Chapter 120: sample

　　 The five-day National Day holiday passed in a flash.
　　 During this period, the overall framework of Xu Qiu's article has been completed.
　　 In the main text, there are now two more important characterizations, the transmission electron microscope TEM, and the magic light source test GIWAXS.
　　 As for other characterization tests, such as nuclear magnetic resonance spectroscopy and elemental analysis of polymer donor materials, they can only be included in supporting information.
　　 In addition, he received an e-mail that the "Big Men" that was repaired before the holiday has been successfully accepted.
　　 The impact factor of this journal is about 5. Because Xu Qiu and Chen Wanqing are working together, they equally divided the prize money for the article publication, 500 yuan each.
　　 If you get the bonus, you have to invite the fellows in the research group to eat.
　　 The whole group of five people, plus the younger brothers and sisters who came to Cengfan, went out for a meal. According to the standard of 70-100 per capita, there was not much left.
　　 If everyone adds the first cup of milk tea invited by others in the fall, the bonus just earned is basically gone.
The price of 　　Madu is still quite expensive. According to the standard of 70 per capita near the university town, the order is almost half meat and half vegetarian, plus the staple food to barely eat.
　　 If you go to eat hot pot or barbecue, 100 per capita may not be enough.
　　 As for the bonus that was just acquired and then spent, the two of them didn't bother very much.
　　 After all, everyone has a bright future, right?
　　 After graduation, the bonus that I get now may only be my daily salary.
　　……
　　 a few days later.
　　 "Xu Qiu, we will test TEM tomorrow, we need to prepare samples."
　　 "I remember that when I tested the AFM, I just used the battery device to test it," Xu Qiu said:
　　 "Do TEM samples still need special preparation?"
　　 "AFM tests the surface of the film, TEM is transmission, and electrons must penetrate the film to test, so no glass substrate is allowed."
　　 "I understand, it's a separate film to test, right."
　　 "That's right, and the thickness of this film should not be too thick. It needs to be at the micro-nano level, otherwise the electron beam cannot penetrate." Chen Wanqing said:
　　 "But our effective layer is only 100 nanometers, so there is no need to worry about the thickness of the film."
　　How to prepare TEM samples?
　　 Xu Qiu did not rush to check the system images or ask for help from the school sister, but to analyze independently:
　　 Before doing synthesis in Zhangjiang, the polymer material was dissolved in chloroform or toluene, and then dropped into the methanol solvent, but it could form a polymer film.
　　 However, the thickness should be in the millimeter level, which is obviously not desirable.
　　 There is still a high probability that spin coating is used to obtain nano-level thin films.
　　 only spin coating must use the substrate, so the question is converted to "how to separate the film and the substrate".
　　 Heating?
　　 Poke with tweezers?
　　 Soak with water?
　　 Ultrasound?
　　 Xu Qiu racked his brains and thought for a long time, but still couldn't think of any way to separate without damage.
　　 Don’t reinvent the wheel, just see what other people’s wheels look like.
　　 Start the system image.
　　 This method is good, but it is still possible.
　　 However, such a clever method, 80% did not come up with the senior sister herself.
　　 said that 80% of her should be overestimated.
　　 Be strict, ninety-nine percent?
　　 "What do you think?" Chen Wanqing shook her hand before his eyes and said:
　　 "Come with me to the receiving office. The copper mesh is needed to test the TEM, which is used to place the sample film."
　　……
　　 After using up, return to the laboratory.
　　 A box of copper mesh is 250 yuan, 50 pieces, and an average of 5 yuan.
　　 Xu Qiu picked up a copper mesh with tweezers to check.
　　The round copper mesh is about 4mm in diameter. It is very small and thin. It will bend with a little force.
　　 Chen Wanqing began to introduce the operation, which is basically the same as in the system image.
　　 First spin-coat a thick layer of PEDOT on a clean glass sheet, and then spin-coat an effective layer.
　　PEDOT should be coated thicker than usual when fabricating devices.
　　 Then the glass piece was immersed in water.
　　PEDOT is water-soluble, so it will dissolve when soaked in water.
　　 The upper effective layer is insoluble in water. When the middle layer PEDOT is dissolved in water, the effective layer film will be separated from the underlying substrate.
　　 Because the density of the film is less than the density of water, it will float on the water.
　　Most of the films will curl up together, and a small part of them can stretch out and float on the water.
　　 Finally, collect the stretched film with a copper mesh dedicated for TEM to obtain a single-layer film sample.
　　 "Senior sister, is this the method you came up with?"
　　 "Of course...no, I learned this from the TEM test teacher."
　　 As expected.
　　……
　　 Han Jiaying didn't come today, and Xu Qiu had no brother to help, so he could only do it himself.
　　 Spin-coating PEDOT at low speed first, and then spin-coating the effective layer normally.
　　 Chen Wanqing took out a few disposable PE cups, cut the cups around the waist, leaving a shallow bottom, and then added half the volume of deionized water to each cup.
　　Because TEM tests the morphology of the donor/acceptor blend film, there is no need to test a sample of a separate polymer film, so the number of samples is small, only eight samples.
　　 In order to prevent accidents, one more backup is required for each type, so a total of sixteen samples must be prepared.
　　 For equipment like TEM, the test cost is still relatively expensive, some are based on the test duration, and some are based on the number of samples.
　　The chemistry department is based on the calculation of the sample test time.
　　 The internal test price in the school is relatively low~EbookFREE.me~ If the test is carried out in a special test center outside, it may cost several thousand yuan for three or four samples.
　　 Therefore, the general instructor will allow students to test TEM only when they are sure that they can produce results, or when other tests are necessary.
　　 Unless it's a research group that has a lot of research funding and can't finish it, then it's another matter.
　　……
　　 Xu Qiu put the glass substrates face up, carefully put them into the PE cup, and then mark them with a marker on the outside of the PE cup.
　　 After the substrate was in the water, it changed quickly.
　　 The corners of the film first encountered water and rolled up.
　　 After a minute, most of the film has been separated from the substrate and floated on the water.
　　 But the largest piece of film, curled up together.
　　 Xu Qiu used pointed tweezers to stir the curled film.
　　If you can flatten the film, then everyone will be happy.
　　 It doesn’t matter if you can’t pick the level.
　　Because film fragments are generated during the stirring process, if the fragments are flat, they can also be collected.
　　The area of ​​the entire film is more than 5 square centimeters, and Xu Qiu only needs to take one percent of it.
　　 Of course, in theory.
　　In actual operation, various accidents will inevitably occur.
　　 For example, the film is not flat no matter how it is picked, the copper mesh of the sample is not clamped off, and the sample is collected and found that it is not a layer of film.
　　Intermittently, Xu Qiu and Chen Wanqing spent three to four hours in total to complete all the samples.
　　 Finally, the two collected the copper mesh with the sample in a disposable centrifuge tube.
　　 Keep the lid of the centrifuge tube open and leave it overnight to completely volatilize the water on the copper net before it can be used for testing.