CN112345412A - Nano bubble diffusion coefficient in-situ measurement method - Google Patents
Nano bubble diffusion coefficient in-situ measurement method Download PDFInfo
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Abstract
The invention belongs to the technical field of micro-nano particle measurement, and relates to an in-situ measurement method for a nano bubble diffusion coefficient. The method is used for accurately and visually measuring the particle size and the nano-bubble diffusion coefficient of the nano-bubbles in the water containing the nano-bubbles. The diameter of the nano-bubbles is directly measured by using the magnification factor of a transmission electron microscope up to hundreds of nanometers, and the motion state of the nano-bubbles with the corresponding particle size can be shot in real time under a liquid phase, so that the diffusion coefficient under the particle size is obtained. The method can effectively and visually measure the particle size of the nanobubbles, and simultaneously calculate the diffusion coefficient of the nanobubbles with corresponding particle size, thereby making up for the defect that the particle size and the diffusion coefficient of the nanobubbles cannot be synchronously obtained by traditional measurement of the nanobubbles by using the DLS principle.
Description
Technical Field
The invention belongs to the technical field of micro-nano particle measurement, and relates to an in-situ measurement method for a nano bubble diffusion coefficient.
Background
In recent years, the nano bubbles have wide application in the fields of aquaculture, soilless culture, sewage treatment, fruit and vegetable cleaning, beauty and skin care and the like due to the characteristics of small particle size, large specific surface area, slow rising speed and long survival time of the nano bubbles: the nano bubbles can survive in water for a long time, so that the dissolved oxygen in the water can be kept sufficient for a long time, and the activity and the yield of aquatic products are greatly improved; the water containing the nano bubbles irrigates crops, so that the population and activity of microorganisms in rhizosphere soil can be increased, and the capability of absorbing water and nutrients of a root system is enhanced; meanwhile, the nano bubbles can enhance the activity of microorganisms in water, accelerate the degradation process of the microorganisms to pollutants in water and realize water purification. The nano bubbles can be widely applied without the characteristics of strong diffusion capability and small particle size in water, so that the determination of the diffusion coefficient and the particle size of the nano bubbles in water is beneficial to the application development of the nano bubbles in the future.
At present, the basic principle of the measuring device for the particle size and the diffusion coefficient of the nano bubbles is mainly Dynamic Light Scattering (DLS). The device using DLS as the principle mainly utilizes the technology to capture the Brownian motion track characteristic of the nano bubbles in water, obtains the diffusion coefficient of the nano bubbles through software calculation, and then calculates the particle size of the nano bubbles by combining the diffusion coefficient with the Einstein equation. However, the measurement device based on the DLS principle has the following problems: the nano bubbles in the captured dynamic video cannot be directly marked by the particle size, and the diffusion coefficient and the particle size of the nano bubbles can be measured only in a stepping mode and cannot be measured simultaneously.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and develop an in-situ measurement method for the diffusion coefficient of the nanobubbles, which is used for accurately and visually measuring the particle size and the diffusion coefficient of the nanobubbles in the nanobubble-containing water. The method utilizes a transmission electron microscope to amplify thousands of or even tens of thousands of times of amplification factor, directly measures the diameter of the nano bubbles, and can shoot the motion state of the nano bubbles with corresponding grain diameter in real time under liquid phase to obtain the diffusion coefficient under the grain diameter. The method can effectively and visually measure the particle size of the nanobubbles, and simultaneously calculate the diffusion coefficient of the nanobubbles with corresponding particle size, thereby making up for the defect that the particle size and the diffusion coefficient of the nanobubbles cannot be synchronously obtained by traditional measurement of the nanobubbles by using the DLS principle.
The technical scheme of the invention is as follows:
the method utilizes the characteristic that a transmission electron microscope can amplify nano bubbles up to hundreds of nanometers, measures the diameters of the nano bubbles in situ, can observe the motion state of the nano bubbles with corresponding particle sizes in real time in a liquid phase, records the diffusion video of the Brownian motion of the nano bubbles, and obtains the diffusion coefficient under the particle sizes by superposing and calculating the motion tracks of the corresponding bubbles.
The method comprises the following specific steps:
the first step is as follows: acquiring a nano bubble motion video and an image;
pushing the solution containing the nano bubbles into a sample cell of a liquid rod equipped in a transmission electron microscope by using a pressure difference device under the action of pressure difference, vacuumizing the sample cell, putting the sample cell into the transmission electron microscope for observation, and shooting a motion video of the nano bubbles after finding the moving nano bubbles;
the second step is that: video and image processing and data processing;
opening motion video data to carry out a scale, measuring the diameter of a moving bubble, simultaneously playing a video frame by frame, measuring the moving distance between each frame of the bubble by a distance measuring tool, wherein the time interval of each frame is not less than 0.16s, and recording the moving distance of each frame;
the third step: calculating the diffusion coefficient of the nano bubbles;
and substituting the moving distance and the time interval between every two frames obtained in the second step into a diffusion coefficient equation, or substituting the accumulated moving distance between every two adjacent frames and the accumulated moving distance corresponding to the time interval into the diffusion coefficient equation, and calculating the diffusion coefficient of the nano bubbles:
d is the diffusion coefficient of the nano-bubbles in the calculation time interval, X is the total moving distance of the nano-bubbles in the calculation time interval, and t is the time interval adopted by the calculation.
Further, in the first step, the nano bubble motion video and the image are obtained, the bubble existence area is searched under low magnification, the magnification is increased to high magnification, and the bubble motion video is recorded, wherein the high magnification is not lower than 6300 times.
In order to obtain a more accurate diffusion coefficient of the nano-bubbles, a video recorded by a transmission electron microscope for a long time can be used, after the distance between each frame is measured, the distance between each frame is accumulated according to the moving distance between adjacent frames and then is accumulated with the corresponding time interval to be brought into a diffusion coefficient equation, a plurality of groups of diffusion coefficients are obtained through calculation, the obtained diffusion coefficients are averaged, and a more accurate diffusion coefficient value of the nano-bubbles is obtained.
The invention has the beneficial effects that:
according to the technical scheme, the transmission electron microscope is used for measuring the particle size of the nano bubbles and calculating the diffusion coefficient, so that the real particle size and the real diffusion coefficient of the nano bubbles in the solution can be accurately obtained.
The transmission electron microscope is used for measuring the particle size of the nano bubbles and calculating the diffusion coefficient, so that the defect that the existing device using DLS as a measurement principle cannot synchronously measure the particle size and the diffusion coefficient and can only bring the Stokes-Einstein equation into the diffusion coefficient to calculate the particle size is overcome. The motion state of the nano bubbles in a liquid environment is directly observed under high magnification by using a transmission electron microscope, the particle size of the nano bubbles in a video is measured by using data processing software, the motion distance of the nano bubbles is measured frame by frame and is brought into a diffusion coefficient equation, and the diffusion coefficient of the nano bubbles is effectively and accurately calculated. The calculation result shows that the moving distance of the nano bubbles with the particle size of about 210nm between each frame is measured, the distances obtained from each 30 frames are accumulated and added, and the average value of the diffusion coefficients of the nano bubbles with the particle size of about 210nm in water is 1.1645 multiplied by 10 by substituting the equation-12m2And/s, substituting the diffusion coefficient value into a Stokes-Einstein equation to calculate that the radius of the bubble is 209.66nm, and comparing the particle size of the bubble, the scheme provided by the invention has high feasibility.
Drawings
FIG. 1 is a flow chart of an in situ measurement method of nanobubble diffusion coefficient.
Fig. 2 is a distance map between each frame.
Fig. 3 is a graph of the distance accumulation results for every adjacent 4 s.
Fig. 4 is a graph of sets of diffusion coefficients calculated for 4s (25 frames) in time intervals.
Detailed Description
The following detailed description of the invention refers to the accompanying drawings. The examples are intended to further illustrate the invention, but not to limit it.
Examples
The method for calculating the particle size and the diffusion coefficient of the nano bubbles comprises the following specific steps:
the first step is as follows: acquiring a nano bubble motion video and an image;
pushing the solution containing the nano bubbles into a sample cell of a liquid rod equipped in a transmission electron microscope by using a pressure difference device under the action of pressure difference, vacuumizing the sample cell, placing the sample cell into the transmission electron microscope for observation, finding the moving nano bubbles under a low-power lens, and then shooting the moving video of the nano bubbles by using a high-power lens; the high multiple is not less than 6300 times.
The second step is that: video and image processing and data processing;
this operation is opened in the GATAN Digital Micrograph software and requires the installation of a corresponding video license to open the video data. Firstly, opening stored video data by in-situ imaging in GATAN Digital Micrograph, firstly clicking a right mouse button on a video window, selecting a layout option, and clicking an add scalebar to add a video ruler; clicking a right button of the mouse, selecting a line with length label to measure the diameter of the nano bubble, wherein the particle size of the nano bubble in the embodiment is 210 nm; clicking a right mouse button on a video window interface, selecting a mask spot to mark a bubble center point, performing point marking on the bubble center of each frame through a frame-by-frame selection function of an in-site player, measuring the distance of the bubble center point between the frames by using a line with length label function, and recording the corresponding frame number and distance at excel at any time, wherein the time length of recording a bubble motion video in the example is 16s (100 frames), and the distance between the frames is shown in figure 2;
the third step: calculating the diffusion coefficient of the nano bubbles;
superposing the moving distance between each frame obtained in the previous step according to the interval of 4s (25 frames) of 0-4s, 1-5s and 2-6s, and calculating to obtain 13 groups of diffusion coefficients and an average value of the nano bubbles by substituting the accumulated distance map into a diffusion coefficient equation with the corresponding time interval of 4s, wherein the accumulated distance map is shown in figure 3:
comparative example
In order to quantify the accuracy of the in-situ measurement method of the nano-bubble diffusion coefficient, the nano-bubble particle size and the diffusion coefficient obtained by measurement and calculation through a transmission electron microscope are compared with the particle size obtained by calculation through substituting the calculated nano-bubble diffusion coefficient into a Stokes-Einstein equation. Comparative examples are nanobubbles with a particle size of 210 nm:
the diffusion coefficient calculated in the above example is:
the diffusion coefficient is substituted into the stokes-einstein equation:
wherein k is Boltzmann constant, and is 1.38065 × 10-23J/K; mu is the viscosity of water, and 0.008949 pas is taken; t is 298.15K at absolute temperature;
the comparison shows that the diameter of the nano-bubble measured based on the transmission electron microscope is 210nm, the calculated diffusion coefficient is substituted into the Stokes-Einstein equation to obtain the diameter of 209.66nm, and the result is basically consistent.
Claims (4)
1. An in-situ measurement method for a nano-bubble diffusion coefficient is characterized by comprising the following steps:
the first step is as follows: acquiring a nano bubble motion video and an image;
pushing the solution containing the nano bubbles into a sample cell of a liquid rod equipped in a transmission electron microscope by using a pressure difference device under the action of pressure difference, vacuumizing the sample cell, putting the sample cell into the transmission electron microscope for observation, and shooting a motion video of the nano bubbles after finding the moving nano bubbles;
the second step is that: video and image processing and data processing;
opening motion video data to carry out a scale, measuring the diameter of a moving bubble, simultaneously playing a video frame by frame, measuring the moving distance between each frame of the bubble by a distance measuring tool, wherein the time interval of each frame is not less than 0.16s, and recording the moving distance of each frame;
the third step: calculating the diffusion coefficient of the nano bubbles;
and substituting the moving distance and the time interval between every two frames obtained in the second step into a diffusion coefficient equation, or substituting the accumulated moving distance between every two adjacent frames and the accumulated moving distance corresponding to the time interval into the diffusion coefficient equation, and calculating the diffusion coefficient of the nano bubbles:
d is the diffusion coefficient of the nano-bubbles in the calculation time interval, X is the total moving distance of the nano-bubbles in the calculation time interval, and t is the time interval adopted by the calculation.
2. The in-situ measurement method for the diffusion coefficient of the nanobubbles according to claim 1, characterized in that the first step of obtaining the nanobubble motion video and image is to search the area where the bubbles exist under low magnification, then to magnify the magnification to high magnification, and record the nanobubble motion video, wherein the high magnification is not less than 6300 times.
3. The method of claim 1, wherein the second step of video and image processing and data processing uses data processing software capable of opening the dm4 format.
4. The in-situ measurement method for the diffusion coefficient of the nanobubbles according to claim 1, characterized in that the third step is to calculate the diffusion coefficient of the nanobubbles, accumulate the moving distances between the adjacent frames and the corresponding time intervals to bring the accumulated moving distances into a diffusion coefficient equation, calculate to obtain a plurality of groups of diffusion coefficients, and calculate the average value of the obtained plurality of groups of diffusion coefficients to obtain a more accurate value of the diffusion coefficient of the nanobubbles.
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| CN116563342A (en) * | 2023-05-18 | 2023-08-08 | 广东顺德西安交通大学研究院 | Bubble tracking method and device based on image recognition |
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Application publication date: 20210209 |