JP6275001B2 - Aerosol collector - Google Patents

Description

  The present invention relates to an aerosol collecting device including a fine particle charging device for charging nanoparticles and a particle deposition device for depositing charged nanoparticles on a collection film by electrostatic deposition.

  Due to rapid progress in semiconductors, electronic devices, material science, and nanotechnology technologies, research and development on nanostructures that integrate nanoparticles as constituent elements is progressing. On the other hand, there is an increasing social interest regarding the behavior of fine particles in the atmospheric environment, represented by PM2.5. In order to analyze the chemical composition and structure of these particles, a chemical analyzer such as an electron microscope or gas chromatography is used. In order to perform such an analysis, development of an efficient method for collecting or depositing a fine particle substance on a substrate is required.

  Air filters are most widely used for collecting such fine particles. For example, in Non-Patent Document 1, chemical components are analyzed using high performance liquid chromatography by collecting aerosol in the atmosphere for a long time and extracting it with a liquid.

  Electrostatic collection of particles is widely used for collecting aerosols having a particle size of submicron or less. For example, Patent Document 1 proposes a method for efficiently collecting conductive ultrafine particles in a carrier gas using an electrostatic collection device.

  For the purpose of chemical analysis and structural analysis, detecting particles in a shorter time and with higher sensitivity is a particularly useful technique for the time variation of atmospheric aerosols and the identification of dust sources in clean rooms. .

  In addition, it is known that the characteristics of the aerosol vary greatly with respect to the physical size of the particles (for example, Non-Patent Document 2). For example, in the electrostatic classifier described in Non-Patent Document 3, it is possible to selectively take out only particles of a specific size outside the apparatus using the difference in electric mobility.

  By depositing the aerosol locally on the substrate using the electrostatic focusing effect, high concentration aerosol particles can be obtained locally, that is, an aerosol concentration effect can be expected. Such an electrostatic convergence effect of aerosol is already described in Non-Patent Document 4.

  In addition, one of the aerosol deposition techniques currently being investigated is an aerosol deposition technique using a lithography technique. For example, a deposition technique for forming a deposition pattern of nanoparticles is cited as an application example (Patent Literature). 2). Patent Document 3 describes a method of depositing particles in a micron range on a dielectric substrate using an alternating electric field.

  Another attempt to deposit aerosol particles on a substrate is to deposit an aerosol using inertial forces. For example, Non-Patent Document 5 proposes a method of forming a pattern of about 50 to 1.5 microns using an aerosol deposition method.

  In a normal electrostatic collection device, for example, as described in Non-Patent Document 6, a substrate is placed on an electrode.

JP 7-47299 A US Patent Application Publication No. 2006 / 0093749A1 US Pat. No. 6,923,979

Sato, Satoshi Tanaka, Ai Lee, Shiho Ogawa, Shiro Hatakeyama (2007) Composition and seasonal variation of organic aerosols at Cape Hedo, Okinawa: Polycyclic aromatic hydrocarbons observed from 2005 to 2006. Geoscience 41: 145 -153. Whitby, K.T (1978) The physical characteristics of sulfur aerosols. Atmospheric Environment 12: 135-159. Chen, D.-R., Pui, DYH, Hummes, D., Fissan, H., Quant, FR and Sem GJ (1998) Design and evaluation of nanometer aerosol Differential Mobility Analyzer (Nano-DMA). Journal of Aerosol Science 29: 197-509. Kim, H., Kim, J., Yang, H., Suh, J., Kim, T., Han, B., Kim, S., Kim, D., Pikhitsa, PV, and Choi, M. ( 2006) Parallel patterning of nanoparticles via electrodynamic focusing of charged aerosols.Nature Nanotechnology 1: 117-121. May, K.R. (1945) The Cascade Impactor: An Instrument for Sampling Coarse Aerosols.Journal of Scientific Instruments 22: 182 Nanometer Aerosol Sampler Model 3089 spec sheet [on line] TSI Incorporated, [Search June 17, 2014], Internet <URL: http://www.tsi.com/uploadedFiles/_Site_Root/Products/Literature/Spec_Sheets/3089_Nanometer_Aerosol_Sampler % 20A4-5001416_WEB.pdf>

  In the known techniques described in the patent documents and non-patent documents as described above, the above-described air filter and electrostatic collection device generally collects aerosol in a large area, and therefore requires a lot of time for sampling. Is.

  In the electrostatic classifier, the particle concentration is remarkably reduced by performing the classification operation, and much more time is required to analyze the chemical components of the particles.

  In addition, in the method of depositing aerosol using the inertial force described above, generally, if the particle size is reduced, the inertial force is reduced, and the particle trajectory is widened by Brownian motion, so that it is difficult to directly form a fine pattern. . In order to overcome this, a large vacuum device or a fine nozzle is required as a device.

  As mentioned above, it is known that aerosol electrostatic deposition is useful for particle collection and subsequent chemical component analysis, but it takes a lot of sampling time to perform analysis with sufficient sensitivity. This is a problem, and a technique for solving this problem is demanded.

  Accordingly, an object of the present invention is to provide an apparatus for locally depositing aerosol particles in order to obtain sufficient analysis sensitivity in a shorter time.

The invention described in the first claim of the present application is described with the reference numerals used in the examples, and the fine particle charging device 2 for charging the nanoparticles, and the charged nanoparticles on the collection film 11 by electrostatic deposition. In an aerosol collecting device 1 provided with a particle deposition device 3 for deposition,
The particle deposition apparatus 3 includes a container 4 provided with a particle inflow portion 5 and a particle discharge portion 6, a particle inflow nozzle 7 provided in the particle inflow portion 5 of the container 4, and particles flowing in from the inflow nozzle 7. A deposition holder 8 for deposition,
The accumulation holder 8 is provided with an electrode 10 inside a resin-made collection container 9, and a collection film 11 is provided on the electrode 10. The accumulation holder 8 is provided at the upper end with the inflow nozzle 7. Covered with a metal cover 12 provided with through-holes 13 that allow the charged nanoparticles to be introduced through;
Further, a metallic mesh member 14 is provided on the collecting film 11 in addition to the above, and the collecting film 11 is a film made of a transparent polymer, and the mesh member 14 is a mesh made of SUS. It is an aerosol collecting device 1 characterized by being.

  According to the invention described in claim 1 of the present application, since the metal mesh member is provided on the collection film so as to overlap, the aerosol particles are electrostatically applied locally as shown in Examples below. It is possible to deposit, and there is an effect that a sufficient analysis sensitivity can be obtained in a shorter time. In this way, high concentration aerosol particles can be obtained locally by depositing the aerosol locally on the substrate using the electrostatic convergence effect. Thus, according to the present invention, an aerosol concentration effect can be expected.

Furthermore , since the collection film is a film made of a transparent polymer and the mesh member is a mesh made of SUS, it becomes possible to form a local deposition pattern of particles on a transparent substrate, for chemical analysis of fine particles. It can be applied as a concentration method. For example, it becomes possible to irradiate fine particles with probe light having a diameter of several microns and obtain information on chemical components of the particles from the scattered light and transmitted light.

It is a schematic diagram which shows the aerosol collection apparatus concerning the Example of this invention. 1 is an external perspective view showing a particle deposition apparatus according to an embodiment of the present invention. FIG. 6 is a prediction diagram illustrating selective deposition of aerosol using an electrostatic convergence effect according to an embodiment of the present invention. It is a figure which concerns on the Example of this invention and shows the electric field calculation result around a deposition board | substrate. It is a figure which concerns on the Example of this invention and shows evaluation of the transport state of the particle | grains by a dimensionless number. It is a figure which concerns on the Example of this invention and shows the mapping of the conditions in which the deposition by a dimensionless number was recognized. It is a figure which concerns on the Example of this invention and shows the random deposition seen on conditions with a large Stokes number. It is a figure which concerns on the Example of this invention and shows the deposition pattern of the obtained particle | grains. It is a figure which shows the enlarged view of a deposition pattern concerning the Example of this invention. It is a figure which concerns on the Example of this invention and shows the measurement result of collection efficiency. 1 is a conceptual diagram of chemical analysis by selective deposition of particles on a transparent film according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

  As shown in FIG. 1, the aerosol collecting device 1 of this example includes a fine particle charging device (SMAC) 2 for charging nanoparticles and particle deposition for depositing charged nanoparticles on a collecting film 11 by electrostatic deposition. And a device 3. In the fine particle charging device (SMAC), particles can be charged in a multivalent manner.

  As shown in FIG. 2, the particle deposition apparatus 3 includes a container 4 provided with a particle inflow part 5 and a particle discharge part 6, a particle inflow nozzle 7 provided in the particle inflow part 5 of the container 4, and the inflow nozzle. And a deposition holder 8 for depositing the particles flowing in from 7.

  The accumulation holder 8 is provided with an electrode 10 inside a resin-made collection container 9, and a collection film 11 is provided on the electrode 10. The accumulation holder 8 is provided at the upper end with the inflow nozzle 7. It is covered with a metal cover 12 provided with a through-hole 13 that allows passage of charged nanoparticles introduced more.

  In the deposition holder 8, the charged particles are introduced from the inflow nozzle 7 by electrostatic force by a high voltage application device and collected on the electrode 10 separated by several mm to several tens mm.

  Furthermore, in the present invention, a metal mesh member 14 is provided on the collection film 11 in an overlapping manner.

  In this example, the deposition holder 8 is made of a resin (for example, Teflon (registered trademark) rod (cylindrical member) with an electrode 10 installed therein, and a PEN film (collecting film 11) that is a transparent polymer on the electrode 10. Are provided, and a SUS mesh (mesh member 14) is further stacked thereon, which is covered with a SUS cover (metal cover 12).

  As described above, the effect obtained when the collection film 11 is provided over the electrode 10 and a SUS mesh is further provided thereon is shown in FIG. When the electric field in the vicinity of the electrode was calculated by numerical simulation, the result shown in FIG. 4 was obtained.

  That is, in FIG. 4, from the left, only the film, the SUS cover added thereto, and the SUS mesh with a fiber distance of 97 microns added thereto are shown. Looking at the leftmost figure (film only), it can be seen that the electric field spreads not only from the upper nozzle to the electrodes, but also around. When this is covered with a SUS cover, the electric field concentrates in the electrode direction as shown in the center figure. Furthermore, if the SUS mesh is overlaid on this in order to form a local deposition pattern, the electric field becomes weaker as shown in the right figure. Therefore, in order to transport particles to the vicinity of the substrate where the electric field is formed, it is considered that the particles introduced from the nozzle need to be transported by inertia up to a certain distance.

  Therefore, the particle transport state was evaluated by two dimensionless numbers, the Stokes number, which is a measure of the inertia of the particle, and the Coulomb parameter representing the transport of particles in the fluid by the electric field (FIG. 5). From FIG. 5, the Stokes number is a dimensionless number representing the inertial force acting on the particle, and is proportional to the square of the particle diameter and the flow velocity. On the other hand, the Coulomb parameter is a dimensionless number representing the transport of particles by the electric field, and is found to be inversely proportional to the flow velocity and the particle size. First, a deposition experiment was performed by changing these two parameters, and the conditions under which a particle deposition pattern was formed were determined.

  The vertical axis is the Coulomb parameter Kc, and the horizontal axis is the Stokes number. In the figure, “x” is a condition in which local deposition of particles was not observed, and “●” is a condition in which local deposition of particles was observed. From the previous equation (FIG. 5), the dependence of the particle size and the flow velocity is reversed between Kc and the Stokes number, so that the Kc decreases as the Stokes number is increased. As shown in FIG. 6, local deposition was not observed under most conditions. For example, in these conditions where the Stokes number was large, the deposition itself was performed, but since the inertia is almost dominant, A pattern could not be formed, and particles were randomly deposited as shown in the SEM image of FIG. On the other hand, deposition was recognized only in two conditions when the Coulomb parameter was 1.5 or more and the distance between the nozzle and the substrate was 5 mm, and there was a certain distance.

  FIG. 8 is an SEM image of PSL particles having a particle diameter of 100 nm in which local deposition was observed among the above conditions. It can be seen that the black portion of the background is the film surface, and the white dots in the figure are structures composed of nanoparticles, respectively, and structures that are arranged at equal intervals are formed as shown in FIG. When the width of the SUS mesh is superimposed on this, as shown in FIG. 9, a particle deposition pattern converged to about 7 μm square is formed at the center of the opening, and about 7% of the SUS mesh pitch width of 97 μm. It turns out that it is shrinking. When this is converted into an area ratio, it is concentrated about 192 times.

  However, as described above, since the electric field is also lowered by the covering of the SUS mesh, there is a concern that the particle collection efficiency is also lowered. Therefore, as shown in FIG. 1, the particle concentration is measured by the condensation nucleus counter CPC at the outlet, and the percentage of the introduced particles is collected by turning on / off the high voltage power source. did.

  FIG. 10 is a plot of the collection efficiency obtained versus the particle size. First, in the result of plotting the collection efficiency when only the film is placed on the deposition holder 8 with respect to the particle diameter, the SMAC (particulate charging device 2) is not used, that is, in the case of monovalently charged particles, 100 nm or less. Is collected almost 100%, but it can be seen that the collection efficiency is reduced due to the decrease in the electric mobility.

  Next, it is understood that when the SMAC is operated, the particles are charged in a multivalent manner, so that the particle collection efficiency is increased. Next, when the film and the SUS cover are placed on the deposition holder 8, the electric field concentrates in the direction of the film, as can be seen from the electric field calculation result in the center of FIG. Therefore, the particle collection efficiency was lowered.

  Finally, when a SUS mesh was installed on this, the electric field was further restricted and the collection efficiency was lowered. At this time, focusing on the coarse particle side, the particles are collected to the same extent as in the case without the mesh, and at this time, the particles are probably collected by inertia rather than the electric field. This can also be inferred from the fact that the collection efficiency is lower as the particle size is smaller. In addition, when the SMAC was activated to charge the particles multivalently, the overall collection efficiency was increased. Finally, the collection efficiency of 100 nm multivalent charged particles was 0.1 (10%). When this was multiplied by the convergence rate obtained from the SEM image, it was found that 10% × 192 = 19.2 times the concentration of the supplied particles. In other words, by installing the SUS cover and the SUS mesh, the particle collection efficiency is reduced to about 10%. However, since the particles can be deposited locally on the surface, the total is about 20 times larger. It was confirmed that it was concentrated.

  Another embodiment of the present invention will be described. In this example, a method of locally depositing nanoparticles at a specific position is applied as a concentration method for chemical analysis of fine particles. As a result, for example, as shown in FIG. 11, it is considered possible to irradiate fine particles with probe light having a diameter of several microns and obtain information on chemical components of the particles from the scattered light and transmitted light. Here, in order to use the transmitted light, it is effective to form a local deposition pattern of particles on a transparent substrate.

  The aerosol collection device of the present invention can be suitably used for structural analysis and chemical analysis because the aerosol can be locally electrostatically deposited and the particles can be concentrated and collected.

DESCRIPTION OF SYMBOLS 1 Aerosol collection apparatus 2 Fine particle charging apparatus 3 Particle deposition apparatus 4 Container 5 Particle inflow part 6 Particle discharge part 7 Inflow nozzle 8 Deposition holder 9 Collection container 10 Electrode 11 Collection film 12 Metal cover 13 Through-hole 14 Mesh member

Claims (1)

In an aerosol collecting device 1 comprising a fine particle charging device 2 for charging nanoparticles and a particle deposition device 3 for depositing charged nanoparticles on a collecting film 11 by electrostatic deposition,
The particle deposition apparatus 3 includes a container 4 provided with a particle inflow part 5 and a particle discharge part 6, a particle inflow nozzle 7 provided in the particle inflow part 5 of the container 4, and particles flowing in from the inflow nozzle 7. A deposition holder 8 for deposition,
The deposition holder 8 is configured by installing an electrode 10 inside a resin-made collection container 9 and stacking a collection film 11 on the electrode.
The deposition holder 8 is configured to be covered with a metal cover 12 provided with a through hole 13 that allows the charged nanoparticles introduced from the inflow nozzle 7 to pass through at the upper end,
Further, a metallic mesh member 14 is provided on the collecting film 11 in addition to the above, and the collecting film 11 is a film made of a transparent polymer, and the mesh member 14 is a mesh made of SUS. An aerosol collecting device 1, characterized in that there is.

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