A method for preparing double samples based on transmission electron microscope support film

Abstract

The present invention proposes a method for preparing double samples based on a transmission electron microscope support film, wherein a matching sample preparation table and a grid support film are used to prepare double samples; when the matching sample preparation table is used to prepare double samples of a transmission electron microscope grid support film, the grid support film is placed with the front side facing upward in a base groove, and a pressing plate cooperates with the base groove through a positioning column so that the bottom of the pressing plate covers the grid support film, and the pressing plate separates the support film into two independent sample preparation areas; after both samples are prepared, a fine sharp object is used to puncture three identification holes in the support film at equal intervals along the circumferential edge of the first sample preparation area of ​​the pressing plate; and two different sample preparation areas are positioned through the three identification holes. The sample preparation method is simple and easy to implement, and can effectively position different sample areas, greatly improving the test efficiency of the transmission electron microscope.

Description

Technical Field

[0001] The invention relates to the technical fields of transmission electron microscopy, sample preparation and the like, and in particular to a method for preparing double samples based on a transmission electron microscope support film. Background Art

[0002] The transmission electron microscope is a precise and valuable instrument for analyzing the morphology, structure and composition of micro- and nano-scale samples. During transmission electron microscopy testing, powder samples are usually prepared on a grid support film, dried and then sent into the electron microscope for testing. Usually only one sample can be prepared on a grid. Since the transmission electron microscope is a high vacuum device, a long vacuum pumping time is required after the sample is sent in. In addition, there is thermal drift in the initial stage after the sample is placed in, and a certain stabilization time is required before testing. Therefore, increasing the number of samples injected at a single time plays an important role in improving the test efficiency of the transmission electron microscope.

[0003] Multi-sample holder is a solution to improve test efficiency. Multiple grid fixing positions are set on the sample holder, and multiple samples can be loaded in one injection. However, the price of multi-sample holder is relatively expensive. In addition, the distance between the objective lens shoes of the transmission electron microscope is limited, and the multi-sample holder can only use the single tilt function. It cannot be used when the sample needs to be double tilted.

[0004] The invention with application number 201910066635.4 discloses a method for loading two samples simultaneously based on a common sample stage of a transmission electron microscope. The prepared sample grid is manually cut in half, and then the halves of the grids of two different samples are spliced ​​for loading. Manual cutting has limited precision and is prone to damage to the grid. In addition, there is a risk of samples falling due to loose clamping.

[0005] The invention with publication number CN113192816A discloses a special type of carrier mesh, which is divided into multiple sample loading areas by setting a partition on the carrier mesh. Although a partition is set on the carrier mesh, its protruding height is small, and there is still a problem of the droplet crossing another sample preparation area when the sample is dripped. In addition, this type of carrier mesh also has a positioning problem, and different sample preparation areas cannot be distinguished during testing. The invention with application number 202110812543.3 discloses a special type of multi-sample carrier mesh. The carrier mesh is prepared with dividing grooves to divide it into multiple sample preparation areas. A matching sample preparation table is used to prepare multiple samples in different areas. Slotting the carrier mesh to separate the samples undoubtedly increases the preparation cost of the carrier mesh. In addition, the slots on the carrier mesh are very narrow and small, which makes it difficult to assemble with the matching sample preparation table, increasing the difficulty of sample preparation. Slotting the carrier mesh will also reduce the strength of the carrier mesh, and the carrier mesh is prone to shaking under the action of electronic heat, affecting the test accuracy.

[0006] Therefore, how to prepare multiple samples on common commercially available grid support films in a simple and low-cost manner and accurately separate each sample area has become a problem that needs to be solved to improve the utilization rate of transmission electron microscopy. Summary of the invention

[0007] In view of the defects and shortcomings of the prior art, the present invention proposes a method for preparing double samples based on a transmission electron microscope support film, which provides a method for preparing double samples on a commercially available grid support film and effectively positioning different sample areas. The grid support film used is a commercially available pure copper grid, a microgrid support film, a carbon support film, etc. with a diameter of 3 mm. The commercially available grid support film is usually used to prepare one sample.

[0008] The specific technical solutions are as follows:

[0009] A method for preparing double samples based on a transmission electron microscope support film, characterized in that: a matching sample preparation table and a grid support film are used to prepare double samples:

[0010] The matching sample preparation platform includes a pressing plate and a base; the bottom of the pressing plate is provided with a cylindrical positioning column, a circular through hole is opened in the middle, and the upper part of the circular through hole is provided with a chamfer to increase the sample dripping area. A partition is arranged in the middle, the bottom of the partition is flush with the bottom of the positioning column and separates the through hole in the middle of the pressing plate to form two equally divided independent areas; the sample preparation base is provided with a groove matching the cylindrical positioning column;

[0011] When using the matching sample preparation table to prepare double samples of the transmission electron microscope grid support film, the grid support film is placed in the base groove with the front side facing upward, and the pressing plate cooperates with the base groove through the positioning column so that the bottom of the pressing plate covers the grid support film, and the pressing plate separates the support film into two independent sample preparation areas; after the two samples are prepared, a small sharp object is used to pierce three identification holes in the support film at equal intervals along the circumferential edge of the first sample preparation area of ​​the pressing plate;

[0012] The three identification holes are used to locate two different sample preparation areas.

[0013] Furthermore, the specific method for positioning two different sample preparation areas through the three marking holes is:

[0014] (1) Fix the grid support film on the electron microscope sample rod and put it into the transmission electron microscope; find the three marked holes in the first sample preparation area in the electron microscope imaging mode, and record the x and y coordinates of the three marked holes, which are (x1, y1), (x2, y2) and (x3, y3) respectively; the triangular area with the three marked holes on the grid as vertices is the observation area of ​​the first sample; and test the first sample in this area;

[0015] (2) After testing the first sample, estimate the range of the second observation area based on the coordinates of the three marking holes in the first observation area. The three marking points in the first observation area approximately fall on a circle. The coordinates of the mirror points of the three marking points can be obtained (x ′ 1, y ′ 1), (x ′ 2, y ′ 2) and (x ′ 3, y ′ 3); Mark the coordinates of the three mirror points in the transmission electron microscope operating software; the triangular area with the three mirror points as vertices is the observation area of ​​the second sample.

[0016] Furthermore, the specific process of estimating the range of the second observation area according to the coordinates of the three marking holes in the first observation area includes:

[0017] Step A1: Let: A=2×(x2-x1);

[0018] B = 2 × (y2-y1);

[0019] C=x2 2 +y2 2 -x1 2 -y1 2 ;

[0020] D = 2 × (x3-x2);

[0021] E = 2 × (y3-y2);

[0022] F=x3 2 +y3 2 -x2 2 -y2 2 ;

[0023] Step A2: Calculate the center coordinates of the circles corresponding to the three marked points:

[0024] x0=(B×FE×C) / (B×DE×A);

[0025] y0=(d×ca×f) / (b×de×a);

[0026] Step A3: Calculate the coordinates of the three marking points relative to the mirror point based on the coordinates of the circle center:

[0027] x ′ 1=2×x0-x1;

[0028] y ′ 1=2×y0-y1;

[0029] x ′ 2=2×x0-x2;

[0030] y ′ 2=2×y0-y2;

[0031] x ′ 3=2×x0-x3;

[0032] y ′ 3=2×y0-y3;

[0033] After calculation, three estimated coordinates are input into the electron microscope control software to locate the second observation area; the triangular area with the three mirror point coordinates as vertices is the observation area of ​​the second sample.

[0034] Furthermore, in the middle through hole of the pressing plate, two equally divided independent areas are formed, numbers are engraved near the first area as identification, and the other area is the second area.

[0035] Furthermore, the diameter of the cylindrical positioning column is 3 mm and the height is 5 mm; the diameter of the circular through hole is 2.5 mm; the width of the partition is 0.25 mm; the diameter of the groove is 3.2 mm and the depth is 5 mm.

[0036] Furthermore, first disperse the two powders to be tested in a certain liquid respectively, then use a pipette to suck 3 μL of the first sample dispersion and drop it into the first area of ​​the support membrane separated by the pressing plate, and wait for the sample to dry naturally or use a drying lamp; then use a pipette to suck 3 μL of the second sample dispersion and drop it into the second area of ​​the support membrane separated by the pressing plate, and wait for the sample to dry naturally or use a drying lamp.

[0037] Furthermore, the shape of the pressing plate and the base body can be circular or square, preferably circular. The pressing plate and the base are made of corrosion-resistant stainless steel.

[0038] The present invention and its preferred embodiment can use conventional commercially available grid support membranes to prepare double samples. The sample preparation method is simple and easy, and different sample areas can be effectively positioned, greatly improving the test efficiency of the transmission electron microscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0040] Figure 1 Schematic diagram of the pressing plate used for preparing double samples in an embodiment of the present invention. Figure 1 (a) is a three-dimensional diagram of the pressure plate. Figure 1 (b) is a cross-sectional view of the pressure plate.

[0041] Figure 2 Schematic diagram of the base used for double sample preparation in an embodiment of the present invention.

[0042] Figure 3It is a schematic cross-sectional view of the sample preparation platform after assembly according to an embodiment of the present invention.

[0043] Figure 4 This is a schematic diagram of marking in the first sample preparation area according to an embodiment of the present invention.

[0044] Figure 5 This is a schematic diagram of determining an observation area through three marking holes in an embodiment of the present invention.

[0045] Figure 6 This is a ceramic powder morphology image observed in the first observation area of ​​an embodiment of the present invention.

[0046] Figure 7 This is a morphology image of a quantum dot sample observed in the second observation area of ​​an embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail with the accompanying drawings as follows:

[0048] Combination Figure 1 and Figure 2 The structure of the sample preparation table is described in detail. Figure 1 (a) is a three-dimensional schematic diagram of the pressure plate. Figure 1 (b) is a schematic cross-sectional view of the pressing plate. In this embodiment, there is a cylindrical positioning post 101 with a diameter of 3 mm and a height of 5 mm at the bottom of the pressing plate. A through hole 102 with a diameter of 2.5 mm is opened in the middle of the pressing plate. The upper part of the circular through hole is chamfered 103 to increase the sample dripping area. A partition 104 with a width of 0.25 mm is arranged in the middle of the through hole 102. The bottom of the partition 104 is flush with the bottom of the positioning post 101. The partition 104 isolates the through hole 102 in the middle of the pressing plate to form two equally divided independent areas 105 and 106. The side of the first area 105 is engraved with a logo 107. Correspondingly, area 106 is the second area. As shown in FIG. Figure 2 As shown, a groove 201 with a diameter of 3.2 mm and a depth of 5 mm is provided on the sample preparation base. The body shape of the pressing plate and the base can be circular or square, preferably circular. The pressing plate and the base are made of corrosion-resistant stainless steel.

[0049] The steps for preparing the double sample of the transmission electron microscope grid support membrane using the sample preparation stage are as follows:

[0050] (1) If Figure 3 As shown, a commercially available grid support film 301 is placed in the base groove 201 with the front side facing upward.

[0051] (2) The pressing plate cooperates with the base groove 201 through the positioning column 101, so that the bottom of the pressing plate covers the grid support film 301, and the pressing plate separates the support film into two independent sample preparation areas 302 and 303.

[0052] (3) Disperse the two powders to be tested in a certain amount of liquid respectively.

[0053] (4) Use a pipette to absorb 3 μL of the first sample dispersion and drop it into the first sample preparation area 302 of the support film 301 separated by the pressing plate, and wait for the sample to dry naturally or use a drying lamp to dry it.

[0054] (5) Use a pipette to take 3 μL of the second sample dispersion and drop it into the second sample preparation area 303 of the support film 301 separated by the pressing plate, and wait for the sample to dry naturally or use a drying lamp to dry it.

[0055] (6) After both samples are prepared, Figure 4 As shown, three fine marking holes 402, 403 and 404 are equidistantly punctured in the first sample preparation area 302 of the support film using a fine sharp object along the circumferential edge 401 of the first sample preparation area of ​​the pressing plate.

[0056] The positioning method of different sample preparation areas of the grid support film after the sample is prepared is as follows:

[0057] (1) Fix the grid support film 301 on the electron microscope sample rod and put it into the transmission electron microscope. Under the electron microscope imaging mode, find the three marked holes in the first sample preparation area and record the x and y coordinates of the three marked holes, which are (x1, y1), (x2, y2) and (x3, y3), respectively. Figure 5 The triangular area with three marked holes as vertices on the grid is the observation area for the first sample. The first sample is tested in this area.

[0058] (2) After testing the first sample, estimate the range of the second observation area based on the coordinates of the three marking holes in the first observation area. The three marking points in the first observation area are approximately on a circle. The coordinates of the mirror points of the three marking points can be obtained (x ′ 1, y ′ 1), (x ′ 2, y ′ 2) and (x ′ 3, y ′ 3) The estimation steps are as follows:

[0059] A1) Let: A=2×(x2-x1);

[0060] B = 2 × (y2-y1);

[0061] C=x2 2 +y2 2 -x1 2 -y1 2 ;

[0062] D = 2 × (x3-x2);

[0063] E = 2 × (y3-y2);

[0064] F=x3 2 +y3 2 -x2 2 -y2 2 ;

[0065] A2) Calculate the coordinates of the center of the circle corresponding to the three marked points:

[0066] x0=(B×FE×C) / (B×DE×A);

[0067] y0=(d×ca×f) / (b×de×a);

[0068] A3) Calculate the coordinates of the three marked points relative to the mirror point based on the coordinates of the circle center:

[0069] x ′ 1=2×x0-x1;

[0070] y ′ 1=2×y0-y1;

[0071] x ′ 2=2×x0-x2;

[0072] y ′ 2=2×y0-y2;

[0073] x ′ 3=2×x0-x3;

[0074] y ′ 3=2×y0-y3;

[0075] The calculation process of the mirror point coordinates can be calculated by software programming or electronic spreadsheet. After calculation, the three estimated coordinates are input into the electron microscope control software to locate the second observation area. The triangular area with the three mirror point coordinates as vertices is the observation area of ​​the second sample. Specific embodiment 1:

[0077] The present invention is described below by simultaneously preparing and observing two samples, ceramic nanopowder and carbon quantum dots, on an ultra-thin carbon film grid. The steps are as follows:

[0078] (1) Place the pressing plate, ultra-thin carbon film grid and base according to Figure 3 Assembled in the shown positions.

[0079] (2) Disperse ceramic nanopowder and carbon quantum dots samples in a certain liquid respectively.

[0080] (3) Use a pipette to take 3 μL of the ceramic nanopowder dispersion and drop it into the first sample preparation area 105 of the pressing plate, and dry it using an infrared drying lamp.

[0081] (4) Use a pipette to take 3 μL of the carbon quantum dot dispersion and drop it into the second sample preparation area 106 of the pressing plate, and use an infrared drying lamp to dry it.

[0082] (5) After both samples are prepared, Figure 4 As shown, three fine marking holes 402, 403 and 404 are equidistantly punctured in the first sample preparation area 302 of the ultra-thin carbon film along the circumferential edge 401 of the first sample preparation area of ​​the pressing plate using a fine sharp object.

[0083] (6) Fix the ultra-thin carbon support film on the electron microscope sample rod and send it into the transmission electron microscope. Find the three marked holes of the ultra-thin carbon film in the electron microscope imaging mode and record the x and y coordinates of the three marked holes, which are (-175.84μm, 844.01μm), (925.35μm, 572.62μm) and (933.10μm, -689.56μm). The triangular area with the three marked holes as vertices on the grid is the observation area of ​​the first sample. The sample morphology observed in this marked area is as follows: Figure 6 shown.

[0084] (7) After observing the samples in the first area, estimate the range of the second observation area based on the coordinates of the three marked holes in the first observation area. Enter the coordinates of the three marked holes in the pre-compiled spreadsheet and calculate the corresponding mirror point coordinates as (545.14μm, -970.09μm), (-556.04μm, -698.70μm) and (-563.79μm, 563.47μm). Use the three estimated coordinates to locate the second observation area in the electron microscope control software. The triangular area with the three mirror point coordinates on the grid as vertices is the observation area of ​​the second sample. The morphology of the carbon quantum observed in this area is as follows: Figure 7 As shown, it can be seen that there is no mutual interference between the two samples, which shows that the method of the present invention can prepare two samples on a grid support film at the same time and effectively position and test them, greatly improving the efficiency of the transmission electron microscope.

[0085] This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of methods for preparing double samples based on transmission electron microscope support membranes under the inspiration of this patent. All equivalent changes and modifications made according to the scope of the patent application of the present invention should be covered by this patent.

Claims

1. A method for preparing double samples based on a transmission electron microscope support film, characterized in that: Use the matching sample preparation table and grid support film for double sample preparation: The matching sample preparation table includes a pressing plate and a base; a cylindrical positioning column is arranged at the bottom of the pressing plate, a circular through hole is opened in the middle, and a chamfer is arranged on the upper part of the circular through hole to increase the sample dripping area; a partition is arranged in the middle, the bottom of the partition is flush with the bottom of the positioning column and the through hole in the middle of the pressing plate is separated to form two equally divided independent areas; a groove matching the cylindrical positioning column is opened on the base; When using the matching sample preparation table to prepare double samples of the transmission electron microscope grid support film, the grid support film is placed in the base groove with the front side facing upward, and the pressing plate cooperates with the base groove through the positioning column so that the bottom of the pressing plate covers the grid support film, and the pressing plate separates the support film into two independent sample preparation areas; after the two samples are prepared, a small sharp object is used to pierce three identification holes in the support film at equal intervals along the circumferential edge of the first sample preparation area of ​​the pressing plate; Positioning two different sample preparation areas is performed through the three identification holes; The specific method for positioning two different sample preparation areas through the three marking holes is: (1) Fix the grid support film on the electron microscope sample rod and put it into the transmission electron microscope; find the three identification holes in the first sample preparation area under the electron microscope imaging mode, and record the x and y coordinates of the three identification holes, which are (x1, y1), (x2, y2) and (x3, y3) respectively; the triangular area with the three identification holes on the grid as vertices is the observation area of ​​the first sample; and test the first sample in this area; (2) After testing the first sample, estimate the range of the second observation area based on the coordinates of the three marking holes in the first observation area; the three marking holes in the first observation area approximately fall on a circle; calculate the coordinates of the radial points of the three marking holes (x ′ 1, y ′ 1), (x ′ 2, y ′ 2) and (x ′ 3, y ′ 3): Mark the coordinates of the three radial points in the transmission electron microscope operating software; the triangular area with the three radial points as vertices is the observation area of ​​the second sample.

2. The method for preparing double samples based on a transmission electron microscope support film according to claim 1, characterized in that: The specific process of estimating the range of the second observation area according to the coordinates of the three identification holes in the first observation area includes: Step A1: Let: A=2×(x2-x1); B = 2 × (y2-y1); C=x2 2 +y2 2 -x1 2 -y1 2 ; D = 2 × (x3-x2); E = 2 × (y3-y2); <h2 style=";text-align:left;direction:ltr">F=x3<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +y3<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -x2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -y2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> ; Step A2: Calculate the center coordinates of the circles corresponding to the three marking holes: x0=(B×FE×C) / (B×DE×A); y0=(D×CA×F) / (B×DE×A); Step A3: Calculate the coordinates of the three marking hole diameter points based on the coordinates of the circle center: x ′ 1=2×x0-x1; yes ′ 1=2×y0-y1; x ′ 2=2×x0-x2; yes ′ 2=2×y0-y2; x ′ 3=2×x0-x3; y ′ 3=2×y0-y3; After calculation, three estimated coordinates are input into the electron microscope control software to locate the second observation area; the triangular area with the three radial point coordinates as vertices is the observation area of ​​the second sample.

3. The method for preparing double samples based on a transmission electron microscope support film according to claim 1, characterized in that: The through hole in the middle of the pressure plate is separated into two equally divided independent areas, a number is engraved near the first area as an identification, and the other area is the second area.

4. The method for preparing double samples based on a transmission electron microscope support film according to claim 1, characterized in that: The diameter of the cylindrical positioning column is 3 mm and the height is 5 mm; the diameter of the circular through hole is 2.5 mm; the width of the partition is 0.25 mm; the diameter of the groove is 3.2 mm and the depth is 5 mm.

5. The method for preparing double samples based on a transmission electron microscope support film according to claim 4, characterized in that: After the support film is separated into two independent sample preparation areas by a pressing plate, the sample preparation process includes the following steps: first, the two powders to be tested are dispersed in a certain liquid respectively, and then 3 μL of the first sample dispersion is sucked by a pipette, and dropped into the first area of ​​the support film separated by the pressing plate, and the sample is waited for natural drying or dried by a drying lamp; then 3 μL of the second sample dispersion is sucked by a pipette, and dropped into the second area of ​​the support film separated by the pressing plate, and the sample is waited for natural drying or dried by a drying lamp.

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