (5). Since the energy band of the bottom multi-layer dielectric film is fully transmissive when the numerical aperture of the light beam is less than 0.2, the collimated 750nm light beam is directly transmitted and hits the scattering layer (10) and is evenly scattered, generating propagation wave vectors at various angles and being incident on the top multi-layer dielectric film (9). Under the energy band limitation of the top multi-layer dielectric film (9), the scattered 750nm light beam is screened. The light beam with a numerical aperture less than 0.7 in the scattered light is reflected back to the scattering layer (10) by the top multi-layer dielectric film (9), and under the limitation of the bottom multi-layer dielectric film (11), part of the scattered light beam is incident on the top multi-layer dielectric film (9) again. The light beam with a numerical aperture greater than 0.7 in the scattered light directly exits as a hollow conical light beam and irradiates the nano-aerosol deposited on the cover glass (8). The environmental humidity of the irradiated nano-aerosol is controlled by the control chamber (4). The control chamber (4) can change the relative humidity of the chamber environment (regulating the relative humidity range of 60%-95%), thereby changing the physical and chemical properties of the aerosol and causing its optical properties to change. The change in the scattered light of the irradiated nano-aerosol is collected by the air objective lens (3). Since the collection numerical aperture of the air objective lens is less than the exit numerical aperture of the planar chip light beam, the air objective lens only collects the pure scattered light of the particles. The scattered light then passes through the imaging tube lens (2) and finally forms an image on the image plane detector (1), achieving a high-contrast (the high contrast means that the particle contrast of 100nm reaches 0.1) dark-field imaging of the nano-aerosol, realizing a real-time monitoring imaging system for single nano-aerosol without labeling and non-invasive.

[0021] Further, the collimation requirement of the 750nm LED light beam is not high. The so-called not high collimation requirement means that as long as the numerical aperture of the light beam is less than 0.2, and its incident collimation requirement is determined by the bottom multi-layer dielectric film (11).

[0022] Further, the scattering layer (10) can scatter the incident collimated light beam into propagation wave vectors at various angles and be incident on the top multi-layer dielectric film (9).

[0023] Further, the top multi-layer dielectric film (9) can control the transmission angle of the light beam, so that the light beam with a numerical aperture greater than 0.7 exits to illuminate the nano-aerosol particles deposited on the cover glass (8).

[0024] Furthermore, an imaging system composed of an air objective lens (3), an imaging tube lens (2), and an image plane detector (1) has a numerical aperture (e.g., 0.6) smaller than the numerical aperture of the light beam emitted from the planar chip (e.g., 0.7), enabling high-contrast (a 100-nm particle contrast of 0.1) and label-free dark-field imaging of nano-aerosols.

[0025] Furthermore, the control chamber (4) can stably control the humidity change in the environment around the nano-aerosol. By changing the humidity inside the control chamber, the nano-aerosol undergoes hygroscopic growth, thereby changing its physical and chemical properties, and consequently causing a change in its optical properties. The imaging system composed of an air objective lens (3), an imaging tube lens (2), and an image plane detector (1) monitors the optical changes of the nano-aerosol in real time.

[0026] Furthermore, the device measures the hygroscopic growth of 100-nm atmospheric aerosol particles in real time by detecting the change in the scattered light intensity of the nano-aerosol particles. The exposure time of the image plane detector (1) is 100 ms, and its time resolution reaches the level of 100 milliseconds.

[0027] Furthermore, the device can achieve imaging and detection systems with different fields of view and different resolutions by designing the energy bands of the top multi-layer dielectric film (9) and the bottom multi-layer dielectric film (11) and selecting collection air objective lenses (3) with different numerical apertures.

[0028] Among them, the multi-layer dielectric film is composed of SiO2 and silicon nitride nano-films with different refractive indices.

[0029] Among them, the scattered light of the nano-aerosol particles is collected by an air objective lens with a numerical aperture smaller than that of the planar chip, passed through the imaging tube lens, and imaged on the image plane detector to perform dark-field imaging on the nano-aerosol particles.

[0030] Among them, an air objective lens with a numerical aperture of 0.6 and a magnification of 40 times, together with the imaging tube lens and the image plane detector, provides large-field dark-field imaging.

[0031] Among them, the control chamber changes the humidity in the environment around the nano-aerosol, and the image plane detector detects the change in the scattered light of the nano-aerosol in real time.

[0032] In the present invention, the first SiN x The dielectric film refers to the dielectric film formed by the first SiN x The second SiN x The dielectric film refers to the dielectric film formed by the second SiN x The third SiN x The dielectric film refers to the dielectric film formed by the third SiNx The formed dielectric thin film. The first SiN x , the second SiN x , the third SiN x has different refractive indices.

[0033] The principle of the technical solution of the present invention is as follows: A device for detecting the hygroscopic growth of single aerosol nanoparticles by dark-field microscopy based on a planar chip. By designing the top multi-layer dielectric thin film, the bottom multi-layer dielectric thin film, and the scattering of the light beam by the scattering layer, after a light beam with relatively low collimation is incident on the planar chip, it exits as a large-angle conical hollow light beam and irradiates the nano-aerosol particles deposited on the surface. An imaging system with a small numerical aperture is used to collect the pure scattered light of the nano-aerosol. Dark-field imaging of the nano-aerosol is realized. By integrating the scattered intensity on the imaging detector, label-free real-time detection of the hygroscopic growth of single nano-aerosol particles is achieved.

[0034] The advantages of the present invention compared with the existing imaging technologies are as follows:

[0035] 1. Label-free detection: The technology of detecting nano-aerosols by dark-field microscopy based on a planar chip is a label-free imaging and detection technology, which reduces the influence on aerosol particles during the detection process. It more truly reflects the dynamic process of aerosol hygroscopicity.

[0036] 2. Wide-field imaging: The imaging field of view is determined by the energy band of the top multi-layer dielectric thin film and the numerical aperture of the air objective lens. The energy band structure of the top multi-layer film can be freely designed to achieve wide-field imaging.

[0037] 3. Simple device: The system consists of an ordinary upright microscope, a planar chip, and a light source. There are no mechanical moving parts, and the requirements for the collimation and uniformity of the incident light are low, which is convenient for non-professional personnel to operate.

[0038] 4. High integration: Compared with the traditional method of using an objective lens with a special structure to achieve dark-field illumination, the thickness of the planar chip is in the range of several millimeters, realizing integration.

[0039] 5. Low usage cost: Based on a pure optical detection method, the equipment cost is low, the consumables are used less, and the processing of the multi-layer dielectric thin film is simple and inexpensive.

[0040] 6. Diverse usage environments: Since the collecting objective lens is an air objective lens rather than an oil immersion lens, the device of the present invention is more suitable for the detection of outdoor atmospheric particles. Brief Description of the Drawings

[0041] Figure 1 It is a schematic structural diagram of a device for detecting the hygroscopic growth of single aerosol nanoparticles by dark-field microscopy based on a planar chip according to the present invention;

[0042] Figure 2 Schematic diagram of the principle of a planar chip

[0043] Figure 3 Dark-field imaging images of 100-nm sodium chloride particles using a planar chip at different relative humidities

[0044] Figure 4 Results of the process detection for measuring the hygroscopic growth of typical atmospheric particles using this device

[0045] Figure 1 In [the figure], 1 is an image plane detector; 2 is an imaging tube lens; 3 is an air objective lens; 4 is a control chamber; 5 is a planar chip; 6 is a 750-nm filter; 7 is a 750-nm LED light source

[0046] Figure 2 In [the figure], 8 is a cover glass; 9 is a top multilayer dielectric film; 10 is a scattering layer; 11 is a bottom multilayer dielectric film Specific implementation manner

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners

[0048] A dark-field microscope for detecting the hygroscopic growth of single aerosol nanoparticles based on a planar chip according to the present invention includes: an image plane detector, an imaging tube lens, an air objective lens, a control chamber, a planar chip, a 750-nm filter, and a 750-nm LED light source. The planar chip is composed of a cover glass for carrying a sample, a top multilayer dielectric film for controlling the light flow, a scattering layer for providing various propagation wave vectors, and a bottom multilayer dielectric film for improving the light energy utilization efficiency

[0049] Among them, the 750-nm LED light source emits broadband light with a central wavelength of 750 nm, which is incident on the planar chip after passing through a 750-nm filter with a bandwidth of 10 nm

[0050] Among them, the top multilayer dielectric film is composed of a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 100 nm and a first SiN x dielectric film with a refractive index of 2.36 and a thickness of 88 nm, which are alternately (a total of 10 pairs) deposited on a 0.17-mm-thick cover glass by chemical vapor deposition

[0051] Among them, the bottom multilayer dielectric film is composed of a second SiN x dielectric film with a refractive index of 2.32 and a thickness of 73 nm and a third SiN xAfter 18 pairs of alternating (total 18 pairs) dielectric thin films are deposited by chemical vapor deposition on a 0.17 mm thick cover glass, on this basis, SiO2 with a refractive index of 1.46 and a thickness of 139 nm and the first SiN with a refractive index of 2.36 and a thickness of 100 nm are alternately deposited. x of dielectric thin films (total 11 pairs).

[0052] Among them, the scattering layer is formed by doping 60 nm titanium dioxide particles in SOG glue and then spin-coating on the bottom multi-layer dielectric thin film, with a thickness of 2 μm.

[0053] Among them, the top multi-layer dielectric thin film and the scattering layer are adhered together with a refractive index matching oil (refractive index of 1.51).

[0054] Among them, the bottom multi-layer dielectric thin film allows a beam with a relatively high collimation (beam numerical aperture less than 0.2) to pass through, and the top multi-layer dielectric thin film allows a beam with a numerical aperture greater than 0.7 to pass through and blocks a beam with a numerical aperture less than 0.7.

[0055] Among them, the scattering layer is to provide light beams at various angles to be incident on the top multi-layer dielectric thin film.

[0056] Among them, the cover glass and the top multi-layer dielectric thin film are adhered together through the refractive index matching oil.

[0057] Among them, the top multi-layer dielectric thin film performs transmission selection on the incident scattered light beams. Light with a numerical aperture less than 0.7 will be reflected back to the scattering layer and then reflected back to the top through the bottom multi-layer dielectric thin film; while light beams with a numerical aperture greater than 0.7 will pass through the top multi-layer dielectric thin film, making the light beams exit as a hollow conical beam.

[0058] Among them, the scattered light of the nano-aerosol particles is collected by an air objective lens with a numerical aperture of 0.6 and a magnification of 40 times, passes through an imaging tube lens, and is imaged on an image plane detector to perform dark-field imaging on the nano-aerosol particles.

[0059] Among them, the air objective lens with a numerical aperture of 0.6 and a magnification of 40 times, together with the imaging tube lens and the image plane detector, provides a large field of view and high signal-to-noise ratio dark-field images.

[0060] Among them, by setting the corresponding relative humidity in the control chamber, the humidity of the environment around the nano-aerosol in the control chamber can be changed, and the control range is (60% - 95%). The image plane detector performs real-time detection on the change of the scattered light of the nano-aerosol. [[ID=~31]]

[0061] Refer to Figure 1A device for detecting the hygroscopic growth of single aerosol nanoparticles based on a planar chip, as shown, includes: an image plane detector 1; an imaging tube lens 2; an air objective lens 3; a control chamber 4; a planar chip 5; a 750nm filter 6; a 750nm LED light source 7. The light beam emitted by the 750nm LED light source 7 is collimated and incident on the planar chip 5 through the 750nm filter 6, and exits on the planar chip as a large-angle hollow conical beam with a numerical aperture greater than 0.7, irradiating the nano-aerosol particles deposited on the planar chip. The pure scattering signal is collected by the air objective lens 3 with a numerical aperture of 0.6 and a magnification of 40, and passes through the imaging tube lens 2, and finally forms a dark-field image of the nano-aerosol particles on the image plane detector 1.

[0062] The top multi-layer dielectric film 9 is composed of SiO2 with a refractive index of 1.46 and a thickness of 100nm and the first SiN with a refractive index of 2.36 and a thickness of 88nm x alternately (a total of 10 pairs) by chemical vapor deposition on a 0.17mm thick cover glass, which is used to control the light flow. The scattering layer 10 is formed by doping 60nm titanium dioxide particles in SOG glue and then spin-coated on the bottom multi-layer dielectric film, with a thickness of 2μm, which is used to provide various propagation wave vectors. The bottom multi-layer dielectric film 11 is composed of the second SiN with a refractive index of 2.32 and a thickness of 73nm x and the third SiN with a refractive index of 1.92 and a thickness of 90nm x alternately (a total of 18 pairs) by chemical vapor deposition on a 0.17mm thick cover glass, and then on this basis, SiO2 with a refractive index of 1.46 and a thickness of 139nm and the first SiN with a refractive index of 2.36 and a thickness of 100nm are alternately deposited x alternately (a total of 11 pairs) to improve the light energy utilization efficiency. The top multi-layer dielectric film 9 and the scattering layer 10 are adhered together with a refractive index matching oil (refractive index of 1.51).

[0063] The 750nm LED light source emits a collimated 750nm light beam that is incident on the bottom multi-layer dielectric film 11 in the planar chip 5 through the 750nm filter 6.

[0064] Since the energy band of the underlying multi-layer dielectric film is fully transparent when the numerical aperture of the light beam is less than 0.2, the collimated 750-nm light beam is directly transmitted and hits the scattering layer 10 and is evenly scattered, generating wave vectors propagating in all directions and incident on the top multi-layer dielectric film 9. Under the energy band limitation of the top multi-layer dielectric film 9, the scattered 750-nm light beam screens the light beam. The light beam with a numerical aperture less than 0.7 in the scattered light is reflected by the top multi-layer dielectric film 9 back to the scattering layer 10, and under the limitation of the bottom multi-layer dielectric film 11, part of the scattered light will be incident on the top multi-layer dielectric film 9 again; while the light beam with a numerical aperture greater than 0.7 in the scattered light directly exits as a hollow conical light beam and irradiates the nano-aerosol deposited on the cover glass 8. The environmental humidity of the irradiated nano-aerosol is controlled by the control chamber 4. The control chamber 4 can stably change the relative humidity of the cavity environment (regulating the relative humidity range of 60%-95%) for the aerosol, thereby changing the physical and chemical properties of the aerosol and causing its optical properties to change. The change in the scattered light of the irradiated nano-aerosol is collected by the air objective lens 3. Since the collection numerical aperture of the air objective lens is less than the exit numerical aperture of the planar chip light beam, the air objective lens only collects the pure scattered light of the particles. The scattered light then passes through the imaging tube lens 2 and finally forms an image on the image plane detector 1, achieving a high-contrast dark-field imaging of the nano-aerosol and realizing a real-time monitoring imaging system for single nano-aerosol without labeling, non-invasive, and with high signal-to-noise ratio.

[0065] The collimation requirement for the 750-nm LED light beam is not high. Its exit numerical aperture only needs to be less than 0.2, and its incident collimation requirement is determined by the bottom multi-layer dielectric film 11.

[0066] The scattering layer 10 can scatter the incident collimated light beam into wave vectors propagating in all angles and incident on the top multi-layer dielectric film 9.

[0067] The top multi-layer dielectric film 9 can control the transmission angle of the light beam, so that the light beam exits at an angle greater than the numerical aperture of 0.7, illuminating the nano-aerosol particles deposited on the cover glass 8.

[0068] The imaging system composed of the air objective lens 3, the imaging tube lens 2, and the image plane detector 1 has a collection numerical aperture less than the exit numerical aperture of the planar chip light beam, enabling high-contrast, label-free dark-field imaging of the nano-aerosol.

[0069] The control chamber 4 can stably control the humidity change of the environment around the nano-aerosol. By changing the humidity inside the control chamber, the nano-aerosol undergoes hygroscopic growth, thereby changing its physical and chemical properties and thus causing its optical properties to change. The imaging system composed of the air objective lens 3, the imaging tube lens 2, and the image plane detector 1 monitors the optical changes of the nano-aerosol in real time.

[0070] The described device measures the hygroscopic growth of atmospheric aerosol particles with a diameter of 100 nm in real time by detecting the change in the scattered light intensity of nano-aerosol particles. Its time resolution is determined by the image plane detector 1. In this implementation, the exposure time of the image plane detector 1 is 100 ms, that is, the time resolution of this device can reach the level of 100 milliseconds.

[0071] The described device can design the energy bands of the top multi-layer dielectric film 9 and the bottom multi-layer dielectric film 11 by changing the thickness and refractive index of SiO2 and SiN x and select collection air objectives 3 with different numerical apertures, such as an air objective with a numerical aperture of 0.6 and a magnification of 40 times, an objective with a numerical aperture of 0.3 and a magnification of 10 times, etc., to realize imaging and detection systems with different fields of view and different resolutions.

[0072] Refer to Figure 2 As shown, it is a schematic diagram of the principle of a planar chip. The planar chip 5 consists of a cover glass 8 with a size of 22 mm * 22 mm and a thickness of 0.17 mm, a top multi-layer dielectric film 9 (composed of SiO2 with a refractive index of 1.46 and a thickness of 100 nm and a dielectric film with a refractive index of 2.36 and a thickness of 88 nm of the first SiN x alternating (a total of 10 pairs) by chemical vapor deposition on the 0.17-mm-thick cover glass), a scattering layer 10 (formed by doping 60-nm (particle size) titanium dioxide particles (the concentration of titanium dioxide particles is 100 mg / mL) in SOG glue and then spin-coating on the bottom multi-layer dielectric film, with a thickness of 2 μm), and a bottom multi-layer dielectric film 11 (composed of a second SiN x dielectric film with a refractive index of 2.32 and a thickness of 73 nm and a third SiN x dielectric film with a refractive index of 1.92 and a thickness of 90 nm alternating (a total of 18 pairs) by chemical vapor deposition on the 0.17-mm-thick cover glass, and then on this basis, alternately depositing a SiO2 dielectric film with a refractive index of 1.46 and a thickness of 139 nm and a first SiN x dielectric film with a refractive index of 2.36 and a thickness of 100 nm (a total of 11 pairs)). The top multi-layer dielectric film 9 and the scattering layer 10 are adhered together with a drop of Nikon refractive index matching oil (refractive index of 1.51). The cover glass 8 is used to carry the deposited nano-aerosol particle sample. The planar chip 5 is composed of a cover glass 8, a top multi-layer dielectric film 9, a scattering layer 10, and a bottom multi-layer dielectric film 11 stacked in sequence from top to bottom.

[0073] Among them, the top multi-layer dielectric film 9 screens the wave vector of the scattered excitation light, and the light beam with a scattered light numerical aperture greater than 0.7 can directly pass through the top multi-layer dielectric film 9, while the light beam with a scattered light numerical aperture less than 0.7 is blocked by the top multi-layer dielectric film 9.

[0074] Among them, the scattering layer scatters the incident light into propagating wave vectors at various angles and is incident on the top multi-layer dielectric film 9.

[0075] Among them, when the energy band of the bottom multi-layer dielectric film allows the numerical aperture of the incident light beam to be less than 0.2, the light beam directly passes through the bottom multi-layer dielectric film, reducing the requirement for the high collimation of the incident light beam. And it can reuse the light beam reflected back by the top multi-layer dielectric film 9.

[0076] Among them, the top multi-layer dielectric film 11 composed of alternating layers of a high refractive index Si3N4 and a low refractive index SiO2 allows the light beam with a higher collimation to pass through, and it can reuse the light beam reflected back by the top multi-layer dielectric film 9.

[0077] Among them, the refractive index parameter of SiO2 is the standard value of PECVD (Plasma Enhanced Chemical Vapor Deposition). Its process uses the standard silicon oxide process, with a silane gas flow rate of 150 sccm, a nitrous oxide gas flow rate of 710 sccm, and a nitrogen gas flow rate of 1000 sccm.

[0078] Among them, the first SiN x is a silicon-rich silicon nitride process, and the PECVD parameters are a silane gas flow rate of 310 sccm and an ammonia gas flow rate of 4 sccm.

[0079] Among them, the second SiN x is a silicon-rich silicon nitride process, and the PECVD parameters are a silane gas flow rate of 270 sccm and an ammonia gas flow rate of 4 sccm.

[0080] Among them, the third SiN x is a low-silicon silicon nitride process, and the PECVD parameters are a silane gas flow rate of 70 sccm and an ammonia gas flow rate of 4 sccm.

[0081] Refer to Figure 3 as shown, Figure 3 is the dark-field image of 100-nm sodium chloride aerosol particles in different humidity environments using this system. In the present invention, the preparation method of 100-nm sodium chloride aerosol particles is as follows: The 100-nm sodium chloride particles are first deposited on a cover glass using a self-made deposition system. A dark-field imaging with a high contrast (the contrast of 100-nm particles reaches 0.1) is achieved for the 100-nm sodium chloride aerosol particles, realizing a real-time monitoring imaging system for single-nanometer aerosol without labeling, non-invasive, and with a high signal-to-noise ratio.

[0082] Among them, the self-made deposition system includes an atomizer responsible for generating particles, a drying tube for drying the particles, a differential mobility analyzer (DMA) for screening nanoparticles, and a deposition chamber for depositing onto a cover glass. The deposition chamber is a conical cavity, allowing the screened particles to enter from the bottom of the conical cavity and finally exit from the top of the conical cavity, hitting the particles onto the cover glass.

[0083] Among them, the ambient humidity around 100nm sodium chloride particles can be controlled by the control chamber 4, and the humidity range of the control chamber is 60%-90%.

[0084] Among them, at fixed humidities, such as 60%, 74%, 76%, 90%, the nano-aerosol is imaged, and the scattering intensity of aerosol particles at the corresponding humidity is obtained on the image plane detector 1. The exposure time of the image plane detector 1 is 100ms.

[0085] Among them, it can be clearly seen that when the relative humidity changes from 74% to 76%, the image intensity detected on the image plane increases significantly, proving that at this humidity, the sodium chloride particles have undergone the phenomenon of hygroscopic deliquescence.

[0086] Refer to Figure 4 as shown Figure 4 It is the growth process of the integral scattering intensity (black dots, right axis) of 100nm sodium chloride aerosol particles in an environment with increasing relative humidity using this system, and the growth factor curve (solid line, left axis) calculated by referring to the existing extended inorganic aerosol model (http: / / www.aim.env.uea.ac.uk / aim / aim.php) (setting 100nm sodium chloride particles).

[0087] Among them, the integration of the scattering intensity is obtained by integrating a rectangular integration region of 13*13 pixel points centered on the highest scattering intensity in the image plane (refer to the rectangular frame region in Figure 3 ).

[0088] Among them, the growth of the integral scattering intensity measured by this system accurately measures the deliquescence point position of sodium chloride. The scattering integral intensity curve and the calculated growth factor curve coincide, and it can directly reflect the hygroscopic growth process of 100nm single-particle sodium chloride from the imaging.

[0089] Among them, after the relative humidity reaches 76% and the sodium chloride nanoparticles deliquesce, this device can still detect the process of sodium chloride particles continuously absorbing water from the environment as the humidity increases, proving that even the moisture absorption without a deliquescence point can be detected in real time.

[0090] The parts not elaborated in the present invention belong to the well-known technologies in the art. The above-described embodiments are only descriptions of the preferred embodiments of the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Without departing from the spirit of the design of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A device for detecting the hygroscopic growth of a single aerosol nanoparticle by a dark-field microscope based on a planar chip, characterized in that: The device includes: an image plane detector (1), an imaging tube lens (2), an air objective lens (3), a control chamber (4), a planar chip (5), a 750 nm filter (6), and a 750 nm LED light source (7); wherein the planar chip (5) is composed of a cover glass (8), a top multilayer dielectric film (9), a scattering layer (10), and a bottom multilayer dielectric film (11) stacked in sequence from top to bottom; Among them, the 750 nm LED light source (7) emits a collimated 750 nm light beam that is incident on the bottom multilayer dielectric film (11) in the planar chip (5) through the 750 nm filter (6); since the energy band of the bottom multilayer dielectric film is completely transmissive when the numerical aperture of the light beam is less than 0.2, the collimated 750 nm light beam is directly transmitted and hits the scattering layer (10) and is uniformly scattered, generating propagation wave vectors at various angles and incident on the top multilayer dielectric film (9); under the energy band limitation of the top multilayer dielectric film (9), the scattered 750 nm light beam is screened; the light beam with a numerical aperture less than 0.7 in the scattered light is reflected back to the scattering layer (10) by the top multilayer dielectric film (9), and under the limitation of the bottom multilayer dielectric film (11), part of the scattered light beam is incident on the top multilayer dielectric film (9) again; while the light beam with a numerical aperture greater than 0.7 in the scattered light directly exits as a hollow conical light beam and irradiates the nano-aerosol deposited on the cover glass (8); the ambient humidity of the irradiated nano-aerosol is controlled by the control chamber (4); the control chamber (4) can change the relative humidity of the chamber environment, thereby changing the physical and chemical properties of the aerosol and causing changes in its optical properties; the change in the scattered light of the irradiated nano-aerosol is collected by the air objective lens (3), and since the collection numerical aperture of the air objective lens is less than the exit numerical aperture of the planar chip light beam, the air objective lens only collects the pure scattered light of the particles, and the scattered light passes through the imaging tube lens (2) and finally forms an image on the image plane detector (1), forming a dark-field image of the nano-aerosol.

2. The device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip according to claim 1, characterized in that, The collimation requirement for the 750 nm LED light beam is that the numerical aperture of the light beam is less than 0.2, and its incident collimation requirement is determined by the bottom multilayer dielectric film (11).

3. The device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip according to claim 1, wherein The scattering layer (10) can scatter the incident collimated light beam into propagation wave vectors at various angles and incident on the top multilayer dielectric film (9).

4. A device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip according to claim 1, characterized in that, The top multilayer dielectric film (9) can control the transmission angle of the light beam, allowing the light beam with a numerical aperture greater than 0.7 to exit and illuminate the nano-aerosol particles deposited on the cover glass (8).

5. The hygroscopic growth device for detecting a single aerosol nanoparticle based on a planar chip according to claim 1, wherein The imaging system composed of the air objective lens (3), the imaging tube lens (2), and the image plane detector (1) has a collection numerical aperture less than the exit numerical aperture of the planar chip light beam.

6. A device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip by dark-field microscopy according to claim 1, characterized in that The control chamber (4) can stably control the humidity change in the surrounding environment of the nano-aerosol. By changing the humidity inside the control chamber, the nano-aerosol undergoes hygroscopic growth, thereby changing its physical and chemical properties, and thus causing changes in its optical properties. The imaging system composed of an air objective lens (3), an imaging tube lens (2), and an image plane detector (1) monitors the optical changes of the nano-aerosol in real time.

7. A device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip in a dark-field microscope according to claim 1, characterized in that, The described device measures the hygroscopic growth of 100-nm atmospheric aerosol particles in real time by detecting the change in the scattered light intensity of the nano-aerosol particles, and the time resolution of the image plane detector (1) reaches the millisecond level.

8. The device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip by dark-field microscopy according to claim 1, wherein The described device can achieve imaging and detection systems with different fields of view and different resolutions by designing the energy bands of the top multi-layer dielectric film (9) and the bottom multi-layer dielectric film (11) and selecting collection air objective lenses (3) with different numerical apertures.

9. The device for detecting the hygroscopic growth of a single aerosol nanoparticle based on a planar chip according to claim 1, wherein The top multi-layer dielectric film (9) is formed by alternately chemically vapor depositing a SiO2 dielectric film with a refractive index of 1.45 - 1.5 and a thickness of 95 - 100 nm and a first SiNx dielectric film with a refractive index of 2.36 - 2.5 and a thickness of 80 - 88 nm on a cover glass with a thickness of 0.17 - 0.2 mm.

10. A device for detecting the hygroscopic growth of a single aerosol nanoparticle by a dark-field microscope based on a planar chip according to claim 1, characterized in that, The bottom multi-layer dielectric film (11) is formed by alternately chemically vapor depositing a second SiNx dielectric film with a refractive index of 2.2 - 2.32 and a thickness of 73 - 75 nm and a third SiNx dielectric film with a refractive index of 1.9 - 2.0 and a thickness of 90 - 95 nm on a cover glass with a thickness of 0.17 - 0.2 mm. Then, on this basis, a SiO2 dielectric film with a refractive index of 1.45 - 1.5 and a thickness of 139 - 150 nm and a first SiNx dielectric film with a refractive index of 2.36 - 2.5 and a thickness of 100 - 110 nm are alternately deposited. The scattering layer (10) is formed by doping TiO2 particles with a particle size of 60 - 80 nm in SOG glue and then spin-coating it on the bottom multi-layer dielectric film (11), with a thickness of 2 - 3 µm.

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