A highly efficient method for preparing ultra-large liquid tank pools

Abstract

The application discloses a kind of efficient super large liquid tank pool preparation method, with dimethyl carbonate (DMC) as solvent preparation concentration 15%-20% (w / v, g / mL) polyvinyl acetate (PVAC) solution as shell precursor liquid, with water as solvent preparation 10 vol%-70 vol% glycerol solution as core precursor liquid, by coaxial electrospinning technology, with carbon support membrane direct receiving spinning fiber, to obtain by PVAC wrapping water's fibrous liquid tank pool that can be directly used for electron microscope test.This method can prepare about 9000 liquid tank pools in 30s, greatly improve the preparation efficiency of liquid tank pool, the raw materials used in the whole process are cheap and easy to obtain, which greatly saves the cost;At the same time, a large number of liquid tank pools prepared are on the same support film or substrate, so a large number of samples can be observed under the same external conditions to observe the behavior of a large number of samples in real liquid environment, so it can be used for statistical research.

Description

Technical Field

[0001] This invention belongs to the field of electron microscope testing technology, and specifically relates to a liquid tank that can be directly used for electron microscope testing. Background Technology

[0002] Electron microscopy enables real-time, atomic-level observation of the structure and evolution dynamics of materials and biological samples. Because electron microscopes require a vacuum environment, the samples typically used for characterization are solid. However, many real-world applications occur in liquid environments, such as electrochemical processes, catalysis, self-assembly in materials systems, and various physiological processes in biological systems. To observe the behavior of samples in liquids using electron microscopy, liquid baths are employed. A liquid bath typically consists of two thin sheets, with the liquid sample injected between them and sealed. The challenges in fabricating a liquid bath lie in: 1) the imaging window must be thin enough to allow the electron beam to pass through; and 2) the material of this thin imaging window must possess sufficient strength to withstand the pressure difference caused by the high vacuum. In the decades since the invention of the electron microscope, researchers have progressed from initially attempting to seal liquids using sandwich-shaped thin aluminum foil to now using silicon nitride / silicon and graphene to create liquid baths.

[0003] Key developments in recent years can be summarized as follows: In 2003, William et al. first reported the use of silicon nitride / silicon as a liquid bath window. Its high strength ensured stability under high vacuum, while its lower atomic number improved spatial resolution in a liquid environment. In 2009, Zheng et al. fabricated an independent liquid bath using thinner silicon nitride films, achieving a resolution of 1 nm. In the same year, De Jonge et al. added microtubes and a syringe pump to the silicon nitride liquid bath to allow for liquid circulation, successfully observing the state of a large number of samples within the bath. In 2012, Yuk et al. created a liquid bath by encapsulating liquid in a double-layer graphene layer to observe platinum growth; its excellent resolution was attributed to the ultrathin graphene material. In addition, there are also some graphene-derived liquid baths, such as those directly deposited on amorphous carbon films.

[0004] While advancements in liquid bath cell technology, such as improved resolution, have been made, the preparation methods for these cells are generally cumbersome, time-consuming, labor-intensive, and costly, limiting their application. This is especially true when large numbers of liquid bath samples are needed for statistical studies, making these methods inadequate. Therefore, a simplified liquid bath cell preparation method is urgently needed to enable statistical analysis of samples in a liquid environment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention will develop a novel liquid bath preparation technology based on coaxial electrospinning technology, aiming to achieve efficient, high-volume preparation, low cost, and ready-to-use technology.

[0006] The method for preparing the liquid tank of the present invention is as follows:

[0007] (1) Raw materials: polyvinyl acetate (170000 g / mol, Macklin), dimethyl carbonate (99%, Adamas), glycerol (≥99% Greagent), ultrapure water.

[0008] (2) Production process flow chart as follows Figure 4 As shown;

[0009] (3) Production process:

[0010] 1. The electrospinning process is employed to prepare the core and shell precursor solutions. Before spinning, separate precursor solutions are required. A 15%-20% (w / v, g / mL) polyvinyl acetate (PVAC) solution is prepared using dimethyl carbonate (DMC) as the solvent to serve as the shell precursor solution. A 10 vol%-70 vol% glycerol solution is prepared using water as the solvent to serve as the core precursor solution (for preparing electrospinning samples containing nanoparticles, simply incorporate the corresponding nanoparticles into the core precursor solution). After preparing the core and shell precursor solutions, these solutions are transferred to the corresponding syringes of the electrospinning machine for subsequent spinning processes.

[0011] 2. Place the core-shell syringe on a micropump with precisely controllable flow rate, maintaining a temperature of 30-40℃ and a relative humidity of 30-40% under standard pressure. Use coaxial electrospinning technology to form Taylor cones between the core and shell solutions, producing the final core-shell nanofibers. The voltage during spinning is 10-20 kV, and the distance from the coaxial needle tip to the receiver is 10-20 cm.

[0012] 3. A carbon support membrane is used to directly receive the spun fibers, resulting in a fibrous liquid tank containing water encapsulated by PVAC. Liquid tanks prepared using this method can be directly used for electron microscopy testing.

[0013] The technical solution of the present invention has the following advantages:

[0014] 1. This invention can prepare approximately 9,000 liquid tanks within 30 seconds, greatly improving the preparation efficiency of liquid tanks;

[0015] 2. The raw materials used in the entire process are inexpensive and readily available, which greatly reduces costs;

[0016] 3. Since a large number of liquid tanks are prepared on the same supporting membrane, the behavior of a large number of samples in the liquid tanks can be observed under the same conditions, which can be conveniently used for statistical research. Attached image description:

[0017] Figure 1 These are transmission electron microscopy images of the liquid tank prepared by this invention under different conditions;

[0018] Figure 2 This is a schematic diagram of in-situ observation of bubble changes in the liquid tank of the present invention;

[0019] Figure 3 This is a schematic diagram showing the changes in the liquid tank of the present invention when it contains nanoparticles;

[0020] Figure 4 This is a flowchart of the production process of this invention. Detailed Implementation

[0021] 1. Disperse 4 g of PVAC in 20 mL of DMC to prepare a 20% (w / v) dispersion as the shell solution; dissolve 1 mL of glycerol in 9 mL of ultrapure water to prepare a 10 vol% solution as the core solution;

[0022] 2. Turn on the heater and dehumidifier, and set the temperature and relative humidity to 35℃ and 35%, respectively. Take a 20 nm thick carbon support film and attach its edge to the roller receiver. Adjust the distance from the coaxial needle tip to the receiver to 15 cm;

[0023] 3. Using two 10 mL syringes, respectively, draw sufficient amounts of the nucleus solution and shell solution and place them on a micro-pump. Connect the syringes to the nucleus / shell inlet of the coaxial needle. First, advance the nucleus / shell solution forward at a faster speed to reach the needle inlet, then wipe away any overflowing solution.

[0024] 4. The preset core solution feeding rate is 1.12 mL / h, the shell solution feeding rate is 4.38 mL / h, the spinning voltage is 15 kV, and the roller rotation speed is 60 r / min. The micro-pump and voltage are turned on sequentially. During the electrostatic spinning process, the liquid forms a Taylor cone at the needle tip, thus forming a jet. The shell solution solvent will rapidly evaporate to form a polymer shell, while the core solution will be retained within the fibrous shell, forming a liquid tank.

[0025] 5. After spraying for 30 seconds, turn off the voltage, micro-pump, and roller in sequence, and remove the carbon support film for electron microscopy testing.

[0026] To confirm the effectiveness of the liquid bath, we characterized it using a transmission electron microscope (TEM, TALOS F200X). Using the electron beam in the TEM as the excitation source, we can observe the dynamic behavior of the sample in the liquid bath after excitation in real time using a charge-coupled device (CCD) camera. Several typical applications are illustrated below. Figure 1 Typical liquid tank cells in transmission electron microscopy. (a) Image of multiple liquid tank cells. (b) Magnified image of a single liquid tank cell. (c) Schematic diagram of the structure of a liquid tank cell. (d) The preparation of multiple liquid tank cells on the same substrate enables simultaneous observation of the evolution of multiple sample systems (such as bubbles). Three bubbles under electron beam excitation are demonstrated here. These bubbles contract at different rates, with the rate of change in the order of bubble 1 > bubble 3 > bubble 2. The length of each bubble is measured in nanometers.

[0027] Figure 1 Image a shows a typical multi-channel liquid bath image, revealing several linear fibers, with the liquid bath located within protruding beads (marked with solid arrows). Further magnification of the liquid bath image allows observation of internal air bubbles, such as... Figure 1 b (The dark areas marked by solid arrows represent liquid, and the bright areas marked by dashed arrows represent bubbles). Based on the bubble shape, it can be determined that the prepared liquid tank is tubular. Figure 1 Figure c shows a schematic diagram of the liquid tank, which is a tubular liquid channel encased in a PVAC polymer shell.

[0028] Compared with existing liquid bath preparation methods in the literature, this method can efficiently prepare a large number of liquid baths on the same substrate, with approximately 9000 liquid baths on a single 3 mm diameter carbon support film (spinning time 30 s). This also allows the dynamic process of samples in multiple liquid baths to be observed simultaneously under the same external conditions, such as... Figure 1 As shown in Figure d, in the initial state (0 s), each of the three independent liquid baths contains one bubble with lengths of 1950, 1325, and 2700 nm, respectively. After 8 seconds of electron beam irradiation, the bubble sizes changed; bubbles 2 and 3 contracted in length by approximately 6% and 66%, respectively, while bubble 1 contracted and disappeared. After 16 seconds of electron beam irradiation, bubble 2 remained, while bubble 3 contracted again and disappeared. This means that these bubbles of different sizes change at different rates when resisting electron beam irradiation, confirming that this method can be used to statistically study the kinetic behavior of a large number of liquid bath samples under the same external conditions.

[0029] We further investigated different bubble dynamic behaviors in situ, including bubble growth, bubble contraction, bubble stabilization, and bubble fusion. Figure 2A series of electron microscopy snapshots show the evolution of bubbles over time. (a) Under electron beam excitation, bubbles larger than the critical size tend to grow. (b) Bubbles smaller than the critical size tend to shrink. (c) Bubbles of appropriate size (reaching a stable critical size) can remain stable. (d) When multiple bubbles coexist, they merge into a single bubble, which then gradually shrinks until it eventually disappears. The length of each bubble at different times is in nanometers.

[0030] For example: Regarding bubble growth ( Figure 2 a) Bubbles with an initial length of 1466 nm gradually grew after electron beam irradiation, increasing in length to 2857 nm (nearly double) after 6 seconds of irradiation. On the other hand, a certain number of bubbles experienced a decrease in length, such as... Figure 2 The 2421 nm long bubble in b gradually shrinks during excitation and eventually disappears after 10 s. However, at an appropriate size (the critical size for stability), the original bubble is stable during irradiation. Figure 2 c). Furthermore, if multiple air bubbles exist simultaneously in the same liquid tank ( Figure 2 d), they will merge into a single bubble after irradiation (3 s), then shrink until they finally disappear (12 s).

[0031] The above demonstration illustrates one application of the prepared liquid tank: studying various dynamic behaviors of bubbles. Simultaneously, the driving force generated by bubble evolution will propel various movements of nanoparticles in the liquid, showing potential applications in autonomous nanomotors and drug delivery. For the large bubbles here, we selected two typical systems of similar size: single gold nanoparticles (symmetric morphology; ~50 nm); Figure 3 a and 3c) and gold aggregates (asymmetric morphology; ~70nm; Figure 3 b and 3d) demonstrate the effect of morphological asymmetry on the motion of nanostructured samples. Figure 3 (a, b) are snapshots of the motion of gold nanoparticles and aggregates taken under a transmission electron microscope, from which the motion trajectories of the particles and aggregates can be obtained and their diffusion behavior can be analyzed. Figure 3 (c, d) are transmission electron microscopy images of single gold nanoparticles and gold aggregates in a liquid bath, and magnified images within the corresponding red dashed boxes. Gold particles of ~10 nm can be clearly distinguished.

[0032] The movement of these gold nanostructure samples in the liquid is caused by the contraction of air bubbles due to electron beam irradiation, leading to liquid flow. Therefore, this product allows for real-time observation of the movement of nanostructures in liquids.

[0033] In summary, this method is suitable for efficiently preparing large numbers of liquid tanks for statistical observation. Compared to silicon nitride or graphene films, which can cost hundreds or thousands of yuan per piece, this method significantly reduces material costs. Furthermore, this method can produce approximately 9000 liquid tanks within 30 seconds, greatly saving time.

Claims

1. A method for preparing a high-efficiency, ultra-large volume liquid tank for real-time observation in electron microscopy, characterized in that, The method includes: using a 15%-20% w / v polyvinyl acetate solution as the shell precursor solution, and using water as the solvent to prepare a 10 vol%-70 vol% glycerol solution as the core precursor solution; after the core and shell precursor solutions are prepared, they are spun on a support membrane using electrospinning technology; the electrospinning step is carried out using an electrospinning machine. After the core and shell precursor solutions are prepared, they are transferred to corresponding syringes of a coaxial electrospinning machine, and the temperature is maintained at 30-40℃ and the relative humidity at 30-40% under standard pressure. The core and shell precursor solutions are then used to form Taylor cones and produce the final core-shell nanofibers through the coaxial electrospinning machine. The voltage during spinning is 10-20 kV, the distance from the tip of the coaxial needle to the receiver is 10-20 cm, and the spun fibers are directly received using a carbon support membrane, thereby obtaining a fibrous liquid tank containing water encapsulated by polyvinyl acetate; the shell precursor solution uses dimethyl carbonate as the solvent.

2. The method for preparing an ultra-large volume liquid tank according to claim 1, characterized in that, The method for preparing liquid bath samples containing nanoparticles is as follows: corresponding nanoparticles are incorporated into the nuclear precursor solution.

Images